Specifications

RF Integration
Rev 2.0 Apr.10 Proprietary and Confidential 41
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 applications, 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 perfor-
mance.
• Connecting cables between the module and the antenna must have 50 
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—If your host device is not designed to use the MC57xx module’s
diversity antenna, terminate the interface with a 50  load.
• MC8201/MC8700/MC8780/MC8781/MC8790/MC8790V/MC8791V/
MC8792V/MC8795V —Use the AT command
!RXDEN=0 to disable receive
diversity or
!RXDEN=1 to enable receive diversity.
Interference and sensitivity
Note: These modules are
based on ZIF (Zero Inter-
mediate Frequency)
technologies. When
performing EMC (Electro-
magnetic Compatibility)
tests, there are no IF
(Intermediate Frequency)
components from the
module to consider.
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.
Note: Values in this guide
are taken from the appro-
priate product specifi-
cation documents (PSDs)
(listed in Related
documents on page 13)—
in the case of a
discrepancy between this
document and the relevant
PSD, use the value listed
in the PSD.
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.