The results reported in the preceding Section showed that a rectangular patch with a U shaped slot has a double looped
impedance characteristic and can attain large bandwidth without the need of adding parasitic patches in another layer or in the same layer. It is thus a single-layer single-patch wideband microstrip antenna. The widehand behaviour is probably due to the fact that the currents along the edges of the slot introduce an additional resonance, which, in conjunction with the resonance of the main patch, produce an overall broadband frequency response characteristic. The slot also appears to introduce a capacitive reactance which counteracts the inductive reactance of the probe. However, the exact mechanism responsible for the wideband behaviour is not well understood at the present time. Much experimental
and theoretical study is needed to characterise this antenna. Such studies are currently in progress