Shielding; Antenna And Cabling - Sierra Wireless MC5720 Hardware Integration Manual

MC5720/8755/8765 Hardware Integration Guide
14

Shielding

The module is fully shielded to protect against EMI and to
ensure compliance with FCC Part 15 ‐ "Radio Frequency
Devices" (or equivalent regulations in other jurisdictions).
Note: The module shields must NOT be removed.

Antenna and cabling

When selecting the antenna and cable, it is critical to RF perfor‐
mance to match antenna gain and cable loss.
Choosing the correct antenna and cabling
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 MC5720 and MC8755/8765 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,
2130114