RU2393493C1 - Method of determining signal attenuation in distributed random antenna - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: method of determining signal attenuation at frequency f_c between points A and B in a distributed random antenna involves measurement of the signal power level P₁ at point A of the distributed random antenna, measurement of the signal power level P₂ at point B of the distributed random antenna and calculation of signal attenuation on the path between points A and B using formula A_c=20lg(P₁/P₂), dB; the distributed random antenna is excited at the frequency of the signal subharmonic f_n=f_c/n using a nonlinear element connected to the distributed random antenna and signal power level P₁ and P₂ is measured on the n-th harmonic of the exciting frequency which is numerically equal to frequency f_c.

EFFECT: increased accuracy of results of determining attenuation A_c of a signal in a distributed random antenna with a branched and multi-stage configuration, possibility of automating the measurement process.

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Description

The invention relates to techniques for radio measurements and can be used to determine the parameters of radio systems, combined by the term "distributed random antennas" (PCA).

The classification and properties of random antennas are considered in [1-2]. Distinctive features of PCA are, firstly, the random nature of the placement and excitation of its linearly extended (or planar) conductive elements (which may include signaling, control, power supply, grounding, etc.). To ensure commercial secrets, it is important to identify and block the channels of confidential information leakage (CI) for such SAR in the form of connecting lines (SL), departing from the premises to be protected (PPP) - offices, office rooms, meeting rooms and booths, conference rooms into the external environment [3].

Secondly, the essentially different nature of the propagation of the initial KI signal inside the PZP and KI signals in the trunk, with the help of which the equipment located in the PZP is connected to external public equipment. As a result of this, KI signals can go far beyond the PZP along the SAR and become unauthorized.

Thirdly, the difficulties of modeling (mathematical, physical, computer) SLs that are SAR: in particular, neither in the theory of antennas nor in the literature on the protection of CI there are indications of using which methods and means it is possible to evaluate SAR parameters - for example, the degree of attenuation of the KI signal in the occupied frequency band.

Known methods for determining the parameters of feeder lines, including the attenuation coefficient α; 1 / m or dB / m [4]. There is a proposal to use reflective surfaces with controlled non-linear parameters for covert communication between subscribers [5]. The methodological apparatus for assessing the effectiveness of non-linear radio communications and radio suppression is described in detail in [6]. The results of research in the field of nonlinear radar are presented in [7].

The closest in technical essence is a method of measuring the attenuation coefficient of the feeder by comparing the input and output power ([4], p. 170, Fig. 7.4) (prototype of the invention), including the following operations:

- measurement of power P ₁ supplied to the feeder length L;

- measurement of power P ₂ emerging from the feeder of length L;

- determination of the attenuation coefficient: α = (1 / 2L) ln (P ₁ / P ₂ ), 1 / m or directly the attenuation value of the signal in the feeder with a length L: And _with = 20 log (P ₂ / P ₂ ), dB.

The main disadvantage of the prototype method, as applied to SAR, is its low metrological accuracy, since in practice it was impossible to measure the signal strength P ₁ at point A and the signal power P ₂ at point B in a SAR section of length L with the required methodological error, between which it is necessary find the attenuation A _{from the} signal at a frequency f _c . This is due to the fact that in addition to the electrical connection between points A and B through the SAR, there is an electromagnetic connection between points A and B through the surrounding space. Therefore, the measurement results P ₁ and P ₂ carry information about the signal power levels at a frequency f _c entering the measuring device both through the SAR and through the surrounding space at the same time. The “spatial addition” to the levels of P ₁ and P _{2 is} not related to SAR and is a negative factor that significantly increases the methodological error in determining signal attenuation in SAR.

The proposed solution to the problem is that when determining the attenuation of A _{from the} signal between points A and B in the SAR at a frequency f _c, exclude the electromagnetic effect of the SAR excitation source on the instrument that measures P ₁ and P ₂ : first, by exciting the SAR on subharmonic frequency f _n = f _c / n, and secondly, by connecting to a PCA a nonlinear element (NE) to increase the "energy weight" of the signal of the nth harmonic of the excitation frequency, that is, the signal at a frequency f _c . With the simultaneous measurement of P ₁ and P ₂ using a two-channel device, the process of determining A _c can be automated.

The technical result of the invention is to increase the accuracy of determining signal attenuation in an SAR by reducing the methodological error by reducing the electromagnetic influence of the SAR excitation source on the measuring device through the surrounding space. An additional result is an increase in the level of the measured signal due to PCA excitation with the help of NEs at the signal subharmonic frequency f _n = f _c / n and the possibility of automating the measurement process using a two-channel power meter P ₁ and P ₂ .

The essence of the proposed method for determining the attenuation of a signal at a frequency f _c between points A and B in a distributed random antenna, including measuring the signal power level P ₁ at point A of a distributed random antenna, measuring the signal power level P ₂ at point B of a distributed random antenna and calculating signal attenuation on the way between points A and B according to the formula A _with = 20 log (P ₁ / P ₂ ), dB, consists in the fact that the distributed random antenna is excited at the signal subharmonic frequency f _n = f _c / n using a non-linear element, conn feeding your distributed random antenna and measuring the power levels P ₁ and P ₂ to produce signal n-th harmonic of the excitation frequency that is numerically equal to the frequency f _c.

Figure 1 shows a diagram of an implementation of a prototype — a known method for measuring the attenuation coefficient of a feeder (as applied to an SAR with a complex multi-story structure) by comparing the input and output power ([4], p. 170, Fig. 7.4) of a section of length L between points A and In, where 1 is a signal generator for exciting PCA at a frequency f _c ; 2 - signal excitation device in SAR; 3 - SAR in the form of a branched heterogeneous SL; 4 - device for signal pickup at points A and B of the SAR; 5 - meter power level signal at a frequency f _c .

Figure 2 illustrates an implementation diagram of the proposed method for determining signal attenuation in an SAR, where 1 is a signal generator for exciting a SAR at a subharmonic frequency f _n = f _c / n; 2 - signal excitation device in SAR at a subharmonic frequency f _n = f _c / n; 3 - SAR in the form of a branched heterogeneous SL; 4 - devices for signal pickup at points A and B of the SAR; 5 - meter signal power level at a frequency f _c ; 6 - non-linear element connected to the SAR.

Figure 3 represents the experimental spectrograms, which indicate: a) the level of the main signal is 91 dB passing to the meter 5 through SAR 3 in the form of a wire without NE and the environment, and the level of the main signal is 98.7 dB passing to the meter 5 through the environment at a distance of L = 110 m: from the 3rd to the 4th floor of the city building; 6 - the level of the main signal - 97 dB, passing to the meter 5 through the SAR in the form of a wire without NE and the environment, and the level of the main signal - 100 dB, passing to the meter 5 through the environment at a distance L = 120 m: from 2 to 4 floor of a city building.

Figure 4 represents the experimental spectrograms, which indicate: a) the background signal level is 107 dB for SAR 3 in the form of a single wire without NE at a distance of L = 5 m; b - the signal level of the second harmonic - 75.2 dB for SAR 3 in the form of a wire with NE at a distance of L = 5 m; c - the level of the third harmonic signal - 100 dB for SAR 3 in the form of a single wire with NE at a distance of 5 m.

Figure 5 represents the experimental spectrograms, which indicate: a) the background signal level is 108 dB for SAR 3 in the form of a pipe system without NE at a distance of L = 8 m; b - second harmonic signal level - 91.6 dB for SAR 3 in the form of a system of pipes with NE at a distance of L = 8 m; c - signal level of the third harmonic - 100 dB for SAR 3 in the form of a system of pipes with NE at a distance of 8 m.

6 shows options for connecting NE 6 to SAR 3: a) - galvanic; b) inductive; c) - capacitive connection.

Figure 7 shows the device 2 (in the form of a loop antenna) of excitation of the SAR 3 and NE 6 connected to the SAR 3 according to the variant of Fig.6b (inductive connection).

On Fig shows the device 4 of the signal pickup (in the form of a ring ferrite antenna) with SAR 3.

The known prototype method is as follows.

At the first stage (see Figure 1), the signal generator 1 with a frequency f _{c is} connected to the PCA 3 through the PCA excitation device 2 (in reality, the transmitting antenna connected to the generator 1 can act as a device 2); a signal power level meter 5 at a frequency f _{c is} connected through a signal pickup device 4 to a PCA 3 at point A, after which a signal power level P ₁ is measured at a given point (in the prototype, point A is the input of the feeder, it can be in any PCA at any arbitrary cross-section of the PCA).

At the second stage, the signal pickup device 4 and the signal power level meter 5 are disconnected from point A and connected to the SAR 3 at point B (as shown in Fig. 1 by dashed lines), after which the power level P _{2 of the} signal is measured at this point ( in the prototype, point B is the output of the feeder, in PCA it can be in any arbitrary cross-section of the PCA).

At the third stage in the prototype, the signal attenuation coefficient is determined in the feeder with the length L: α = (1 / 27L) ln (P ₁ / Р ₂ ), 1 / m, and with respect to the SAR, the signal attenuation value is directly: А _с = 20 log ( P ₁ / P ₂ ), dB.

In terms of solving this problem: when determining the signal attenuation at a frequency f _c between points A and B in a real SAR, the prototype method has the following disadvantages.

1. The determination of signal power levels P ₁ at point A and P ₂ at point B in a PCA section of length L where it is necessary to find the attenuation of A _{from the} signal at a frequency f _c is made with an unsatisfactory methodological error due to the fact that, in addition to a stable electrical connection between by points A and B through the SAR (which the value of A _c is intended to estimate), there is an unstable electromagnetic coupling through the environment between the generator 7 with the SEC 3 excitation device 3, on the one hand, and the signal power level meter 5 at a frequency f _c , the follower but connected via signal pick-up device 4 to PCA 3 at points A and B, on the other hand.

This is clearly seen in the spectrograms of Fig. 3a: a signal at a frequency f _c from 3 floors to 4 floors (L = 110 m) of a city building passes through a PCA in the form of a single wire and an environment with a level of 91 dB; and through the environment - with a level of 98.7 dB; and Fig.3b: a signal at a frequency f _c from 2 floors to 4 floors (L = 120 m) of the same building passes through the same SAR and the environment with a level of 97 dB; and through the environment - with a level of - 100 dB. At closer distances L, which are also of interest for the protection of IC, the indicated levels become almost the same. All this does not allow to isolate the signal at a frequency f _c passing through the SAR from point A to point B, against the background of the total signal passing through the SAR and through the environment.

2. The level of the total signal passing from point A to point B and through the SAR and through the environment is unstable in time and space (the spectrograms in Figure 3 fluctuate and vary significantly). This additionally complicates the procedure for measuring signal power levels P ₁ at point A and P ₂ at point B and increases the undesirable methodological error in determining attenuation A _{from the} signal in the SAR at a frequency f _c .

Therefore, the present invention proposes, firstly, when determining the attenuation of A _{from a} signal between points A and B at a frequency f _c, eliminate the electromagnetic influence of the generator 1 and the signal excitation device 2 (in real conditions, it is a transmitting antenna) on the signal power level meter 5 through the environment by exciting PCA 3 at a subharmonic frequency f _n = f _c / n; secondly, by connecting to PCA 3 NE 6 to increase the "energy weight" of the signal of the nth harmonic of the excitation frequency, that is, the signal at a frequency f _c .

The proposed method is as follows.

At the first stage (see Figure 2), the signal generator 1 with the subharmonic frequency f _n = f _c / n through the device 2 for excitation of the SAR (device 2 can also be a transmitting antenna connected to the generator 1) and NE 6 is connected to PCA 3; the signal power level meter 5 is connected through a signal pick-up device 4 to the SAR 3 at point A, after which the power level P _{1 of the} signal is measured at the nth harmonic of the excitation frequency, numerically equal to the frequency f _c , at this point.

At the second stage, the pick-up device 4 and the signal power level meter 5 are disconnected from point A and connected to the SAR 3 at point B (as shown in Fig. 2 by dashed lines), after which the power level P _{2 of the} signal is measured at a frequency f _c in point B is similar to point A. When using a two-channel meter 5 of the signal power level connected to the SAR 3 at points A and B at the same time, there is no need to reconnect the signal power level meter 5 from point A to point B.

At the third stage, the signal attenuation at a frequency f _c between points A and B in the SAR is determined by the formula A _with = 20 log (P ₁ / P ₂ ), dB.

In contrast to the prototype method, the proposed method, firstly, allows you to "decouple" in frequency the PCA 3 excitation operation (at a frequency f _n = f _c / n) and the operation of measuring signal power levels at points A and B (at a frequency f _c ), therefore, the effect of unstable electromagnetic coupling through the environment between the generator 1 with the PCA 3 excitation device 2, on the one hand, and the signal power level meter 5 at a frequency f _c connected through the signal pickup device 4 to the PCA 3 at points A and B , on the other hand, is practically absent - regardless of masks the distance L between points A and B in the X-ray diffraction.

Secondly, the excitation of the PCA 3 through NE 6 significantly increases the overall signal level in the PCA at a frequency f _c against the background of noise, therefore, the signal power meter 5 at points A and B operates at higher signal-to-noise ratios compared to the prototype, which also positively affects the metrological accuracy of the determination of attenuation And _with .

The spectrograms of the signal levels at the harmonics of the frequency f _n = 890 MHz, presented in Fig.4-5, confirm this. For PCA in the form of a single wire without NE 6 at L = 5 m (see Fig. 4a), the background signal level is equal to 107 dB; for SAR in the form of a wire with NE under the same conditions (see Fig. 4b and Fig. 4c) the harmonic signal level 2 (at a frequency f _c = 1780 MHz): - 75.2 dB and the harmonic signal level 3 (at a frequency f _c = 2670 MHz): - 100 dB.

Similarly, for SAR in the form of a system of branched (heating, water) pipes without NE 6 at L = 8 m (see Fig. 5 a) the background signal level is 108 dB; for SAR in the form of a system of pipes with NE under the same conditions (see Fig. 5b and Fig. 5c) the harmonic signal level 2 (at a frequency f _c = 1780 MHz): - 91.6 dB and the harmonic signal level 3 (at a frequency f _c = 2670 MHz): - 100 dB.

From Fig.4-5 it is clearly seen that the proposed method, using the connection to the SAR 3 NE 6, allows you to determine the attenuation And _with the required distances between points A and B (including at L <10 m) with metrological accuracy corresponding to the instrumental the error of the signal power meter 5, since at n = 2 the signal level at f _c is 17-31.8 dB higher than the noise level, and even with n = 3 the excess is stably 7-8 dB - unlike the prototype, where excesses of the order of 3-7 dB are recorded in unstable conditions at L = 110-120 m.

Implementation options for connecting NE 6 (in the form of a microwave germanium modulator diode D401) to PCA 3 (galvanic, inductive, capacitive) are shown in Fig.6. Galvanic connection (serial or parallel) of NE 6 to RSA 3 is made by soldering or threaded connection of wires connected to NE 6, inductive - by winding wires connected to NE 6 to the PCA 3 section; capacitive - with the help of metal-dielectric pads (clamps) connected by wires with NE 6 and installed on the PCA 3 section.

In the experimental determination of the attenuation A _{c, we} used the embodiments of the PCA 3 excitation device 2 in the form of a vibrator and frame antennas (the PCA 3 excitation option in the form of a system of metal pipes through the frame antenna is illustrated in Fig. 7). The signal pickup device 4 was a ring ferrite antenna (for the appearance of the SAR 3 in the form of a system of metal-plastic pipes, see Fig. 8); A spectrum analyzer manufactured by Rode & Schwarz was used as a signal power level meter 5 in PCA 3.

The proposed method is universal, simple and effective, it is convenient to implement and easily amenable to automation when using a two-channel meter 5 signal power in PCA 3.

Literature

1. Maslov O.N. Random antennas // Telecommunications. No. 7, 2006. - S.12-15.

2. Maslov ON, Solomatin MA, Orlov AB Multichannel random antennas // Infocommunication technologies. V.5, No. 4, 2007. - S. 47-52.

3. Kechiev L.N., Stepanov P.V. EMC and information security in telecommunication systems. M .: Publishing House "Technologies", 2005. - P.320.

4. Fradin A.Z., Ryzhkov E.V. Measurement of antenna parameters. M .: Svyazizdat, 1962.316 s.

5. The method of radio communications and systems for its implementation // Golovkov AA, Volobuev AG, Chaplygin AA et al. Patent RU 2271065 C1 of 06/09/2004, publ. 02/27/2006, Bull. No. 6.

6. Aliev D.S., Avdeev V.B., Vaganov E.S., Vaganov M.S., Panychev S.N. Methodological apparatus for evaluating the effectiveness of non-linear radio communications and radio suppression // Telecommunications, No. 7, 2007. - S.35-40.

7. Non-linear radar. Digest of articles. Part 1. M .: Radio engineering, 2005. - 96 p.

Claims (1)

A method for determining signal attenuation at a frequency f _c between points A and B in a distributed random antenna, comprising measuring a signal power level P ₁ at point A of a distributed random antenna, measuring a signal power level P ₂ at point B of a distributed random antenna, and calculating signal attenuation along the way between points A and B according to the formula A _c = 20 log (P ₁ / P ₂ ), dB, characterized in that the distributed random antenna is excited at the signal subharmonic frequency f _n = f _c / n using a non-linear element connected to the distributed random antenna, and the measurement of signal power levels P ₁ and P _{2 is} performed at the nth harmonic of the excitation frequency, numerically equal to the frequency f _c .

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