xN930 M.2 Hardware User Guide
9
Other Information
9.1
EMI/EMC and Platform Noise
The M.2 Data Card has shielding and noise filtering in place to ensure that the
WWAN module does not impact the operation of the host system.
The M.2 Data Card must also be able to tolerate platform noise caused by high order clock
harmonics from the host processor and associated support circuitry. It is required that the
noise levels (as measured at the antenna connector) in the operating frequencies of the M.2
Data Card be no greater than 5 dB as compared to the noise floor of the host system.
9.2
Platform Noise Mitigation - Adaptive Clocking
Wireless subsystems in mobile platforms are affected by platform related noise, even with the
best antenna and chassis design. This noise hampers the wireless radio performance,
sometimes severely. For platforms that incorporate wireless subsystems like WWAN, passing
the wireless operator certification is an important component of platform launch.
One of the key elements of platform noise, commonly referred to as RF interference, is LCD
display panel pixel clock and its harmonics. The pixel clock generates RF that translates
directly into noise picked up by platform wireless radios due to the close proximity of display
electronics and the integrated antennas in the system. Many of
the panel vendors allow the pixel clock to be “tweaked” (i.e. adapt the pixel clock) to shift
the harmonics from interfering with the wireless components in operating radio frequencies.
A radio’s receive performance could be improved by moving any harmonics of the graphics
pixel clock outside of the frequencies used by the wireless modules. This will be
accomplished by shifting the display pixel clock. Shifting the pixel clock is not expected to
affect the graphics quality or its performance. The display panel refresh rate will not be
changed.
To support crosstalk mitigation, the WWAN module provides an event indication to the host
when the channel frequency changes. On the event indication, the host would use the
frequency change information (i.e. Center Frequency, Bandwidth, and any other optional
information) through an API that would facilitate the facilitating the implementation of a
noise mitigation service.
9.3
Thermal Monitoring
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