RFX144V24-S23 and RFX96V24-S23 Modem Designer’s Guide
1070
4-17
No. 72
Speakerphone Line Echo Suppresser
Speakerphone line echo suppresser is a switching loss inserted in the receive (speaker) path and is enabled only in the
transmit mode (Transmit_Speech_Active = 1, Receive_Speech_Active = 0.) The loss should be kept just necessary so that
the hybrid residual echo will not be heard at maximum speaker volume control setting. The setting of this parameter is purely
subjective and will not affect any other parts of the speakerphone. Using a bigger value will help minimize the switching
effect. The default value is loaded each time the modem is configured to Speakerphone Mode (CONF = 91h.)
Format:
16 bits, positive, two's complement
Equation:
Loss = (10[x/20])(32767)
Where:
x = desired loss in dB.
Range:
07FFh - 7FFFh
Default Value:
7FFFh (0 dB)
No. 73
Speakerphone Transmit AGC Reference Level
Energy reference level for microphone AGC in speakerphone operation. When microphone signal energy is below the AGC
reference level, a gain will be added till the signal energy after AGC reaches the reference level. When microphone signal
energy is greater than the AGC reference level, a loss will be inserted until the signal energy after AGC drops to the
reference level. The default value is loaded each time the modem is configured to Speakerphone Mode (CONF = 91h.)
Format:
16 bits, positive, two's complement
Equation:
Level = (10[(x + 15)/20])(5827)
Where:
x = desired level in dB.
Range:
040Ch - 16C3h (-30 dB to -15 dB) referenced to maximum digital signal (7FFFh)
Default Value:
16C3h (-15 dB)
No. 74
Speakerphone Transmit AGC Slew Rate
The AGC slew rate determines how rapidly the AGC algorithm tracks the microphone input voice signal. Larger/smaller slew
rate values correspond to faster/slower average energy convergence to the AGC reference level. The default value is loaded
each time the modem is configured to Speakerphone Mode (CONF = 91h.)
Format:
16 bits, positive, two's complement
Range:
0098h - 04C0h
Default Value:
0260h
No. 75
Speakerphone Receive AGC Reference Level
Averaged energy reference level for speaker AGC in speakerphone operation. When line input signal energy is below its
AGC reference level, a gain will be added till the signal energy after AGC reaches the reference level. When line input signal
energy is greater than its AGC reference level, a loss will be inserted until the signal energy after AGC drops to the
reference level. The default value is loaded each time the modem is configured to Speakerphone Mode (CONF = 91h.)
Equation:
Level = (10[(x + 15)/20])(5827)
Where:
x = desired level in dB.
Range:
040Ch - 16C3h (-30 dB to -15 dB) referenced to maximum digital signal (7FFFh)
Default Value:
16C3h (-15 dB)
No. 76
Speakerphone Receive AGC Slew Rate
The AGC slew rate determines how rapidly the AGC algorithm tracks the line input voice signal. Larger/smaller slew rate
values correspond to faster/slower average energy convergence to the AGC reference level. The default value is loaded
each time the modem is configured to Speakerphone Mode (CONF = 91h.)
Format:
16 bits, positive, two's complement
Range:
0098h - 04C0h
Default Value:
0260h
Содержание RFX144V24-S23
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