Four-Port Dual-Mode Diplexer with High Signal Isolation

Jessada Konpang,Natchayathorn Wattikornsirikul

doi:10.1155/2020/4032673

Abstract

An ease of four-port dual-mode diplexer with high signal isolation is presented. A compact dual-mode diplexer with high signal isolation between the Rx and Tx modules is achievable by only using one resonator filter topology. Two back-to-back dual-mode diplexers have a 180° phase shift in one branch. The high isolation can be achieved by amplitude and phase cancellation technique. The delayed transmission line can be easily achieved by the phase shifter. The simulated and measured four-port dual-mode diplexers are designed at the centre frequency of Rx/Tx at 1.95 GHz and 2.14 GHz, respectively. The measured results of Rx/Tx dual-mode diplexer devices are presented with 47.1 dB Rx/Tx isolation. This four-port dual-mode diplexer achieves the isolation (S32) of more than 24.1 dB when compared with the conventional three-port dual-mode diplexer structure.

Highlights

In RF front-ends of several communication systems, a diplexer is usually used to discriminate two different signal frequency bands for transmitting (Tx) and receiving (Rx) channels while sharing a single antenna
Filters and diplexer are recently required to design with compact size, light weight, and high signal isolation
To keep small circuit size and light weight, common microstrip resonators are employed for filters and diplexer design. e microstrip open-loop resonator filters are highly desirable in the wireless communication systems with compactness and high performance [2]

Summary

Introduction

In RF front-ends of several communication systems, a diplexer is usually used to discriminate two different signal frequency bands for transmitting (Tx) and receiving (Rx) channels while sharing a single antenna. Filters and diplexer are recently required to design with compact size, light weight, and high signal isolation. To keep small circuit size and light weight, common microstrip resonators are employed for filters and diplexer design. High signal isolation between Tx/Rx ports can be increased by using an ease of structure design; many research papers have been made to increase the signal isolation in diplexers. An alternative technique to design diplexer with low cost, high signal isolation, and ease of fabrication process was introduced by using four-port network [12, 13]. E technique for size reduction and high isolation signal by using a dual-mode resonator filter and diplexer is presented in [14, 15]. E dual-mode structure by using U-shaped resonator with open stub enables a compact and ease of design. In order to cancel the same amplitude signal but different phase in transmitter and receiver, a delayed microstrip transmission line can be used to achieve a 180° phase shift in one branch

Tx filter Tx filter

Conclusions