A Wideband Circularly Polarized Transmitarray Using Matched Dipole-Spiral Elements

In this letter, a wideband receive-and-transmit element suitable for linear-to-circular polarization applications is proposed, utilizing a combined field-circuit and conjugate matching design approach. The receiver comprises a wideband, linearly polarized kite-shaped dipole, while the transmitter is a wideband, circularly polarized spiral antenna. The two elements' excitation probes are interconnected through a central via, allowing for continuous rotation of the spiral element for phase compensation. To test the proposed design, a 0.24 lambda(0) thick transmitarray with 635 elements was constructed, and its performance was assessed. The results indicated a peak gain of 29.3 dBi and peak aperture efficiency of 55.5% within the band. The 1 dB gain bandwidth ranged from 22 to 28.5 GHz, corresponding to a bandwidth of 25.7%.