RFX144V24-S23 and RFX96V24-S23 Modem Designer’s Guide
4-6
1070
4.2 DIAGNOSTIC DATA SCALING
No. 1a
Received Signal Sample (Pre-AGC) = A/D Sample Word
Format:
16 bits, signed, twos complement
Equation:
VINT (Volts)= [(A/D Sample Word x VMAX/32768) + 2.5V
Where:
VMAX = 1.0V @ 9600 Hz sample rate
VMAX = 0.85 @ 8000 Hz sample rate
VEXT is the input to the IA
VINT is the output of the IA and input to the DSP.
No. 1b Received Signal Sample (Post-AGC) = A/D Sample Word
Format:
16 bits, signed, twos complement
Equation:
VINT (Volts)= [(A/D Sample Word x VMAX/32768) + 2.5V
VEXT = VINT/LOG10-1 [AGC Gain (dB)/20]
Where:
VMAX = 1.0V @ 9600 Hz sample rate
VMAX = 0.85 @ 8000 Hz sample rate
VEXT is the input to the IA
VINT is the output of the IA and input to the DSP.
No. 2
Received Signal Sample - 8-bit Audio Mode (Post-AGC) = A/D Sample Word
Format:
8 bits, signed, twos complement
Equation:
VINT (Volts)= [(A/D Sample Word)8] x (0.85/128) + 2.5V
VEXT = VINT/LOG10-1 [AGC Gain (dB)/20]
Where:
VEXT is the input to the IA
VINT is the output of the IA and input to the DSP.
No. 3
Average Power
Format:
16-bits, positive, twos complement
Equation:
Post-AGC Average Power (dBm) = 10 Log [(Average Power Word)h/889h]
Pre-AGC Average Power (dBm) = Post-AGC Avg. Power in dBm - AGC gain in dB
Typical Value:
0889h
No. 4
AGC Gain
Format:
16-bits, unsigned
Equation :
AGC Gain (dB) = 50 [1 - (AGC Gain Word)h/32768]
No. 5
AGC Slew Rate
Format:
16 bits, positive, twos complement
The AGC Slew Rate can be approximated by the following equation.
Equation:
AGC Slew Rate = [19968/(Sample rate x AGC gain fall time constant in seconds)]h
Note: AGC gain tracks the input signal with an exponential function with respect to time, and its fall time is approximately 5
times faster than its rise time. The above equation was determined based upon a 40 dB change in input signal.
Summary of Contents for RFX144V24-S23
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