%0 Journal Article
%T Directional Coupler with Good Restraint Outside the Passband and its Frequency-Agile Application
%A Yu Jian Cheng
%A Lei Wang
%A Jie Wu
%A Yong Fan
%J PIER
%@ 1070-4698
%D 2013
%I 
%R 10.2528/PIER12121009
%X In this paper, a directional coupler incorporating the bandpass frequency response characteristic is proposed and characterized. This structure is modified from a conventional branch-line coupler. Two wide open-ended coupled lines are used instead of microstrip branch lines. As such, good restraint performance outside the passband can be achieved. The even-odd mode technique is employed to analyze and synthesize such a coupler. After that, frequency tuning is achieved by modifying the electrical length of the open-ended coupled lines with varactors. Measured results validate the correctness of our theory and design.
%U http://www.jpier.org/pier/pier.php?paper=12121009