Hardware Design Of Portable Transponder Test Equipment Based On Zero-IF Technology

At present,the industry of civil aviation transportation is facing unprecedented operating pressures such as large flow,high density,and more safety.Air traffic control must be strictly implemented to ensure the flight safety of aircraft.In order to accurately grasp the flight status of the aircraft and implement uninterrupted flight command,the flight order must be maintained through radar.At present,ATC / S mode transponders are widely used in air traffic control systems in many countries.In this thsis,a portable transponder test equipment is designed to meet the increasingly heavy demand of airborne transponder testing.It can generate only A/C mode query signal,A/C/S full call query signal and S mode query signal and identify and demodulate the response signal.And measure the power and frequency of the transponder transmitter according to the test requirements of the transponder.This article introduces the design process of portable answering machine test equipment from technical principles to hardware implementation.The research contents of this article are as follows:1.Cut in from the indicators and functions of the portable transponder test equipment,and analyze it through the A/C and S-mode data communication links of the airborne transponder and the S-mode secondary radar.The technical route of zero-IF architecture in software radio technology and its demodulation algorithm are proposed.Because this design is a portable test equipment,and software radio technology equipment has the characteristics of small size,low cost,easy upgrade,high performance,etc.,the application of radio technology in the design of this test equipment will undoubtedly have huge advantages.2.This design is divided into two parts: hardware design and logic program.In the hardware design,the RF transceiver AD9361 and the FPGA as the baseband processor are used as the RF transceiver solution.The digital interface of the RF transceiver is configured to make the RF transceiver configuration selection more flexible and the baseband processing functions more abundant..At the same time,in order to realize the function of power and frequency measurement,a power measurement circuit and a frequency measurement circuit are designed,and a daughter board of a lithium battery charge-discharge protection circuit is designed to protect the lithium battery.3.In the design of the logic program,an inquiry signal simulation unit capable of correctly generating only the A/C mode inquiry signal,the A/C/S full call inquiry signal and the S mode inquiry signal is designed.In order to correctly identify and demodulate the response signal,a response signal demodulation module is designed to identify whether the response signal is an A/C response signal or an S-mode response signal and demodulate the response signal.At the same time,a power measurement logic program and a frequency measurement logic program are written to complete the reading of power measurement data and frequency measurement,and to complete the data and address communication between the host computer and the FPGA according to the logic program of the PXI communication interface module.Finally,by establishing a test platform,the test equipment functions and indicators are verified.After testing and verification,they have good and stable working characteristics,and their functions can meet the design requirements of the indicators,and the airborne answering machine can be tested.