PSB2163T-V31TR Infineon Technologies, PSB2163T-V31TR Datasheet - Page 148

• Manufacturer Part Number: PSB2163T-V31TR
• Description: IC AUDIO RINGING CODEC 28-PDSO
• Manufacturer: Infineon Technologies
• Series: ARCOFI®r

Specifications of PSB2163T-V31TR

• Function: CODEC Filter
• Interface: IOM-2, PCI, Serial
• Number Of Circuits: 1
• Voltage - Supply: 5V
• Current - Supply: 900µA
• Power (watts): 1mW
• Operating Temperature: -25°C ~ 80°C
• Mounting Type: Surface Mount
• Package / Case: DSO-28
• Includes: Activation and Deactivation, B-Channel and D-Channel HDLC Controllers, D-Channel Priority Handler, Monitor Channel Handler
• Lead Free Status / RoHS Status: Request inventory verification / Request inventory verification
• Other names: PSB2163T-V31INTR; PSB2163T-V31TR

Speakerphone Implementation
2.6
The Speech Comparator for the Acoustic Echo
The speech comparator for the acoustic echo has the important task to decide, whether
a signal actually being received by the microphone is an echo or really a speech activity.
This is done by comparing the amplitude of the incoming signal with the amplitude of the
outgoing signal (See “Basics about the Speakerphone Algorithm” on page 140). If the
transmit signal is stronger than the signal being received at that moment, this will be
indicated to the speakerphone control logic which does a mode switching if also the
corresponding speech detector has recognized speech.
To understand how the comparator works it is assumed at first order, that mechanical
resonances can be neglected compared to the different kinds of acoustic echo. The
acoustic echo can be divided into two main parts. The first part of the signal reaches the
microphone directly from the loudspeaker, travelling inside or outside the telephone
housing (part 1). The second part results from reflections at the walls or boundaries like
the desk where the telephone is placed on (part 2). It takes about one millisecond for
signal part 1 to travel from loudspeaker to microphone (depending on the geometrical
arrangement). Reflected signals are not only weaker than the direct sound, they also
arrive with a certain delay. This situation is illustrated in figure 8.
Figure 8
Acoustic Echoes Resulting from Direct Coupling (1) or Reflections (2)
Semiconductor Group
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