Electrically Small Superconducting Antennas With Bandpass Filters

In order to reduce the size of a wireless system, we have proposed the design formulas for an electrically small antenna (ESA), i.e. an antenna whose dimension is much smaller than a wavelength, with a miniaturized matching circuit which connects to a 50 Omega external circuit. Theoretical performances of the slot dipole antenna with the impedance matching circuit designed by the present theory are studied by the electrical circuits using transmission lines (transmission line model) as well as the electromagnetic (EM) field simulator. We designed a slot dipole antenna with the aid of the simulations using the electrical circuits as well as the EM field simulator. The size of the designed antenna including the matching circuit is 4.1 mm times 1.9 mm on MgO substrate with relative permittivity of 9.6 at the center frequency of 5 GHz, and the designed fractional bandwidth is 13% @RL (return loss) = -3 dB. In order to demonstrate the theory, we also carried out experiments on the slot dipole antenna with the matching circuits of pole number n = 2 using high temperature superconductors YBCO on MgO substrates in the 5 GHz band.