A tunable dual‐band branch line coupler based on composite right/left‐handed transmission lines

This article demonstrates a frequency-tunable dual-band branch line coupler based on composite right/left-handed transmission lines.A simple, yet effective conversion enables to design such transmission lines in a form that can be frequency tuned. A tuning function is realized with varactors. For demonstration, a dual-band branch line coupler at 0.6 and 1.2 GHz is fabricated. Tuning ranges of 51.4 and 18.0% are measured in the lower and upper band, respectively, in which |S21/S31| ≤ ±0.5 dB is obtained, when maintaining S11 below −10 dB. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1955–1958, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25373