PCM/FM Telemetry Receiver Sestem

Telemetry system mainly uses the PCM/FM system, the system uses the presettingfilter to limits the signal band, concentration of useful emission power, and uses limitingfrequency discriminator of non-coherent detection method, applied to the fading channelthat difficult to establish the phase-coherent detection. This paper analyzed andsummarized on the basis of the development process of the PCM/FM system, we researchon the following aspects in this dissertation.Firstly, we researched the demodulation technology in PCM/FM system, analyzed thecause that analog phase-locked frequency modulation circuit to achieve low-frequencyresponse characteristics of PCM/FM system is not ideal, and characteristics of analogcircuits is very difficult to debug, and the system is not flexible enough. And then useddigital demodulation method for remote telemetry receiver system, we summarized somebasically demodulation theory and improved some demodulation methods.Secondly, we focused on two demodulation technologies that were the linear FM ztransformation algorithm and envelope detector algorithm. linear FM z transformalgorithms, when the signal to noise ratio is smaller, using the method that improving thelocalization spectral resolution, can got a more accurate peak, and got adaptive selectionalgorithm of results. Envelope detection method is derivation to the constant amplitudeFM wave, which allows the variation of the modulation signal to be reflected in theenvelope.Thirdly, we in-depth researched cordic demodulation algorithm, when input signal isquartered IF signal and the corresponding clock, so the output is the instantaneous phasecorresponding to the input transient signal., but when it is no delay of the channel, theanti-noise performance less than coherent demodulation. On this basis, we put forward animproved cordic differential frequency discriminator demodulation algorithm, after obtainthe instantaneous phase, made the first order difference in the digital domain to completethe signal frequency discrimination, ensure the signal’s anti-dry performance at thechannel without delay. Through the simulation result show that the algorithm reasonable. Finally, we designed working diagram of telemetry remote control receiver system,analyzed the demodulation performance of the above demodulation algorithm. And weanalog IF signal to numerical simulate, analyzed the bit error rate and the demodulateddata, through the experimental data could know the cordic differential frequencydiscrimination is the best demodulation algorithm.