CN107612642A - A kind of signal band and out-of-band interference level method of testing - Google Patents

Abstract

The invention relates to a signal frequency band and a method for testing interference levels outside the frequency band, comprising: a computer terminal starts a carrier communication test item, and sends a carrier communication command to a concentrator or a reader through a communication interface; Data, to judge whether the carrier communication is successful or not; at the same time, the test system is notified through the communication interface, and the industrial computer starts the test process control program of the project; when the spectrum analyzer inside the test system finishes testing the carrier transmission level parameters, the industrial computer sends a stop test command ; Adjust the working state of the test system according to the carrier communication result, read the test data stored in the industrial computer from the communication interface and complete the processing. The present invention is carried out according to the given method of DL/T 698. The sampling signal is passed through circuits such as isolation level conversion, and then sent to the spectrum analyzer for measurement according to the sampling of the sending end and the receiving end, and the actual carrier level is obtained, which realizes high test stability and anti-interference The advantages of strong ability.

Description

A kind of interference level testing method of signal frequency band and out-of-band

technical field

The invention relates to the technical field of testing the signal frequency band, the maximum output signal level and the interference level outside the frequency band, in particular to a method for testing the signal frequency band and the interference level outside the frequency band.

Background technique

With the improvement of the degree of automation of the power system, and the increasingly widespread application of computer technology in the power system. Due to its disadvantages such as low efficiency, large investment, and poor reliability, the traditional electricity billing method has been unable to adapt to the requirements of the new situation. It is of practical significance to establish a high-precision, stable, reliable, and highly automated electric energy automatic metering system.

The metering automation terminal equipment communicates with the energy meter through the local communication network. Within the framework of the electricity consumption information collection system, the local communication network is mainly composed of low-voltage power line carrier, RS-485 and micro-power wireless communication. Compared with other communication methods, the low-voltage power line carrier, which is convenient for construction and low in cost, is favored by power companies. However, with the construction of the centralized meter reading system and the development of pilot work, related problems gradually emerged. The communication channel used by the power carrier communication has certain inherent defects. Since the original design of the low-voltage power line is to ensure the power transmission of the distribution line, it is not a communication carrier specially used to transmit high-frequency signals, so there is noise on the low-voltage power line. Large interference, fast attenuation changes, line impedance changes with topology changes and load access, and uncertain factors such as line length and connection nodes also affect the communication rate and reliability of low-voltage power line carriers. It is urgent to develop a A signal frequency band and a method for testing the interference level outside the frequency band.

Contents of the invention

The purpose of the present invention is to provide a method for testing the interference level of the signal frequency band and outside the frequency band, which ensures the comparability of the level test results and realizes high test stability and strong anti-interference ability.

In order to achieve the above object, the present invention adopts the following technical solutions: a signal frequency band and an interference level testing method outside the frequency band, the method comprising the steps of the following sequence:

(1) The computer terminal starts the carrier communication test item, that is, the maximum output signal level and the out-of-band interference level test program, and sends a carrier communication command to the tested concentrator or reader through the communication interface;

(2) Receive the data of the measured carrier table, and judge whether the carrier communication is successful or not;

(3) At the same time, the test system is notified through the communication interface, and the industrial computer starts the test process control program of the project;

(4) After the spectrum analyzer inside the test system completes the test carrier transmission level parameters, the industrial computer sends a stop test command;

(5) Adjust the working state of the test system according to the carrier communication results, read the test data stored in the industrial computer from the communication interface and complete the processing.

When the computer terminal starts the carrier communication test project, a clean power supply system is added to the test system, and the clean power supply system provides an ideal low-voltage power line simulation test environment for the communication interface.

Receive the data of the measured carrier meter through the single-phase carrier energy meter or three-phase carrier energy meter to judge whether the carrier communication is successful or not.

When the industrial computer starts the test process control program of the project, a digital oscilloscope is used to monitor the test process and reflect the actual timing of the carrier communication in the time domain.

In step (5), when performing data processing, the signal frequency band test is carried out according to the DL/T 698 standard. First, use a spectrum analyzer to test the maximum signal level, and then perform amplitude analysis on the current spectrum to obtain an off-center value 20dB smaller than the maximum signal A pair of frequency points of the frequency, subtract the frequency of the pair of frequency points, take the absolute value, and obtain the current carrier signal frequency band.

As can be seen from the above-mentioned technical solution, the advantages of the present invention are: first, the present invention is carried out according to the given method of DL/T 698, and the key of this project is the measurement of signal level, to ensure that the results of the level test are comparable; the second Second, there must be an appropriate test environment. The artificial power network can take on this role, and use the stable impedance characteristics of the artificial power network to achieve the goal of test consistency. Borrow the design ideas of GB/T6113.103-2008 on the artificial power network to carry out carrier Signal sampling; thirdly, the sampling signal is sent to the program-controlled switch through isolation level conversion and other circuits, as a test port, and the computer selects different test ports to represent different signal sampling, and then sends the spectrum analyzer for measurement according to the sampling of the sending end and the receiving end , to obtain the actual carrier level, and realize the advantages of high test stability and strong anti-interference ability.

Description of drawings

Fig. 1 is a flow chart of the method of the present invention.

detailed description

As shown in Figure 1, a kind of signal frequency band and the interference level test method outside the frequency band, this method comprises the steps of following sequence:

(1) The computer terminal starts the carrier communication test item, that is, the maximum output signal level and the out-of-band interference level test program, and sends a carrier communication command to the tested concentrator or reader through the communication interface;

(2) Receive the data of the measured carrier meter, and the staff judge whether the carrier communication is successful or not through the data of the carrier meter;

(3) At the same time, notify the test system industrial computer to start the test flow control program of the project through the communication interface; the test system is composed of a spectrum analyzer and a digital oscilloscope;

(4) After the spectrum analyzer inside the test system completes the test carrier transmission level parameters, the industrial computer sends a stop test command;

(5) Adjust the working state of the test system according to the carrier communication results, read the test data stored in the industrial computer from the communication interface and complete the processing.

When the computer terminal starts the carrier communication test project, a clean power supply system is added to the test system, and the clean power supply system provides an ideal low-voltage power line simulation test environment for the communication interface.

Receive the data of the measured carrier meter through the single-phase carrier energy meter or three-phase carrier energy meter to judge whether the carrier communication is successful or not.

When the industrial computer starts the test process control program of the project, a digital oscilloscope is used to monitor the test process and reflect the actual timing of the carrier communication in the time domain.

In step (5), when performing data processing, the signal frequency band test is carried out according to the DL/T 698 standard. First, use a spectrum analyzer to test the maximum signal level, and then perform amplitude analysis on the current spectrum to obtain an off-center value 20dB smaller than the maximum signal A pair of frequency points of the frequency, subtract the frequency of the pair of frequency points, take the absolute value, and obtain the current carrier signal frequency band.

The present invention uses the idea of signal level testing to test the out-of-band level similarly. Although 698 stipulates the test method for the signal frequency band, the corresponding point of the signal frequency band cannot be used as a criterion for the out-of-band level, because the maximum After subtracting 20dB, the amplitude of the signal level is far greater than the specified level value outside the frequency band. Therefore, the test frequency points of the interference level outside the frequency band cannot be transferred to the test results of the signal frequency band. According to the division of the communication frequency band, it is usually divided into It is the signal passband, the adjacent channel channel, the separated channel passband, etc. However, according to the actual results of the carrier spectrum, it is difficult to confirm this indicator. At present, the main assessment is whether the harmonic level of the carrier signal meets the requirements of the signal outside the frequency band. Level requirements, the interference level indicators outside the frequency band specified in 698 are as follows:

(1) The maximum interference level in the frequency band from 9kHz to 150kHz is not greater than 60dBμV;

(2) The maximum interference level in the frequency band from 150kHz to 500kHz is not greater than 50dBμV;

(3) The maximum interference level greater than 500kHz frequency band is not greater than 46dBμV.

If the out-of-band interference level meets the out-of-band interference level index specified in DL/T 698, the criterion is qualified; otherwise, the criterion is not qualified.

In summary, the present invention is carried out according to the given method of DL/T 698. The key of this project is the measurement of the signal level, to ensure that the results of the level test are comparable; the sampling signal is sent to the The program-controlled switch is used as a test port. The computer selects different test ports to represent the sampling of different signals. The samples from the sending end and the receiving end are sent to the spectrum analyzer for measurement, and the actual carrier level is obtained, which realizes high test stability and strong anti-interference ability. The advantages.

Claims (5)

1. a kind of signal frequency band and the interference level test method outside the frequency band, it is characterized in that: the method comprises the steps of following sequence: (1) The computer terminal starts the carrier communication test item, that is, the maximum output signal level and the out-of-band interference level test program, and sends a carrier communication command to the tested concentrator or reader through the communication interface; (2) Receive the data of the measured carrier table, and judge whether the carrier communication is successful or not; (3) At the same time, the test system is notified through the communication interface, and the industrial computer starts the test flow control program of the project, (4) After the spectrum analyzer inside the test system completes the test carrier transmission level parameters, the industrial computer sends a stop test command; (5) Adjust the working state of the test system according to the carrier communication results, read the test data stored in the industrial computer from the communication interface and complete the processing. 2. signal frequency band according to claim 1 and the interference level test method outside the frequency band, it is characterized in that: when computer terminal starts carrier communication test item, add clean power supply system in the test system, clean power supply system provides communication interface ideal low voltage Powerline simulation test environment. 3. signal frequency band according to claim 1 and the interference level test method outside the frequency band, it is characterized in that: receive the data of measured carrier meter by single-phase carrier energy meter or three-phase carrier energy meter, judge carrier communication success and no. 4. signal frequency band according to claim 1 and the interference level test method outside the frequency band, it is characterized in that: when industrial computer starts this project test flow control program, adopts digital oscilloscope to monitor test process, reflects carrier wave in time domain The actual timing of the communication. 5. signal frequency band according to claim 1 and the interference level testing method outside the frequency band, it is characterized in that: in step (5), when carrying out data processing, signal frequency band test is carried out according to DL/T 698 standard, uses first The spectrum analyzer tests the maximum signal level, and then performs amplitude analysis on the current spectrum to obtain a pair of frequency points that are 20dB smaller than the maximum signal and deviate from the center frequency. Subtract the frequencies of the pair of frequency points and take the absolute value to obtain the current carrier signal frequency band.