A Wideband True Time Delay Microstrip Line Five-Port Coupler with Double Ring Star Link

In this paper, a passive, matched, symmetrical five-port wideband coupler with true time delay (TTD) characteristic is presented. Unlike other five-port designs focusing on magnitude and phase balance, the proposed structure incorporates a compact delay equalizing element within a broadband microstrip ring-star core to achieve a constant TTD response, while preserving equal power division and ±120° phase relations. The theory analysis and simulation are carried out for the proposed design, and a simultaneous conductive and dielectric inks injecting 3D printing technique is applied to fabricate the proposed five-port coupler with TTD response. The experiment results align with simulation and theory, and it achieves the expected constant TTD behavior across the 4-8 GHz range. The proposed TTD five-port coupler can be applied for wideband beam-squint reduction phased array design.