Digital Frequency Discriminator Research, And Frame Synchronization

The basic thought of software radio is to take a general, standard, and modular hardware platform as a support and to realize all kinds of the radio's functions through the software programming, setting it free from the method to design a broadcasting station which is based on the hardware and faces to purpose. The first problem which SDR met is digitalize. Along with the fast development of the digital chips, it is urgently to study the digital technology. As well as the telemetry area which is also take the SDR structure. Digital demodulation, bit synchronization and frame synchronization are the key technology of the digital telemetry receiver. Since the usage of digital signal processing technology, compare to the analog system, the digital system has a better performance, less signal distortion, better environmental adaptation and becomes appearing in various applications. So we propose to study the key technology of the digital telemetry receiving system, in order to build a foundation to realize the digital telemetry receiving system.In this thesis, the PCM/FM telemetry signal with 160MHz carrier frequency is directly sampled, digital down-converted and real-time demodulated, then bit synchronized and frame synchronized. Firstly we analyze the theory and algorithm design of digital demodulation related with SDR. Based on the theory, we build the mathematical model of digital demodulation, complete the program of bit synchronization and frame synchronization. Furthermore, we simulate the whole process of DDC and digital demodulation and bit synchronization take the method of combing the Modelsim and Simulink. The simulation results indicate that, system has a good character and well anti-noise performance. According to the simulation structure, we program each part of the system in VHDL language, and finally, realize the digital demodulation and bit synchronization in one FPGA chip. Compared to bit synchronization, frame synchronization is more simple, we just give the model. In the end, the paper introduces the system test results, all the system' parameters meet the technical requirement. The success design of the system, provides a feasibility reference to the development direction of small telemetry receiving system.