Telecommunications Industry Association
TR41.3.5-14-08-008
Document Cover Sheet
Project Number
ANSI/TIA-PN-912-C
Document Title
Noise measurement test procedure
Source
Industry Canada
Contact
Name: Jason Nixon
Complete Address: 3701 Carling Ave,
Building 94, Ottawa, ON, K2H 8S2
Distribution
TR-41.3.5
Intended Purpose
of Document
(Select one)
X
Phone: 613-990-6551
Fax:
Email: Jason.nixon@ic.gc.ca
For Incorporation Into TIA Publication
For Information
Other (describe) -
The document to which this cover statement is attached is submitted to a TIA Engineering
Committee, Formulating Group, or sub-element thereof in accordance with the provisions of TIA
procedures including but not limited to Section 3.3.2 of the TIA Engineering Committee Operating
Procedures, all of which provisions are hereby incorporated by reference.
Abstract
The following measurement results compare the results obtained when measuring noise measurements in
the voice band using a spectrum analyzer’s band power markers versus a filter, as specified in Cablelabs
PKT-SP-HDV-IO4-120823, and a wideband volt meter.
V2.0 – 20140702
Telecommunications Industry Association
TR41.3.5-14-08-008
Background
At the May TR-41.3.5 meeting, a method to measure the in-band unweighted noise of a CPE was
being discussed. Suggestions were to use the method specified in CableLabs PKT-SP-HDVIO4-120823.
The method outlined in the CableLabs document was to use a wideband voltmeter connected to
the bandpass butterworth filter. Industry Canada suggested that this could easily be replicated
using a spectrum analyzer or FFT and band power markers at the 3dB roll-off points of the
bandpass butterworth filter.
Measurement description
Filter measurements were performed with a 6 ½ digit voltmeter connected to a 50 ohm load on
the output of the butterworth filter. The resulting voltage measurement was then converted to
dBV.
Bandpower measurements were performed with the spectrum analyzer connected across a
50ohm load with the input impedance set to 1 Mohm. The bandpower markers were set to 300
Hz and 6400 Hz. The resolution bandwidth (RBW) was varied from 30 Hz to 300 Hz
Measurement results
Bandpower measurement
Signal (-13dBm)
30 Hz RBW
100 Hz RBW
300 Hz RBW
Filter Measurement
60 Hz
-81.68 dBV
-81.32 dBV
-39.79 dBV
-106.02 dBV
180 Hz
-80.73 dBV
-79.89 dBV
-22.03 dBV
-70.17 dBV
2 kHz
-12.78 dBV
-12.78 dBV
-12.78 dBV
-16.27 dBV
White Noise
-36.76 dBV
-36.90 dBV
-35.17 dBV
-46.20 dBV
Measurement observations
Filter measurement:
- Although the design of the filter was taken from an on-line filter calculator to produce the
appropriate filter response, in practice the filter 3dB points did not correspond to the
correct frequencies and therefore the attenuation of the white noise through the pass band
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TR41.3.5-14-08-008
was greater than expected. This would explain the large difference between the white
noise measurements.
The filter was constructed with passive components and therefore did have a passband
loss of 1.72 dB. See Plot 1 for the filter response with a swept sinewave at -13 dBV.
Figure 1 - Butterworth filter
Bandpower Measurements:
- The 60 Hz measurement value represents the noise floor of the spectrum analyzer
measurement with the reference level set to the lowest value possible with the -13 dBV
60 Hz tone applied to the input. If the 60 Hz tone was of a lower value the range could
have been reduced and the bandpower level would have as well.
- The 300 Hz RBW results would not be a suggested test setup for this measurement as the
300 Hz RBW filter response caused power from the 60 Hz and 180 Hz noise to appear
within the bandpower markers.
Conclusions
-
-
Both methods would produce a valid measurement; however, the filter is a large
unknown in the test setup and could be designed to be favorable to the manufacturer.
The bandpower would have less uncertainty associated with it
The bandpower method would give a repeatable result that does not evaluate the level of
noise outside the voice band.
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TR41.3.5-14-08-008
The resolution bandwidth used for the bandpower measurement should be specified and
100Hz would be reasonable.
Do to the need for accuracy in the measurement the filter specified in the CableLabs
standard would need to be an active filter with a no passband loss.
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