Siemens MC35 Specifications download pdf (Page 26)

MC35i Terminal Hardware Interface Description

Confidential / Released

MC35i_T_HD_v02.00a Page 26 of 42 16.02.2007

3.5.3.2 Speech processing

The voiceband filter includes a digital interpolation low-pass filter for received voiceband

signals with digital noise shaping and a digital decimation low-pass filter for voiceband

signals to be transmitted.

After voiceband (interpolation) filtering the resulting 2Mbit/s data stream is digital-to-analog

converted and amplified by a programmable gain stage in the voiceband processing part.

The output signal can directly be connected to the earpiece of the GSM cellular device or to

an external handset earpiece (via I/O connector). In the opposite direction the input signal

from the microphone is first amplified by a programmable amplifier. After analog-to-digital

conversion a 2Mbit/s data stream is generated and voiceband (decimation) filtering is

performed.

The resulting speech samples from the voiceband filters are handled by the DSP of the

baseband controller to calculate e.g. amplifications, sidetone, echo cancellation or noise

suppression.

Full rate, half rate and enhanced full rate, speech and channel encoding including voice

activity detection (VAD) and discontinuous transmission (DTX) and digital GMSK modulation

are also performed on the GSM baseband processor.

Note: With regard to acoustic shock, the cellular application must be designed to avoid

sending false AT commands that might increase the amplification, e.g. for a high

sensitive earpiece.

1 2 ... 21 22 23 24 25 26 27 28 29 30 31 ... 41 42

No comments

Siemens MC35 Specifications Page 26