Broadband Equal-Split Directional Couplers Composed of Cascade- and Tandem-Connected Coupled-Line Sections Having Unequal Lengths

Kinga Gawel,Slawomir Gruszczynski,Robert Smolarz,Kamil Staszek,Magda Kalawska,Krzysztof Wincza

doi:10.1109/access.2021.3106901

Kinga Gawel, Slawomir Gruszczynski + Show 4 more

Open Access

https://doi.org/10.1109/access.2021.3106901

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Abstract

A new concept of broadband equal-split coupled-line directional couplers is proposed. The proposed couplers are based on coupled-line sections, all having the same coupling coefficient, and feature frequency characteristics similar to the ones obtained for classic symmetrical three-section coupled-line couplers. It is shown that appropriate cascade- and tandem-connected coupled-line sections, having all the same coupling coefficients and different electrical lengths allow for achieving equal power split in a broadband frequency range together with the quadrature differential phase response. Therefore, a very flexible design process is possible, in which directional couplers with different bandwidths and coupling imbalances can be realized by changing solely the electrical lengths of the coupled-line sections. Moreover, the proposed networks require significantly lower coupling coefficients and feature slightly shorter overall electrical lengths than their classic counterparts. The theoretical analysis of the proposed circuits is shown in the paper and is followed by the design and measurements of two broadband equal-split quadrature directional couplers operating at the center frequency of 2 GHz.

Highlights

Quadrature directional couplers as well-known and often utilized components in contemporary microwave electronics, feature equal-power split between coupled and direct ports and simultaneously they present additional 90◦ phase shift of the signal delivered to direct port with respect to the signal delivered to the coupled port
We present a new circuit solution to the design of equal-split directional couplers featuring frequency characteristics similar to the ones obtained for classic quadrature three-section directional couplers
Since the developed couplers feature the properties of three-section symmetrical directional couplers, the achieved properties have been comparted to other published solutions that allow for the design of directional couplers having equal-ripple coupling characteristics over a broad bandwidth i.e.; classic symmetrical directional couplers [16], classic symmetrical tandem couplers [25], couplers with tandem-connected center section [27], and tandem couplers composed of coupled-line sections having unequal lengths [35]

Summary

Introduction

Quadrature directional couplers as well-known and often utilized components in contemporary microwave electronics, feature equal-power split between coupled and direct ports and simultaneously they present additional 90◦ phase shift (delay) of the signal delivered to direct port with respect to the signal delivered to the coupled port. We present a new circuit solution to the design of equal-split directional couplers featuring frequency characteristics similar to the ones obtained for classic quadrature three-section directional couplers.

Results

Conclusion