Theory and experiment on microstrip patch antennas with shorting walls

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.