Interference And Sensitivity; Power Supply Noise; Interference From Other Wireless Devices - Sierra Wireless MC5725 Hardware Integration Manual

Note: These modules are based
on ZIF (Zero Intermediate
Frequency) technologies; when
performing EMC
(Electromagnetic Compatibility)
tests, there are no IF
(Intermediate Frequency)
components from the module to
consider.
Note: Values in this guide are
taken from the appropriate
product specification documents
(PSDs) (listed in
documents
,
case of a discrepancy between
this document and the relevant
PSD, use the value listed in the
PSD.
Rev 1.9.1 Feb.09
In the event of a discrepancy in values between this guide and the Product Specification Document (PSD), the PSD takes precedence.
Related
page 13) — in the
Proprietary and Confidential
tions, the placement of the antenna is still very important —
if the host device is insufficiently shielded, high levels of
broadband or spurious noise can degrade the module's
performance.
Connecting cables between the module and the antenna
•
must have 50 Ω impedance. If the impedance of the module
is mismatched, RF performance is reduced significantly.
• Antenna cables should be routed, if possible, away from
noise sources (switching power supplies, LCD assemblies,
etc.). If the cables are near the noise sources, the noise may
be coupled into the RF cable and into the antenna.
Disabling the diversity antenna
MC57xx — I f your host device is not designed to use the
•
MC57xx module's diversity antenna, terminate the interface
with a 50 Ω load.
MC8780 / M C8781 / M C8785V / M C8790 / M C8790V /
•
M C8791V / M C8792V — Use the AT command
disable receive diversity or
diversity.

Interference and sensitivity

Several sources of interference can affect the RF performance
of the module (RF desense). Common sources include power
supply noise and device‐generated RF.
RF desense can be addressed through a combination of
mitigation techniques and radiated sensitivity measurement.

Power supply noise

Noise in the power supply can lead to noise in the RF signal.
The power supply ripple limit for the module is no more than
200 mVp‐p 1 Hz to 100 kHz. This limit includes voltage ripple
due to transmitter burst activity.

Interference from other wireless devices

Wireless devices operating inside the host device can cause
interference that affects the module.
To determine the most suitable locations for antennas on your
host device, evaluate each wireless device's radio system,
considering the following:
Any harmonics, sub‐harmonics, or cross‐products of signals
•
generated by wireless devices that fall in the module's Rx
RF Integration
!RXDEN=0
!RXDEN=1
to enable receive
to
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