基于时空调制(STM)的单端环行器因其输入信号和调制信号的混合, 在接近所需频带处将受到互调产物(IMP)的影响, 这些IMP不仅会对相邻通道造成干扰, 还会限制调制参数。差分环行器通过匹配两个单端环行器, 以180°相位差的调制信号分别调制两个单端环行器, 从而消除IMP, 有效地改善了环行器的插入损耗、带宽及功率容量等指标, 提高了环行器的性能, 并降低了对调制信号的要求。该文描述了差分环行器的基本原理, 对差分环行器的电路结构、调制方式及测试方法进行了总结。对比分析表明, 差分体声波(BAW)环行器在插入损耗、隔离度及功耗等方面表现出优异的性能, 有望取代大多数商业系统中的铁氧体环行器。

The single ended circulator based on the spatiotemporal modulation(STM) will be affected by the intermodulation products(IMP) very close to the required frequency band due to the mixing between RF input and modulation signal. These intermodulation products will not only cause interference to adjacent channels, but also limit the modulation parameters. By matching two single ended circulators, the single ended circulators in the differential circulator are modulated respectively with the modulation signal of 180° phase difference, which can eliminate the IMP, so as to effectively improve the insertion loss, bandwidth and power handling of circulator, improve the performance of circulator, and significantly relax the requirement of the modulation frequency. This paper describes the basic principle of differential circulator, summarizes its circuit structure, modulation and test methods. The comparative analysis shows that BAW differential circulator exhibits excellent performance in insertion loss, isolation and power consumption, and is expected to replace ferrite circulators in most commercial systems.