基于复合铁氧体基片的三倍频程超宽带微带环行器设计与仿真分析

Design and simulation of third octave bandwidth microstrip circulator based on composite ferrite substrate

通常利用单一铁氧体材料制成的微带环行器难以有超倍频程的带宽。根据一般微带环行器的设计理论,利用两种不同的铁氧体材料构成的复合基片设计并制作了一种工作在三倍频程带宽的超宽带微带环行器。仿真结果表明,该环行器在6~18 GHz的工作频带内,插入损耗(|S12|)小于1 d B,回波损耗(|S11|)大于20 d B,隔离度(|S21|)约19 d B,满足超宽带微带环行器的设计指标。除在整个工作频带内插入损耗有所增加且在低频段的6~6.5 GHz内出现了低场损耗外,实测结果与仿真结果基本吻合。文末讨论了实测结果和仿真结果之间出现低场损耗等差异的原因。

In general, microstrip circulators made from a single ferrite are difficult to attain bandwidth of octave coverage. In this paper, based on the general design theory of microstrip circulator, a ultra-wideband microstrip circulator operating at triple octave bandwidth had been designed and fabricated with a composite made up of two different ferrites. The simulation results indicate that, the circulator at frequency range from 6 GHz to 18 GHz features an insertion loss S12 less than 1dB, return loss S11 greater than 20 dB, and isolation S21 greater than 20 dB, meeting the design specifications of the ultra-wideband microstrip circulator. Although insertion loss increases slightly in the entire frequency band and a low-field loss appears at the low frequency range from 6 GHz to 6.5 GHz, the measured results are basically in agreement with the simulation results. At the end of this paper, the reasons for the differences like low-field loss between the measured results and the simulation results are discussed.