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.