Patch antenna

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Patch antenna (right) in a GPS logger
Here, many individual patches (the small U-shaped rectangles) form an array as a panel antenna for TV satellite reception. The individual patches are fed via striplines .
Patch antenna in a mobile phone. At the top there are two antenna leads for circular polarization. The complex shape of the patch increases the antenna bandwidth

The patch antenna is an antenna variant that is particularly suitable for integration on circuit boards . The patch antenna often consists of a rectangular metal surface, the long side of which corresponds to a length of λ / 2. The metal surface thus acts as a resonator , similar to dipole antennas .

The patch antenna can have a directional effect , in particular if it is combined with a metal surface located behind it and serving as a reflector. A single element can then achieve a gain of approximately 10 dBi.

The broadband capability of a patch antenna is strongly dependent on the ratio of substrate thickness and wavelength as well as on the effective dielectric constant of the system. The width of the patch also affects the bandwidth.

Further refinements, such as the use of parasitic patches in different substrate layers, can improve the broadband and directivity of the antenna.

If several patches are arranged in an array in front of a metal surface, gain and directivity increase further ( panel antenna ).

A patch antenna can be fed in several ways, e.g. B. by means of a microstrip line or slot coupling . The type of feed has a decisive influence on the broadband and the base point impedance of the antenna.

For very high frequency bands , a patch antenna is often applied as a layer structure on a ceramic substrate. Ceramic is a very good insulator and insensitive to moisture. It also has a low dielectric loss angle .

The antenna design is also used in cell phones , WLAN and DECT cordless phones. A variant of the patch antenna is the PIF antenna .

literature

  • HH Meinke, Friedrich-Wilhelm Gundlach : Pocket book of high frequency technology . 4th edition. Springer-Verlag, Berlin 1986, ISBN 3-540-15393-4 , pp. N55 ff .
  • Girish Kumar: Broadband microstrip antennas (=  Artech House antennas and propagation library ). Artech House, Boston Mass 2003.