High T/sub c/ superconducting frequency selective surfaces and their theoretical computer modeling

The authors report the results of measurements of quasi-optical millimeter-wave bandpass filters (frequency selective surface structure) fabricated using YBa/sub 2/Cu/sub 3/O/sub 7/ high-T/sub c/ superconductor thin films. The W-band (75-110 GHz) filter consisted of asymmetric two-dimensional cross arrays. Transmitted power through the filter was investigated as a function of both temperature and frequency. At 15 K and 92 GHz, a factor-of-2 improvement in the superconducting filter Q-factor was observed compared to a gold filter of identical design. More than an order-of-magnitude improvement in Q-factor is expected at lower frequencies (X-band) due to the frequency-squared dependence of the superconductor surface resistance versus that of a normal metal which has a frequency-to-the-one-half dependence. In addition, theoretical computer modeling of the superconducting frequency selective surface structure is discussed.<>