Design And Implementation Of PCM Telemetry Signal Source

The aerospace remote sensing technology is attacking more and more state·s attention inthis information age. The function of the conventional PCM telemetry encoder is single, andcan not meet the requirements of versatility. Therefore, the development of programmablePCM signal source has a very important significance, which has optional code pattern,variable frame structure and adjustable code rate. PCM telemetry signal source is a devicecapable of producing a variety of test signals required by the user, which plays an importantrole in providing a data source for the telemetry ground equipment in the test system.This paper designs a multiple function telemetry PCM signal source, which using FPGAas the main logic control chip. Related basic theoretical knowledge of PCM telemetry signalsource is described in detail in the context of telemetry encoding technique. According to therequirements of technical indicators, the overall design plan of the system is given on thebasis of the above-mentioned technique. The design and implementation of PCM signalsource·s hardware circuit are given, including the USB interface circuit, configuration circuitof FPGA, two output interface circuits, the system power supply circuit and so on. The logicdesign of the signal source is an important part of this paper, this part introduces design andimplementation of the waveform selection module, clock generation module, data buffermodule, frame structure generation module and string conversion module and formatconversion module. Adjustable output PCM code rate, variable pattern and variable framestructure make the three key technologies of this paper. Using the combination of DDS andPLL as frequency synthesizer technology, we achieve the purpose of adjustable outputfrequency; By observing the changing laws of NRZ-L/M/S and BIФ-L/M/S code complyingwith IRIG-106standard, and ultimately the common NRZ-L has been transformed into otherpatterns, thus meeting the requirements of variable pattern. The performance of telemetryPCM sources is analyzed and verified with the help of TarsusPCM-PCI-01made of USA.The six kinds of output pattern of the telemetry PCM signal source are NRZ-L/M/S, BIФ-L/M/S; the output bit rate range is between1Mbps and13Mbps; length of the data wordis8or16; The output waveforms are sine wave, triangle wave, sawtooth and a fixed value.