Using Open Stubs and Tuning the Width of Output Microstrip Lines of a Balun Diplexer to Obtain the Matching Output Impendence With Rf Output Transceiver

Abstract

Abstract-Two novel compact 2.6/5.2 GHz diplexers with high common-mode suppression are designed and fabricated on an FR4 substrate. The diplexers are based on two open-loop rectangle-ring (OLRR) resonators, and two different resonant frequencies are easily obtained by tuning the lengths of the OLRR resonators. In the past, the traditional balun diplexer needed a matching circuit to achieve low loss when transferring a signal to a radio frequency (RF) transceiver, because of unmatched impedances between them. To improve efficiency and lower the cost of circuit fabrication, we propose a novel method for tuning the output impedance of the balun diplexer so that it matches that of the RF transceiver. The resulting balun diplexer has two stub-loaded microstrip lines; the required output impedance can be tuned by changing the widths of the microstrip lines and stubs and adjusting the stubs' length and position. If the output impedance is well tuned, this balun diplexer is more efficient and less costly because a matching circuit is unnecessary.