RU2508559C2 - Method of scanning space with radar station - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: in the disclosed method of scanning space with a radar station with successive movement of the beam in columns on the elevation angle and two-step detection of a signal from a target, the beam in a column is moved in a zigzag manner via two-dimensional electronic scanning; in each beam position, a probing signal is emitted; the received reflected signal is compared with thresholds of the first and second detection steps; a target in the current beam position in discrete values of range where the threshold of the second detection step has been exceeded is considered detected if, in at least one of two neighbouring beam positions in the column scanned at previous moments in time, in discrete range values selected based on range measurement error and possible movement of the target during the time between the steps, the threshold of the first detection step is exceeded.

EFFECT: reducing time and power costs when scanning space with a radar station in conditions with a large number of targets and noise in many beam positions.

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Description

The invention relates to the field of radar and can be used in survey radar stations (RLS) with two-dimensional electronic scanning and mechanical rotation of the antenna in azimuth when viewing the space by sequential movement of the beam.

A known method of viewing space by a radar station with sequential column movement of the beam along the elevation angle with a given step using electronic scanning, and in azimuth due to the mechanical rotation of the antenna, in which a probe signal is emitted at each position of the beam, which is then reflected in the same position of the beam the signal in each discrete in range is compared with a detection threshold, above which a decision is made to detect a target (Radar Reference. Edited by M. Skolnik, Volume 1. - M., 1 976, p. 180, 1st paragraph).

The disadvantage of this method is the significant time and energy costs during the review. This is because the energy of the probe signal emitted in each position of the beam of the field of view is determined based on the required (usually high enough) probability of target detection at a given (usually low enough) probability of false alarm. And since the targets, as a rule, are far from each beam position, a significant part of the radar’s time (energy) is spent in positions where there are no targets.

The total time spent on a review in a known manner is determined from the expression:

$$T_{\Sigma \mathrm{and}\mathrm{from}}=n_0\times N_l\times \Delta t_s,\left(\mathrm{one}\right)$$

where n ₀ is the number of pulses that is emitted in each position of the beam of the field of view to detect the target with the required probability;

N _l - the number of beam positions in the radar field of view;

Δt _z - the duration of the probe pulse period.

Closest to the claimed one is a way to view the space of a radar station with sequential column movement of the beam using electronic scanning in azimuth and mechanical rotation in azimuth and two-stage detection of the signal from the target. The method is as follows.

When viewing the space in each position of the beam, a probe signal of the first detection stage is emitted, a reflected signal is received, and in all discrete samples in range the received signal is compared with the threshold of the first detection stage. If the detection threshold exceeded the detection threshold at least in one discrete range, the second probing signal (the signal of the second detection stage) is emitted at the same position of the beam, the reflected signal is also received in range discrete corresponding to the discrete in which the excess threshold of the first detection stage, compare it with the threshold of the second detection stage. The selection of the discrete by range, in which the received signal is compared with the threshold of the second detection stage, is carried out taking into account the errors of measuring the range and the possible movement of the target during the time between the moments of radiation of the probing signals at the detection stages (Radar Reference. Edited by M. Skolnik, vol. 1. - M, 1976, p.200).

In the closest method, when viewing a space, the beam is sequentially moved by linear columns in elevation with a given step using electronic scanning, and in azimuth, due to the rotation of the antenna. The even / odd columns of the field of view can be offset in elevation relative to the odd / even columns (FIG. 1) or can be offset in elevation (FIG. 2). In the drawings, ellipses with a gray fill and a bold border indicate the beam cross-sections in positions in which a decision is made on two-stage signal detection.

The probe signal of the second detection stage is emitted only at the beam positions where the threshold of the first detection stage is exceeded by the signal received at the first detection stage. This saves energy emitted in the field of view.

The total time spent on a review with two-stage detection in the closest method is determined from the expression:

$$T_{\Sigma nb\mathrm{from}}=(n_{\mathrm{one}}+k\times n_2)\times N_l\times \Delta t_s,\left(2\right)$$

where n ₁ and n ₂ are the number of pulses emitted in the position of the beam of the field of view at the first and second stages of detection, respectively, n ₁ + n ₂ = n ₀ ;

k is the number of second steps.

However, the aforementioned savings occur with a relatively small number of targets and interference in the field of view (with a small value of k).

Under normal (average) target and interference conditions, the number of beam positions in the field of view in which the second detection stage is implemented does not exceed 20% of the number of beam positions in which the threshold of the first detection stage is exceeded (k = 0.2). In this case, the use of two-stage detection is effective because it allows you to save time and energy resources of the radar when viewing the space.

In a complex target and interference environment, when there are many targets and interference in the field of view in many beam positions, the total time spent on the zone survey in the closest method can reach an extremely large value (for k = 1) equal to:

$$T_{\Sigma nb\mathrm{from}}=n_0\times N_l\times \Delta t_s.\left(3\right)$$

In this case, the time spent in the closest method becomes equal to the cost in the known method (1), that is, the application of the closest method is ineffective.

Thus, the disadvantage of the closest method is the increase in time and energy costs when viewing space in a large number of targets and interference in many positions of the beam.

The invention is aimed at eliminating this drawback.

The problem being solved (technical result), therefore, is the reduction of time and energy costs when viewing the space of a radar station under conditions of a large number of targets and interference in many beam positions.

The specified technical result is achieved by the fact that in the method of viewing space by a radar station with electronic scanning by the antenna beam and rotating the antenna in azimuth with sequential column movement of the beam along the elevation angle, two-stage detection of the signal reflected from the target, including the radiation of the probe signal at each beam position in the column , receiving a reflected signal, comparing a received signal in all samples in range with a threshold of a first detection step, comparing a received signal with a threshold the second detection stage and the decision to detect the target when the specified threshold is exceeded, while the selection of the discrete in range, in which the received signal is compared with the threshold of the second detection stage, is made taking into account the errors of measuring the range and the possible movement of the target during the time between the moments of radiation of the probing signals at the detection stages, according to the invention, the beam in the column is moved in a zigzag manner using two-dimensional electronic scanning, while the beam is moved along the elevation angle with a constant m or in a variable step, not exceeding the beam width in elevation at half power, each movement of the beam in azimuth in the column, in addition to the first movement, is carried out in the direction opposite to the previous one, the first in the column moves the beam in azimuth in the direction coinciding with the direction of rotation of the antenna , while the beam in azimuth in the column is moved in increments not exceeding half the width of the beam in azimuth at half power, comparing the signal received at the position of the beam in the column at the moment An instance of time with a threshold of the second detection stage is carried out in the aforementioned distance samples in which at least one of two adjacent beam positions in the column examined at previous time instants exceeded the threshold of the first detection stage.

The essence of the claimed technical solution is that when two-stage detection of a signal reflected from the target in the current position of the beam in the column uses signals received at previous points in time in the nearest neighboring positions of the beam in this column.

The possibility of such a technical solution is based on the following two premises.

Firstly, it is known that, closer to a certain range, the signals reflected from the target, due to the overlap of the antenna pattern during the successive movement of the beam, are detected in several neighboring beam positions, that is, an angular packet (packet) of detected signals is formed on the target (Kuzmin S.Z. Fundamentals of the theory of digital processing of radar information. - M., 1974, p. 43-45). The presence of an angular packet of signals reflected from the target allows combining target detection at the detection stages with an overview of the space and thereby saving the radar’s time and energy resources.

Secondly, it is known that the signals emitted at the first and second stages of two-stage detection, as well as the number of pulses emitted at the stages (n ₁ and n ₂ ) without significant damage to optimality, can be assumed to be the same (Radar Reference. Ed. M Skolnik, Volume 1. - M., 1976, p. 201). This allows you to use the same signal at both stages of detection.

In the claimed invention, a review of the space is carried out in a zigzag sequential movement of the beam in the column using two-dimensional electronic scanning (Fig.3 and Fig.4, the column viewing order is indicated by dashed arrows) and mechanical rotation of the antenna. Such a column is inspected in one pass instead of two columns of the closest method inspected in two passes. At the same time, it becomes possible to form angular packets in the column according to signals from the target, received at minimum time intervals, at both coordinates and to use them sequentially in two-stage detection.

Comparison of the signal received at the beam position in the column at a given time with the threshold of the second detection stage is carried out in range discretes corresponding to those in which at least one of the two adjacent beam positions at previous time instants exceeded the threshold of the first detection stage. The selection of the mentioned discrete in range is made taking into account the errors of measuring the range and the possible movement of the target during the time between the moments of radiation of the probing signals at the detection stages.

In figure 3 and figure 4, ellipses with a gray fill and a bold border indicate the beam cross-sections in positions in which a decision is made on two-stage signal detection. In each such case, the first detection step is to exceed the threshold of the first detection step in one of two adjacent beam positions, indicated by a gray fill and a thin border.

At each position of the beam in the column, except for the first position (the first position of the beam in the column can be the lowest or highest upper position of the beam, depending on the viewing order of the column), the first and second detection steps can be implemented. The study of the signal of the first detection stage, by analogy with the prototype, is carried out in all positions of the beam of the field of view.

The second detection stage is realized in the beam position of the column at a given time only if the received signal exceeded the threshold of the second detection stage in any discrete in range in this beam position, and in one of two adjacent beam positions in the same range occurred exceeding the detection threshold of the first detection stage. Since the same signals are used at both stages of detection and no special signals are emitted for the second stage, the time (energy) spent on viewing the zone remains constant regardless of the interference environment.

Since for the method to work, it is necessary that the target is detected in at least two adjacent positions of the beam (i.e., an angular packet should be formed by the reflected signal), the step of moving the beam in the column should be sufficiently small: it should not exceed half the beam width in level half power of at least one of the angular coordinates. Typically, the radar field of view according to elevation is rigidly defined, so it is most advisable to set a small beam pitch in azimuth. Thus, the step of moving the beam in the column along the elevation angle should not exceed the beam width in elevation, and in azimuth - the beam width in azimuth at half power level.

The total time spent in the claimed method is determined from the expression:

$$T_{\Sigma s\mathrm{from}}=n_{\mathrm{one}}\times N_l\times \Delta t_s.\left(\mathrm{four}\right)$$

The value of the gain in time costs in the claimed method relative to the closest method follows from the expressions (2) and (4), taking into account the fact that n ₂ = n ₁ , in the form:

$$\frac{T_{\Sigma nb\mathrm{from}}}{T_{\Sigma s\mathrm{from}}}=\mathrm{one}+k.\left(5\right)$$

In expression (5), the value l + k is greater than unity for any value of k> 0, which means that the time costs in the inventive method in any target and interference environment are always less than the time costs in the closest method.

It is important to note that the effectiveness of the proposed method, that is, the gain in time and energy costs, increases with increasing tension of the target and interference conditions (that is, with an increase in k).

Thus, the claimed technical result is achieved.

The invention is illustrated by the following drawings:

Figure 1 is an overview of the zone in the closest method when adjacent columns are offset in elevation.

Figure 2 is an overview of the zone in the closest method when adjacent columns are not offset in elevation.

Figure 3 is an overview of the zone in the claimed method, the beam in the column is moved in a zigzag fashion with a step in elevation equal to 0.5θ _ε , in azimuth - in increments of 0.5θ _β , each movement of the beam in azimuth in the column is carried out in the opposite direction the previous one, where θ _β and θ _ε are the beam widths at the half power level in azimuth and elevation, respectively. Ellipses with a gray fill and a bold border indicate the beam cross-sections at the positions in which a decision is made on two-stage signal detection. In each such case, the first detection step is to exceed the threshold of the first detection step in one of the adjacent beam positions, indicated by a gray fill and a thin border.

4 - Overview zone in the inventive method, the beam is moved in a zigzag in the column with variable pitch elevation (alternating from state to state values of the beam to be zero and θ _ε), in azimuth - a step equal 0.5θ _β, where each the beam is moved in azimuth in the column in the opposite direction to the previous one.

5 is a functional diagram of a radar station that implements the inventive method.

The inventive method can be implemented in a radar (figure 5), containing a transmitter 1, an antenna switch 2, an antenna 3, a beam control device 4, a receiver 5, a threshold device 6, a threshold device 7, a synchronizer 8, a storage device 9, a calculator 10, the input of the transmitter 1 is connected to the first output of the synchronizer 8, the output of the transmitter 1 is connected to the input of the antenna switch 2, the input / output of which is connected to the first input / output of the antenna 3, the second control input of the antenna 3 is connected to the output of the beam control device 4, input which is connected to the second output of the synchronizer 8, the output of the antenna switch 2 is connected to the input of the receiver 5, the output of which is connected to the input of the threshold device 6 and to the input of the threshold device 7, the output of the threshold device 6, the output of the threshold device 7, the coordinate output of the antenna 3 and the third the output of the synchronizer 8 is connected respectively to the first, second, third and fourth inputs of the storage device 9, the output of which is connected to the input of the computer 10, the output of the computer 10 is the output of the radar.

The radar station can be performed using the following functional elements.

Transmitter 1 - pulse type (Reference to the basics of radar technology. - M., 1967, p. 278).

Antenna switch 2 - is made on the circulator (Reference on the basics of radar technology. - M., 1967, p.146-147).

Antenna 3 - phased antenna array with electron beam scanning at both angular coordinates (two-dimensional scanning) and with circular mechanical rotation (Radar Reference. Edited by M. Skolnik, Volume 2. - M, 1977, pp. 132-138).

The beam control device 4 is a computer made on standard microcircuits (Integrated microcircuits. A reference book edited by B.V. Tarabrin. - M., 1984). It implements the function of calculating the position of the beam in space before each radiation of the probe signal.

Receiver 5 - superheterodyne type (Handbook on the basics of radar technology. - M., 1967, S. 343-344).

The threshold device 6, the threshold device 7, the storage device 9 are made on standard microcircuits (Integrated microcircuits. Handbook edited by B.V. Tarabrin. - M., 1984).

Synchronizer 8 is made on the basis of a master oscillator and a chain of frequency dividers connected in series (Radar devices (theory and construction principles). Edited by V.V. Grigorin-Ryabov. - M., 1970, S. 602-603).

The calculator 10 is made on standard microcircuits (Integrated microcircuits. Handbook edited by B.V. Tarabrin. - M., 1984). It implements the function of determining discrete numbers by range in which the detection threshold is exceeded.

The operation of the radar is as follows. In the transmitter 1, according to the commands of the synchronizer 8 (synchronization pulses), probing signals are generated, which are transmitted through the antenna switch 2 to the first input / output of the antenna 3. The position of the antenna 3 beam is determined in the beam control device 4, from the output of which, by the synchronizer 8 command, to the second control the input of the antenna 3 serves the coordinates of the beam (azimuth and elevation angle) in accordance with a given program of the review of space in zigzag columns of beam positions. The reflected signals are received by the antenna 3 and through the antenna switch 2 are fed to the input of the receiver 5.

From the output of the receiver 5, the signals are fed to the input of the threshold device 6 and the input of the threshold device 7, in which the received signals are compared with the thresholds of the first and second stages of detection, respectively. Signals whose level exceeds the threshold pass to the outputs of the threshold devices. The signals from the outputs of the threshold device 6, the threshold device 7 and signals proportional to the coordinates of the beam of the antenna 3, respectively, are supplied to the first, second and third inputs of the storage device 9, where the zones are stored during the review.

By commands from the synchronizer 8 from the storage device 9, the data recorded in them for three consecutive beam positions in the column are retrieved and fed to the calculator 10. In the calculator 10, in these beam positions, a discrete search is performed in which the threshold for the second detection stage is exceeded (taking into account range measurement errors and possible range movement of the target over the time between steps) in the current position of the beam and the threshold of the first detection stage in at least one of the previous neighboring beam positions. For these discretes, a decision is made to detect signals from targets. The coordinates of the detected targets are issued from the output of the calculator 10.

Thus, in the radar that implements the inventive method of two-stage detection of the signal from the target, the claimed technical result is achieved.

Claims (1)

A way to view the space of a radar station with electronic scanning by the antenna beam and rotating the antenna in azimuth with sequential column movement of the beam along the elevation angle, two-stage detection of the signal reflected from the target, including radiation of the probe signal at each position of the beam in the column, receiving the reflected signal, comparing the received signal in all discretes in range with the threshold of the first detection stage, comparing the received signal with the threshold of the second detection stage and making a decision on detection target when exceeding the specified threshold, while the choice of discrete in range, in which the received signal is compared with the threshold of the second detection stage, is made taking into account measurement errors of the range and the possible movement of the target during the time between the moments of radiation of the probing signals at the detection stages, characterized in that the beam in the column is moved in a zigzag manner using two-dimensional electronic scanning, while the beam is moved along the elevation angle with a constant or variable pitch, not exceeding the beam width in angle at the site in terms of half power, each beam moving in azimuth in the column, in addition to the first movement, is carried out in the opposite direction to the previous one, the first in the column moving the beam in azimuth is in the direction coinciding with the direction of rotation of the antenna, while the beam in azimuth is moved in the column with in a step not exceeding half the beam width in azimuth in terms of half power, comparing the signal received at the beam position in the column at a given time with the threshold of the second stage of detection appear in the mentioned discrete samples in range in which the threshold of the first detection stage is exceeded in at least one of the two adjacent beam positions in the column examined at previous time instants.

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