patchantenner

Patch antenna, or microstrip patch antenna, is a type of radio antenna consisting of a flat metallic patch on a dielectric substrate, backed by a ground plane. It is typically fabricated using printed circuit board techniques and fed by a microstrip line, a coaxial probe, or other feeding methods.

Rectangular patches are most common, but circular and other shapes exist. Radiation arises from the patch edges, producing a broadside radiation pattern with a relatively wide azimuth beam and moderate gain. Polarization is usually linear; circular polarization can be achieved with perturbations or dual-feed configurations.

Advantages include a low profile, light weight, compatibility with PCB fabrication, and ease of integration on surfaces or in compact devices. They are widely used in GPS receivers, WLAN equipment, mobile terminals, RFID systems, and small satellite terminals. Common substrate materials include FR4 and microwave laminates such as Rogers materials. Operating frequencies range from hundreds of megahertz up to tens of gigahertz, with patch size primarily determining the frequency.

Limitations: single patches have narrow bandwidth and modest gain. Bandwidth and gain can be increased by techniques such as stacking patches, aperture-coupled feeding, proximity coupling, thicker substrates, or using patch arrays.

Feeding options include edge-fed microstrip lines, coaxial probes, and proximity- or aperture-coupled feeding. Impedance matching aims for low return loss (S11) at the target frequency. Variants include dual-band, circularly polarized, aperture-coupled, and array configurations for higher gain or specific polarization.