Research On Distance-cover Characteristic Of Phase-code Signal For HF Radar

The single base high-frequency ground wave OTH radar can not transmit andreceive signals at the same time, when using the phase-coded signal, thephase-encoded signals are often higher requirements on the duty cycle, this willinevitably results in distance-cover phenomenon that the echo signals from far ornear will be received incompletely. When the target is in the eclipsed region, somecodes are missing due to the fact that part of the phase-encoded signal is covered. Inrelevant handling of pulse compression, since the matched filter is designed by thefull codes, so once the echo is covered, the characteristics of pulse compression willdeteriorate and the range side-lobes will increase which will seriously affect theanalysis of target information, so it is very important to discuss the problem ofdistance-cover in the phase-encoded signal.For the phase-encoded radar signals, it is very important to choose codes withgood autocorrelation properties. Because the complementary code signal has thecharacteristics of zero side-lobe，it has obvious advantages for radar detection of fartarget. The main contents of this paper is based on complementary binary code，firstly，design the radar signal according to the system parameters, then analyze thecharacteristics of distance-cover in different covering length, finally, focuses onstudying different ways to solve the problem.In this paper, it solves the problem of phase-encoded signal’s distance-covermainly in three ways: signal processing segment, signal design, side-lobesuppression. Subsection processing mainly uses complementary code with thecharacteristics of sub-complementary to divide the signal into segments according todistance delay, then conducts pulse compression in segment. Signal design mainlystart from the combination and improvement of different signal coding methods,combined with short code and long code in pulses and improved the complementarycode using the improved algorithms for golay code. For the close area echoes wecan effectively avoid covering by short code, for the type of code improvementmainly in order to find some codes which have excellent part of relatedcharacteristics. In sidelobe suppression, first try to use the conventional sidelobesuppression methods of phase code to suppress side-lobe, the result is not satisfiedenough. In that case,based on the pulse compression characteristic of coveredcomplementary code,a absolute value based sidelobe suppression method isproposed and in the meanwhile, combination of the absolute value based sidelobesuppression method and the code word originating from improved Golay codealgorithm is introduced to solve the distance covering problem,with the sidelobe in the covering condition finally the paper uses the improved RMMSE algorithmprocessing to suppress the side-lobe caused by distance-cover through adaptiveiteration，the side-lobe suppression effect is relatively satisfied.