A novel two section branch line coupler employing different transmission line techniques

Abstract

In this paper, a 3dB wideband branch line coupler with reduced size and harmonic suppression is presented. New multiple asymmetric π-shaped, cross and T-shaped transmission line techniques are used to reduce the physical size of the coupler. At the operating frequency of f0=0.9GHz, the fabricated coupler achieves 15dB return loss bandwidth of 44.4% with a size reduction of 76.3%. The designed coupler has insertion loss better than 3.6dB with a magnitude balance of 0±1dB over the frequency band 0.67–1.05GHz. In addition to compact design, the unwanted harmonics are well suppressed up to 4f0 with a level better than 20dB by maintaining good agreement between the measured results and theoretical predictions.