Hardware Design Of Signal Simulation Equipment For TACAN And DME Based On Zero-IF Technology

The Tactical Air Navigation System,referred to as TACAN for short,is a short-range radio navigation system that can provide distance information and azimuth information for aircraft and is widely used in military navigation systems.Distance Measurement Equipment(DME)is a high-precision pulse-type and land-based distance navigation system for civil aviation.According to the specification of PXI bus,a standard 3U board card is designed for the signal simulation equipment.This equipment simulates TACAN azimuth,distance signals and DME distance signals transmitted by beacon stations or equipments,and serve as the excitation source for the on-board TACAN and DME devices to complete their testing functions.In this paper,according to the research status of TACAN and DME system test equipment at home and abroad,the task is proposed,and the functional requirements of signal simulation equipment are briefly analyzed.Based on the characteristics and index requirements of the two kinds of navigation system signals,a signal receiving and transmitting scheme based on zero-IF technology is proposed and its feasibility is analyzed.This technology only needs one mixer to directly output zero intermediate frequency signal.Its structure is simple,convenient for system integration,and reduces the design cost and power consumption.The signal simulation equipment includes hardware circuit design and control logic design.The hardware circuit design is based on the AD9361,a high-performance RF transceiver with zero-IF structure.It can be configured through the digital interface of the processor to achieve programmable functions.It integrates the RF front-end and baseband signals,greatly reducing the design difficulty.At the same time,this design combines the outstanding advantages of FPGA in digital signal processing and ARM in signal control,making the hardware platform more flexible and versatile.This design specifically completed the design of RF transceiver circuit,FPGA and ARM interface circuit,data buffer circuit,clock circuit,PXI interface circuit and power supply circuit.The control logic design completes the ARM configuration of the AD9361 register to enable the reception of TACAN and DME interrogation signals and the transmission of simulated signals,and the Verilog HDL programming of the digital signal processing portion of the FPGA.The subject specifically completed the main and auxiliary reference pulse generation logic,using the DDS principle to generate a sinusoidal envelope signal.For the two pulse forming requirements of TACAN and DME,a dedicated digital FIR filter was designed.At the same time,the TACAN azimuth simulation,TACAN/DME distance simulation control logic are realized,and the FPGA remote update function is completed.Finally,the test platform is built to test the index parameters of the hardware circuit of the signal simulation equipment,prove the practicability of this scheme.The completed signal simulation equipment has good and stable working characteristics.The simulated TACAN and DME signals can achieve full coverage of 962MHz~1213MHz frequency band and have good narrowband characteristics.The accuracy of the simulated azimuth information and distance information meets the index design requirements.And the signal simulation equipment can be used as a signal excitation source for airborne TACAN and DME equipment testing.