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B. Voice call Uplink Mode(Receiver, Speaker, Headset)
This section provides a detailed description of the Voice Call TX functions.
MIC1 to
AUXO1 Loop
MIC1N
Microphone Input 1
34
MIC1P
35
AUXI1
Auxiliary Input 1
18
19
MIC2N
Microphone Input 2
37
MIC2P
38
AUXI2
Auxiliary Input 2
20
21
Loudspeaker
Signal from
Voice Call RX
Linear Echo
Canceller
28
33
The Uplink supports two microphones and two auxiliary inputs to the speech encoder blocks.
Both microphone inputs are compatible with an electric microphone.
The VINCENNE internal voltage source (CCO) provides the necessary drive current for the electric
microphone. The voltage source is via I2C programmable to supply 2.2V or 2.4V.
But the voltage source of our Model is to supply 2.4V.
The auxiliary audio inputs can be used as an alternative source of speech, a source from an external
microphone or as an analog loop connection. Figure 3.4.4.2 shows that the audio inputs are fed to the
transmit PGAs, which enables to adjust the total gain in the product for different sensitivities of the
microphones and spread in the transmit paths. The ADCs are followed by the transmit band pass
filters, which accept the maximum output swing that the microphone preamplifiers can deliver without
clipping, and maintain a good signal-to-noise ratio. The high pass filter in the TX-paths can be disabled
via I2C; still removing the DC offset from the signal.
For one of the two transmit paths, a transmit gain control amplifier precedes the final encoding of the
PCM output.
Audio Codec (TX-path)
Analog
Loop
ADC1
TX1 LP
TX1 HP
59
ADC2
TX2 LP
TX2 HP
60
Voice Call TX
Residual
Noise
Acoustic
Echo
Reduction
Compensation
Controller
40
41
2
3
28
Interdependency
Figure 3-4-5. Voice Call Uplink Scheme
- 61 -
53
Sidetone
Loop
54
55
Encoder
TX PGA1
TX GC
PCM 8/16
62
44
45
58
Encoder
TX PGA2
PCM 8/16
63
44
45
58
Hard Limiter
TX
Band Pass
Soft Limiter
Filter
TX
48
D
E
56
57
F
3. Technical Brief
Audio Mixer
Bluetooth
Module
A
C
1
B
FR Speech
Encoder
HR Speech
Encoder
Speech Coded
Data to Host
AMR Speech
Encoder
EFR Speech
Encoder
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