RU2282178C1 - Radio introscope - Google Patents

Abstract

FIELD: search and localization of medium heterogeneities.

SUBSTANCE: proposed radio introscope is primarily used for searching and localizing nonlinear artificial anisotropic scatterers concealed in sheltering surface which incorporate semiconductor components in their composition. Device makes use of two properties of such objects at a time during their radio location: signal frequency conversion into higher harmonics and reversal of its polarity. For the purpose device incorporates provision for (a) frequency-polarized division of signals in antenna sensor to ensure decoupling of transmitter and receiver at sounding signal frequency and (b) passage of nonlinear anisotropic scatterer echo signal to receiver input.

EFFECT: enlarged functional capabilities.

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Description

The invention relates to radar, and in particular to methods for determining the location of inhomogeneities in various environments when irradiated with a high-frequency electromagnetic field, and can be used in the radio wave technique for measuring the dielectric parameters of materials and in underground geophysics.

Known radar search and detection of the so-called non-linear scatterers (HP) - inhomogeneities of the medium with non-linear electromagnetic properties / 1 /. Known radar devices, either directly designed to solve this problem, or which can obviously be used to solve it without making fundamental changes to them / 2, 3, 4, 5 /. B / 2, 3 / uses the ability of HP to convert the frequency of the probing signal into higher harmonics during re-reflection, the intensity of which, after their frequency selection in the receivers, a decision is made on the presence of HP. V / 4 /, another, less informative “energy” method for detecting HP is used, based on the nonlinear dependence of the power of the reflected signal on the power of the probe, which is detected by varying the power of the HP irradiating signal controlled by the antenna system. Using the device / 5 /, which measures the power of the cross-polarization component of the reflected signal, one can also detect HP, but only those that have the additional property of rotating the plane of polarization of the reflected signal relative to the plane of polarization of the probe signal. It is important to note that the majority of artificial HP disguised in a covering surface are electronic electronic industrial espionage schemes (various "bugs"), electronic fuses, etc. containing semiconductor elements - diodes, transistors, etc., - have such a depolarizing (anisotropic) property. In / 5 /, the polarization selection of HP is achieved by the mutually orthogonal arrangement of the transmitting probe that converts the electrical signal of the high-frequency generator into a linearly polarized electromagnetic wave, and the receiving probe that converts the cross-polarization component of the reflected wave into the input signal of the receiver.

The disadvantage of analogues is the low efficiency of solving the HP detection problem due to the following reasons:

- for / 2, 3 / —this is the small suitability of their antenna systems for solving the radiointroscopy problem of interest to us — the search and localization of HP located in the covering surface at distances comparable with the wavelength of the probe signal when the surface being examined is located in the near zone of the antenna moving along it systems;

- for / 4 / - this is a relatively high level of interference signals from the covering surface in the absence of the possibility of detecting HP by the fine structure of the reflected signal, namely using the frequency - in the sense of multiple harmonics - selection of isotropic HP or polarization selection of anisotropic HP;

- for / 5 / - this is insufficient isolation across the field between the receiving and transmitting probes, despite their optimal mutually orthogonal orientation in space, as a result of which the probing signal penetrates the receiver and thereby reduces the contrast of the HP observation.

Closest to the proposed one is a radio introscope that implements a "Method for controlling the dielectric constant anisotropy of dielectrics" / 6 /, in which the level of the cross-polarization component of the reflected signal is measured. Polarization processing in / 6 / is performed using a simple antenna sensor in the form of a segment of a waveguide of rectangular cross section with two mutually orthogonal - transmitting and receiving probes, the open end (opening) of which is parallel to the surface being examined and emits a wave of type H ₁₀ . Assuming the presence of HP with anisotropic properties, the signal received by the opening contains a cross-polarization component, which is perceived by the waveguide as a wave of the type H ₀₁ .

The disadvantage of the prototype is its low sensitivity when detecting HP due to insufficient isolation on the field between the receiving and transmitting probes.

The aim of the invention is to increase the sensitivity of the radio introscope when searching for nonlinear anisotropic inhomogeneities of the medium.

To achieve this goal, a radio introscope containing a rectangular waveguide with a vertically arranged narrow wall of size b and a wide wall of size a = η b, a transmitting probe connected to a high-frequency generator and a first receiving probe connected to the first input of the receiver, located in the narrow wall of the first waveguide additionally introduced a second, coaxial with the first, waveguide of rectangular cross section with a horizontally located narrow wall of size b ^* = a and a wide wall of size a ^* = η b ^* , connected to the first m by smoothly transitioning the wide wall of the first waveguide into the narrow wall of the second waveguide and the narrow wall of the first waveguide into the wide wall of the second waveguide, the second receiving probe connected to the second input of the receiver and placed in the wide wall of the first waveguide, the transmitting probe being placed in the wide wall of the second waveguide, the frequency F of the high-frequency generator is selected from the condition

where f ₁₀ is the minimum critical frequency of the first waveguide, and the receiver performs the function of a second harmonic filter 2F in the signals received by the first and second receiving probes.

1, 2 are illustrated

- diagram of the device (figure 1), where in addition to the antenna sensor in the form of two smoothly connected first and second waveguides, a high-frequency generator 1 and a receiver 2 are connected to it;

- the relative position of the frequency F of the high frequency generator, the second harmonic 2F and the critical frequencies of the waveguides on the frequency axis (figure 2).

We proceed to consider the operation of the radio introscope of figure 1, using the following notation:

- H ₁₀ , H ₀₁ - types of waves of the first waveguide with the corresponding critical frequencies f ₁₀ and f ₀₁ ;

- H ^* ₁₀ , H ^* ₀₁ - wave types of the second waveguide with the corresponding critical frequencies f ^* ₁₀ and f ^* ₀₁ .

In the future, for convenience and without loss of generality, we assume that the radiated signal has horizontal polarization. In relation to the spatial orientation of the antenna sensor (Fig. 1), the waves H ₁₀ and H ^* ₀₁ are vertical, and the waves H ₀₁ and H ^* _{10 have} horizontal polarization.

If the size b ^{* of the} narrow wall of the second waveguide coincides with the size a of the wide wall of the first waveguide, we obtain the coincidence of critical frequencies

The high-frequency generator 1, using a transmitting probe, excites a probe signal in the second waveguide - a horizontally polarized wave of type H ^* ₁₀ , and at a frequency F exceeding the critical frequency f ^* ₁₀ , but not exceeding the critical frequency f ^* ₀₁

As a result of the irradiation of an isotropic surface with anisotropic HP by the probe signal, the reflected signal having a horizontally polarized frequency component F from the isotropic surface, horizontally and vertically polarized frequency components 2F from anisotropic HP returns to the opening of the second waveguide. The probe signal and the components of the reflected signal of frequency F do not penetrate the first waveguide due to the criticality of frequency F for all types of its waves. The reflected HP signal at the second harmonic of 2F with any polarization can propagate from the aperture to the receiving probe with low loss if the frequency of 2F exceeds the critical frequency f ₀₁ :

which is the maximum among all considered critical frequencies. The system of inequalities (2), (3) determines the condition for choosing the frequency F. To solve this system, we introduce the assumption that the proportionality coefficient η (1 <η) coincides between the size of the wide and narrow walls for both waveguides

from which the relationship of the critical frequencies f ₁₀ and f ₀₁ follows, as well as f * ₁₀ and f * _01/7 /:

Solving the system of inequalities (2), (3) taking into account (1) and (5), we obtain restrictions on the choice of the probing frequency:

Thus, a positive effect is achieved by frequency-polarization separation of signals in the antenna sensor, as a result of which, firstly, the isolation of the transmitter and receiver at the frequency of the probing signal and, secondly, the passage of the signal reflected by the nonlinear anisotropic scatterer to the receiver input is ensured.

HP discovery is done in the traditional way:

- filtering and detecting signals of dual frequency 2F in two channels of the receiver associated with the first and second receiving probes, respectively;

- summing their output signals with subsequent display using an indicator device to be able to observe the results of the summation by the operator deciding on the availability of HP.

The receiving and transmitting probes of a capacitive type in the form of pins immersed in the waveguides are located in the middle of the corresponding walls and are connected to the high-frequency generator and the receiver by an internal conductor of the corresponding coaxial line. The distance between the receiving probes and the rear (blank) wall of the first waveguide is a quarter of the wavelength of the useful signal of frequency 2F. The lengths of each of the waveguides and the transition section between them, having the form of a sectorial horn, are selected large enough to ensure a smooth change in wave resistance, the formation of waves of type H ₁₀ , H ₀₁ (in the first waveguide) and H ^* ₁₀ , H ^* ₀₁ (in the second waveguide) and attenuation of waves of higher types.

Information sources

1. Musabekov P.M., Panychev S.N. Non-linear radar: methods, techniques and scope. Foreign electronics. Successes of modern radio electronics, 2000, No. 5, p. 54-61.

2. Patent RU 2079856 C1.

3. Patent RU 2166769 C1.

4. Patent RU 2205429 C2.

5. Patent RU 2121671 C1.

6. Patent SU 1737366 A1.

7. Nikolsky V.V. Electrodynamics and radio wave propagation. Moscow, 1978

Claims (1)

A radio introscope containing a first waveguide of rectangular cross section with a vertically arranged narrow wall of size b and a wide wall of size a = η b, a transmitting probe connected to a high-frequency generator and a first receiving probe connected to a first input of the receiver, located in a narrow wall of the first waveguide, characterized in that a second waveguide of rectangular cross section, coaxial with the first, with a horizontally located narrow wall of size b ^* = a and a wide wall of size a ^* = η b ^* connected to the first m by smoothly transitioning the wide wall of the first waveguide into the narrow wall of the second waveguide and the narrow wall of the first waveguide into the wide wall of the second waveguide, the second receiving probe connected to the second input of the receiver and placed in the wide wall of the first waveguide, the transmitting probe being placed in the wide wall of the second waveguide, the frequency F of the high-frequency generator is selected from the condition

where f ₁₀ is the minimum critical frequency of the first waveguide, and the receiver performs the function of a second harmonic filter 2F in the signals received by the first and second receiving probes.

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