W‐band microstrip band‐pass filter using branch‐line coupler with open stubs

Abstract

This article presents the design and measurement of a microstrip band‐pass filter (BPF) using modified branch‐line coupler with asymmetric open‐circuit stubs in the W‐band frequency range. The fundamental topology consists of using the branch‐line coupler as a filtering section by loading the coupled ports with suitable lengths of open‐circuit stubs. Therefore, transmission responses with simultaneously good stopband and sharp cutoff slope are derived, while the passband bandwidth can be easily controlled by means of the design parameters of the filtering section. The proposed BPF structure has been designed and fabricated on GaAs substrate. The fabricated BPF shows a 3‐dB bandwidth from 81 to 107 GHz with insertion loss <2 dB at center frequency, rejection of 51 dB, and return loss better than 18 dB. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1436–1439, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25185

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