GB/T 11299.4-1989 Satellite communication earth station radio equipment measurement methods Part 1: Measurements common to subsystems and subsystem combinations Section 4: Baseband measurements
Some standard content:
National Standard of the People's Republic of China
Methods of measurement for radio equipment used in satellite earth stationsPart 1: Measurements common to sub-systemsand combinations of sub-systemsSection Four-Measurements in the basebandThis standard is GB11299.4-89 of the series of standards "Methods of measurement for radio equipment used in satellite earth stations"
IEC510-1-4(1986)
This standard is equivalent to the International Electrotechnical Commission standard IEC510-1-4 (1986) "Methods of measurement for radio equipment used in satellite earth stationsPart 1: Measurements common to sub-systemsand combinations of sub-systemsSection Four-Measurements in the baseband". 1 Subject content and scope of application
The basic measurements given in this standard are applicable to subsystems (such as amplifiers) and also to the subsystem combinations of simulated satellite earth stations.
This standard specifies methods of measurement of the following parameters: a.
Input and output impedance (return loss);
Input and output levels;
Baseband gain or loss;
Amplitude/frequency characteristics;
Group delay/frequency characteristics;
Non-linear amplitude distortion;
Differential gain and differential phase distortion.
Methods for measuring parameters related to specific baseband signaling, such as frequency-division multiplexed telephone or television transmissions, are given in the relevant clauses of Part 1 of this series of standards.
2 Linear Input and Output Characteristics
2.1 Return Loss
2.1.1 Definitions and General Considerations
In satellite communications earth stations, the measurement of return loss rather than the impedance reflection coefficient is of interest. The return loss (L) of the impedance (Z) relative to its nominal value (Z.) is given by the following equation: I. = 20 log1o|2
or by the following equation:
L20logt
Approved by the Ministry of Electronics Industry of the People's Republic of China on March 1, 1989 3.
Implemented on January 1, 1990
GB11299.4--89
Wu Zhong: -—The voltage reflection coefficient of impedance (7) relative to (2). That is: 2—2
0:=2+z
Note: (0) The nominal impedance (2) of the baseband port is usually 750 pure impedance (unbalanced), and 1500 pure impedance (balanced) for small capacity systems (free reference 1): ② The above equation is applicable to measurements using sinusoidal voltage and current. 2.1.2 Measurement Methods
Return loss can be measured directly as described below, or it can be calculated by measuring the complex impedance B or the value of the reflection coefficient ". When measuring return loss directly, the following method using a bridge is preferred, and any other measurement method that can achieve the required accuracy (approximately ±1d13) can also be used. The point-by-point measurement method can be used, as shown in Figure 1. Usually the device under test and the frequency-selective level meter are both grounded, so both ends of the test oscillator must be insulated from the ground. When the frequency is above 1kHz, the insulation can be achieved by transformer isolation. In many cases, the transformer is installed in the test base bridge or in the test oscillator. When the frequency is below 1kHz, it is usually measured by measuring the complex impedance 2, Then calculate the return loss.
The swept frequency method can also be used, as shown in Figure 2. Measurements at baseband frequencies usually use a complete measurement device consisting of a swept frequency signal generator, a sweep-controlled frequency-selective level meter, an oscilloscope, and a return loss bridge (the same bridge used in the point-by-point measurement method). The cables, attenuators, adapters used in the measurement process, and the return loss of the input and output connectors of the measuring equipment can all be measured as described below.
The measurement procedure consists of three steps: calibration, checking the balance of the measuring bridge, and measurement. 2.1.2.1 Calibration
See Figures 1 and 2. Connect a short-circuit device S. Replace the device under test and obtain a return loss of OdB. Write down the value selected at this time. Read the readings of the frequency-selective level meter and its input attenuator (Fig. 1), or mark the return loss curve that will be displayed on the scale screen of the oscilloscope as the calibration line (Fig. 2).
Note: For calibration purposes, a standard mismatched terminal Z. with a known return loss (e.g. 20 dB) can also be used instead of the short-circuit device S. 2.1.2.2 Check the balance of the bridge
Connect: - standard impedance Zs (Zs-Z.) to the measuring bridge to replace the device under test. Adjust the input attenuator of the frequency-selective level meter so that the frequency-selective level meter has the same reading as that obtained during calibration, or so that the point on the curve representing the minimum return loss within the scan bandwidth displayed on the oscilloscope coincides with the calibration line. The difference between the attenuator reading when the short-circuit device is connected and the attenuator reading when the standard impedance is connected is The difference is the return loss of the measurement system itself. If this return loss is XdB, the maximum value of the return loss that this measurement device is suitable for measuring is (X--20)dB, with an accuracy of ±1dB. This check takes into account any mismatch between the two standard impedances, as well as the effects of bridge balance, bridge leakage, etc. Note: When the errors of the two impedances are the same, this device is insensitive, because the measurement is to test whether their impedances are equal, not whether they are a specified impedance value, such as 75Ω impedance. 2.1.2.3 Measurement
The device under test is connected as shown in Figure 1 or Figure 2. In the point-by-point measurement method (Figure 1), adjust the input attenuator of the frequency-selective level meter so that the reading of the frequency-selective level meter is the same as the reading when the short circuit is connected. The difference between the attenuator reading when the short circuit is connected and the attenuator reading when the device under test is connected is the return loss of the device under test. When measuring the base using the swept frequency method (Figure 2), adjust the input attenuator of the sweep control frequency selection level meter so that the point on the line indicating the minimum return loss within the sweep bandwidth on the oscilloscope coincides with the calibration line. The difference between the attenuator reading when the short circuit is connected and the attenuator reading when the device under test is connected is the minimum return loss of the device under test. Note: If a standard mismatched terminal load with a known return loss is used for calibration, the return loss of the device under test is equal to the difference between the attenuator reading when the standard mismatched terminal load is connected and the attenuator reading when the device under test is connected, plus the return loss of the standard mismatched terminal load. 2.1.3 Result Representation The results of the frequency measurement method should be represented as much as possible by a photograph of the oil line displayed on an oscilloscope with a calibrated scale. It can also be represented by a curve recorded by a ×Y recorder or by a manually drawn curve, but in all cases, the bridge balance check oil line should be represented together with the measured curve of 36
GB 11299.4--89
. When the measurement results are not presented in a curve, they shall be presented as follows: \In the frequency range of 30kHz~~12MHz, the return loss is not less than 30dB and the bridge balance is not less than 45dB\For the point-by-point measurement method, the measurement results can also be given as in the above example. In addition, the measurement frequency interval should be given, for example, each decade of measurement. The measurement results can also be presented graphically, and the measured values are clearly marked on the figure F2.1.4 Details to be specified
When this measurement is required, the equipment specifications shall include the following: a. Nominal impedance Z.
b. Frequency range
℃
C. Wave loss tolerance
2.2 Input level
2.2.1 Definitions and general considerations
The input level must be defined to ensure that the signal generator is adjusted to the specified level when it is connected to the input of the device under test. For television systems, the input level is defined as: impedance equal to the nominal input impedance Z of the system under test. For frequency division multiplexing telephone systems, the input level is defined as the RMS voltage (or power) applied to a terminal load with an impedance equal to the nominal input impedance Z of the system under test. Note: If the input impedance of the device under test is different from Z, the voltage at its input port will be different from the input voltage defined above 2.2.2 Measurement method
The input test signal level is the level established by the signal generator at the terminal load with nominal impedance Z. Then, the output of the signal generator is connected to the input of the device under test without further level adjustment. The input level can be measured with a broadband level meter, a frequency-selective level meter, a power meter or a calibrated oscilloscope. The return loss relative to the terminal load with nominal impedance Z. should be greater than 30dB. Note: If a new instrument is used, the previous steps are not required, because such instruments are usually referenced to a specific value and scaled in decibels. 2.2.3 Result expression
Because the input level is generally specified as a component of some other measurement, it is usually not necessary to express it separately. 2.2.4 Details to be specified
When this measurement is required, the equipment specifications should include the following: a. Nominal input impedance Z,;
b. Nominal input level and tolerance;
The waveform used.
2.3 Output level
2.3.1 Definition
The output level of the equipment may be expressed as the peak-to-peak voltage, the RMS voltage across a standard terminal load with a nominal impedance Z, or as an appropriate quantity of the applied power. The peak-to-peak voltage is generally used for television measurements. 2.3.2 Measurement method
Connect the output of the equipment under test to a standard impedance terminal and measure the output level in accordance with 2.2.2. 2.3.3 Expression of results
For television systems, express in peak-to-peak voltage; for telephone systems, express in milliwatts or decibels relative to 1 mW. 2.3.4 Details to be specified
When this measurement is required, the equipment specifications shall include the following: a. Nominal output impedance Zo;
b. Nominal output level and tolerance.
3 Linear transfer characteristics
This clause only describes the measurement of baseband transfer characteristics that are independent of the baseband signal level within the normal operating range. The measurement of transfer characteristics that are related to the baseband signal level will be given in Clause 4. 3.1 Baseband gain or loss
3.1. 1 General definition
CB11299.4-89
Baseband gain is the ratio of output level to input level, expressed in decibels. If the baseband gain is a negative decibel number, its sign is usually changed and it is called loss.
3.1.2 Measurement method
The usual practice is to measure the input and output levels to calculate the baseband gain. For telephone systems, a test signal of a specified level is used for measurement. For television systems, a test signal of 1V peak-to-peak voltage is used for measurement. The baseband gain is measured at a specified test frequency, at which the frequency deviation measured with and without pre-emphasis is equal. In television systems, the gain may be measured using non-sinusoidal waves, such as the test signals shown in Section 3 of Part 3 of this series of standards, "Measurements on Television Transmissions".
3.1.3 Expression of results
The baseband gain is expressed in decibels at a specified frequency. 3.1.4 Details to be specified
When this measurement is required, the equipment specifications shall include the following: a. The frequency or waveform of the test signal;
b. The required baseband gain and tolerance.
3.2 Amplitude/frequency characteristic
The amplitude/frequency characteristic is the ratio of the baseband output level to the reference level (expressed in decibels) as a function of the baseband frequency. The measurement shall be made at a constant input level well below the saturation level. The reference level is usually the output level at a specified frequency. 3.2.2 Measurement method
The measurement may be made by point-by-point measurement or by frequency sweeping. For convenience, the point-by-point measurement method is usually used for frequencies below 20kHz, and the frequency sweep method is often used for higher frequencies.
If the point-by-point measurement method is used, a wideband level meter can be used, but it is best to use a frequency-selective level meter. When using a wideband level meter, it must be confirmed that the harmonic power at the output of the test signal generator is at least 40dB less than the fundamental power. The level meter should be equipped with a precision input attenuator. Figure 3 shows a typical equipment configuration for measuring baseband amplitude/frequency characteristics using the point-by-point measurement method. This set of equipment can also be used to measure gain or loss. Before measurement, set the value of attenuator 1 to a value slightly larger than the gain of the device under test, then alternately place switch S in the A and B positions, and adjust attenuator 2 so that the reading of the frequency-selective level meter in the A position is the same as the reading in the B position. In this way, the difference between the readings of attenuator 1 and attenuator 2 is the gain or loss of the device under test. The test equipment shown in Figure 3 is also suitable for the swept frequency method. It uses a baseband swept frequency signal generator and an oscilloscope connected to a sweep control (the sweep control signal is taken from the baseband signal generator) frequency selection level meter. Note: If there is a baseband level adjuster (baseband AGC amplifier) controlled by an in-band pilot signal in the system under test, the adjuster must be disconnected or bypassed.
3.2.3 Result Representation
When measuring with the swept frequency method, a photo of the curve displayed by the oscilloscope should be provided. When the measurement results are not presented graphically, they shall be presented as follows: \In the frequency range of 300Hz to 8MHz, the amplitude/frequency characteristic is within 0.2 to -0.1 ciB relative to the gain at 1MHz.
The point-by-point measurement method may present the measurement results in the form of a curve, table or the above text. 3.2.4 Details to be specified
When this measurement is required, the equipment specifications shall include the following: a. Reference frequency (e.g. 100kHz);
, frequency band range;
c. Tolerance for amplitude variation.
3.3 Group delay/frequency characteristic
3.3.1 Definitions and general considerations
For linear networks, the transfer function can be written as: GB11299.4---89
H(jw) = A(n) e
Where: A(w) - amplitude/frequency characteristic of a linear network; B(w) - phase/frequency characteristic of a linear network (a positive value is when the phase of the output signal lags behind the phase of the input signal). The group delay t() of the network is defined as the first-order derivative of B() with respect to α, that is: t(w)
The unit is expressed in seconds.
The group delay variation or group delay/frequency characteristic is defined as the difference between the above group delay and the group delay at the reference frequency. 3.3.2 Measurement method
The frequency sweep test signal is slowly The test signal is amplitude modulated or phase modulated by a signal with a suitable measurement frequency f (such as 20kHz), thereby obtaining a composite signal consisting of a carrier and two sidebands. This composite signal is applied to the test receiver through the device under test. In the test receiver, the frequency of the local oscillator is synchronously scanned with the swept frequency test signal to generate an intermediate frequency signal with a fixed frequency. After the intermediate frequency signal is amplitude demodulated or phase demodulated, The measured signal with a frequency of f is recovered and then subjected to phase detection to obtain a signal with a scanning rate. This signal is displayed on the oscilloscope as the group delay as a function of the baseband frequency.
This measurement is usually made using a commercially available set of dedicated test equipment. In the case of amplitude modulation, a baseband test receiver can be used to recover the measured signal with a frequency of f through an amplitude demodulator. 3.3.3 Result presentation
The measurement results can be presented using a photograph of the curve displayed by an oscilloscope with a calibrated scale or a curve recorded by an XY recorder. When the measurement results are not shown in a graphic format, the measurement results can be presented in a graphic format. When expressed, it should be expressed as follows: "Over the range of 200kHz to 8MHz, the total group delay variation is 87ns". 3.3.4 Details to be specified
When this measurement is required, the equipment specifications should include the following: a. Baseband frequency range;
b. Permissible group delay variation.
4 Non-linear transfer characteristics
Non-linear transfer characteristics are related to the level of the baseband signal. They are caused by the harmonics of the sinusoidal test signal and the intermodulation products of two or more such signals.
4.1 Differential gain/non-linearity
4.1.1 Definitions and general considerations
Differential gain/non-linearity refers to the gain variation for a small-amplitude high-frequency sinusoidal signal (test signal) as a function of the instantaneous value of a large-amplitude low-frequency signal (sweep signal) transmitted simultaneously on the same channel. For television systems, see Section 1 of Part 1 of this series of standards. The differential gain/nonlinearity is defined as a function of the instantaneous value above, given by the following formula: DG(X)
-differential gain;
where: DG(X)
instantaneous value of the input scanning signal;
GB11299.4-89
A(X)-amplitude of the output test signal, a function of A.= The amplitude of the output test signal when the sweep signal is at its peak. For a distortion-free, ideal DUT, the differential gain/nonlinearity is zero. However, for a practical device, the above function varies. A practical device is characterized by its differential gain/nonlinearity (DG), which is the difference between the two extreme values given by equation (7) below. It is usually expressed as a white fraction: DG Am(X) = Am(X) × 100%
The relationship between differential gain and nonlinearity and the choice of test signal frequency is given in the following clause. 4.1.2 Measurement method
Figure 4 shows a typical measurement equipment configuration, including the section for measuring differential phase/group delay. When measuring differential gain/nonlinearity, the switch should be in the position of the amplitude modulation detector. The baseband input signal applied to the DUT is a composite signal formed by superimposing the sinusoidal test signal on a sweep signal. At the baseband output of the DUT, the test signal component is separated and applied to an envelope detector. The output of the envelope detector is proportional to the amplitude of the test signal and is used as the vertical deflection voltage displayed by the oscilloscope; while the horizontal deflection voltage of the oscilloscope can be obtained directly from the sweep signal. If the device under test contains an IF/RF part, it can also be demodulated from the IF signal. The sweep signal is low-frequency and its amplitude is selected to cover the dynamic range of the device under test. The amplitude of the test signal should be much smaller than the amplitude of the sweep signal so that only a relatively small part of the measured characteristic curve is examined at any moment to obtain a smaller average error. The test signal frequency is generally always much higher than the sweep signal frequency, and its selection depends on the characteristics of the part of the device under test to be evaluated. If only the nonlinear effects of the baseband part of the modulator/demodulator are evaluated, a lower frequency (such as 50-500kHz) is selected, and the measured function is called nonlinearity. However, when the effects of nonlinearity of the carrier part and the baseband part are to be evaluated, a higher frequency (such as 112MHz) is used, and the measured function is called differential gain. 4.1.3 Presentation of Results
It is best to present the differential gain/nonlinear distortion as a photograph of an oscilloscope display or a curve recorded by an XY recorder. Scale the two axes appropriately, the horizontal axis in terms of swept voltage and, if the equipment under test includes a modulator and demodulator, in terms of frequency deviation. Alternatively, the distortion may be expressed as a percentage of the difference between the two extreme values of the function, with the sweep range (in megahertz) given. 4.1.4 Details to be Specified
When this measurement is required, the equipment specifications shall include the following: Frequency of the test signal:
b. Frequency of the sweep signal;
c. Sweep amplitude (volts, peak-to-peak), or sweep bandwidth (megahertz, peak-to-peak); d. Maximum permitted differential gain/nonlinear distortion in percentage. 4.2 Differential Phase/Group Delay
4.2.1 Definitions and General Considerations
Differential phase refers to the phase change of a small-amplitude high-frequency sinusoidal signal (test signal) as a function of the instantaneous value of a large-amplitude low-frequency signal (sweep signal) transmitted simultaneously on the same channel. The differential phase can be defined as a function of the instantaneous value given by the following equation: DP(X) (X) —
where: DPX is the differential phase;
X is the instantaneous value of the input sweep signal;
X) is the phase of the output test signal, which is a function of (8)
, - the phase of the output test signal when the sweep signal is zero. For a distortion-free, ideal device under test, the differential phase is zero. However, for a practical device, the above function varies. Practical equipment is characterized by its differential phase distortion (DP), which is the difference between the two extreme values of the above function, usually expressed in degrees, 39
GB 11299.4—89
= gmax - pmin
Note: When the differential phase is measured with a test signal of lower frequency (e.g., a few Hz), this measurement can also reflect the change in group delay. In practice, the group delay of the measuring equipment is usually scaled in nanoseconds
The group delay is proportional to the ratio of the differential phase to the test signal frequency. When using a test signal of higher frequency (e.g., a few MHz), the differential phase scale (degrees) is used.
4.2.2 Measurement method
Figure 1 shows a typical measurement equipment configuration, which also includes the measurement of differential gain/nonlinearity. The part of the linear distortion. When measuring the differential phase, the switch should be placed in the phase detector position. The baseband input signal added to the device under test is a composite signal, formed by superimposing a sinusoidal test signal on a slowly varying sweep signal. At the baseband output of the device under test, the test signal component is separated and added to a phase detector. The output of the phase detector is proportional to the phase change of the test signal and is used as the vertical deflection voltage displayed by the oscilloscope. The horizontal deflection voltage of the oscilloscope can be obtained directly from the sweep signal, or if the device under test contains an IF/RF section. The scan signal is low frequency and its amplitude is selected to cover the dynamic range of the device under test. The amplitude of the test signal should be much smaller than the amplitude of the scan signal so that only a relatively small part of the characteristic curve under test is examined at any moment to obtain a smaller average error. 4.2.3 Result Representation
It is best to use a photograph of the oscilloscope display or a curve recorded by an XY recorder to represent the differential phase distortion. Scale the two axes appropriately, the horizontal axis with the scan voltage scale, and if the device under test contains a modulator and demodulator, the horizontal axis with the scan voltage scale. Frequency deviation scale. Alternatively, this distortion may be expressed as the difference in degrees between the two extreme values of the function, together with the sweep range (V or MHz). 4.2.4 Details to be specified
When this measurement is required, the equipment specifications shall include the following: frequency of the test signal;
frequency of the sweep signal;
sweep amplitude (V, peak-to-peak), or sweep bandwidth (MHz, peak-to-peak); d.
maximum permissible differential phase distortion (degrees). 5 Reference material
5.1 CCIR Recommendation 380--3 (vol iX): Interconnection at baseband Irequencies lor radio-relay systems lor telephony using frcqjucency-division multiplex
5.2 CCIR Recommendation 567--1 (vol XIl) Transmission performance of television rircuits designctfor use in international connections.40
With signal generator
GB11299.4
Measuring bridge
Equipment under test
Selected level meter
Figure 1 Equipment configuration for measuring return loss using the point-by-point measurement method Equipment under test
With frequency-sweeping signal generator
Measuring bridge
Sweep control
Selected level meter
Current output
Sweep voltage
Fluctuator
Figure 2 Equipment configuration for measuring return loss using the swept frequency method Y
Test signal generator
Sweep conduction generator
Baseband signal generator
GB11299.4-89
Subtractor!
Attenuator 2
Equipment under test
Frequency-selective meter
Figure 3 Equipment configuration for measuring amplitude/frequency characteristics Light-modulated detector
Equipment under test
Band-pass filter
Phase-modulated detector
Oscilloscope display
Figure 4 Equipment configuration for measuring differential gain/nonlinear distortion and differential phase distortion Additional remarks
This standard was drafted by Nanjing Radio Factory. 422 Measurement Methods
Figure 4 shows a typical measurement equipment configuration, including the section for measuring differential phase/group delay. When measuring differential gain/nonlinear distortion, the switch should be placed in the position of the AM detector. The baseband input signal applied to the device under test is a composite signal, formed by superimposing a sinusoidal test signal on a sweep signal. At the baseband output of the device under test, the test signal component is separated and applied to an envelope detector. The output of the envelope detector is proportional to the amplitude of the test signal and is used as the vertical deflection voltage displayed by the oscilloscope; the horizontal deflection voltage of the oscilloscope can be obtained directly from the sweep signal. If the device under test contains an IF/RF section, it can also be obtained by demodulation from the IF signal. The sweep signal is low-frequency and its amplitude is selected to cover the dynamic range of the device under test. The amplitude of the test signal should be much smaller than that of the sweep signal so that only a relatively small part of the characteristic curve under test is investigated at any instant, so as to obtain a smaller average error. The test signal frequency is generally always much higher than the sweep signal frequency, and its selection depends on the characteristics of the part of the device under test to be evaluated. If only the nonlinear effects of the baseband portion of the modulator/demodulator are to be evaluated, a lower frequency (e.g. 50 to 500 kHz) is chosen and the function measured is called nonlinearity. However, if the effects of nonlinearity of the carrier and baseband portions are to be evaluated, a higher frequency (e.g. 112 MHz) is used and the function measured is called differential gain. 4.1.3 Presentation of results
Differential gain/nonlinearity distortion is best presented as a photograph of an oscilloscope display or a curve recorded by an XY recorder. Scale the two axes appropriately, the horizontal axis in terms of sweep voltage or, if the equipment under test includes a modulator and demodulator, in terms of frequency deviation. Alternatively, this distortion may be expressed as a percentage of the difference between the two extreme values of the function, with the sweep range (in megahertz) given. 4.1.4 Details to be specified
When this measurement is required, the equipment specifications shall include the following:
b. Frequency of the test signal;
c. Frequency of the sweep signal;
d. Sweep amplitude (volts, peak-to-peak), or sweep bandwidth (MHz, peak-to-peak); d. Maximum differential gain/percentage of nonlinear distortion allowed. 4.2 Differential Phase/Group Delay
4.2.1 Definitions and General Considerations
Differential phase refers to the phase change of a small-amplitude, high-frequency sinusoidal signal (test signal) as a function of the instantaneous value of a large-amplitude, low-frequency signal (sweep signal) transmitted simultaneously on the same channel. The differential phase can be defined as a function of the instantaneous values given by the following equation: DP(X) (X) —
Where: DPX differential phase;
X instantaneous value of the input sweep signal;
X) — phase of the output test signal, which is a function of; (8)
, — phase of the output test signal when the sweep signal is zero. For a distortion-free, ideal device under test, the differential phase is zero. However, for a practical device, the above function is variable. Practical devices are characterized by their differential phase distortion (DP), which refers to the difference between the two extreme values of the above function, usually expressed in degrees, 39
GB 11299.4—89
= gmax - pmin
Note: When using a lower frequency (e.g., a few Hz) test signal to measure the differential phase, this measurement can also reflect the change in group delay. In practice, the group delay of the measurement device is usually scaled in nanoseconds
The group delay is proportional to the ratio of the differential phase to the test signal frequency. When using a higher frequency (e.g., a few MHz) test signal, the differential phase scale (degrees) should be used.
4.2.2 Measurement method
Figure 1 shows a typical measurement device configuration, which also includes the measurement of differential gain/nonlinearity. The part of the linear distortion. When measuring the differential phase, the switch should be placed in the phase detector position. The baseband input signal added to the device under test is a composite signal, formed by superimposing a sinusoidal test signal on a slowly varying sweep signal. At the baseband output of the device under test, the test signal component is separated and added to a phase detector. The output of the phase detector is proportional to the phase change of the test signal and is used as the vertical deflection voltage displayed by the oscilloscope. The horizontal deflection voltage of the oscilloscope can be obtained directly from the sweep signal, or if the device under test contains an IF/RF section. The scan signal is low frequency and its amplitude is selected to cover the dynamic range of the device under test. The amplitude of the test signal should be much smaller than the amplitude of the scan signal so that only a relatively small part of the characteristic curve under test is examined at any moment to obtain a smaller average error. 4.2.3 Result Representation
It is best to use a photograph of the oscilloscope display or a curve recorded by an XY recorder to represent the differential phase distortion. Scale the two axes appropriately, the horizontal axis with the scan voltage scale, and if the device under test contains a modulator and demodulator, the horizontal axis with the scan voltage scale. Frequency deviation scale. Alternatively, this distortion may be expressed as the difference in degrees between the two extreme values of the function, together with the sweep range (V or MHz). 4.2.4 Details to be specified
When this measurement is required, the equipment specifications shall include the following: frequency of the test signal;
frequency of the sweep signal;
sweep amplitude (V, peak-to-peak), or sweep bandwidth (MHz, peak-to-peak); d.
maximum permissible differential phase distortion (degrees). 5 Reference material
5.1 CCIR Recommendation 380--3 (vol iX): Interconnection at baseband Irequencies lor radio-relay systems lor telephony using frcqjucency-division multiplex
5.2 CCIR Recommendation 567--1 (vol XIl) Transmission performance of television rircuits designctfor use in international connections.40
With signal generator
GB11299.4
Measuring bridge
Equipment under test
Selected level meter
Figure 1 Equipment configuration for measuring return loss using the point-by-point measurement method Equipment under test
With frequency-sweeping signal generator
Measuring bridge
Sweep control
Selected level meter
Current output
Sweep voltage
Fluctuator
Figure 2 Equipment configuration for measuring return loss using the swept frequency method Y
Test signal generator
Sweep conduction generator
Baseband signal generatorWww.bzxZ.net
GB11299.4-89
Subtractor!
Attenuator 2
Equipment under test
Frequency-selective meter
Figure 3 Equipment configuration for measuring amplitude/frequency characteristics Light-modulated detector
Equipment under test
Band-pass filter
Phase-modulated detector
Oscilloscope display
Figure 4 Equipment configuration for measuring differential gain/nonlinear distortion and differential phase distortion Additional remarks
This standard was drafted by Nanjing Radio Factory. 422 Measurement Methods
Figure 4 shows a typical measurement equipment configuration, including the section for measuring differential phase/group delay. When measuring differential gain/nonlinear distortion, the switch should be placed in the position of the AM detector. The baseband input signal applied to the device under test is a composite signal, formed by superimposing a sinusoidal test signal on a sweep signal. At the baseband output of the device under test, the test signal component is separated and applied to an envelope detector. The output of the envelope detector is proportional to the amplitude of the test signal and is used as the vertical deflection voltage displayed by the oscilloscope; the horizontal deflection voltage of the oscilloscope can be obtained directly from the sweep signal. If the device under test contains an IF/RF section, it can also be obtained by demodulation from the IF signal. The sweep signal is low-frequency and its amplitude is selected to cover the dynamic range of the device under test. The amplitude of the test signal should be much smaller than that of the sweep signal so that only a relatively small part of the characteristic curve under test is investigated at any instant, so as to obtain a smaller average error. The test signal frequency is generally always much higher than the sweep signal frequency, and its selection depends on the characteristics of the part of the device under test to be evaluated. If only the nonlinear effects of the baseband portion of the modulator/demodulator are to be evaluated, a lower frequency (e.g. 50 to 500 kHz) is chosen and the function measured is called nonlinearity. However, if the effects of nonlinearity of the carrier and baseband portions are to be evaluated, a higher frequency (e.g. 112 MHz) is used and the function measured is called differential gain. 4.1.3 Presentation of results
Differential gain/nonlinearity distortion is best presented as a photograph of an oscilloscope display or a curve recorded by an XY recorder. Scale the two axes appropriately, the horizontal axis in terms of sweep voltage or, if the equipment under test includes a modulator and demodulator, in terms of frequency deviation. Alternatively, this distortion may be expressed as a percentage of the difference between the two extreme values of the function, with the sweep range (in megahertz) given. 4.1.4 Details to be specified
When this measurement is required, the equipment specifications shall include the following:
b. Frequency of the test signal;
c. Frequency of the sweep signal;
d. Sweep amplitude (volts, peak-to-peak), or sweep bandwidth (MHz, peak-to-peak); d. Maximum differential gain/percentage of nonlinear distortion allowed. 4.2 Differential Phase/Group Delay
4.2.1 Definitions and General Considerations
Differential phase refers to the phase change of a small-amplitude, high-frequency sinusoidal signal (test signal) as a function of the instantaneous value of a large-amplitude, low-frequency signal (sweep signal) transmitted simultaneously on the same channel. The differential phase can be defined as a function of the instantaneous values given by the following equation: DP(X) (X) —
Where: DPX differential phase;
X instantaneous value of the input sweep signal;
X) — phase of the output test signal, which is a function of; (8)
, — phase of the output test signal when the sweep signal is zero. For a distortion-free, ideal device under test, the differential phase is zero. However, for a practical device, the above function is variable. Practical devices are characterized by their differential phase distortion (DP), which refers to the difference between the two extreme values of the above function, usually expressed in degrees, 39
GB 11299.4—89
= gmax - pmin
Note: When using a lower frequency (e.g., a few Hz) test signal to measure the differential phase, this measurement can also reflect the change in group delay. In practice, the group delay of the measurement device is usually scaled in nanoseconds
The group delay is proportional to the ratio of the differential phase to the test signal frequency. When using a higher frequency (e.g., a few MHz) test signal, the differential phase scale (degrees) should be used.
4.2.2 Measurement method
Figure 1 shows a typical measurement device configuration, which also includes the measurement of differential gain/nonlinearity. The part of the linear distortion. When measuring the differential phase, the switch should be placed in the phase detector position. The baseband input signal added to the device under test is a composite signal, formed by superimposing a sinusoidal test signal on a slowly varying sweep signal. At the baseband output of the device under test, the test signal component is separated and added to a phase detector. The output of the phase detector is proportional to the phase change of the test signal and is used as the vertical deflection voltage displayed by the oscilloscope. The horizontal deflection voltage of the oscilloscope can be obtained directly from the sweep signal, or if the device under test contains an IF/RF section. The scan signal is low frequency and its amplitude is selected to cover the dynamic range of the device under test. The amplitude of the test signal should be much smaller than the amplitude of the scan signal so that only a relatively small part of the characteristic curve under test is examined at any moment to obtain a smaller average error. 4.2.3 Result Representation
It is best to use a photograph of the oscilloscope display or a curve recorded by an XY recorder to represent the differential phase distortion. Scale the two axes appropriately, the horizontal axis with the scan voltage scale, and if the device under test contains a modulator and demodulator, the horizontal axis with the scan voltage scale. Frequency deviation scale. Alternatively, this distortion may be expressed as the difference in degrees between the two extreme values of the function, together with the sweep range (V or MHz). 4.2.4 Details to be specified
When this measurement is required, the equipment specifications shall include the following: frequency of the test signal;
frequency of the sweep signal;
sweep amplitude (V, peak-to-peak), or sweep bandwidth (MHz, peak-to-peak); d.
maximum permissible differential phase distortion (degrees). 5 Reference material
5.1 CCIR Recommendation 380--3 (vol iX): Interconnection at baseband Irequencies lor radio-relay systems lor telephony using frcqjucency-division multiplex
5.2 CCIR Recommendation 567--1 (vol XIl) Transmission performance of television rircuits designctfor use in international connections.40
With signal generator
GB11299.4
Measuring bridge
Equipment under test
Selected level meter
Figure 1 Equipment configuration for measuring return loss using the point-by-point measurement method Equipment under test
With frequency-sweeping signal generator
Measuring bridge
Sweep control
Selected level meter
Current output
Sweep voltage
Fluctuator
Figure 2 Equipment configuration for measuring return loss using the swept frequency method Y
Test signal generator
Sweep conduction generator
Baseband signal generator
GB11299.4-89
Subtractor!
Attenuator 2
Equipment under test
Frequency-selective meter
Figure 3 Equipment configuration for measuring amplitude/frequency characteristics Light-modulated detector
Equipment under test
Band-pass filter
Phase-modulated detector
Oscilloscope display
Figure 4 Equipment configuration for measuring differential gain/nonlinear distortion and differential phase distortion Additional remarks
This standard was drafted by Nanjing Radio Factory. 423. Presentation of results
It is best to present the differential gain/nonlinear distortion by a photograph of an oscilloscope display or a curve recorded by an XY recorder. Scale the two axes appropriately, the horizontal axis in terms of swept voltage and, if the equipment under test includes a modulator and demodulator, in terms of frequency deviation. Alternatively, the distortion may be expressed as a percentage of the difference between the two extreme values of the function, with the sweep range (in megahertz) given. 4.1.4. Details to be specified
When this measurement is required, the equipment specifications shall include the following: Frequency of the test signal:
b. Frequency of the sweep signal;
c. Sweep amplitude (volts, peak-to-peak), or sweep bandwidth (megahertz, peak-to-peak); d. Maximum permitted differential gain/nonlinear distortion in percentage. 4.2 Differential Phase/Group Delay
4.2.1 Definitions and General Considerations
Differential phase refers to the phase change of a small-amplitude high-frequency sinusoidal signal (test signal) as a function of the instantaneous value of a large-amplitude low-frequency signal (sweep signal) transmitted simultaneously on the same channel. The differential phase can be defined as a function of the instantaneous value given by the following equation: DP(X) (X) —
where: DPX is the differential phase;
X is the instantaneous value of the input sweep signal;
X) is the phase of the output test signal, which is a function of (8)
, - the phase of the output test signal when the sweep signal is zero. For a distortion-free, ideal device under test, the differential phase is zero. However, for a practical device, the above function varies. Practical equipment is characterized by its differential phase distortion (DP), which is the difference between the two extreme values of the above function, usually expressed in degrees, 39
GB 11299.4—89
= gmax - pmin
Note: When the differential phase is measured with a test signal of lower frequency (e.g., a few Hz), this measurement can also reflect the change in group delay. In practice, the group delay of the measuring equipment is usually scaled in nanoseconds
The group delay is proportional to the ratio of the differential phase to the test signal frequency. When using a test signal of higher frequency (e.g., a few MHz), the differential phase scale (degrees) is used.
4.2.2 Measurement method
Figure 1 shows a typical measurement equipment configuration, which also includes the measurement of differential gain/nonlinearity. The part of the linear distortion. When measuring the differential phase, the switch should be placed in the phase detector position. The baseband input signal added to the device under test is a composite signal, formed by superimposing a sinusoidal test signal on a slowly varying sweep signal. At the baseband output of the device under test, the test signal component is separated and added to a phase detector. The output of the phase detector is proportional to the phase change of the test signal and is used as the vertical deflection voltage displayed by the oscilloscope. The horizontal deflection voltage of the oscilloscope can be obtained directly from the sweep signal, or if the device under test contains an IF/RF section. The scan signal is low frequency and its amplitude is selected to cover the dynamic range of the device under test. The amplitude of the test signal should be much smaller than the amplitude of the scan signal so that only a relatively small part of the characteristic curve under test is examined at any moment to obtain a smaller average error. 4.2.3 Result Representation
It is best to use a photograph of the oscilloscope display or a curve recorded by an XY recorder to represent the differential phase distortion. Scale the two axes appropriately, the horizontal axis with the scan voltage scale, and if the device under test contains a modulator and demodulator, the horizontal axis with the scan voltage scale. Frequency deviation scale. Alternatively, this distortion may be expressed as the difference in degrees between the two extreme values of the function, together with the sweep range (V or MHz). 4.2.4 Details to be specified
When this measurement is required, the equipment specifications shall include the following: frequency of the test signal;
frequency of the sweep signal;
sweep amplitude (V, peak-to-peak), or sweep bandwidth (MHz, peak-to-peak); d.
maximum permissible differential phase distortion (degrees). 5 Reference material
5.1 CCIR Recommendation 380--3 (vol iX): Interconnection at baseband Irequencies lor radio-relay systems lor telephony using frcqjucency-division multiplex
5.2 CCIR Recommendation 567--1 (vol XIl) Transmission performance of television rircuits designctfor use in international connections.40
With signal generator
GB11299.4
Measuring bridge
Equipment under test
Selected level meter
Figure 1 Equipment configuration for measuring return loss using the point-by-point measurement method Equipment under test
With frequency-sweeping signal generator
Measuring bridge
Sweep control
Selected level meter
Current output
Sweep voltage
Fluctuator
Figure 2 Equipment configuration for measuring return loss using the swept frequency method Y
Test signal generator
Sweep conduction generator
Baseband signal generator
GB11299.4-89
Subtractor!
Attenuator 2
Equipment under test
Frequency-selective meter
Figure 3 Equipment configuration for measuring amplitude/frequency characteristics Light-modulated detector
Equipment under test
Band-pass filter
Phase-modulated detector
Oscilloscope display
Figure 4 Equipment configuration for measuring differential gain/nonlinear distortion and differential phase distortion Additional remarks
This standard was drafted by Nanjing Radio Factory. 423. Presentation of results
It is best to present the differential gain/nonlinear distortion by a photograph of an oscilloscope display or a curve recorded by an XY recorder. Scale the two axes appropriately, the horizontal axis in terms of swept voltage and, if the equipment under test includes a modulator and demodulator, in terms of frequency deviation. Alternatively, the distortion may be expressed as a percentage of the difference between the two extreme values of the function, with the sweep range (in megahertz) given. 4.1.4. Details to be specified
When this measurement is required, the equipment specifications shall include the following: Frequency of the test signal:
b. Frequency of the sweep signal;
c. Sweep amplitude (volts, peak-to-peak), or sweep bandwidth (megahertz, peak-to-peak); d. Maximum permitted differential gain/nonlinear distortion in percentage. 4.2 Differential Phase/Group Delay
4.2.1 Definitions and General Considerations
Differential phase refers to the phase change of a small-amplitude high-frequency sinusoidal signal (test signal) as a function of the instantaneous value of a large-amplitude low-frequency signal (sweep signal) transmitted simultaneously on the same channel. The differential phase can be defined as a function of the instantaneous value given by the following equation: DP(X) (X) —
where: DPX is the differential phase;
X is the instantaneous value of the input sweep signal;
X) is the phase of the output test signal, which is a function of (8)
, - the phase of the output test signal when the sweep signal is zero. For a distortion-free, ideal device under test, the differential phase is zero. However, for a practical device, the above function varies. Practical equipment is characterized by its differential phase distortion (DP), which is the difference between the two extreme values of the above function, usually expressed in degrees, 39
GB 11299.4—89
= gmax - pmin
Note: When the differential phase is measured with a test signal of lower frequency (e.g., a few Hz), this measurement can also reflect the change in group delay. In practice, the group delay of the measuring equipment is usually scaled in nanoseconds
The group delay is proportional to the ratio of the differential phase to the test signal frequency. When using a test signal of higher frequency (e.g., a few MHz), the differential phase scale (degrees) is used.
4.2.2 Measurement method
Figure 1 shows a typical measurement equipment configuration, which also includes the measurement of differential gain/nonlinearity. The part of the linear distortion. When measuring the differential phase, the switch should be placed in the phase detector position. The baseband input signal added to the device under test is a composite signal, formed by superimposing a sinusoidal test signal on a slowly varying sweep signal. At the baseband output of the device under test, the test signal component is separated and added to a phase detector. The output of the phase detector is proportional to the phase change of the test signal and is used as the vertical deflection voltage displayed by the oscilloscope. The horizontal deflection voltage of the oscilloscope can be obtained directly from the sweep signal, or if the device under test contains an IF/RF section. The scan signal is low frequency and its amplitude is selected to cover the dynamic range of the device under test. The amplitude of the test signal should be much smaller than the amplitude of the scan signal so that only a relatively small part of the characteristic curve under test is examined at any moment to obtain a smaller average error. 4.2.3 Result Representation
It is best to use a photograph of the oscilloscope display or a curve recorded by an XY recorder to represent the differential phase distortion. Scale the two axes appropriately, the horizontal axis with the scan voltage scale, and if the device under test contains a modulator and demodulator, the horizontal axis with the scan voltage scale. Frequency deviation scale. Alternatively, this distortion may be expressed as the difference in degrees between the two extreme values of the function, together with the sweep range (V or MHz). 4.2.4 Details to be specified
When this measurement is required, the equipment specifications shall include the following: frequency of the test signal;
frequency of the sweep signal;
sweep amplitude (V, peak-to-peak), or sweep bandwidth (MHz, peak-to-peak); d.
maximum permissible differential phase distortion (degrees). 5 Reference material
5.1 CCIR Recommendation 380--3 (vol iX): Interconnection at baseband Irequencies lor radio-relay systems lor telephony using frcqjucency-division multiplex
5.2 CCIR Recommendation 567--1 (vol XIl) Transmission performance of television rircuits designctfor use in international connections.40
With signal generator
GB11299.4
Measuring bridge
Equipment under test
Selected level meter
Figure 1 Equipment configuration for measuring return loss using the point-by-point measurement method Equipment under test
With frequency-sweeping signal generator
Measuring bridge
Sweep control
Selected level meter
Current output
Sweep voltage
Fluctuator
Figure 2 Equipment configuration for measuring return loss using the swept frequency method Y
Test signal generator
Sweep conduction generator
Baseband signal generator
GB11299.4-89
Subtractor!
Attenuator 2
Equipment under test
Frequency-selective meter
Figure 3 Equipment configuration for measuring amplitude/frequency characteristics Light-modulated detector
Equipment under test
Band-pass filter
Phase-modulated detector
Oscilloscope display
Figure 4 Equipment configuration for measuring differential gain/nonlinear distortion and differential phase distortion Additional remarks
This standard was drafted by Nanjing Radio Factory. 422 Measurement Methods
Figure 1 shows a typical measurement equipment configuration, which also includes the part for measuring differential gain/nonlinear distortion. When measuring differential phase, the switch should be placed in the phase detector position. The baseband input signal applied to the device under test is a composite signal, formed by superimposing a sinusoidal test signal on a slowly varying sweep signal. At the baseband output of the device under test, the test signal component is separated and applied to a phase detector, the output of which is proportional to the phase change of the test signal and is used as the vertical deflection voltage displayed by the oscilloscope. The horizontal deflection voltage of the oscilloscope can be obtained directly from the sweep signal, or it can be obtained by demodulating the IF signal if the device under test contains an IF/RF part.
The sweep signal is low frequency and its amplitude is selected to cover the dynamic range of the device under test. The amplitude of the test signal should be much smaller than the amplitude of the sweep signal so that only a relatively small part of the measured characteristic curve is examined at any instant to obtain a small average error. 4.2.3 Presentation of results
Differential phase distortion is best represented by a photograph of an oscilloscope display or a curve recorded by an XY recorder. Scale the two axes appropriately, the horizontal axis in swept voltage or, if the equipment under test contains a modulator and demodulator, in frequency deviation. Alternatively, the distortion may be expressed as the difference in degrees between the two extreme values of the function, together with the sweep range (V or MHz). 4.2.4 Details to be specified
When this measurement is required, the equipment specifications shall include the following: frequency of the test signal;
frequency of the sweep signal;
sweep amplitude (V, peak-to-peak), or sweep bandwidth (MHz, peak-to-peak); d.
maximum differential phase distortion allowed (degrees). 5 Reference materials
5.1CCIR Recommendation 380--3(vol iX):Interconnection at baseband Irequencies lor radio-relay systems lor telephony using frcqjucency-division multiplex
5.2 CCIR Recommendation 567--1(vol XIl)Transmission performance of television rircuits designctfor use in international connections.40
With signal generator
GB11299.4
Measuring bridge
Equipment under test
Selected level meter
Figure 1 Equipment configuration for measuring return loss using the point-by-point measurement method Equipment under test
With frequency-sweeping signal generator
Measuring bridge
Sweep control
Selected level meter
Current output
Sweep voltage
Fluctuator
Figure 2 Equipment configuration for measuring return loss using the swept frequency method Y
Test signal generator
Sweep conduction generator
Baseband signal generator
GB11299.4-89
Subtractor!
Attenuator 2
Equipment under test
Frequency-selective meter
Figure 3 Equipment configuration for measuring amplitude/frequency characteristics Light-modulated detector
Equipment under test
Band-pass filter
Phase-modulated detector
Oscilloscope display
Figure 4 Equipment configuration for measuring differential gain/nonlinear distortion and differential phase distortion Additional remarks
This standard was drafted by Nanjing Radio Factory. 422 Measurement Methods
Figure 1 shows a typical measurement equipment configuration, which also includes the part for measuring differential gain/nonlinear distortion. When measuring differential phase, the switch should be placed in the phase detector position. The baseband input signal applied to the device under test is a composite signal, formed by superimposing a sinusoidal test signal on a slowly varying sweep signal. At the baseband output of the device under test, the test signal component is separated and applied to a phase detector, the output of which is proportional to the phase change of the test signal and is used as the vertical deflection voltage displayed by the oscilloscope. The horizontal deflection voltage of the oscilloscope can be obtained directly from the sweep signal, or it can be obtained by demodulating the IF signal if the device under test contains an IF/RF part.
The sweep signal is low frequency and its amplitude is selected to cover the dynamic range of the device under test. The amplitude of the test signal should be much smaller than the amplitude of the sweep signal so that only a relatively small part of the measured characteristic curve is examined at any instant to obtain a small average error. 4.2.3 Presentation of results
Differential phase distortion is best represented by a photograph of an oscilloscope display or a curve recorded by an XY recorder. Scale the two axes appropriately, the horizontal axis in swept voltage or, if the equipment under test contains a modulator and demodulator, in frequency deviation. Alternatively, the distortion may be expressed as the difference in degrees between the two extreme values of the function, together with the sweep range (V or MHz). 4.2.4 Details to be specified
When this measurement is required, the equipment specifications shall include the following: frequency of the test signal;
frequency of the sweep signal;
sweep amplitude (V, peak-to-peak), or sweep bandwidth (MHz, peak-to-peak); d.
maximum differential phase distortion allowed (degrees). 5 Reference materials
5.1CCIR Recommendation 380--3(vol iX):Interconnection at baseband Irequencies lor radio-relay systems lor telephony using frcqjucency-division multiplex
5.2 CCIR Recommendation 567--1(vol XIl)Transmission performance of television rircuits designctfor use in international connections.40
With signal generator
GB11299.4
Measuring bridge
Equipment under test
Selected level meter
Figure 1 Equipment configuration for measuring return loss using the point-by-point measurement method Equipment under test
With frequency-sweeping signal generator
Measuring bridge
Sweep control
Selected level meter
Current output
Sweep voltage
Fluctuator
Figure 2 Equipment configuration for measuring return loss using the swept frequency method Y
Test signal generator
Sweep conduction generator
Baseband signal generator
GB11299.4-89
Subtractor!
Attenuator 2
Equipment under test
Frequency-selective meter
Figure 3 Equipment configuration for measuring amplitude/frequency characteristics Light-modulated detector
Equipment under test
Band-pass filter
Phase-modulated detector
Oscilloscope display
Figure 4 Equipment configuration for measuring differential gain/nonlinear distortion and differential phase distortion Additional remarks
This standard was drafted by Nanjing Radio Factory. 42
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