一种新型高隔离四端口双工器设计

A novel design of 4-port diplexer with high isolation

设计了一款基于微带线的高隔离的新型四端口双工器,由两组中心频率不同的滤波器构成,每一组滤波器包括相位分别为±90°的两个滤波器.相对于传统的三端口双工器,得益于该双工器的新型四端口电路拓扑,使得泄露信号经过两路传输后形成相位相差180°的信号,最终相互抵消,进而达到提高隔离度的目的.另外,本设计所需要的180°移相由滤波器本身结构实现,不需要额外的移相电路,因而使得电路更加简单紧凑.为验证方法的有效性,设计了一款工作在1.8GHz和2.1GHz的四端口双工器并进行了加工,通过对双工器实物的测量,在1.8GHz和2.1GHz的隔离度分别达到了50.9dB和43.5dB,相对于传统三端口双工器分别提高了9.7dB和12.8dB,显著提升了双工器的隔离度.

A high isolated 4-port diplexer based on microstrip line is presented in this paper.The diplexer is composed of two pairs of filters operating different frequency,each pair include 2 filters with phase of 90° and-90°.The diplexer can achieve an isolation enhancement compared with some reported 3-port diplexers,resulting from the 4-port circuit topology and difference of phase 180° suppresses the leakage between the two channels.The filter of proposed 4-port diplexer is based on half-wavelength open-loop resonator structure,which enables the inverter without incurring any extra circuit footprint.For validation,the diplexer with operating frequencies of 1.8 GHz and 2.1 GHz is designed,fabricated and measured.The experimental results show that the 4-port diplexer has good in-band performance and high isolation of 50.9 dB and 43.5 dB.Compared to the traditional 3-port diplexer,the 4-port diplexer increased by 9.7 dB and 12.8 dB respectively,which indicates that the novel diplexer increased the isolation significantly.