Based On Fpga-if Digital Despreading Device Research And Engineering

In the view of engineering design and application, according to the requests of the performance characteristics to the IF correlation processing circuit implemented with SAW.P.TDL in the DS-SS(Direct Sequence Spread Spectrum)receiver of the airborne equipment, the substitute scheme of the IF digital correlator based on FPGA is set forth in this dissertation. The prototype has been developed to meet engineering conditions by theoretical analysis, software simulation, math calculation and circuit design etc. Its main performance and technical tests have been done in lab first, and then it has been tested and used on the airborne equipment. All the test results show that its performance characteristics meet the design requests. Some questions in engineering application have been researched and analyzed in detail, including to SAW parts (convolver and programmable tapping delay line) and the frequency response of the IF digital correlation for despreading BPSK DS-SS signal.The main works in this paper are as follows:⑴The IF digital correlator based on FPGA will replace the one based on SAW Programmable Matched Filter in the airborne equipment by theoretical analysis, circuit design and software simulation.⑵In order to make sure whether the circuit gets the excepted target and meets circumstance such as high temperature and low temperature etc, the main performance of the IF digital correlation have been tested and the necessary technical experiments of high temperature and low temperature have been done.⑶The IF digital correlator based on FPGA is put into the SS(Spread Spectrum) receiver instead of the former SAW circuit. We test the EMC (Electronic Magnetic Compatibility) and matching with intermediate amplifier circuit. We also test the parameters about sensitivity, dynamic range and probability to decide whether these parameters meet the request of the receiver.⑷The improvement SS receiver is put into the airborne equipment. We still test the parameters about the receiver and have done the main technical experiments so as to make sure whether these parameters meet the request of the airborne equipment.⑸By contrast the IF digital correlator based on FPGA with the one based on SAW programmable matching filter, especially in the aspect of circuit for the response characteristic of frequency shift, we draw the primary conclusion.