If Digital Solution To Mediate Expansion Of Technology Research

Digital intermediate frequency receiver is the inevitable choice to satisfy all rigor performance of modern radar. Many companies and research centers attach importance to this field. Direct sequence spread spectrum communication is a technology which can avoid the data being disturbed effectively, This task designed a kind of digital intermediate frequency receiver which can demodulate and despread. The main chip is of the Virtex-Ⅳserial FPGA made by Xilinx Corporation. Significant results of the work include:1. According to the request, the hardware implementation scheme of the digital intermediate frequency demodulate & despread board based on FPGA and high-speed A/D chip is proposed.2. Design of the schematic and six layer printed circuit board (PCB) of the digital intermediate frequency receiver is accomplished by using the software of Protel. Besides this, the hardware installation and debugging is finished. The circuit includes a 14-bits A/D converter of the highest frequency of 65MHz, a XC4VSX35-10 FPGA chip, a 16Mbit flash memory, the system power unit and so on.3. The program and simulation of digital intermediate frequency demodulate & despread is finished on the plane of the software ISE using VHDL language and IP core.4. The debug and test of demodulation and dispreading are accomplished on the plane of designed.hardware of digital intermediate frequency demodulate & despread board, The direct sequence spread spectrum (DS/SS) code is generated from FPGA, then generate modulated signal and send back to the circuit board. The maximum Doppler Frequency can be up to±500KHz.