Research And Implenmetation On The Technology Of Spectrum Detection Supporting To The Design Of Aeronautical Communication Signal Waveform

Aeronautical communication environment is complex and varying. Different states of aircraft will lead to different fading channels. When the spectrum is sharing with other communication systems or in the non-cooperative communication system, the signal designing of aeronautical communication system could adjust immediately according to the state of spectrum, thus could improve the communication efficiency. The spectrum detection is very important when monitoring the state of spectrum used. General time-domain detection technology could only judge whether the jamming signal is present. However the frequency-domain detection technology could detect the spectral range of jamming signal, thus could design the communication signal waveform according to the actual conditions. Therefore this paper presents the research and implementation of frequency-domain detection technology which supports the design of aeronautical communication signal waveform.First this paper analyzes the frequency-domain energy detection algorithm, and presents the detail derivation process of the algorithm. Because the Fast Fourier Transformation(FFT) operation will bring about spectrum leakage, this paper presents the cause of spectrum leakage and presents the performance of several window functions which could reduce spectrum leakage. There are some drawbacks with threshold estimation method of frequency-domain energy detection, so this paper presents the Forward Consecutive Mean Excision(FCME) algorithm which changes threshold in real time according to the change of the noise. And this paper presents the simulation result of FCME algorithm used to detect partial-band interference, single-tone interference, multi-tone interference.Then simulate the influence of detection for communication in the cases of different jamming signal. The simulation results show that communication performance is basically consistent in cases of actual detection and ideal detection. This paper analyzes the maximum path loss between transmitter and receiver. Simulate and analyze the difference of spectrum tab detected in transmitter and receiver in the scenario of cruising. Simulate the communication performance in the cases of different jamming signals, and the results show the system has good communication performance no matter where the interference source locates.Finally this paper presents the implementation of detection link in Field Programmable Gate Array(FPGA), and verifies the performance of detection link. The framework includes baseband processing module, frequency-domain amplitude calculating module, detection module. This paper presents the detailed description of design process of the modules in the detection link. The baseband processing module includes down-conversion and down-sampling. The frequency-domain amplitude calculating module includes windowing, FFT, amplitude calculating, frame accumulating. The detection module implements the FCME algorithm, including iterative operation and sorting operation. This paper presents the detailed design process of bubble sort and heap sort which could greatly reduce the processing time of detecting.