基于交指滤波器的高隔离度宽带双工器设计

Design of interdigital-filter based diplexer with high isolation and wideband

针对用于无线通信系统中的高隔离度宽带双工器,首先将双工器指标拆分为留有一定余量的Tx,Rx滤波器指标,然后使用微带交指结构和基于耦合系数与外部品质因数的改进方法,设计出满足指标的宽带Tx,Rx滤波器,最后使用两种T型结和滤波器组合的结构对双工器进一步设计,并对这两种结构的微带双工器进行了仿真分析。仿真结果显示,并行连接的双工器结构紧凑,但隔离度较差;串行连接的双工器通带内最小回波损耗为14.16dB,最大插入损耗为1.01dB,通带间最小隔离度为53.46dB,双工器尺寸为8.0899mm×2.0591mm×0.302mm,完全满足指标要求,并且具有相对带宽大、隔离度高、插入损耗低的优点,为设计高性能双工器提供了可行性。

For diplexer with high isolation and wideband in wireless communication system, in this paper, the diplexer specification is divided into Tx and Rx filter specifications with a certain margin. Then the wideband Tx and Rx filter is designed by using the microstrip interdigital structure and the improved method based on coupling coefficient K and external quality factor Q e. Finally, two kinds of T-junction and filter combination structures are used to further design the diplexer, and the microstrip diplexer with these two structures are simulated and analyzed respectively. The simulation results show that the structure of parallel connection diplexer is compact, but the passband isolation is not satisfactory. The minimum return loss in the passband of the series connection diplexer is 14.16 dB, the maximum insertion loss is 1.01 dB, the minimum passband isolation is 53.46 dB, and the size of the diplexer is 8.089 9 mm×2.059 1 mm×0.302 mm. It has the advantages of large relative bandwidth, high isolation and low insertion loss, which provides the feasibility for the design of high-performance diplexer.