C频段收发前端高隔离环形器设计与实现技术

Design and Realization Technology of High Isolation Circulator in Microwave Transceiver

介绍了微位移测量系统微波收发信道微波前端高隔离环形器的具体设计方法、实现形式以及测试结果。微位移收发信道是同频、同时、同天线的工作体制，所以发射信号会通过环形器泄露到接收信道中，造成接收通道饱和，接收信道对有用信号的信噪比，影响最后的系统测量精度；或者使得整个系统的测量距离很小，无法实际工程应用。为了在接收信道中将发射信号通过环形器泄露到接收信道中的信号进行抑制，采用的方法是在发射信道末端通过耦合器耦合一定信号能量，并使耦合信号进过可调衰减器和移相器对其幅度和相位进行调整，使耦合信号与泄露信号的幅度相等、相位相差180°，从而达到对环形器泄露信号的抑制抵消。该高隔离环形器指标要求工作频段是5750～5850MHz，发射端输出电平高于30dBm，接收端口对发射端口隔离度110dB（最大），稳态大于88dB，噪声系数小于3．5dB。

The design and realization of high isolation Circulator in microwave transceiver is presen- ted. In a micro displacement measuring system which adopts co-frequency co-time and co-antenna config- uration, the measuring accuracy usually will be aggravated by the leakage from the transmitter to the re- ceiver, which could be larger than the reflecting signal and lead to an overdrive to the receiver channel and a worse C/N ratio. In this case, the measure precision will be affected or the micro displacement measuring system cannot come true for small measuring distance. To reduce the leakage, a certain level RF signals obtained through a coupler at the transmitter and then adaptive processed by a attenuator and a phase shifter, so the high leakage suppression can be realized by the offset between the reflect signal from the antenna and the coupling signal which have been adjusted to the adaptive condition. The circula- tor works at the frequency of 5 750 ~ 5 850 MHz, the leakage suppression could be 110 dB （ maxim）, better than 88 dB （steady state） and a noise factor less than 3.5 dB.