A novel compact branch-line coupler using four coupled transmission lines

A compact branch line coupler (BLC) using four coupled transmission lines is introduced. The loaded part of the proposed model has a same performance with a cascade two unit elements and it is equaled by a quarter wavelength line. The quarter wavelength lines of each branch in the conventional coupler are replaced by an equivalent circuit composed of a four coupled transmission line and two transmission lines. A compact branch‐line coupler (BLC) is designed, analyzed, and tested using this technique. The size reduction is about 65% with comparable performance. The measurement results are in good agreement with the theoretical ones. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1712–1714, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23460