ncerned with the ratio of the total energy stored in a circuit to the energy dissipated per cycle. The second definition relates to the frequency selectivity of a circuit, which is the ratio of the resonant frequency, fo to the 3-dB bandwidth, B. With the first definition it can be said that the larger the value of Q, the more efficient the energy storage element. With the second definition, the larger the value of Q, the better the frequency selectivity of the element due to the reduction of the bandwidth range. In burst-mode transmission, the clock requirements become stricter because the timing recovery must be carried out as soon as the burst signal reaches the receiver. Some Chapter 2 Data Transmission Data Lost Data Received within BER Limits Fig. 2.16 Baseline drift effect in consecutive bursts due to AC coupling. techniques send a preamble before the data signal, which contains clock information. Edge detection techniques (detection of only the rise and fall time of the data pulses) can also be used to almost instantly lock to incoming bursts. Special attention must be considered if system is capacitively coupled (AC coupled) because of the adaptation of the bursts to 0-DC level, which can result in data lost at the beginning of the packet or burst. The amplitude and phase levels of the consecutive bursts are also affected by this baseline drift originated by the AC coupling. Figure 2.16 describes this effect in continuous bursts with different amplitude levels. The extraction of the clock will also be affected by the burst adaptation to the zero-DC level. Synchronization At the receiver, the transmitted digital signal must be interpreted correctly (i.e., the bits received must correspond exactly to the bits sent). If the clock is faster or slower, a mismatch can occur and the receiver will misunderstand the signals. Synchronization in digital signals refers to the process where the receiver will sample the transmitted bits at the correct moment and the correct time. Synchronization can be subdivided into