GB/T 4958.9-1988 Measurement methods for equipment used in terrestrial radio-relay systems Part 2: Subsystem measurements Section 9: Standby channel switching equipment
Some standard content:
National Standard of the People's Republic of China
GB/T4958.9—1988
idtIEC487—2—2：1981
Methods of measurement for equipment used in terrestrial Radio-relay systems
Part 2:Measurements for sub-systemsSection Nine-Stand-by Channel Switching equipmentPromulgated on March 28, 1988
Implemented on February 1, 1989
Ministry of Posts and Telecommunications of the People's Republic of China
National Standard of the People's Republic of China
Methods of measurement for equipment used in terrestrial Radio-relay systemsPart 2:Measurements for sub-systemsSection Nine-Stand-by Channel Switching equipment terrestrialRadiorelaysystems
Part 2:Measurements for sub-systemsSection Nine-Stand-by Channel Switching equipmentUDC
621.396：
621.317.08
GB/T4958.9—1988
IEC487—2—2(1981)
The standard for measurement methods for equipment used in terrestrial radiorelay systems includes three parts. Part 1: Measurements common to sub-systems and simulation systems. Part 2: Measurements for sub-systems. Part 3: Measurements for simulation systems. Each part includes several sub-standards. "Stand-by channel switching equipment" is a sub-standard in Part 2. The backup channel switching equipment is equivalent to the international standard IEC--487-2--2 "Measurement methods for equipment used in ground radio relay systems Part 2: Subsystem measurements Section 2 Backup channel switching equipment" (now IEC487-2-2 [19817) 1 Scope
This section deals with the performance measurement of each subsystem used for backup channel switching. This section gives the measurement methods for the following characteristics: the transmission characteristics of the switching subsystem inserted in the transmission channel baseband or intermediate frequency, the operation and conversion time of the pilot and noise detector subsystem and the switching switch.
2 Introduction
The number of protected working channels and the number of backup channels are expressed as (m+n): Where: m is the number of working channels, usually one or more. n is the number of backup channels, usually one or two. When m and n are 1, there can be multiple backup methods. In the first mode, the communication service is added to two channels at the same time, so that the transmitter does not need to switch (i.e., dual-channel operation). In the second mode, the communication service is added to only one channel, and the second channel is used as a backup for the first channel. If the operation of the first channel is satisfactory, the second channel can also be used for other purposes. For example: for transmitting television. In this mode, switching equipment must be equipped in each terminal station in the system. Moreover, the service of the working channel takes precedence over the service of the backup channel. Note: In another case, the working channel and the backup channel use the same RF frequency, and each transmitter and receiver needs to have a switching device. In all backup modes (except the mode of "Note" above), the (m+n) channels work in different RF frequency modes, and the backup switching is performed at baseband or intermediate frequency. When
m>1, the backup channel can adopt various priority modes, which are not considered here. In general, two-way communication is required between the switching sections to ensure the correct switching operation sequence (see Reference 1). However, in a dual-channel switching system where the backup channel is not used for other services, the return control signal channel is not required. Note: For dual-channel and hot standby systems, additional measurements are required in accordance with Section 6 of Part 2 of this series of standards, "Diversity dual-channel and hot standby equipment". Multi-channel switching systems include:
Approved by the Ministry of Posts and Telecommunications of the People's Republic of China on March 28, 1988, and implemented on February 1, 1989
GB/T4958.9-1988
-A judgment and logic subsystem to determine whether switching is required; a two-way communication system between switching sections; a switching equipment and auxiliary equipment.
The study of the characteristics of multi-channel switching equipment has not yet achieved standardization of the connection of various switching systems (see reference document 3). Due to the great differences between various standby switching systems, it is impossible to list the measurement methods for each one. Therefore, this section only gives the methods selected for some typical equipment. What tests need to be done should be agreed upon by the supplier and the buyer. In order to test the standby switching equipment, some measurement items need to use all or part of the equipment used in a relay section of the emulation radio system. In this case, the simulated radio system should be carefully adjusted to ensure that the performance of the equipment meets the requirements of the technical specifications. 3 Transmission characteristics
Since the switching equipment is connected in series with the subsystems of the radio relay system. Therefore, it is necessary to measure the transmission characteristics of the switching equipment itself. The measurement methods of transmission characteristics are given in Part 1 and Part 3 of this series of standards. The transmission characteristics of the switching equipment can be measured from intermediate frequency to intermediate frequency or from baseband to baseband. The measurement is made in the simulated system with and without the switching equipment connected to determine the impact of the switching equipment on the transmission characteristics. Each path should be measured separately. Note: The loss or gain of each switching device should be taken into account. 4 Isolation between switch ports
4.1 Definition and general considerations
The isolation between any two ports of a switch (only one of which is a signal path) is: the ratio of the two port levels when all ports are terminated with their nominal impedance, expressed in decibels. Each port is measured with all other ports in turn. 4.2 Measurement method
Measure isolation using the swept frequency method. Apply the swept frequency signal generator signal to one port of the intermediate frequency or baseband. Then connect the receiver to the two ports of the isolation to be measured in turn and record the minimum level difference. During the measurement, the receiver should be properly matched to the port to which it is connected. The other ports should also be terminated with matching loads. Care should be taken to ensure that the output of the signal generator does not overload the switch. Alternatively, the point-by-point method can be used.
Note: For this test, the required accuracy is not high (e.g. ±2dB). 4.3 Result presentation method
The measurement results should be given in the following way: "When the frequency between Y and Z ports is fkHz (or MHz), the minimum isolation between the ports is xdB". If required, the isolation/frequency characteristic curve or the corresponding oscilloscope display photo can also be included. 4.4 Details to be specified
In the equipment detail specification, the following items should be included as required: a. The port to be measured;
b. The input level to be used,
c. The frequency range to be measured;
d. The required isolation (e.g. 80 dB).
5 Criteria for switching
5.1—General considerations
Two switching criteria are usually used, namely a specified continuous pilot level change (see references) and/or a specified noise level change in the noise measurement narrowband (see clause 5.3.2).
The pilot and noise detectors shall be measured under the following conditions to determine that both detectors start and reset at the specified pilot level and the specified noise signal level:
—without baseband signal;
—with baseband signal at rated level;
—with baseband signal at overload modulation level. GB/T4958.9—1988
It is also necessary to check that the noise detector does not produce vibration when it reaches a point close to the working or recovery noise level. It is also necessary to check the impact of the noise detector on the pilot level when it is in the startup state and the impact of the pilot detector on the noise power when it is in the startup state. Note: ① In most cases, the pilot detector is started at a level lower than the normal level point. However, in some cases, the pilot detector is started under both conditions below and above the normal level.
② A step attenuator should not be used to adjust the pilot or noise level. Because the instantaneous interruption of this attenuator when changing levels can cause the detector to malfunction.
③ Due to the volatility and randomness of noise, all measurement items including the noise source should be repeated many times to determine the average startup level of the detector.
5.2 Startup and recovery level of pilot detector 5.2.1 Definition
The start-up level of the pilot detector is the signal level at the pilot input when the pilot detector is started and changes from the "normal" state to the "abnormal" state.
The reset level is the signal level at the pilot input when the pilot detector indicates that it has recovered from the "abnormal" state to the "normal" state. Note: ① The start-up level is usually adjustable within the specified range. ② The reset level is specified as x dB higher or lower than the start-up level, depending on the situation. Sometimes x can also be adjusted. 5.2.2 Measurement method
There are two methods for measuring the start-up and reset levels of the pilot detector: if the detector is sampled from the rated baseband output, all tests are performed at the baseband according to the method shown in Figure 1a. If the detector monitors its pilot at the intermediate frequency with the help of a demodulator, it is appropriate to use the method shown in Figure 1b.
In both measurement methods, the pilot signal is generated by an external signal generator. The output level of the signal generator starts from the nominal value, First change continuously in one direction until the detector operates, and then change in the other direction until the detector recovers. If the pilot detector operates at a level higher or lower than the normal level, their start-up level and recovery level must be measured in both cases. Before starting the measurement for intermediate frequency switching (see Figure 1b), the frequency deviation caused by the external pilot should be adjusted to the nominal value. 5.2.3 Method of expressing results
The measured start-up level and recovery level should be filled in the table. 5.2.4 Details to be specified
In the detailed specifications of the equipment, the following items should be included as required: a. Required start-up level range (for example, -8 to -4 dB relative to the nominal pilot level); b. Required recovery level range (for example, 1 to 3 dB higher than the start-up level); c. Pilot signal frequency.
5.3 Noise Detector startup and recovery levels 5.3.1 Definitions and general considerations
The startup level of a noise detector is the noise level when the indication of the detector changes from a "normal" state to an "abnormal" state as required by the baseband technical conditions.
The recovery level is the noise level when the indication of the noise detector returns to a "normal" state from an "abnormal" state as required by the same baseband technical conditions.
Note: ①The startup level is generally adjustable within the specified range. ②The recovery level is x dB lower than the startup level, and sometimes x can also be adjusted. The bandpass filter of the noise detector is usually assembled as one piece with the detector. Therefore, the test point behind the filter cannot be used. The startup level is expressed by the equivalent noise power measured in the specified baseband part. The noise power in the specified frequency band directly represents the system when switching occurs. The quality of system performance. There is generally a clear relationship between this noise power and the noise power at the input of the noise detector. 3
GB/T4958.9—1988
In telephone systems, the specified frequency band is generally the highest measurement channel (see reference). In television systems, it is the entire video band (see reference ③). However, the measurement method for telephone systems is also applicable to measuring television systems. Because when switching occurs, there is a fixed relationship between the thermal noise related to the path loss under the two transmission conditions. 5.3.2 Measurement method
The start-up level and reset level of the noise detector are best measured using the "noise receiver" method. In this method, the noise source is a normal system receiver. The input signal size can be changed to make its noise output variable. The block diagram of the test equipment is shown in Figure 2a or Figure 26. The attenuation of the intermediate frequency or radio frequency attenuator (depending on which one is more convenient) is continuously increased until the noise detector starts, and then the attenuation is reduced until the detector recovers to its original state.
However, if some inter-phase type equipment is to be measured, the method shown in Figure 3a or 3b (depending on the measurement) may be more convenient for some other measurements to be made. In this method, the noise source is provided by a white noise generator, the output level of which is gradually increased until the noise detector is activated, and then the output level of the white noise generator is reduced until the detector is restored. The bandwidth of the noise source should include the frequencies of the pilot detector and the noise detector. However, its bandwidth should be limited (for example, a 2700-channel low-pass filter may be used to test an 1800-channel system). Regardless of which method is used, the noise level measured on the white noise receiver when the detector state change is caused should be recorded.
The attack and restore levels measured using the method of Figure 2a or Figure 2b may differ by several dB compared to the attack and restore levels measured using the method of Figure 3a or Figure 3b. This is due to the fact that the noise power in the detector passband is different from the noise power in the measurement narrowband in both methods. Once this level difference has been determined for the particular type of equipment being measured, the method of Figure 3a or Figure 3b can be used to measure the attack level and the reset level with greater accuracy than the measurement using the block diagram of Figure 2a or 2b. NOTE: Some systems use a narrow band of noise centered on the pilot tone and detect a band of noise around the pilot tone. For such systems, the pilot tone level must be checked to be nominal whenever any measurement is made on the noise detector. 5.3.3 Method of Presentation of Results
The measured attack level and reset level shall be filled in a table. 5.3.4 Details to be Specified
The following items shall be included in the equipment detail specification as required: a. The center frequency of the noise measurement channel in the baseband; b. The required attack level in the noise measurement channel (e.g. 20000pWp to 250000pWp); c. The required reset level (e.g. 5±1dB lower than the measured attack level); d. The measurement method used (i.e. white noise method or noise receiver method). 5.4 Effect of Baseband Overload on Pilot Detector Operation 5.4.1 General Considerations
Since switching malfunctions are undesirable, the effect of adding signal load in the transmission band on the pick-up level of the pilot detector is generally tested. This effect is mainly due to interference caused by baseband signal distortion at the pilot frequency. The purpose of this measurement is to determine whether several types of baseband signals, when slightly above the nominal level, cause only small interference (e.g. 1 dB) on the pick-up and reset levels of the pilot detector band. 5.4.2 Measurement Method
The effect of baseband loading on the pick-up state of the pilot detector is measured using the block diagram shown in Figure 1a or Figure 1b. It is very important to adjust the equipment correctly, especially the sensitivity of the modulator and demodulator, the total linearity and group delay in Figure 1b, and the pick-up and reset levels of the detector of Figure 1a or Figure 1b. It is important that the modulator of Figure 1b does not introduce any parasitic components into the pilot detector band. After completing the measurement of the start level and the reset level (see 5.2.2), add various baseband signals in turn for measurement and record the level of each signal in the various baseband signals, which causes a small change (for example 1 dB) to the start level and the reset level. Note: Usually, using a correctly adjusted system, it is only necessary to check that the change in the start level and the reset level caused by the maximum baseband signal level used is less than the specified maximum change.
The following baseband signals can be used:
a. White noise with appropriate frequency band and level, b. The test signal shown in Figure 13 of Section 3 of Part 3 of this series of standards for the measurement of black-and-white and color television transmissions. 4
GB/T4958.9—1988
c. A sinusoidal signal of specified level and frequency, such as a sinusoidal signal of half or one-third of the pilot frequency. Note: ① The baseband test signal used should have no effect on the level of the pilot signal used; ② A band-stop filter (the stopband is the pilot frequency) may be required at the output of the test signal generator to ensure that out-of-band signal components do not enter the test system.
When using the baseband test signal in item c, the harmonics of the pilot frequency at the output of the test signal generator should be more than 50dB lower than the required output level. The signal frequency should be set to produce a low beat frequency between the pilot frequency and the harmonic interference frequency. The signal frequency should make the corresponding harmonic frequency fall within the passband of the pilot detector.
5.4.3 Method of expressing results
The measurement results should be expressed in an explanatory manner: When the start level and the reset level are changed (for example, 1dB), the level of each baseband signal is expressed in total noise as follows:
For white noise signals, use dBm0;
For television signals, use decibels relative to the 1V peak-to-peak level; For sinusoidal signals, use level and frequency. In addition, it should be noted whether the change caused by the maximum baseband signal level used is less than the specified minimum change (e.g. 1 dB). 5.4.4 Details to be specified
In the equipment detailed specification, the following items should be included as required: a. Required pilot detector start level and reset level; b. Baseband test signal used;
c. Emphasis characteristics used (if necessary); d. Minimum level of each baseband signal and the start and reset levels allowed to vary (e.g. 1 dB); e.The maximum baseband level of each added signal (e.g. a white noise signal 6 dB greater than the nominal value, a television test signal 3 dB greater than the nominal value);
f. Pilot signal frequency.
5.5 Effect of baseband overload on the start-up state of the noise detector 5.5.1 General considerations
The test for the effect of baseband overload on the noise detector is similar to that of 5.4, and it should be noted that the possible change in the start-up level of the noise detector at a moderate overload (less than 6B) is less than the change allowed in the equipment detailed specification (e.g. 1 dB). 5.5.2 Measurement method
The effect of baseband overload on the start-up state of the noise detector uses the block diagram shown in Figure 2a or Figure 2b, depending on the switching situation. When measuring the change of the start level, the output level of the test signal generator should be very low, and the IF or RF variable attenuator should be adjusted until the noise level in the measured narrow band is slightly lower than the start level (for example, 1 dB). Then gradually increase the level of the white noise signal or video test signal or a sinusoidal signal with a frequency of half or one-third of the center frequency of the noise detector passband until a false operation occurs or the maximum specified start level of the test signal is reached.
When measuring the change of the reset level, the output level of the test signal generator needs to start from a very low level and then increase the level to the maximum specified level. Repeat the reset level measurement several times. 5.5.3 Method of expressing results
The results should be expressed in a narrative manner, indicating the level of each baseband signal when the start level and reset level change (for example, 1 dB), and the total noise power is expressed in the following units:
For a white noise signal, use dBmO,
For a video test signal, use decibels relative to the peak-to-peak level of 1 V For a sine wave signal, use level and frequency. In addition, it is necessary to state whether the change caused by the maximum baseband signal level used is less than the specified maximum change (for example, 1dB). 5.5.4 Details to be specified
In the detailed equipment specifications, the following items should be included as required:5
GB/T4958.9—1988
a. The center frequency and passband of the noise detector; b. The required start-up level and reset level of the noise detector; c. The various baseband test signals used;
d. The emphasis characteristics used;
e. The minimum level of each baseband signal and the start-up and reset levels allowed to change (for example, 1dB); f. The maximum baseband level of each added signal (for example, when it is greater than the nominal value of 6dB white noise signal, greater than the nominal value of 3dB TV test signal).
5.6 Effect of noise on the pilot detector startup state 5.6.1 General considerations
Since switching malfunctions are undesirable, it is reasonable to measure the startup range of the pilot detector depending on the noise power level. 5.6.2 Measurement method
The measurement block diagram is shown in Figure 2a or Figure 2b and two measurements are made according to the following method. - First, the pilot signal generator is disconnected and the RF or IF attenuation is slowly increased from a low value until the pilot detector malfunctions (or recovers). The noise power level under this condition is measured within the specified passband. - Second, the pilot signal generator is connected and the level is set to the nominal value. The RF or IF attenuation is slowly increased from a low value until the pilot detector malfunctions. Under this condition, the noise level within the specified passband (usually the highest measurement channel) is measured. Note: It must be ensured that the startup is not caused by the influence of the frequency modulation threshold and the pilot rating changes. This effect is checked by connecting a highly selective frequency-selective level meter in parallel with the noise receiver and tuning the meter to the pilot frequency. 5.6.3 Method of Presentation of Results
The results of the test shall be presented in a narrative form, indicating the various noise powers within the passband at which false tripping occurs. Alternatively, it may be stated as the maximum specified noise level at which false tripping does not occur. 5.6.4 Details to be Specified
The following items shall be included as required in the equipment detail specification: a. The required pilot detector pickup and reset levels, b. The emphasis characteristics to be used,
c. The noise power level below which false tripping is not permitted (e.g. telephone channel - 35 dBmOp); d. The frequency of the pilot signal.
5.7 Effect of pilot level on the pickup state of the noise detector 5.7.1 General considerations
During selective fading, the pilot level at the receiving end of a radio-relay system may vary by several dB, depending on the RF band and the RF frequency of the pilot.
Therefore, it is necessary to indicate whether the change of the pilot level within the specified range causes any disturbance in the start-up level and the reset level of the noise detector.
5.7.2 Measurement method
The influence of the pilot level on the working state of the noise detector is measured by the noise receiver method described in 5.3.2. The measurement of the start-up level and the reset level should be carried out under the following pilot signal level conditions. a. Nominal level:
b. Maximum and minimum levels when the start-up level and the reset level of the noise detector are allowed to change (for example, 1dB); c. Various other levels required by the equipment detailed specification. Due to the volatility and randomness of noise, it is necessary to repeat the measurement several times in order to determine the average start-up level when the false operation occurs. 5.7.3 Result presentation method
The measurement results should be presented in a narrative manner, indicating the pilot level value when the start-up level and the reset level of the detector change by a specified small amount (for example, 1dB).
In addition, it can also be stated that within the applied level range, the change of the start level and the reset level does not exceed the specified value. 6
5.7.4 Details to be specified
GB/T4958.9-1988
In the equipment detailed specification, the following items should be included as required: a. Required noise detector start level and reset level; b. Emphasis characteristics used;
c. Maximum and minimum pilot signal levels when the start level and reset level are allowed to change by a small amount (for example, 1dB) (for example, 10dB to 16dB relative to the nominal level, and 10dB relative to the nominal value when there is no pilot); d. Pilot signal frequency.
6 Operating time and conversion time of switching equipment 6.1 Definition and general considerations
The conversion time is the period of time during which the baseband signal at the output end of the radio relay system is interrupted (when the switching switch is working). Since the baseband signal is not interrupted when the transmitting end switches. Therefore, it is only necessary to determine the required switching time at the receiving end of the switching section. The working time is the time taken from the moment when the transmission quality drops significantly to the moment when the switching process starts, to the moment when the switching process is completed (switching to the backup channel). The working time is the sum of a series of time units that cause several subsystems to work. Generally, it includes the following parts of time: - recognition time of fading or failure at the receiving end; - establishment time of the control signal sent to the transmitting end; - transmission time* used by the control signal to reach the transmitting end; - recognition time at the transmitting end (checking the prohibition instruction when necessary): - bridging or switching time at the transmitting end,
- transmission time* used by the control signal to reach the receiving end; - checking time of the received control signal;
- judgment time used to determine whether the switching should be started; actual switching operation time (conversion time). Note: The time unit marked with an asterisk * depends on the distance between the transmitting and receiving ends. For simulated radio relay systems, these factors can be ignored (see reference 2).
The operating time of pilot fault switching is different from the operating time of noise increase switching. Under the first condition (pilot fault), the operating time is almost equal to the interruption time. Under the second condition, the interruption time is equal to the switching time. Therefore, it is generally only necessary to measure the operating time of pilot fault.
The operating time of any particular channel is also determined by the following factors: a. the special circuit structure and state at the moment of switching, b. the priority of the predetermined channels;
c. whether one or two protection channels are available. 6.2 Method of measuring the operating time
To measure the start time, use the measurement block diagram shown in the group of figures or Figure 6. The additional switch in the working channel is triggered by the interruption of the trigger-driven signal to cause the initial switching process. The signal interruption time observed on the oscilloscope is the operating time. For intermediate frequency switching, the interruption signal is observed at the intermediate frequency, and for baseband switching, the interruption signal is observed using a sine wave signal (e.g. 100kHz). The switch S can be a mechanical switch or an electronic switch. The time for the switch S to be on and off for one cycle should be longer than the measured working time to allow for a repeated switching operation. The switching operation repetition frequency of about 10Hz is more appropriate. Because the levels of points P1, P2 and P: on the main signal path and the levels of points P4 and Ps on the control signal path should have specified values, the networks N1, N2 and N3 should all be adjustable. These networks contain attenuators or amplifiers that meet the transmission characteristics requirements. 6.3 Method for measuring switching time
The switching time is in the order of milliseconds for mechanical switches and in the order of microseconds for electronic switches. The measurement block diagram is shown in Figure 5a or Figure 5b.
GB/T4958.9—1988
Since the switching time is determined only by the switch itself and has nothing to do with the signal that causes it to operate, it is appropriate to control the switch with an external trigger signal. The interruption time of the test signal (a sinusoidal signal of about 2MHz can be used) is observed on an oscilloscope. In the case of intermediate frequency switching, in order to obtain the true interruption time, it is best to observe the interruption signal at the baseband rather than at the intermediate frequency. However, some minor factors can also make the results unclear, such as the instantaneous change of the intermediate frequency switching signal level. Such observations can be made using a demodulator with good limiting performance and a signal generator, which is frequency modulated by a sinusoidal voltage to produce a suitable frequency deviation (such as the test audio deviation).
6.4 Method of Presentation of Results
The measurement results shall be presented using a photograph of the oscilloscope display. The time scale may be divided by a calibrated frequency scale or by measuring the number of cycles of the test signal (usually this signal is not displayed). 6.5 Details to be Specified
The following items shall be included as required in the equipment detail specification: a. Nominal impedance of the switch and pilot receiver (IF or baseband); b. Nominal level at each point Pi~Ps (which may be adjusted by the network Nr, N2, Ns) (Figures 4a and 4b); c. Switching period of switch S (see Figures 4a and 4b); d. Baseband switching (see Figures 4a and 5a), level and frequency of the sinusoidal test signal; e. IF switching (conversion time measurement at baseband - see Figure 5b), frequency of the test signal and frequency deviation at this frequency point; f. Simulation of switching conditions,
name. Required switching time and operating time. 7 Transient disturbances at the output of baseband switching equipment
7.1 General considerations
Transient disturbances (spike voltages) may occur at the output of baseband switching equipment during switching operations. These voltage spikes may impair the transmission quality. Therefore, the amplitude and duration need to be limited. 7.2 Measurement method
The voltage spike value can be measured by connecting an oscilloscope with sufficient bandwidth to one output of the switching equipment and then performing a switching operation.
The block diagram of Figure 5a can be used. However, the signal generator should be removed and all ports should be connected to matched loads. When a specific switching standard is used (for example, the noise suppression effect of the baseband output when the noise power of the working channel and the standby channel is greater than the noise detector startup level), the voltage spike should be measured under each switching condition. 7.3 Method of presentation of results
Oscilloscope waveform photos with appropriate voltage and time calibration are preferably used to present the measurement results. Alternatively, the measurement results may be given in the following manner:
“The voltage spike amplitude on each output terminal is ≤1V peak, and the duration of the voltage spike on each output terminal is within 50% of the peak amplitude <2 μs\.
7.4 Details to be specified
In the equipment detail specification, the following items shall be included as required: The peak amplitude of the permitted voltage spike.
(For example, for duration <2μus, the peak amplitude is 2V, for duration >2μs; for duration the pulse width is 0.7V and the width of the pulse is 50% of the peak point)
8 References
1.CCIR Recommendation 444-2 (Volume X): Preferred characteristics of multi-line switching arrangements for analogue radio-relay systems. 2.CCIR Recommendation 305 (Volume X): Backup arrangements for television and telephone radio-relay systems. 3.CCIR Report 137-4 (Volume X): Analogue Radio relay system multi-line switching arrangement. 8
GB/T4958.9—1988
4.CCIR Recommendation 401-2 (Volume X): Frequency and frequency deviation of continuous pilot in television and telephone FM radio relay system. 5.CCIR Recommendation 3993 (Volume X): Noise measurement using continuous uniform spectrum signal in frequency division multiplexing telephone radio relay system.
6.CCIR Recommendation 567 (Volume XI): Transmission performance of television circuits designed for international switching. Narration
1. External pilot generator
2. Test signal generator
3. Variable attenuator
4. Baseband mixing||t t||5. Baseband branch
Set up the chip
6. Pilot detector
7. Pilot alarm
8. Noise detector
9. Noise alarm
Figure 1a-Block diagram of the measurement pilot detector function: used for baseband switching (5.2.2 and 5.4.2) Note: The test signal generator connected by the dotted line is only used for the measurement port of 5.4.2
1. External pilot generator
2. Test signal generator
3. Variable attenuator
4. Baseband mixing
6. Intermediate frequency modulator
Situation division point flow
7. Intermediate frequency demodulator||tt ||8. Pilot detector
9. Pilot alarm
10. Noise detector
11. Noise alarm
Figure 1b--Block diagram of the pilot detector function for measurement: IF switching use (5.2.2 and 5.4.2) Note: 1. If a pilot band stop filter is installed at the input of the IF modulator, it should be short-circuited. 2. If the internal pilot generator is assembled in the IF modulator, it should be disabled. 3. The test signal generator connected by the dotted line is only used for the measurement of 5.4.2. 9
GB/T4958.9—1988
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1. External pilot generator
2. Test signal generator
3. Variable attenuator
4. Baseband mixing
5. IF modulator
6. Variable attenuator
7. IF amplifierbzxz.net
8. RF transmitter
9. Variable attenuator
10. RF receiver
11. IF amplifier
12. IF demodulator
13. Baseband branch
14. Pilot detector||tt ||15. Pilot alarm
16. Noise detector
17. Noise alarm
18. White noise receiver
Figure 2a-Block diagram of noise detector and pilot detector using noise receiver method: Baseband switching (5.3.3, 5.5.25.6.2 and 5.7.2) Note: 1. If the pilot band stop filter is installed at the modulator input or the system demodulator output, it should be short-circuited 2. If the built-in pilot generator is installed in the modulator, it should be disabled 3. The test signal generator connected by the dotted line is only used for the measurement specified in 5.5.2. a
1. External pilot generator
2. Test signal generator
3. Variable attenuator
4. Baseband mixer
5. IF modulator
6. Variable attenuator
7. IF amplifier
8. RF transmitter
9. Variable attenuator
10. RF receiver
11. IF amplifier
12. IF branch
13. IF demodulator
14. Pilot detector||tt ||15. Pilot alarm
16. Noise detector
17. Noise alarm
18. IF demodulator
19. White noise receiver
Figure 2b--Test block diagram for measuring the noise detector and pilot detector functions using a noise receiver, applicable to IF switching (5.3.3, 5.5.2, 5.6.2 and 5.7.2)10
GB/T4958.9—1988
Note: 1. If a pilot band stop filter is installed at the modulator and input, it should be short-circuited. 2. If an internal pilot generator is installed in the modulator, it should be disabled. 3. The test signal generator connected by the dotted line is only used for the measurement of 5.5.2. Return
1. White noise generator
2. External pilot generator
3. Variable attenuator
4. Baseband mixing
5. Baseband branching
6. Pilot detector
7. Pilot alarm
8. Noise detector
9. Noise alarm
10. White noise receiver
Figure 3a-Test block diagram of using white noise generator to measure noise detector function: used for baseband switching (5.3.3 and 5.7.2) Note: The external pilot generator connected by dotted line is only used for the measurement of 5.7.2. Return Return
1.1. White noise generator
2. External pilot generator
3. Variable attenuator
4. Baseband mixing
5. IF modulator
6. IF branch
7. IF demodulator
Our equal rate amplifier
8. Pilot detector
9. Pilot alarm
10. Noise detector
11. Noise alarm
12. IF demodulator
13. White noise receiver
Figure 3b - Test block diagram for measuring the noise detector function using a white noise generator: Used for IF switching (5.3.3 and 5.7.2) Note: The external pilot generator connected by the dotted line is only used for the measurement of 5.7.2. 11
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