This standard applies to analog systems and mainly discusses the measurement of diversity receiving equipment using two or more receivers at a radio relay station. For this purpose, we assume that the diversity equipment constitutes a switching and (or) synthesized diversity channel circuit. Although in addition to the diversity channel equipment itself, transmitters, receivers, modulators and demodulators may also be included in the measurement scope. In addition to diversity equipment measurements, dual-channel and hot standby equipment measurements that are not discussed in this series of standards GB 4958.9 "Measurement methods for equipment used in ground radio relay systems Part 2: Subsystem measurements Section 9 Standby channel switching equipment" are considered in this standard. The measurements involve switching characteristics and switching process characteristics, and should be equally applicable to standby channel switching equipment tests and diversity, dual-channel and hot standby equipment measurements, which can be found in this series of standards GB 4958.9. GB/T 4958.17-1992 Measurement methods for equipment used in terrestrial radio-relay systems Part 2: Subsystem measurements Section 6: Diversity, dual-path and hot standby equipment GB/T4958.17-1992 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
GB/T4958.17—1992
eqvIEC487-2-6:1984
Methods of measurement for equipment used in terrestrial radio-relay systemsPart 2:Measurements for sub-systemsSection 6:Diversity'twin-path and hotstand-by equipmentPromulgated on October 6, 1992
Implemented on May 1, 1993
Promulgated by the State Administration of Technical Supervision
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 6:Diversity'twin-path and hotstand-by equipment equipmentused in terrestrial radio-relay systems Part 2: Measurements for sub-systems Section 6: Diversity'twin-path and hotstand-by equipment
This standard is part of the GB/T4958.17-1992 series of standards for "Measurement methods for equipment used in terrestrial radio-relay systems"
This standard is equivalent to the international standard IEC487-2-6 (1984) "Measurement methods for equipment used in terrestrial radio-relay systems Part 2: Subsystem measurements Section 6: Diversity, twin-path and hotstand-by equipment". 1 Subject content and scope of application
This standard applies to analog systems and mainly discusses the measurement of diversity receiving equipment using two or more receivers in a radio relay station. For this purpose, we assume that the diversity equipment constitutes a switching and (or) synthesized diversity channel circuit. Although in addition to the diversity channel equipment itself, transmitters, receivers, modulators and demodulators may also be included in the measurement scope. In addition to diversity equipment measurements, dual-channel and hot standby equipment measurements that are not discussed in this series of standards GB4958.9 "Measurement methods for equipment used in ground radio-relay systems Part 2: Subsystem measurements Section 9 Standby channel switching equipment" are considered in this standard. The measurements should involve switching characteristics and switching process characteristics, and should be equally applicable to standby channel switching equipment tests and diversity, dual-channel and hot standby equipment measurements, which can be found in this series of standards GB4958.9. 2 Referenced standards
GB4958.9 Measurement methods for equipment used in terrestrial radio-relay systems Part 2: Subsystem measurements Section 9 Standby channel switching equipment
2 Measurement methods for equipment used in terrestrial radio-relay systems Part 1: Measurements common to subsystems and simulation systems GB6662
Section 3 Measurements in the intermediate frequency range
GB4958.12 Measurement methods for equipment used in terrestrial radio-relay systems Part 3: Measurements in simulation systems Section 4 Measurements on frequency division multiplexed transmission
GB/T4958.14 Measurement methods for equipment used in terrestrial radio-relay systems Part 1: Measurements common to subsystems and simulation radio-relay systems Section 2 Measurements in the radio frequency range. 3 Introduction
The main factors affecting the availability of a radio relay circuit are the propagation conditions and the reliability of the equipment itself. The former is discussed in Article 3.1, and the latter in Article 3.2.
3.1 Diversity System
GB/T4958.17—1992
Diversity reception is based on the fact that radio signals travel across different paths and (or) use different frequencies to reach the receiving location, with locally unrelated levels and phases. Appropriate switching or synthesis methods are used to reduce the impact of fading. Dual paths and (or) different frequencies are widely used in line-of-sight systems. The diversity channel feeds the same baseband signal at the same time, and the selection is completed at the terminal of the diversity part. Two signals with different signal-to-noise ratios can be obtained at the receiving terminal. An automatic switch is used to select the one with a better signal-to-noise ratio as the output between the two signals, or a synthesizer is used to synthesize the two output signals to improve the signal-to-noise ratio.
Common diversity system types are as follows:
Frequency diversity system: This diversity device uses different RF channels and a common antenna for transmission and reception. In the microwave frequency band, the frequency difference is greater than 1% or 2%, and the channel fading characteristics are generally unrelated. Frequency diversity is mainly used to reduce the impact of fading caused by multipath propagation. Space diversity and beam angle diversity system: If the field strength depends largely on radio wave reflection, the first step is to use a single transmitting antenna and multiple receiving antennas for space diversity. Therefore, the receiving antennas are placed one above the other. Radiated angle diversity can be applied to troposcatter reception, and the direction of each receiving antenna is slightly moved in different directions to achieve a diversity effect. It is not considered here. Route diversity system: The diversity route is a path with different terrains, and each path includes two or more radio relay segments. The radio wave propagation conditions are different on different routes, so it can play a diversity role. In order to reduce the impact of rain attenuation on the signal-to-noise ratio, this system is mainly used in the frequency band above 10GHz.
3.2 Dual-channel and hot standby systems
Unlike diversity systems, dual-channel and hot standby systems are systems that use switches to switch to standby equipment in order to reduce the impact of equipment failure rather than fading. However, in dual-channel systems, the frequency difference can be as low as 1%. In hot standby systems, the two channels use the same frequency. In the latter system, the switching is not only at the receiving terminal, but also at each transceiver on the radio relay circuit. 4 Switching diversity, dual-channel and hot standby equipment
4.1 General considerations
Figure 1a shows a simplified block diagram of a baseband switching device, which is used in the receiving part of a diversity system and a hot standby system. The switching is driven by a pilot detector and a noise detector or an AGC voltage. Figure 2a shows a simplified block diagram of an intermediate frequency switching device, which is used in the receiver part of a diversity system, a dual-channel system and a hot standby system. In the intermediate frequency switching device, in addition to the pilot and noise detectors, a fast-response intermediate frequency detector is also used. The branches in the figure are indicated by dotted lines and can be selected according to the situation. The noise detector can be replaced by the AGC detector of the RF receiver, and the AGC is used to drive the switch. The intermediate frequency switching device is always connected to the RF receiver. Figure 3a shows a simplified block diagram of the RF switching equipment, which is applied to the signaling part of the hot standby system. The switching is driven by the RF detector voltage. In all switching equipment, the detection voltage is fed to the logic circuit, where a switch drive signal is generated from the input voltage. All detectors are generally equipped with an alarm light indicating the change from normal to abnormal conditions, and the switching of the two states is usually indicated by a light. Note: In most two-channel switching equipment, in order to avoid unnecessary switching, the switch still maintains its last state even if the condition of the original faulty channel has been restored. The following measurement method is applicable to the "mutual standby" type system. The switch switches from one channel to another according to the pilot level, noise level or AGC level change. The block diagrams used for these level measurements are shown in Figures 1b, 2b and 3b, which include the switching equipment under test and additional pilot, IF and RF level attenuators to simulate propagation conditions or equipment failures. The required pilot, IF or RF levels are obtained by adjusting these attenuators. The noise level is measured using a white noise receiver connected to the output of the switching equipment (directly in the case of baseband equipment, or through a measurement demodulator in the case of IF equipment). If it is necessary to block the working pilot, a series pilot band stop filter can be used, and an external pilot generator can be used to provide a standard level pilot signal to both channels.
Note: ① All measurements should be supplemented with several special adjustments of the equipment control to provide adjustment of the switch switching level. ② In order to avoid instantaneous interruption of the signal, step attenuators shall not be used. 2
GB/T4958.17—1992
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Figure 1a Simplified block diagram of baseband switching equipment used in the receiving part of diversity system, dual-channel and hot standby system 1 demodulator; 2-RF receiver, 3-baseband branch; 4-pilot detector; 5-noise detector; 6-logic; 7 baseband switch 3
GB/T4958.17—1992
Base Simple Engineering
Figure 16: Functional measurement block diagram of baseband switching equipment used in the receiving part of diversity system, dual-channel and hot standby system 1—Attenuator; 2 Measurement modulator; 3—RF transmitter; 4—Receiver; 5—Demodulator; 6 Baseband switching equipment under test, 7 White noise receiver; 8—External pilot oscillator Di
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Guide quota governance||t t||Figure 2a Simplified block diagram of the intermediate frequency switching equipment used in the receiving part of the diversity, two-way system and hot standby system 1-RF receiver 2-IF branch, 3-IF detector; 4-demodulator; 5-pilot detector; 6-noise detector, 7-logic, intermediate frequency switch GB/T4958.17-1992
Guokouguo
Figure 26 Functional measurement block diagram of the intermediate frequency switching equipment used in the receiving part of the diversity, two-way system and hot standby system 1-Attenuator; 2 measurement modulator; 3-external pilot oscillator; 4-radio transmitter, 5-RF receiver; 6-intermediate frequency switching device under test: 7-measurement solution 1
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Figure 3a Simplified block diagram of the RF switching device of the transmitting part of the thermal equipment system 1-RF transmitter; 2-baseband or intermediate frequency branch; 3-coupler; 4-RF detector; 5-logic; 6-radio Frequency switch
GB/T4958.17—1992
Figure 3b Functional measurement block diagram of the RF switching equipment of the hot standby system transmission part 1—RF transmitter; 2—RF branch, 3—attenuator; 4—RF switching equipment under test
4.2 Switching caused by pilot level change As shown in Figure 1a and Figure 2a, the pilot change is detected by the pilot detector, and the two specified levels that can start and restore the switching need to be measured. The definition and method of these level measurements are described in this series of standards GB4958.9. The measurement of the pilot detector in each channel should be described separately. When these measurements are completed, the start and restore levels are verified and the switching can work correctly.
4.3 Switching caused by IF or RF level changes 4.3.1 Definition and general considerations
As shown in Figure 2a and Figure 3a, it is used for IF/RF in IF/RF switching equipment. Level changes are detected by the IF/RF detector, and two specified levels that enable switching to start and to recover need to be measured. The start level of an IF or RF detector is the IF/RF input signal level at which the detector operates and indicates the change from the "normal" state to the "abnormal" state. This level is usually adjustable to exceed a specified range. The recovery level refers to the IF/RF input signal level when the IF/RF detector changes from the "abnormal" state to the "normal" state. This level is specified as X (dB) above the start level. In some cases, X is adjustable. 4.3.2 Measurement method
In the IF/RF switching equipment, the block diagram of the IF/RF detector level measurement is shown in Figure 2b and Figure 3b. In the IF level measurement (Figure 2b) and the RF level measurement (Figure 3b), the nominal RF level is obtained at the receiver input (see Figure 2b) or the switching device input (see Figure 3b) by adjusting the attenuators RF1 and RF2. In the case of switching caused by changes in the IF level (see Figure 2b), attenuators IF1 and IF2 are first adjusted to zero attenuation, which is equivalent to sending the nominal IF level in the two channels to the switching device. These IF level test methods are described in this series of standards GB6662. In the case of switching caused by changes in the RF level, the level measurement method at the input end of the switching device is described in this series of standards GB/T4958.14. The IF and RF attenuators used above must be calibrated. The channel 1 detector level can be measured by increasing the positive 1 attenuation [switching for IF level changes (Figure 1b) or the RF1 attenuation [switching for RF level changes (Figure 3b) until the detector operates, and then reducing the attenuation until the detector indicates the normal position again. The measurement result is obtained by comparing the measured value of the relevant attenuator mentioned above with the initial value. The same steps are then repeated for the channel 2 detector. After completing these measurements, when the pickup and reset levels reached are verified, the switching can work correctly. NOTE: In many cases, the coupler and detector of the RF switching equipment shown in Figure 3a are included in the transmitter. In this case, it is necessary to include the transmitter as part of the device under test.
4.3.3 Representation of measurement results
The measured pickup and reset levels should be Tabulated. 4.3.4 Details to be specified
In the detailed equipment specification, the following items should be specified, if necessary: ​​a. Required start level range (for example -8 to -4 dB relative to the nominal level); b.
Required reset level range (for example 13 dB higher than the start level). 6
4.4 Switching due to noise level changes 4.4.1 General considerations
GB/T4958.17—1992
In the baseband/intermediate frequency switching equipment, a noise detector is used to detect noise level changes as shown in Figures 1a and 2a. The noise detector startup and reset levels in channel 1 and channel 2 and the noise level difference between channel 1 and channel 2 can be used as switching criteria. For the measurement method of the startup and reset levels For methods and definitions, see GB4958.9 of this series of standards. The description of the noise detector measurements of the two channels should be carried out separately. After completing these measurements, when the startup and recovery levels reached are verified, the switching can work correctly. When the noise levels of the two channels are different, the switching is initiated. The following method is used to measure the switching. 4.4.2 Measurement method
The measurement block diagram for initiating switching due to different noise levels between the two channels is shown in Figure 1b and Figure 2b. First, adjust the attenuators RF1 and RF2 so that the receiver obtains the nominal input level and records this value. Assuming that the switch position is in channel 1 at this time, then increase the attenuation of RF1 to increase the noise level in channel 1 until the switch turns to channel 2. The next step is to increase the attenuation of RF2 to increase the noise level in channel 2 until the switch is turned to channel 2. Switch back to channel 1. At the beginning and after each switch, the white noise receiver noise level reading should be recorded accordingly. Continue to increase the attenuation of RF1 and RF2 alternately until the highest noise level specified for diversity operation is reached. 4.4.3 Presentation of measurement results
The initial noise power value and the difference in noise power after each switch should be filled in the table in decibels. 4.4.4 Details to be specified
In the detailed equipment specification, the following items should be specified if necessary: ​​a.
The minimum noise power level difference range required to initiate a switch (e.g. 4 to 10 dB); b.
White noise receiver measurement frequency,
emphasis characteristics.
4.5 Switching due to AGC level changes 4.5.1 Measurement method
The AGC detector in the RF receiver in front of the IF diversity switching equipment detects the AGC level changes as shown in Figure 2a. If the AGC detector is used to control the IF diversity switching equipment, the difference in the RF input level between the two channels when the switching is started must be measured. The measurement block diagram is shown in Figure 2b.
First, adjust the attenuators RF1 and RF2 to obtain the nominal input level of the receiver and record this value. Assume that the switch position is channel 1 at this time, then increase the attenuation of RF1 to reduce the RF input level in channel 1 until the switch is turned to channel 2. Next, increase the attenuation of RF2 to reduce the RF input level in channel 2 until the switch is turned back to channel 1. Record the readings of the attenuator at the beginning and after each switch, and continue to increase the attenuation of RF1 and RF2 alternately until the minimum input level of the receiver specified for diversity startup is reached. 4.5.2 Representation of measurement results
The initial level value and the level value relative to the nominal input of the receiver after each conversion, as well as the difference between adjacent measurements, shall be tabulated in decibels.
4.5.3 Details to be specified
In the detailed equipment specification, the following items shall be specified if necessary: ​​a. The nominal input level of the receiver (e.g. -30 dBm); a.
The range of receiver input levels required to start diversity (e.g. +5 to -35 dB relative to the nominal level); c. The range of the minimum receiver input level difference required to start switching (e.g. 4 to 6 dB). 4.6 Isolation between switch ports
See GB4958.9 of this series of standards.
5 Synthetic diversity equipment
5.1 General considerations
GB/T4958.17—1992
For any diversity system connected to two microwave receivers, the synthesis is performed either at the intermediate frequency or at the baseband. In a space diversity system where the two signals are at the same radio frequency, the synthesis can be performed at the radio frequency. And the radio frequency synthesizer is followed by a single receiver. The synthesis equipment includes the synthesizer itself and several phase control circuits that provide the same phase signal to the intermediate frequency and radio frequency synthesizer input ports. Figure 4 shows a simplified block diagram of the synthesis equipment used in the diversity system. In the radio frequency synthesis equipment shown in Figure 4a, the control of the radio frequency phase is achieved by using a servo motor driving an radio frequency phase shifter and a phase modulator inserted in the radio frequency path and modulated by a low frequency oscillator. The amplitude modulation of the intermediate frequency output signal after synthesis depends on the phase difference between the two radio frequency signals. An intermediate frequency envelope detector is used to provide the phase control signal for the servo motor.
In the IF synthesis equipment shown in Figures 4b and 4c, an RF phase shifter is inserted between the local oscillator and one of the mixers or an IF phase shifter is inserted between one of the IF outputs and the phase detector input or a voltage-controlled local oscillator is used to control the IF phase.
This control is achieved by using the IF phase detector output to compare the synthesizer input signal. In the baseband synthesis equipment shown in Figure 4a, only the baseband synthesizer itself is generally used without phase control (but some phase equalization is required). Three types of synthesizers that can be used to improve the signal-to-noise ratio (sometimes also called diversity gain) are shown in Figure 5, and their functions are as follows: a. In equal signal level synthesizers, which are mainly used for baseband, the signals are synthesized at equal signal levels, so the improvement in signal-to-noise ratio provided is limited to the difference in signal-to-noise ratio. Therefore, when the difference in signal-to-noise ratio is greater than about 5dB, the channel with the lower signal-to-noise ratio is turned off. b. In the linear addition synthesizer mainly used for RF or IF equal gain synthesis, the signals are synthesized at their inherent level difference (i.e. the AGC circuit mentioned above). Therefore, a higher signal-to-noise ratio is provided than the equal signal level type, but further improvement can only be achieved within the range of the difference in signal-to-noise ratio, although within the signal-to-noise ratio difference greater than 7.66dB, the signal-to-noise ratio has a small loss. When the signal-to-noise ratio difference is greater than this value, the channel with a lower signal-to-noise ratio is not closed. The reason is the complexity of the switching equipment and the limit of the improvement that can be obtained; c. In the ratio square or maximum ratio synthesizer mainly used for IF or baseband, the signals are synthesized in proportion to their respective signal-to-noise ratios. This type of synthesizer improves the signal-to-noise ratio with any signal-to-noise ratio difference. Therefore, this synthesis method does not require switching channels. Note: For IF and baseband synthesizers, in order to invalidate useless channels, a pilot detector is usually used to start switching. This switching function is measured in accordance with Article 4.2. This switching takes place while the baseband signal output level must be maintained. For any diversity combining equipment, the most important characteristic to be measured is the effect of the signal-to-noise ratio of the other channel on the signal-to-noise ratio at the combiner output when the signal-to-noise ratio in the channel is kept constant. For RF/IF combining equipment, the effect of the RF input level and phase on the IF output level is measured, and the IF transient response to sudden changes in input phase should also be measured. Although the signal-to-noise ratio function is the most important characteristic of the combiner, it is also important to evaluate the effect of the combiner insertion on the transmission quality of the simulated circuit (see 5.5). In this connection, the transmission quality is evaluated under various operating conditions, such as each channel is in normal operation or one channel is disconnected from the combiner.
Core+output
Figure 4a Simplified block diagram of RF synthesizer
1-modulation oscillator; 2-bandpass filter; 3-RF phase modulator; 4-RF phase shifter; 5-servo motor 6-RF synthesizer; 7-RF receiver 8
GB/T4958.17—1992
China
China
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Figure 4b Common local oscillator of intermediate frequency synthesizer Simplified block diagram of an oscillator (spatial diversity) 1—local oscillator; 2—mixer, 3 RF branch, 4—IF amplifier; 5-RF phase shifter 6—IF phase shifter; 7-IF phase detector; 8 IF synthesizer
Figure 4c Simplified block diagram of an independent local oscillator of an IF synthesizer 1—mixer; 2—local oscillator; 3—IF amplifier; 4—IF phase detector, 5—IF synthesizer
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Figure 4d Simplified block diagram of baseband synthesizer
1 RF receiver; 2 Demodulator, 3 Baseband synthesizer 9
5.2 Signal-to-noise ratio function
5.2.1 Measurement method
GB/T4958.17—1992
Signal-to-noise ratio function of ideal diversity combiner
a ratio square or maximum ratio synthesizer, b equal gain or linear addition synthesizer; c equal signal level synthesizer
The measurement block diagram of the signal-to-noise ratio function of the diversity combiner is shown in Figure 6 (in the case where the RF transmitter is equipped with an intermediate frequency oscillator, the intermediate frequency generator is not required). The signal-to-noise ratio corresponding to the basic noise (i.e., no noise load) is measured using a white noise receiver. The signal-to-noise ratio is directly calibrated in decibels. As described in this series of standards GB4958.12. The synthesizer characteristics are evaluated by the following signal-to-noise ratio test: (s/N). —The signal-to-noise ratio when both inputs of a synthesizer are valid. (S/N)1 — The signal-to-noise ratio of channel 1 with channel 2 excluded. (S/N)2 — The signal-to-noise ratio of channel 2 with channel 1 excluded. In the case of IF or baseband synthesizers, a switch is usually required to exclude one of the channels. In the case of RF synthesizers, disconnect the RF ports and connect matched loads.
Adjust attenuators RF1 and RF2 so that the receiver input level is in the middle of the AGC range, where triangular noise is dominant. Record the initial ratio (S/N)o of this input level when (S/N)1 equals (S/N)2. First, increase the attenuation of RF1 to reduce (S/N)1, and test (S/N)1 for several RF1 values. Then reset RF1 to its original attenuation value. The next step is to increase the attenuation of RF2 to reduce (S/N)2, and test (S/N)2 for several RF2 values. Finally, reset RF2 to its original attenuation value. In the equal signal level synthesizer, the channel changes with the input level and automatically closes and restores during the above steps. The signal-to-noise ratio should be recorded when the channel is closed and restored.
Note: In addition to adjusting RF1 and RF2 in the above steps so that each receiver obtains the RF input level, under the conditions of (S/N). Approximate to (S/N)1 and (S/N)2, check RF1 and RF2. It should meet the condition that when RF1 or RF2 increases, (S/N)i or (S/N)2 decreases. 10
GB/T4958.17—1992
Figure 6a RF synthesis equipment signal-to-noise ratio function measurement block diagram 1—IF generator, 2—RF generator 3—attenuator; 4—RF branch; 5—RF synthesizer of the measured receiving device; 6—measurement demodulator; 7—white noise receiver REI
IF synthesis equipment signal-to-noise ratio function measurement block diagram Figure 6b
1 IF generator; 2—RF transmitter; 3—attenuator; 4—RF branch, 5—IF synthesizer of the measured receiving device; 6—measurement demodulator; 7—white noise receiver
Figure 6c Baseband synthesis equipment signal-to-noise ratio function measurement block diagram 1—IF generator 2—RF transmitter; 3—attenuator; 4—RF branch, 5—Baseband synthesizer of the measured receiving device; 6—white noise receiver 1117—1992
Figure 6a RF synthesis equipment signal-to-noise ratio function measurement block diagram 1—IF generator, 2—RF generator 3—attenuator; 4—RF branch; 5—RF synthesizer of the measured receiving device; 6—measurement demodulator; 7—white noise receiver REI
IF synthesis equipment signal-to-noise ratio function measurement block diagram Figure 6b
1 IF generator; 2—RF transmitter; 3—attenuator; 4—RF branch, 5—IF synthesizer of the measured receiving device; 6—measurement demodulator; 7—white noise receiver
Figure 6c Baseband synthesis equipment signal-to-noise ratio function measurement block diagram 1—IF generator 2—RF transmitter; 3—attenuator; 4—RF branch, 5—Baseband synthesizer of the measured receiving device; 6—white noise receiver 1117—1992
Figure 6a RF synthesis equipment signal-to-noise ratio function measurement block diagram 1—IF generator, 2—RF generator 3—attenuator; 4—RF branch; 5—RF synthesizer of the measured receiving device; 6—measurement demodulator; 7—white noise receiver REI
IF synthesis equipment signal-to-noise ratio function measurement block diagram Figure 6b
1 IF generator; 2—RF transmitter; 3—attenuator; 4—RF branch, 5—IF synthesizer of the measured receiving device; 6—measurement demodulator; 7—white noise receiver
Figure 6c Baseband synthesis equipment signal-to-noise ratio function measurement block diagram 1—IF generator 2—RF transmitter; 3—attenuator; 4—RF branch, 5—Baseband synthesizer of the measured receiving device; 6—white noise receiver 11Within the difference of 66dB in signal-to-noise ratio, there is a small loss in signal-to-noise ratio. When the difference in signal-to-noise ratio is greater than this value, the channel with lower signal-to-noise ratio is not closed. The reason is the complexity of the switching equipment and the limit of improvement that can be obtained; c. In the ratio squarer or maximum ratio synthesizer mainly used for intermediate frequency or baseband, the signals are synthesized in proportion to their respective signal-to-noise ratios. This synthesizer improves the signal-to-noise ratio with any signal-to-noise ratio difference. Therefore, this synthesis method does not require channel switching. Note: For intermediate frequency and baseband synthesizers, in order to invalidate useless channels, a pilot detector is usually used to start switching. This switching function is measured in accordance with Article 4.2. When this switching occurs, the baseband signal output level must be maintained. The most important characteristic to be measured for any synthesis diversity equipment is the effect of the signal-to-noise ratio of another channel on the signal-to-noise ratio at the output of the synthesizer when the signal-to-noise ratio in the channel remains constant. For RF/IF synthesis equipment, the effect of RF input level and phase on IF output level should be measured, and the IF transient response when the input phase changes suddenly should also be measured. Although the signal-to-noise ratio function is the most important characteristic of the synthesizer, it is also important to evaluate the influence of the synthesizer insertion on the transmission quality of the simulated circuit (see 5.5). In this connection, the evaluation of the transmission quality is carried out under various operating conditions, such as normal operation of each channel or a channel disconnected from the synthesizer.
Core+Output
Figure 4a Simplified block diagram of RF synthesizer
1-Modulation oscillator; 2-Bandpass filter; 3-RF phase modulator; 4-RF phase shifter; 5-Servo motor 6-RF synthesizer; 7-RF receiver 8
GB/T4958.17-1992bzxz.net
China ... Simplified block diagram of an oscillator (spatial diversity) 1—local oscillator; 2—mixer, 3 RF branch, 4—IF amplifier; 5-RF phase shifter 6—IF phase shifter; 7-IF phase detector; 8 IF synthesizer
Figure 4c Simplified block diagram of an independent local oscillator of an IF synthesizer 1—mixer; 2—local oscillator; 3—IF amplifier; 4—IF phase detector, 5—IF synthesizer
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Figure 4d Simplified block diagram of baseband synthesizer
1 RF receiver; 2 Demodulator, 3 Baseband synthesizer 9
5.2 Signal-to-noise ratio function
5.2.1 Measurement method
GB/T4958.17—1992
Signal-to-noise ratio function of ideal diversity combiner
a ratio square or maximum ratio synthesizer, b equal gain or linear addition synthesizer; c equal signal level synthesizer
The measurement block diagram of the signal-to-noise ratio function of the diversity combiner is shown in Figure 6 (in the case where the RF transmitter is equipped with an intermediate frequency oscillator, the intermediate frequency generator is not required). The signal-to-noise ratio corresponding to the basic noise (i.e., no noise load) is measured using a white noise receiver. The signal-to-noise ratio is directly calibrated in decibels. As described in this series of standards GB4958.12. The synthesizer characteristics are evaluated by the following signal-to-noise ratio test: (s/N). —The signal-to-noise ratio when both inputs of a synthesizer are valid. (S/N)1 — The signal-to-noise ratio of channel 1 with channel 2 excluded. (S/N)2 — The signal-to-noise ratio of channel 2 with channel 1 excluded. In the case of IF or baseband synthesizers, a switch is usually required to exclude one of the channels. In the case of RF synthesizers, disconnect the RF ports and connect matched loads.
Adjust attenuators RF1 and RF2 so that the receiver input level is in the middle of the AGC range, where triangular noise is dominant. Record the initial ratio (S/N)o of this input level when (S/N)1 equals (S/N)2. First, increase the attenuation of RF1 to reduce (S/N)1, and test (S/N)1 for several RF1 values. Then reset RF1 to its original attenuation value. The next step is to increase the attenuation of RF2 to reduce (S/N)2, and test (S/N)2 for several RF2 values. Finally, reset RF2 to its original attenuation value. In the equal signal level synthesizer, the channel changes with the input level and automatically closes and restores during the above steps. The signal-to-noise ratio should be recorded when the channel is closed and restored.
Note: In addition to adjusting RF1 and RF2 in the above steps so that each receiver obtains the RF input level, under the conditions of (S/N). Approximate to (S/N)1 and (S/N)2, check RF1 and RF2. It should meet the condition that when RF1 or RF2 increases, (S/N)i or (S/N)2 decreases. 10
GB/T4958.17—1992
Figure 6a RF synthesis equipment signal-to-noise ratio function measurement block diagram 1—IF generator, 2—RF generator 3—attenuator; 4—RF branch; 5—RF synthesizer of the measured receiving device; 6—measurement demodulator; 7—white noise receiver REI
IF synthesis equipment signal-to-noise ratio function measurement block diagram Figure 6b
1 IF generator; 2—RF transmitter; 3—attenuator; 4—RF branch, 5—IF synthesizer of the measured receiving device; 6—measurement demodulator; 7—white noise receiver
Figure 6c Baseband synthesis equipment signal-to-noise ratio function measurement block diagram 1—IF generator 2—RF transmitter; 3—attenuator; 4—RF branch, 5—Baseband synthesizer of the measured receiving device; 6—white noise receiver 11Within the difference of 66dB in signal-to-noise ratio, there is a small loss in signal-to-noise ratio. When the difference in signal-to-noise ratio is greater than this value, the channel with lower signal-to-noise ratio is not closed. The reason is the complexity of the switching equipment and the limit of improvement that can be obtained; c. In the ratio squarer or maximum ratio synthesizer mainly used for intermediate frequency or baseband, the signals are synthesized in proportion to their respective signal-to-noise ratios. This synthesizer improves the signal-to-noise ratio with any signal-to-noise ratio difference. Therefore, this synthesis method does not require channel switching. Note: For intermediate frequency and baseband synthesizers, in order to invalidate useless channels, a pilot detector is usually used to start switching. This switching function is measured in accordance with Article 4.2. When this switching occurs, the baseband signal output level must be maintained. The most important characteristic to be measured for any synthesis diversity equipment is the effect of the signal-to-noise ratio of another channel on the signal-to-noise ratio at the output of the synthesizer when the signal-to-noise ratio in the channel remains constant. For RF/IF synthesis equipment, the effect of RF input level and phase on IF output level should be measured, and the IF transient response when the input phase changes suddenly should also be measured. Although the signal-to-noise ratio function is the most important characteristic of the synthesizer, it is also important to evaluate the influence of the synthesizer insertion on the transmission quality of the simulated circuit (see 5.5). In this connection, the evaluation of the transmission quality is carried out under various operating conditions, such as normal operation of each channel or a channel disconnected from the synthesizer.
Core+Output
Figure 4a Simplified block diagram of RF synthesizer
1-Modulation oscillator; 2-Bandpass filter; 3-RF phase modulator; 4-RF phase shifter; 5-Servo motor 6-RF synthesizer; 7-RF receiver 8
GB/T4958.17-1992
China ... Simplified block diagram of an oscillator (spatial diversity) 1—local oscillator; 2—mixer, 3 RF branch, 4—IF amplifier; 5-RF phase shifter 6—IF phase shifter; 7-IF phase detector; 8 IF synthesizer
Figure 4c Simplified block diagram of an independent local oscillator of an IF synthesizer 1—mixer; 2—local oscillator; 3—IF amplifier; 4—IF phase detector, 5—IF synthesizer
Heart aim out
0 hold!
Figure 4d Simplified block diagram of baseband synthesizer
1 RF receiver; 2 Demodulator, 3 Baseband synthesizer 9
5.2 Signal-to-noise ratio function
5.2.1 Measurement method
GB/T4958.17—1992
Signal-to-noise ratio function of ideal diversity combiner
a ratio square or maximum ratio synthesizer, b equal gain or linear addition synthesizer; c equal signal level synthesizer
The measurement block diagram of the signal-to-noise ratio function of the diversity combiner is shown in Figure 6 (in the case where the RF transmitter is equipped with an intermediate frequency oscillator, the intermediate frequency generator is not required). The signal-to-noise ratio corresponding to the basic noise (i.e., no noise load) is measured using a white noise receiver. The signal-to-noise ratio is directly calibrated in decibels. As described in this series of standards GB4958.12. The synthesizer characteristics are evaluated by the following signal-to-noise ratio test: (s/N). —The signal-to-noise ratio when both inputs of a synthesizer are valid. (S/N)1 — The signal-to-noise ratio of channel 1 with channel 2 excluded. (S/N)2 — The signal-to-noise ratio of channel 2 with channel 1 excluded. In the case of IF or baseband synthesizers, a switch is usually required to exclude one of the channels. In the case of RF synthesizers, disconnect the RF ports and connect matched loads.
Adjust attenuators RF1 and RF2 so that the receiver input level is in the middle of the AGC range, where triangular noise is dominant. Record the initial ratio (S/N)o of this input level when (S/N)1 equals (S/N)2. First, increase the attenuation of RF1 to reduce (S/N)1, and test (S/N)1 for several RF1 values. Then reset RF1 to its original attenuation value. The next step is to increase the attenuation of RF2 to reduce (S/N)2, and test (S/N)2 for several RF2 values. Finally, reset RF2 to its original attenuation value. In the equal signal level synthesizer, the channel changes with the input level and automatically closes and restores during the above steps. The signal-to-noise ratio should be recorded when the channel is closed and restored.
Note: In addition to adjusting RF1 and RF2 in the above steps so that each receiver obtains the RF input level, under the conditions of (S/N). Approximate to (S/N)1 and (S/N)2, check RF1 and RF2. It should meet the condition that when RF1 or RF2 increases, (S/N)i or (S/N)2 decreases. 10
GB/T4958.17—1992
Figure 6a RF synthesis equipment signal-to-noise ratio function measurement block diagram 1—IF generator, 2—RF generator 3—attenuator; 4—RF branch; 5—RF synthesizer of the measured receiving device; 6—measurement demodulator; 7—white noise receiver REI
IF synthesis equipment signal-to-noise ratio function measurement block diagram Figure 6b
1 IF generator; 2—RF transmitter; 3—attenuator; 4—RF branch, 5—IF synthesizer of the measured receiving device; 6—measurement demodulator; 7—white noise receiver
Figure 6c Baseband synthesis equipment signal-to-noise ratio function measurement block diagram 1—IF generator 2—RF transmitter; 3—attenuator; 4—RF branch, 5—Baseband synthesizer of the measured receiving device; 6—white noise receiver 11Signal-to-noise ratio of channel 1. (S/N)2 - Signal-to-noise ratio of channel 2 with channel 1 excluded. In the case of IF or baseband synthesizers, a switch is usually required to exclude one of the channels. In the case of RF synthesizers, disconnect the RF ports and connect matched loads.
Adjust attenuators RF1 and RF2 so that the receiver input level is in the middle of the AGC range, where triangular noise is dominant. Record the initial ratio (S/N)o of this input level when (S/N)1 equals (S/N)2. First, increase the attenuation of RF1 to reduce (S/N)1, and test (S/N)1 for several RF1 values. Then reset RF1 to its original attenuation value. The next step is to increase the attenuation of RF2 to reduce (S/N)2, and test (S/N)2 for several RF2 values. Finally, reset RF2 to its original attenuation value. In the equal signal level synthesizer, the channel changes with the input level and automatically closes and restores during the above steps. The signal-to-noise ratio should be recorded when the channel is closed and restored.
Note: In addition to adjusting RF1 and RF2 in the above steps so that each receiver obtains the RF input level, under the conditions of (S/N). Approximate to (S/N)1 and (S/N)2, check RF1 and RF2. It should meet the condition that when RF1 or RF2 increases, (S/N)i or (S/N)2 decreases. 10
GB/T4958.17—1992
Figure 6a RF synthesis equipment signal-to-noise ratio function measurement block diagram 1—IF generator, 2—RF generator 3—attenuator; 4—RF branch; 5—RF synthesizer of the measured receiving device; 6—measurement demodulator; 7—white noise receiver REI
IF synthesis equipment signal-to-noise ratio function measurement block diagram Figure 6b
1 IF generator; 2—RF transmitter; 3—attenuator; 4—RF branch, 5—IF synthesizer of the measured receiving device; 6—measurement demodulator; 7—white noise receiver
Figure 6c Baseband synthesis equipment signal-to-noise ratio function measurement block diagram 1—IF generator 2—RF transmitter; 3—attenuator; 4—RF branch, 5—Baseband synthesizer of the measured receiving device; 6—white noise receiver 11Signal-to-noise ratio of channel 1. (S/N)2 - Signal-to-noise ratio of channel 2 with channel 1 excluded. In the case of IF or baseband synthesizers, a switch is usually required to exclude one of the channels. In the case of RF synthesizers, disconnect the RF ports and connect matched loads.
Adjust attenuators RF1 and RF2 so that the receiver input level is in the middle of the AGC range, where triangular noise is dominant. Record the initial ratio (S/N)o of this input level when (S/N)1 equals (S/N)2. First, increase the attenuation of RF1 to reduce (S/N)1, and test (S/N)1 for several RF1 values. Then reset RF1 to its original attenuation value. The next step is to increase the attenuation of RF2 to reduce (S/N)2, and test (S/N)2 for several RF2 values. Finally, reset RF2 to its original attenuation value. In the equal signal level synthesizer, the channel changes with the input level and automatically closes and restores during the above steps. The signal-to-noise ratio should be recorded when the channel is closed and restored.
Note: In addition to adjusting RF1 and RF2 in the above steps so that each receiver obtains the RF input level, under the conditions of (S/N). Approximate to (S/N)1 and (S/N)2, check RF1 and RF2. It should meet the condition that when RF1 or RF2 increases, (S/N)i or (S/N)2 decreases. 10
GB/T4958.17—1992
Figure 6a RF synthesis equipment signal-to-noise ratio function measurement block diagram 1—IF generator, 2—RF generator 3—attenuator; 4—RF branch; 5—RF synthesizer of the measured receiving device; 6—measurement demodulator; 7—white noise receiver REI
IF synthesis equipment signal-to-noise ratio function measurement block diagram Figure 6b
1 IF generator; 2—RF transmitter; 3—attenuator; 4—RF branch, 5—IF synthesizer of the measured receiving device; 6—measurement demodulator; 7—white noise receiver
Figure 6c Baseband synthesis equipment signal-to-noise ratio function measurement block diagram 1—IF generator 2—RF transmitter; 3—attenuator; 4—RF branch, 5—Baseband synthesizer of the measured receiving device; 6—white noise receiver 11
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