User Manual DDS200 Digital Demodulation System 070-9952-00

Manual OperationA wide loop bandwidth (HI)should be chosen if the phase of the input signalis has considerable jitter. In this case, most of the phase jitter of the signal tobe analyzed can be compensated for.The medium loop bandwidth (MED) is ideal for general applications.The narrow bandwidth (LOW) can be chosen when the jitter in the signal isexceptionally low.The lower the loop bandwidth, the more reliable the recovery of the transmittedsignal. In the case of problems, refer to the constellation diagram and thecalculated parameters (particularly phase jitter).Selected loop bandwidth High Med LowSet loop bandwidth/Symbol rate 10 –2 5 x 10 –3 10 –3The specified loop bandwidths are normalized to the symbol rate. In the positionHI and a symbol rate of, for instance, 6.900 MSPS, the bandwidth of the loopfilter is 69 kHz.MPEG DATA OUTPUT. The MPEG DATA OUTPUT key opens a submenu wherethe serial and parallel MPEG outputs can be configured with the following mainparameters (see Figure 2–30):Figure 2–30: SPECIAL FUNCTION: MPEG DATA OUTPUT menuREED SOLOMON DECODER: This decoder forms the main part of the errorprotection in the MPEG-2 transport stream. With a BER of 1E-4 in front of thedecoder (in the DDS200 the BER is always measured in front of the decoder), a2–36 DDS200 Digital Demodulation System User Manual