Out-Of-Band Interference; Ensuring Interference Immunity - Quectel L76 Hardware Design

Table 6: Intermodulation Distortion (IMD) Products
Source F1 Source F2
GSM850/B5 Wi-Fi 2.4 GHz
DCS1800/B3 PCS1900/B2
PCS1900/B2 Wi-Fi 5 GHz
LTE B13 N/A

5.3.2. Out-of-Band Interference

Strong signals transmitted by other communication systems can cause a GNSS receiver to become
saturated, so that its performance is greatly deteriorated, as illustrated in the following figure.
Power [dBm]
GSM850
0
-110
0 500

5.3.3. Ensuring Interference Immunity

There are several things you can do to decrease the impact of interference signals and thus ensure the
interference immunity of a GNSS receiver:
⚫
Keep the GNSS antenna away from interference sources;
⚫
Add a band-pass filter in front of the GNSS module;
⚫
Use shielding and multi-layer PCB and ensure adequate grounding;
⚫
Optimize layout and component placement of the PCB and the whole device.
L76&L76-L_Hardware_Design
IM Calculation
F2 (2412 MHz) - F1 (837 MHz)
2 × F1 (1712.6 MHz) - F2 (1850.2 MHz)
F2 (5280 MHz) - 2 × F1 (1852 MHz)
2 × F1 (786.9 MHz)
GPS carrier frequency
1575.42 MHz
GSM900
GPS 带宽
1000
Figure 24: Out-of-Band Interference on GPS L1
DCS1800 PCS1900
2000
GNSS Module Series
IMD Products
IMD2 = 1575 MHz
IMD3 = 1575 MHz
IMD3 = 1576 MHz
IMD2 = 1573.8 MHz
Wi-Fi 2.4 GHz
Frequency [MHz]
2500
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