Design of a bidirectional radiation focusing antenna based on the frequency-controlled metasurface

This paper presents a bidirectional focusing antenna based on a frequency-tuned metasurface array, integrating both reflective and transmissive functions. By leveraging the metasurface's frequency selectivity, the antenna achieves distinct radiation performance in two frequency bands. The core of the design is a frequency-tunable polarization-selective metasurface. It provides differentiated polarization control and phase compensation at different frequencies. Within the target bands, it can reflect circularly polarized waves while transmitting linearly polarized waves and independently focus the beam at specific frequencies. By coupling a feed antenna with this tunable metasurface array and utilizing its frequency-dependent transmission-reflection switching, bidirectional radiation is achieved in the dual bands. Compared with conventional unidirectional antennas, this system demonstrates excellent beam focusing in both directions. In transmission mode at 11.8 GHz, it achieves a peak gain of 16.6 dBi with significant beam focusing. In reflection mode at 23 GHz, the focusing performance is further enhanced, reaching a peak gain of 19.3 dBic. Simulation and experimental results are in good agreement, validating the effectiveness of the frequency-tuning mechanism in this bidirectional focusing antenna.