Compact dual-band stubless branch-line coupler

Abstract

The implementation of microstrip nonuniform transmission lines (MNTLs) for dual-band branch-line coupler design is presented in this study. The proposed structure demonstrates dual-band performance, low insertion loss, and compact size in comparison with other prior proposed dual-band branch-line couplers. The current work fabricates an experimental dual-band branch-line couplers working at 0.9/1.8 GHz. Employing the stubless branches also leads to circuit miniaturization and achieves an overall size reduction up to 64.4%, compared with conventional stub tapped dual-band couplers. Also, stubless dual-band operation of the coupler causes the same phase relation between the two output signals at the two frequency bands. The measured results validate good dual-band performance.