RU2352952C1 - Single-antenna measuring gauge of polarised matrix - Google Patents

Abstract

FIELD: physics, measurement.

SUBSTANCE: invention is related to the field of radiolocation and is intended for measurement of target radiolocating characteristics. Single-antenna measuring gauge of polarisation matrix comprises transmitter, polariser, directional separator of polarisations with E and H side arms, two variables of complex load, two ampliphasemeters and lens transceiving antenna. Antenna lens is arranged with single external refraction surface. Outlet of transmitter is connected to inlet of polariser, outlet of which is connected to inlet of the main arm of directional divider of polarisations. Outlet of polarisations divider is connected to inlet of transceiving antenna. Non-directional outlets of E and H side arms of polarisations divider are connected to variable loads, besides, directional outlets of E and H side arms of polarisation divider are connected to signal inlets of appropriate ampliphasemeters.

EFFECT: reduction of gauge dimensions, increase of its potential and dynamic range of measurements.

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Description

The invention relates to the field of radar and is intended to measure the radar characteristics of targets. The preferred application of the invention is the measurement of the polarization matrix of radar targets on models.

A known measuring device for measuring "non-linear" radar characteristics of targets (RU Pat. No. 2265230 G01R 29/08, G01S 13/04, Bull. No. 33 of 11/27/2005). This device contains a master oscillator, a bandpass filter, a transmitting and receiving antenna, a recorder, a serially connected amplifier, a local oscillator, and a local oscillator frequency stabilization unit. Between the receiving antenna and the recorder, a polarization separator and two parallel receiving channels are connected in series. Each channel consists of a series-connected mixer and an amplifier of the receiving channel. The outputs of the amplifiers are connected to the corresponding inputs of the recorder, and their second outputs are connected to a phase detector, the output of which is connected to the registrar. A directional coupler is introduced between the master oscillator and the bandpass filter. An amplifier and a local oscillator frequency stabilization unit are connected in series to the lateral output of the directional coupler. The transmitting antenna is made of circularly polarized radiation. Two local oscillator outputs are connected to the mixers of the respective receiving channels, the third output is connected to the frequency stabilization unit, and the output of the bandpass filter is connected to the transmitting antenna.

This setup does not allow the measurement of the total polarization matrix, and for measuring complex elements, a large range to the target is required to create measurement conditions that are close to the measurement conditions in the far zone of the antenna, which leads to an increase in the setup potential, the size of the measuring platform and material costs.

The well-known single-antenna backscattering meter (USSR autosw. No. 302810, H03J 5/00, Bull. No. 15 dated 04/28/71) contains a generator, a main and reference channels, a polarizer, a device for separating and recording incident and secondary radiation waves from the target and transmitting the antenna. A device for separating radio waves emitted by the antenna and reflected by the target is made in the form of a waveguide directional polarization separator with a main line of square or circular cross section and with two lateral lines of rectangular cross section. The wide walls of the side waveguides are mutually perpendicular. The backscatter meter is designed to measure the polarization matrix M of the target when fixing the target on a rigid support.

Matrix equation (1), connecting two orthogonal components of the incident radio waves with the corresponding components of the secondary radiation, the target of the radio waves, has the form

where Ei, x and Ei, y are the orthogonal components of the radio waves incident on the target;

Er, x and Er, y are the orthogonal components of the secondary radiation by the target of the radio wave;

a · expiφ _xx , b · expiφ _xy , c · expiφ _yx and d · expiφ _yy are elements of the polarization matrix;

a, b, c and d are the modules of the elements of the polarization matrix;

φ _yy , φ _xx , φ _yh and φ _xy are the arguments of the elements of the polarization matrix.

The matrix M, whose modules are calibrated in the values of the effective scattering surface - σ (EPR), is written as

σ _yy where, σ _{xx yi} and σ, σ _xy - Effective surface scattering target in parallel and orthogonal to the reception of the secondary radiation of radio waves in a predetermined order polarization basis.

The polarization matrix is symmetrical if the transmit and receive antennas are combined. In this case, the matrix elements √σ _yi, expiφ _yx and √σ _xy, expiφ _xy equal and the scattering matrix (2) takes the form

This device measures the full polarization matrix, but for measuring complex elements, a large range to the target is required to create measurement conditions close to the measurement conditions in the far zone of the antenna, which requires increasing the installation potential, the size of the measuring platform and material costs.

A device is known that can significantly reduce the required distance to the target. This device is a collimator made in the form of a lens antenna with a lens with one internal refracting surface (Mayzels E.N., Torganov A.A., Measurement of scattering characteristics of radar targets, M., Sov. Radio, 1972, p. 59, fig. . 3.1.a). A lens with one internal refracting surface approximates the phase distribution of the electromagnetic field in the aperture to the phase distribution in a plane electromagnetic wave, but increases the inhomogeneity of the amplitude distribution of the irradiator, which leads to large measurement errors, to a decrease in the potential of the measuring setup and the dynamic range of measurements.

The amplitude distribution of the field in the aperture of the lens does not coincide with the angular amplitude distribution of the field of its irradiator. When energy passes through the lens due to the different angles of refraction for different rays, the width of the elementary beam beams changes before and after the beam passes through the refractive surface of the lens.

For a lens with an internal refracting surface, the elementary beams incident on the refracting surface expand (Fig. 1), which leads to an increase in the decay of the amplitude distribution from the axis of the lens to the edges, while for a lens with an external refracting surface, the elementary beams incident on the refracting the surface is narrowed (figure 2), thereby increasing the amplitude in the amplitude distribution at the edges of the lens and compensate for the decrease in amplitude caused by the radiation pattern of the irradiator.

Figures 1 and 2 introduced the notation: f is the focal length of the lens; t is the thickness of the lens; α is the angle at which the beam leaves the aperture of the irradiator; r is the beam incident on the refractive surface of the lens at an angle α; θ is the angle formed by the beam r and the perpendicular at the point of its incidence on the refractive surface of the lens; y and x are the coordinates of the Cartesian coordinate system with the center in the phase center of the irradiator; y ₁ and x ₁ are the coordinates of the Cartesian coordinate system with the center at the point of incidence of the ray r on the refractive surface of the lens.

Figure 3 shows the calculated graphs of the relative angular distribution of the power flux P (α) on the outer surface of the lens with an internal (dashed curve) and external (solid curve) refractive surface made of PS-1 foam with a dielectric constant of 1.1. The distribution of the power flux P (α) of the irradiator is indicated by a dash-dot line. The graphs confirm that a lens with an internal refractive surface increases the amplitude heterogeneity, and a lens with an external refractive surface reduces the amplitude heterogeneity in the aperture.

For a lens with one external refractive surface made of PC-1 foam, the opening utilization factor is two times higher than for a lens with one internal refractive surface. With the same size of the amplitude inhomogeneity in the apertures of lenses with an internal and external refracting surface, the latter has a focal length of 2–3 times less, which increases the potential of the measuring setup by 12–19 dB in comparison with a setup equipped with a lens with an internal refracting surface.

The technical result of the invention is to reduce the size of the measuring installation, increasing its potential and dynamic range of measurements, ceteris paribus.

Figure 4 presents the structural diagram of a single-antenna meter. A single-antenna meter of the polarization matrix contains: 1 - transmitter (Prd); 2 - polarizer (Pl); 3 - directional polarization separator (NRP) with orthogonal E and H shoulders; 4 - two variable complex loads (PN); 5 - two ampliphase meters (AF); a lens antenna consisting of an irradiator 6 and a lens (L) 7 with one external refracting surface.

The output of the transmitter 1 is connected to the inputs of the reference signals of the ampliometers 5 and to the input of the polarizer 2. The output of the polarizer 2 is connected to the input of the main arm of the directional polarizer 3. The output of the polarizer 3 is connected to the input of the transceiver antenna. The non-directional outputs E and H of the lateral arms of the polarization separator 3 are connected to the corresponding variable loads 4. The directional outputs E and H of the lateral arms of the polarization separator 3 are connected to the signal inputs of the corresponding ampliometers 5.

The transceiver antenna is made lens of the irradiator 6 and lens 7. Lens 7 is made with one external refracting surface.

Single-antenna meter works as follows. The microwave signal of the transmitter 1 is fed to the input of the polarizer 2, a small part of the microwave signal is fed to the inputs of the reference signals of the ampliometers 5 necessary for measuring the phases. Polarizer 2 converts a wave with vertical linear polarization at its entrance to the wave with the desired polarization at its output (horizontal, inclined, with circular polarization or does not change polarization). From the output of the polarizer 2, the microwave signal goes to the irradiator 6, and from its output to the internal non-refracting surface of the lens 8. An electromagnetic field is formed on the external refracting surface of the lens with uniform distributions of the amplitude and phase with which the target model is irradiated. Reflections of the microwave signal from parts of the microwave path, the irradiator and the lens (local objects) are compensated to the noise level of the amplifiers superheterodyne amplifiers using complex variable loads 4. Using the loads, the amplitude and phase of the signals reflected from them are changed. Then a measured model is placed in front of the lens. The secondary radiation of the target model through the lens and the irradiator enters the output of the main arm of the NRP 3, and from it to the directional outputs E (vertical polarization) and N (horizontal polarization) of the side arms. From the outputs E and H of the side arms of the NRP 3, the signal is fed to the inputs of the corresponding ampliometers 5.

The transmitter 1 is made of continuous radiation. Polarizer 2 has an input of a rectangular waveguide passing into a circular waveguide. The circular waveguide has two quarter-wave inserts, one of which converts the vertical polarization of the wave into a wave with circular polarization, and the second converts circular polarization to linear with the required slope of the plane of polarization. A circular polarizer waveguide goes into a square. The main shoulder of the directional polarization separator 3 has a square cross section, and the side shoulders are made on waveguides of rectangular cross section. Complex load variables 4 are made on a rectangular waveguide with a change in the amplitude and phase of the reflected microwave signal. Ampliphase meters are made with superheterodyne receivers, phase and amplitude detectors, and phase and amplitude recorders. Irradiator 6 is made in the form of a horn. Lens 7 is made of polystyrene with one external refracting surface.

An example of the implementation of a single-antenna meter polarization matrix

Generator 1 operates at a wavelength of 3.2 cm, its power is 2 watts, the stability of the carrier frequency is one ten millionth, which remains for 30 minutes. The diameter of the circular waveguide of the polarizer is 23 mm. The cross section of the main arm of the NRP 3 is square 20 × 20 mm, the lateral E and H shoulders are made on a rectangular waveguide with a cross section of 23 × 10 mm. The opening of the irradiator is 6.4 cm. The lens is made of PS-1 foam with one external refracting surface, the diameter of the lens is 150 cm and the focal length is 200 cm. Complex variable loads are made on a rectangular waveguide 23 × 10 mm with the possibility of changing the amplitude by 20 times and 2π phase of the reflected microwave signal. Loads provide 60 dB compensation for third-party object signals. In the aperture of the lens, a uniform distribution is ensured within 50 × 50 cm: amplitudes with an accuracy of 1 dB and phases - π / 8.

The technical result of the invention is achieved. For a given field size of 50 × 50 cm with uniform amplitude and phase distributions, the area under the meter is reduced by half, its potential and the dynamic range of measurements are increased by 8 dB.

Claims (1)

A single-antenna polarization matrix meter comprising a transmitter, a polarizer, a directional polarization separator with orthogonal E and H side arms, two complex variable loads, two ampliphase meters and a transceiver antenna, the output of the transmitter being connected to the inputs of the reference signals of the amplifiers and to the input of the polarizer, the output of which is connected to the input of the main arm of the directional polarization separator, in addition, the output of the polarization separator is connected to the input of the transceiver antenna, and the aligned outputs E and H of the lateral arms of the polarization separator are connected with variable loads, the directional outputs E and H of the lateral arms of the polarization separator are connected to the signal inputs of the corresponding amplifiers, characterized in that the transceiver antenna is made of a lens and the lens is made with one external refracting surface.

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