RU2490662C2 - Method for radar detection of targets and device for realising said method - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: decision on detection of a signal from a target is made based on signal detection results in the same spatial element in amplitude mode and in moving target selection mode. In a viewing field element, in which the detection threshold is exceeded in amplitude mode, the ratio K_I of signal/noise values is calculated in amplitude mode and in moving target selection mode, which is compared with a threshold value K_P, calculated in advance for boundary radial velocity of the reflecting object, set based on allowable target losses. A signal detection decision is made if K_I>K_P.

EFFECT: high reliability of detecting signals from targets.

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Description

The group of inventions relates to the field of radar and can be used in surveillance radar stations.

There is a known method of radar target detection, in which a probing signal is emitted in each direction of the radar field of view, the received reflected signal is compared with a detection threshold, above which a decision is made to detect the target in the corresponding element of the field of view (Radar Reference. Ed. M. Skolnik, v.1, 1976, p.180, Detector with a fixed sample size).

An element of the field of view is understood as a spatial region whose dimensions in terms of elevation, azimuth, and distance are equal to the dimensions of resolution elements in the corresponding coordinates.

The known device for radar target detection contains a series-connected multiplier, integrator and threshold device (Theoretical Foundations of Radar. Edited by Ya.D.Shirman, 1970, p.102-103). The reference oscillation corresponding to the expected signal and the received signal are supplied to the multiplier. The reference oscillation is generated by a special local oscillator, depending on the set delay time of the reflected signal, proportional to the distance to the target. The signal from the output of the integrator is fed to a threshold device, where it is compared with a detection threshold, which is selected based on the probability of a false alarm. A signal that exceeds a threshold is a target detection signal.

In the known method and device, the decision to detect a target is made based on the results of one sounding, therefore, any received signal that is close in structure to the emitted signal and exceeds the detection threshold is considered a signal from the target. Such signals, in addition to signals from targets, include signals from other reflective objects: the underlying surface, local objects, clouds, clouds of dipole interference, specially created by the enemy to suppress the radar. Thus, along with targets, passive interference is also detected. This is a disadvantage of the known technical solutions.

Closest to the claimed method is a method of radar target detection, including radiation in the radar field of view of the probing signals, receiving signals from reflective objects and comparing them with the detection threshold in the elements of the field of view (amplitude mode), radiation in the radar field of view of the pulses of the SDC system, reception signals from reflecting objects and comparing the signals from the output of the SDS system with the detection threshold in the elements of the field of view (SDS mode), making a decision on the detection of targets in the elements of the field of view (Airspace defense, No. 4 (11) 2003, p. 17, col. 1-2).

The radar target detection device that implements the closest method (Fig. 1) contains a comparison unit with a threshold for detecting amplitude mode 1, an SDC 2 system, a block for comparing with a threshold for detecting SDC 3 mode, a decision block on detecting target 4, and the input to the block comparison with the detection threshold of the amplitude mode 1 and the input of the SDS 2 system are respectively the first and second inputs of the device, the output of the SDS 2 system is connected to the input of the comparison unit with the detection threshold of the SDS 3 mode, the outputs of the comparison block with the threshold ohms for detecting the amplitude mode 1 and the comparison unit with the detection threshold of the SDS 3 mode are connected respectively to the first and second inputs of the decision-making unit for detecting target 4, the output of which is the output of the target radar detection device (Aerospace Defense, No. 4 (11) 2003, p.17, col. 1-2).

The SDC system uses several (usually at least three) pulses emitted at predetermined time intervals. As a result of the subtraction of the received reflected pulses, those that are reflected from stationary and slowly moving objects are suppressed, since they vary little from pulse to pulse. To a lesser extent, pulses from objects moving at high speeds are suppressed. As a result, signals are output to the SDC system, the amplitude of which depends on the speed of the reflecting object.

In the closest technical solutions, the entire radar field of view is examined in the amplitude mode, and part of it in the SDC mode. This is due to the fact that in the SDS mode, several pulses must be emitted in each direction of the field of view, and the time resources of the radar are usually limited. Therefore, the SDS mode is mainly used in areas of the radar field of view, where the greatest amount of passive interference is assumed, for example, in the lower part of the field of view. Thus, where the SDS mode is applied, the elements of the field of view in this mode overlap with the elements of the field of view in the amplitude mode.

For elements of the field of view located in the area of operation of only the amplitude mode, the decision to detect a target is made based on the results of the amplitude mode, and in the area where work is also carried out in the SAC mode, based on the results of detection in the SES mode. In the latter case, the decision to detect the target is made when the detection threshold is exceeded in the SDC mode, regardless of whether the detection threshold is exceeded in the amplitude mode or not.

It is known that in the SDS due to the periodic nature of the amplitude-speed characteristics (ACX) there are losses in the detection of targets (figure 2). This occurs when the target’s speed corresponds to the position of one of the “failures” of the ASX (Theoretical Foundations of Radar. Edited by Shirman Y.D., 1970, p. 479, 481).

In the closest technical solutions, situations are possible in which erroneous decisions are made:

- in the amplitude mode, the detection threshold is exceeded, in the SDS mode it is not exceeded. A decision is made about the absence of a goal, although in reality there is a goal, but it turned out to be in the “failure” of the ACX

- in the amplitude mode and in the SDS mode, the detection thresholds are exceeded. A decision is made to detect the target, although there is passive interference, the level of which exceeds the capabilities of the SDS system to suppress interference.

Thus, a drawback of the closest technical solutions is the low reliability of target detection.

The invention is aimed at eliminating this drawback.

The problem being solved (technical result), thus, is to increase the reliability of target detection.

The specified technical result is achieved by the fact that in the method of radar detection of targets, including radiation in the radar field of view of the probing signals, receiving signals from reflecting objects and comparing them with the detection threshold in the elements of the field of view (amplitude mode), radiation in the radar field of view of the pulses of the SDC system , receiving signals from reflective objects and comparing signals from the output of the SDS system with a detection threshold in the elements of the field of view (SDS mode), making a decision on the detection of targets in the elements of the field of view in which in the SDC mode, the detection threshold is exceeded, and in the amplitude mode is not exceeded, according to the invention, in each element of the field of view in which the detection threshold is exceeded in the amplitude mode, the ratio is calculated:

$${\text{K}}_{\text{AND}}=\frac{{\text{A}}_{\text{SDC}}}{{\text{A}}_{\text{AMP}}}\text{,}\left(\text{one}\right)$$

where A _SDC and A _AMP are the ratios of the amplitudes of the received signals in the SDC mode and in the amplitude mode to the rms noise value, respectively;

the ratio K _{И is} compared with the threshold value K _П , pre-calculated for the boundary radial velocity of the reflecting object V _{r gr} , set on the basis of allowable losses for targets, when the condition K _И > K _П is fulfilled, a decision is made to detect the target.

The specified technical result is also achieved by the fact that as the SDC system, a three-pulse time-time difference system of the SDC is used, for which the threshold value K _{P is} calculated in accordance with the formula:

$${\text{K}}_{\text{P}}=\text{258}{\left(\frac{{\text{V}}_{\text{r}gR}}{\text{λ}\left({\text{T}}_{\text{one}}+{\text{T}}_{\text{2}}\right)}\right)}^{\text{2}}\frac{{\text{G}}_{\text{SDC}}}{{\text{G}}_{\text{AMP}}}\sqrt{\frac{{\text{τ}}_{\text{AND}}{}_{\text{SDC}}{\text{δ}}_{\text{SDC}}}{{\text{τ}}_{\text{AND}\text{AMP}}{\text{δ}}_{\text{AMP}}}}\text{,}\left(\text{2}\right)$$

where λ is the wavelength of the signals emitted by the radar;

T ₁ and T ₂ are the time intervals between the emissions of the first and second, second and third pulses of the SDC mode, respectively;

V _{r gr} is the boundary radial velocity of the reflecting object, above which the object is considered to be the target, is set based on the allowable losses for targets having radial velocities, the values of which are in the vicinity of non-zero “dips” in the amplitude-velocity characteristics of the SDC;

G _SDC and G _AMP - radar antenna gain in the SDC mode and in the amplitude mode, respectively;

τ _{And SDC} and τ _{And AMP} - the pulse duration in the SDC mode and the duration of the probe signal in the amplitude mode, respectively;

δ _SDC and δ _AMP are the signal loss values in the SDC mode and in the amplitude mode, respectively.

The specified technical result is also achieved by the fact that the radial boundary velocity V _{r gr is} set in accordance with the formula:

$${\text{V}}_{\text{r}\text{gr}}=\frac{\text{λ}}{{\text{T}}_{\text{one}}+{\text{T}}_{\text{2}}}\sqrt{\text{k}\frac{\left|{\text{T}}_{\text{one}}-{\text{<figure-callout id="2" label="T" filenames="00000008.png,00000010.png" state="{{state}}">T</figure-callout>}}_{\text{2}}\right|}{\text{π}\left({\text{T}}_{\text{one}}+{\text{T}}_{\text{2}}\right)}}\text{,}\left(\text{3}\right)$$

where k is the number of non-zero “failure” (k≥1) of the amplitude-speed characteristic of the SDS.

The indicated technical result is also achieved by the fact that in the device for radar target detection containing a comparison unit with a threshold for detecting an amplitude mode, an SDC system, a unit for comparing with a threshold for detecting an SDC mode, a decision block for detecting a target, and the input of a comparison unit with a threshold for detecting an amplitude mode and the input of the SDC system are respectively the first and second inputs of the device, the output of the SDC system is connected to the input of the comparison unit with the detection threshold of the SDC mode, the output of the unit is comparable with the detection threshold of the amplitude mode and the output of the comparison unit with the detection threshold of the SDC mode, respectively, are connected to the first and second inputs of the decision detection unit of the target, intended for detection signals in the amplitude mode and in the SDC mode, respectively, the output of the decision block on detecting the target is the output of the device for radar detection of targets, according to the invention, the input of the comparison unit with the threshold for detecting the amplitude mode and the output of the SDS system are connected respectively about with the third and fourth inputs of the decision-making block on target detection, intended for the received signals of the amplitude mode and signals from the output of the SDC, respectively.

The essence of the claimed technical solutions is as follows.

The claimed technical solutions, as in the prototype, work in the field of view, where the detection is carried out jointly in the amplitude mode and in the SDC mode.

The elements of the view area, which in the amplitude mode, the detection threshold is exceeded, the detection decision target is made based on the analysis of the ratio of the signal / noise A _MTI output MTI in SBC mode to the value of the signal / noise ratio A _ILA in the amplitude mode in accordance with the formula ( one). It doesn’t matter if the detection threshold is exceeded in SDS mode or not.

The specified analysis is based on the following.

The position of the minima (“dips”) and maxima (“peaks”) of the ACX is unambiguously related to the type of SDC, the number and parameters of pulses, their repetition periods (Fig. 2 shows an example of a three-pulse difference-time SDC normalized to a single pulse of ACC ACX). The “failures” and “peaks” of the ASX are usually numbered. In the description, “dips” are numbered with integers starting from zero. Zero “failure” corresponds to zero speed.

As a sign by which a reflecting object is taken as a target or as a passive interference, its radial speed is used. If the radial speed of the object exceeds a pre-selected boundary radial speed V _{r gr} , then the object is considered the target, otherwise - passive interference. The boundary radial velocity V _{r gr} is selected on the basis of allowable losses for targets in accordance with formula (3).

When deciding on the detection of a target moving relative to the radar, the radial velocity of the object is not used (which, for example, is not known with a regular review of the zone), but the ratio K _{And the} signal-to-noise ratio A of the _SDC at the output of the SDC SDS to the signal-to-noise A _AMP in the amplitude mode (1). The indicated ratio depends on the radial velocity of the target and does not depend on many unknown parameters of the target and radar, for example, such as the effective scattering surface of the target and the level of antenna gain in the direction to the target.

The ratio K _{AND is} compared with the threshold value K _P (2), pre-calculated for the selected boundary radial velocity of the reflecting object V _{r gr} . When deriving formula (2), the equality of pulsed powers of the signals radiated in the amplitude mode and in the SDC mode, which is being implemented in practice, was taken into account.

When the conditions K _And > K _P are fulfilled, a decision is made to detect a target in a given element of the field of view.

The value of the boundary radial velocity V _{r gr is} counted in the ACX area of the SDC from zero speed to its first "peak" (figure 2). In this case, the value of V _{r gr is} taken at a point in this ACX region, corresponding to the normalized amplitude of the selected non-zero ACX “dip”. It is preferable to specify the boundary radial velocity V _{r g} based on the normalized amplitude of the first (k = 1) ACX “dip” (dependent claim 3 of the invention), since in this case the value of the velocity V _{r gp} relative to other _ACX “dips” is the smallest and losses in detecting targets with speeds corresponding to other “failures”, no.

Thus, the decision to detect the signal from the target when using the amplitude mode and the SDS mode together allows to increase the reliability of detection of signals from the targets, that is, the claimed technical result is achieved.

The invention is illustrated by the following drawings.

Figure 1 is a functional diagram of a device for radar target detection that implements the closest method.

Figure 2 is an example of the amplitude-velocity characteristics of the three-pulse time-difference system of the SDC, normalized to the amplitude of one pulse of the SDC.

Figure 3 is a functional diagram of a device for radar target detection that implements the inventive method.

A radar target detection device that implements the inventive method (Fig. 3) comprises a comparison unit with a threshold for detecting an amplitude mode, an SDC system, a block for comparing with a threshold for detecting an SDC mode, a decision block for detecting a target, and an input for a comparison block with a threshold for detecting an amplitude mode and the input of the SDC system are respectively the first and second inputs of the device, the output of the SDC system is connected to the input of the comparison unit with the detection threshold of the SDC mode, the output of the comparison unit with the detection threshold the amplitude mode and the output of the comparison unit with the detection threshold of the SDC mode are connected respectively to the first and second inputs of the decision block on detecting the target, the input of the comparison unit with the detection threshold of the amplitude mode and the output of the SDC system are connected respectively to the third and fourth inputs of the decision detection block the output of which is the output of a radar target detection device.

A device for radar target detection can be performed using the following functional elements.

The comparison unit with the detection threshold of the amplitude mode 1 is made on standard microcircuits (Integrated microcircuits. Handbook edited by T.V. Tarabrina, 1984). In the block, the amplitude of the signal received in the amplitude mode is compared with the detection threshold of the amplitude mode. A single signal is output from the output of block 1, if the received signal exceeds a threshold level, a signal is not issued if the detection threshold is not exceeded.

SDC 2 system - a three-pulse time-difference time-difference system of SDC, can be implemented on two shifting delay lines, a compensating delay line and an adder (Radar Reference. Ed. M. Skolnik, 1979, v. 3, p. 319-320).

Signal processing in the three-pulse difference-time SDS system is carried out in accordance with the formula:

$$\text{u}=\left({\text{u}}_{\text{one}}-{\text{u}}_{\text{2}}\right)-\left({\text{u}}_{\text{2}}-{\text{u}}_{\text{3}}\right)\text{,}\left(\text{four}\right)$$

where u is the signal at the output of the SDC system,

u ₁ , u ₂ , u ₃ , are the amplitudes of the 1st, 2nd, and 3rd received pulses, respectively.

The comparison unit with the detection threshold of the SDC 3 mode is made on standard microcircuits (Integrated microcircuits. Handbook edited by T.V. Tarabrina, 1984). The block compares the amplitude of the signal from the output of the SDS 2 system with a detection threshold. A single signal is output from the output of block 3, if the received signal exceeds a threshold level, a signal is not issued if the detection threshold is not exceeded.

The decision making unit for detecting target 4 is a computer (Integrated circuits. Reference edited by T.V. Tarabrina, 1984), which implements calculations by formulas (1), (2), (3) and verifies the condition for detecting targets K _AND > K _p . The threshold value K _{P is} calculated in advance for the boundary radial velocity of the reflecting object V _{r gr} , specified on the basis of allowable losses for targets, and is stored in block 4. The inventive device for radar target detection works as follows.

The probing signals of the amplitude mode are emitted in the directions of the radar field of view. In the directions of the field of view in which the SDC mode is applied, after the radiation of the probing signal of the amplitude mode, the pulses of the SDC mode are emitted. In the comparison unit with the detection threshold of the amplitude mode 1, the received signals of the amplitude mode are compared with the detection threshold of the amplitude mode set in accordance with a predetermined level of false alarms. In the SDS 2 system, the processing of received pulses is carried out according to the formula (4). Signals that depend on the radial speed of the reflecting object from the output of SDC 2 are fed to the input of the comparison unit with the detection threshold of the SDC 3 mode, where they are compared with the detection threshold of the SDC mode, set on the basis of a given level of false alarms. If the signals received in the comparison blocks 1 and 3 exceed the corresponding detection thresholds, then the standard unit signals are formed at the outputs of these blocks - signs of exceeding the thresholds, which are supplied respectively to the first and second inputs of the decision-making block on target detection 4. Accepted in the amplitude mode the signals and signals from the output of the SDS 2 system are supplied, respectively, to the third and fourth inputs of the decision block on detecting target 4. In this block, a decision is made to detect the target in the element of the field of view. In this case, a signal about target detection is issued in two cases:

- from the input of the comparison unit with the detection threshold of the SDC 3 mode, a signal was received about the detection threshold being exceeded in the SDC mode, and there is no signal from the output of the comparison unit with the detection threshold of the amplitude mode 1 about the excess of the detection threshold in the amplitude mode;

- from the output of the comparison unit with the detection threshold of the amplitude mode 1, a signal was received that the detection threshold was exceeded and the ratio Kc calculated in block 4 in accordance with formula (1) using the signals received in the block 4 received in the amplitude mode and from the output СДЦ, satisfies the condition K _И > K _П.

The threshold value K _{P is} calculated in advance by the formula (2) based on the boundary radial velocity of the reflecting object V _{r gr} , set in accordance with expression (3), and is constantly stored in block 4.

Thus, the claimed technical result is achieved.

Claims (4)

1. The method of radar detection of targets, including the radiation in the field of view of the radar station (radar) of probing signals, the reception of signals from reflecting objects and comparing them with the detection threshold in the elements of the field of view (amplitude mode), the radiation in the field of view of the radar of pulses of the target selection system of moving targets (SDC), receiving signals from reflective objects and comparing signals from the output of the SDC system with a detection threshold in the elements of the field of view (SDC mode), deciding on the detection of targets in the elements of the field of view in which in the SDC mode, the detection threshold is exceeded, but in the amplitude mode it is not exceeded, characterized in that in each viewing element in which the amplitude mode and the SDC mode are shared and in which the detection threshold is exceeded in the amplitude mode, the ratio is calculated
$$K_{\mathrm{and}}=\frac{{\mathrm{BUT}}_{\mathrm{from}dc}}{{\mathrm{BUT}}_{\mathrm{but}mP}},$$

where A _SDC and A _dmp are the ratios of the amplitudes of the received signals in the SDC mode and in the amplitude mode to the rms noise value, respectively;
ratio K _and compare with a threshold value of K _p pre-calculated for the boundary radial velocity of the reflecting object V _{r gr} , set on the basis of allowable losses on targets, when the conditions K _and > K _p are fulfilled, they decide to detect the target. 2. The method according to claim 1, characterized in that the three-pulse time-difference system of the SDC is used as the SDC system, for which the threshold value K _{p is} calculated in accordance with the formula
$${\text{K}}_{\text{P}}=\text{258}{\left(\frac{{\text{V}}_{\text{r}gR}}{\text{λ /}\left({\text{T}}_{\text{one}}+{\text{T}}_{\text{2}}\right)}\right)}^{\text{2}}\frac{{\text{G}}_{\text{sdc}}}{{\text{G}}_{\text{amp}}}\sqrt{\frac{{\text{τ}}_{\text{and}}{}_{\text{sdc}}{\text{δ}}_{\text{sdc}}}{{\text{τ}}_{\text{and}\text{amp}}{\text{δ}}_{\text{amp}}}},$$

where λ is the wavelength of the signals emitted by the radar;
T ₁ and T ₂ are the time intervals between the emissions of the first and second, second and third pulses of the SDC mode, respectively;
V _{r gr} is the boundary radial speed of the reflecting object, above which the object is considered to be the target, is set based on the allowable losses for targets having radial velocities, the values of which are in the vicinity of non-zero “dips” in the amplitude-velocity characteristics of the SDC;
G _SDC and G _amp are the radar antenna gain in the SDC mode and in the amplitude mode, respectively;
τ _{and SDC} and τ _{and amp} are the pulse durations in the SDC mode and the duration of the probe signal in the amplitude mode, respectively;
δ _SDC and δ _amp are the signal loss values in the SDC mode and in the amplitude mode, respectively. 3. The method according to claim 2, characterized in that the radial boundary velocity V _{r gr} set in accordance with the formula
$${\text{V}}_{\text{r}\text{rp}}=\frac{\text{λ}}{{\text{T}}_{\text{one}}+{\text{T}}_{\text{2}}}\sqrt{\text{k}\frac{\left|{\text{T}}_{\text{one}}-{\text{T}}_{\text{2}}\right|}{\text{π}\left({\text{T}}_{\text{one}}+{\text{T}}_{\text{2}}\right)}}$$

,
where k is the number of non-zero “failure” (k≥l) of the amplitude-speed characteristic of the SDS. 4. A device for radar target detection, comprising a unit for comparison with a threshold for detecting an amplitude mode, an SDC system, a unit for comparing with a threshold for detecting an SDC mode, a block for making a decision on detecting a target, while the input of a unit for comparing with a threshold for detecting an amplitude mode and an input for the SDC system are respectively the first and second inputs of the device, the output of the SDC system is connected to the input of the comparison unit with the detection threshold of the SDC mode, the output of the comparison unit with the detection threshold of the amplitude mode and the output of the unit with equalities with the detection threshold of the SDC mode are connected respectively to the first and second inputs of the target detection decision block intended for detection signals in the amplitude mode and in the SDC mode, respectively, the output of the target detection decision block is the output of the radar target detection device, characterized in that the input of the comparison unit with the threshold for detecting the amplitude mode and the output of the SDC system are connected, respectively, with the third and fourth inputs of the decision-making unit on updating Weapons intended for the received signals of the amplitude mode and signals from the output of the SDC, respectively, the decision to detect the target is made if the output of the comparison unit with the detection threshold of the SDC mode receives a signal that the detection threshold is exceeded in the SDC mode and there is no signal from the output of the comparison unit with the detection threshold of the amplitude mode about exceeding the detection threshold in the amplitude mode; the decision to detect the target is also made if the output of the comparison unit with the threshold for detecting the amplitude mode _{sends a} signal to the decision block on detecting the target that the detection threshold is exceeded and the ratio K _and = A _SDC / A _amp satisfies the condition K _and > K _p , where A _SDC and A _amp are the ratios of the amplitudes of the received signals in the SDC and in the amplitude mode to the rms noise value, respectively, K _p is the pre-calculated threshold value for the boundary radial velocity of the reflecting object, specified based on allowable losses on goals.

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