RU2038608C1 - Radar indicator of elevation of air targets - Google Patents

Abstract

FIELD: radiolocation. SUBSTANCE: radar indicator of elevation of air targets has receiving-transmitting antenna system including parabolic reflector 1, vertical 2 and horizontal 3 symmetric vibrators of excitation source, metal counter reflector 4, antenna switch 5, pulse transmitter 6, receivers 7 and 8 of signals of vertical and horizontal polarization accordingly, phase meter 9 and calculator 10. EFFECT: increased operational stability and authenticity. 2 dwg

Description

 The invention relates to radar and can be used in ground-based radars for various purposes for measuring elevation angles of air targets in the entire elevated sector of positive elevation angles.

 Known goniometric device of a radar station [1] containing three spaced apart antennas associated with three channels of receiving signals, a device for measuring phase shifts of received signals and an operation unit with a memory device that determines the direction to the target from the measured phase shifts.

 The disadvantage of this device is that the antenna system consists of three antennas spaced apart in height and is therefore bulky and has a large vertical size.

 Also known radar with a swinging radiation pattern of the antenna [2] containing a transceiver antenna having a narrow radiation angle. Such a radar measures the elevation angle of the target by continuous mechanical swing (rotation) of the antenna in the vertical plane of the target.

 The disadvantage of this radar is that the antenna should have a narrow radiation pattern in the vertical plane and, therefore, the vertical aperture size is large compared to the wavelength. In addition, you need to swing this bulky antenna in elevation.

Closest to the invention is a monopulse phase direction finding radar system [2] used, for example, for measuring elevation and tracking targets in a vertical plane, the receiving part of which contains two identical antennas spaced apart in height, receiving radio waves of the same (for example, vertical) polarization, two receivers respectively associated with these antennas, the phase shifter 90 ^on one of the receive channels, a phase detector, detecting the output voltages of the receivers, and a motor with a reducer and amplifier of the error signal, controlled by the output voltage of the phase detector and rotating the antenna system in elevation. Two identical prototype receivers convert the received signals to an intermediate frequency using mixers and a common local oscillator, amplify the signals in the intermediate frequency amplifiers and limit them in amplitude with the help of limiters. Information about the elevation angle of the target is contained in the phases of the received signals. When the axis of the antenna system coincides with the direction to the target, the error signal at the output of the phase detector is
zero and the electric motor does not rotate the antenna system. When the target deviates in elevation from the direction of the antenna axis, a mismatch signal appears that causes the motor and antennas to rotate in elevation until the axis of the antenna system coincides with the direction to the target. In this case, the elevation angle of the target is determined by the current elevation position of the antenna system. The prototype also includes a pulse transmitter with a transmitting antenna. As a transmitting antenna, you can use the receiving antenna system, switching it from transmission to reception using the antenna switch.

 The disadvantages of this radar system are the ambiguity of determining the elevation angle of the target, to eliminate which use antennas with narrow radiation patterns, which leads to a significant increase in the vertical size of the aperture of the antenna, as well as the presence of an electric drive for rotating the antennas in elevation. In addition, when working in the sector of small elevation angles, reflected from the ground echoes of the target interfere with the operation of the device and reduce the accuracy of measuring the elevation angle.

 The technical objectives of the invention are to eliminate the ambiguity of determining the elevation angle of the target in the entire elevational sector of positive elevation angles, to eliminate the complex operation of rotating the antenna system in elevation, and also to eliminate the harmful effects of target echoes reflected from the ground on the accuracy of elevation measurement by using the device only these signals to achieve a positive effect.

-
2arg

Δφ 0, (1) где λ длина волны;
ε σ относительная диэлектрическая проницаемость и проводимость земной поверхности вблизи антенны соответственно;
arg обозначение операции вычисления аргумента комплексного числа.To do this, in a radar meter for elevation of aerial targets, containing a transceiver antenna system that emits and receives linearly polarized radio waves, a pulse transmitter, two receivers and an antenna switch that connects the antenna system to the transmitter during transmission and to the respective receivers when receiving target echoes, antenna the system is made in the form of one mirror antenna with an irradiator from two mutually perpendicular symmetric vibrators located at the focus of the parabolic mirror a common metal counterreflector, and the axis of the antenna’s parabolic mirror is tilted down half the elevation angle of the antenna radiation pattern to zeros, the vertical vibrator of the irradiator is connected through the antenna switch to the receiver of vertical polarization signals, and the horizontal vibrator to the receiver of horizontal polarization, the device is additionally included a phase meter that measures the phase shift Δ φ of the received signals, and a special calculator that determines the elevation angle of the target θ put from this phase shift We are solving the following transcendental equation:
2arg

-
2arg

Δφ 0, (1) where λ is the wavelength;
ε σ the relative dielectric constant and conductivity of the earth's surface near the antenna, respectively;
arg designates the operation of computing the argument of a complex number.

In this case, the antenna is not rotated in elevation and the phase shifter of 90 ^° , a phase detector and an antenna rotation motor in elevation with a gearbox and an error signal amplifier are eliminated from the prototype. It is also believed that the electrical parameters (ε and σ) of the earth's surface included in equation (1) at a site near the antenna are known or previously measured in any known manner.

 In FIG. 1 shows a simplified structural diagram of the proposed device, as well as the design of the antenna, its radiation pattern and the beam of the radio wave reflected from the ground; in FIG. 2, the calculated dependence of the phase shift Δ φ of the received signals on the elevation angle of the target θ.

,

сигналов вертикальной и горизонтальной поляризации на выходах приемников 7 и 8 по промежуточной частоте, и спецвычислитель 10, определяющий угол места цели θ по измеренному сдвигу фаз Δ φ путем решения трансцендентного уравнения (1) в секторе положительных углов места.The radar meter for elevation of air targets contains a metal parabolic mirror 1 of the transceiver antenna, vertical 2 and horizontal 3 symmetric vibrators of the irradiator, a common metal counterreflector 4 of the irradiator, an antenna switch 5, which connects both vibrators 2 and 3 in parallel to the pulse transmitter when transmitting, and when receiving a vibrator 2 to the receiver 7 of the vertical polarization signal and a vibrator 3 to the receiver 8 of the horizontal polarization, a phase meter 9, measuring the phase shift Δ φ voltage

,

vertical and horizontal polarization signals at the outputs of receivers 7 and 8 at an intermediate frequency, and a special calculator 10 that determines the target elevation angle θ from the measured phase shift Δφ by solving transcendental equation (1) in the sector of positive elevation angles.

 The principle of operation of the proposed device is illustrated as follows. The axis of the device’s mirror antenna is tilted down by half the elevation angle of the antenna radiation pattern to zeros, so the antenna practically emits and receives only vertical and horizontal polarized waves reflected from the ground, and the device almost does not radiate direct antenna-target and target-antenna waves and does not accept.

,

сигналов вертикальной и горизонтальной поляризации на выходах приемников 7 и 8 определяются следующими формулами:

F $\genfrac{}{}{0ex}{}{\text{2}}{\text{в}}$ (θ_o-θ)

×
× K

(2) на выходе приемника вертикальной поляризации 7 и

F $\genfrac{}{}{0ex}{}{\text{2}}{\text{г}}$ (θ_o-θ)

×
× K

(3) на выходе приемника горизонтальной поляризации 8, где

,

комплексные коэффициенты усиления приемников 7 и 8;
λ длина волны;
G_мв, G_мг максимальные коэффициенты усиления зеркальной антенны для вертикально и горизонтально поляризованных радиоволн;
r наклонная дальность по углу отраженной от земли волны между антенной и целью;
P мощность передатчика;
R_пв, R_пг входные сопротивления приемников 7 и 8;
σ_цв, σ_цг эффективные отражающие поверхности цели для радиоволн вертикальной и горизонтальной поляризации;
θ угол места цели;
θ_о угол наклона вниз оси зеркала антенны (положительный);
F_в(θ_o-θ), F_г(θ_o-θ) нормированные диаграммы направленности зеркальной антенны в вертикальной плоскости для вертикально и горизонтально поляризованных радиоволн;
φ_ов, φ_ог изменение фаз радиоволн вертикальной и горизонтальной поляризации при отражении от цели;
К_ш коэффициент шероховатости, учитывающий ослабление интенсивности волны из-за рассеяния на мелкомасштабных неровностях земли (вещественный и не зависит от поляризации);
ε σ относительная диэлектрическая проницаемость и проводимость земной поверхности.Receivers 7 and 8 as well as in the prototype, have the same phase characteristics. Given these observations, complex stress amplitudes

,

the signals of vertical and horizontal polarization at the outputs of the receivers 7 and 8 are determined by the following formulas:

F $\genfrac{}{}{0ex}{}{\text{2}}{\text{in}}$ (θ _o -θ)

×
× K

(2) at the output of the vertical polarization receiver 7, and

F $\genfrac{}{}{0ex}{}{\text{2}}{\text{g}}$ (θ _o -θ)

×
× K

(3) at the output of the horizontal polarization receiver 8, where

,

complex gain of receivers 7 and 8;
λ wavelength;
G _mv , G _mg maximum gains of the mirror antenna for vertically and horizontally polarized radio waves;
r slant range in the angle of the wave reflected from the ground between the antenna and the target;
P transmitter power;
R _pv , R _pg input impedance of receivers 7 and 8;
σ _tsv , σ _{tsg are the} effective reflective surfaces of the target for radio waves of vertical and horizontal polarization;
θ target elevation angle;
θ _{about the} angle of inclination down the axis of the antenna mirror (positive);
F _in (θ _o -θ), F _g (θ _o -θ) normalized radiation patterns of the reflector antenna in the vertical plane for vertically and horizontally polarized radio waves;
φ _s , φ _og change of phases of radio waves of vertical and horizontal polarization upon reflection from the target;
To _w the roughness coefficient, taking into account the attenuation of the wave intensity due to scattering on small-scale irregularities of the earth (material and does not depend on polarization);
ε σ is the relative dielectric constant and conductivity of the earth's surface.

It is known that when vertical and horizontal polarization radio waves are reflected from balloons, warheads, missiles, and other simple-shaped targets with approximately axial symmetry, the changes in the phase of the radio wave φ _s and φ _og will be approximately the same for both polarizations. those. cp _s ≈ φ _lim. The proposed device is intended for measuring elevation angles of such targets.

и

c учетом приведенных выше замечаний, получим трансцендентное уравнение (1) для определения угла места цели θ. Уравнение (1) имеет единственное решение во всем угломестном секторе положительных углов места, что полностью устраняет присущую прототипу неоднозначность определения угла места при любых размерах антенны. Это можно видеть на фиг. 2, где представлена расчетная зависимость сдвига фаз Δ φ от θ угла места цели. Эта зависимость имеет монотонно возрастающий характер, что гарантирует единственность решения трансцендентного уравнения (1) и однозначное определение угла места. Этот график рассчитан по формуле (1) для длины волны λ 0,35 м над морем.Calculating from formulas (2) and (3) the phase shift of the stresses

and

taking into account the above remarks, we obtain the transcendental equation (1) to determine the target elevation angle θ. Equation (1) has a unique solution in the entire elevation sector of positive elevation angles, which completely eliminates the inherent ambiguity of determining the elevation angle for any antenna size. This can be seen in FIG. 2, where the calculated dependence of the phase shift Δ φ on θ of the elevation angle of the target is presented. This dependence has a monotonically increasing character, which guarantees the uniqueness of the solution of transcendental equation (1) and an unambiguous determination of the elevation angle. This graph is calculated according to formula (1) for a wavelength of λ 0.35 m above the sea.

 Thus, the proposed device can be practically implemented, and the above distinguishing features are essential and fundamentally necessary for the implementation of the device.

 The above elements of the structural diagram of the proposed device (Fig. 1) are made as follows. The mirror 1 of the antenna is solid metal and made in the form of a notch from a paraboloid of revolution or a parabolic cylinder. The antenna irradiator consists of vertical and horizontal symmetric vibrators 2 and 3 located at the focus of the mirror, and the common counter-reflector 4 is made in the form of a metal disk. The remaining elements of the device are made according to the usual well-known schemes, and as a special calculator 10 you can use a conventional microcomputer.

 Radar meter works as follows.

 The transmitter 6 generates a high-frequency pulse sounding signal, which through the antenna switch 5 enters the vibrators 2 and 3 of the irradiator mirror antenna. The antenna of the device emits and receives vertically and horizontally polarized radio waves only in the lower hemisphere, and in the upper hemisphere the antenna almost does not radiate and does not receive. Radio waves emitted by the antenna are reflected from the earth's surface and reach the target. The echo signal reflected from the target after reflection from the ground is received by the antenna, and direct target-antenna radio waves are hardly received. The received echo signal of vertical polarization through the antenna switch 5 is supplied to the receiver 7, and the echo signal of horizontal polarization to the receiver 8. The phasometer 9 measures the phase shift Δ φ of the received signals, and the calculator 10 determines from this phase shift and the known parameters λ ε and σ elevation angle of the target θ by solving the transcendental equation (1).

 It should be noted that the proposed device can also be used for direction finding of linearly polarized sources of radio emission, the polarization vector of which has vertical and horizontal components.

 Thus, the proposed device can be practically implemented, has significant distinguishing features, completely eliminates the ambiguity of determining the elevation angle of the target in the entire elevated sector of positive angles, allows at least halving the vertical size of the antenna system, ceteris paribus, eliminates the complex operation of rotating the antennas by elevation angle and the harmful effect of target echoes reflected from the ground on the accuracy of elevation measurement, while using only these signals in order to reach Izhzii positive effect.

Claims (1)

RADAR ANGLE TARGET MEASUREMENT, comprising a transceiver antenna system, a pulse transmitter, two receivers and an antenna antenna switch from transmission to reception, characterized in that the antenna system is made in the form of a mirror antenna with an irradiator of two mutually perpendicular vertical and horizontal symmetrical vibrators with a common counterreflector, and the axis of the parabolic mirror of the antenna is tilted down along the elevation angle by half the elevation radiation pattern at zero, vertically cial vibrator illuminator is connected via a duplexer to receiver vertical polarization signals and the horizontal oscillator with the receiver horizontal polarization signals, and further introduced phase meter for measuring the phase shift of the received signals of vertical and horizontal polarization, and a calculator to determine the angle q purpose place by the formula

where Dv is the phase shift of the received vertical and horizontal polarization signals;
l wavelength;
e, σ are the relative permittivity and conductivity of the earth's surface near the antenna, respectively.

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