Many antennas are placed on circuit boards. The choice is logical. It allows for an antenna to be easily incorporated into the device it is designed for. However, it is easy to overlook the importance of the board shape and the location of the components.
Chip Antennas and Ground Planes
Out of all of the different types of antennas, chip antennas are the most sensitive to board-shape-related problems. This is because most chip antennas actually rely on the circuit board itself to radiate.
The performance of a chip antenna is rated with an example board. As covered previously, for the antenna to work as the specs show, the board must be the same size and shape as the example board. If the shape of the board is changed, the antenna will likely not perform as anticipated.
Furthermore, the antenna must be placed in the correct location on the board. Any deviations from the example board design will need to be tested and analyzed.
Conventional antennas set in PC boards are susceptible to variances in board design, as well. If an antenna using a ground plane is placed on a PC board, the ground trace of the PC board must be large enough to enable the antenna to work. Inversely, if an antenna that does not use a ground plane is incorporated into a PC board, it must be separated from the ground traces as much as possible.
PC Board Components and Properties
While all of these factors are important, the biggest variable is the location of the components.
Most standard electrical components are relatively large and metallic. Their location will affect the antenna. Metal shields can detune an antenna, or even block the RF. One of the worst offenders, however, is the batteries in the device.
Batteries are, of course, conductive by nature. This means that they can alter the performance of an antenna. Couple this with their very large size, and you can have a real problem. If the battery is placed over the antenna (and given their large size this is not a remote possibility by any means) the antenna can not only be detuned, but the battery will act to some degree as an RF shield preventing radiation.
One other potential concern is the dielectric properties of the PC board. The dielectric properties of the PC board not only affect the tuning of an antenna, but can also alter the efficiency of the system.
It is important to know the dielectric of the PC board before designing the antenna, especially at high frequencies. In some cases, it may be necessary to use a more expensive PC board to obtain the desired results.
Designing for PC Boards
The good news is that it is entirely possible to design an antenna to work around many of these factors.
The main thing is to avoid blocking the antenna with large metal objects as much as possible. The remaining problems can usually be resolved by tuning the antenna.
One thing to keep in mind is that after the antenna is initially designed any changes to the board will have the potential to foul the antenna. Small components will not likely make a big difference, but a large change to the board can cause serious results directly in proportion to how much metal is being moved around the antenna.
ARSI 
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