Experimental and calculated results based on the finite-difference time-dom
ain method are presented on the impedance and radiation characteristics of
the classic shorted quarterwave patch. It is found that, for foam substrate
s with relative permittivity close to unity, the bandwidths of the quarterw
ave patches are significantly larger than the halfwave patches. On the othe
r hand, for microwave substrates with relative permittivites equal to 2.32
and 4.0. the bandwidths of quarterwave patches are less than those of halfw
ave patches, owing to the excitation of surface waves. The maximum gain in
the case of foam substrate is in the range of 2-3.5dBi, occurring 0-45 degr
ees from broadside, depending on the substrate thickness. The use of a part
ial short, while reducing the resonant frequency, also decreases the bandwi
dth. The paper also describes the application of the shorting-wall principl
e to realise a compact wideband L-probe patch antenna.