Experimental results on a 12-GHz 16-element multilayer microstrip array with a high-T/sub c/ superconducting feed network

The authors describe the design, fabrication, and testing of a 4*4 microstrip array with a superconducting feed network. The structure consists of three layers which are, from top to bottom, a quartz superstrate, a vacuum gap, and a LaAlO/sub 3/ substrate. A network of power dividers and lower microstrip patches was produced on the LaAlO/sub 3/ by patterning a thin film of the high T/sub c/ superconductor YBa/sub 2/Cu/sub 3/O/sub 7-x/, and a silver ground plane was deposited on the bottom surface of the LaAlO/sub 3/. Initially, measurements were made on elements in a cryogenic waveguide simulator, which experimentally replicates an infinite array environment. The theoretical model was shown to accurately predict the resonant frequency at about 12 GHz, with a measured 2:1 voltage standing wave ratio bandwidth of 8%. Next, a 4*4 array was designed and fabricated with the lower-layer microstrip patches and feed network made from thin-film superconducting YBCO, and with silver for the ground plane. The measured far-field radiation patterns are shown.<>