GB/T 11298.1-1997 Measurement methods for satellite television earth receiving stations System measurement
Some standard content:
GB/T11298.1-1997
This standard is a revision of GB11298.1-89 "Systematic Measurement of Satellite TV Earth Receiving Station Measurement Methods". The revision strives to be concise and to quote other standards as much as possible. Only Appendix C (supplement) is retained in the original standard appendix, and other appendices are implemented in accordance with the provisions of relevant standards. Due to the development of science and technology, satellite TV dedicated signal sources have been commercialized, so appropriate modifications are made to the start of Figure 3; in addition, since the video channels of the indoor units of satellite TV receivers all have noise band-limiting filters, when testing the image signal-to-noise ratio, no additional band-limiting filters should be added, so the 10kHz~6MHz bandpass filter is removed from the receiving end test equipment in Figure 3. There are some inappropriate words, terms and expressions in the original standard GB11298.1, and this standard has also been revised. This standard is a supporting standard for GB/T11442--95. After the standard is released, it will replace GB11298.1-89 at the same time. Appendix A of this standard is the appendix of the standard.
This standard is proposed by the Ministry of Electronics Industry of the People's Republic of China. This standard is under the jurisdiction of the Standardization Institute of the Ministry of Electronics Industry. The drafting units of this standard are the 54th Institute of the Ministry of Electronics Industry and the Broadcasting Science Research Institute of the Ministry of Radio, Film and Television. The main drafters of this standard are Tian Yi, Han Peixian and Wang Zhishi. This standard was first issued on March 31, 1989 and revised for the first time in August 1997. 1 Scope
National Standard of the People's Republic of China
Methods of measurement for satellitetelevision earth receive-only stationSystem measurement
This standard specifies the system measurement methods for satellitetelevision earth receive-only stationSystem measurement
This standard specifies the system measurement methods for satellitetelevision earth receive-only station. This standard is applicable to the system measurement of analog satellitetelevision earth receive-only stations. 2 Referenced standards
GB/T 11298.1—1997
Replaces GB11298.1 --89
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. At the time of publication of the standard, the versions shown are valid. All standards are subject to revision, and parties using this standard should explore the possibility of using the latest version of the following standards. GB11299.6--89 Satellite communication earth station radio equipment measurement methods Part 2: Subsystem measurement Section 1: Overview Section 2: Antenna (including feed network)
GB 11299.12-89
Satellite communication earth station radio equipment measurement methods Part 3: Subsystem combination measurement Section 2: 4-6GHz receiving system quality factor (G/T) measurement GB/T11442-1995 Satellite TV earth receiving station general technical conditions 3 Measurement conditions
3.1 Atmospheric conditions
Temperature: 15℃~35℃,
Humidity: 45%~75%;
Atmospheric pressure: 86kPa~～106kPa.
3.2 Power supply
Voltage: ~220V±10%;
Frequency: 50Hz±2Hz.
4 Quality factor (G/T)
4.1 General considerations
The quality factor G/T value of a system refers to the absolute gain G of the antenna at a specified frequency and under specified conditions. The ratio of the noise temperature T of the receiving system converted to the entrance of the outdoor unit is usually expressed by formula (1) in units of dB/K. G/T = 10 lg%
4.2 Measurement method
There are two main methods for measuring the quality factor (G/T) value: direct measurement method and indirect measurement method. Approved by the State Administration of Technical Supervision on August 26, 1997 (1)
Implemented on May 1, 1998
GB/T 11298.1—1997
The first method is to use a radio star to directly measure the quality factor (G/T) value according to the measurement method in Chapter 4 of GB11299.12-89.
The second method is the indirect measurement method, that is, to measure the total power gain G of the antenna (including the feed source) and the system noise temperature T, respectively. The antenna power total gain G is measured according to the measurement method in Chapter 8 of GB11299.6-89, and the system noise temperature T is measured according to the measurement method in Chapter 9 of GB11299.6-89, and then the G/T value is calculated. 4.3 Result Representation
Represented by graph or text, or in table. 5 Gain stability
5.1 General considerations
Gain stability refers to the maximum change AGmx of the ratio of the peak-to-peak value L of the video signal amplitude at the output of the device under test to the nominal value L of the amplitude of the test signal input at the transmitting end (700mV peak-to-peak) within a specified time (medium cycle 1h), expressed in dB, see formula (2): AGmax = 20 lgl
Where: L——peak-to-peak value of the video signal at the output of the device under test, mV; nominal value of the amplitude of the input signal at the transmitting end, mV. Lo
5.2 Measurement method
Usually, the measurement of the gain stability of the receiving system is the measurement of the gain stability of the receiver. (2)
a) Connect the measuring equipment as shown in Figure 1, and send the step wave test signal (see Figure 2) with a constant level (1V (pp)) and an average picture level (APL) of 50% output by the test signal source to the receiving system under test after modulation by the transmitting equipment; b) Measure the output level at the video output end of the receiver at a certain time interval. Measure continuously for one hour, and substitute the maximum value L of the measured video level into formula (2) for calculation. Receiver under test
Coupler
Attenuator
Up-converter
System gain stability measurement
Waveform monitor
Test signal
Generator
[Transmitting end
5.3 Result representation
Represent in a diagram or explain in words.
6 Image signal-to-noise ratio
6.1 General considerations
-300mV
GB/T11298.1-1997
Figure 2 Average image level is 50% step wave model D The image signal-to-noise ratio S/N (dB) is the ratio of the nominal value of the brightness signal amplitude to the effective value of the random noise amplitude measured after bandwidth limitation. It is calculated according to formula (3):
. Nominal value of brightness signal amplitude [700mV(pp)] S/N = 20 lg
Effective value of random noise amplitude
.6.2 Measurement method
(3)
a) Point the antenna to the cold sky and connect the measuring equipment according to Figure 3. Set switches S1Sz, S3, S, Ss to position "1" respectively. At this time, the antenna and the outdoor unit act as noise sources;
b) Correct the carrier-to-noise ratio C/N to odB.
Disconnect the automatic gain control (AGC) and use the output end of the indoor unit intermediate frequency amplifier as the test point. When calibrating, add noise only without adding signal. Adjust the attenuator, change the input noise power, and record the power meter reading "P". Pay attention to keep the system working linearly. Then set S to 2\ to remove noise. Send only a flat-field signal K (as shown in Figure 4) modulated RF signal to the input end of the indoor unit, adjust its level so that the power meter displays the same reading P", then the noise is equal to the signal power, that is, the carrier-to-noise ratio C/N is equal to 0dB; c) After calibration, set S,Set to "1", change the attenuator value, the noise power decreases by 1dB, and the carrier-to-noise ratio C/N increases by 1dB accordingly, until the carrier-to-noise ratio C/N reaches the specified value (such as 14dB), then remove the power meter and connect the receiver; d) The transmitting device outputs the RF signal modulated by the flat-field signal K according to the specified frequency deviation, adjusts its output video signal level to 1Vp-p) (on a 75α load), then removes the flat-field signal K, and uses a video RMS voltmeter to measure the noise RMS value N at the output end of the receiver; e) Substitute the measured noise RMS value N into formula (3) to calculate and obtain the unweighted signal-to-noise ratio S/N; S: can also be set to 2", and the S/N can be directly measured using an interpolation analyzer,
f) Set switches S and S: to 2" respectively, so that the video output end of the indoor unit is connected to a unified weighted network (see Appendix A (Appendix to the standard), and still use method d to measure the noise RMS value, substitute it into formula (3) to calculate, and obtain the weighted signal-to-noise ratio. Notes
1 Select several representative frequency points within the input frequency band for measurement. 2 When using an outdoor unit as a noise source, point the antenna toward the background sky. 3 When the tuner-demodulator has no intermediate frequency interface, use a standard filter with a 1 GHz bandwidth of 27 MHz or a standard spectrum tuner with an intermediate frequency interface and an intermediate frequency bandwidth of 27 MHz to complete the measurement in item b. 6
Test signal
Generator
Signal generation
Power meter
Analyzer
GB/T11298.11997
Satellite TV signal source
Attenuator
DC block
Indoor unit
Monitor
RMS voltmeter
(or oscilloscope)
(700mV)
350mV-
-300mV
6.3 Result representation
Express in words or in diagrams.
7 Static threshold value
7.1 General considerations
Harmonic distortion meter
Attenuator
DC block
Weighting network
(or level meter)
Video characteristic measurement equipment configuration
Flat field signal K
RMS value
Voltmeter
When the signal-to-noise ratio S/N of the receiver output is not in a linear relationship with the decrease of the carrier-to-noise ratio C/N, and the S/N drops significantly by 1dB, the corresponding carrier-to-noise ratio C/N value is the static threshold value. 7.2 Measurement method
According to the method in 6.2, the only difference is to change the carrier-to-noise ratio C/N value to measure the corresponding signal-to-noise ratio S/N value, then draw the relationship curve between the carrier-to-noise ratio C/N and the signal-to-noise ratio S/N, find the carrier-to-noise ratio C/N corresponding to the point 1dB lower than the straight line, this carrier-to-noise ratio C/N value is the threshold value, and record the corresponding signal-to-noise ratio S/N value.
7.3 Result expression
Use text description or curve expression.
8 Luminance/chrominance delay inequality
8.1 General considerations
GB/T 11298. 11997
When the specified composite measurement signal is added to the input of the system under test, the relative change in the time relationship between the corresponding parts of the luminance and chrominance components at the output is called luminance/chrominance delay inequality. The composite measurement signal includes a component with a fixed amplitude and a component of a chrominance subcarrier modulated by a luminance signal. 8.2 Measurement method
Connect the measurement equipment according to Figure 3 and set switches S1, S2, and S: to the positions of \1", "1", "2", respectively. The test signal generator outputs a sine square wave filled with a chrominance subcarrier as shown in Figure 5 (a). After being modulated by the transmitting device, it is sent to the receiving device under test. At the video output end, the compensation method is used to measure the values of parameters V. and V. shown in Figures 6 (a) and (b) on a waveform monitor (or oscilloscope). Finally, substitute the measured value into formula (4) to calculate:
Where: △t
luminance/chrominance delay is not equal, ns;
4(10T)vV
half amplitude point width of sine square pulse, ns; T=
2×6×106
V,—10T positive amplitude of sine square pulse bottom line deviating from baseline (as shown in Figure 6), mVV——10T negative amplitude of sine square pulse bottom line deviating from baseline (as shown in Figure 6), mV. When the chrominance signal lags behind the luminance signal, At(ns) is positive, otherwise it is negative. It can also be directly measured using an interpolation signal analyzer. 700mV
4.7μs12.3μ8 15μs
(a) 10T signal filled with subcarrier
(b) F, G signal filled with subcarrier
Figure 5 10T and bar pulse signals F, G filled with subcarrier8
GB/T 11298. 1—1997
Chrominance component
(a) The chrominance component delay is greater than the luminance component delay △t, which is positive8.3 Result representation
(b) The chrominance component delay is less than the luminance component delay △, which is negativeFigure 6 The luminance/chrominance delay △t measured at the output end is not equal. Please explain it in words or express it in a graph.
9 Luminance/chrominance gain inequality
General considerations
Add a test signal with specified luminance and chrominance components to the input of the system under test. The change in the amplitude ratio of the chrominance component to the luminance component between the input and the output is called luminance/chrominance gain inequality. 9.2 Measurement method
a) As shown in Figure 3, set switches St, Sz, and S to the \1"\1""2\ positions respectively; b) The subcarrier-filled sine square wave (Figure 5a, Figure 5b) output by the test signal source is modulated by the transmitting device and sent to the receiving device under test. At the video output end, the compensation method is used to measure V., VV shown in Figure 7 on the waveform monitor (or oscilloscope). Substitute it into formula (5) to calculate AK, expressed as a percentage.
Where: V.
2(V,- V)
-10T The positive amplitude of the bottom line of the sine square pulse deviating from the baseline, mV; -10T The negative amplitude of the bottom line of the sine square pulse deviating from the baseline, mV; -10T The total amplitude of the sine square pulse, mV. When the chroma component gain is greater than the luminance component gain, as shown in Figure 7(a), △K is positive; otherwise it is negative, as shown in Figure 7(b). (a) The chroma component gain is greater than the luminance component gain △K is positive (5)
(b) The chroma component gain is less than the luminance component gain △K is negative Figure 7 Luminance/chroma gain inequality diagram
△K can also be directly measured using an inset analyzer. 9.
9.3 Result representation
Represented in text or chart.
10 Differential gain distortion
General consideration
GB/T 11298.1—1997
A color subcarrier with a constant amplitude is superimposed on the luminance signal of different levels and added to the input of the system under test. When the luminance signal changes from the blanking level to the white level, and the average picture level (APL) is maintained at a certain specified value. The change in the output color subcarrier amplitude is called differential gain distortion.
10.2 Measurement method
Connect the measuring equipment according to Figure 3, set switches S1, S2, and S: to "1", "1", and "2" respectively, and add the test signal to the input of the system under test after being modulated by the transmitting equipment, and measure A, Amax, and Amin at the visual output end using an oscilloscope as shown in Figure 8 (b). Substitute the values into formulas (6), (7), and (8) for calculation: X=
The peak-to-peak value of the differential gain distortion is:
Where: X-
11 ×100
— 11 × 100
Am_ Amim - 11 × 100
Positive peak value of differential gain distortion, %;
Negative peak value of differential gain distortion, %,
Peak-to-peak value of differential gain distortion, %:
A. 一一一Subcarrier amplitude or detection level at blanking level at output end: Amax——the maximum value of subcarrier amplitude or detection level at each step of the step wave (including blanking level);: Amin——the minimum value of subcarrier amplitude or detection level at each step of the step wave (including blanking level). (6)
It is required to measure the differential gain distortion values under the three conditions of average picture level (APL) of 12.5%, 50% and 87.5% respectively, and take the maximum value.
Differential gain distortion can also be directly measured by line analyzer. 700mV-
-300mV
(a) Staircase wave D2 filled with color subcarrier (b) Envelope waveform after detection
Figure 8 Staircase wave filled with color subcarrier signal D, and the detected waveform after demodulation 10.3. Result presentation
Explain in words or in diagrams.
11 Differential phase distortion
11.1 General considerations
GB/T 11298.1--1997
When a chrominance subcarrier with constant amplitude that is not phase modulated is superimposed on luminance signals of different levels and added to the input of the system under test, and the luminance signal changes from blanking level to white level while the average picture level remains constant, the phase change of the subcarrier at the output end is called differential phase distortion.
11.2 Measurement method
Set switches S1, S2, S3 to positions 1, 1, and 2, respectively, as shown in Figure 3. The test signal source outputs a signal Dz [Figure 8a)]. After being modulated by the transmitting device, it is sent to the receiving device under test. The subcarrier phase on each step is measured with an oscilloscope at the video output end. Taking the subcarrier phase d at the blanking level as the reference as shown in Figure 9, substitute the measured values of max, pmin, and p into formula (9), formula (10), and formula (11) to calculate: X = Ipmar - Y = lomin - l
The peak-to-peak value of the differential phase distortion is:
X+ Y = [max - min !
Where: X—positive peak value of differential phase distortion, (°); Y
negative peak value of differential phase distortion, (°); X+Y—peak-to-peak value of differential phase distortion, (°); dmax——maximum value of subcarrier phase on each step of the step wave at the output end of the device under test (°); minimum value of subcarrier phase on each step of the step wave at the output end of the device under test (°). Smin
·（9)
10)
It is required to measure the differential phase distortion values under the three conditions of average image level of 12.5%, 50% and 87.5%, and take the maximum value as the test result.
Differential phase distortion can also be directly measured by line analyzer. 5
Figure 9 Subcarrier phase on each step wave output
11.3 Result representation
Use text description or diagram to represent.
12 Audio signal-to-noise ratiowwW.bzxz.Net
12.1 General considerations
The audio signal-to-noise ratio refers to the ratio of the signal power to the noise power at the output end of the audio channel of the receiving system under test. 12.2 Measurement method
Connect the measuring equipment according to Figure 3, and turn on switches S,, S, S: Connect to the positions of \1", "1", and "3" respectively; input a test tone signal with a constant amplitude and a frequency of 1.42kHz at the input end of the audio modulator at the transmitting end, so that the frequency deviation of the audio subcarrier (such as a frequency of 6.6MHz) is a FM signal of a specified value (such as ±100kHz), and send this signal to the receiving device under test after being modulated by the transmitting device; use an effective value voltmeter or a quasi-peak voltmeter to measure the signal level V at the audio output end, and at the same time keep the carrier-to-noise ratio C/N (dB) value of the indoor unit at the rated value. Then, connect the audio input port of the transmitting end to a 600α impedance, and measure the noise level V at the audio output end of the device under test. Substitute the values of V and V into formula (12) to calculate the audio signal-to-noise ratio.
S/N = 20 lg
Where: S/N-
Signal-to-noise ratio of audio, dB;
(12)
V.—Signal level, mV;
V.—Noise level, mV.
12.3 Result expression
Describe in words.
3 Total harmonic distortion of audio
General consideration
GB/T11298.1—1997
The total harmonic distortion of audio is the ratio of the root mean square value of each single-tone harmonic voltage to the single-tone voltage. 13.2 Measurement method
The measurement configuration is shown in Figure 3. Set switches S1, S2, and S3 to "1\"1" and "4" respectively. Send constant-amplitude audio signals (such as frequencies of 100Hz, 1kHz, 7.5kHz, etc.) to the receiving device under test after modulation by the transmitting device. Use a distortion meter to measure at the audio output end. When measuring, the accompanying sound output should be kept at the specified level (such as +6dBm, impedance 600α) under the specified carrier-to-noise ratio C/N. 13.3 Result representation
Textual description is available.
Definition of unified weighted network
GB/T 11298.1—1997
(Appendix to the standard)
Video unified weighted network
The unified weighted network is designed to simulate the characteristic that the subjective feeling of the human eye to random noise varies with frequency, which can make the measurement result close to the actual average visual effect.
A2 Structure of unified weighted network
The structure of unified weighted network is shown in Figure A1. Ri
Z. =750
2. -750-
Figure A1 Unified weighted network
A3 Unified weighted network parameters
Inductance: L=Zo
Capacitance: C=
Resistance: R=αZ,
Regulations: Z. =750
t=245 ns
Specific component values are shown in Table A1.
Component symbol
Component value
3266pF
A4 Insertion loss of uniform weighted network A
Where: -—angular frequency, rad/s
t-—delay, ns.
GB/T 11298.1—1997
A=10lg
At high frequency A20lg(1+a)=14.8dB
A5 The characteristics of the uniform weighted network
are shown in Figure A2.
1+(lwt)2
Characteristic curve of uniform weighted network
e0eo2o(Al)
Frequency, MHzS/N-
Signal-to-noise ratio of audio, dB;
(12)
V.—Signal level, mV;
V.—Noise level, mV.
12.3 Result expression
Describe in words.
3 Total harmonic distortion of audio
General consideration
GB/T11298.1—1997
The total harmonic distortion of audio is the ratio of the root mean square value of each single tone harmonic voltage to the single tone voltage. 13.2 Measurement method
The measurement configuration is shown in Figure 3. Set switches S1, S2, and S3 to "1\"1" and "4" respectively. Send constant-amplitude audio signals (such as frequencies of 100Hz, 1kHz, 7.5kHz, etc.) to the receiving device under test after modulation by the transmitting device. Use a distortion meter to measure at the audio output end. When measuring, the accompanying sound output should be kept at the specified level (such as +6dBm, impedance 600α) under the specified carrier-to-noise ratio C/N. 13.3 Result representation
Textual description is available.
Definition of unified weighted network
GB/T 11298.1—1997
(Appendix to the standard)
Video unified weighted network
The unified weighted network is designed to simulate the characteristic that the subjective feeling of the human eye to random noise varies with frequency, which can make the measurement result close to the actual average visual effect.
A2 Structure of unified weighted network
The structure of unified weighted network is shown in Figure A1. Ri
Z. =750
2. -750-
Figure A1 Unified weighted network
A3 Unified weighted network parameters
Inductance: L=Zo
Capacitance: C=
Resistance: R=αZ,
Regulations: Z. =750
t=245 ns
Specific component values are shown in Table A1.
Component symbol
Component value
3266pF
A4 Insertion loss of uniform weighted network A
Where: -—angular frequency, rad/s
t-—delay, ns.
GB/T 11298.1—1997
A=10lg
At high frequency A20lg(1+a)=14.8dB
A5 The characteristics of the uniform weighted network
are shown in Figure A2.
1+(lwt)2
Characteristic curve of uniform weighted network
e0eo2o(Al)
Frequency, MHzS/N-
Signal-to-noise ratio of audio, dB;
(12)
V.—Signal level, mV;
V.—Noise level, mV.
12.3 Result expression
Describe in words.
3 Total harmonic distortion of audio
General consideration
GB/T11298.1—1997
The total harmonic distortion of audio is the ratio of the root mean square value of each single tone harmonic voltage to the single tone voltage. 13.2 Measurement method
The measurement configuration is shown in Figure 3. Set switches S1, S2, and S3 to "1\"1" and "4" respectively. Send constant-amplitude audio signals (such as frequencies of 100Hz, 1kHz, 7.5kHz, etc.) to the receiving device under test after modulation by the transmitting device. Use a distortion meter to measure at the audio output end. When measuring, the accompanying sound output should be kept at the specified level (such as +6dBm, impedance 600α) under the specified carrier-to-noise ratio C/N. 13.3 Result representation
Textual description is available.
Definition of unified weighted network
GB/T 11298.1—1997
(Appendix to the standard)
Video unified weighted network
The unified weighted network is designed to simulate the characteristic that the subjective feeling of the human eye to random noise varies with frequency, which can make the measurement result close to the actual average visual effect.
A2 Structure of unified weighted network
The structure of unified weighted network is shown in Figure A1. Ri
Z. =750
2. -750-
Figure A1 Unified weighted network
A3 Unified weighted network parameters
Inductance: L=Zo
Capacitance: C=
Resistance: R=αZ,
Regulations: Z. =750
t=245 ns
Specific component values are shown in Table A1.
Component symbol
Component value
3266pF
A4 Insertion loss of uniform weighted network A
Where: -—angular frequency, rad/s
t-—delay, ns.
GB/T 11298.1—1997
A=10lg
At high frequency A20lg(1+a)=14.8dB
A5 The characteristics of the uniform weighted network
are shown in Figure A2.
1+(lwt)2
Characteristic curve of uniform weighted network
e0eo2o(Al)
Frequency, MHz
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