Quatech 802.11B/G manual Antenna Location

Quatech, Inc. Airborne Enterprise Module Databook

PCB Embedded – This approach embeds an antenna design into the host PCB. This approach is very common with add-in WiFi card (CF, PCMCIA, SDIO, etc.) as it requires no external connections and is the cheapest production approach. The lower production cost requires significant development cost and lack of performance and flexibility.

Chip – The integration of a chip antenna is simple and requires a relatively small footprint on the host system, however, it does suffer from the same limitations of flexibility and performance seen with the PCB embedded approach. There are relatively large numbers of suppliers of this type of antenna; there is also a range of configuration and performance options.

Flying Lead – This approach is similar to the flying lead solution for external antennas, the difference is that the form factors are smaller and provide a range of chassis and board mounting options, all for internal use. This approach suffers less from the performance and flexibility limitations of the other approaches, since the location of the antenna it not determined by the host PCB design. The assembly of a system using this approach maybe slightly more complex since the antenna is not necessarily mounted on the host PCBA.

8.5Antenna Location

The importance of this design choice cannot be over stressed; it can in fact be the determining factor between success and failure of the WiFi implementation.

There are several factors that need to be considered when determining location:

Distance of Antenna from radio

Location of host system

Proximity to RF blocking or absorbing materials

Proximity to potential noise or interference

Position relative to infrastructure (Access Points or Laptops)

Orientation of host system relative to infrastructure

Is it known

Is it static

To minimize the impact of the factors above the following things need to be considered during the development process:

Minimize the distance between the radio and the location of the antenna. The coaxial cable between the two impacts the Transmit Power and Receive Sensitivity negatively. Quatech recommends using 1.32-1.37mm outer diameter U.FL coaxial cables.

Minimize the locations where metal surfaces come into contact or are close to the location of the antenna.

Avoid locations where RF noise, close to or over lapping the ISM bands, may occur. This would include microwave ovens and wireless telephone systems in the 2.4GHz and 5.0GHz frequency range.

Mount the antenna as high on the equipment as possible.

28 8/11/2009 100-8080-110