u-blox AMY-5M, Руководство по оборудованию, Страница: 37 / 54

AMY-5M - Hardware Integration Manual
GPS.G5-MS5-08207-A3 Preliminary Design-in
Page 37 of 54
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 25: In-band interference signals
u-blox
5 LNA
u-
blox GPS
receiver
CPU
data bus
Figure 26: In-band interference sources
Measures against in-band interference include:
Maintaining a good grounding concept in the design
Shielding
Layout optimisation
Filtering
Placement of the GPS antenna
Adding a CDMA, GSM, WCDMA bandbass filter before handset antenna
2.11.7.4 Out-band interference
Out-band interference is caused by signal f
requencies that are different from the GPS carrier (see
Figure 27
). 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 27: 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 2.11.5) into the antenna input line to the
GPS receiver (see Figure 28).