Specifications

Wireless CPU
®
Q24 Series
Interfaces
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This document is the sole and exclusive property of WAVECOM. Not to be distributed or divulged without
prior written agreement.
WM_PRJ_Q24NG_PTS_001-004
January 16, 2007
3.12 Audio Interface
Two different microphone inputs and two different speaker outputs are supported.
The Wireless CPU
®
Q24 Series also include an echo cancellation feature, which allows
hands-free operation.
Caution:
When speakers and microphones are exposed to the external environment, it is
recommended to add ESD protection on the audio interface lines.
3.12.1 Microphone Inputs
The MIC2 inputs already include the biasing for an electret microphone, thus allowing
easy connection to a handset.
The MIC1 inputs do not include an internal bias. MIC1/SPK1 may be used for a
hands-free system or a handset, including biasing circuit for the microphone.
The microphone connections may be either differential or single-ended, but using a
differential connection in order to reject common mode noise and TDMA noise is
strongly recommended.
Caution:
While using a single-ended connection, ensure to have a good ground plane, a good
filtering as well as shielding, in order to avoid any disturbance on the audio path.
3.12.1.1 Common Microphone Input Characteristics
Both microphone inputs are designed with the following audio transmit
characteristics:
Internal audio filter characteristics
Frequency Gain
0-150 Hz < -22 dB
150-180 Hz < -11 dB
180-200 Hz < -3 dB
200-3700 Hz 0 dB
>4000 Hz < -60 dB
The gain in the MIC inputs are internally adjusted and may be tuned from -6.5 dB to
51.3 dB by using AT commands (refer to AT commands documentation
[4]).