Single-feed superconducting circularly polarized microstrip array antenna for direct-to-home receiving system

Single-feed circularly polarized microstrip patch and patch array antennas for 'direct-to-home' receiving system at around 12 GHz are studied by theor etical analysis and experiments. A full-wave microwave circuit simulator (E m), based on the method of moments and capable of handling the microwave su rface impedance, has been used in the theoretical analysis of the antennas. Antennas have been fabricated from both normal conductor (gold) and YBa2Cu 3O7-x (YBCO) superconductor for comparison. Measured results on resonant fr equency (f(r)), return loss, gain, bandwidth, and axial ratio are presented . The antennas are found to show a very low axial ratio and a moderate band width. In the comparison of gain, the superconducting antennas showed a rem arkable improvement over their gold counterparts. The receiving power of a four-element array fabricated from a single-side YBCO thin film on (100) Mg O single crystal substrate is found to be 1.8 dB higher than that of a gold array with identical configuration and both measured at 77 K.