A broadband plate antenna with slits

As a small antenna of handsets for personal communication systems, a two-strip meander-line antenna and a normal mode helical antenna have been suggested. The values of quality factors of both antennas are from 20 to 30 when the size of the antennas are smaller than 0.1 wavelength. The quality factor Q is really important to evaluate the bandwidth of an antenna. The bandwidth is in inverse proportion to Q. Therefore, if the quality factor can be small, the bandwidth becomes broadband. A plate antenna whose quality factor is smaller than those of the meander line antenna and the normal mode helical antenna can be obtained with broadband characteristics. In order to realise the impedance matching, the antenna consists of two plates, and the currents of the two plates are produced in imbalance and balance modes. In this paper, the small plate antenna with slits is treated. The impedance characteristics of the antenna is made clear and increasing the bandwidth by using two plates is also discussed.