单天线FMCW雷达射频收发前端高隔离技术研究

发布时间：2018-07-27 09:18

【摘要】：随着对雷达小型化、低重量要求越来越高,调频连续波(FMCW)雷达尤其是收发共用同一个天线的单基地雷达,在军用和民用上得到了越来越多地关注。然而CW单基地雷达系统设计面临着一个重大挑战,就是如何解决发射信号到接收机的泄露问题。解决这一问题,可使FMCW雷达作用距离更远,从而可使它的应用更加广泛。基于这种需求背景,关于提高连续波雷达收发隔离的相关技术研究在本文中得以开展。首先,调研了现有的高隔离技术,包括双天线空间隔离、环行器隔离以及各种对消技术;并从理论上阐述对消技术的工作原理。在此基础上,本文提出了将高隔离度环行器与数字闭环控制射频对消技术相结合的方案,可极大提高收发机之间的隔离度。其中误差检测电路采用外差结构,它的优点是,相比传统的模拟对消技术,可解决其中模拟混频器后存在的直流漂移问题。而且采用数字闭环控制,可实现更准确更灵活地对消控制。为了验证该方案的可行性,在X波段上设计了一个对消系统样机。首先根据系统设计要求,介绍了系统方案整个制定过程;并对系统按功能模块进行详细描述,还对关键性能进行分析。接着,详细地描述了微波前端相关电路及腔体设计过程,这是本文的主要工作内容之一。按照射频对消模块设计(包括馈通对消电路设计和误差检测电路设计)、发射机功放电路设计、电源板设计、以及腔体设计几个部分来展开说明。其中详细说明了关键器件选型,无源微波器件设计,电路图绘制,以及腔体结构优化。最后,详细介绍了系统中微波电路的测量调试。先进行单独模块测试,再组装联合起来进行测试。还分析了电路组装测试出现的问题,并给出了解决方法。最终微波前端的联合测试结果表明,在600MHz带宽内,射频对消部分可达到30dB以上的对消度;加上环行器的隔离度,整个系统对发射泄露信号的抑制度可以达到70dB以上,达到预定要求。最后总结了全文的工作成果,并对后续工作进行展望,提出需要改进的地方。
[Abstract]:With the miniaturization of radar and the increasing requirement of low weight, FM CW (FMCW) radar, especially mono-static radar with the same antenna, has been paid more and more attention in both military and civilian fields. However, the design of CW mono-static radar system is faced with a major challenge, how to solve the problem of transmitting signal to receiver leakage. To solve this problem, FMCW radar can be used more widely. Based on this requirement, the research on improving the transceiver isolation of CW radar is carried out in this paper. Firstly, the existing high isolation technologies, including dual-antenna spatial isolation, circulator isolation and various cancellation techniques, are investigated, and the working principle of cancelling technology is described theoretically. On this basis, a scheme combining high isolation circulator with digital closed-loop control radio frequency cancellation technology is proposed, which can greatly improve the isolation between transceivers. The heterodyne structure is used in the error detection circuit. Compared with the traditional analog cancellation technique, the error detection circuit can solve the DC drift problem after analog mixer. Moreover, digital closed-loop control can realize more accurate and flexible cancellation control. In order to verify the feasibility of the scheme, a cancellation system prototype is designed on X band. Firstly, according to the requirements of the system design, the whole process of making the system scheme is introduced, and the system is described in detail according to the function module, and the key performance is analyzed. Then, the design process of microwave front-end circuit and cavity is described in detail, which is one of the main contents of this paper. The design of RF cancellation module (including feed-through cancellation circuit design and error detection circuit design), transmitter power amplifier circuit design, power supply board design, and cavity design are described. The selection of key devices, the design of passive microwave devices, the drawing of circuit diagram and the optimization of cavity structure are described in detail. Finally, the measurement and debugging of microwave circuit in the system are introduced in detail. A separate module is tested first, then assembled together to test. The problems in circuit assembly test are analyzed, and the solutions are given. Finally, the joint test results of the microwave front end show that in the 600MHz bandwidth, the radio frequency cancellation part can reach the cancellation degree above 30dB, plus the isolation degree of the circulator, the whole system can suppress the emission leakage signal more than 70dB. Meet the scheduled requirements. Finally, the paper summarizes the results of the work, looks forward to the follow-up work, and points out the need for improvement.
【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】：TN957

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