EM919
1
Hardware Integration Guide
RF Specifications
11
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. See
Interference from Other Wireless Devices
.
Disabling the Auxiliary (Diversity) Antenna
Certification testing of a device with an integrated EM919
1
may require the module’s main
and diversity antennas to be tested separately.
To facilitate this testing, receive diversity can be enabled/disabled using AT commands:
!RXDEN
— used to enable/disable diversity for single-cell call (no carrier aggregation).
!LTERXCONTROL
— used to enable/disable paths (in carrier aggregation scenarios) after a call
is set up.
Note:
LTE networks expect modules to have more than one antenna enabled for proper operation.
Therefore, customers must not commercially deploy their systems with the diversity antenna
disabled.
A diversity antenna is used to improve connection quality and reliability through redundancy.
Because two antennas may experience different interference effects (signal distortion, delay, etc.),
when one antenna receives a degraded signal, the other may not be similarly affected.
3.3.
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 ground hole shown in
Figure 3-1
.
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.
3.4.
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
) and radiated sensitivity measurement (
Radiated Sensitivity
Measurement
).
Note:
The EM919
1
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.
3.4.1.
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 range may cause spurious response, resulting in decreased Rx
performance.
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