of the PCB). If this is not possible, the printed antenna should be placed in the corner of the board so two sides are exposed. Surrounding the printed antenna on three sides, or even worse, on all 4 sides, will degrade performance substantially.
Antenna Impedance not Validated in Product
Commercial antennas, either external or embedded, often have return loss specifications that have been measured by the manufacturer. While this is useful data, the antenna impedance must be validated with the antenna installed in the product, with all of the surrounding materials (conductors and non-conductors) in place, and with all components installed on the PCB. Even the small details of a plastic enclosure can influence the impedance of the antenna.
Antenna Too Close to Digital Noise Source
Electrical noise generated by the circuitry of the device can enter the antenna directly and result in poor or intermittent performance, and failure at the PTCRB test lab. Care should be taken to locate the antenna as far as possible from noise sources.
Antenna Placed In Poor Location with regard to Body Effects
If the product is to be hand-held or otherwise in contact with the human body, remember that interaction with the human body will introduce power loss external to the product in both receive and transmit operation. As a separate issue, interaction with the human body will also cause de-tuning of the antenna. Both of these effects seriously degrade performance. Testing should be performed to properly quantify the effects of the human body.
4.4 Antenna Design and Implementation Assistance
There are several approaches available to achieve the intended antenna implementation and performance. The three primary approaches are:
Antenna Fundamentals – Technical Brief