RU2761478C1 - Method for automated measurement of the levels of electromagnetic radiation in the structural elements of a shielded structure in the required frequency band - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention relates to the field of radio engineering, in particular, to measuring equipment, and can be used to measure the value of actual attenuation of the electromagnetic field created by radio-electronic means for various purposes in the required frequency band and to evaluate the shielding properties of shielded structures. Proposed is a method for automated measurement of the levels of electromagnetic radiation in the structural elements of a shielded structure in the required frequency band, wherein a signal is formed using a signal source and subsequently emitted by means of a transmitting antenna, the signal received by a receiving antenna is processed using an electromagnetic energy level meter. Prior to receiving and measuring the signal level, the receiving path is calibrated, the signal level from the signal source is measured, and a theoretical calculation of signal attenuation in a free space is conducted. Antennas are used with a broad directional pattern, placed at different sides of the structural element of the shielded structure. The emitted signal is therein formed at control frequencies in accordance with a predetermined time interval, the level of the signal received by the receiving antenna is measured. The frequency band corresponding to the operating frequency range of the shielded structure is set on the electromagnetic energy level meter, and the received signal is processed in the accumulation mode or in the peak power level recording mode.

EFFECT: increased accuracy of evaluating the efficiency of shielding.

1 cl, 1 dwg

Description

The invention relates to the field of radio engineering, in particular, to measuring equipment, and can be used to measure the value of the real attenuation of the electromagnetic field created by radio electronic means for various purposes in the required frequency band, and to assess the shielding properties of shielded structures (ES), for example, rooms, cameras etc.

Throughout the entire life cycle of an ES, it is necessary to confirm the effectiveness of shielding both the ES as a whole and its structural elements, in particular, due to the fact that over time due to the influence of external factors, this characteristic deteriorates, as a result of which the requirements regarding shielding efficiency established for a specific ES. To confirm the effectiveness of shielding and further unhindered operation of the ES, it is necessary to periodically assess the effectiveness of the shielding of the ES.

From the prior art, a method is known for determining the value of the real attenuation of the electromagnetic field, implemented by the "Automated complex for determining the coefficient of real attenuation of the electromagnetic field during certification tests of information objects" ZOND ", produced by ZAO NPTs Firm" Nelk "(https://nelk.ru/catalog/ sistemy_otsenk_zashchishchennosti_informatsii / dopolnitelnoe_i_vspomogatelnoe_oborudovanie / zond-2 /), which consists of a sinusoidal high-frequency signal generator, a power amplifier, a transmitting antenna, a measuring receiver with a set of receiving antennas and a control personal computer (PC). In this case, a spectrum analyzer is used as a measuring receiver. The control of the restructuring of the generator of sinusoidal signals is carried out via the RS-232 interface (interface for connecting a computer with a data transmission device) from a control PC. Data exchange between the spectrum analyzer and a PC is carried out via the GPIB bus (General Purpose Interface Bus).

Using this device, the level of the electric field strength is measured, created by the source of a continuous high-frequency sinusoidal signal and the transmitting antenna at specified points in space at specified frequencies, and the obtained values of the electric field strength are compared with the value of the electric field strength at the location of the receiving antenna. Reconstruction of the generator of sinusoidal signals and the spectrum analyzer (measuring receiver) is carried out synchronously according to the commands of the control PC.

The disadvantage of this method is the low reliability of the measurement results at large values of the attenuation of the electromagnetic field (more than 40 dB), which occurs when assessing the effectiveness of the ES shielding, a limited range of controlled frequencies, a long waiting time for control commands from a PC (up to 25 sec), the presence of a connecting cable with an RS-232 interface to control the tuning of the generator of sinusoidal signals from the control PC, which increases the likelihood of leakage of the HF signal from the generator of sinusoidal signals through the elements of the ES structures and leading to a decrease in the efficiency of shielding of the ES.

A known method for measuring the efficiency of shielding shielded rooms, implemented by a device (A Low-cost Method for Shielded Enclosure Integrity Monitoring. Walter E. Gordon.ITEM 1994. P. 199.), consisting of a signal generator that generates a sinusoidal signal with a fixed frequency of 900 MHz, power amplifier, attenuator, transmitting antenna, measuring antenna, bandpass filter, preamplifier and detector. The disadvantage of this solution is that the shielding efficiency is measured only at one fixed frequency, which does not allow judging the shielding properties of the object in the required frequency range.

The closest in technical essence to the claimed technical solution is a method for measuring the magnitude of the real attenuation of the electromagnetic field and assessing the effectiveness of shielding, implemented by the device (patent RU 136183, IPC: G01R 29/00, published on 12/27/2013), containing a generator of sinusoidal signals, a power amplifier, modulator and generator of complex signals, transmitting antenna, receiving antenna, measuring receiver, PC and device for optimal signal processing.

The generator of sinusoidal signals generates a high-frequency signal (carrier) with a frequency from a given list in the required frequency range stored in the PC, which is fed to the input of the modulator, to the control input of which a modulating signal is supplied from the output of the generator, which generates a complex, for example, noise-like signal of a certain duration. The modulator transfers the spectrum of the complex signal (SS) to the carrier frequency of the generator of sinusoidal signals by any of the linear types of modulation. Next, the modulated signal is fed to a power amplifier, where it is amplified to the required level, and is emitted by a transmitting antenna. A receiving antenna with a measuring receiver located at a given point in the surrounding space provides reception and preliminary processing (filtering) of this signal. The generator of sinusoidal signals and the measuring receiver are tuned in frequency synchronously, according to the commands coming from the PC. The signal from the output of the measuring receiver is fed to the input of the optimal processing device CC, by means of which the optimal processing of the received complex signal is realized based on the correlator or matched filter. From the output of the device for optimal processing of the SS, the processed signal enters the PC, which provides control over the tuning of the generator of sinusoidal signals and the measuring receiver, processes the measuring information coming into it and displays the measurement results.

The disadvantages of this technical solution should be recognized the complexity of the equipment used, the presence of a connecting cable with an RS-232 interface to control the tuning of the generator of sinusoidal signals from the control PC, which increases the likelihood of leakage of the RF signal from the generator of sinusoidal signals through the elements of the ES structures, and thereby leading to a decrease in efficiency ES shielding.

The technical problem solved by the creation of this invention lies in the insufficiently high accuracy of assessing the shielding efficiency of both the ES as a whole and its structural elements, due to the low reliability of determining the value of the real attenuation of the electromagnetic field.

The technical result of the claimed invention is aimed at creating a method that makes it possible to increase the accuracy of assessing the shielding efficiency of both the ES as a whole and its structural elements, by ensuring high reliability in determining the value of the real attenuation of the electromagnetic field.

The specified technical result is achieved by the fact that in the method of automated measurement of the levels of electromagnetic radiation in the structural elements of a shielded structure in the required frequency band using a signal source, a signal is generated with its subsequent emission by means of a transmitting antenna, energy. Before receiving and measuring the level of the leaked signal, the receiving path is calibrated, the signal level from the signal source is measured, and the theoretical calculation of the signal attenuation in free space is carried out. When carrying out measurements, antennas with a wide radiation pattern are used as transmitting and receiving antennas, which are placed on opposite sides of a structural element of the shielded structure, while the emitted signal is formed at the control frequencies from the operating frequency range of the shielded structure in accordance with a given time interval. After that, the level of the signal leaked through the structural element of the shielded structure, received by the receiving antenna, is measured, while the frequency band corresponding to the operating frequency range of the shielded structure is set on the electromagnetic energy level meter, and the received signal is processed in the accumulation mode, or in the mode of fixing the peak power level ...

The proposed method for automated measurement of the levels of electromagnetic radiation in the structural elements of a shielded structure in the required frequency band is based on the transmission and reception of a signal using the transmitting and receiving antennas, respectively, followed by measuring the level of the received (leaked) signal. In this case, antennas with a wide radiation pattern are used as these antennas, which are placed on opposite sides of the ES structural element. The signal emitted by the transmitting antenna is generated using a signal source connected to this antenna, and an electromagnetic energy level meter is used to measure the received signal level.

Measurement of levels of electromagnetic radiation is necessary when assessing the effectiveness of ES shielding.

Consider the implementation of the proposed method using the example of the circuit shown in the figure, where:

1 - signal source;

2 - transmitting antenna;

3 - structural element of a shielded structure (EKES);

4 - receiving antenna;

5 - meter for the level of electromagnetic energy;

6 - transmitting path;

7 - receiving path.

Signal source 1 generates a signal arriving at the transmitting antenna 2, which, in combination with the indicated signal source 1, forms a transmitting path 6. With the help of the transmitting antenna 2, the signal is emitted to the EKES 3, which can be, for example, a wall, ceiling, door, filter, etc. On the other hand, the EKES 3 receiving antenna 4 receives the leaked signal, the level of which is determined and further processed using an electromagnetic energy level meter 5 (spectrum analyzer, measuring receiver, etc.) connected to the receiving antenna 4, which in turn form receiving path 7.

It should be noted that the specified equipment is selected taking into account the range of operating frequencies of radio electronic equipment and technological equipment, work with which is carried out in the ES, as well as the required efficiency of shielding the elements of the ES structures.

Measurement of levels of electromagnetic radiation in structural elements of a shielded structure is carried out as follows.

First, the receiving path is calibrated, while the signal level is measured from the signal source 1, which simulates the operation of the product, its component or the technological equipment, which is operated in the ES. The maximum obtained value of the signal level is taken as the operating signal level at a distance of 1 meter from the product.

A theoretical calculation of the free space attenuation of the electromagnetic signal is then carried out (Recommendation ITU-R P.525-2 *, Calculation of the free space attenuation, internet: https://www.itu.int/dms_pubrec/itu-r/rec/p/ R-REC-P.525-2-199408-S !! PDF-R.pdf) by the formula:

where L is the signal attenuation, (dB);

d is the distance from the product to the antenna installation site (km);

f - signal frequency (MHz).

The total attenuation from signal source 1 to receiving antenna 4 will be calculated using the formula:

where L _es is the minimum value of the shielding efficiency of a shielded structure, which provides the required protection against signal leakage;

L _sv.p - signal attenuation value in free space;

L _pt - the value of the signal attenuation introduced by the receiving and transmitting paths, determined during the system calibration.

The value of the signal attenuation obtained in this way is set as the minimum necessary for the possibility of carrying out work in the ES.

In accordance with GOST 30373-95 / GOST R 50414-92 “Electromagnetic compatibility of technical equipment. Equipment for testing "tests of the ES for the shielding efficiency must be carried out at least at five control frequencies (including at two extreme) of the operating range of the ES (this operating range is set individually for each specific ES during its manufacture). For the convenience of measurements, this method implements the possibility of automated measurement of the levels of electromagnetic radiation in structural elements of shielded structures in the entire operating range of the ES by setting the control frequencies from the operating frequency range at the signal source 1, as well as the time interval during which the signal source 1 will form a signal at a given control frequency and setting the frequency band corresponding to the operating frequency range of the ES, on the meter of the level of electromagnetic energy 5, with the accumulation mode turned on, or the mode of fixing the peak power level.

When the electromagnetic energy level meter 5 operates in the accumulation mode, in the event of a signal leakage at the control frequency, the indicated signal will be sequentially recorded on the screen of the electromagnetic energy level meter 5 with a gradual increase in its level to the maximum leakage level, which will allow the most accurate determination of the signal leakage. The signal level will need to be determined based on the signal spectrogram on your own.

When the meter of the level of electromagnetic energy 5 operates in the mode of fixing the peak power level, it will record the maximum level of the leaked signal for the entire measurement period with a marker, indicating its exact value, which will make it possible to more accurately determine the fact of leakage and the signal level.

At the same time, the main advantage of the proposed measurement method, in contrast to the prototype, is that in this method there is no need to connect the measuring equipment on the transmitting and receiving sides using connecting cables, which increases the accuracy of assessing the effectiveness of shielding the ES as a whole and its structural elements, in particular, and the reliability of determining the magnitude of the real attenuation of the electromagnetic field. The positive effect is achieved by eliminating the need to lay a connecting cable connecting the transmitting and receiving sides, during which the radio-tightness of the ES can be violated, or if specialized radio-frequency filters were supposed to be used for laying the connecting cable, then there is no need to use them, which leads to a simplified design of the ES ... In addition, a positive effect is the optimization of the composition of the measuring equipment used to check the ES, by excluding the PC from it.

Claims (1)

A method for automated measurement of the levels of electromagnetic radiation in structural elements of a shielded structure in the required frequency band, in which a signal is generated with the help of a signal source, followed by its emission through a transmitting antenna, the signal received with the help of a receiving antenna is processed, using an electromagnetic energy level meter, characterized by that before receiving and measuring the level of the leaked signal, the receiving path is calibrated, the signal level from the signal source is measured, and the theoretical calculation of the signal attenuation in free space is performed; different sides of a structural element of a shielded structure, while the emitted signal is generated at control frequencies from the operating frequency range of the shielded structure in accordance with a given time interval, after that, the level of the signal leaked through the structural element of the shielded structure is measured and received by the receiving antenna, while the frequency band corresponding to the operating frequency range of the shielded structure is set on the electromagnetic energy level meter, and the received signal is processed in the accumulation mode or in the mode of fixing the peak power level.

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