Dual-Band Branch-Line Couplers With Short/Open-Ended Stubs

Abstract

Two dual-band branch line couplers with arbitrary power division are proposed in this brief. By adopting half-wavelength open/short-ended stubs in improved couplers, the dual-band operations could effectively be implemented while ensuring a compact size. Furthermore, the frequency is tunable by changing the characteristic impedance of the transmission line. For practical verification, two branch line coupler ( ${\varepsilon }_{r} = 2.65$ , ${h}= 0.5$ mm) operating at 0.9/1.8GHz and 0.9/1.57GHz are constructed in microstrip technology and tested. The measured results are in good agreement with the simulated ones.