MINIATURIZED MICROSTRIP BRANCH-LINE COUPLER WITH GOOD HARMONIC SUPPRESSION PERFORMANCE

摘要

This paper presents a miniaturized microstrip branch-line coupler with good harmonic suppression performance.The proposed coupler consists of four branch-line sections,each of which is loaded by open-circuit stubs both at the center and the two ends.This type of loading can realize size reduction and harmonic suppression.As an example,a proposed branch-line coupler operating at 1.0 GHz is designed,fabricated and measured.The results show that the proposed branch-line coupler occupies 67％ size of a conventional one and has better than 20 dB suppression from 1.9 to 5.8 GHz.Furthermore,the high slop of the transition band ensures good selectivity of the coupler.