A new design of horizontally polarizedand dual-polarized uniplanar conical beam antennas for HIPERLAN

It is shown that a conical beam 5.2-GHz antenna suitable for HIPERLAN application, but working in horizontal polarization, can be realized as a group of microstrip patch radiators in a ring formation. Layouts with three and four patches are described, and radiation patterns are found to agree well with predictions from a simple array model. The three-patch form is smaller and gives a closer approximation to an azimuthindependent pattern. Patterns are very similar to those achieved in vertical polarization with previously reported disk antenna realizations, giving peak radiation at about 50(degree) elevation. Two methods of impedance matching are found to give atisfactory results. A dual-polarized conical-beam microstrip antenna, with a strictly uniplanar conductor pattern, is also presented and realized as an array of three square patches whose corners meet a central feed point. For the second polarization, the antenna functions as a series fed array. Fairly good conical beam patterns have been obtained, though only moderate polarization purity appears to be obtainable from three-element arrays.