Design And Implementation Of Signal Simulator For A TACAN Test System

TACAN is Tactical Air Navigation System,which can provide both azimuth and distance information for the aircraft.At present,many of our military aircraft are equipped with the navigation system.In order to meet the requirements of airborne TACAN internal and external field testing,it is necessary to develop a TACAN signal simulator to provide an excitation signal source for the test system.Aiming at the problems of large size,low automatic test efficiency and difficult system integration,the basic digital TACAN signal simulator based on PXI bus technology is proposed.The main work contents of the thesis are as follows:1.The thesis introduces the background and significance of the research,analyzes the existing technical solutions,and studies the TACAN principle and direct digital frequency synthesis technology(DDS).2.According to the expected technical indicators of the TACAN signal simulator,the hardware circuit is designed.The FPGA chip is selected and the configuration circuit of the FPGA is designed.By comparing and analyzing the two implementation schemes of PXI interface,the scheme of FPGA+PCI9054 dedicated chip is proposed,and the peripheral circuit and configuration circuit of PCI9054 are designed.The intermediate frequency signal adopts DDS.The chip is generated.Under the control of the FPGA,the AD9951 generates a 70 MHz IF signal,analyzes the principle of harmonic generation in the IF circuit,and designs a 7th-order elliptic filter.3.Software design and simulation.This design uses Verilog hardware description language to design FPGA internal logic on the QuartusII integrated development platform,including baseband signal generation unit,PXI local bus logic unit,azimuth and distance algorithm implementation and SPI interface control.Unit,with Modelsim simulation software,complete the simulation of each functional module,and give the simulation results.After system debugging,the output of waveform is observed on the oscilloscope.The results show that the simulator can generate 962-1213 MHz TACAN full-band signal,and the bandwidth of each channel meets the requirements of less than 1MHz,the azimuth accuracy is less than 0.1 degrees,the simulation distance accuracy is less than 0.1km,which meets the expected technical specifications.The simulator can be used for TACAN internal and external field testing.