Antenna-Filter-Antenna-Based Transmit-Array for Circular Polarization Application

A novel antenna-filter-antenna-based asymmetric unit cell suitable for transmit-array (TA) is proposed in this letter. This unit cell converts a clockwise circular-polarized (CP) wave to counterclockwise CP with less than 0.5 dB insertion loss at 20.5 GHz, while its rotation provides up to 360° continuous phase shift in the transmitted wave. Hence, a 14 × 14 array of the proposed unit cell is fabricated and placed in front of a CP feed antenna. Placing the TA leads to a 9.5-dBi increase in the gain of the feed, and it redirects the beam to -15° off broadside. The axial ratio of the whole system is close to 2 dB. Therefore, this transmit-array can be used for fixed and/or steerable high-gain radiations for satellite communication in Ka-band.