A Dual-Band Circularly-Polarized Transmitarray Antenna With Simultaneous Low Side-Lobe and Cross-Polarization Level

Previously proposed array antennas with low side-lobe level (SLL) based on amplitudephase metasurface inevitably result in high cross-polarization level (CPL) due to amplitude modulation is achieved by transforming some primary energy to the cross-polarization. This paper proposes a dualband circularly-polarized (CP) transmitarray antenna (TA) with simultaneous low SLL and CPL. The proposed antenna is based on a metasurface with independent amplitude and phase control at dual-band. The element of metasurface consists of dual-band receiver-transmitter (Rx-Tx) structures constructing CP receiving patches and transmitting patches. The amplitude and phase modulations at each band can be achieved dependently by adjusting the impedance-matching characteristics and the rotation angles of the Tx patches, respectively. By applying amplitude-phase modulation at dual-band, the antenna can achieve high directivity, low SLL and CPL simultaneously. Experimental results are in good accordance with the simulation ones, demonstrating that the designed low-side-lobe antenna realizes gains of 24.2 dBic and 25.2 dBic, CPLs of -32.2 dB and -26.6 dB, SLLs of -23.2 dB and -24 dB at 12 GHz and 15 GHz, respectively. The proposed TA shows good SLL and CPL performances at dual-band for dual-CP, which presents great application potential in two-way satellite communication systems with limited volume and space.