WAVE-GUIDE EXCITED MICROSTRIP PATCH ANTENNA - THEORY AND EXPERIMENT

An arbitrarily shaped microstrip patch antenna excited through an arbi trarily shaped aperture in the mouth of a rectangular waveguide is inv estigated theoretically and experimentally. The metallic patch resides on a dielectric substrate grounded by the waveguide flange and may be covered by a dielectric superstrate. The substrate (and superstrate, if present) consists of one or more planar, homogeneous layers, which may exhibit uniaxial anisotropy. The analysis is based on the space do main integral equation approach. More specifically, the Green's functi ons for the layered medium and the waveguide are used to formulate a c oupled set of integral equations for the patch current and the apertur e electric field. The layered medium Green's function is expressed in terms of Sommerfeld-type integrals and the waveguide Green's function in terms of Floquet series, which are both accelerated to reduce the c omputational effort. The coupled integral equations are solved by the method of moments using vector basis functions defined over triangular subdomains. The dominant mode reflection coefficient in the waveguide and the far-field radiation patterns are then found from the computed aperture field and patch current distributions. The radar cross secti on (RCS) of a plane-wave excited structure is obtained in a like manne r. Sample numerical results are presented and are found to be in good agreement with measurements and with published data.