Xircom An Intel Company GEM3501 User Manual
Core Engine GSM/GPRS Modem Developer Guide Preliminary Draft: 7/6/2001
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Part Number: 07100026, Revision: 002
Confidential
© 2001 Xircom, Inc., an Intel company All rights reserved.
All trademarks and copyrights are the property of Xircom, Inc., an Intel company
All trademarks and copyrights are the property of Xircom, Inc., an Intel company
7.4.2 Example Differential Microphone Circuit
Figure 4 shows an example of how to implement a differential microphone circuit
compatible with the Core Engine.
compatible with the Core Engine.
Figure 3: Differential Microphone Circuit (Example)
7.5 Microphone Cable Considerations
The differential circuit design in the Core Engine baseband processor has excellent
common mode voltage rejection for noise signals.
common mode voltage rejection for noise signals.
If the microphone is located reasonably close to the Core Engine module, it should be OK
to use unshielded cable. However, this also depends on where the cable is routed. Slight
TDMA framing noises may be noticed if the cable is close to the antenna.
to use unshielded cable. However, this also depends on where the cable is routed. Slight
TDMA framing noises may be noticed if the cable is close to the antenna.
It is recommended that a twisted pair cable be used from the Core Engine microphone
connector to the microphone element. If problems arise, then a shielded cable (i.e.
termination of the shield) may be used.
connector to the microphone element. If problems arise, then a shielded cable (i.e.
termination of the shield) may be used.