Broadbanding of a plate antenna with slits

Handset antennas for mobile radio communications have been small, and its high-performance characteristics over a broadband have been required. With the spread of multimedia, broadband small handset antennas are required too for video communications. In our previous studies, two-wire meander-line, two-wire helical and two-plate antennas have been investigated for the purpose of the broadbanding of the small antennas. By making the antenna element a two-wire structure, it is possible to utilize both the currents in the unbalance and balance modes on the antenna, which results in the broadband characteristics. The radiation resistance of the electrically small antenna (about one tenth of the wavelength) is generally small, and the Q-value then becomes high. Therefore, broadband impedance matching becomes complicated. In this paper, the broadband characteristics are obtained by adding a series impedance element to a small two-plate antenna with slits. The analysis is carried out by using an equivalent circuit of the antenna, and the effect of the impedance added in the series is examined.