Development of Algorithm, Architecture and FPGA Implementation of Demodulator for Processing Satellite Data Communication

摘要

This paper proposes a novel VLSI architecture for the demodulator for processing satellite data communication. The overall receiver algorithm is divided into two parts: one to be implemented on an FPGA and the other on a DSP processor. A new distributed arithmetic based architecture for implementing a Sampling Rate Converter is also proposed. The main advantage of this architecture is that it does not employ any MAC unit, whose operational speed is, generally, a bottleneck for high filter throughput. Instead, it makes extensive use of LUTs and hence is ideally suited for FPGA implementation. Architecture for Digital Frequency Synthesizer, which gives 60 dB spectral purity, is also presented. The developed FPGA core consists of a mixer and two numbers of 193 tap, RRC filters to accept modulated, 12-bit, signed ADC output at a sampling frequency of 1.536 MHz and convert it into In-phase (I) and Quadrature-phase (Q) channel outputs, each of size 16 bits, signed, at half the sampling frequency. The main design goals in this work were to maintain low system complexity and reduce power consumption and chip area requirements. These architectures were coded in Verilog HDL and implemented on Xilinx FPGA. The design was synthesized with XCV600-4 FPGA and occupies about 2360 slices with an equivalent gate count of about 45000 and operating at a maximum frequency of 19.8 MHz. The entire modulator and demodulator have been coded in Matlab in order to validate the hardware results. The hardware and MATLAB results compare favorably.