Research On Baseband Signal Process Of Meteorological Satellite Broadcasting System Receiver

Meteorological satellite broadcasting system’s main function is to transmit meteorological information to the launch platform by the information management platform which is based on the server. Meteorological satellite will broadcast this information to the covering area, users can use information receiver to receive weather information, which can be stored and forwarded. This paper studies on baseband signal processing, based on the LRIT data transmission in China’s FY-IV geostationary meteorological satellite, and designs baseband signal process system based on FPGA.Baseband signal process system is divided into BPSK demodulator and channel decoder. BPSK demodulator not only completes the demodulation function, but also has the capability of tracking input carrier frequency offset in a certain range. It consists of carrier synchronization module, which realized by phase orthogonal loops, and symbol synchronization module, which realized by LL-DPLL. Channel decoder implements the functionality of identifying and correcting error code due to noise and interference in transmission. This paper makes a decoding schedule, according to LRIT encoding rules. The decoder contains frame synchronization detection, descramble and concatenated decode, which consists of convolutional code, interleaved code, and RS code.On the basis of introducing key technology principle, this paper focuses on the FPGA-based implementation process. Carrier synchronization, symbol synchronization, frame synchronization and descramble module are programmed by hardware language Verilog, while digital filter and concatenated decode module are designed by IP cores in hardware design tool ISE. Test signal for carrier synchronization is digital IF signal with a specified SNR which produced in Matlab tool. Circuit simulation is in Modelsim software. Channel encoder is designed to generate encoded signal sequence for testing channel decoder.Finally, with the help of high speed digital signal process platform, the baseband signal process system is board tested and verified. Carrier tracking process can be observed by signal generator and spectrum analyzer, and the decoder is validated by Chipscope.