Coupled-line coupler with controllable bandwidth

Abstract

A new approach for designing a parallel coupled-line coupler with controllable bandwidth is presented. The proposed circuit consists of one coupled-line section and four open- or short-circuited stubs tapped at the ends of coupled lines. The adjustable range of fractional bandwidth is from 7% to 45% controlled by adjusting the impedance of stubs. An experiment coupler operating at 2.5 GHz was fabricated for demonstration with a bandwidth of 17.6%.