Implementation of inkjet-printed 3 dB coupler with equal power division and 45° output phase difference

Abstract

Implementation of a 3 dB coupler with flexible phase difference was presented in this paper. The coupler has equal power division and output phase difference of 45° as against the conventional coupler. It has advantage in many applications that require phase delay like phased antenna array, and beamforming network without necessarily requiring additional phase shifters. It was designed and implemented using the instant inkjet printing technique on a transparent Polyethylene terephthalate (PET) substrate specially coated with resin. The coupler's response shows very good return loss and isolation of −28 and −48 dB, respectively. A bandwidth of 31.33% was achieved around the center frequency. However, an output phase difference of 45° was recorded with a slight phase variation of about ±1° within the specified bandwidth