Baseband Module Of PCM/FM Digital Telemetry Receiver Design And Implementation

PCM/FM (Pulse Code Modulation/Frequency Modulation) is adopted as the international aerospace telemetry system for a long time for the excellent quality of anti-interference and flexibility. The needs of the missile range and other aircraft telemetry grow rapidly with the development of China’s aerospace industry now, and the related equipment for signal transmitting and receiving, have become one of the main trend of the relevant domestic research institutions and industry design company.We have got great achievement in the field of PCM/FM equipment design recent years while these equipment are un-uniform, poor stability and flexibility. For this, the paper has researched digital receivers aiming at PCM/FM system.This paper has investigated and analyzed standards of domestic and international about PCM/FM technical specifications and features, such as signal spectrum, modulation and demodulation mode, frame format, etc. By combining with the application cases of the domestic markets in recent years, this paper presents a digital design of CPCI architecture based on FPGA, and it deals with the following contents: related technical standard of domestic and foreign, theory of digital receiver design including:sampling and resampling theories, digital parallel polyphase filtering, DDS etc, and mades relevant mathematical theoretical derivation;The paper has designed a mathematical model based on Matlab according to units of signal spectrum process, modulation index, signal bandwidth, shaping filter, rate transformation, parallel processing, code type and frame structure, carrier and bit synchronization etc. By analyzing characters of NRZ-L/M/S, BI with-L/M/S, the paper listes the technical indicators and put forward the scheme of circuit. Finally the paper implements the PCM/FM processing module and validates the system.Bit rate of the implemented module from 10Kbps to 20Mbps with 1Kbps step value while the word length and frame length can be reset within a certain range. Finally the module is verificated by being linked to a standard PCM/FM device.