Sidetone (Dsp); Transmit Path Audio - Motorola V820 Service Manual

Digital wireless telephone

Table of Contents

Theory of Operation

Sidetone (DSP)

2003

the audio interface into a few passive components. The integrated

Codec converts an analog audio signal, either differential or single-

ended, from the microphone into digital signals for the MSM6050's

Vocoder. The integrated Codec also converts digital audio data from the

Vocoder into an analog audio signal, either differential or single-ended,

for the earpiece. The Codec is configured through the QDSP4000

Command types and is not directly controlled by the microprocessor.

The Codec Configuration command is sent to the QDSP4000 and then

the QDSP4000 executes the command and configures the Codec. The

internal Vocoder supports EVRC, QCLEP 13K Vocoders, along with

implementing two echo cancellers, an earseal (ESEC) and an acoustic

echo canceller (AEC) for carkit applications. The Vocoder also supports

digital FM (DFM), DTMF generation and detection, Noise Suppression,

audio AGC control, and automatic volume control (AVC). The

MSM6050 has an auxiliary Pulse Code Modulation (PCM) interface

and programmable Tx and Rx 13-Tap compensation filters to support an

auxiliary linear, mu-Law, or A-law Codec that is typically found in

carkit applications.

Sidetone is audio signal from the microphone summed into speaker

path. The MSM6050 includes the capability of adding a portion of the

Tx audio into the receive path. This sidetone is added with a

programmable gain stage, with a range of 0 dB to -96 dB, controlled

by the QDSP4000 DMA parameter CodecSTGain.

The mobile phone supports three microphone input paths identified as

Internal Microphone (MIC1), Headset Microphone (MIC2), and

External Accessory Microphone (AUDIO_IN). Headset and External

Mic inputs are single ended and Internal MIC is differential Input. The

proper Microphone path is selected by the MIC selector and path gain

is programmable at the MIC AMP1, 2 in the MSM. Refer to the

following sections and block diagram below.

Motorola Confidential Proprietary

V810

Page 22

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