Specifications

RF Integration
Rev 2.0 Apr.10 Proprietary and Confidential 43
Methods to mitigate decreased Rx performance
It is important to investigate sources of localized interference early in the design
cycle. To reduce the effect of device-generated RF on Rx performance:
• Put the antenna as far as possible from sources of interference. The
drawback is that the module may be less convenient to use.
• Shield the host device. The module itself is well shielded to avoid external
interference. However, the antenna cannot be shielded for obvious reasons.
In most instances, it is necessary to employ shielding on the components of
the host device (such as the main processor and parallel bus) that have the
highest RF emissions.
• Filter out unwanted high-order harmonic energy by using discrete filtering on
low frequency lines.
• Form shielding layers around high-speed clock traces by using multi-layer
PCBs.
• Route antenna cables away from noise sources.
Radiated sensitivity measurement
A wireless device contains many sources of noise that contribute to a reduction in
Rx performance.
To determine the extent of any desensitization of receiver performance due to
self-generated noise in the host device, over-the-air (OTA) or radiated testing is
required. This testing can be performed by Sierra Wireless or you can use your
own OTA test chamber for in-house testing.
Sierra Wireless’ sensitivity testing and
desensitization investigation
Most carriers require a certain level of receiver performance to ensure proper
functioning of the device on their networks. Although AirPrime embedded
modules have been designed to meet these carrier requirements, they are still
susceptible to various performance inhibitors.
As part of the Engineering Services package, Sierra Wireless offers modem OTA
sensitivity testing and desensitization (desense) investigation. For more
information, contact your account manager or the Sales Desk (see page 4).
Note: Sierra Wireless has the capability to measure TIS (Total Isotropic Sensitivity) and
TRP (Total Radiated Power) according to CTIA's published test procedure.
OTA test chamber configuration
To make OTA measurements, a test chamber is required. A full-size anechoic
chamber is not necessarily required. Figure 3-2 on page 44 shows a small
anechoic chamber manufactured by Lindgren. This does not provide power to the