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Microstrip Patch

Microstrip & Printed Antennas

A flat metal patch printed on a dielectric board that radiates broadside.

Band: UHF to SHF (microwave)
Gain: ~6-8 dBi (single element)
Polarization: Linear or circular (feed dependent)

Photos

Real-world photo of a Microstrip Patch in use — Real-world example. Source: Wikimedia Commons (CC BY-SA 3.0; The original uploader was Serge Nueffer at French Wikipedia.).

Radiation / wave patterns

Idealized radiation pattern of the Microstrip Patch — Idealized azimuth radiation pattern (illustrative, generated). Radial scale in dB.

How & why it works

A patch antenna is a metal rectangle (often a half-wavelength on a side in the dielectric) printed over a ground plane on a circuit board. The patch and ground form a resonant cavity whose fringing fields at two opposite edges do the radiating, sending a beam broadside—straight up off the board. Being flat, light, cheap to mass-produce, and easy to integrate with circuitry, patches are everywhere in modern wireless, and feeding them appropriately can yield linear or circular polarization.

Real-world uses

GPS receivers, Wi-Fi and cellular devices, RFID readers, and phased-array building blocks.