Sierra Wireless AirPrime EM8805, Hardware Integration Manual

RF Specifications

Rev 1  Jan.13

Proprietary and Confidential - Contents subject to change

13

•

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

•

Use the AT command 

!RXDEN=0

 to disable receive diversity or 

!RXDEN=1

 to 

enable receive diversity.

Note:  A diversity antenna is used to improve connection quality and reliability through 
redundancy. Because two antennas may experience difference interference effects (signal 
distortion, delay, etc.), when one antenna receives a degraded signal, the other may not be 
similarly affected.

Ground connection

When connecting the module to system ground:

•

Prevent noise leakage by establishing a very good ground connection to the 
module through the host connector.

•

Connect to system ground using the module’s mounting hole.

•

Minimize ground noise leakage into the RF.



Depending on the host board design, noise could 

potentially

 be coupled to 

the module from the host board. This is mainly an issue for host designs that 
have signals traveling along the length of the module, or circuitry operating at 
both ends of the module interconnects.

Interference and sensitivity

Several interference sources can affect the module’s RF performance 
(RF desense). Common sources include power supply noise and device-
generated RF.

RF desense can be addressed through a combination of mitigation techniques 
(

Methods to mitigate decreased Rx performance on page 14

) and radiated 

sensitivity measurement (

Radiated sensitivity measurement on page 15

).

Note:  The EM8805 is 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.