AMY-6M - Hardware Integration Manual
UBX-17021971 – R07
Design-in
Page 38 of 57
Unshielded connectors (e.g. pin rows etc.)
Weakly shielded lines on PCB (e.g. on top or bottom layer and especially at the border of a PCB)
Weak GND concept (e.g. small and/or long ground line connections)
EMI protection measures are recommended when RF emitting devices are near the GPS receiver. To minimize the
effect of EMI a robust grounding concept is essential. To achieve electromagnetic robustness follow the standard
EMI suppression techniques.
http://www.murata.com/products/emc/knowhow/index.html
http://www.murata.com/products/emc/knowhow/pdf/4to5e.pdf
Improved EMI protection can be achieved by inserting a resistor or better yet a ferrite bead (BLM15HD102SN1)
into any unshielded PCB lines connected to the GPS receiver. Place the resistor as close as possible to the GPS
receiver pin.
Example of EMI protection measures on the RX/TX line using a ferrite bead:
T X
R X
G
P
S
R
e
c
e
iv
e
r
F B
F B
B L M 1 5 H D 1 0 2 S N 1
> 1 0 m m
Figure 31: EMI Precautions
VCC can be protected using a feed thru capacitor. For electromagnetic compatibility (EMC) of the RF_IN pin refer
to section 2.14.5
2.14.7
GSM applications
GSM uses power levels up to 2W (+33dBm). Make sure that absolute maximum input power level of GPS
receiver is not exceeded. See
AMY-6M Data Sheet
2.14.7.1
Isolation between GPS and GSM antenna
In a handheld type design an isolation of approximately 20dB can be reached with careful placement of the
antennas. If such isolation can’t be achieved, e.g. in the case of an integrated GSM/GPS antenna, an additional
input filter is needed on the GPS side to block the high energy emitted by the GSM transmitter. Examples of
these kinds of filters would be the SAW Filters from Epcos (B9444 or B7839) or Murata.
2.14.7.2
Increasing interference immunity
Interference signals come from in-band and out-band frequency sources.
2.14.7.3
In-band interference
With in-band interference the signal frequency is very close to the GPS frequency of 1575 MHz (see Figure 32).
Such interference signals are typically caused by harmonics from displays, micro-controller, bus systems, etc.