Detection And Parameter Estimation Of Frequency-Hopping Signal Under Shortwave Channel

The development of short-wave communication technology has endured for decades.However,as its technical level continues to increase,its drawbacks become more and more apparent.This is mainly reflected in two aspects: 1.under the short-wave channel,the types of communication signals are increasingly diversified and various signals are interwiven in the shortwave environment,causing interference.2.The channel quality is poor,the SNR under the channel and the quality of transmission signal are low.At the same time,the frequency hopping signal,with its unique modulation method,has won the good graces of various countries.The constant change of the carrier frequency makes it difficult to be detected and captured.The complex environment of shortwave channel makes the frequency-hopping signal even more powerful.The complex background environment provides a natural barrier for the frequency-hopping signal,making the frequency-hopping signal that is difficult to be captured even more like "a duck to water." Therefore,it is a difficult challenge to achieve reconnaissance and interception of frequency hopping signals in a short-wave environment.However,the challenges engender opportunities.This paper aims to study the detection and parameter estimation of frequency-hopping signals under the short-wave channel with the complex environment.The main work is as follows:1.To complete the detection of frequency-hopping signals in complex channels.The nonstationarity nature of the frequency-hopping signal makes it highly resistant to interception,while the complexity of short-wave channel presents a great challenge for the detection work of frequency-hopping signal.Therefore,the key to the detection of frequency hopping signals lies in :(1)capture characteristics;(2)combating interference.For these two aspects,this paper first studies a non-blind detection algorithm based on energy feature distribution.The algorithm aims at a known frequency hopping signal,uses principal component analysis to signal the projection to the energy domain,whitens the original received data and extracts the main energy characteristics to remove the burst signal interference;then the channelization processing method is used to receive the signal so that the energy characteristics of the signal are decomposed into each channel.After the series of preprocessing,the problem of frequency-hopping signal detection in the short-wave channel is transformed into a general binary signal detection problem.Then the short-term energy feature statistics are extracted and the existence of the frequency hopping is judged by statistical judgment.Finally,the algorithm is validated by the actual data,which shows that the algorithm can achieve real-time detection which can't be achieved by the “batch processing” method while accurately capturing the frequency hopping signal.After the completion of non-blind detection,an algorithm was proposed to achieve blind detection of frequency-hopping signals.The blind detection algorithm aims to more accurately analyze the characteristics of frequency-hopping signals,and then find more superior detection statistics that do not rely on prior information,and finally realize the blind detection of frequencyhopping signal in complex environments.Since the signal is projected to the energy domain by removing the interference through the energy distribution feature,on the basis of this,the blind detection of the frequency hopping signal is realized by constructing the detection statistic in the energy domain.The experimental simulation of the algorithm shows that the algorithm can effectively achieve the blind detection of frequency hopping signals in complex environments.2.The parameter estimation of frequency-hopping signals in complex channels is completed,and a parameter estimation algorithm in short-wave channel is proposed.Accurately extracting frequency hopping features is the key to estimating frequency hopping signal parameters as well as eliminating other interference effects.After studying the analysis of frequency-hopping signals with traditional time-frequency distribution,the Hilbert-Huang Transform(HHT)method was chosen to extract frequency hopping characteristics.The algorithm can adaptively decompose frequency hopping signals for analysis.In view of the complex interference existing in the channel,this paper also integrates the independent component analysis method to deal with the impact of various interference and noise,and improve the feature accuracy and estimation accuracy.