【作者】 倪菁；

【导师】 刘中； 黄银和；

【作者基本信息】 南京理工大学 ， 电子与通信工程， 2008， 硕士

【摘要】 天波超视距雷达(OTHR)工作在高频段,利用电离层的反射实现远距离探测。该雷达具有探测距离远、能有效对付反辐射导弹、超低空突防、隐身攻击武器和电子干扰等当前雷达面临的主要威胁的突出优点,在我国现代防空领域具有非常重要的地位,填补了我国远程预警手段的空白。天波超视距雷达频段拥挤,回波中包括了各种有源干扰、无源干扰、外部噪声等,检测背景复杂;由于受到电离层时变因素的影响,杂波展宽严重。在这种复杂的环境下,实现雷达目标的有效检测是天波超视距雷达的重要研究内容之一。天波超视距雷达观测的目标分为空中目标和海面目标两大类,本文主要研究空中目标的检测方法。本文主要介绍了天波超视距雷达工作环境的特点和信号处理的主要任务;对回波信号经过信号处理的过程进行了分析推导,说明了信号处理是距离/方位/速度的三维联合信号处理;对天波超视距雷达回波中目标、干扰、杂波特性进行了研究,大量实录数据统计分析表明,目标、干扰、杂波共同构成了天波超视距雷达的检测背景,该背景是一种非平稳的复杂背景;对经典的两种CFAR检测器进行了阐述,比较了CA-CFAR和OS-CFAR的性能,并提出了这两种CFAR检测器在天波超视距雷达应用中存在的问题;从实际数据出发,针对经典CFAR检测器在天波超视距雷达应用中的不足,根据目标、干扰、杂波特性的不同,提出了目标检测方案,目前检测方案中首先采取了抗干扰的措施解决干扰剩余的问题,使得杂波背景尽量均匀、同态;然后采用经典的CFAR检测器进行恒虚警检测;由于杂波背景和CFAR检测器的背景不一致,虚警目标形成的点迹较多,最后还对点迹进行滤波等后续处理以降低虚警率。此外,根据天波超视距雷达的目标特性,如起伏性等,还有针对性地采取了关联检测方法来提高目标的检测概率。最后对全文进行了总结,对目标检测下阶段的工作进行了展望。本文研究结果通过实测数据验证,证明是有效的,已应用到天波超视距雷达中。更多还原

【Abstract】 Sky-wave Over-the-horizon radar (OTHR) works at high frequency band and can achieve long range detection via refraction by the ionosphere. It is significantly characterized by capabilities of detecting targets at long distance, resisting anti-radiation missile and stealth aircraft, and countering electronic jam, which badly threat conventional radars at present. Sky-wave OTHR plays an important role in the field of modern aerial defense and consequently fills the vacancy of strategic early warning of our country.OTHR works at a hostile electromagnetic environment and its echoes are confronted with all kinds of interferences from man-made and natural sources, and external noise, so it has a complicated background when detects targets. Besides, time-varying ionosphere will lead to serious clutter spectrum spread. All of the above makes target detection a key technique in OTHR signal processing. OTHR targets can be classified into two kinds, i.e. air targets and ship targets. This thesis aimed at air target detection with sky-wave OTHR.The thesis was organized as follows: introduced the features of sky-wave OTHR environment and the main task of corresponding signal processing; signal processing flow at sky-wave OTHR was introduced and techniques involved were analyzed and deduced, especially the range-azimuth-speed joint processing; Analysis of target signature, interference feature and clutter characteristics was centralized. Statistics of much data recorded with sky-wave OTHR showed that, target, interference and clutter consisted of nonstationary signal detection background; Two kinds of classical CFAR detectors were illustrated. The performance of CA-CFAR and OS-CFAR was compared, and both of their deficiencies appearing in the application to real radar data were analyzed; Based on the preceding detectors performance comparison and real echo analysis, It presented a new target detection scheme. Firstly, interference-suppressing measure was taken in the scheme to remove interference remains to keep background stationary and homogeneous. Secondly, CFAR based classical detector was adopted. The last step was false alarm filtering. Due to the inconsistency of real background with CFAR model, false alarm is possibly higher than expected. False target filtering technique was developed to discriminate false targets among all the detected. Furthermore, CFAR-based correlative detection method was advanced for fluctuant target to promote probability of detection, which had fluctuating SNR during sky-wave radar’s scanning time. At last, the thesis summarized the whole thesis and pointed out future work remained to study further.The techniques provided in this thesis has been proved by sky-wave OTHR data to be effective and applied in engineering practice.更多还原