Linx Technologies EVAL-xxx-KH3 - Manual (Page 7)

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About Antennas
The choice of antennas is one of the most critical and often overlooked
design considerations. The range, performance, and legality of an RF link
are critically dependent upon the type of antenna employed. Linx offers
a variety of antenna styles that can be considered for a design. Included
with the kit is a Linx CW Series connectorized whip antenna that should
be connected prior to using the kit. Despite the fact that the antenna is
not centered on the board’s ground plane, it exhibits a VSWR of <1.7 and
suitably demonstrates the module’s best practical performance.
In Closing
Here at Linx, “Wireless Made Simple” is more than just our motto, it is our
commitment. A commitment to the highest caliber of product, service,
and support. That is why, should you have questions or encounter any
difficulties using the evaluation kit, you’ll be glad to know many resources
are available to assist you. First, check carefully for the obvious, then
visit our website at www.linxtechnologies.com or call +1 541 471 6256
between 8AM and 4PM Pacific Time to speak with an application engineer.
Legal Notice: All Linx kits and modules are designed in keeping with
high engineering standards; however, it is the responsibility of the user to
ensure that the products are operated in a legal and appropriate manner.
The purchaser understands that legal operation may require additional
permits, approvals, or certifications prior to use, depending on the
country of operation.
RSSI voltage with the transmitter turned off to determine if ambient
interference is present. If this fails to resolve the issue, please contact Linx
technical support.
Using the Boards as a Design Reference
The basic evaluation boards included in this kit are very simple, yet they
illustrate some important techniques that should be incorporated into the
board layout. The module’s mounting pads extend slightly past the edge of
the part. This eases hand assembly and allows for better heat conduction
under the part if rework is necessary. A full ground plane fill is placed on the
bottom of the board. This ground plane serves three important purposes:
First, since a quarter-wave antenna is employed, the ground plane is
critical to serve as a counterpoise (please see Application Note AN-00500
“Antennas: Design, Application, and Performance” for details on how a
ground plane affects antenna function).
Second, a ground plane suppresses the transfer of noise between stages
of a product as well as unintentional radiation of noise into free space.
Third, a ground plane allows for the implementation of a microstrip feed
between the module and the antenna. The term microstrip refers to a PCB
trace running over a ground plane that is designed to serve as a 50-ohm
transmission line. See the module’s data guide or the calculator available
on our website for details on microstrip calculations.