EVA-M8E - Hardware Integration Manual
UBX-15028542 - R05
Contents
Page 24 of 44
Production Information
1525
1550
1625
GPS input filter
characteristics
1575
1600
0
-110
Jammin
g signal
1525
1550
1625
Frequency [MHz]
Power [dBm]
GPS input filter
characteristics
1575
1600
0
Interference
signal
GPS
signals
GPS Carrier
1575.4 MHz
Figure 8: In-band interference signals
Figure 9: In-band interference sources
Measures against in-band interference include:
•
Maintaining a good grounding concept in the design
•
Shielding
•
Layout optimization
•
Filtering e.g. resistors and ferrite beads
•
Placement of the GNSS antenna
•
Adding a CDMA, GSM, WCDMA bandbass filter before handset antenna
2.13.5.4
Out-band interference
Out-band interference is caused by signal frequencies that are different from the GNSS carrier (see
Figure 10). The main sources are wireless communication systems such as GSM, CDMA, WCDMA,
WiFi, BT, etc.
0
500
1000
1500
2000
GPS input filter
characteristics
0
-110
0
500
1500
2000
Frequency [MHz]
GSM
900
GSM
1800
GSM
1900
Power [dBm]
GPS input filter
characteristics
GPS
1575
0
-110
GPS
signals
GSM
950
Figure 10: Out-band interference signals
Measures against out-band interference include maintaining a good grounding concept in the design
and adding a SAW or bandpass ceramic filter (as recommend in section 2.13.5) into the antenna input
line to the GNSS receiver (see Figure 11).
Figure 11: Measures against out-band interference
