ents, a special requirement has Transient phase and to be taken into account. Because TDMA is used, there are adjacent frequency measurement channels in both the frequency domain and the time domain. Be- cause of this, the expression "adjacent time slot rejection' has been introduced. This measurement is carried out implicitly by defining Power ramp analysis an appropriate level for the adjacent time slots when sensitivity measurements are carried out. 61.10.2 Transmitter measurements Demodulation and decoding 61.10.2.1 Signal analyser requirements Error recognition Conventional power meters and modulation analysers can only handle settled (static) test signals. This means they cannot be used Figure 61.31 GSM transmitter measurement flowchart to analyse signal packets (TDMA time slots). Even the latest display The radio path or Physical Layer (Layer 1) 61/29 Hopping Attenuator sequences control Sample memory Frequency hopping synthesizer demodulation by digital signal Input processing converter attenuator Measurement by post processing Signalling Figure 61.32 Principle of the signal analyser 61.10.2.2 Principle of the signal analyser 61.10.3 Simulation and analysis of Layer 1 coding R.F. signals at the input of the analyser, shown in Figure 61.32, are attenuated to the correct level for the down converter. The signals As the error free transmission of bits is a prime requirement, the are down converted to an i.f. frequency using a frequency hopping binary data must undergo a certain amount of coding at this, the synthesiser. The signal is then divided into its in phase (I) and lowest level of the data transmission chain. In the GSM Specifica- quadrature phase (Q) components. These baseband signals are di- tions, these functions form part of the channel coding. The industry gitised and stored for post processing. is attempting to implement the coding and decoding functions using VLSI semiconductors. However, great caution must be exercised when ICs of this kind are used in test equipment. If precise informa- 61.10