Wideband transmitarray with independent phase/amplitude control for millimeter-wave vehicular sensing and communication

This paper proposes an innovative multi-bit transmitarray (TA) designed for vehicular sensing applications at Ka-band, featuring 400 unit cells with independent adjustments in both phase and amplitude. The far-field beam-steering mechanism involves calculating phase compensation for each unit cell to redirect the beam toward the desired direction, coupled with a multi-bit amplitude distribution system to reduce side-lobe levels (SLL). A Genetic Algorithm (GA) optimization approach is employed to mitigate gain reduction during amplitude tapering, ensuring robust performance. Thus, the primary contribution of this study is the integration of multi-bit amplitude control with phase manipulation, which collectively enhance beam-steering accuracy and side-lobe suppression, providing a high-performance solution that outperforms traditional designs. Simulation results demonstrate two beam scanning techniques: a phase-only beam steering system with a maximum peak gain of 22.3 dBi and SLLs of −15.7 dB and −14.1 dB for the H- and E-planes, respectively, and an independent phase/amplitude mechanism at angles of 0° and 30°, yielding maximum measured peak gains of 27.2 dBi and 24.5 dBi, respectively. Moreover, the measured side-lobe levels and cross-polarization levels remain below −22.1/−19.4 dB and −44/−35.7 dB, for 0°; −16.3/−19.6 dB and −29.7/−29.05 dB for 30° in H-/E-planes, respectively, making the proposed TA a promising candidate for a high-gain and low SLL mm-Wave vehicular communication system.