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Antennas for wireless devices can be completely embedded inside the product or can be mounted external to the product housing. Each implementation has its particular advantages and disadvantages.

4.1.1 External Antennas In the following discussion, an external antenna is assumed to be a short vertical wire or a trace (or traces) on a PCB, typically encased in a plastic housing. An external antenna is external to the main housing of the device, is connected to the device in one place (often with an RF connector), and generally is perpendicular to the largest dimension(s) of the device.

Dipoles and monopoles are typical external antennas, with a size of 1/2 and 1/4 wavelength, respectively. These antennas, if designed correctly, provide excellent performance. External antennas achieve high efficiency and have, in general, better immunity to the self-generated noise of the product, although any antenna is susceptible to external noise.

While external antennas can provide superior performance, there are significant disadvantages: susceptibility to damage, additional manufacturing cost, and potential performance degradation due to the user's interaction with the exposed antenna. While external antennas clearly have their uses, they are generally not recommended for the typical modern hand-held wireless device.

4.1.2 Embedded Antennas An embedded antenna is any antenna that lies completely within the device housing. It is most typically mounted parallel to the largest dimension(s) of the device. An embedded antenna may or may not use connectors. Embedded antennas may be printed on the edge of a PCB, can be a separate sheet metal part (or wire) that is soldered to a PCB, or can be a hybrid of these techniques. The antenna can be sprayed or painted (using conductive paint) on the plastic housing of the device. An embedded antenna can also be created from conductive parts of the device structure. Very small “chip” antennas that can be

Antenna Fundamentals Technical Brief


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