Design And Implementation Of Modem In VSAT Satellite Communication System

It has been 40 years since satellite communications and technologies were put into application in China. They are widely used in customs, banking, commercial sales, news feeds, automobile manufacturing and transport sectors because of its compact structure, low power consumption, low cost, easy to install and low environmental requirements and safety advantages. However the whole communication link of VSAT is almost foreign equipment; and it is inconvenient for aftermarket and maintenance, and there is a certain risk of aftermarket service.Compared with the study in China, the study of the whole system of VSAT is further improved and mature. The standard's development to the development of products are walking in the forefront in China. When software radio technology which rose from abroad came into the domestic, it has been a hot topic in the field of communication immediately; and it gradually developed from GMSK, 4FSK, BPSK, QPSK modulation and demodulation algorithm into multi-band, multirate and multi-mode adaptive necessary techniques of modulation and demodulation in application field.From the lack of research of the VSAT satellite communication system modem device in China, and combined with the existing software radio technology and the latest design techniques in hardware, this text studies the QPSK VSAT satellite baseband modem hardware circuit, and completes a set of hardware circuitry and basic FPGA logic which is parts useful in the present hardware circuit.With comprehensively analyzing the requirements of the hardware resource be used in the modulation and demodulation algorithm VSAT satellite communications system in the circuit schematic design, this text proposed to meet the cost of VSAT adaptive modulation and demodulation algorithm based on dual- FPGA + DSP way; before hardware circuit layout, the design method of signal integrity simulation is used to the simulation of critical signals, therefore obtaining the layout constraint recommend; after the completion of the main device layout and the split of power planes, the method of power integrity design is used to choose capacitors rationally and make the capacitor can achieve good decoupling effect when the whole PCB capacitors are within the operating frequency range of 0 ~ 1GHz. After PCB Layout, signal integrity simulation is carried out to ensure the rational critical signal wiring, thus shortening the development and test cycles and ensure the success of the circuit design.After detection test of the baseband of QPSK modulation and demodulation, the VSAT communications baseband modem hardware in this text is stable and meet the design requirements of hardware resources, and follow-up job will be done by the algorithm development department.