Improvement Of Detection And Parameter Estimation Techniques For Frequency Hopping Signals

As one of the most commonly used means of spread spectrum communication,frequency hopping communication has been widely applied communications, especially in the field of military communication, in which it has played a huge potential. Its low-power transmitter and frequency hopping caused by pseudo-random sequence, bring to FH communication characteristics of low probability of intercept, fixed frequency interference,etc. Widely used of FH communications in military communication brought serious challenges to the communication countermeasure. How to detect the existence of the frequency hopping signals, how to estimate the parameters of frequency hopping signals and other problems will follow. In order to solve these two problems, this paper focuses on the blind hopping signal detection and parameter estimation techniques.This article first expounds the basic principles of frequency hopping communication system, and the main parameters involved in the estimate algorithm are briefly described. And further study of the spectrum sensing, time-frequency analysis technology, which commonly used in the field of non-stationary signal processing to provide a theoretical basis for the subsequent algorithm.Then, for blind detection of frequency hopping signals, this paper first discusses the multi-hop autocorrelation detection scheme of frequency hopping signal, and the simulation taken to assess the performance of the algorithm. And then combined the technology of spectrum sensing principle, this paper proposes a new kind of frequency hopping signal detection algorithm based on power spectrum cancellation, In order to compensate for the lack of traditional power spectrum cancellation algorithm in versatility, practicality and other aspects. Compared with the existing algorithm based on autocorrelation or energy, it does not need any assumption about hopping rate or alphabet of hopping frequencies, and constructed a decision parameter with determining threshold to meet the testing under different signal conditions. Using this detection scheme, on the premise of greatly reduced computation complexity, can realize the detection of frequency hopping signal, fixed frequency signals and Gaussian white noise signal. A large number of simulation results show that compared with traditional detection scheme, this algorithm is more robust and has less computational overhead, which is very important in practical engineering.Finally, the traditional hopping signal parameter estimation method based on time-frequency analysis, usually adopt fixed window function, resulting in restrictions on the frequency hopping of received signal, for this defect, we design an adaptive time-frequency analysis window function. By using adaptive window structure,according to different frequency hopping signal, the system estimates the width of window function at first. In addition, through the processing of time-frequency matrix, realized the estimate of frequency hopping parameters, and discussed in this paper to optimize its performance. Through simulation by MATLAB, analyzes the two kinds of time-frequency analysis method's strengths and weaknesses in parameter estimation of frequency hopping signals.