Enable Continuous Beam Scanning for Joint Communication and Sensing Employing the Generalized Joined Coupler Matrix

Joint communication and radar/radio sensing (JCAS) is envisioned as a promising capability in various future vehicular platforms, such as smart cars. The generalized joined coupler (GJC) matrix is a promising candidate for JCAS, offering a compact design and the ability to generate independently scannable multiple beams. However, the GJC matrix suffers from severe beam splitting problems when one beam approaches or overlaps with another, due to anti-phases among elements caused by its inherent structure. In this paper, the beam splitting issue of the GJC matrix is investigated. Reconfigurable directional couplers are adopted and configured with two different sets of values depending on whether there is beam overlapping. A joint scanning multibeam optimization (JSMO) method is developed to eliminate the beam splitting for the Blass-like GJC matrix by optimizing the coupler coefficients using the Particle Swarm Optimization (PSO) algorithm. It allows for simultaneous consideration of multiple potential beam overlapping scenarios in the optimization. Moreover, for the Nolen-like GJC matrix, an improved JSMO (IJSMO) method is developed by incorporating an alternating coupler and phase optimization (ACPO) strategy into the JSMO method. Representative examples are provided to demonstrate the effectiveness of the JSMO and IJSMO methods in addressing the beam splitting issue. For the first time, continuous multibeam scanning has been enabled for GJC matrices without beam splitting, making them well-suited for JCAS.