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AirPrime EM7690 Hardware Integration Guide
3.4.4.
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.
3.4.5.
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 50Ω emissions baseline. (AirPrime embedded modules meet the 50Ω conducted emissions
requirement.)
3.5.
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.
Sierra Wireless' Sensitivity Testing and
3.5.1.
Desensitization Investigation
Although AirPrime embedded modules are designed to meet network operator requirements for
receiver performance, 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.
Note:
Sierra Wireless has the capability to measure TIS (Total Isotropic Sensitivity) and TRP (Total
Radiated Power) according to CTIA's published test procedure.
3.5.2.
Sensitivity vs. Frequency
Sensitivity definitions for supported RATs:
UMTS bands — sensitivity is defined as the input power level in dBm that produces a BER (Bit
Error Rate) of 0.1%. Sensitivity should be measured at all UMTS frequencies across each band.
LTE bands — sensitivity is defined as the RF level at which throughput is 95% of maximum.
411139xx15
Rev
0.31
RF Specifications
September 23, 2020
12
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