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Rev 1 Sep.15
Proprietary and Confidential - Contents subject to change
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 Spurious Emissions (RSE)
When designing an antenna for use with AirPrime embedded modules, the host
device with an AirPrime embedded module must satisfy any applicable
standards / local regulatory bodies for radiated spurious emission (RSE) for
receive-only mode and for transmit mode (transmitter is operating).
Note that antenna impedance affects radiated emissions, which must be
compared against the conducted 50-ohm emissions baseline. (AirPrime
embedded modules meet the 50-ohm conducted emissions requirement.)
Radiated Sensitivity Measurement
A wireless host device contains many noise sources that contribute to a reduction
in Rx performance.
To determine the extent of any receiver performance desensitization 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.
RF Specifications
15
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