Analysis of tem three‐section symmetrical directional couplers with tandem‐connected center section

Abstract

ABSTRACTThe analysis of TEM three‐section symmetrical directional couplers with tightly coupled section realized as a tandem connection of two coupled‐line sections has been shown. The design equations allowing for calculating the required even‐mode characteristic impedances of coupled‐line sections for arbitrarily chosen coupling coefficient and coupling ripple have been derived. The proposed method has been utilized for analysis of three‐section 3‐dB symmetrical couplers with different coupling ripple and the results are given in a tabular form. The theoretical analysis has been confirmed by measurements of a 3‐dB three‐section symmetrical coupler, in which coupled‐line sections constituting a tightly coupled section have been miniaturized to for better fitting to the coupler's structure. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2578–2582, 2013