The Ionospheric Effects On The High Frequency Skywave Radar And The Correction Methods

HF Skywave radar exploits the refractive and multi-path nature of high frequency propagation through the ionosphere to achieve wide-area surveillance, which has those advantages, compared with the conventional radar, such as finding stealth aircrafts, low cost for construction and maintenance, a long detection range and wide coverage, the order of hour for early-warning time, and so on that it has attracted people's attention in recent years. However there are so many problems caused by the ionosphere channel that affecting its operation. Those problems mainly include frequency channel is very crowd in HF band; all kinds of interference are comparatively more; a temporal phase path variation broaden echo's spectrum which often severely degrades the target detection performance; Multi-layers structure and the time varied parameters of the ionosphere degrade the accuracy of the target location estimate. The adaptive ability to the ionospheric propagation channel is needed to improve the performance of the HF Skywave radar, so recognition and correction of distortion and contamination is a vital part of the radar.This thesis consists of two parts: Firstly, it presents the mechanisms that how the ionosphere channel influences the HF radio wave. Then it look into the principle and performance of several kinds of correction technique in signal processing. In the second part, this thesis focuses on the correction techniques exploiting ionosphere sounding mainly introducing a novel ionosode system, especially its design, development , results and applications in the correction for HF Skywave radar.The author's distribution includes:a) summarize the mechanism how ionosphere influent HF radio wave.b) Bring forward several improved methods on the basis of comparing performance of all kinds of correction techniques. Those methods include: the improved MUSIC-type algorithm to estimate slowly-changing phase path smearing function; the channel equalization in frequency dimension to estimate random-changing phase path smearing function.c) A simple but effective method processing in range dimension is elaborated for Radio Freqency interference.d) Design and realize the host program of the novel ionosode system, which has been proved to be successful in the vertical ionosphere soundinge) Put forward the potential application of the novel ionosode system in correcting the ionospheric distortion.