This standard specifies the linear and nonlinear measurement methods for radio frequency branch networks related to radio relay transmitters and receivers. This standard applies to the measurement of multi-port linear passive branch networks. GB/T 4958.16-1992 Measurement methods for equipment used in terrestrial radio relay systems Part 2: Measurement of subsystems Section 3: Radio frequency branch networks GB/T4958.16-1992 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
GB/T4958.16—1992
eqvIEC487-2-3:1984
Methods of measurement for equipment used in terrestrial radio-relay systems
Part 2: Measurements for sub-systems
Section 3: RF branching networks
Methods of measurement for equipment used in terrestrial radio-relay systemsPart 2:Measurements for sub-systemsSection 3:RF branching networksPublished on October 6, 1992
Implemented on May 1, 1993
Published 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 systems
Part 2: Measurements for sub-systems
Section 3:RF branching networks
Methods of measurement for equipment used in terrestrial Radio-relay systems Part 2: Measurements for sub-systems Section 3: RF branching networks This standard is part of the series of standards GB/T4958.16-1992 for "Measurement methods for equipment used in terrestrial radio-relay systems". This standard is equivalent to the international standard IEC487-2-3 (1984) "Measurement methods for equipment used in terrestrial radio-relay systems Part 2: Measurements for sub-systems Section 3: RF branching networks". 1 Subject content and scope of application This standard specifies the linear and nonlinear measurement methods for RF branching networks related to radio-relay transmitters and receivers. This standard is applicable to the measurement of multi-port linear passive branching networks. 2 Referenced standards GB/T4958.14 Measurement methods for equipment used in terrestrial radio-relay systems Part: Measurements common to sub-systems and simulated radio-relay systems Section 2: Measurements of RF range 3 Definitions and general considerations The branching networks involved in this standard are multi-port linear passive networks. A branch network is a device that connects the RF ports of several transmitters and receivers to a common RF feed. There are the following types of branch networks:
-receive only; www.bzxz.net
-transmit only;
-receive and transmit combined.
In a radio relay system with several RF channels, a branch network is used to connect transmitters and receivers working on different frequencies. The block diagram of a branch network with four transmitting ports (T1, *..*T), four receiving ports (R,., R and a common port C connected to the feed source is shown in Figure 1. The paths between T. and C, and between R. and C have passband and stopband characteristics. Due to the use of non-reciprocal elements, these paths are generally unidirectional. The paths of any other ports are isolated from each other. Therefore, passband, stopband and isolation loss are the characteristics that need to be determined for the branch network. When using an RF switch, it can be regarded as part of the branch network. The function of the switch is to connect a single device to one of the two feeders to change the channel, or to connect a single feeder to one of the two transmitters or receivers to replace the device. Approved by the State Administration of Technical Supervision on October 6, 1992 and implemented on May 1, 1993 || t t||GB/T4958.16—1992
The measurement of the branch network is carried out at the two specified ports. It is very important that not only the two ports to be measured, but also all other ports are correctly connected. Usually, it is necessary to connect a load with specified return loss and good matching to each port. If the network contains an RF switch, all measurements are performed at each specified position through the switch. Special attention should be paid: overload power must not be used to avoid damage to the dummy load, microwave switch tube and ferrite components in the measuring device. When the network is close to ferromagnetic materials, care must be taken to ensure that the electrical properties of the ferrite components in the network remain unchanged. In some cases, the filter of the branch network is an integral part of the transceiver, so it is not easy to measure. In this case, a filter of exactly the same type can be used instead. The measuring device is shown in Figures 1 to 3. The transmission loss from each port to the common port should be measured separately for whether there is a corresponding filter in the line. Only in this way can the basic loss of the branch network be determined.
From the transmitter
To the transmitter
Figure 1 Block diagram of the RF branch network
Radio branch circuit
Figure 2 Block diagram of multi-carrier intermodulation component measurement (transmitting direction) 2
4 Linear measurement
4.1 Parameters to be measured
GB/T4958.16—1992
High precision
Figure 3 Block diagram of multi-carrier intermodulation component measurement (receiving direction) Teaching
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The measured parameters depend on the selected port pair. Between ports T. and C and between C and R. (see Figure 1 ) The following measurements can be made: Transmission loss at the center frequency of the passband;
- Amplitude/frequency characteristics within the specified passband and stopband; - Group delay/frequency characteristics within the passband, reflection loss/frequency characteristics within the passband. Usually, the isolation loss between the remaining port pairs is measured at the center frequency of the passband. However, with the consent of the parties concerned, some representative ports can also be selected for measurement in order to reduce the number of measurements to a minimum. 4.2 Definitions, measurement methods, and representation of measurement results For the definitions, measurement methods, and representation of measurement results of the parameters listed in Article 4.1, please refer to GB/T4958.14. 4.3 Details to be specified
In the detailed equipment specification, if necessary, the following items should be included: a. Port pairs to be measured
b. Frequency or frequency range;
c. Characteristics to be measured.
5 Nonlinearity Measurement - Measurement of Multi-Carrier Intermodulation Components 5.1 General Consideration
Nonlinearity of branching networks produces multi-carrier intermodulation components at the following frequencies: f1 ± f2 ± f3
2f2f1 and so on.
This is the result of intermodulation between signals at frequencies f1, f2 and/or f3. 3
GB/T4958.16—1992
Multi-carrier intermodulation components can be caused by ferrite devices in the network, such as circulators, or by nonlinearities in the waveguide, such as imperfect flange connections.
5.2 Measurement Method
5.2.1 Measurement in the Transmit Direction
Single frequency signals of f1, f2, and f3 are applied to each of the two or three transmitter ports shown in Figure 2 at a specified level, such as +30 dBm (the figure only shows the case of two frequencies). Each frequency should be selected to be within the passband of the port used. In order to display the maximum permissible level of multi-carrier intermodulation products, a calibrated spectrum analyzer with sufficient sensitivity is connected to the common port (C) through a device that is terminated with a matched load and attenuates the carrier level to the dynamic range of the spectrum analyzer used. The device can be an attenuator or a directional coupler with an adjustable filter. It should be noted that the device used does not produce significant intermodulation. The remaining ports should be connected to matched loads with a specified return loss. The bandwidth of the spectrum analyzer should be narrow enough to suppress noise, and a suitably narrow sweep width should be selected. The level of the intermodulation products is read from the calibrated analyzer.
In some cases, it may be necessary to use an actual radio relay transmitter as a signal source for measurement. 5.2.2 Measurement in the receiving direction
At a specified level, for example -30dBm, single-frequency signals of f1, f2f3 are added to the common port (C) shown in Figure 3 (here only the case of two frequencies is shown). Each frequency should be selected to be within the passband of one of the receiving ports. A passband port suitable for measuring the required intermodulation components should be selected.
In order to display the maximum allowable level of multi-carrier intermodulation components, connect a calibrated spectrum analyzer with sufficiently high sensitivity to the specified receiving port. Its passband should include one of the appropriate frequencies of 2f1-f2, 2f2-f1 (or f1-f2±f3). The remaining ports should be connected to a matched load with a specified return loss. The bandwidth of the spectrum analyzer should be narrow enough to suppress noise, and an appropriately narrow sweep width should be selected. The level of the intermodulation components is read from the calibrated analyzer.
5.3. Expression of measurement results
The results shall be expressed in terms of the order, frequency and level of each intermodulation component. 5.4. Details to be specified
In the detailed equipment specification, the following items shall be included, if necessary: ​​a. The frequency and level of the signals f1, f2, fs b. The maximum permissible level of any intermodulation component, c. The return loss of the selected load within the measurement frequency range. Additional notes:
This standard was proposed by the Ministry of Posts and Telecommunications of the People's Republic of China. This standard is under the jurisdiction of the Telecommunications Transmission Institute of the Ministry of Posts and Telecommunications. This standard was drafted by the Beijing Communications Equipment Factory of the Ministry of Posts and Telecommunications. The main drafters of this standard are Chen Chengda, Ma Yihai and Ji Shudong. 4
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