A Compact Millimeter-Wave Phase Shifter Integrated Variable Coupler in SIW Technology for Beam-Forming Applications

This work presents an innovative, compact phase shifter integrated variable coupler in substrate-integrated waveguide (SIW) technology for millimeter-wave beam-forming applications. The phase-shifting mechanism leverages rectangular slots on the top and bottom walls of the SIW, enabling a precise and tunable phase shift of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 60^{\circ}$</tex>. This phase shifter is functionally embedded into a cruciform directional coupler to realize variable coupling with arbitrary phase shift, combining functionality in a single, unified component. To validate this concept, seven prototypes are fabricated, each operating at a center frequency of 37 GHz, and offering variable coupling and phase-shift configurations (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{3} \mathbf{d B}, \mathbf{1} \mathbf{d B}, \mathbf{5} \mathbf{d B}, \pm 60^{\circ}$</tex>, and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 30^{\circ}$</tex>). Characterization of these prototypes confirms the effectiveness and flexibility of the design, marking a significant advancement in compact, multi-functional millimeter-wave components. The proposed integrated design functions as a single component, ideal for advanced beam-forming networks, including Generalized Joined Coupler Matrix (GJC) architectures.