ANSI SCTE-119-2011 pdf download Measurement Procedure for Noise Power Ratio
1.0 SCOPE
This procedure defines a method of measurement for Noise Power Ratio (NPR) of active Cable Telecommunications equipment. It is intended for measurement of 75-ohm devices having type “F” or 5/8-24 KS connectors. See SCTE 96 2008 Cable Telecommunications Testing Guidelines for a discussion of proper testing techniques. This procedure uses a spectrum analyzer to measure the noise power in a narrow frequency band. Other means of measurement such as a narrow band filter followed by a power meter may be used as long as the results can be shown to correlate to this method.
2.0 INFORMATIVE REFERENCES
The following documents may provide valuable information to the reader but are not required when complying with this standard. [SCTE 96] SCTE 96 2008 Cable Telecommunications Testing Guidelines
3.0 COMPLIANCE NOTATION
“SHALL” This word or the adjective “REQUIRED” means that the item is an absolute requirement of this specification.
“SHALL NOT” This phrase means that the item is an absolute prohibition of this specification.
4.0 DEFINITIONS AND ACRONYMS 4.1 Noise Power Ratio (NPR) Test: A test method that examines the amount of noise and intermodulation distortion in a channel. A test signal, comprised of flat Gaussian noise band limited to the frequency range of interest and with a narrow band (channel) of the noise deleted by a notch filter or other means, is injected into the Device Under Test (DUT). The NPR is measured at the output of the DUT as the test signal is swept across a power range. See Figure 1 for an example of an NPR test signal.
4.2 Noise Power Ratio: The ratio of the signal power density to the power density of the combined noise and intermodulation distortion in the channel. Essentially, NPR is the depth of notch. The signal power density is defined with the entire passband filled with energy. The power density of the noise and intermodulation distortion shall be measured by removing signal power from a range of frequencies with a notch filter while maintaining constant total signal power at the DUT input.