SJ 20580-1996 Communication system electrical performance measurement method
Some standard content:
Military Standard of the Electronic Industry of the People's Republic of China FL0130
SJ20580-96
Methods for communication system electrical performance measurement1996-08-30 Issued
1997-01-01 Implementation
Ministry of Electronics Industry of the People's Republic of China
1 Scope
1.1 Subject matter
1.2 Applicable scope
2 Referenced documents
3 Definitions
3.1 Terminology
4 General requirements
4.1 Environmental conditions for measurement
4.2 Preparation requirements
5 Detailed requirements
5.1 Measurement of bonding resistance
5.2 Crosstalk (intelligible) measurement
5.3 Digital bit error measurement
5.4 Digital jitter measurement
5.5 Signal dropout (drpout) measurement
5.6 Envelope delay distortion (EDD) measurement
Frequency measurement
5.8 Frequency measurement Measurement of rate conversion error
5.9 Measurement of harmonic distortion..
Impulse noise measurement
Transmission loss-rate characteristic measurement
Intermodulation distortion (TMD) measurement
Longitudinal balance measurement
Net attenuation/gain change measurement?
Noise figure measurement
Noise/Signal-to-noise ratio measurement
Phase impact measurement
Phase jitter measurement
Ground resistance measurement
Return loss measurement
Sidetone measurement
Speech volume measurement
Telephone equipment transmission noise measurement
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People's Republic of China Electronic Industry Military Standard Communication System Electrical Performance Measurement Method
Methods for communication system electrical performance measurement1 Scope
1.1 Subject content
This standard specifies the measurement method of communication system electrical performance. 1.2 Scope of application
SJ 20580-96
This standard is applicable to the measurement of strategic and tactical communication system performance, and can also be used for the measurement of related subsystem performance. 2 Referenced Documents
GB/T 13428—92
GJB/Z 25—91
Methods of measurement of delta modulation terminal equipment
Guide to the design of grounding, bonding and shielding of electronic equipment and facilitiesCCITT Recommendation G.821 Error performance of international digital connections forming part of the Integrated Services Digital Network (ISDN)3 Definitions
3.1 Terms
3.1.1 Impairment
Any transmission channel characteristic or degradation that may reduce the performance or quality of a communication system or subsystem (of which the channel is a part).
3.1.2 Intrinsic jitterIntrinsic jitter refers to the digital or time jitter that appears at the output when there is no jitter at the input. 3.1.3 Jitter transfer characteristic The ratio of the output jitter value (time, amplitude, frequency or phase) to the input jitter value at a given jitter frequency and a given bit rate.
Transmission impaximent measuring set (TIMS) 3.1.4 Transmission impairment measuring set Www.bzxZ.net
For the purposes of this standard, a transmission impairment measuring set is a broad term used to denote the measuring equipment associated with any given measurement method, rather than a specific automatic test equipment with all measurement capabilities. It may be portable or fixed and it denotes only the minimum test unit or series of units required for any given measurement method. 3.1.5 Unit under test (UUT) Depending on the measurement task, the sample that is subjected to performance analysis may be a system, a subsystem, or a device. The unit under test sample may be a link, channel, circuit, transmitter, receiver, modem, and multiplexer. Issued by the Ministry of Electronics Industry of the People's Republic of China on August 30, 1996 and implemented on January 1, 1997
4 General requirements
4.1 Environmental conditions for measurement
SJ20580-96
All parts that may cause damage to the equipment should be excluded during measurement. Unless otherwise specified, the measurement should be carried out under the following standard atmospheric conditions for the test:
Temperature: 15-35℃;
Relative humidity: 20%～80%;
Air pressure: test site air pressure.
4.2 Equipment requirements
When using the measurement methods described in this standard, the requirements described in this clause should be noted: a. To prevent the formation of ground loops, the device under test (UUT) should be connected to a separate ground point. Before connecting the device under test to the measuring equipment, check whether the connections and switch positions are correct. Where possible, the measuring equipment should use a filtered AC power supply;
b. The calibration time of the measuring instrument should comply with the time limit required by the manufacturer's product specifications or other applicable documents to ensure the required tolerance and make the measurement correct:
c. The connection with the UUT, related circuits and measuring equipment (including test cables) should be considered as a balanced or unbalanced interface; when making test connections, the impedance matching and the inherent cable loss should also be checked. d. The device under test (UUT) configuration should be compatible with the measurement method. 5 Detailed requirements
The measurement methods given in each section of this chapter are mainly used to measure the electrical performance of the system shown in Figure 1. 2
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Audio product
Effective digital user
Damage analysis
Analog interface
Distribution equipment
Digital interface
Clearing equipment
Shangying mathematics user
SJ2058096
Transmission media
(cable light wave, radio, etc.)
"Damage analysis
Analog interface
Adapter equipment
Digital interface
Adapter equipment
High-speed digital user!
Figure 1 Schematic diagram of the communication system in the end-to-end measurement environment Figure 5.1 Measurement of bonding resistance
Audio user
Digital product
This method is applicable to determining the adequacy of electrical connection between metal bonding based on DC (ID, C.) bonding resistance. 5.1.1 Measuring equipment
Low resistance ohmmeter with 4 terminals: or
DC resistance bridge; or
Low-resistance wire with power spring clamps.
5.1.2 Measurement principle
The DC resistance of a typical point-to-point electrical bonding should be less than 1 mg, and a 4-terminal measuring device with a maximum range of 1/10mQ to a sufficient upper limit should be used. The voltage drop across the bonding is detected by the measuring equipment and compared with the internal standard Compare, then convert it into a reading in ohms and read it directly.
5.1.3 Measurement method
The measurement principle is shown in Figure 2. After ensuring that the ohmmeter has been correctly calibrated, clamp the wires to both ends of the overlapping connection point as shown in Figure 1. If a bridge is used, the bridge should be adjusted to zero (including the wires), and then the wires are clamped to both ends of the overlapping connection as shown in Figure 2, and the bridge is balanced until it is balanced. Read the resistance value and compare it with the specified resistance limit value. 3
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Note: The current wire size must be adjusted appropriately to be able to transmit the maximum test current. ② The method of connecting the current line away from the connection point and the potential line close to the connection point can make The influence of the probe contact resistance is minimal. However, if the measured connection is an internal connection to the metal grid, there will be other current paths parallel to the measured connection path. In this case, the voltage probe and the current probe should be close to the same point of the connection to minimize the error. 4-terminal low-limit ohmmeter
or bridge
current conductor
5.2 Crosstalk (interpretable) measurement
potential bus
measured connection
Figure 2 Schematic diagram of connection resistance measurement
This method is suitable for measuring near-end and far-end interpretable crosstalk. It can be used to measure the crosstalk of two or more parallel analog or quasi-analog signal channels or circuit equipment. 5.2.1 Measurement equipment
Transmission impairment measurement equipment (TIMS);
Frequency-selective level measurement equipment, or voice channel characteristic comprehensive tester. 5.2.2 Measurement principle
When two adjacent transmission channels have noise, the interference signal from the other channel can be detected in one channel. Near-end crosstalk is measured at the end closest to the source of the interference signal. Far-end crosstalk is measured at the end farthest from the source of the interference signal. If the two channels transmit in opposite directions, the near-end crosstalk is important. On the contrary, the far-end crosstalk must be considered. The crosstalk measurement result is generally expressed as the ratio of the power transmitted by the interference channel source to the power received at the measurement point of the interfered channel. For the entire transmission system, it is meaningful to consider any difference in the nominal relative voltage at each measurement point. This measurement result can be expressed in two ways, namely, as the measured noise power level relative to 1mW (in dB) and as the noise power level measured relative to the zero transmission level point or at the zero transmission level point (OTLP) (i.e. dBmO). 5.2.3 Measurement method
The measurement block diagram is shown in Figure 3.
TIMS (generator) or
Channel characteristic comprehensive tester
(generator)
Select level measurement equipment or
Channel A
Device under test
Channel B
Channel characteristic comprehensive tester (receiver)
Near-end crosstalk
Channel terminal
Channel terminal
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TIMS (generator) or
Channel characteristic comprehensive tester
(generator)
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Channel A
Device under test
Channel B
Channel terminal
b. Far-end crosstalk
Channel terminal
Frequency-selective level measurement equipment or
Channel characteristic comprehensive tester
(receiver]
Figure 3 Crosstalk (intelligible) measurement diagram
Adjust the TIMS to the specified frequency and level, then switch the frequency-selective level measurement equipment to its narrowband bit quantity, record the difference between this level and the reading on the meter of the interfered channel in dB (should be expressed in dBm or dBm according to the standard requirements), and then compare it with the value required in the specification of the device under test. Remove the TIMS from the interfering channel and replace it with a terminated nominal load to verify that the power level measured on the interfered channel is mainly crosstalk and the residual noise has little effect. The following formula can be used to compensate for the effect of residual noise on the crosstalk reading: dB2 = dB1-10log10(1-10u-1)
Where: cB1 is the uncorrected decibel number, dB; dB2 is the corrected decibel number, dB;
is the decibel difference between the uncorrected decibel number and the residual noise reading. Repeat this measurement method at other frequencies required by the applicable specifications of the UUT. 5.3 Digital Error Measurement
This method is applicable to checking digital data streams to determine whether the transmitted logical state detected by the receiving end is the opposite state (i.e., bit error). This method provides information on error analysis such as error calculation, bit error rate (BFR), block error rate (BI,ER), error seconds, error-free seconds (EFS), percentage of availability and unavailability, severely errored seconds (SES) and percentage degradation.
5.3.1 Test equipment
Error measurement equipment (with pattern generator and error detector, if these two parts are assembled in one, two units are required for end-to-end configuration);
Recording device,
5.3.2 Measurement principle
Digital errors are detected by error count or error time interval. BER is obtained by the ratio of the number of error bits received in the case of errors to the total number of transmitted bits; BLER is also obtained by the ratio of the number of error blocks received in the case of errors to the total number of transmitted blocks. The meaningful measurement is the BER and BLER measurement within the specified averaging time. Note: The measurement time generally required is inversely proportional to the data rate. The average measurement time recommended by CCI-G.821 is: when the BER threshold value is 0 to 10-\, the average measurement time is 1s to 10min; the total measurement time can be as long as one month, depending on the type of digital service being evaluated. In the calculation results of the BER analyzer or measuring instrument, for high confidence, the error rate measurement usually requires the collection of at least 100 errors.
Error zone appears in the beginning and is independent of the sampling period. The error interval is often expressed in error seconds. When the measurement is performed within the specified measurement time range, the error seconds can be used to derive the percentage error seconds, percentage SES, and percentage degradation points. FFS measurements should be performed within the specified sampling period. u BI.ER can be expressed as EFS at is block length. 5
SJ 20580—96
Percentage availability is another way to characterize digital error performance. For BER exceeding the threshold value, it can be derived from the value of the 1s interval within the measurement period. Note: Percentage availability, percentage unavailability (the opposite of percentage availability), percentage error seconds, percentage severely errored seconds (SES), and percentage degradation points are all derived from the available time in CCITTG.821. In BER measurement, the limits of the random distribution of bit errors shall be specified, while BLER and EFS are the error rules used to characterize the distribution of bit error bursts.
The measurement shall be performed using error measurement equipment suitable for characterizing the results of the measurement items specified in the UUT specification. 5.3.3 Measurement method
The measurement block diagram is shown in Figure 4.
Digital stream
Error measurement equipment
(Pattern generator)
Timing 1)
Timing 1)
Equipment under test
Digital stream
Timing 1)
Figure 4 Block diagram of digital error measurement
Error measurement equipment
Error detector)
Recording device
Note: I) If the equipment under test (UT) cannot provide a clock signal that works in step mode, synchronization is achieved using the clock signal of the pattern generator or an external clock provided by the transmitting end of the error measurement equipment. 2) The device under test can be either an analog device (terminated with a data modem) or a digital device. This method measures the distribution of bit errors when a test signal (a known data sequence) is applied. When using the dashed line portion of the figure, if appropriate timing cannot be obtained from outside the UUT, the timing can be provided internally by the bit error measurement device.
Note: Sometimes, it is best to use an external timing source because it is difficult to synchronize with the receiver of the measurement device with internal timing. After selecting the interface and format of the modem or other terminating device suitable for the UUT, a known code pattern (generally a random code pattern) is sent through the UUT. At the receiving end, an identical error-free code pattern is generated internally by the bit error measurement device, synchronized, and then compared with the received signal. Observe directly on the test display, or monitor the error count or error interval directly on the recording device. At the end of the test required time, record the measurement results and compare them with the required values in the UUT specification. 5.4 Digital jitter measurement
This method is suitable for measuring the inherent jitter and jitter transfer characteristics of digital transmission systems. 5.4.1 Measurement equipment
Jitter generator/receiver (jitter measurement equipment): spectrum analyzer (optional);
voltmeter (optional);
recording device.
5.4.2 Measurement source
Digital jitter is a key impairment parameter of digital transmission systems. At higher bit rates, the interval between pulses shortens and the data pulse becomes narrower. Since the jitter of the digital path is cumulative, the pulse transition position may occur before or after the expected position, thereby causing errors in the pulse transition at the receiving end. Time jitter measurement can be completed using a jitter measurement device 6
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that can detect and calculate the reference time base 0 crossing point, and can be controlled by gate control or by external start and stop actions to control the time interval counter.
5.4.3 Measurement method
The measurement block diagram is shown in Figure 5.
Jitter measurement equipment
(Generator)
Voltmeter
SJ 20580-96
Device under test
Recording device
Jitter measurement equipment
(Receiver)
Demodulator output
Spectrum analyzer
Figure 5 Block diagram of digital jitter measurement
Note: Voltmeter and spectrum analyzer can be used to measure RMS amplitude or spectral content, respectively. A better way to measure digital jitter is to use a jitter generator/receiver (jitter measurement equipment) that can generate the required input jitter amplitude and frequency and provide direct readout of the jitter measurement parameters. Generally, the receiving part of the measuring equipment should have an output port to receive the demodulated jitter. The root mean square (RMS) amplitude of the demodulated jitter can be measured by a voltmeter, or the spectrum content can be measured by a spectrum analyzer.
a. Intrinsic jitter is the output jitter measured in the absence of input jitter. In the absence of input jitter, the intrinsic jitter output of the UUT will appear in the peak-to-peak symbol interval. The jitter amplitude is recorded and then compared with the limit specified in the UUT specification;
Note: In the absence of jitter measurement equipment, the alternative method of the indicator can be used. However, for ease of use and accuracy, it is best to use a dynamic measurement equipment with a generator and a receiver.
b. The jitter transfer characteristic is the relationship between the ratio of the output jitter to the input jitter and the jitter frequency at a given bit rate. The input jitter is the jitter specified in the applicable standard with amplitude and frequency parameters. The jitter transfer characteristic is evaluated by applying a jittered data stream to the UUT input through a generator, and then observing the output jitter frequency and gain on the jitter spectrum of interest at the receiver. The jitter value obtained is recorded and compared with the requirements in the UUT specification: c. The jitter gain-jitter frequency characteristic curve is generally drawn using a recording device that can compare the test results with the values specified in the UUT specification.
5.5 Signal Dropout (drpout) Measurement
This method is suitable for measuring large channel drops caused by deep radio fades, or communication continuity interruptions in communication systems.
5.5.1 Measurement Equipment
Transmission Impairment Measurement Equipment (TIMS), 2 units; Recording Device (Optional).
5.5.2 Measurement principle
If the hold tone drops by more than 12dB within a specified time interval, it is considered as "signal loss". Use the signal loss measurement equipment or the transmission impairment measurement equipment (TIMS) to measure the hold tone receiving signal level at the beginning of the measurement time interval, and specify 7
SI 20580-96
12dB below this level is the signal dropout threshold. During the measurement, this threshold should be kept constant. The parameters for the signal dropout measurement include: the time the gain remains below the threshold, the number of signal dropouts in a given time interval, and the signal dropout time distribution.
5.5.3 Measurement method
The measurement block diagram is shown in Figure 6.
(Generator)
Irrigated equipment
(Receiver)
Recording device
Figure 6 Signal dropout measurement block diagram
Note: The recording device can be used to characterize the performance results. TIMS (generator) sends a holding tone to accumulate Signal dropout is controlled and adjusted to the threshold and required time interval required for the device under test, and the received TIMS counts the signal dropout. The number of signal dropouts within the required time is recorded, and then compared with the requirements in the specifications of the device under test. 5.6 Envelope Delay Distortion (ED) Measurement
This method is applicable to envelope delay distortion measurements performed to evaluate the linearity of the phase-frequency response characteristics of a voice channel in a communication system.
5.6.1 Measurement Equipment
2 Transmission Impairment Measurement Equipment (TIMS): Recording device.
5.6.2 Measurement Principle
The absolute delay of the signal transmitted through the channel (i.e., the transmission time) The phase shift of each frequency (time) can change with frequency. This change is defined as phase or delay distortion, which is equivalent to nonlinear phase shift. Since it is impractical to measure the absolute phase shift of each frequency passing through the channel, this method uses a scanning carrier frequency modulated with a low-frequency signal to perform relative measurements. Delaying the carrier frequency and its modulation sidebands also delays the modulation envelope. Therefore, envelope delay distortion is the maximum envelope delay deviation that exceeds the specified frequency band. In data transmission, envelope delay distortion (EDD) will enhance the inter-symbol interference surface and cause additional bit errors, while increasing sensitivity to system noise and bandwidth limitations.
5.6.3 Measurement method
There are two basic methods to measure envelope delay distortion. ：The method specified in Article 7.12.2 of GB/T3428; a.
b. A reference method that requires an additional circuit (forward or reverse reference line). The two methods use different measuring equipment and are not compatible. The standard recommends method &. Record the measured values under the specified frequency and envelope delay limits. And compare with the requirements in the specification. 5.7 Frequency measurement
This method is applicable to measuring the ability of an independent frequency source to maintain a fixed and specified frequency. 5.7.1 Measuring equipment
Frequency meter;
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Relying on frequency and time standards (if necessary):
Recording device.
5.7.2 Measurement principle
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The basic tool for frequency measurement is a frequency meter that can calculate the number of cycles of the measured signal within a known exact time interval. In general, the accuracy of the frequency meter must be at least one order of magnitude higher than that of the device under test. For this reason, it is sometimes necessary to use a primary or secondary standard as the time reference for the frequency meter.
5.7.3 Measurement method
The measurement block diagram is shown in Figure 7.
Recording device
Frequency counter
Prediction and time standard
Figure 7 Frequency measurement block diagram
Equipment under test
Note: ① The frequency meter is generally unbalanced to ground, and the frequency meter used may be sensitive to external noise induced on the test signal line or to longitudinal current caused by the LUT.
) The dotted line is only required for those measurements where high accuracy cannot be obtained from the internal frequency oscillator. Monitor and record the frequency meter readings under the specified temperature rise and environmental conditions of the equipment under test and for the time required for the highest accuracy or for the time required for stability. The maximum deviation from the specified frequency of the device under test is recorded and compared with the specified tolerance of the device under test. If the measurement is not done automatically, the frequency stability can be calculated using the following formula: (FmmFam) 100
Where; S—stability,%;
-maximum deviation frequency of the carrier frequency measured, Hz;
Fin—minimum deviation frequency of the carrier frequency measured, Hz; F. specified carrier frequency, Hz.
5.8 Measurement of frequency conversion error
This method is suitable for detecting the frequency change that occurs when an audio signal is transmitted in one direction through an audio channel. This measurement is mainly used in systems that include frequency conversion technology such as frequency division multiplexing (FDM) equipment. 5.8.1 Test equipment
Signal generator:
Frequency meter, 2 units,
5.8.2 Measurement principle
When the transmitted carrier frequency and the received carrier frequency are different, the non-synchronized FIDM system will cause the frequency of the audio signal to deviate. These undesirable changes are sometimes called frequency displacement or frequency drift errors. 5.8.3 Measurement method
The measurement block diagram is shown in Figure 8.
Signal generator
Frequency meter
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Device under test
Figure 8 Frequency conversion error measurement block diagram
Frequency meter
The signal generator sends a test signal and then uses the readings on the two frequency meters to determine any changes in the frequency. The difference in readings is then compared with the requirements in the specification of the device under test to determine whether the requirements are met. 5.9 Harmonic distortion measurement
This method is applicable to single harmonic distortion measurements made in analog transmission systems. It can measure harmonic distortion within the transmission system, within the physical circuit, or within any independent part of the analog system (for example, an audio amplifier). Harmonic measurements made according to this method should be limited to those circuits and equipment that have harmonics within the passband of the device under test. 5.9.1 Measuring equipment
Signal generator;
Level measuring equipment:
Frequency-selective level meter measuring equipment or spectrum analyzer. 5.9.2 Measurement principle
Harmonic distortion is caused by the nonlinear transfer characteristics in the circuit or device. Therefore, it is a nonlinear distortion formed by the newly generated signal components that are not in the original transmitted signal. This distortion appears as the harmonics of the single frequency input signal, so it is called harmonic distortion. In audio circuits, harmonic distortion refers to the in-band second and third harmonics related to the original frequency.
5.9.3 Measurement method
The measurement block diagram is shown in Figure 9
Signal generator
There are two methods for measuring harmonic distortion:
Equipment under test
Level measurement equipment
Figure 9 Harmonic distortion measurement block diagram
Single harmonic distortion method using a frequency-selective level meter or spectrum analyzer: a.
b. Total harmonic distortion method using a zero-adjusted harmonic analyzer. The frequency-selective level meter or spectrum analyzer used in method 6 cannot distinguish between harmonics and noise and cannot provide the level of a single harmonic, so this standard recommends the use of method a. When measuring, add a test tone to the input of the device under test as shown in Figure 9, and then measure the harmonic component level at the output. Assuming that the frequency and level are properly adjusted, measure the in-band harmonic level relative to the fundamental wave, and record the level value as a percentage or decibel below the fundamental wave, and then compare these values with the values required by the UUr specification. Using the following formula, the harmonic distortion can be converted from the decibel number below the fundamental wave to the percentage distortion 100
log-1100.050
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