Study On Signal Processing System For Mode-S Aircraft Transponder

Airborne Mode S transponder plays an important role in secondary radar systems. It is a device that is used to receive, identify, reply interrogators signal which is from secondary radar systems. In the field of military identification friend or foe and civilian air traffic control (ATC), it is very significant.With the rapid economic development, the demand for air services is growing. Greater density, high efficient, low cost and avoiding accidents are needed to be settled urgently. Over the next few years, with the opening up of low-altitude airspace, the number of private aircraft will be more and more. For much more effective management, installation of Mode S transponders will be a more effective method for ATC. Miniaturization and low-cost of airborne Mode S transponder will bring about enormous business opportunities.Airborne Mode S transponder has the capability of real-time signal processing and better monitoring, and requires high reliability. In the aspect of communication, not only has it a strong data-link capability, but also is compatible with A/C mode transponders.Based on this, according to the requirement of function and performance, the solution of ARM7plus FPGA hardware platform design was proposed. Around the method of signal processing on this platform, the application of interrogators signal in the Mode S secondary radar syatems was discussed. This paper includes the general design of Airborne Mode S transponder, the terminal hardware circuit design, the software design of signal processing and function. Rational design and layout of the hardware, as well as proper software, ensure that the system can work efficiently and accurately.On the design and implementation, absorbing the researching experience of foreign Mode S transponder products and combining with china’s current needs, we improve the system’s performance and realize the various functions through optimizing the program design. Incorporating new trends and characteristics, with the application of new surveillance systems, such as ADS-B, which not only broadcasts DF11message, but also DF17message, that is just the function of ADS-B OUT. What’s more upgrading the software can make the device more compatible.In order to validate the basic function of Mode S transponder, we took on experiments on it. On the early debugging stage, the standard signal source of simulating interrogation was used. In further stage, for simulating real working environment, various types of interrogation signal were taken to inquiry the transponder alternately with all-purpose tester. The testing result shows that the Mode S transponder achieved the requirements of ANNEX10, which has the characteristics of high sensitivity and low error rate.