The Design And Implementation Of Receiver Based On Software Defined Radio

The essential idea of the SDR (Software Defined Radio) is to establish a universal hardware platform where the A/D (Analog to Digital Converter) is moved as closely as possible to the antenna and the radio functions are accomplished by software as much as possible. SDR is based on a versatile programmable platform to realize all kinds of communication standards and criterions, to meet requirements of many increasing new functions. The agility of systems is highly improved. As another revolution in wireless communication area, SDR has become one of the most important research fields.This paper aims at the studying of the development, the principle, 3 kinds of architectures and features of SDR, and the result shows that the ideal SDR can hardly be realized now because of the deficiency of the electronic devices and technology for the moment. As a compromising method, a single channel SDR receiver platform based on direct intermediate frequency sampling is researched in this paper, which is one of the feasible software radio systems nowadays.In chapter 2, the fundamentals including the sampling theory, digital down converter, multi-rate signal processing technology and the digital quadrature demodulation, which are concerned by SDR, are introduced.In chapter 3, firstly, the performance parameters and the configurations of the receiver's RF front-end are introduced. And the simulation of the LNA (Low Noise Amplifier) and mixer is done to optimize the parameters of the circuits and enhance the performance of the system. LNA is an important part of the receiver; its noise characteristic will greatly affect the noise performance of the receiver. LNA is carried out by the low noise common emitter-common base circuits. LO (Local Oscillator) signal is the core of the receiver. PLL(Phase Locked Loop) frequency synthesizer has many advantages, such as small size, high precision and high frequency stabilization. Signal micro chip PLL IC MB1504 is used as the LO signal source. The mixer which converts the RF signal to the IF signal is realized by the high performance transistor. Finally the test results and analysis of the circuits are given.In chapter 4, a IF receiver sub-system has been designed. The IF signal processing module is established based on the high speed and high precision A/D converter AD6644, the programmable digital down converter AD6620 and the high performance DSP TMS320C6416. AD6644 completes the sampling of the IF signal. AD6620 achieves the reduction of the data flow speed. TMS320C6416 fulfills the demodulation of the base band signal.The SDR system which is designed in this paper is feasible and flexible, and embodies the spirit of the SDR. It provides an implementation method for the SDR receiver sample.