Inverted-F antenna

The design has two advantages over a simple monopole: the antenna is shorter and more compact, allowing it to be contained within the case of the mobile device, and it can be impedance matched to the feed circuit by the designer, allowing it to radiate power efficiently, without the need for extraneous matching components.

However, its most widespread use is as a planar inverted-F antenna (PIFA) in mobile wireless devices for its space saving properties.

The advantage of doing this is that the input impedance of the antenna is dependent on the distance of the feed point from the grounded end.

It can be used to implement required distributed-element RF components such as filters, while at the same time being economical because the same mass production methods are used as for printed circuit boards.

This works on the same principle as an inverted-F; viewed sideways, the F shape can be seen, it is just that the antenna element is very wide in the horizontal plane.

[6] The shorted patch antenna has a wider bandwidth than the thin line type due to the greater radiation area.

The thin line type of inverted-F antennas with the ground plane to one side like A and B in the diagram are just called IFA even if they are in planar format.

In this configuration, the resonant frequency is given approximately by, This formula only holds if the antenna is not affected by nearby dielectrics, such as the casing of the device.

[14] The need for multi-band antennas arises with mobile devices that need to roam between countries and networks where the frequency bands used can often be different.

Another technique is to insert one or more spur lines into the patch, which has the effect of coupled resonators broadening the band.

This includes mobile phones and tablet computers using wireless transmissions such as GSM, Bluetooth, and Wi-Fi.

Multiband PIFAs can be used to combine the antenna feeds for mobile phone, satellite navigation, and car radio.

[20] These antennas have been used for telemetry applications at military test ranges, including those supporting Inter-Range Instrumentation Group standards.

These frequencies are in the same ratio as the mobile phone GSM bands at 900 MHz and 1.8 GHz so the design could be used for this application as well if the dimensions were scaled down to suit.