High-T/sub c/ superconducting small antennas

The authors describe the designs of and report experimental results for one- and two-element high-T/sub c/ superconducting small antennas composed of self-resonant helical radiators and quarter-wave matching circuits. A 500-MHz-band antenna using a lambda /40 ( lambda is the free-space wavelength) radiator fabricated with Bi(Pb)SrCaCuO bulk realized a gain of -1.2 dBi, which indicates that this antenna achieves a high frequency of 70%. A 900-MHz-band two-element array antenna using lambda /20 radiator with a lambda /11 element spacing was designed to obtain a superdirective radiation pattern. The array antenna thus fabricated with YBaCuO bulk realized both a higher efficiency than a Cu antenna and a unidirectional radiation pattern. Furthermore, by adopting EuBaCuO thin-film meander lines as the matching circuit, the total length could be reduced to about 1/4 that of an antenna using a linear circuit.<>