Based On The Simulation Of Frequency Hopping Communication System Anti-jamming Technology Research

Frequency Hopping Spread Spectrum (FHSS) communications technology is widely used in the field of military communications because of its excellent properties of anti-jamming and anti-intercept. It has been the main means of modern military anti-jamming communications. With the increasing of interference means, continuous improvement and innovation are needed to be made to reinforce the performance of FHSS system.The carrier wave of FHSS system is controlled by pseudo random sequence to avoid interference. Therefore, the properties of Frequency Hopping (FH) sequence are directly related to anti-jamming performance of FHSS system. Design of FH sequence with good performance becomes a research hotspot. Additionally, jamming for FHSS system mainly affects the synchronization of FH pattern and the judgment of integral of demoded signal to degrade its performance. According to that, it’s the key to improve the performance of FHSS system that how to reject the jamming.This thesis mainly study the anti-jamming performance and suppression of non-network FHSS system under narrow-band jamming, multi-tone jamming and broad-band Gaussian noise interference. Firstly, all the modules involved in FHSS system are analyzed to elaborate their functions and effect for anti-jamming performance. For received FH signal copy, serial search method and delay-locked loop (DLL) are adopted to acquire and track the receipted FH signal respectively. Taking into account the long average search time of serial search technique, a method is utilized to remedy the defect. This method estimates the possible phase of FH sequence by FFT for a piece of samples to reduce the average search time. Secondly, the traditional dual-band method for design of wide-interval FH sequence is unable to use all FH slots. Improvement is made to utilize all the FH slots and analysis is made to show that the consequent sequence still meets the requirement of wide interval. Besides, consistent Hamming correlation properties and larger linear span are obtained by this processing. Lastly, a combining algorithm is presented to utilize the frequency diversity effect when MFSK is adopted by FHSS system and simulation results of it is compared with that of linear combining, self-normalized combining and ratio-statistic combining algorithm.The FHSS system receiver implemented by using MATLAB software is employed to test the anti-jamming performance under the previously mentioned three types of jamming. The simulation results show that estimation of the phase of FH sequence via FFT improves the probability of successfully capture and the presented ratio-clipping combining algorithm obtains better performance than the three mentioned combining algorithms under multi-tone jamming. The FHSS hardware-in-the-loop simulation system is constructed with general test instruments verifies the correctness of design of the FHSS receiver.