Antenna And Cabling - Sierra Wireless MC5725V Hardware Integration Manual

CDMA and GSM / UMTS Mini Card Hardware Integration Guide
Note: Values in this guide are
taken from the appropriate
product specification documents
(PSDs) (listed in
documents
, page
case of a discrepancy between
this document and the relevant
PSD, use the value listed in the
PSD.
20
In the event of a discrepancy in values between this guide and the Product Specification Document (PSD), the PSD takes precedence.

Antenna and cabling

When selecting the antenna and cable, it is critical to RF perfor‐
mance to match antenna gain and cable loss.
Related Choosing the correct antenna and cabling
8) — in the
Consider the following points for proper matching of antennas
and cabling:
The antenna (and associated circuitry) should have a
•
nominal impedance of 50 Ω with a return loss ≤ 10 dB
across each frequency band of operation.
• The system gain value affects both radiated power and
regulatory (FCC, IC, CE, etc.) test results.
Developing custom antennas
Consider the following points when developing custom‐
designed antennas:
• A skilled RF engineer should do the development to ensure
that the RF performance is maintained.
Identify the bands that need to be supported, particularly
•
when both the MC57xx and MC87xx will be installed in the
same platform. In this case, you may want to develop
separate antennas for maximum performance.
Determining the antenna's location
Consider the following points when deciding where to put the
antenna:
Antenna location may affect RF performance. Although the
•
module is shielded to prevent interference in most applica‐
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.
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