.2.3 In channel measurements on transmitters tion about the error correction facilities of a mobile phone is re- quired, for type acceptance for example, the test set must have Some of the most important measurements on transmitters using facilities for injecting and detecting errors at different layers. Such digital modulation are: facilities, however, cannot be realised, as VLSI circuits do not have the required interfaces. 1. Power levels, down to 13dBm for the mobile station. When precise simulations and analyses are required, e.g. during 2. Power ramp up for ramp down using stipulated tolerance mask. development or for approval testing, it must be possible to access all 3. Phase noise, measured as the deviation from the ideal phase levels of signalling. By using the latest fast digital signal processors trajectory. 4. Frequency errors, also derived from phase data. 61.10.2.4 Measuring spectral components The spectral components near the carrier are specified by the mask shown in Figure 61.33. The Tx signal is not continuous because of the TDMA used SO that the measurement cannot be made by simply connecting up a spectrum analyser. This difficulty can be overcome by triggering the spectrum analyser in synchronism with the TDMA Integral antenna frames and displaying the results in zero-span mode. Further spec- trum analyser settings are given in the specifications, a distinction being made between: antenna connector 1. Measurements in the modulated section of the burst (spectrum due to modulation); resolution BW = 30kHz, video BW = 30kHz average mode. 2. Measurements at the edges of the burst (spectrum due to Frequency from the carrier (kHz) switching); resolution BW = 30kHz, video BW = 100kHz max-hold mode. Figure 61.33 Mask used for measurement of spectral components Spurious transmissions up to 12.75GHz must also be checked. 61/30 Telecommunication system measurements (DSP), test sets will be able to carry out real time simulations of Test sets require an enormous amount of memory to completely GSM protocol