Cisco Model 6944 and 6940 Node bdr Dig Rev 2 1 Mux System for Prisma II Installation Guide
Resulting NPR,
Continued
An alternative way to present the information in the left half of the NPR curve is
shown in Figure A8.
shown in Figure A8.
Noise vs Composite Input Power
-104.00
-102.00
-100.00
-98.00
-96.00
-94.00
-92.00
-90.00
-10.00
-5.00
0.00
5.00
10.00
15.00
20.00
25.00
Composite Input Power (dBmV)
Noi
se (
dBmV/
Hz)
Figure A8. Quantization noise changes as a function of input level
At a composite input level above approximately 22 dBmV, the noise is dominated by
clipping distortion. However, below 22 dBmV, the noise is results from quantization
error, NOT DISTORTION OR CLIPPING. As Figure A6 indicates, the quantization
noise floor changes around 7 dB as the composite input level is increased from –5
dBmV to +22 dBmV. This quantization noise results from the individual steps in the
A/D – D/A transfer characteristic.
clipping distortion. However, below 22 dBmV, the noise is results from quantization
error, NOT DISTORTION OR CLIPPING. As Figure A6 indicates, the quantization
noise floor changes around 7 dB as the composite input level is increased from –5
dBmV to +22 dBmV. This quantization noise results from the individual steps in the
A/D – D/A transfer characteristic.
During the generation of the NPR curve, changing the signal amplitude while
maintaining a constant bandwidth varies the composite power. However, the
results are the same if the signal amplitude is held constant and the bandwidth is
varied. Thus, as loading on an individual link changes, the quantization noise floor
changes. This characteristic is critical for understanding overall system performance
as multiple links are combined.
maintaining a constant bandwidth varies the composite power. However, the
results are the same if the signal amplitude is held constant and the bandwidth is
varied. Thus, as loading on an individual link changes, the quantization noise floor
changes. This characteristic is critical for understanding overall system performance
as multiple links are combined.
26
Improving the Performance and Capacity of Digital Reverse Systems
4000819 Rev B