Study On The Key Technologies Of Subset Based Coherent Fast Frequency Hopping Communication Systems

Frequency hopping is one of the commonly used techniques in military communications.Frequency hopping communication is divided into Fast Frequency Hopping(FFH)and Slow Frequency Hopping(SFH).Fast frequency hopping is widely used in modern electronic warfare because of its excellent anti-interference,anti-interception and anti-multipath characteristics.The fast frequency hopping communication technology can not perform channel estimation because each frequency point is independent of each other,and uses a non-coherent modulation and demodulation transmission system.The frequency subset-based coherent fast frequency hopping technology has the anti-jamming and anti-acquisition capabilities of traditional FFH systems,while overcoming the difficulties of channel estimation in fast frequency hopping,by using coherent modulation and demodulation methods,Improve the spectrum efficiency and scalability of the system.This paper mainly studies the key technologies of S-CFFH system,mainly including: from the perspective of channel coherence time,gives a reasonable frame format design of S-CFFH system,thus ensuring the channel estimation is feasible;Based on the frame format design,given System parameter design.The system's anti-jamming performance was analyzed and simulated under the interference environment.The system was constructed and implemented based on the Nutaq software radio platform,and the anti-jamming test under AWGN and fading channels was performed at the same time.The work of the thesis is mainly divided into the following three parts and is elaborated as follows:First,based on the concept of frequency subsets,the overall design of the S-system was completed.On the basis of traditional fast frequency hopping communication,the division of frequency hopping frequency subsets is studied,the difficulty of channel estimation in frequency hopping communication is solved,and the non-coherent modulation and demodulation mode is transformed into a coherent modulation and demodulation system.Frame structure design scheme.Secondly,the anti-jamming performance of S-CFFH system is analyzed.In the interference-free environment,the BER performance of the S-CFFH system in the AWGN channel and the three typical fading channels is analyzed.The results show that the S-CFFH system has both spectral efficiency and bit error ratio(BER).Advantages of coherent transmission system;In the case of multi-tone interference,partial noise interference,and pulse interference,the pulse suppression method based on packet detection and the overlap-based windowing frequency-domain interference suppression technology based on maximum likelihood are greatly improved in this paper.Finally,the implementation of the S-CFFH system was completed based on the Nutaq software radio platform.The design scheme and implementation scheme of the transmitter and receiver are given in detail.The anti-interference performance of the S-CFFH system is tested based on the platform.The measured results show that the S-CFFH system has strong anti-interference ability.