ZED-F9P-Integration Manual
UBX-18010802 - R02
7 Electromagnetic
interference on I/O lines
Page 82 of 114
Advance Information
observed. Further, non-linear effects like gain compression, NF degradation (desensitization)
and intermodulation must be analyzed.
Pulsed interference with a low duty cycle like e.g. GSM may be destructive due to the high
peak power levels.
7.2 In-band interference mitigation
With in-band interference, the signal frequency is very close to the GNSS frequency. Such
interference signals are typically caused by harmonics from displays, micro-controller operation,
bus systems, etc. Measures against in-band interference include:
• Maintaining a good grounding concept in the design
• Shielding
• Layout optimization
• Low-pass filtering of noise sources, e.g. digital signal lines
• Remote placement of the GNSS antenna, far away from noise sources
• Adding a LTE, CDMA, GSM, WCDMA ,BT band-pass filter before antenna
7.3 Out-of-band interference
Out-of-band interference is caused by signal frequencies that are different from the GNSS carrier
The main sources are wireless communication systems such as LTE, GSM, CDMA, WCDMA, WiFi,
BT, etc.
Measures against out-of-band interference include maintaining a good grounding concept in the
design and adding a GNSS band-pass filter into the antenna input line to the receiver.
For GSM applications, like a typical handset design, an isolation of approximately 20 dB can be
reached with careful placement of the antennas. If this is insufficient, an additional SAW filter is
required on the GNSS receiver input to block the remaining GSM transmitter energy.
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