复杂环境中MIMO-OTH雷达的分集增益研究

发布时间：2018-02-25 19:24

本文关键词： 雷达 MIMO OTH 空间分集　出处：《电子科技大学》2014年硕士论文　论文类型：学位论文

【摘要】：多输入多输出(MIMO)系统利用空间分布的多个发射天线和多个接收天线获得空间分集增益,从而用来对抗信道衰弱。天波超视距(OTH)雷达利用电离层折射探测目标,具有超远距离目标探测和信息获取的能力,具有重大的战略意义,本文针对采用MIMO技术的OTH雷达(MIMO-OTH雷达),研究复杂环境中MIMO-OTH雷达目标检测的分集增益,分析雷达系统参数配置、多径传播等因素对MIMO-OTH雷达系统目标检测性能的影响。通过分析OTH雷达的工作模式和OTH雷达信号在电离层中的传播特点,构建同时具有MIMO雷达以及OTH雷达特性的MIMO-OTH雷达回波信号模型,该信号模型不仅体现雷达信号在复杂电离层环境中的传播特性,还能体现多径传播现象,在有加性复高斯白噪声和杂波的情况下,根据上述MIMO-OTH雷达回波信号模型,利用尼曼-皮尔逊(NP)准则得到高斯检测器。本文研究了NP准则下MIMO-OTH雷达最佳检测器的漏检概率,同时推导了MIMO-OTH雷达目标检测的分集增益,并以分集增益为评价指标分析了影响MIMO-OTH雷达检测性能的主要因素。雷达信号经过电离层传播后照射到目标,并在目标上反射后再次经过电离层传播回到雷达接收端,因此在本文所构建的信号模型中存在两次电离层传播和一次目标反射过程,其中电离层传播损耗系数和目标反射系数有可能是确定未知量或者复高斯随机变量,使得总的信道增益表现为复高斯、复双高斯或复三高斯等随机变量。本文将分别计算在复双高斯信道环境下和复三高斯信道环境下MIMO-OTH雷达目标检测的分集增益。对于一个由M个发射天线和N个接收天线所构成的MIMO-OTH雷达,若第m个发射天线发射的探测信号通过mQ条传播路径照射到目标,经目标反射后通过mnH条传播路径被第n个接收天线接收到,本文证明在复高斯或复三高斯信道环境中,雷达系统目标检测能够获得的最大分集增益d满足1 1min{, }N M n m mn md NM H Q= =￡ ? ? 。研究表明MIMO-OTH雷达目标检测的分集增益小于等于雷达收发端天线个数的乘积与总传播路径条数的最小值。增加天线个数或者多径条数均可以增大分集增益,有利于雷达提高检测性能,本文的分析不仅表明天波MIMO-OTH雷达较传统OTH雷达具有更好的检测性能,并且为合理设计MIMO-OTH雷达的系统参数以提高目标检测性能提供了理论参考。本文最后分别对两种复杂环境下MIMO-OTH雷达目标检测的进行数值仿真,展现了不同场景下MIMO-OTH雷达目标检测的漏检概率情况,同时分析对比了不同雷达参数、不同信道环境以及不同传播路径条数对雷达目标检测性能的影响。
[Abstract]:Multiple input and multiple output (Mimo) systems use spatially distributed multiple transmit antennas and multiple receiving antennas to gain spatial diversity gain to counter channel debility.Sky wave over-the-horizon OTHradar uses ionospheric refraction to detect targets. This paper studies the diversity gain of OTH radar and MIMO-OTH radar based on MIMO technology, and analyzes the configuration of radar system parameters. The effects of multipath propagation on the target detection performance of MIMO-OTH radar system are analyzed. The working mode of OTH radar and the propagation characteristics of OTH radar signal in the ionosphere are analyzed. The echo signal model of MIMO-OTH radar with the characteristics of MIMO radar and OTH radar is constructed. The signal model not only reflects the propagation characteristics of radar signal in complex ionospheric environment, but also reflects the phenomenon of multipath propagation. In the case of additive complex Gao Si white noise and clutter, according to the above mentioned MIMO-OTH radar echo signal model, we use the Niman-Pearson MIMO-OTH criterion to obtain the Gao Si detector. In this paper, we study the missed detection probability of the best MIMO-OTH radar detector under NP criterion. At the same time, the diversity gain of MIMO-OTH radar target detection is deduced, and the main factors affecting the detection performance of MIMO-OTH radar are analyzed with diversity gain as the evaluation index. The radar signal is irradiated to the target after ionospheric propagation. After reflection on the target, the ionosphere propagates back to the radar receiver again, so there are two ionospheric propagation and one target reflection process in the signal model constructed in this paper. Among them, the ionospheric propagation loss coefficient and the target reflection coefficient may be unknown variables or complex Gao Si random variables, so that the total channel gain is represented by complex Gao Si. In this paper, we calculate the diversity gain of MIMO-OTH radar target detection in the environment of complex double Gao Si channel and complex triple Gao Si channel, respectively. For a MIMO-OTH radar target detection by M transmitting antenna and N connection, we will calculate the diversity gain of target detection in the condition of complex double Gao Si or complex triple Gao Si, respectively. MIMO-OTH radar composed of receiving antenna, If the detection signal transmitted by the m transmitting antenna reaches the target through the mQ propagation path and is received by the nth receiving antenna by the mnH propagating path after the reflection of the target, it is proved in this paper that in the environment of the complex Gao Si or the complex triple Gao Si channel, The maximum diversity gain d obtained by radar system target detection satisfies 11 min {,} NM n m mn m m d NM H Q = =? ? It is shown that the diversity gain of MIMO-OTH radar target detection is less than the minimum value of the product of the number of antennas at the radar transceiver end and the number of total propagation path bars. Increasing the number of antennas or the number of multi-path bars can increase the diversity gain. The analysis of this paper not only shows that the sky-wave MIMO-OTH radar has better detection performance than the traditional OTH radar, It provides a theoretical reference for reasonably designing the system parameters of MIMO-OTH radar to improve the performance of target detection. Finally, numerical simulation of MIMO-OTH radar target detection in two complex environments is carried out. The missed detection probability of MIMO-OTH radar target detection in different scenes is presented. The effects of different radar parameters, different channel environment and different propagation path number on radar target detection performance are analyzed and compared.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN958

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