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

In this paper, a 3 dB 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 = 0.9 GHz, the fabricated coupler achieves 15 dB return loss bandwidth of 44.4% with a size reduction of 76.3%. The designed coupler has insertion loss better than 3.6 dB with a magnitude balance of 0 ± 1 dB over the frequency band 0.67–1.05 GHz. In addition to compact design, the unwanted harmonics are well suppressed up to 4f0 with a level better than 20 dB by maintaining good agreement between the measured results and theoretical predictions.