Design And Implementation Of Wideband Amplitude Comparison Direction Finding System For Unmanned Aerial Vehicles

The current direction(DF)finding system is mainly arranged on the ground,which is easily affected by buildings,resulting in a decrease in its reliability and direction finding accuracy.The DF system based on unmanned aerial vehicle(UAV)platform can greatly reduce the impact of the above situations due to its aerial advantages,ensuring the reliability and accuracy of direction finding.Due to the limitations of drone load and range,the direction finding system carried by UAV has the characteristics of small structure,light weight,and low power consumption.Based on the characteristics of UAV platforms,this article designs a30MHz～3000MHz broadband DF system for UAVs.The system consists of a DF antenna,a receiver,and a data display module,using the sum-difference amplitude comparison DF method.The receiver adopts a superheterodyne architecture with two-stage frequency conversion,with the first intermediate frequency of 3600 MHz and the second intermediate frequency of 1575 MHz.The main work of this article is as follows:1.Based on the analysis of relevant product indicators at home and abroad and the characteristics of UAV platforms,the DF system scheme and indicators in this article are determined.To reduce the volume,weight,and power consumption of the system,the DF system adopts a sum-difference amplitude comparison DF system and a two-stage mixing superheterodyne receiving front-end structure.2.Based on the principle of sum difference amplitude ratio and two-stage mixing structure,the RF front-end circuit of the receiver was designed.The circuit mainly consists of a mixer,amplifier,detector,attenuator,filter,and sum-difference network.Simulate and verify the gain,noise figure,and spurious suppression indicators of the front-end circuit using ADISim RF and ADS.3.Design back-end circuits based on system functions and indicators,including frequency sources,control modules,and communication modules.The design of the3630-6600 MHz first local oscillator and the 2025 MHz second local oscillator was achieved using ADI’s ADF4356 and ADF4360-2 phase-locked loop chips.Use the STM32 development board to control the front-end circuit.The NRF24L01 wireless communication module is used to achieve communication between the receiver and the ground station.4.Design the front-end circuit PCB board and test the front-end circuit and the entire DF system.The performance testing of the DF system shows that it can meet the usage requirements of unmanned aerial direction finding.The DF system designed in this article has a working frequency of30MHz～3000MHz,a power measurement range of-100 d Bm～-10 d Bm,and a direction finding accuracy of 3°(RMS).