A Flat-Panel 8x8 Wideband K-/Ka-Band Dual Circularly Polarized Phased Array Antenna for CubeSat Communications

A novel flat-panel 8x8 wideband dual circularly polarized (CP) electronically scanned phased array antenna is proposed, which covers the satellite communications bands of 22.55-23.55 and 25.5-27.5 GHz. A CP stacked microstrip patch antenna is used as the element radiator with a structural modification on the parasitic patch to minimize gain variation. Since the axial ratio (AR) bandwidth of the element radiator is inherently narrow, sequential rotation is employed to yield a wide AR bandwidth while forming the 2x2 subarray, which is then used as a building block to construct the larger 8x8 phased array. The phased array has a simulated scan range of +/- 51 degrees, +/- 46., and +/- 36 degrees at 23, 24, and 26.5 GHz, respectively, assuming <= 3 dB scan loss and AR. A beamforming network (BFN) is integrated within the stackup of the phased array that comprises a commercially available silicon beamforming chip. This facilitates beam steering through the independent control of the input amplitudes and phases of the individual element radiators. The practical effects of the BFN on the scanning performance of the 8x8 phased array are studied, which is found to slightly degrade the scan ranges. Finally, experiments were performed on the fabricated prototype, and the measured scan data showed good correspondence with their simulated counterparts with >41. and 35. scan ranges (in +theta-direction) at 24 and 26.5 GHz, respectively. The corresponding equivalent isotropic radiated power (EIRP) and G/ T of the 8x8 phased array are also estimated through measurements.