GB/T 4574-1984 Test method for actual circuit noise and circuit noise of simulated system load in simulated communication network
Some standard content:
National Standard of the People's Republic of China
GB/T4574—1984
Measuring methods for actual circuit noise andthe circuit noise in simulating system loadingover the analogue communication networkPublished on July 17, 1984
National Bureau of Standards
Implementation on April 1, 1985
National Standard of the People's Republic of China
Measuring methods for actual circuit noise andthecircuitnoisein simulating system loadingover the analogue communication networkUDC
621.391.82
：534.61
GB/T4574—1984
This standard proposes two noise test methods. The first method is suitable for measuring the actual circuit noise in the simulated communication network, and can also be used for maintenance testing. The second method proposes to use white noise to simulate the system load to measure the noise generated by the circuit, base group segment and super group segment of the frequency division multiplexing system in the communication network, which is suitable for acceptance testing and quality inspection. 1 Actual circuit noise measurement
1.1 Instrument used
Noise tester, the main characteristics requirements are shown in Appendix A. 1.2 Test point
Measurement point of four-wire circuit switching point (receiving) Measurement point of two-wire circuit switching point;
Network audio four-wire interface point (receiving).
1.3 Test method
The test should be performed when the circuit under test is idle. The circuit far-end terminal is 6002 resistor, the measured point is directly connected to the noise tester, and the terminal method is used for measurement. The noise tester uses 600Q balanced input impedance, telephone weighting, and 200ms integration time slot for measurement. The measured result is the noise meter absolute power level (or voltage) of the circuit under test. 2 Circuit noise measurement of simulated system load
2.1 White noise simulated system load method Noise test principle Use uniform spectrum random noise signal to simulate the load of circuits, base group segments and super group segments composed of frequency division multiplexing system in communication network under actual operating conditions, and test the crosstalk noise of multiple channels to one channel and the inherent noise of the channel. This method is referred to as white noise simulation method.
2.2 Principle diagram of noise test by white noise simulation method 2.2.1 Principle diagram of circuit noise test
Published by National Bureau of Standards on July 17, 1984
Implementation on April 1, 1985
GB/T4574—1984
In the figure:
1—A noise source with variable power;
Ruining road chain
Borun Electric Appliance
Figure 1 Principle diagram of circuit noise test
A bandpass filter with effective bandwidth B equal to 0.3~3.4kHz, a conventional telephone signal shaping network;
—An effective bandwidth - Bandpass filter with B equal to 60~108kHz 4
5——Power divider;
6—Bandpass filter with effective bandwidth B equal to 312~552kHz: - Bandpass filter with effective bandwidth B equal to 812~2044kHz; 8
10~12-
-Circuit under test;
Noise tester;
Noise generator;
Transmitting input of circuit under test,
Receiving output of circuit under test:
-Basic basic group interface point;
Basic super group interface point,
Basic main group interface point.
2.2.2 Principle diagram of base group noise test
In the figure:
1——noise source with variable power;
GB/T4574—1984
Filter test model
FO-1502
Figure 2 Principle diagram of base group noise test
2——Bandpass filter with effective bandwidth B equal to 60~108kHz, and bandstop filter with center frequency f. 3
A power divider,
A bandpass filter with effective bandwidth B equal to 312～552kHz; a bandpass filter with effective bandwidth B equal to 8122044kHz; the base group to be tested;
receiving bandpass filter, with center frequency f. , bandwidth △f is about 2kHz, receiving variable attenuator;
10——RMS detection level meter;
11~14——noise generator;
15——noise receiver;
a basic base group sending input,
a basic base group receiving output.
2.2.3 Schematic diagram of supergroup noise test
GB/T4574—1984
Wake up on the road!
Can measure supergroup
Figure 3 Schematic diagram of supergroup noise test
In the figure:
noise source with variable power;
bandpass filter with effective bandwidth B equal to 312～552kHz; center frequency is f. The band-stop filter of
power divider,
a band-pass filter with an effective bandwidth B equal to 812-2044kHz; the supergroup section to be tested,
a receiving band-pass filter with a center frequency of f. and a bandwidth △f of about 2kHz; 8
a receiving variable attenuator;
a root mean square value detection level meter;
a noise generator;
a noise receiver;
a basic supergroup transmission input,
a basic supergroup reception output.
2.3 Test load and its configuration
2.3.1 Calculation formula
When using a uniform spectrum random noise signal to simulate busy-hour multi-channel signal load (i.e., intermodulation noise calculation load), the average absolute power level at the zero relative level point is calculated according to the following formula:
101gP(n)=(-15+101gn)dBm0
10lgP(n)=(-1+4lgn)dBm0
Where: P(n)
-random noise power in milliwatts;
-number of telephone channels.
2.3.2 Load configuration when measuring the noise of the circuit (established on a line chain); a. No load is added to the measured channel;
b. Each of the two adjacent channels is -15dBm0; c. Each of the remaining 9 channels is -6.4dBm0;
d. The remaining fundamental groups
—3.1dBm0,
12n<240
e. The remaining supergroups +2.3dBm0,
f. The remaining main groups +9.8dBm0;
GB/T4574—1984
g. The line chain load is calculated according to the system capacity according to the formula given in Section 2.3.1, plus the load increase of the main group where the measured channel is located. 2.3.3 Load configuration for measuring the noise of the primary group section (established on a line chain) a. Measured primary group +3.3dBm0;
—3.1dBm0;
b. Remaining primary groups
c. Remaining super groups
+2.3dBm0;
d. Remaining main groups +9.8dBm0
e. The line chain load is calculated according to the system capacity according to the formula given in Section 2.3.1, plus the load increase of the main group where the measured primary group is located.
2.3.4 Load configuration when measuring the noise of the supergroup section (established on a line chain) a. Supergroup being measured + 6.1dBm0;
+2.3dBm0,
b. Other supergroups
c. Other main groups + 9.8dBm0;
d. The line chain load is calculated based on the system capacity according to the formula given in Section 2.3.1, plus the load increase value of the main group where the supergroup being measured is located.
2.4 Test frequency of basic group segment and super group segment
Test frequency is specified as follows:
Basic group segment to be tested
2.5 Measurement method
2.5.1 Circuit noise measurement
Frequency band range
60~108
312~552
Test frequency
331,534
2.5.1.1 Connect the circuit according to the test principle diagram 1. Use unrelated white noise sources for each channel of the tested circuit group. 2.5.1.2 After the channel white noise signal passes through the conventional telephone signal shaping network, it is sent to the transmission input end of each channel of the tested group according to the load configuration specified in 2.3.2. The transmission input end of the tested channel is terminated with a 600Q resistor. The remaining groups in the same supergroup, and the remaining supergroups and the remaining main groups in the same main group are all configured with the load specified in 2.3.2, and the noise signals of the corresponding frequency bands are sent to the transmission input ends of GDF (group interface point), SDF (supergroup interface point) and MDF (main group interface point). 2.5.1.3 Use a noise tester (such as QP-670I) with telephone weighting and an integration time of 200ms to measure at the receiving output end of the tested circuit channel. The absolute power level (or voltage) of the noise meter of the tested circuit can be measured. The receiving output terminal of the basic group of the tested basic group is 600Q resistor. The receiving outputs of the remaining fundamental groups, super groups and main groups are terminated with 150 and 752 resistors respectively.
2.5.2 Measurement of the noise power ratio of the fundamental group
2.5.2.1 Connect the circuit according to the fundamental group noise test principle diagram 2. The fundamental group uses a bandpass filter with an effective bandwidth B equal to 60~108kHz. The remaining super groups and main groups use bandpass filters with effective bandwidths B equal to 312~552kHz and 812~2044kHz respectively. The output impedance of the noise generator is balanced 1502 and unbalanced 752 respectively. 2.5.2.2 According to the load configuration provisions of Section 2.3.3, send the noise signal to the corresponding transmitting input terminals of the measured fundamental group, the remaining fundamental groups, the super groups and the main group respectively. The noise signals of the measured fundamental group and the remaining fundamental groups, the super groups and the main group should be unrelated. The load is measured with a broadband RMS detection level meter.
GB/T4574—1984
2.5.2.3 The band-stop filter in the noise generator is not connected to the circuit for the time being. The noise receiver is connected to the band-pass filter of the test frequency, and is connected to the output of the measured base group with a 150Ω balanced input impedance for measurement. The noise power ratio (NPR) when the noise receiver is connected to the band-pass filter of different frequencies (only one is connected at a time) and the noise generator is connected to the band-stop filter of the corresponding frequency is measured. At the receiving end, the receiving outputs of the remaining base group, super group and main group are terminated with 150Ω and 75Ω resistors respectively. 2.5.3 Super group noise power ratio measurement
2.5.3.1 Connect the circuit according to the super group noise test principle diagram 3. The super group uses a band-pass filter with an effective bandwidth B equal to 312~552kH. The output impedance of the noise generator is unbalanced 752. 2.5.3.2 According to the load configuration provisions of 2.3.4, send the noise signal to the corresponding transmission input terminals of the supergroup under test, the remaining supergroups and the main group. The noise signals of the supergroup under test should be unrelated to those of the remaining supergroups and the main group. The load is measured using a wideband RMS detection level meter. 2.5.3.3 The band-stop filter in the noise generator is not connected to the circuit for the time being. The noise receiver is connected to the band-pass filter of the test frequency and connected to the receiving output terminal of the supergroup under test with a 75Ω unbalanced input impedance for measurement. Measure the noise power ratio (NPR) when the noise receiver is connected to the band-pass filter of different frequencies (only one is connected at a time) and the noise generator is connected to the band-stop filter of the corresponding frequency. At the receiving end, the receiving outputs of the remaining supergroups and the main group are terminated with 75Ω resistors. 2.5.4 Direct measurement of weighted noise power level The measurement circuit requirements are the same as Figures 2 and 3. The noise generator is connected to the test frequency band-stop filter. However, a noise receiver with an equivalent noise bandwidth Af equal to 1.74 kHz (equal to 3.1 kHz × 10-0.25) or a frequency-selective level meter of the corresponding measurement frequency band should be selected for measurement. The noise level measured by the frequency-selective level meter should be deducted by the weighted value 1011.74 of the equivalent noise bandwidth B (kH) of the frequency-selective level meter, that is, B
weighted noise power level is equal to the value measured by the frequency-selective level meter minus 10181.74B
2.6 Noise power level calculation
According to 2.5.2 and 2.5.3, the noise power ratio (NPR) can be measured. The noise meter power level Pn of the 3.1 kHz bandwidth at the zero relative level point can be obtained from the noise power ratio.
Base group section:
P.=-NPR—11.1dBmoP
Super group section:
P.=-NPR-15.3dBm0P
3The circuit noise test method simulating system load mentioned above is also applicable to measuring the noise generated by the frequency division multiplexing system's channel, base group, super group and other frequency conversion devices.
The tested circuit, the tested base group section and the tested super group section in Figure 1, Figure 2 and Figure 3 are replaced by the channel frequency conversion device, the base group frequency conversion device and the super group frequency conversion device respectively.
A.1 Requirements for noise generator
A.1.1 Noise signal characteristics
GB/T4574—1984
Appendix A
Main characteristics requirements of white noise test equipment (supplement)
The ratio of peak value to effective value shall not be less than 12dB. A.1.2 Noise spectrum uniformity
Within the effective bandwidth of the bandpass filter, the voltage change of the effective value of the white noise spectrum measured with a frequency band of about 2kHz should not exceed ±0.5dB.
A.2 Conventional telephone signal shaping network
The relative frequency response curve requirements of the conventional telephone signal shaping network are shown in Figure A1. n
Xin Xin H2
A.3 Main characteristics of noise tester
A.3.1 Detector characteristics
Use root mean square detection (also known as square law detection or effective value detection). A.3.2 Weighting network characteristics of noise tester
The characteristic curve requirements of the weighting network are shown in Figure A2. an
Fap100
A.4 Test band pass filter characteristics requirements The characteristics requirements of the band pass filter are shown in Table A1. Test frequency band
GB/T4574—1984
5 6 7 H10
Following H2
Effective
Cut-off frequency and its allowable
error of bandpass filter (kHz）
Basic fundamental group
Basic supergroup
Basic main group
60-108
312~552
812~2044
A.5 Test frequency bandstop filter characteristic requirements 61±2
320±8
840±16
107±2
546±10
2004±30
Pass resistance Out-of-band frequency bands with attenuation difference greater than 75dB
(kHz)
Below passband
Above passband
116~1200
577~8500
2318~26000
The attenuation below and above these frequency bands decreases at a slope of
6dB per octave
*The definition of nominal effective cutoff frequency is: Assuming a filter with an ideal rectangular cutoff characteristic, its power transmission capacity is the same as that of an actual filter, then the cutoff frequency of this ideal filter is called the nominal effective cutoff frequency. 8
The characteristic requirements of the band-stop filter are shown in Table A2. GB/T4574—1984
Relative to f. The attenuation of the center frequency
f(kHz)
(kHz) at the following bandwidth should at least reach the value
white noise tester sensitivity requirements
relative to f. The attenuation of
(kHz) outside the following bandwidth should not exceed the value
When the noise receiver is directly connected to the noise generator, under normal load conditions, when the band stop filter is bypassed, the ratio of the noise power indicated by the noise receiver to the noise power indicated when the band stop filter is connected should be no less than 67dB. Additional notes:
This standard was proposed by the Ministry of Posts and Telecommunications and is under the jurisdiction of the Telecommunications Transmission Research Institute of the Ministry of Posts and Telecommunications. This standard was drafted by the Telecommunications Transmission Research Institute of the Ministry of Posts and Telecommunications. The main drafters of this standard are Zhao Xiaozhu, Luo Jianguo, and Zhang Youlan. 93 Use a noise tester (such as QP-670I) with telephone weighting and 200ms integration time to measure at the receiving output terminal of the circuit under test. The absolute power level (or voltage) of the noise meter of the circuit under test can be measured. The receiving output terminal of the base residual channel of the tested base group is 600Ω resistor. The receiving outputs of the remaining base groups, super groups and main groups are terminated with 150 and 752 resistors respectively.
2.5.2 Measurement of base group noise power ratio
2.5.2.1 Connect the circuit according to the principle diagram 2 of the base group noise test. The base group uses a bandpass filter with an effective bandwidth B equal to 60~108kHz. The remaining super groups and main groups use bandpass filters with effective bandwidth B equal to 312~552kHz and 812~2044kHz respectively. The output impedance of the noise generator is 150Ω for balanced type and 75Ω for unbalanced type. 2.5.2.2 According to the load configuration provisions of 2.3.3, send the noise signal to the corresponding transmission input terminals of the tested fundamental group, the remaining fundamental groups, the super group and the main group respectively. The noise signals of the tested fundamental group and the remaining fundamental groups, the super group and the main group should be unrelated. The load is measured with a wideband RMS detection level meter.
GB/T4574—1984
2.5.2.3 The band-stop filter in the noise generator is not connected to the circuit for the time being. The noise receiver is connected to the band-pass filter of the test frequency and connected to the receiving output terminal of the tested fundamental group with a 150Ω balanced input impedance for measurement. The noise power ratio (NPR) when the noise receiver is connected to the band-pass filter of different frequencies (only one is connected at a time) and the noise generator is connected to the band-stop filter of the corresponding frequency is measured. At the receiving end, the receiving outputs of the remaining fundamental groups, the super group and the main group are terminated with 150Ω and 75Ω resistors respectively. 2.5.3 Supergroup noise power ratio measurement
2.5.3.1 Connect the circuit according to the supergroup noise test principle diagram 3. The supergroup uses a bandpass filter with an effective bandwidth B equal to 312~552kH. The output impedance of the noise generator is unbalanced 752.2.5.3.2 According to the load configuration provisions of 2.3.4, send the noise signal to the corresponding transmission input terminals of the supergroup under test, the remaining supergroups and the main group respectively. The noise signals of the supergroup under test and the remaining supergroups and the main group should be unrelated. The load is measured using a wideband RMS detection level meter. 2.5.3.3 The bandstop filter in the noise generator is not connected to the circuit for the time being. The noise receiver is connected to the bandpass filter of the test frequency and connected to the receiving output terminal of the supergroup under test with a 75Q unbalanced input impedance for measurement. Measure the noise power ratio (NPR) when the noise receiver is connected to the bandpass filter of different frequencies (only one is connected at a time) and the noise generator is connected to the bandstop filter of the corresponding frequency. At the receiving end, the receiving outputs of the remaining supergroups and the main group are terminated with 75Q resistors respectively. 2.5.4 Direct measurement of weighted noise power level The measurement circuit requirements are the same as those in Figures 2 and 3. The noise generator is connected to the test frequency band-stop filter. However, a noise receiver with an equivalent noise bandwidth Af equal to 1.74kH (equal to 3.1kH×10-0.25) or a frequency-selective level meter of the corresponding measurement frequency band should be selected for measurement. The noise level measured by the frequency-selective level meter should be deducted by the weighted value 1011.74 of the equivalent noise bandwidth B (kH) of the frequency-selective level meter, that is, B
The weighted noise power level is equal to the value measured by the frequency-selective level meter minus 10181.74B
2.6 Noise power level calculation
According to 2.5.2 and 2.5.3, the noise power ratio (NPR) can be measured. The noise meter power level Pn of the 3.1kH bandwidth at the zero relative level point can be obtained from the noise power ratio.
Base group section:
P.=-NPR—11.1dBmoP
Super group section:
P.=-NPR-15.3dBm0P
3The circuit noise test method simulating system load mentioned above is also applicable to measuring the noise generated by the frequency division multiplexing system's channel, base group, super group and other frequency conversion devices.
The tested circuit, the tested base group section and the tested super group section in Figure 1, Figure 2 and Figure 3 are replaced by the channel frequency conversion device, the base group frequency conversion device and the super group frequency conversion device respectively.
A.1 Requirements for noise generator
A.1.1 Noise signal characteristics
GB/T4574—1984
Appendix A
Main characteristics requirements of white noise test equipment (supplement)
The ratio of peak value to effective value shall not be less than 12dB. A.1.2 Noise spectrum uniformity
Within the effective bandwidth of the bandpass filter, the voltage change of the effective value of the white noise spectrum measured with a frequency band of about 2kHz should not exceed ±0.5dB.
A.2 Conventional telephone signal shaping network
The relative frequency response curve requirements of the conventional telephone signal shaping network are shown in Figure A1. n
Xin Xin H2
A.3 Main characteristics of noise tester
A.3.1 Detector characteristics
Use root mean square detection (also known as square law detection or effective value detection). A.3.2 Weighting network characteristics of noise tester
The characteristic curve requirements of the weighting network are shown in Figure A2. an
Fap100
A.4 Test band pass filter characteristics requirements The characteristics requirements of the band pass filter are shown in Table A1. Test frequency band
GB/T4574—1984
5 6 7 H10
Following H2
Effective
Cut-off frequency and its allowable
error of bandpass filter (kHz）
Basic fundamental group
Basic supergroup
Basic main group
60-108
312~552
812~2044
A.5 Test frequency bandstop filter characteristic requirements 61±2
320±8
840±16
107±2
546±10
2004±30
Pass resistance Out-of-band frequency bands with attenuation difference greater than 75dB
(kHz)
Below passband
Above passband
116~1200
577~8500
2318~26000
The attenuation below and above these frequency bands decreases at a slope of
6dB per octave
*The definition of nominal effective cutoff frequency is: Assuming a filter with an ideal rectangular cutoff characteristic, its power transmission capacity is the same as that of an actual filter, then the cutoff frequency of this ideal filter is called the nominal effective cutoff frequency. 8
The characteristic requirements of the band-stop filter are shown in Table A2. GB/T4574—1984
Relative to f. The attenuation of the center frequency
f(kHz)
(kHz) at the following bandwidth should at least reach the value
white noise tester sensitivity requirements
relative to f. The attenuation of
(kHz) outside the following bandwidth should not exceed the value
When the noise receiver is directly connected to the noise generator, under normal load conditions, when the band stop filter is bypassed, the ratio of the noise power indicated by the noise receiver to the noise power indicated when the band stop filter is connected should be no less than 67dB. Additional notes:
This standard was proposed by the Ministry of Posts and Telecommunications and is under the jurisdiction of the Telecommunications Transmission Research Institute of the Ministry of Posts and Telecommunications. This standard was drafted by the Telecommunications Transmission Research Institute of the Ministry of Posts and Telecommunications. The main drafters of this standard are Zhao Xiaozhu, Luo Jianguo, and Zhang Youlan. 93 Use a noise tester (such as QP-670I) with telephone weighting and 200ms integration time to measure at the receiving output terminal of the circuit under test. The absolute power level (or voltage) of the noise meter of the circuit under test can be measured. The receiving output terminal of the base residual channel of the tested base group is 600Ω resistor. The receiving outputs of the remaining base groups, super groups and main groups are terminated with 150 and 752 resistors respectively.
2.5.2 Measurement of base group noise power ratio
2.5.2.1 Connect the circuit according to the principle diagram 2 of the base group noise test. The base group uses a bandpass filter with an effective bandwidth B equal to 60~108kHz. The remaining super groups and main groups use bandpass filters with effective bandwidth B equal to 312~552kHz and 812~2044kHz respectively. The output impedance of the noise generator is 150Ω for balanced type and 75Ω for unbalanced type. 2.5.2.2 According to the load configuration provisions of 2.3.3, send the noise signal to the corresponding transmission input terminals of the tested fundamental group, the remaining fundamental groups, the super group and the main group respectively. The noise signals of the tested fundamental group and the remaining fundamental groups, the super group and the main group should be unrelated. The load is measured with a wideband RMS detection level meter.
GB/T4574—1984
2.5.2.3 The band-stop filter in the noise generator is not connected to the circuit for the time being. The noise receiver is connected to the band-pass filter of the test frequency and connected to the receiving output terminal of the tested fundamental group with a 150Ω balanced input impedance for measurement. The noise power ratio (NPR) when the noise receiver is connected to the band-pass filter of different frequencies (only one is connected at a time) and the noise generator is connected to the band-stop filter of the corresponding frequency is measured. At the receiving end, the receiving outputs of the remaining fundamental groups, the super group and the main group are terminated with 150Ω and 75Ω resistors respectively. 2.5.3 Supergroup noise power ratio measurement
2.5.3.1 Connect the circuit according to the supergroup noise test principle diagram 3. The supergroup uses a bandpass filter with an effective bandwidth B equal to 312~552kH. The output impedance of the noise generator is unbalanced 752.2.5.3.2 According to the load configuration provisions of 2.3.4, send the noise signal to the corresponding transmission input terminals of the supergroup under test, the remaining supergroups and the main group respectively. The noise signals of the supergroup under test and the remaining supergroups and the main group should be unrelated. The load is measured using a wideband RMS detection level meter. 2.5.3.3 The bandstop filter in the noise generator is not connected to the circuit for the time being. The noise receiver is connected to the bandpass filter of the test frequency and connected to the receiving output terminal of the supergroup under test with a 75Q unbalanced input impedance for measurement. Measure the noise power ratio (NPR) when the noise receiver is connected to the bandpass filter of different frequencies (only one is connected at a time) and the noise generator is connected to the bandstop filter of the corresponding frequency. At the receiving end, the receiving outputs of the remaining supergroups and the main group are terminated with 75Q resistors respectively. 2.5.4 Direct measurement of weighted noise power level The measurement circuit requirements are the same as those in Figures 2 and 3. The noise generator is connected to the test frequency band-stop filter. However, a noise receiver with an equivalent noise bandwidth Af equal to 1.74kH (equal to 3.1kH×10-0.25) or a frequency-selective level meter of the corresponding measurement frequency band should be selected for measurement. The noise level measured by the frequency-selective level meter should be deducted by the weighted value 1011.74 of the equivalent noise bandwidth B (kH) of the frequency-selective level meter, that is, B
The weighted noise power level is equal to the value measured by the frequency-selective level meter minus 10181.74B
2.6 Noise power level calculation
According to 2.5.2 and 2.5.3, the noise power ratio (NPR) can be measured. The noise meter power level Pn of the 3.1kH bandwidth at the zero relative level point can be obtained from the noise power ratio.
Base group section:
P.=-NPR—11.1dBmoP
Super group section:
P.=-NPR-15.3dBm0P
3The circuit noise test method simulating system load mentioned above is also applicable to measuring the noise generated by the frequency division multiplexing system's channel, base group, super group and other frequency conversion devices.
The tested circuit, the tested base group section and the tested super group section in Figure 1, Figure 2 and Figure 3 are replaced by the channel frequency conversion device, the base group frequency conversion device and the super group frequency conversion device respectively.
A.1 Requirements for noise generator
A.1.1 Noise signal characteristics
GB/T4574—1984
Appendix A
Main characteristics requirements of white noise test equipment (supplement)
The ratio of peak value to effective value shall not be less than 12dB. A.1.2 Noise spectrum uniformity
Within the effective bandwidth of the bandpass filter, the voltage change of the effective value of the white noise spectrum measured with a frequency band of about 2kHz should not exceed ±0.5dB.
A.2 Conventional telephone signal shaping network
The relative frequency response curve requirements of the conventional telephone signal shaping network are shown in Figure A1. n
Xin Xin H2
A.3 Main characteristics of noise tester
A.3.1 Detector characteristics
Use root mean square detection (also known as square law detection or effective value detection). A.3.2 Weighting network characteristics of noise tester
The characteristic curve requirements of the weighting network are shown in Figure A2. an
Fap100
A.4 Test band pass filter characteristics requirements The characteristics requirements of the band pass filter are shown in Table A1. Test frequency band
GB/T4574—1984
5 6 7 H10
Following H2
Effective
Cut-off frequency and its allowable
error of bandpass filter (kHz）
Basic fundamental group
Basic supergroup
Basic main group
60-108
312~552
812~2044
A.5 Test frequency bandstop filter characteristic requirements 61±2
320±8
840±16
107±2
546±10
2004±30
Pass resistance Out-of-band frequency bands with attenuation difference greater than 75dB
(kHz)
Below passband
Above passband
116~1200
577~8500
2318~26000
The attenuation below and above these frequency bands decreases at a slope of
6dB per octave
*The definition of nominal effective cutoff frequency is: Assuming a filter with an ideal rectangular cutoff characteristic, its power transmission capacity is the same as that of an actual filter, then the cutoff frequency of this ideal filter is called the nominal effective cutoff frequency. 8
The characteristic requirements of the band-stop filter are shown in Table A2. GB/T4574—1984
Relative to f. The attenuation of the center frequency
f(kHz)
(kHz) at the following bandwidth should at least reach the value
white noise tester sensitivity requirements
relative to f. The attenuation of
(kHz) outside the following bandwidth should not exceed the value
When the noise receiver is directly connected to the noise generator, under normal load conditions, when the band stop filter is bypassed, the ratio of the noise power indicated by the noise receiver to the noise power indicated when the band stop filter is connected should be no less than 67dB. Additional notes:
This standard was proposed by the Ministry of Posts and Telecommunications and is under the jurisdiction of the Telecommunications Transmission Research Institute of the Ministry of Posts and Telecommunications. This standard was drafted by the Telecommunications Transmission Research Institute of the Ministry of Posts and Telecommunications. The main drafters of this standard are Zhao Xiaozhu, Luo Jianguo, and Zhang Youlan. 93 The band-stop filter in the noise generator is not connected to the circuit for the time being. The noise receiver is connected to the band-pass filter of the test frequency, and connected to the receiving output of the measured basic group with a 150Ω balanced input impedance for measurement. The noise power ratio (NPR) when the noise receiver is connected to the band-pass filter of different frequencies (only one is connected at a time) and the noise generator is connected to the band-stop filter of the corresponding frequency is measured. At the receiving end, the receiving outputs of the remaining basic group, super group and main group are terminated with 150Ω and 75Ω resistors respectively. 2.5.3 Super group noise power ratio measurement
2.5.3.1 Connect the circuit according to the super group noise test principle diagram 3. The super group uses a band-pass filter with an effective bandwidth B equal to 312~552kH. The output impedance of the noise generator is an unbalanced 752.2.5.3.2 According to the load configuration provisions of Section 2.3.4, send the noise signal to the corresponding transmitting input terminals of the measured super group, the remaining super groups and the main group respectively. The noise signals of the measured supergroup should be uncorrelated with those of the remaining supergroups and the main group. The load is measured using a wideband RMS detection level meter. 2.5.3.3 The band-stop filter in the noise generator is not connected to the circuit for the time being. The noise receiver is connected to the band-pass filter of the test frequency and connected to the receiving output of the measured supergroup with a 75Ω unbalanced input impedance for measurement. The noise power ratio (NPR) when the noise receiver is connected to the band-pass filter of different frequencies (only one is connected at a time) and the noise generator is connected to the band-stop filter of the corresponding frequency is measured. At the receiving end, the receiving outputs of the remaining supergroups and the main group are terminated with 75Ω resistors respectively. 2.5.4 Direct measurement of weighted noise power level The measurement circuit requirements are the same as those in Figures 2 and 3. The noise generator is connected to the band-stop filter of the test frequency. However, a noise receiver with an equivalent noise bandwidth Af equal to 1.74kH (equal to 3.1kH×10-0.25) or a frequency-selective level meter of the corresponding measurement frequency band should be selected for measurement. The noise level measured by the frequency-selective level meter should be deducted from the weighted value 1011.74 of the equivalent noise bandwidth B (kH) of the frequency-selective level meter, that is, B
The weighted noise power level is equal to the value measured by the frequency-selective level meter minus 10181.74B
2.6 Noise power level calculation
According to 2.5.2 and 2.5.3, the noise power ratio (NPR) can be measured. The noise meter power level Pn of the 3.1kH bandwidth at the zero relative level point can be obtained from the noise power ratio.
Basic group section:
P.=-NPR—11.1dBm0P
Super group section:
P.=-NPR-15.3dBm0P
3The circuit noise test method for simulating system load is also applicable to measuring the noise generated by frequency conversion equipment such as channels, basic groups, and super groups of frequency division multiplexing systems.
The circuit under test, the fundamental group section under test, and the supergroup section under test in Figures 1, 2, and 3 are replaced by channel frequency conversion equipment, fundamental group frequency conversion equipment, and supergroup frequency conversion equipment, respectively.
A.1 Requirements for noise generators
A.1.1 Noise signal characteristics
GB/T4574—1984
Appendix A
Main characteristics requirements for white noise test equipment (supplementary)
The ratio of peak value to effective value shall not be less than 12dB. A.1.2 Noise spectrum uniformity
Within the effective bandwidth of the bandpass filter, using a frequency band of about 2kHz, the voltage change of the effective value of the white noise spectrum measured shall not exceed ±0.5dB.
A.2 Conventional telephone signal shaping network
The relative frequency response curve requirements of the conventional telephone signal shaping network are shown in Figure A1. n
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A.3 Main characteristics of noise tester
A.3.1 Detector characteristics
Use RMS detection (also called square law detection or effective value detection). A.3.2 Weighted network characteristics of noise tester
The characteristic curve of weighted network is shown in Figure A2. an
Fap100
A.4 Characteristics of bandpass filter in test frequency band The characteristics of bandpass filter are shown in Table A1. Test frequency band
GB/T4574—1984
5 6 7 H10
Following H2
Effective
Cut-off frequency and allowable
error of band-pass filter (kHz)
Basic fundamental group
Basic supergroup
Basic main group
60-108
312~552
812~2044
A.5 Test frequency Band-stop filter characteristic requirements 61±2
320±8
840±16
107±2
546±10
2004±30
Pass-stop Out-of-band frequency bands with attenuation difference greater than 75dB
(kHz)
Below passband
Above passband
116~1200
577~8500
2318~26000
The attenuation below and above these frequency bands decreases at a slope of
6dB per octave
*The definition of nominal effective cutoff frequency is: Assuming a filter with an ideal rectangular cutoff characteristic, its power transmission capacity is the same as that of an actual filter, then the cutoff frequency of this ideal filter is called the nominal effective cutoff frequency. 8
The characteristic requirements of the band-stop filter are shown in Table A2. GB/T4574—1984
Relative to f. The attenuation of the center frequency
f(kHz)
(kHz) at the following bandwidth should at least reach the value
white noise tester sensitivity requirements
relative to f. The attenuation of
(kHz) outside the following bandwidth should not exceed the value
When the noise receiver is directly connected to the noise generator, under normal load conditions, when the band stop filter is bypassed, the ratio of the noise power indicated by the noise receiver to the noise power indicated when the band stop filter is connected should be no less than 67dB. Additional notes:
This standard was proposed by the Ministry of Posts and Telecommunications and is under the jurisdiction of the Telecommunications Transmission Research Institute of the Ministry of Posts and Telecommunications. This standard was drafted by the Telecommunications Transmission Research Institute of the Ministry of Posts and Telecommunications. The main drafters of this standard are Zhao Xiaozhu, Luo Jianguo, and Zhang Youlan. 93 The band-stop filter in the noise generator is not connected to the circuit for the time being. The noise receiver is connected to the band-pass filter of the test frequency, and connected to the receiving output of the measured basic group with a 150Ω balanced input impedance for measurement. The noise power ratio (NPR) when the noise receiver is connected to the band-pass filter of different frequencies (only one is connected at a time) and the noise generator is connected to the band-stop filter of the corresponding frequency is measured. At the receiving end, the receiving outputs of the remaining basic group, super group and main group are terminated with 150Ω and 75Ω resistors respectively. 2.5.3 Super group noise power ratio measurement
2.5.3.1 Connect the circuit according to the super group noise test principle diagram 3. The super group uses a band-pass filter with an effective bandwidth B equal to 312~552kH. The output impedance of the noise generator is an unbalanced 752.2.5.3.2 According to the load configuration provisions of Section 2.3.4, send the noise signal to the corresponding transmitting input terminals of the measured super group, the remaining super groups and the main group respectively. The noise signals of the measured supergroup should be uncorrelated with those of the remaining supergroups and the main group. The load is measured using a wideband RMS detection level meter. 2.5.3.3 The band-stop filter in the noise generator is not connected to the circuit for the time being. The noise receiver is connected to the band-pass filter of the test frequency and connected to the receiving output of the measured supergroup with a 75Ω unbalanced input impedance for measurement. The noise power ratio (NPR) when the noise receiver is connected to the band-pass filter of different frequencies (only one is connected at a time) and the noise generator is connected to the band-stop filter of the corresponding frequency is measured. At the receiving end, the receiving outputs of the remaining supergroups and the main group are terminated with 75Ω resistors respectively. 2.5.4 Direct measurement of weighted noise power level The measurement circuit requirements are the same as those in Figures 2 and 3. The noise generator is connected to the band-stop filter of the test frequency. However, a noise receiver with an equivalent noise bandwidth Af equal to 1.74kH (equal to 3.1kH×10-0.25) or a frequency-selective level meter of the corresponding measurement frequency band should be selected for measurement. The noise level measured by the frequency-selective level meter should be deducted from the weighted value 1011.74 of the equivalent noise bandwidth B (kH) of the frequency-selective level meter, that is, B
The weighted noise power level is equal to the value measured by the frequency-selective level meter minus 10181.74B
2.6 Noise power level calculation
According to 2.5.2 and 2.5.3, the noise power ratio (NPR) can be measured. The noise meter power level Pn of the 3.1kH bandwidth at the zero relative level point can be obtained from the noise power ratio.
Basic group section:
P.=-NPR—11.1dBm0P
Super group section:
P.=-NPR-15.3dBm0P
3The circuit noise test method for simulating system load is also applicable to measuring the noise generated by frequency conversion equipment such as channels, basic groups, and super groups of frequency division multiplexing systems.
The circuit under test, the fundamental group section under test, and the supergroup section under test in Figures 1, 2, and 3 are replaced by channel frequency conversion equipment, fundamental group frequency conversion equipment, and supergroup frequency conversion equipment, respectively.
A.1 Requirements for noise generators
A.1.1 Noise signal characteristics
GB/T4574—1984
Appendix A
Main characteristics requirements for white noise test equipment (supplementary)
The ratio of peak value to effective value shall not be less than 12dB. A.1.2 Noise spectrum uniformity
Within the effective bandwidth of the bandpass filter, using a frequency band of about 2kHz, the voltage change of the effective value of the white noise spectrum measured shall not exceed ±0.5dB.
A.2 Conventional telephone signal shaping network
The relative frequency response curve requirements of the conventional telephone signal shaping network are shown in Figure A1. n
Xin Xin H2www.bzxz.net
A.3 Main characteristics of noise tester
A.3.1 Detector characteristics
Use RMS detection (also called square law detection or effective value detection). A.3.2 Weighted network characteristics of noise tester
The characteristic curve of weighted network is shown in Figure A2. an
Fap100
A.4 Characteristics of bandpass filter in test frequency band The characteristics of bandpass filter are shown in Table A1. Test frequency band
GB/T4574—1984
5 6 7 H10
Following H2
Effective
Cut-off frequency and allowable
error of band-pass filter (kHz)
Basic fundamental group
Basic supergroup
Basic main group
60-108
312~552
812~2044
A.5 Test frequency Band-stop filter characteristic requirements 61±2
320±8
840±16
107±2
546±10
2004±30
Pass-stop Out-of-band frequency bands with attenuation difference greater than 75dB
(kHz)
Below passband
Above passband
116~1200
577~8500
2318~26000
The attenuation below and above these frequency bands decreases at a slope of
6dB per octave
*The definition of nominal effective cutoff frequency is: Assuming a filter with an ideal rectangular cutoff characteristic, its power transmission capacity is the same as that of an actual filter, then the cutoff frequency of this ideal filter is called the nominal effective cutoff frequency. 8
The characteristic requirements of the band-stop filter are shown in Table A2. GB/T4574—1984
Relative to f. The attenuation of the center frequency
f(kHz)
(kHz) at the following bandwidth should at least reach the value
white noise tester sensitivity requirements
relative to f. The attenuation of
(kHz) outside the following bandwidth should not exceed the value
When the noise receiver is directly connected to the noise generator, under normal load conditions, when the band stop filter is bypassed, the ratio of the noise power indicated by the noise receiver to the noise power indicated when the band stop filter is connected should be no less than 67dB. Additional notes:
This standard was proposed by the Ministry of Posts and Telecommunications and is under the jurisdiction of the Telecommunications Transmission Research Institute of the Ministry of Posts and Telecommunications. This standard was drafted by the Telecommunications Transmission Research Institute of the Ministry of Posts and Telecommunications. The main drafters of this standard are Zhao Xiaozhu, Luo Jianguo, and Zhang Youlan. 91 Requirements for noise generator
A.1.1 Noise signal characteristics
GB/T4574—1984
Appendix A
Main characteristics requirements for white noise test equipment (supplement)
The ratio of peak value to effective value shall not be less than 12dB. A.1.2 Noise spectrum uniformity
Within the effective bandwidth of the bandpass filter, the voltage change of the effective value of the white noise spectrum measured with a frequency band of about 2kHz shall not exceed ±0.5dB.
A.2 Conventional telephone signal shaping network
The relative frequency response curve requirements of the conventional telephone signal shaping network are shown in Figure A1. n
New Xin H2
A.3 Main characteristics requirements for noise tester
A.3.1 Detector characteristics
Use root mean square value detection (also known as square law detection or effective value detection). A.3.2 Noise tester weighted network characteristics
The characteristic curve requirements of the weighted network are shown in Figure A2. an
Fap100
A.4 Test band bandpass filter characteristics requirements The characteristics requirements of the bandpass filter are shown in Table A1. Test band
GB/T4574—1984
5 6 7 H10
Following H2
Effective
Cut-off frequency and allowable
error of band-pass filter (kHz)
Basic fundamental group
Basic supergroup
Basic main group
60-108
312~552
812~2044
A.5 Test frequency Band-stop filter characteristic requirements 61±2
320±8
840±16
107±2
546±10
2004±30
Pass-stop Out-of-band frequency bands with attenuation difference greater than 75dB
(kHz)
Below passband
Above passband
116~1200
577~8500
2318~26000
The attenuation below and above these frequency bands decreases at a slope of
6dB per octave
*The definition of nominal effective cutoff frequency is: Assuming a filter with an ideal rectangular cutoff characteristic, its power transmission capacity is the same as that of an actual filter, then the cutoff frequency of this ideal filter is called the nominal effective cutoff frequency. 8
The characteristic requirements of the band-stop filter are shown in Table A2. GB/T4574—1984
Relative to f. The attenuation of the center frequency
f(kHz)
(kHz) at the following bandwidth should at least reach the value
white noise tester sensitivity requirements
relative to f. The attenuation of
(kHz) outside the following bandwidth should not exceed the value
When the noise receiver is directly connected to the noise generator, under normal load conditions, when the band stop filter is bypassed, the ratio of the noise power indicated by the noise receiver to the noise power indicated when the band stop filter is connected should be no less than 67dB. Additional notes:
This standard was proposed by the Ministry of Posts and Telecommunications and is under the jurisdiction of the Telecommunications Transmission Research Institute of the Ministry of Posts and Telecommunications. This standard was drafted by the Telecommunications Transmission Research Institute of the Ministry of Posts and Telecommunications. The main drafters of this standard are Zhao Xiaozhu, Luo Jianguo, and Zhang Youlan. 91 Requirements for noise generator
A.1.1 Noise signal characteristics
GB/T4574—1984
Appendix A
Main characteristics requirements for white noise test equipment (supplement)
The ratio of peak value to effective value shall not be less than 12dB. A.1.2 Noise spectrum uniformity
Within the effective bandwidth of the bandpass filter, the voltage change of the effective value of the white noise spectrum measured with a frequency band of about 2kHz shall not exceed ±0.5dB.
A.2 Conventional telephone signal shaping network
The relative frequency response curve requirements of the conventional telephone signal shaping network are shown in Figure A1. n
New Xin H2
A.3 Main characteristics requirements for noise tester
A.3.1 Detector characteristics
Use root mean square value detection (also known as square law detection or effective value detection). A.3.2 Noise tester weighted network characteristics
The characteristic curve requirements of the weighted network are shown in Figure A2. an
Fap100
A.4 Test band bandpass filter characteristics requirements The characteristics requirements of the bandpass filter are shown in Table A1. Test band
GB/T4574—1984
5 6 7 H10
Following H2
Effective
Cut-off frequency and allowable
error of band-pass filter (kHz)
Basic fundamental group
Basic supergroup
Basic main group
60-108
312~552
812~2044
A.5 Test frequency Band-stop filter characteristic requirements 61±2
320±8
840±16
107±2
546±10
2004±30
Pass-stop Out-of-band frequency bands with attenuation difference greater than 75dB
(kHz)
Below passband
Above passband
116~1200
577~8500
2318~26000
The attenuation below and above these frequency bands decreases at a slope of
6dB per octave
*The definition of nominal effective cutoff frequency is: Assuming a filter with an ideal rectangular cutoff characteristic, its power transmission capacity is the same as that of an actual filter, then the cutoff frequency of this ideal filter is called the nominal effective cutoff frequency. 8
The characteristic requirements of the band-stop filter are shown in Table A2. GB/T4574—1984
Relative to f. The attenuation of the center frequency
f(kHz)
(kHz) at the following bandwidth should at least reach the value
white noise tester sensitivity requirements
relative to f. The attenuation of
(kHz) outside the following bandwidth should not exceed the value
When the noise receiver is directly connected to the noise generator, under normal load conditions, when the band stop filter is bypassed, the ratio of the noise power indicated by the noise receiver to the noise power indicated when the band stop filter is connected should be no less than 67dB. Additional notes:
This standard was proposed by the Ministry of Posts and Telecommunications and is under the jurisdiction of the Telecommunications Transmission Research Institute of the Ministry of Posts and Telecommunications. This standard was drafted by the Telecommunications Transmission Research Institute of the Ministry of Posts and Telecommunications. The main drafters of this standard are Zhao Xiaozhu, Luo Jianguo, and Zhang Youlan. 9
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