A new technique is described for feeding printed antennas. A microstrip antenna on one substrate is coupled through an electrically small aperture to a microstrip feed line on a perpendicularly oriented substrate. No direct connection is made to the patch. Such a geometry allows two separate substrates to be used for the antenna and feed functions. Measurements of a prototype design are presented.

Aperture-coupled microstrip antenna with a perpendicular feed

An arbitrarily shaped microstrip patch antenna excited through an arbitrarily shaped aperture in the mouth of a rectangular waveguide is investigated 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 domain integral equation approach. More specifically, the Green's functions for the layered medium and the waveguide are used to formulate a coupled set of integral equations for the patch current and the aperture 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 computational 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 section (RCS) of a plane-wave excited structure is obtained in a like manner. Sample numerical results are presented and are found to be in good agreement with measurements and with published data. >

Waveguide excited microstrip patch antenna-theory and experiment

A compact, low loss and mass producible antenna filter is proposed. The radiating element consists of a microstrip patch. Waveguide feeding ensures low loss. Coupling with the antenna is achieved via a slot in the ground plane, maintaining the simplicity of the structure. In order to avoid any complicated transitions, an E-plane filter is integrated in the waveguide. Simulated and experimental results at X-band are presented to validate the argument.

Antenna Filter for Modern Wireless Systems

This paper presents electromagnetic simulation of a dielectric-filled rectangular waveguide antenna filter structure. A microstrip rectangular patch antenna represents the radiating element of this structure and it is endwall coupled with a waveguide that incorporates E-plane filter via a slot in the ground plane. Microstrip antenna, dielectric filling of the waveguide and direct connection between the antenna and the filter ensure compactness as the primal goal. The example antenna filter is designed and simulated at the centre frequency of 11.85 GHz.

Electromagnetic modelling of dielectric-filled waveguide antenna filters

Antennenstruktur Antenna structure

The fabrication of various iris-fed millimeter-wave rectangular microstrip patch antennas is described. A mathematical model is proposed to describe the iris-fed antenna. An iris having 15 percent of the area of the patch is used to couple energy into the antenna. Resonance of the antenna is observed to be insensitive to the size of the iris for irises up to 115 percent of the size of the patch. A study is also made of the coupling to the antenna as a function of position of the iris with respect to the transverse plane of the waveguide, the iris always being centered with respect to the patch. In general, the antenna has a VSWR in the waveguide feed of roughly 5:1 at resonance, except for the fully open waveguide which gives rise to a VSWR of 2.9:1 at resonance. Far-field antenna power patterns are observed to be quite broad with H-plane beamwidths about 130°. Maximum antenna gain observed was 4.5 dB relative to an isotropic source (dBi), with 2 dBi typical. An initial study is made of the microstrip patch antenna fed from a longitudinal waveguide wall. Results indicate that this feed structure is likely to prove valuable for microstrip patch antennas, with coupling at least as good as for the transverse-fed patch, added to the possibility of feeding multiple patches from a single waveguide.

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David H. Greenlee

Papers

The Characteristics of Iris-Fed Millimeter-Wave Rectangular Microstrip Patch Antennas