Design And Realization Of Direct Down Conversion Wideband Receiver Based On DSP

The traditional radio receivers rely on the hardware strongly, and the flexibility to different communication systems is bad. It also has the limitation in the range of work frequency. The direct down conversion wideband receiver based on DSP is a new style digital receiver with the essential idea of Software Defined Radio(SDR). It makes up the shortages in stability, flexibility and integration of the traditional radio receivers, and emphasizes using the simplest developable hardware as universal platform where the A/D converter is moved as closely as possible to the antenna and the radio functions are accomplished by software as much as possible.This paper introduces the development of SDR, and analyses the design methods of the digital wireless receivers. Due to the limitation of the device, it is impossible to sample RF signal directly now. So sampling wideband IF signal directly is a feasible method. Firstly, the fundamentals which are concerned about the signal processing technique are introduced, and that lays the foundation for IF receiving and processing platform. Secondly, the circuit design of the RF front end is accomplished. This part mainly processes and transforms the signal from the antenna to IF sampling, including signal amplification, mixing and filtering. This subject places emphasis on the software and hardware design of IF processing platform which is established based on the high-speed A/D converter AD6640 and the programmable digital down converter AD6620 and the high performance DSP TMS320VC5416. The circuit design and debugging of the platform are accomplished, initial program of AD6620 is designed and a fast method of the data transfer and processing based on DSP is given. Finally, the baseband signal is demodulated by the quadrature demodulation algorithm.The receiver platform designed in this paper is universal and flexible, and embodies the spirit of the SDR. It provides a feasible experiment platform for improving the digitized wireless receivers.