A Millimeter-Wave Antenna Array With Tunable Element Coupling for Enhanced Scan Capabilities

Phased array systems have become an integral part of many communication and sensor applications. Despite advancements in suppressing scan blindness, existing methods lack adaptive features to enhance radiation efficiency for specific frequency-angle pairs. In this article, a dual-polarized stacked patch antenna with a novel electronically tunable coupling circuit is introduced, enabling adaptive control of the coupling mechanism between adjacent unit cells. An infinity array simulation demonstrates the advantages of integrating varactor diodes into the coupling circuit, enhancing the radiation efficiency for discrete frequency-angle pairs. Furthermore, additional degree of design freedom is achieved through the adaptive control of the coupling mechanism of adjacent unit cells. An $11\times 11$ demonstrator antenna is realized to validate the full-wave simulation results. The measurement results are in good agreement with the simulations. Through far-field measurements the impact of the electronically tunable coupling circuit is demonstrated, enhancing the scan efficiency at frequencies of 27.5 GHz and 31.5 GHz. For both principal planes at 27.5 GHz, a measured gain improvement of at least 2 dB is achieved, while in the E-plane at 31.5 GHz, the onset of a scan degradation within the range of $\pm {\mathrm {60~ {^{\circ}}}}$ can be mitigated.