An Ultra-Compact Full-Band Waveguide Quadrature Hybrid Coupler

Tomas Fernandez,Luca Perregrini,Angel Mediavilla,Gabriele Ceccato,Juan Luis Cano

doi:10.1109/lmwc.2021.3116103

Tomas Fernandez, Luca Perregrini + Show 3 more

Open Access

https://doi.org/10.1109/lmwc.2021.3116103

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Abstract

This work proposes an easily scalable quadrature hybrid coupler (QHC) topology with two symmetric stepped apertures that originate a square coaxial-like mid-section. This new configuration enables an ultra-compact design, three times shorter than equivalent structures, having 40% of fractional bandwidth with 25 dB of matching/isolation and 1 dB of axial ratio (AR). The impedance transformers can be easily redesigned to meet other requirements related to electrical performance or even other desired coupling values. For verification purposes, a prototype at <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ku</i> -band was manufactured and measured showing good agreement with simulation results.

Highlights

D IRECTIONAL couplers are one of the basic microwave circuits that require periodic attention since their capabilities of power division/combination or power sampling need to face more and more stringent requirements from new applications
Waveguide hardware is bulky in nature, there is a growing interest in the design of ultra-compact structures with full-band performance that can be implemented in, for example, Butler matrices, multi-beam communication networks, or multi-pixel radio astronomy receivers [1], [2]
This is a very suitable parameter to characterize the performance of quadrature hybrid coupler (QHC)

Summary

INTRODUCTION

D IRECTIONAL couplers are one of the basic microwave circuits that require periodic attention since their capabilities of power division/combination or power sampling need to face more and more stringent requirements from new applications. The AR is a figure of merit that gathers the amplitude and phase imbalances with respect to equal magnitude and 90◦ out of phase signals [5] This is a very suitable parameter to characterize the performance of QHCs. When aiming at waveguide fullband coverage, 40% fractional bandwidth, and good electrical performances, E-plane structures offer more flexibility. In [13], the use of three apertures arranged in two different levels for the design of a 10 dB coupler achieves a 44% of bandwidth in a very compact configuration It requires a number of matching fins and posts that increase the complexity at the design and manufacturing stages. To overcome the above drawbacks, this work proposes a new QHC architecture, close to [12], with two symmetric stepped apertures that originate a square coaxiallike mid-section (see Fig. 1) This configuration enables an ultra-compact design and broader bandwidth configuration. The thickness of the internal coaxial-like section is thick enough to allow an easy mechanical migration toward higher frequencies

COMPACT HYBRID COUPLER WITH COAXIAL SECTION

Field Analysis of the Coaxial-Like Section

DISCUSSION

MANUFACTURING AND MEASUREMENT RESULTS

Findings

CONCLUSION