Developments of a novel impedance matching circuit for electrically small antennas

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 ohm external circuit. We designed a slot dipole antenna with the aid of the simulations using the electrical circuits as well as the electromagnetic field (EM field) simulator. The size of the designed antenna including the matching circuit is 4.1 mm × 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%@RL3dB. We also made experiments on the slot dipole type ESA with a matching circuit using YBCO thin films on MgO substrates.