PIFA

PIFA stands for planar inverted-F antenna. It is a type of radio-frequency radiator used in compact wireless devices. The structure consists of a planar metallic patch positioned parallel to a ground plane, with a shorting pin (via) connecting one edge of the patch to the ground and a separate feed point located away from the short. This arrangement creates an inverted-F current distribution that enables resonance in a small form factor.

Operation relies on the interaction between the shorting pin and the feed point to shape the current path on the patch. The distance between the feed and the short, along with the height of the patch above the ground plane, determines the resonant frequency and impedance bandwidth. Rectangular patches are common, but designers may introduce meanders, slots, or additional patches to tune bands and save space. PIFAs are often designed to cover one or more frequency bands by exploiting different resonant modes or by stacking elements.

Design considerations include the size of the ground plane, the patch dimensions, the clearance above the ground, and the location of the feed and shorting connection. Impedance matching is typically achieved by adjusting these features, sometimes with matching stubs or parasitic elements. Variants such as meandered or folded patches, multi-band configurations, and stacked PIFAs are used to meet specific bandwidth and multi-band requirements.

Advantages of PIFAs include a low profile, ease of fabrication, and good integration with device chassis and metal enclosures. They offer relatively high efficiency in a compact form factor and are suitable for many mobile and wireless applications. Limitations include narrower bandwidth for single-patch implementations, sensitivity to user handling and nearby metal, and design complexity when supporting wide or multiple bands.

Applications are common in mobile phones, tablets, Wi‑Fi devices, and other compact wireless terminals where a planar, low-profile antenna is advantageous. Design typically relies on electromagnetic simulation and experimental validation.