Research On De-hopping Technique Of Short Wave Frequency-hopping Signal

In frequency-hopping(FH) communication system,the carrier frequency controlled by a sequence of pseudo random codes (PN codes) is continuously changing with complex pattern. The characteristics of better security and anti-interfere lead the frequency-hopping communication technique to a wide military application .So it is significant to search after a method for the interception of FH signal.The de-hopping of carrier frequency is a key step in FH signal interception. Since the FH pattern of the intercepted FH radio can not be known in advance, so the method of PN codes synchronization can not be used here for de-hopping and interception.Generally, the short-wave FH signal is with a relatively low hopping rate and long frequence change time, and there maybe channeloverlap between different FH points.Aimed at these characteristics,the realization of the de-hopping technique for short-wave FH signal is analyzed.Based on the system of digital FFTreceiver,a "Time delay guiding" de-hopping method is introduced. Some key points of this method is discussed in the paper such as:data sampling and design of ADC,mass storage facility (MSF) organization,identification and pattern patchwork of FH signal, and digital down conversion technique. Theoretical analysis and simulation are made for the above-mentioned key techniques, special experiment is also conducted.The simulation results are given at the end of the paper. The feasibility of the method is proved by simulation.