Small patch/slot antenna with 53% input impedance bandwidth

A small microstrip patch/slot antenna, which achieves a very large bandwidth on a relatively thin substrate (about 0.01 lambda(0)), is presented. The performance is achieved by employing a combination of annular-ring loading on the patch radiator and the use of a crossed-slot for miniaturisation. An additional ring-slot in the ground plane is used to produce the wideband characteristics of the antenna. Simulated and measured results indicate that a 53% fractional impedance bandwidth is achieved with respect to the centre frequency of 1.409 GHz and the size of the antenna is reduced by 50% compared to the conventional circular patch antenna with respect to a given frequency.