In an amplification apparatus according to the present disclosure, a combining unit combines an output signal of a first amplifier provided at a first branch with an output signal of a second amplifier provided at a second branch and outputs the combined signal. A non-linearity compensation unit multiplies an input baseband signal by a non-linearity compensation coefficient for compensating non-linearity of the entire apparatus, a first deviation compensation unit multiplies a first branch signal by a first deviation compensation coefficient for compensating an inter-branch deviation, and a second deviation compensation unit multiplies a second branch signal by a second deviation compensation coefficient for compensating the inter-branch deviation. A compensation coefficient calculation unit calculates the non-linearity compensation coefficient, the first deviation compensation coefficient, and the second deviation compensation coefficient based on the input baseband signal and a feedback baseband signal obtained by feeding back the combined signal.

In related art, an outphasing type amplification apparatus (hereinafter referred to as an outphasing amplification apparatus) has been proposed as a high efficiency amplification apparatus that operates an amplifier in an output saturation region (see, for example, Non Patent Literature 1).
The outphasing amplification apparatus is a linear amplification apparatus using a constant amplitude amplifier such as a saturation amplifier like an amplification apparatus of LINC (Linear Amplification with Nonlinear Components) type. However, the LINC type amplification apparatus uses, for example, a hybrid or 3 dB coupler which causes a loss of 3 dB at the time of combining signals as a combining unit that combines output signals of the two amplifiers. On the other hand, the outphasing amplification apparatus uses a Chireix Combiner that combines output signals of two amplifiers without isolation. Thus, the outphasing amplification apparatus can reduce the loss at the time of combining signals, thereby reducing the linearity and instead improving the efficiency.
In the outphasing amplification apparatus according to the related art, input impedances of respective input ports of the Chireix combiner viewed from the two amplifiers are asymmetrical. This leads to a problem that a dynamic range of an amplitude (output power) of an outphasing combined signal, which is an output signal of the Chireix combiner, becomes narrow. This is because of an amplitude imbalance of output signals of the respective amplifiers caused by the above asymmetric input impedance, which reduces an amount of cancellation of the amplitude of the outphasing combined signal when a phase difference of input signals to the Chireix combiner from the two amplifiers is increased to control the amplitude of the outphasing combined signal to be small in an outphasing control operation.
FIG. 12 is a block diagram showing an example of a configuration of the outphasing amplification apparatus according to the related art. The example of FIG. 12 is described in FIG. 1 of Patent Literature 1 and FIG. 9 of Non Patent Literature 2.
As shown in FIG. 12, the outphasing amplification apparatus according to the related art includes a signal separation unit 2, a DAC+Filter (digital-to-analog converter and filter) 3a, a quadrature modulator 4a, a frequency converter 5a, and a first amplifier 6a (amplifier A). The outphasing amplification apparatus according to the related art further includes a DAC+Filter (digital-to-analog converter and filter) 3b, a quadrature modulator 4b, a frequency converter 5b, and a second amplifier 6b (amplifier B). Furthermore, the outphasing amplification apparatus according to the related art includes a combining unit 7, a frequency converter 8, a quadrature demodulator 9, a Filter+ADC (filter and analog-to-digital converter) 10, a non-linearity compensation unit 1, and a compensation coefficient calculation unit 11.
The non-linearity compensation unit 1 performs non-linearity compensation processing on an input baseband signal Sin(t) input to the outphasing amplification apparatus, and outputs, to the signal separation unit 2, the signal subjected to the non-linearity compensation processing as Spd(t). The non-linearity compensation processing is processing for previously multiplying the input baseband signal Sin(t) that is not yet amplified by the outphasing amplification apparatus by a non-linearity compensation coefficient. The non-linearity compensation coefficient will be described later.
The signal separation unit 2 performs phase modulation on the output signal Spd(t) of the non-linearity compensation unit 1 according to an amplitude of Spd(t), separates it into SC1(t) and SC2(t), which are phase modulated pair signals of a constant amplitude, and outputs SC1(t) to the DAC+Filter 3a and SC2(t) to the DAC+Filter 3b. The DAC+Filter 3a converts one of the phase modulated pair signals, which is SC1(t), from a digital signal into an analog signal, and outputs the converted signal to the quadrature modulator 4a. The DAC+Filter 3b converts the other one of the phase modulated pair signals, which is SC2(t), from a digital signal to an analog signal, and outputs the converted signal to the quadrature modulator 4b.
The quadrature modulator 4a quadrature-modulates an in-phase (I-phase) signal and a quadrature (Q-phase) signal, which are output signals of the DAC+Filter 3a, and outputs the quadrature-modulated signals to the frequency converter 5a. The quadrature modulator 4b quadrature-modulates an in-phase (I-phase) signal and a quadrature (Q-phase) signal, which are output signals of the DAC+filter 3b, and outputs the quadrature-modulated signals to the frequency converter 5b.
The frequency converter 5a uses a local oscillation signal (not shown) to convert the output signal of the quadrature modulator 4a from a signal of a baseband frequency or an Intermediate Frequency (IF) into a Radio Frequency (RF) signal and outputs the converted signal to the first amplifier 6a. The frequency converter 5b uses a local oscillation signal (not shown) to convert the output signal of the quadrature modulator 4b from a signal of a baseband frequency or an intermediate frequency into a radio frequency signal and outputs the converted signal to the second amplifier 6b.
When the quadrature modulator 4a and the quadrature modulator 4b have a function capable of directly converting an input in-phase (I-phase) signal and a quadrature (Q-phase) signal into radio frequency signals, the frequency converter 5a and the frequency converter 5b become unnecessary.
The first amplifier 6a amplifies the power of the output signal of the frequency converter 5a, and outputs the signal with amplified power to the combining unit 7 as S1(t). The second amplifier 6b amplifies the power of the output signal of the frequency converter 5b, and outputs the signal with amplified power to the combining unit 7 as S2(t).
The combining unit 7 is a Chireix combiner that combines the output signal of the first amplifier 6a with the output signal of the second amplifier 6b and outputs the combined signal as an outphasing combined signal Sout(t). This outphasing combined signal Sout(t) is output from the outphasing amplification apparatus and transmitted from an antenna or the like (not shown).
The frequency converter 8 uses a local oscillation signal (not shown) to convert the outphasing combined signal Sout(t), which is the output signal of the combining unit 7, from the radio frequency signal into the signal of the baseband frequency or the intermediate frequency and outputs the converted signal to the quadrature demodulator 9. The quadrature demodulator 9 demodulates the output signal of the frequency converter 8 into an in-phase (I-phase) signal and a quadrature (Q-phase) signal, and outputs the demodulated signal to the Filter+ADC 10. The Filter+ADC 10 converts the output signal of the quadrature demodulator 9 from an analog signal into a digital signal, and outputs the converted signal to the compensation coefficient calculation unit 11 as a feedback baseband signal Sfb(t).
When the quadrature demodulator 9 has a function capable of directly converting an input radio frequency signal into an in-phase (I-phase) signal and a quadrature (Q-phase) signal, the frequency converter 8 becomes unnecessary.
The compensation coefficient calculation unit 11 compares the input baseband signal Sin(t) with the feedback baseband signal Sfb(t), calculates the non-linearity compensation coefficient for compensating the non-linearity, as an entire apparatus, of the outphasing combined signal Sout(t), which is the output signal of the combining unit 7, and outputs the calculated non-linearity compensation coefficient to the non-linearity compensation unit 1.
In the above non-linearity compensation processing, the non-linearity compensation unit 1 multiplies the input baseband modulated signal Sin(t) by the non-linearity compensation coefficient calculated by the compensation coefficient calculation unit 11.
Next, the outphasing control operation will be described.
In this example, it is assumed that the non-linearity compensation unit 1 in FIG. 12 is not operated in order to simplify the description of the outphasing control operation.
Since the output signal Spd(t) of the non-linearity compensation unit 1 is the same as Sin(t) when the non-linearity compensation unit 1 is not operated, the input signal of the signal separation unit 2 is represented by Sin(t) in the following formula (1).[Formula 1]Sin(t)=|Sin(t)|·(cos θ(t)+j sin θ(t)).  (1)
In Formula (1), |Sin(t)| is an amplitude modulation component of Sin(t), and θ(t) is a phase modulation component of Sin(t).
In the outphasing control using the Chireix combiner (combining unit 7), the phase modulation angle φm(t) according to the amplitude of the input baseband signal Sin(t) can be expressed, for example, by Formula (2).
                    [                  Formula                                                              2                ]                                                                                ϕ            m                                          (            t            )                          =                                                            sin                                  -                  1                                                                          [                                                                                                                        S                        in                                                                                (                        t                        )                                                                                                                                                                                          S                        in                                                                                    pk                                                  ]                                                                                0                    ≤                                    ϕ              m                                                  (              t              )                                ≤                                    π              2                                                  [              radian              ]                                                          (        2        )
In Formula (2), |Sin|pk is a maximum value of |Sin(t)|. A value of |Sin|pk is determined by a relationship between a Peak to Average Power Ratio (PAPR) of the input baseband signal Sin(t) and a saturation output level of the amplifiers 6a and 6b and then set.
The relationship between the input baseband signal Sin(t) and the phase modulated pair signals SC1(t) and SC2(t) in the outphasing control using the Chireix combiner (combining unit 7) is expressed by Formula (3).[Formula 3]Sin(t)=SC1(t)−SC2(t)  (3)
From Formulas (1), (2), and (3), the phase modulated pair signals SC1(t) and SC2(t) of the constant amplitude can be expressed by the following Formulas (4) and (5).
                    [                  Formula                                                              4                ]                                                                                S                                      C                                                                                1                                                                                (                  t                  )                                            =                                                                                                                              S                        in                                                                                    pk                                    2                                ·                                  [                                                            cos                                                                                θ                                                                                (                        t                        )                                                              +                                          j                                                                                sin                                                                                θ                                                                          (                          t                          )                                                                                ]                                ·                                  [                                                            sin                                                                    (                                                                              ϕ                            m                                                                                (                            t                            )                                                                          )                                                              -                                          j                                                                                cos                                                                          (                                                                                ϕ                              m                                                                                (                              t                              )                                                                                )                                                                                ]                                                                                =                                                                                                                              S                        in                                                                                    pk                                    2                                ·                                  [                                                            cos                                                                                θ                                                                                (                        t                        )                                                              +                                          j                                                                                sin                                                                                θ                                                                          (                          t                          )                                                                                ]                                ·                                                                                [                                                      cos                                                              (                                                                        π                          2                                                -                                                                              ϕ                            m                                                                                (                            t                            )                                                                                )                                                        -                                      j                                                                                sin                                                                    (                                                                              π                            2                                                    -                                                                                ϕ                              m                                                                                (                              t                              )                                                                                )                                                                                ]                                                                                =                                                                                                                              S                        in                                                                                    pk                                    2                                ·                                  [                                                            cos                      (                                                                                θ                                                                                (                            t                            )                                                                          -                                                  (                                                                                π                              2                                                        -                                                                                ϕ                                m                                                                                (                                t                                )                                                                                )                                                                    )                                        +                                                                                j                                                                                sin                  (                                                                                θ                                                                                (                        t                        )                                                              -                                          (                                                                        π                          2                                                -                                                                              ϕ                            m                                                                                (                            t                            )                                                                                )                                                        )                                            ]                                                          (        4        )                                [                  Formula                                                              5                ]                                                                                S                                      C                                                                                2                                                                                (                  t                  )                                            =                                                                                                                              S                        in                                                                                    pk                                    2                                ·                                  [                                                            cos                                                                                θ                                                                                (                        t                        )                                                              +                                          j                                                                                sin                                                                                θ                                                                          (                          t                          )                                                                                ]                                ·                                                                                [                                                      -                                          sin                                                                    (                                                                              ϕ                            m                                                                                (                            t                            )                                                                          )                                                                              -                                      j                                                                                cos                                                                    (                                                                              ϕ                            m                                                                                (                            t                            )                                                                          )                                                                                ]                                                                                =                                                                                                                              S                        in                                                                                    pk                                    2                                ·                                  [                                                            cos                                                                                θ                                                                                (                        t                        )                                                              +                                          j                                                                                sin                                                                                θ                                                                          (                          t                          )                                                                                ]                                ·                                                                                [                                                      cos                                                              (                                                                        π                          2                                                +                                                                              ϕ                            m                                                                                (                            t                            )                                                                                )                                                        -                                      j                                                                                sin                                                                    (                                                                              π                            2                                                    +                                                                                ϕ                              m                                                                                (                              t                              )                                                                                )                                                                                ]                                                                                =                                                                                                                              S                        in                                                                                    pk                                    2                                ·                                  [                                                            cos                      (                                                                                θ                                                                                (                            t                            )                                                                          -                                                  (                                                                                π                              2                                                        +                                                                                ϕ                                m                                                                                (                                t                                )                                                                                )                                                                    )                                        +                                                                                j                                                                                sin                                                  (                                                                                θ                                                                                (                        t                        )                                                              -                                          (                                                                        π                          2                                                +                                                                              ϕ                            m                                                                                (                            t                            )                                                                                )                                                        )                                            ]                                                          (        5        )
FIG. 13 shows the relationship between the input baseband signal Sin(t) and the phase modulated pair signals SC1(t) and SC2(t) (and −SC2(t)) in the outphasing control using the Chireix combiner (combining unit 7). In FIG. 13, a baseband phase θ(t) of the input baseband signal Sin(t) is used as a reference (replaced with zero) to simplify the drawing. Note that, although the signals that are actually phase-modulated by the signal separation unit 2 are SC1(t) and SC2(t), the phase of SC2(t) is inverted finally in the case of using the Chireix combiner (combining unit 7). Thus, −SC2(t) is also shown in FIG. 13 to help understanding the drawing.
In this manner, as shown in Formulas (1) to (5) and in FIG. 13, the signal separation unit 2 generates the phase modulated pair signals SC1(t) and −SC2(t) of the constant amplitude provided with phase modulation control of ±φm(t) in such a way that the phases of SC1(t) and −SC2(t) become ±|π/2−φm(t)| with respect to the phase of the input baseband signal Sin(t) according to the amplitude of the input baseband signal Sin(t), i.e., in such a way that a phase difference of 2×|π/2−φm(t)| is generated between the signals SC1(t) and −SC2(t).
One of the above phase modulated pair signals of the constant amplitude generated by the signal separation unit 2, which is SC1(t), is converted into a radio frequency signal and amplified by the DAC+Filter 3a, the quadrature modulator 4a, the frequency converter 5a, and the first amplifier 6a, and then input to one of the input ports of the combining unit 7 as the signal S1(t). The other one of the above phase modulated pair signals, which is SC2(t), is converted into a radio frequency signal and amplified by the DAC+Filter 3b, the quadrature modulator 4b, the frequency converter 5b, and the second amplifier 6b, and then input to the other one of the input ports of the combining unit 7 as the signal S2(t). When the radio frequency is represented by fC, and ωC=2πfC holds, the signals S1(t) and S2(t) at the respective input ports of the combining unit 7 correspond to the ones in the above Formulas (4) and (5) where θ(t) is replaced by [ωC(t)+θ(t)], and the gains of the amplifiers 6a and 6b are multiplied by G.
Further, as described in Non Patent Literature 1, as for the signals S1(t) and S2(t) at the respective input ports of the combining unit 7, when the Chireix combiner is used as the combining unit 7, the phase of S2(t) is inverted (−SC2(t)) and combined with S1(t). Thus, the outphasing combined signal Sout(t), which is the output signal of the combining unit 7, can be expressed by Formula (6).
                    [                  Formula                                                              6                ]                                                                                S                  out                                                                  (                  t                  )                                            =                                                                                S                    1                                                                          (                    t                    )                                                  +                                  (                                      -                                                                  S                        2                                                                                (                        t                        )                                                                              )                                                                                =                                                                                                                              S                        in                                                                                    pk                                    2                                ·                                  [                                                            cos                                                                    (                                                                                ω                              c                                                                                (                              t                              )                                                                                +                                                      θ                                                                                (                              t                              )                                                                                )                                                              +                                          j                                                                                sin                                                                          (                                                                                ω                                c                                                                                (                                t                                )                                                                                +                                                          θ                                                                                (                                t                                )                                                                                )                                                                                ]                                ·                                                                                [                                  2                  ·                                      sin                                                              (                                                                        ϕ                          m                                                                                (                          t                          )                                                                    )                                                                      ]                                                                                =                                                          G                ·                                                                                                S                      in                                                                            pk                                ·                                  [                                                            cos                                                                    (                                                                                ω                              c                                                                                (                              t                              )                                                                                +                                                      θ                                                                                (                              t                              )                                                                                )                                                              +                                          j                                                                                sin                                                                          (                                                                                ω                                c                                                                                (                                t                                )                                                                                +                                                          θ                                                                                (                                t                                )                                                                                )                                                                                ]                                ·                                                                                sin                                                  (                                                            ϕ                      m                                                                                (                      t                      )                                                        )                                                                                (        6        )
Note that a fixed phase (phase which does not change over time) generated in the course of the frequency conversion or by the phase shift is omitted here.
Furthermore, from Formula (2), the following formula holds.
      sin                                        ϕ        m                          (        t        )              =                                    S          in                                  (          t          )                                                            S          in                            pk      Thus, the output signal of the combining unit 7, i.e., the outphasing combined signal Sout(t), which is the output signal of the outphasing amplification apparatus, is as shown in Formula (7).
                    [                  Formula                                                              7                ]                                                                                S                  out                                                                  (                  t                  )                                            =                                                                                S                    1                                                                          (                    t                    )                                                  +                                  (                                      -                                                                  S                        2                                                                                (                        t                        )                                                                              )                                                                                =                                                          G                ·                                                                                                S                      in                                                                            pk                                ·                                  [                                                            cos                                                                    (                                                                                ω                              c                                                                                (                              t                              )                                                                                +                                                      θ                                                                                (                              t                              )                                                                                )                                                              +                                          j                                                                                sin                                                                          (                                                                                ω                                c                                                                                (                                t                                )                                                                                +                                                          θ                                                                                (                                t                                )                                                                                )                                                                                ]                                ·                                                                                sin                                                  (                                                            ϕ                      m                                                                                (                      t                      )                                                        )                                                                                =                                                          G                ·                                                                                              S                      in                                                                                (                      t                      )                                                                                        ·                                  [                                                            cos                                                                    (                                                                                ω                              c                                                                                (                              t                              )                                                                                +                                                      θ                                                                                (                              t                              )                                                                                )                                                              +                                          j                                                                                sin                                                                    (                                                                                ω                              c                                                                                (                              t                              )                                                                                +                                                      θ                                                                                (                              t                              )                                                                                )                                                                              ]                                                                                (        7        )
As described above, with the outphasing amplification apparatus according to the related art, as shown in the above Formula (1),|Sin(t)|·(cos θ(t)+j sin θ(t))the input baseband signal Sin(t) expressed by the above formula, is converted into a Radio Frequency (hereinafter referred to as RF), and the outphasing combined signal Sout(t), the gain of which has been amplified by G times, can be obtained. Thus, the linearity amplification apparatus using the two amplifiers 6a and 6b, which are constant amplitude amplifiers, can be achieved.
Under the condition in which the non-linearity compensation unit 1 is operated, in the above Formulas (1) to (7). Sin(t) may be replaced by Spd(t), |Sin(t)| may be replaced by |Spd(t)|, and |Sin|pk may be replaced by Spd|pk.
Hereinafter, for convenience of the descriptions, one of two routes branched by the signal separation unit 2 from the DAC+Filter 3a to the first amplifier 6a is referred to as a first branch or simply a branch, while the other one of the two routes branched by the signal separation unit 2 from the DAC+Filter 3b to the second amplifier 6b is referred to as a second branch or simply a branch.
When the Chireix combiner is used as the combining unit 7, as described above, the amplitudes of the output signals S1(t) and S2(t) of the respective amplifiers 6a and 6b become imbalance, because of the asymmetric input impedances of the respective input ports of the combining unit 7 viewed from the two amplifiers 6a and 6b. Thus, there is a problem that non-linearity is generated in the outphasing combined signal Sout(t), which is the output signal of the combining unit 7, even when a constant amplitude amplifier such as a saturation amplifier is used as the amplifiers 6a and 6b.
Moreover, when the phase difference between the input signals S1(t) and S2(t) from the two amplifiers 6a and 6b input to the combining unit 7 is increased to control the amplitude of the outphasing combined signal Sout(t) to be small, the amount of cancellation of the amplitude of the outphasing combined signal Sout(t) decreases due to the above amplitude imbalance. This leads to another problem that a dynamic range of the amplitude (output power) of the outphasing combined signal Sout(t) becomes narrow.
The above problems will be described with reference to the drawings.
FIG. 14 shows a phase relationship in the RF between S1(t) and S2(t) (and −S2(t)) and Sout(t) when the amplitudes of the input signals S1(t) and S2(t) from the respective amplifiers 6a and 6b to the combining unit 7 are equal (|S1(t)|=|−S2(t)|).
FIG. 15 shows a phase relationship in the RF between S1(t) and S2(t) (and −S2(t)) and Sout(t) when the amplitudes of the input signals S1(t) and S2(t) from the respective amplifiers 6a and 6b to the combining unit 7 are not equal (|S1(t)|=|−S2(t)|).
Both FIGS. 14 and 15 show the phase relationship using, as a reference (by replacing the RF phase (ωC(t)+θ(t)) by zero), the RF phase (ωC(t)+θ(t)) of the outphasing combined signal Sout(t) when the amplitudes of the input signals S1(t) and S2(t) from the respective amplifiers 6a and 6b to the combining unit 7 are equal (|S1(t)|=|−S2(t)|) in order to simplify the drawing.
As can be seen from the comparison between FIGS. 14 and 15, with respect to the same φm(t), which has been controlled according to Sin(t), there is a phase difference ΔΨ(t) between Sout(t) when the amplitudes of the input signals S1(t) and S2(t) of the combining unit 7 are not equal (|S1(t)|≠|−S2(t)|) and Sout(t) when the amplitudes of the input signals S1(t) and S2(t) of the combining unit 7 are equal (|S1(t)|=|−S2(t)|). This phase difference ΔΨ(t) corresponds to an AM (Amplitude Modulation)/PM (Phase Modulation) non-linearity characteristic. Here, the AM/PM non-linearity characteristic shows a change in an input/output phase difference (=phase of outphasing combined signal Sout(t)-phase of input baseband signal Sin(t)) with respect to a change in the amplitude (hereinafter referred to as an input amplitude as appropriate) of the input baseband signal Sin(t) before signal separation (i.e., the signal before being separated into the phase modulated pair signals SC1(t) and SC2(t).
FIG. 16 shows an example of the amplitude imbalance (deviation) characteristic of |S1(t)| and |−S2(t)| with respect to a phase control amount of SC1(t) and −SC2(t) in the Chireix combiner (combining unit 7). Here, the phase control amount of SC1(t) and −SC2(t) is a phase control amount (±(90−φm(t)) deg; 0 deg≤φm(t)≤90 deg) to be added to the phases of the input signals S1(t) and S2(t) of the combining unit 7. A maximum amplitude can be obtained by making the phases of SC1(t) and −SC2(t) in-phase with each other i.e., (90−φm(t)=0 deg). This phase control amount is referred to as an outphase angle, because it is a deflection angle from the in-phase.
FIG. 17 is a diagram showing an amplitude imbalance (deviation) characteristic of the Chireix combiner (combining unit 7) for the absolute value (90−φm(t) deg; 0 deg≤φm(t)≤90 deg) of the phase control amount of SC1(t) and −SC2(t) in FIG. 16 expressed as a deviation (dB), which is converted into the ratio of |S1(t)|/|−S2(t)| to logarithmically transform it.
It can be seen that for the absolute value of the phase control amount of SC1(t) and −SC2(t), the amplitudes of |S1(t)| and |−S2(t)| are equal only at a few points including 0 deg at which the amplitude of the outphasing combined signal Sout(t) reaches its maximum. However, with the outphasing amplification apparatus according to the related art shown in FIG. 12, the inter-branch amplitude imbalance (deviation) characteristic shown in FIGS. 16 and 17 cannot be compensated, because no means for observation and compensation is included.
FIG. 18 shows a change in the amplitude (output power) of the outphasing combined signal Sout(t) normalized with the maximum value as 0 dB for the absolute value of the phase control amount of SC1(t) and −SC2(t). In FIG. 18, the dynamic range when there is an inter-branch amplitude imbalance (deviation) shown in FIG. 16 is compared with the dynamic range when there is no inter-branch amplitude imbalance (deviation).
When there is no inter-branch amplitude imbalance (deviation), the dynamic range is wide. On the other hand, when there is an inter-branch amplitude imbalance (deviation), the dynamic range of only about 22 dB is achieved, because when the phase difference between the input signals S1(t) and S2(t) from the two amplifiers 6a and 6b to the combining unit 7 in the outphasing control operation is increased to control the amplitude of the outphasing composite signal Sout(t) to be small, the amount of cancellation of the amplitude of the outphasing combined signal Sout(t) decreases.
FIG. 19 shows an example of an AM/AM non-linearity characteristic and an example of the AM/PM non-linearity characteristic caused by the inter-branch amplitude imbalance (deviation) shown in FIG. 16. Here, the AM/AM non-linearity characteristic refers to a change in an output amplitude ratio (=amplitude of normalized outphasing combined signal Sout(t)/amplitude of input baseband signal Sin(t) before signal separation) with respect to a change in the amplitude (input amplitude) of the input baseband signal Sin(t), which is a signal before being separated into the phase modulated pair signals SC1(t) and SC2(t). The AM/PM non-linearity characteristic is as described above.
In a low input amplitude region where the amplitude of the outphasing combined signal Sout(t) is lower by 22 dB or more than the input amplitude at which the amplitude reaches its maximum, the influence of the inter-branch amplitude imbalance (deviation) is large, and thus the input baseband signal Sin(t) cannot be reproduced with the decrease in the amount of cancellation of the outphasing combined signal Sout(t) caused by the inter-branch amplitude imbalance (deviation). As described above, there is a problem that non-linearity compensation according to the related art alone cannot completely compensate (both of) the AM/AM non-linearity characteristic and the AM/PM non-linearity characteristic particularly in the low-input amplitude region. In the non-linearity compensation according to the related art, the input baseband signal Sin(t) before signal separation is compared with the outphasing combined signal Sout(t), and the non-linearity of the entire outphasing amplification apparatus is compensated for the input baseband signal Sin(t) before signal separation.
In order to solve the above-described problem, an apparatus including means for compensating the inter-branch amplitude imbalance (deviation) between two branches in the outphasing combining has been proposed (see, for example, Patent Literature 1, 2, and 3).

Amplification apparatus and amplification method


The disclosure describes a driving device for a mill including a gear ring, suitable for being fastened to a grinding chamber, a first reduction transmission suitable for transmitting a rotation from a first motor to the gear ring, the reduction transmission comprising a case, an output module including an output pinion and an output shaft defining an output axis. The gear ring has helical teeth, the output pinion has helical teeth, the or each output module can be inserted in a single piece into the associated case in an insertion direction or removed in a single piece from that associated case in a removal direction. The driving device includes a disconnectable connecting element suitable for rotatably connecting the output shaft to a transmission element and allowing, in a disconnected state, a rotation of the output pinion around the output axis upon removal of the output module outside the case or during insertion of the output module into the case.

1. Field of the Invention
The present invention relates to a driving device for a mill, in particular a horizontal mill comprising: a gear ring suitable for being fastened to a grinding chamber and extending around a ring axis, a first reduction transmission suitable for transmitting a rotation from a first motor to the gear ring, the or each reduction transmission comprising: a case, at least two output modules each including an output pinion and an output shaft defining an output axis, each output pinion meshing with the gear ring.
2. Description of the Related Art
A driving device of this type is known from document WO-2011/083274.
This device comprises a gear ring and an output pinion meshing with the gear ring. The gear ring and the output pinions are provided with spur teeth.
However, driving devices with spur teeth have a number of drawbacks, for example such as limited transmission power for a given size.
The invention therefore aims to increase the transmissible power for a given size, while allowing quick and inexpensive upkeep of the driving device.

Compagnie Engrenages et Reducteurs—Messian—Durand


Polycapillary chromatographic column contains a set of parallel channels isolated from each other, walls of the channels on the inside are covered with sorbent, and are joined with walls of adjacent channels on the outside by fusing. Feature of a column is that it is produced as set of modules of a various level, thus the module of the lowest level represents hexagonally packed and having in cross-section shape of a correct hexagon set of the channels which are produced by joint drawing of a bundle of monocapillaries in the softened condition. The module of each higher level represents hexagonally packed and having in cross-section shape of a correct hexagon set of modules of the previous level, growing out by their joint drawing in the softened condition. All modules of the highest level (the modules are made in shells 2 on the drawing) are grouped in the uniform hexagonally packed structure (on the drawing it is surrounded with an external protective shell 3), produced by their joint drawing in the softened condition.

1. Field of the Invention
Proposed inventions are related to area of analytical chemistry, namely to a chromatography and to fabrication methods of the chromatography equipment elements, more concrete—to the chromatographic column and method of its manufacturing.
2. Description of Related Art
One of modern tendencies of analytical chemistry is a miniaturization of chromatographic equipments, including use of capillary columns in the chromatography (Tesarszik K., Komarek K. Capillary columns in gas chromatography (in Russian—translation from Czech).—Moscow, Publishing house "Mir", 1987, 222 p. [1]). Using the capillary columns with a sorbent located on internal walls has allowed to increase specific and general efficiency of achievable separation, to reduce sorbent consumption, to increase considerably sensitivity of chromatographic analytical system and to improve such characteristics of process as a radial gradient of temperature at programming, to simplify realization of hyphenated method of the gas chromatography analysis in a combination with mass-spectrometry.
Separation of substance sample on its components in a chromatography is determined by two characteristics of chromatographic column—its selectivity and efficiency. Measure of selectivity is relative retention of separated components, and measure of efficiency is characterized by number of so-called theoretical plates. Basic advantage of the chromatographic capillary columns is that on absolute and relative efficiency of these columns essentially surpass traditionally used chromatographic packed columns having diameter more then 2 mm. Total efficiency of capillary columns is 30000–100000 theoretical plates, and more (Rudenko B. A. Capillary chromatography (in Russian)—Moscow, Publishing house "Nauka", 1978.—215 p. [2]) that much more surpasses efficiency of the packed columns.
Together with such advantage as high efficiency of sample components separation, chromatographic capillary columns have the disadvantage consisting in significant restriction of the sample's weight. It reduces a signal magnitude at the analysis and sharply increases the limit of determined concentration.
This advantage is reduced in polycapillary (multichannel) chromatographic columns, being a package of 1000–2000 capillaries of diameter from 30 up to 100 micrometers located in parallel to each other (the inventor's certificate of the USSR No968181, issued 15.08.91 [3]; inventor's certificate of the USSR No1635128, issued 15.03.91 [4]; patent of the Russian Federation No1651200, issued 23.05.91 [5]).
However, when the column has such limited number of capillaries, then even insignificant distinctions in amount of the deposited mobile phase in them result in occurrence of a significant dispersion of retention times of substances. The dispersion essentially reduces efficiency of separation achievable with the aid of such columns. As a result, the efficiency of such columns stops increase when their length surpasses 1.0–1.5 m.
In inventor's certificate of the USSR No1635128 (issued 15.03.91 [6]) the method of manufacturing polycapillary chromatographic columns is proposed. The method's purpose is increasing uniformity of the columns' flow areas. The method provides manufacturing a column by softening and drawing bank of blanks formed from cylindrical rods of identical size. The rods forming central part of the blank of each separate channel are made from a technological material, should be later removed. Rods, surrounding the central part, are produced from the base material. These rods after removing the technological material form a walls of the channel. A package of blanks is formed in a way, providing hexagonal or square packing the rods' group
Known method on the inventor's certificate of the USSR No1635129 (issued 15.03.91 [7]) in comparison with previous is more complicated. Some of the rods surrounding rods of the blank's central part of the single channel are also produced from the technological material. After removing the technological material, it results in formation of longitudinal grooves in walls of the channels. The grooves connect the joint channels with each other.
Thus, polycapillary chromatographic columns made by the methods, known from [6] and [7], contain set of the parallel channels. The channels are joined by fusion of external walls of the adjacent channels. At that in the column made by the method known from [6], channels are isolated from each other, and in a column known from [7] the adjacent channels are connected with each other by means of longitudinal grooves in their walls.
Polycapillary chromatographic columns made according to the specified methods require large labor-consumption. The large labor-consumption is caused by the necessity of manual forming the blank of each channel. At that, it is not possible to produce the blank having channels number exceeding provided in known columns [3–5]. Therefore, further increase of the chromatographic column parameters is impossible. Therefore, realization of advantage of the manufacturing methods known from [6, 7] is impossible too.
Polycapillary chromatographic column and method of its manufacturing known from the inventor's certificate of the USSR No1635128 [6] are closest to the proposed column and method.

Abstract: The method of columns manufacturing consists in realization of several stages drawing of blanks packages, each of which is drawing result at the previous stage, and cuttings produced at drawing items on a part of the specified length—blanks.

Abstract: The micrometer and submicrometer size of channels are achieved at their number equal 1 million in order of magnitude with small dispersion of the channel diameters.


Network site testing of other sites in a communication network environment may be performed with the assistance of all sites participating to identify and confirm failures. One example method of operation may include transmitting a test message from a test site to a network site, the test message solicits a feedback response from the network site, determining whether a feedback response message was received from the network site, and determining whether the network site is in an up state or a down state based on the feedback response message being received or not being received. Other sites and triangulation may be used to confirm a sub-network status.

Conventionally, as networks grow to include additional sub-networks, devices, and/or switches/routers, the likelihood of bottlenecks, traffic congestion, and failures continually increases. Most monitoring applications are manual and do not take proactive measures to continually monitor and mend network failures. For example, a server may have a diagnostic tool managed by an administrator to manually identify computers on the network to determine if their diagnostics (i.e., packet rate, CPU usage, memory usage, etc.) are optimal when compared to other devices. However, once the diagnostic tool monitors network devices and/or traffic for 24 hours or however long it was commissioned to perform such actions, the tool normally stops monitoring and does not offer any additional information or actions necessary to correct failures and other network anomalies.

Network monitoring to perform fault isolation


The read circuit can be applied to optomechanical scanning imaging devices. The circuit is designed for the reading of batteries of photodetectors comprising a specified number N of detection channels, each constituted by N.sub.d sensors positioned in the scanning direction, such that each point of an image is successively analyzed by N.sub.d sensors of a channel. The circuit includes a current summation scale, associated with each detection channel, formed by a specified number M of current summation circuits and coupled to the detection channel by means of a voltage-current conversion device. Application to the thermal imaging devices.

The present invention relates to a circuit for the reading of linear arrays of photodetectors. It can be applied especially to high-performance thermal imaging devices using optomechanical scanning of the image perpendicularly to a linear array of photodetectors.
In these imaging devices, the scanning is done by an appropriate optomechanical system comprising in particular a mobile mirror and an optical assembly for the formation and projection of an image of the observed scene on the detection linear array.
Conventionally, in the direction perpendicular to the scanning, the linear array comprises a number N of detection channels enabling the parallel reading of N instantaneous fields. In order to improve the sensitivity of the imaging devices, each detection channel comprises a determined number N.sub.d of "sensors" aligned in the scanning direction, such that each point or pixel of the image-taking field is analyzed successively by N.sub.d sensors. The improvement of the sensitivity is obtained by the recomputation, in phase, of the electrical signals delivered by each of the sensors of one and the same channel and then by the adding together of these signals. Since the noise is added quadratically, the addition of the signals given by the N.sub.d sensors enables the signal-to-noise ratio to be improved by the factor .sqroot.N.sub.d . This processing of the signals is known in specialized literature as "time delay and integration" or TDI.
In the known embodiments, with each detection element there is associated a circuit for the injection and integration of the photo-charges generated by the photosensitive cells proportionally to the illumination received. At the end of the integration period, the state of the integrator is read either by means of a shift register comprising as many lateral inputs as the detection channel or, in the CMOS technology structures, by a summation circuit comprising switched-capacitance operational amplifiers.
Since the number of information elements during processing, at a given point in time, is set by the number of detection channels "N", the number of sensors per channel N.sub.d and the ratio between the pitch P.sub.d of the sensors and the sampling pitch P.sub.e of the image in the scanning direction and since each of these information elements is assigned to a Time Delay and Integration (TDI) operator comprising N.multidot.N.sub.d .multidot.P.sub.d /P.sub.e summation devices, the dimensions of the linear arrays are soon limited firstly by the space requirement of the read circuit and secondly by the dissipated power. For example, if N=1000, N.sub.d =10 and P.sub.d /P.sub.c =3, 30,000 TDI summation devices are needed.
Furthermore, the low frequency noise, the limited gain, the gain variations and offset variations of the operational amplifiers, combined with the fluctuations of the values of the summation capacities, lead to the superimposing, on the restituted video signal, of an additional noise that is difficult and costly to correct.

Circuit for the reading of linear arrays of photodetectors


An input device includes a keyboard system where the keyboard system includes a keyboard transmit line electrically connected to an integrated circuit, a keyboard sense line electrically connected to the integrated circuit, and the keyboard transmit line and the keyboard sense line are selectively connectable through a switch incorporated into the keyboard system. The input device also includes a capacitive touch system where the capacitive touch system includes a touch transmit line electrically connected to the integrated circuit, and a touch sense line electrically connected to the integrated circuit. The keyboard system and the capacitive touch system use at least one common component of the integrated circuit during operation, and the keyboard system and the capacitive touch system are executable simultaneously.

The present invention relates to computing devices in general and, in particular, to computing devices with a keyboard. The keyboard generally includes an arrangement of keys where each key is connected to an electrical switch located under the key. Multiple transmit lines provide a voltage to one side of the switches associated with different keys. The other side of the switches are connected to different sense lines. When the switches close in response to a user depressing the keys, the respective transmit lines and sense lines are temporarily brought into contact. This temporary contact can be detected by measuring the voltage on the sense lines.
An example of a circuit that operates both a touchpad and a keyboard is disclosed in U.S. Patent Publication No. 20070279385 issued to Richard D. Woolley, et al. (hereinafter, the '385 Publication). This reference expressly teaches that touchpad sensor control circuitry can control the operation of a touch or proximity sensitive touchpad in a first mode, and in a second mode functions as a keyboard controller. The touchpad sensor control circuitry also determines which keys on a keyboard have been actuated by manipulation of keys, wherein pressing a key is detected by the touchpad sensor control circuitry.
In another embodiment described in the '385 Publication, a touchpad and a keyboard are both active at the same time. This mode of simultaneous operation is possible because the touchpad sensor control circuitry is operating in a typical capacitive mode. But it should also be realized that because the keyboard and the touchpad are both active, this embodiment draws more power than in embodiments where the circuitry switches modes to operate the touchpad or the keyboard independently. In the embodiment where the circuit simultaneously controls the keyboard and the touchpad, the '385 Publication describes that the touchpad sensor control circuitry is coupled to the touchpad via a grid of electrodes where a first set of electrodes are configured as X electrodes, and a second set of electrodes are configured as Y electrodes. All measurements of touchpad parameters are taken from a single sense electrode, and not from the sets of X or Y electrodes. The '385 Publication further explains that the sense electrode is not disposed in the same layers as the X and Y electrodes. Instead, the sense electrode is electrically isolated from the X and Y electrodes.
The '385 Publication describes that the keyboard is redesigned to have a plurality of keys arranged to be disposed above the grid. The grid of X and Y electrodes intersect underneath the keys of the keyboard. When any key of the keyboard is pressed, the mutual capacitance between the X and Y electrodes and the sense electrode beneath that key will be changed, and that change in capacitance is detected by the touchpad sensor control circuitry.
A second prior art reference, U.S. Pat. No. 6,204,839 issued to Stephan A. Mato, describes a combination keyboard and pointing device is incorporated in a portable computer and includes a dielectric base member on a top side of which a spaced series of electrically conductive pad member portions of a capacitance-based proximity sensing system are formed. Manually depressible key members are positioned above the pads. With the sensing system switched to a typing mode, the pads capacitively sense the proximity, velocity and acceleration of a user's fingers depressing their associated keys and output signals useable by the computer to display the character associated with the depressed key. A sensed increased stroke velocity of each manually depressed key may be used to alter the key character image displayed on the screen, for example capitalizing, bolding or underlining the character. The sensing system may be manually or automatically switched from its typing mode to a pointing mode in which it capacitively senses various hand and finger motions and orientations to carry out various pointing functions, such as cursor movements, pick functions, and scrolling functions, in response to the sensed hand and finger motions and orientations. Both of these references are herein incorporated by reference for all that they disclose.


A printable recording material that contains an opaque supporting substrate; a resin-rich barrier layer; a coating composition with bimodal pore size distribution; and an ink colorant-receiving layer. Also disclosed herein are the method for making such material and the method for producing printed images using said printable recording material.

Inkjet technology has expanded its application to high-speed, commercial and industrial printing, in addition to home and office usage, because of its ability to produce economical, high quality, multi-colored prints. This technology is a non-impact printing method in which an electronic signal controls and directs droplets or a stream of ink that can be deposited on a wide variety of media substrates. These printable media or recording material can be cut sized sheets or commercial large format media such as banners and wallpapers. Current inkjet printing technology involves forcing the ink drops through small nozzles by thermal ejection, piezoelectric pressure or oscillation, onto the surface of such media. Within said printing method, the media substrate plays a key role in the overall image quality and permanence of the printed images.
Nowadays, there is a growing demand for digitally printed contents which is no longer limited to the "traditional" black-white text images and full color photo images, but extends also to prints with visual special effects such as the metallic appearance and/or reflectivity, for example. Accordingly, investigations continue into developing media and/or printing methods that can be effectively used with such printing techniques, which imparts good image quality and which allow the production of specific appearances.

Hewlett-Packard Development Company, L.P.


Disclosed is an apparatus for manufacturing carbon nanotube fibers, which includes: a synthesis furnace that provides a space therein where a carbon nanotube fiber is synthesized; a raw material supplier that supplies a liquid-state raw material for a carbon nanotube into the synthesis furnace; a gas supplier that supplies a carrying gas into the synthesis furnace; a sub-synthesis furnace that is formed in the shape of a pipe and disposed at the upper portion in the synthesis furnace, and in which the raw material for a fiber flows along the inner side; a nozzle that sprays the raw material for a fiber supplied by the raw material supplier to the inner wall of the sub-synthesis furnace; and a heater that disposed along the outer side of the synthesis furnace.

Carbon nanotube filaments can fall into a complex made by mixing a carbon nanotube with a polymer and one made of only a carbon nanotube.
The former is manufactured as a complex by melting a polymer, which is matrix, with a solvent or heat and then mixing it with a carbon nanotube, in which the technology of distributing the carbon nanotube is the most important technology, and it is a typical method for the latter to manufacture a filament through a post process after producing a carbon nanotube on a board. Also, the method has a problem in that the process of depositing a catalyst onto a board and continuous production of carbon nanotubes with a synthesis furnace closed are limited.
In the methods of manufacturing high-purity carbon nanotube fibers in the related art, a method of manufacturing fibers by directly spraying a solution with carbon nanotubes distributed into a container rotating with a polymer solution therein so that the polymer solution penetrates in between the carbon nanotube particles and bonds the carbon nanotubes is generally known.
When a solution is directly sprayed, as described above, however, there is a problem in that the polymer solution is distributed slowly between the carbon nanotubes and the efficiency of manufacturing carbon nanotube fibers is limited due to a limit in rotation speed of the container filled with the polymer solution. In addition, since there is polymer of around 30 wt % is in the manufactured carbon nanotube fibers, there is a limit in expression of excellent properties of the carbon nanotubes.
Korean Patent Publication No. 2012-0090383 can be exemplified as a prior art of the present invention.

Apparatus for manufacturing carbon nanotube fibers

SOONGSIL UNIVERSITY RESEARCH CONSORTIUM TECHNO-PARK


A method (100) for standardizing gene nomenclature, comprising: (i) receiving (110) a source; (ii) tokenizing (120) the source; (iii) comparing (130) a first token to a prefix tree structure with a root node, edges, and leaf nodes; (iv) determining (140) which edge extending from the root node to associated first leaf nodes the first token matches; (v) updating (150) an identification pointer with the location of the first leaf node; (vi) determining (160) which of one or more edges that a second token matches; (vii) updating (170) the identification pointer with the location of the second leaf node; (viii) repeating (172) the determining (160) and updating (170) steps with subsequent tokens until a subsequent token fails to match an edge extending from a leaf node or there is no edge extending from the leaf node; and (ix) providing (180) an identification of a canonical gene name.

Given an accelerating focus on precision medicine, including increasing numbers of clinical trials targeting the therapeutic treatment of patients with particular genetic variants, the extraction of pertinent information from patient medical records and clinical trial descriptions must include identification and extraction of mentions of particular genetic tests and variants.
A gene name is typically a mention in medical text intended to identify a specific gene. Such a mention functions like a noun phrase within text, and its internal composition respects the sensibilities of English or other natural language. But its nomenclature often consists of highly-technical molecular and clinical vocabulary, sub-specialty notations, other jargon, and acronym-like symbols. Thus, the gene name is typically a hybrid between natural language and a special notation. Recognizing a gene name involves locating the mention, classifying it as a gene name, and identifying the specific referenced gene.
In addition to recognizing a gene name, there are benefits to normalizing gene names. Normalizing a gene name typically requires an understanding of the range of possible mentions which identify the same gene, appreciating or determining that one of those mentions is the preferred representative for that range (the "canonical name"), and associating the observed mention with its preferred representative.
There are existing systems that attempt to deal with recognition and normalization of gene names. For example, there are multiple specifications and standards for gene nomenclature, multiple databases of gene names and relationships among them, and multiple machine-learning systems that marry naming rules, database entries, and actual naming patterns in text corpora. However, the recall and precision percentages for these methods typically reach the high 70's at best in practice, as gene naming patterns and contexts are highly productive and continue to evolve. Thus, gene name recognizers/normalizers entail dependencies on external sources and tools, and require complex mechanisms and data, yet provide modest performance.

Method and system for normalization of gene names in medical text


In a friction stir welding apparatus that can control a penetrating position of a probe with respect to a processing target member to an optimum position at a time of friction stir welding by detecting a wear volume and a tip position of the probe, as a drive mechanism moves down a holder having a coefficient of thermal expansion larger than that of the probe and holding the probe, a detector can freely detect a length of a member including the holder and the probe, and a probe detection mechanism can freely detect a tip length, which is the length of the member of only the probe.

The present invention relates to a friction stir welding apparatus, and more particularly relates to a friction stir welding apparatus having a probe detection mechanism, a processing-member detection mechanism, and a probe cleaning mechanism.
In recent years, there has been proposed a friction stir welding apparatus that performs friction stirring on a predetermined welding portion in a processing target component formed by a plurality of metal plates such as aluminum plates by a probe rotating at a high speed, in addition to general arc welding, to weld the metal plates with each other. Even in a strength component of a movable body such as an automobile, a configuration having a welding portion welded by a friction stir welding apparatus has been realized.
In such a friction stir welding apparatus, the rotating probe and the processing target component need to be moved relative to each other to weld a predetermined welding portion accurately. Accordingly, it is important to execute friction stir welding by detecting parameters required therefor with high accuracy, taking the detection values thereof into consideration.
Under such circumstances, although it is not related to a friction stir welding apparatus, Japanese Patent Application Laid-open Publication No. 2002-283059 discloses setting of a shaft reference position of a servo spot welding gun and a robot control apparatus therefor. The robot control apparatus has such a configuration that a movable welding tip of the welding gun is pressed against a fixed welding tip until an estimated disturbance load reaches a set first threshold, and when the estimated disturbance load has reached the first threshold, the movable welding tip is driven in a direction in which the both tips are away from each other until the estimated disturbance load reaches a second threshold smaller than the first threshold, to set, update, and store the shaft position of the movable welding tip when the second threshold is reached as a reference position, thereby enabling to obtain and update the reference position in the same manner even when the welding tip is worn off.
Japanese Patent Application Laid-open Publication No. 2007-30017 relates to a friction stirring welding method and discloses a configuration in which after a rotation jig is moved to a temporary setting position determined based on deflection amount data of a support table generated when a welding pressure is applied and thickness data of an overlapped portion, position control of a servo motor is canceled at the temporary setting position and torque of the servo motor is controlled. After a certain time has passed since the start of torque control, a moving distance of the rotation jig is measured, to obtain a welding operation start position based on the obtained moving distance and the temporary setting position, and then a friction stir welding operation with respect to the overlapped portion is performed by using the welding operation start position as a reference.
Japanese Patent Application Laid-open Publication No. H5-138361 relates to a nozzle cleaning apparatus of a welding torch, although it is not related to a friction stir welding apparatus. The nozzle cleaning apparatus includes a pre-processing device 10 in which a plurality of long wires 12 having a tip bent inward and a plurality of short wires 13 having a tip formed in an outward hook shape are erected on a circumference slightly smaller than an opening end diameter of a nozzle 7 of a fixed table 11, and a main processing device 20 in which a plurality of long brushing bars 22 and short brushing bars 23 having fine wires implanted at the end thereof are erected on a circumference slightly smaller than the opening end diameter of the nozzle 7 of a turntable 21 and a cylindrical wire brush 24 is provided in a standing condition outside thereof, thereby eliminating spatters near a gas outlet 9 and circular spatters at the opening end of the nozzle 7.


A fingerprint image capture system comprises an electro-optical material which captures a static fingerprint image and an apparatus for converting the static fingerprint image into an electronic signal. The image capture system includes an electrode for contacting a finger, and a bias supply for creating an electric field where epidermal ridges contact the electro-optical material. A transistor array senses charge or optical density variations in the electro-optical material to create an electronic representation of the fingerprint image. An initialization electrode places the electro-optical material into a uniform condition prior to acquisition of the fingerprint image. A physical artifact of the fingerprint image can be archived by removing the electro-optical material from the system following the fingerprint image acquisition.

Fingerprint capture devices are finding increased use in law enforcement, security, financial, and other applications. The underlying motivation for fingerprint acquisition is the widely accepted belief that fingerprints are unique to an individual, and therefore comprise an exclusive attribute of identification. Biologically, fingerprints consist of raised portions of the epidermis, termed friction ridges or epidermal ridges, on the digits (fingers and toes), the palm of the hand or the sole of the foot, comprising one or more connected ridge units of friction ridge skin. By virtue of this description, it should be evident that the term "fingerprint" can apply to several parts of the anatomy which exhibit a uniquely defined pattern in the epidermis. Historically, fingerprint images were acquired for analysis and archival by application of ink to the skin, followed by making an impression of the skin onto a sheet of paper or cardstock.
The usefulness of a particular fingerprint or set of fingerprint images is intimately tied to their comparison and matching to a known set or database of other fingerprint images. Prior to the availability of computer-based storage systems, comparison and matching were performed manually, and fingerprint images required physical archival. The development of digital storage systems created an opportunity and need for electronic means to acquire fingerprints so as to enable rapid storage, distribution, and searching. A variety of techniques have been developed for this purpose. The internet encyclopedia Wikipedia broadly groups fingerprint readers into solid-state devices and optical readers utilizing one of several physical principles including optical, ultrasonic, capacitive or thermal means for detecting the difference between valleys and ridges on the skin.
In one example of a popular fingerprint acquisition system a Light Emitting Sensor film is used to create a visible image of a fingerprint by electrically exciting a light emitting phosphor using the ridges of the epidermis to couple an alternating current (ac) power source to the film. With reference to FIG. 1, a fingerprint acquisition system and detection film detail of the prior art, a fingerprint acquisition system 100 has capture and display device 110 showing a luminescent fingerprint image 120. An acquisition electronics detail 130 includes skin epidermal ridges 140 making an electrical contact to light emitting film 150 on the surface of an image array sensor 160. An alternating current (to be described infra) is coupled from the skin to the light emitting film 150, which causes the film to glow at the points of contact, resulting in luminescent fingerprint image 120. The image array sensor 160 can be comprised of thin film transistors, cmos sensor pixels, or a ccd device. Skilled artisans will appreciate that the image sensor 160 is essentially similar to image capture devices widely employed in smart phone cameras, video capture devices, scanners, and digital x-ray detectors. The image capture process can employ electronics and software for image acquisition well known to those skilled artisans. The light emitting film 150 is detailed in light emitting film cross section 170, which illustrates the connection of an ac power supply 180 between a top electrode and a phosphor layer within the film. In operation, the fingerprint acquisition system 100 is configured so that the top electrode contacts a portion of the skin, making the epidermal ridges into an electrical potential node. An electrical current is induced between the epidermal ridges and the phosphor layer, providing the energy needed for the phosphor to glow.
The prior art fingerprint acquisition system of FIG. 1 has several undesirable characteristics: First, the visible fingerprint image is present only for the duration that the finger is in contact with the light emitting film and the ac power is applied. Absent a separate retrieval and display system, the fingerprint image cannot be examined once the finger has ceased contact with the device. Because the fingerprint image is constrained to only the portion of the finger contacting the device, it is not possible to obtain an extended contact image by rolling the finger from one side to another. The technique of rolling the finger is commonly employed when acquiring fingerprint images by means of ink and paper. These extended images are valuable for matching to forensic evidence which often includes incomplete or partial fingerprint images acquired from a variety of objects at crime scenes. Next, in order to effectively induce phosphor luminescence, the ac power supply must be of relatively high frequency and high voltage. Typically, the electrical potential is about 80 to 250 volts or more at a frequency of about 500 Hz to 40 kHz. The power supply needed to generate these operating conditions typically adds complexity, cost, and lowers efficiency as compared with a typical low voltage direct current (dc) power supply. Because the visible fingerprint image depends on light emission from a phosphor, the image may be rendered difficult or impossible to see under conditions of high external illumination, for example outside in bright sunlight.
What is needed is an improved means for acquiring a fingerprint image which combines simple low power electronics, image retention during and following capture, and sunlight readability in a low cost system. In particular, a system which combines the best features of both electronic and traditional paper/ink based fingerprint capture would advance the state of the art.
In order to better illustrate the features of the present invention, attention is now directed to FIG. 2, an example of an eletrophoretic display material 200 known in the prior art. Electrophoretic materials are a portion of a broad class of opto-electronic materials which exhibit a change in visible appearance or optical characteristics in response to the application of an electric field. The electrophoretic display material 200 typically has a transparent protective layer 210, a transparent electrode layer 220, with transparent micro-capsules 230 in contact with the transparent electrode layer 220. In one commercial implementation, the transparent micro-capsules 230 are each about 50 to 100 microns in diameter and contain positively charged white pigments 240A and negatively charged black pigments 240B suspended in a transparent fluid 250. A free surface 260 of the electrophoretic display material is typically placed in contact with an array of pixel electrodes, to be described infra. When an electric field is applied between the transparent electrode layer 220 and the free surface 260, the corresponding charged pigments become visible at the transparent electrode layer 220. The electric field is produced by applying a potential between the transparent electrode layer 220 and pixel electrodes which are typically part of a thin film transistor (TFT) backplane to which the electrophoretic display material 200 is laminated. A first bias condition is produced by positively charged pixel electrodes 270A. This first bias condition results in incident white light illumination 280 having a white-colored response 290A. A second bias condition is produced by negatively charged pixel electrodes 270B. This second bias condition results in incident white light illumination 280 having a black-colored response 290B. The charge to each capsule can also be bifurcated resulting in a half white half black surface. A combination of both positive and negative charges produces bifurcated pixel electrodes 270C. This bifurcated charge condition results in incident white light illumination having a gray-colored response 290C.
Other variations of electrophoretic materials are known which produce a similar optical response to applied electric fields. For example, in a presentation "Low Cost Flexible Displays Using Nanoscale Droplets" by Mateusz Bryning, PhD a display material is described as comprising charged nanosize ink droplets dispersed in a porous matrix. In a presentation published on the world wide web, CLEARink Displays discloses a electrophoretic display material in which charged particles modulate the response of the display material by disrupting a process of total internal reflection in the top plane of the display material.

Method for capture of a fingerprint using an electro-optical material