JP2002048859A - Target identification radar device - Google Patents

Abstract

(57) [Problem] To provide a target identification radar apparatus in which the probability of correctly identifying a target is improved even if a plurality of targets have similar range profiles. SOLUTION: Two antennas having polarization characteristics orthogonal to each other, a polarization switch for switching and driving both antennas to collect a scattering matrix of an observation target, and an observation target for observation of multiple polarizations are provided. A target identification unit that performs target identification using a scattering matrix range profile for each resolution cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-resolution target identifying radar apparatus, and more particularly to a case where target range profiles are similar, or where sufficient information on a target aspect angle cannot be obtained in advance. The present invention relates to a target identification radar apparatus with an improved target identification probability.

[0002]

2. Description of the Related Art A conventional apparatus of this type is, for example, Scott
Hudson & Demetri Psaltis, “Correlation Filters for
Aircraft Identification From Radar Range Profile
s, ”IEEE Trans. on Aerospace and Electronic Syst
ems, vol. 29, No. 3, pp. 741-748, July 1993. FIG. 13 is a block diagram of an apparatus configured according to the above document. In the figure, 501 is a transmitter, 502 is a transmission / reception switch, 503 is a transmission / reception antenna,
Reference numeral 504 denotes a receiver, 505 denotes a display, 25 denotes an observation range profile accumulator, 35 denotes a target identification circuit, 351 denotes a correlator, 352 denotes a candidate target range profile database, and 303 denotes determination means. FIG. 14 is a diagram for explaining the processing content of the target identification circuit in FIG.

Next, the operation will be described. The radar apparatus having the high range resolution identifies a target by using a range profile of the observed target. Here, the range profile will be described first. A range profile transmits a short pulse of electromagnetic waves, receives the reflected waves reflected by the target, and records as a function of time. The range profile can be regarded as a projection of the spatial distribution of the target reflection coefficient in the direction of the line of sight of the radar.

FIG. 15 shows the concept of range profile observation. The pulse transmitted at time t1 is incident on a strip-shaped area (distance resolution cell) having a pulse width w as shown in the figure at time t2, and is reflected there. At a different time t3, the transmission pulse enters another range bin as shown in the figure, and is reflected there. Therefore, if the reflected waves from the target are received and recorded as a function of time, the reflected waves from each distance resolution cell can be recorded in order from the one closer to the antenna. In this way, the target range profile is observed. In this conventional method, the range profile is considered to be a real number range profile having only the received electric field strength (without considering the phase).

[0005] Since the range profile varies depending on the target, the target can be identified using the observed range profile. The principle of this target identification will be described below. A known range profile of a certain target x (hereinafter, a known range profile of a certain target is appropriately referred to as reference data) is referred to as ffx (= (fx (0), fx
(1), ..., fx (K-1)]). Now, if the observed range profile is represented by pp (= [p (0), p (1), ..., p (K-1)]), the known range profile ffx of the target x and
The correlation coefficient Φ with the observed range profile pp is calculated by the following equation.

[0006]

(Equation 1)

In equation (1), peak [.] Is an operation for selecting the maximum value of the function. The symbol * represents a correlation operation defined by the following equation.

[0008]

(Equation 2)

The correlation between ffx and pp can be obtained as a function of shift s (correlation function) by the correlation operation of equation (2). As shown in equation (1), here, the correlation coefficient Φ between ffx and pp is It is defined by the maximum value of this correlation function.

Here, consider identifying N types of targets (x1, x2,..., XN). It is assumed that the range profiles (ffx1, ffx2,..., FfxN) of these N types of targets have been accumulated as reference data from prior observation or the like. The correlation coefficients (Φ1, Φ2,..., ΦN) between the observed range profile pp and these N types of range profiles are determined by the husband and wife equation (1). Here, the target can be identified by classifying the target into one having the largest correlation coefficient. For example, if Φ1 is maximum, the observed target is identified as x1, and if Φ2 is maximum, the observed target is identified as x2.

Hereinafter, the specific processing will be described with reference to FIG. The broadband pulse generated by the transmitter 501 is radiated to the observation target from the transmission / reception antenna 503 via the transmission / reception switch 502, and the echo scattered by the observation target is received by the receiver via the transmission / reception antenna 503 and the transmission / reception switch 502. Then, the obtained time-series received signals are accumulated in the observation range profile accumulator 25. Target identification circuit 35
The target is identified from the received signal observed by the above, and the identification result is output to the display 505.

The operation of the target identification circuit 35 will be described with reference to FIG. The target identification circuit 35 includes a correlator 351, a candidate target range profile database 352, and a determination unit 3.
03. The candidate target range profile database 352 stores range profiles of N types of candidate targets as reference data. The correlator 351 calculates the correlation between the observation value accumulated in the observation range profile accumulator 25 and the N kinds of reference data by an equation.
Calculate and output according to (1). The determination unit 303 selects the maximum value from the output result from the correlator 351 and outputs the type of reference data having the maximum value as the identification result. Thus, the target can be identified.

[0013]

However, in the conventional apparatus as described above, when there are a plurality of targets having similar range profiles, there is a problem that these targets cannot be accurately identified. The above cited references give examples of different targets with very similar range profiles, in which case the range profile information alone would not be able to identify these targets, but would be identifiable with prior information on the target aspect angles. It is going to be. However, since the range profile of the target greatly changes due to a slight change in the target aspect angle (the angle between the target centerline and the line of sight of the radar), the aspect angle of the observation target is not exactly equal to the aspect angle of the reference data. Otherwise, the value of the correlation coefficient will be low. Therefore, in the conventional apparatus, there is also a problem that the probability of correctly identifying a target is deteriorated if the accuracy of prior information regarding the aspect angle of the target is not sufficient.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and a target identification radar apparatus having an improved probability of correctly identifying a target even when a plurality of targets have similar range profiles. The purpose is to get. It is another object of the present invention to provide a target identification radar device with an improved probability of correctly identifying a target even when sufficient accuracy information about the target aspect angle cannot be obtained in advance.

[0015]

According to a first aspect of the present invention, there is provided a target identifying radar apparatus comprising: a high-resolution target identifying radar apparatus having two polarization characteristics orthogonal to each other; Antennas, to collect the scattering matrix of the observation target, of these antennas, one of these antennas in transmission, a polarization switch that drives both in reception, and a transmitter that generates and transmits broadband pulses, An observation scattering matrix range profile accumulator that stores a scattering matrix for each resolution cell of the observation target, and a target identification unit that identifies a target by using a range profile of a target observed with multiple polarizations. And

According to a second aspect of the present invention, there is provided a target identifying radar apparatus, wherein the target identifying means in the target identifying radar apparatus according to the first aspect includes a scattering matrix of a plurality of candidate targets obtained by prior observation or theoretical calculation. A database that stores a range profile, a multi-range profile correlator that calculates a correlation coefficient between the scattering matrix range profile of the observation target from the observation scattering matrix range profile accumulator and the scattering matrix range profile of the candidate target,
Determining means for performing determination for target identification.

According to a third aspect of the present invention, there is provided a target identifying radar apparatus for collecting two antennas having polarization characteristics orthogonal to each other and a scattering matrix of an observation target. Of these antennas, a polarization switch that drives one of them for transmission and the other for reception, a transmitter that generates and transmits broadband pulses, and a scattering matrix for each resolution cell to be observed are stored. Observed scattering matrix range profile accumulator, and decompose the observed target scattering matrix range profile into polarization components for each distance resolution cell, form a range profile for each polarization component, and use this range profile. And target identification means for performing target identification by using

According to a fourth aspect of the present invention, there is provided a target identifying radar apparatus, wherein the target identifying means in the target identifying radar apparatus according to the third aspect includes a scattering matrix of a plurality of candidate targets obtained by prior observation or theoretical calculation. A database that stores a range profile, a polarization component decomposition circuit that decomposes the scattering matrix for each resolution cell of the scattering matrix range profile of the candidate target and the scattering matrix range profile of the observation target into polarization components, Multi-range profile correlation for calculating a correlation coefficient between a range profile for each polarization component of the observation target obtained by polarization component decomposition and a range profile for each polarization component of the scattering matrix range profile of the candidate target And a determination means for performing determination for target identification.

According to a fifth aspect of the present invention, there is provided a target identifying radar apparatus, wherein the multi-range profile correlator of the target identifying means in the target identifying radar apparatus according to the second or fourth aspect of the present invention identifies a target. It is a phase information non-use type correlator that calculates a correlation coefficient using only the power or electric field strength of the plurality of range profiles.

According to a sixth aspect of the present invention, there is provided a target identifying radar apparatus, wherein the multi-range profile correlator of the target identifying means in the target identifying radar apparatus according to the second or fourth aspect of the present invention identifies a target. It is a phase information utilizing type correlator that calculates a correlation coefficient using a relative phase in each of the distance resolution cells of the plurality of range profiles and an electric field intensity.

According to a seventh aspect of the present invention, there is provided a radar apparatus for target identification, wherein the target identification means in the radar apparatus for target identification according to the second or fourth aspect provides a reception signal for a plurality of range profiles used for target identification. There is provided a transmission / reception polarization combination selecting means for selecting based on the ratio between the level and the receiver noise level and using it for target identification.

According to an eighth aspect of the present invention, there is provided a target identifying radar apparatus, wherein the target identifying means in the target identifying radar apparatus according to the second or fourth aspect uses observation values of a plurality of range profiles used for target identification. A range profile weighting means for performing weighting based on the likelihood of the target and using the weight for target identification.

According to a ninth aspect of the present invention, there is provided a target identifying radar apparatus according to the second or fourth aspect, wherein the target identifying result of the target identifying means is the same many times. A plurality of hit determination means for determining a target as a target is provided.

According to a tenth aspect of the present invention, there is provided the radar apparatus for target identification, wherein the multi-range profile correlator of the target identification means of the radar apparatus for target identification according to the second or fourth aspect further comprises a correlation between the observation data and the reference data. It is characterized by a multi-range profile correlator using FFT and IFFT that calculates the function by multiplication in the frequency domain.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a configuration block diagram showing Embodiment 1 of the present invention. In the figure, 101 is a transmitter, 102 is a transmission / reception switch, 103 is a polarization switch, 104 is a first polarization transmission / reception antenna, 105 is a second polarization transmission / reception antenna, 106 is a receiver, 107 is a display, Is the observed scattering matrix range profile accumulator, 3
Reference numeral 0 denotes a target identification circuit using a multi-polarization real number range profile, reference numeral 301 denotes a multi-range profile correlator not using phase information, reference numeral 302 denotes a candidate target scattering matrix range profile database, and reference numeral 303 denotes determination means.

The processing contents of this embodiment will be described with reference to FIGS. First, the scattering matrix range profile will be described. The wave incident on the target and the scattered wave from the target are originally represented as vectors in space, as is clear from the description of Maxwell's equation. In particular, when the target exists sufficiently far away in free space, these electromagnetic waves can be regarded as plane waves, and thus the electric field (magnetic field) can be treated as a two-dimensional vector on a plane orthogonal to the traveling direction. .

The manner in which the electric field (magnetic field) vector changes with time in the plane wave is understood and classified as the wave polarization, that is, the concept of so-called polarization. When an electromagnetic wave is represented by a vector, the scattering characteristics of the observation target are also represented by a scattering matrix (Scattering Matrix) instead of a scalar value such as a radar cross section (RCS).

At time t, frequency f at position vector rr,
The plane wave EE (rr, t) of the wave vector kk is represented by the following equation.

[0029]

(Equation 3)

Here, EE0 is a complex electric field vector, and a vertical (vertical: v) electric field component Ev and a horizontal direction (hor
Using the electric field component Eh of izontal: h), it can be expressed as the following equation.

[0031]

(Equation 4)

Here, ρ is expressed by the following equation.

[0033]

(Equation 5)

[0034] Av e ^{j [delta] v} in the equation (3) Since the act in common to both components, eventually, the vector [1, ρ] ^T: state of polarization (T denotes the transpose) of the plane wave (polarization state )
Will be characterized. Therefore, a vector EEJ in which the Euclidean norm of [1, ρ] ^T is 1 is defined by the following equation.

[0035]

(Equation 6)

Here, * represents conjugate. In the following, the formula
The expression format of the electric field vector in (4) is called Jones Vector format. The polarization state of the wave incident on the target, that is, the polarization state of the transmitting antenna, is represented by a complex electric field vector EEt in JonesVector format. The complex electric field vector EEs of the scattered wave in this case is given by the following equation.

[0037]

(Equation 7)

In the above equation, [S] is a scattering matrix representing the scattering characteristics of the observation target, and is represented by the following equation.

[0039]

(Equation 8)

Here, Svv is the V component of the scattered wave when the polarization of the incident wave is V, Svh is the H component of the scattered wave when the polarization of the incident wave is V, and Shv is the polarization of the incident wave. Shh represents the V component of the scattered wave when H is the H component of the scattered wave when the polarization of the incident wave is H. (Svv, S
vh, Shv, and Shh are complex numbers).

When this scattered wave is polarized by Jones Vect
The reception voltage Vs when receiving with the receiving antenna given by the complex electric field vector E Er of the or form is given by the following equation.

[0042]

(Equation 9)

Therefore, the received power Ps in this case is expressed as follows.

[0044]

(Equation 10)

It is known that the following equation holds when the transmitting antenna and the receiving antenna are monostatic.

[0046]

[Equation 11]

Now, if the scattering matrix of the observation target can be observed, its range profile can also be observed as the range profile of the scattering matrix. That is, as shown in FIG. 2, four elements of the scattering matrix Svv, Svh, Shv, Sh
For each of h, a range profile similar to that shown in FIG. 15 can be obtained. These four range profiles are collectively referred to herein as a scattering matrix range profile. Alternatively, it is synonymous to consider a scattering matrix for each distance resolution cell arranged in the distance direction as a scattering matrix range profile. Note that FIG.
In, the range profile is shown in the form of electric field strength, but each element of the scattering matrix range profile is inherently complex.

Next, the processing contents of this embodiment will be described with reference to FIG. The broadband pulse generated by the transmitter 101 is sent to the polarization switch 103 via the transmission / reception switch 102. The polarization switch 103 transmits a transmission signal to the first polarization transmission / reception antenna 104 of the first polarization transmission / reception antenna 104 and the second polarization transmission / reception antenna 105.

Here, the first polarized wave transmitting / receiving antenna 104 and the second polarized wave transmitting / receiving antenna 105 are a set of antennas whose polarization characteristics are orthogonal to each other. For example, a pair of vertical polarization and horizontal polarization, a pair of right-hand circular polarization and left-hand circular polarization, etc. are well known as the two orthogonal polarization characteristics.

The signal transmitted from the first polarized wave transmitting / receiving antenna 104 is scattered by the observation target. This is sent to the polarization switch 103 via the first polarization transmission / reception antenna 104 and the second polarization transmission / reception antenna 105. These signals are transmitted to the receiver 106 via the duplexer 102, respectively.
Sent to The signal demodulated by the receiver is stored in the observation scattering matrix range profile accumulator 2 in the form of the range profile of the complex reflection coefficients S11 and S12 of the observation target (where Sij is the j-th polarization transmission / reception antenna). Represents the reflection intensity transmitted and received by the i-th polarization transmitting / receiving antenna).

Similarly, the broadband pulse generated by the transmitter 101 is sent to the polarization switch 103 via the transmission / reception switch 102, and is radiated to the target from the second polarization transmission / reception antenna 105 to repeat the same processing. Thus, the range profile of the complex reflection coefficients S21 and S22 of the observation target is obtained. This is similarly stored in the observation scattering matrix range profile accumulator 2. As a result of the above processing, the range profiles of S11, S12, S21, and S22 are stored in the observation scattering matrix range profile accumulator 2, respectively. Alternatively, the scattering matrix [Sk] (k = 1,2,
..., K) is equivalent.

[0052]

(Equation 12)

FIG. 3 shows operation modes of the first polarized wave transmitting / receiving antenna 104 and the second polarized wave transmitting / receiving antenna 105 at respective times. The intervals in the figure are a summary of the processing required to obtain the scattering matrix range profile.

In the candidate target scattering matrix range profile database 302, N types of target scattering matrix range profiles [Snk] (k = 1, 2,
.., K, n = 1, 2,..., N) are stored. [Snk] is a theoretical calculation (eg, GTD: Geometrical Theory)
Needless to say, it is also possible to obtain it from, for example, of Diffraction.

[0055]

(Equation 13)

Next, the correlation between the observed scattering matrix range profile and the candidate target scattering matrix range profile is calculated in the phase information non-use type multi-range profile correlator 301. The operation of the multi-range profile correlator 301 will be described with reference to FIG. Now, assume that the observed scattering matrix range profile is represented by equation (12).
Further, it is assumed that a known scattering matrix range profile (reference data) of a certain candidate target x is represented by Expression (14).

[0057]

[Equation 14]

In FIG. 4, range profiles are drawn for three components Shh, Shv, and Svv as scattering matrix range profiles. This is because, when the radar has a monostatic configuration, since the equation (11) is satisfied, it is not necessary to use the Shv and Svh range profiles redundantly. However, if the radar has a bistatic configuration,
(11) does not hold and a range profile of Svh is needed.

At this time, the correlation coefficient Φm between the known scattering matrix range profile [Sxk] of the candidate target x and the observed scattering matrix range profile [Sk] is defined by the following equation.

[0060]

(Equation 15)

However,

[0062]

(Equation 16)

Φm is a value obtained by calculating a correlation coefficient between a candidate target and observed data for the range profile of each element of the scattering matrix, and averaging them. Expression (1
In 5), the operation * is defined in the same manner as in the equation (2). This is shown again in equation (17). peak [.] is the same as the definition in equation (1).

[0064]

[Equation 17]

In the multiple range profile correlator 301, the observed scattering matrix range profile and the candidate target scattering matrix range profile database 302
Is calculated according to equation (17).

By the way, the multi-range profile correlator 301 not using phase information is realized by using the configuration of the multi-range profile correlator using FFT and IFFT shown in FIG. 5 instead of the configuration shown in FIG. Is also possible. This is a configuration that enables the correlation operation of Expression (17) to be executed with a smaller amount of calculation by executing the multiplication in the frequency domain. This principle is shown in equations (18) and (19). This equation is described, for example, in the document "Basics of Digital Signal Processing" IEICE.

[0067]

(Equation 18)

However,

[0069]

[Equation 19]

Here, FFT {.} Is a fast Fourier transform (Fast
Fourier Transform) and IFFT {.} Are inverse fast Fourier transforms (In
verse Fast Fourier Transform). FIG. 5 shows a configuration in which the correlation coefficient is calculated by Expressions (18) and (19) instead of Expression (17). This applies the FFT to the observed scattering matrix range profile and the range profile for each element of the target scattering matrix range profile, and transforms them into the frequency domain. Next, the operation of multiplying observation data and reference data in the frequency domain, applying IFFT to the result, and obtaining the correlation function in the time domain again is shown.

The value of the correlation coefficient obtained by the multi-range profile correlator 301 is sent to the judgment means 303. In the determination means 303, as in the conventional technique,
The maximum value is selected from the N correlation coefficients, and the type of reference data having the maximum value is output as the identification result.
This identification result is displayed via the display 107.

As described above, according to the first embodiment,
By using the scattering matrix range profile for target identification, in addition to the target range profile, the target is identified using information on the polarization characteristics of scattering, so that the range profile for single polarization as in the prior art is used. It is possible to improve the probability of correctly identifying the target, as compared with the case where the target is identified by using. Further, since only the real number components are used without using the phase components of the scattering matrix range profile, the configuration can be simplified. Although it is not possible to use all of the polarization characteristics of scattering, it is not necessary to measure the phase component, so that the configuration of the receiver and the like can be simplified.

Embodiment 2 FIG. 6 is a configuration block diagram showing a second embodiment of the present invention. In the figure, 31 is a target identification circuit using a multi-polarization complex range profile,
Reference numeral 311 denotes a multi-range profile correlator utilizing the phase information. 101, 102, 103, 104, 105,
106, 107, 2, 302, and 303 are the same as those in FIG.

In the first embodiment, the phase component of the scattering matrix range profile is not used for identifying a target. On the other hand, the present embodiment is characterized in that the phase component of the scattering matrix range profile is used. That is, target identification is performed using a range profile including relative phases among the elements S11, S12, S21, and S22 of the scattering matrix.

Hereinafter, the processing of this embodiment will be described with reference to FIG. In the figure, 101, 102, 103, 10
The operations of 4, 105, 106, 107, 2, 302, and 303 are the same as in the first embodiment. In the present embodiment, the observed scattering matrix range profile accumulator 2 and the candidate target scattering matrix range profile database 30
The scattering matrix range profile stored in 2 is sent to a multi-range profile correlator 311 using phase information. The phase information-based multi-range profile correlator 311 first converts the phase of each element of the scattering matrix into a relative phase with respect to the phase of S11, k for each distance resolution cell k by the following process.

[0076]

(Equation 20)

Therefore, the scattering matrix range profile [Sk] (k = 1, 2,... K) input to the phase information utilizing multi-range profile correlator 311 has a relative phase scattering matrix range profile defined by the following equation. [SRk] (k = 1, 2,... K).

[0078]

(Equation 21)

Here, δij, k represents the phase of Sij, k.

Next, the correlation coefficient Φm between the relative phase scattering matrix range profile [SRxk] of the candidate target x and the observed relative phase scattering matrix range profile [SRk] is calculated by the following equations (15) and (1).
It is calculated in the same way as 6). However, here, the definition of the operation * in the equation (15) is different from the definition of the equation (17) and is as follows.

[0081]

(Equation 22)

The multi-range profile correlator 311 using the phase information uses the FF described in the first embodiment.
Needless to say, the same can be realized by using a configuration of a multi-range profile correlator using T and IFFT.

As described above, according to the second embodiment, all information including the phase information in the polarization characteristics of scattering of a target is used for target identification. ,
The probability of correctly identifying a target can be improved.

Embodiment 3 FIG. 7 is a configuration block diagram showing a third embodiment of the present invention. In the figure, 32 is a polarization component range profile-based target identification circuit,
321 is a polarization component decomposition circuit. 101,10
2,103,104,105,106,107,2,3
01, 302, and 303 are the same as those in FIG.

FIGS. 8 and 9 are diagrams used to explain the processing of the present embodiment. FIG. 8 is a schematic diagram showing a scatterer, and FIG. It is a figure for explaining change of a matrix.

First, the polarization component decomposition circuit will be described. When the radar has a monostatic configuration, since the equation (11) holds, any scattering matrix [S] can be represented by an odd number of reflections (Od
d Bounce) [S] odd representing the polarization characteristic of polarization, [S] even representing even number of reflections (Even Bounce), Cross component (Cross)
Can be expressed as the following equation as a combination of three kinds of basic components of [S] cross.

[0087]

(Equation 23)

Here, the scattering matrices of these three kinds of basic components are as shown in the following equations. FIG. 8 shows an example of a scatterer whose polarization characteristic of scattering is represented by these scattering matrices.

[0089]

(Equation 24)

When the scattering matrix [S] is observed, the three-component coefficients Co, Ce, and Cc are obtained as follows. Since this operation is nothing but the decomposition of the observed scattering matrix into three fundamental components, this is called polarization component decomposition.

[0091]

(Equation 25)

The polarization component decomposition method represented by the equations (24) and (25) is an example in the case where the radar has a monostatic configuration. There are several ways to decompose the scattering matrix into polarization components, for example, Shane Robert Cloude &
Eric Pottier, “A Review of Target Decomposition T
heoremsin Radar Polarimetry ”IEEE Trans. on Geosc
ience and Remote Sensing, vol.34, no.2, pp.498-51
8, Mar. 1996. In the present embodiment, the polarization component decomposition will be described by taking only the method represented by Expressions (24) and (25). However, the present invention is not limited to this, and the scattering matrix is decomposed into a plurality of components. Needless to say, this method may be used.

Next, the processing contents of this embodiment will be described with reference to FIG. In the figure, 101, 102, 103,
104, 105, 106, 107, 2, 301, 303
Are the same as those in the first embodiment, and a description thereof will be omitted. In the present embodiment, the scattering matrix range profile stored in the observed scattering matrix range profile accumulator 2 and the candidate target scattering matrix range profile database 302 is sent to the polarization component decomposition circuit 321. The polarization component decomposing circuit 321 decomposes the scattering matrix [Sk] (k = 1, 2,..., K) for each distance resolution cell k according to equation (25). Then, the range profile of the components of the three polarization components, the component of the odd number of reflections (Co), the component of the even number of reflections (Ce), and the cross component (Cc), is obtained as in the following equation.

[0094]

(Equation 26)

The range profiles of the three components of the polarization component of the observation data obtained by the polarization component decomposition circuit 321 are CCo, CCe, and CCc, and the range profiles of the three components of the polarization component of the candidate target x are CCxo and CCxe. , CCxc. In the multi-range profile correlator 301 without phase information, a correlation coefficient is calculated for these input range profiles. This process is defined by the following equation.

[0096]

[Equation 27]

However,

[0098]

[Equation 28]

Note that this applies to the case where the same calculation as Expressions (15) and (17) is applied to the range profile of three components of the polarization component instead of being applied to the range profile of each element of the scattering matrix. Nothing else.

Although the correlation coefficient is obtained by using the multi-range profile correlator 301 which does not use the phase information in this embodiment, each distance resolution may be obtained in the same manner as the processing shown in the second embodiment. For each cell k, the phase of each element is replaced with, for example, a relative phase with respect to the phase of the element Co, and the correlation coefficient of the complex range profile including this phase component is calculated by the equation (2
It can be easily derived that it is possible to calculate according to the definition of 2) and use the value of the correlation coefficient for identification. Here, it is needless to say that the multi-range profile correlator 301 of FIG. 7 can also be realized by using the configuration of the FFT / IFFT-based multi-range profile correlator shown in FIG. 5 described in the first embodiment.

According to the third embodiment, since the polarization component decomposition is performed and the range profile for each polarization component is used for target identification, even if the accuracy of the prior information regarding the target aspect angle is not sufficient, the target The discrimination performance can be improved.

Hereinafter, the above characteristics will be described. Now, as shown in FIG. 9, consider a case where a three-sided corner reflector and a two-sided corner reflector are included in one distance resolution cell at a distance d. Consider observing this from the radar line-of-sight direction (hereinafter abbreviated as LOS as appropriate) as shown in the figure. FIG. 8 shows a schematic diagram and characteristics of various corner reflectors. Here, assuming that the scattering matrices ([S] odd, [S] even) of the three-sided corner reflector and the two-sided corner reflector shown in FIG. The scattering matrix [S] LOS observed when each resolution cell is observed is represented by the following equation.

[0103]

(Equation 29)

Where λ is the wavelength of the electromagnetic wave used for observation, φ
Is the phase determined by the distance between the three-sided corner reflector and the radar.

In equation (29), focusing on the Shh component (H component of the scattered wave when the polarization of the incident wave is H) among the four components of the scattering matrix [S] LOS, the electric field strength is It is confirmed that the angle varies depending on the angle θ between the line connecting the surface corner reflector and the three-surface corner reflector and the line of sight of the radar.
However, as is clear from equation (29), this scattering matrix [S] L
When OS is decomposed into an odd-number reflection component Co and an even-number reflection component Ce, | Co | and | Ce | do not depend on the angle θ. Therefore, by performing the polarization component decomposition, it is possible to improve the target discrimination performance when the accuracy of the advance information regarding the target aspect angle is not sufficient.

As described above, according to the third embodiment, when the polarization component is decomposed and the range profile for each polarization component is used, the range profile with a small variation due to the change in the target aspect angle is obtained. Is used for target identification, so that the probability of correctly identifying the target can be improved even when the accuracy of the advance information on the aspect angle of the target is not sufficient.

Embodiment 4 FIG. 10 is a configuration block diagram showing a fourth embodiment of the present invention. In the figure, 33
Is a polarization channel selection type target identification circuit. The transmission / reception polarization combination selection circuit 331 and the transmission / reception polarization combination extraction circuit 332 are circuits for implementing transmission / reception polarization combination selection means. 101, 102, 103, 104, 105, 1
06, 107, 2, 301, 302, and 303 are the same as those in FIG.

The processing contents of the present embodiment will be described with reference to FIG. In the figure, 101, 102, 103, 10
4,105,106,107,2,301,302,3
The operation of 03 is the same as that of the first embodiment. In the present embodiment, the scattering matrix range profile stored in the observation scattering matrix range profile accumulator 2 is sent to the transmission / reception polarization combination selection circuit 331 constituting transmission / reception polarization combination selection means. Transmit / receive polarization combination selection circuit 331
Is in the observed scattering matrix range profile:
Focusing on the range profile for each element, the received signal level (peak level, average level, etc.) is the receiver noise level
Only those exceeding β times Pn (determined according to the system) are selected and output. For example, if the signal level of SS12 and SS21 is
If βPn or less, transmit / receive polarization combination selection circuit 3
The range profile selected by 31 is SS11, SS
22. (Here, SSij conforms to the definition of equation (16)).

The above selection result is transmitted to a transmission / reception polarization combination extraction circuit 332 constituting transmission / reception polarization combination selection means.
From the scattering matrix range profile of the candidate target, only the range profile of the element selected by the transmission / reception polarization combination selection circuit 331 is extracted and output. That is, in the case of the above example, among the scattering matrix range profiles of the candidate target x, those selected by the transmission / reception polarization combination extraction circuit 332 are SSx11 and SSx22 (where SSxij is defined by Expression (16). According).

The range profile selected as described above is input to the phase information non-use type multiple range profile correlator 301, and the correlation coefficient between the observation data and the reference data is calculated using them.

In the present embodiment, the method of selecting an element used for target identification from the four elements of the observed scattering matrix has been described. However, the polarization component as described in the third embodiment is used. It goes without saying that a method of selecting a range profile to be used for target identification in a similar procedure for a range profile for each polarization component obtained by performing the decomposition can be easily derived from the above description.

It is generally known that the level of the received power may be extremely low depending on the combination of the transmission and reception polarizations. In this case, the noise profile may become dominant in the range profile observed in the combination of the transmission and reception polarizations, which may hinder target recognition. In such a case, by adopting the present embodiment, a range profile having a low reception level can be removed in advance, and a decrease in target recognition performance can be prevented.

As described above, according to the fourth embodiment, the scattering matrix range profile stored in the observed scattering matrix range profile accumulator 2 and the candidate target scattering matrix range profile database is the same as the observed scattering matrix range profile. Of the components, only those whose received signal level sufficiently exceeds the receiver noise level are selected,
Since a plurality of range profiles are correlated except for those that hinder target identification, the probability of correctly identifying targets can be improved.

Embodiment 5 FIG. FIG. 11 is a configuration block diagram showing a fifth embodiment of the present invention. In the figure, 34
Is a polarization channel weighted target identification circuit. The range profile weight determining circuit 341 and the range profile weighting circuit 342 are circuits that implement a range profile weighting unit. 101, 102, 10
3,104,105,106,107,2,301,3
02 and 303 are the same as those in FIG.

The processing contents of this embodiment will be described with reference to FIG. In the figure, 101, 102, 10
3,104,105,106,107,2,301,3
The operation of 03 is the same as that of the first embodiment. In the present embodiment, the scattering matrix range profile stored in the observation scattering matrix range profile accumulator 2 and the candidate target scattering matrix range profile database is sent to the range profile weight determination circuit 341. In the range profile weight determination circuit 341,
The coefficient Wij (i, j = 1,2) in each range profile is multiplied by the following equation.

[0116]

[Equation 30]

Here, the coefficient Wij to be multiplied by the range profile of each element Sij (i, j = 1, 2) is set such that the value of Wij becomes larger for a range profile having a higher received signal level. In the present embodiment, a method for weighting the range profile of the four elements of the observed scattering matrix has been described.
It goes without saying that a method of weighting the range profile for each polarization component obtained by performing the polarization component decomposition as described in the above in the same manner can be easily derived from the above description.

As described above, according to the fifth embodiment,
For the scattering matrix range profile stored in the observed scattering matrix range profile accumulator 2 and the candidate target scattering matrix range profile database, a lower weight is set to the lower range profile of the received signal level to correlate a plurality of range profiles. By doing so, it is possible to reduce the influence of components that hinder target identification and at the same time to take into account all of the polarization characteristics of the scattering of the target, so that the performance of target identification can be improved.

Embodiment 6 FIG. FIG. 12 is a configuration block diagram showing a sixth embodiment of the present invention. In the figure, reference numeral 4 denotes a multiple hit data majority circuit. 101, 102,
103, 104, 105, 106, 107, 2, 30,
Reference numerals 301, 302, and 303 are the same as those in FIG.

The processing contents of this embodiment will be described with reference to FIG. In the figure, 101, 102, 103, 10
4,105,106,107,2,301,302,3
The operation of 03 is the same as that of the first embodiment. The multiple hit data majority circuit 4 is a circuit that implements a multiple hit determination unit. When the same target can be continuously observed a plurality of times, the identification result in each observation is temporarily stored. The target is identified as the most consistent result, even if the identification result at each observation does not show the same result each time. Although FIG. 12 shows an example in which the multiple-hit data majority circuit 4 is added to the output stage of the target identification circuit 30 of FIG. 1 showing the first embodiment, the invention is not limited to this. Needless to say, the same effect can be obtained even if the multiple hit data majority circuit 4 is added to the output stage of the target identification circuit 32 of FIG.

As described above, according to the sixth embodiment,
When it is possible to continuously observe the same target a plurality of times, it becomes possible to identify the target using the results of the observations made a plurality of times, so that the target identification performance can be improved.

[0122]

As described above, according to the first aspect of the present invention, two antennas having polarization characteristics orthogonal to each other are provided, and a target range profile observed with multiple polarizations is used. By performing the identification, even when the range profiles of a plurality of targets are similar, the targets can be correctly identified as compared with the case where the targets are identified using the range profiles of the targets observed with the conventional single polarization. It is possible to obtain a target identification radar device with an improved identification probability.

According to the second aspect of the present invention, the target identifying means according to the first aspect of the present invention comprises a plurality of candidate target scattering matrix range profiles obtained by preliminary observation or theoretical calculation and a target matrix. By providing a multi-range profile correlator for calculating a correlation coefficient with the scattering matrix range profile, even when the range profiles of a plurality of targets are similar to each other, similar to the effect of the invention according to claim 1, Can be obtained with an improved probability of correctly identifying the target.

According to the third aspect of the present invention, two antennas having polarization characteristics orthogonal to each other are provided, and a target scattering matrix range profile observed in multiple polarizations is converted into a polarization Decomposition into components, including target identification means for performing target identification using a range profile for each polarization component, and using a range profile with small fluctuations due to a change in the target aspect angle for target identification, Even if the accuracy of the prior information regarding the aspect angle of the target is not sufficient, it is possible to obtain a target identification radar device in which the probability of correctly identifying the target is improved.

According to a fourth aspect of the present invention, in the target identifying means according to the third aspect of the present invention, the scattering matrix range profile of the candidate target and the scattering matrix range profile of the observation target are respectively set to a distance resolution. By decomposing into polarization components for each cell and performing target identification using the range profile for each polarization component,
Similarly to the effect of the third aspect of the present invention, a range profile with a small variation due to a change in the aspect angle is used for target identification. Therefore, even when the accuracy of the prior information on the target aspect angle is not sufficient, the target is correctly identified. It is possible to obtain a target identification radar apparatus with an improved probability of performing the target identification.

According to the fifth aspect of the present invention, the multi-range profile correlator of the target identification means in the target identification radar device according to the second or fourth aspect,
A phase information non-use type multi-range profile correlator that calculates a correlation coefficient using only the power or electric field strength of the plurality of range profiles to identify a target is provided, and a phase component of a scattering matrix range profile is used. Without
By using only the real number component, in addition to the effect of the invention according to claim 2 or 4, the configuration of the receiver and the like of the target identification radar device is simplified and the target identification is simplified in processing load. Radar device can be obtained.

According to a sixth aspect of the present invention, in the target identifying radar apparatus according to the second or fourth aspect, the multi-range profile correlator of the target identifying means includes:
A phase information-based correlator for calculating a correlation coefficient using a relative phase in each of the distance resolution cells of the plurality of range profiles and an electric field strength to identify a target; In addition to the effect of the invention according to claim 2 or claim 4, the probability of correctly identifying a target is improved by using all information including the phase information in the information on the polarization characteristics of the scattered light. The obtained target identification radar device can be obtained.

According to the seventh aspect of the present invention, the target identification means in the target identification radar device according to the second or fourth aspect is configured such that a target signal level and a reception signal level of a plurality of range profiles used for target identification are determined. Make a selection based on the ratio of the receiver noise level and use it for target identification,
With transmission and reception polarization combination selection means, among the components of the observed scattering matrix range profile, select only those whose received signal level sufficiently exceeds the receiver noise level, except for those that hinder target identification, By correlating a plurality of range profiles, in addition to the effect of the invention according to claim 2 or claim 4, it is possible to obtain a target identification radar apparatus in which the probability of correctly identifying a target is improved.

According to the eighth aspect of the present invention, the target identifying means in the target identifying radar device according to the second or fourth aspect is capable of confirming the observed value of a plurality of range profiles used for the target identifying. A range profile weighting means for performing weighting based on the likelihood and using the same for target identification, and setting a lower weight for the observed scattering matrix range profile to a lower range profile of the received signal level for target identification; Claim 2 or Claim 4 by reducing the influence of components that hinder the image and correlating a plurality of range profiles.
In addition to the effects of the invention according to the description, it is possible to obtain a target identification radar apparatus in which the probability of correctly identifying a target is improved.

According to the ninth aspect of the present invention, the target identifying radar device according to the second or fourth aspect is characterized in that:
If the target identification result of the target identification means is the same as the target identification result and the number of times is large, the target identification means is provided with a determination means for multiple hits, and it is possible to continuously observe the same target multiple times. A target identifying radar apparatus in which the probability of correctly identifying a target is improved in addition to the effect of the invention according to claim 2 or 3 by identifying the target using the results of the second observation. Can be.

According to the tenth aspect of the present invention, the multi-range profile correlator of the target identification means of the target identification radar device according to the second or fourth aspect is configured such that the correlation function between the observation data and the reference data is determined. By using a multi-range profile correlator using FFT and IFFT calculated by multiplication in the frequency domain, the correlation operation is performed by multiplication in the frequency domain, thereby achieving the effect of the invention according to claim 2 or claim 4. In addition, it is possible to obtain a target identification radar device that can be executed with a smaller amount of calculation.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a scattering matrix range profile of an observation target.

FIG. 3 is a diagram illustrating operation modes of two orthogonally polarized transmission / reception antennas.

FIG. 4 is a diagram illustrating a configuration of a multi-range profile correlator.

FIG. 5 is a diagram illustrating a configuration of a multi-range profile correlator using FFT and IFFT.

FIG. 6 is a configuration block diagram showing a second embodiment of the present invention.

FIG. 7 is a configuration block diagram showing a third embodiment of the present invention.

FIG. 8 is a schematic diagram illustrating an example of a scatterer.

FIG. 9 is a diagram for explaining a change in a scattering matrix according to a change in the line of sight of the radar.

FIG. 10 is a configuration block diagram showing a fourth embodiment of the present invention.

FIG. 11 is a configuration block diagram showing a fifth embodiment of the present invention.

FIG. 12 is a configuration block diagram showing a sixth embodiment of the present invention.

FIG. 13 is a block diagram showing a configuration of a conventional target identification radar apparatus.

FIG. 14 is a diagram illustrating the target identification circuit of FIG. 13;

FIG. 15 is a conceptual diagram of target range profile observation.

[Explanation of symbols]

2 Observed Scattering Matrix Range Profile Accumulator 4 Multiple Hit Data Majority Decision Circuit 30 Target Identification Circuit Using Multi-Polarized Real Range Profile 31 Target Identification Circuit Using Multi-Polarized Complex Range Profile 32 Polarization Component Range Profile-Based Target discriminating circuit 33 Target discriminating circuit of polarization channel selection type 34 Target discriminating circuit of polarization channel weighting type 101 Transmitter 102 Transmit / receive switch 103 Polarization switch 104 First polarized transmitting / receiving antenna 105 Second polarized transmitting / receiving antenna 106 Receiver 107 Display 301 Multi-range profile correlator not using phase information 302 Candidate target scattering matrix range profile database 303 Judging means 311 Multi-range profile correlator using phase information 321 Polarization component decomposition circuit 331 Transmission / reception polarization Combination Selection circuit 332 transmits and receives the polarization combination extraction circuit 341 range profile weighting decision circuit 342 range profile weighting circuit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tetsuro Kirimoto 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation F-term (reference) 5J070 AB01 AD02 AD17 AE04 AH04 AH35 AK14 AK22 AL02

Claims (10)

[Claims] 1. A high-resolution target identification radar apparatus, comprising: two antennas having polarization characteristics orthogonal to each other; and one of these antennas for transmission in order to collect a scattering matrix of an observation target. In the reception, a polarization switch that drives both, a transmitter that generates and transmits broadband pulses, an observation scattering matrix range profile accumulator that stores the scattering matrix for each resolution cell to be observed, and a multi-polarization And a target identification unit that performs target identification using the range profile of the target observed in step (a). 2. A database for storing scattering matrix range profiles of a plurality of candidate targets obtained by prior observation or theoretical calculation, wherein the target identification means comprises: The multi-range profile correlator for calculating a correlation coefficient between a matrix range profile and a scattering matrix range profile of the candidate target, and a determination unit for performing determination for target identification. Target identification radar device. 3. A high-resolution target identifying radar apparatus, comprising: two antennas having polarization characteristics orthogonal to each other; and one of these antennas for transmission in order to collect a scattering matrix of an observation target. In the reception, a polarization switch that drives both, a transmitter that generates and transmits a broadband pulse, an observation scatter matrix range profile accumulator that stores the scatter matrix for each resolution cell of the observation target, A target identification unit that decomposes a target scattering matrix range profile into polarization components for each distance resolution cell, forms a range profile for each polarization component, and performs target identification using the range profile. A radar apparatus for identifying a target. 4. A database in which the target identification means stores a scattering matrix range profile of a plurality of candidate targets obtained by prior observation or theoretical calculation; a scattering matrix range profile of the candidate target; and a scattering of the observation target. A polarization component decomposition circuit for decomposing the scattering matrix for each resolution cell of the matrix range profile into polarization components, and a range profile for each polarization component of the observation target obtained by the polarization component decomposition, and A plurality of range profile correlators for calculating a correlation coefficient between a scattering matrix range profile of a candidate target and a range profile for each polarization component, and a determination unit for performing determination for target identification. The target identification radar device according to claim 3. 5. A phase information non-use type correlator for calculating a correlation coefficient using only the power or electric field strength of the plurality of range profiles to identify a target. The target identification radar device according to claim 2 or 4, wherein the target identification radar device is a multi-range profile correlator. 6. A multi-range profile correlator of said target identification means, wherein a relative phase at each distance resolution cell of said plurality of range profiles to identify a target;
The target identification radar device according to claim 2, wherein the target identification radar device is a multi-range profile correlator using a phase information that calculates a correlation coefficient using an electric field intensity. 7. A transmission / reception polarization combination selection, wherein the target identification means selects a plurality of range profiles used for target identification based on a ratio between a received signal level and a receiver noise level and uses the selected profile for target identification. The target identifying radar apparatus according to claim 2 or 4, further comprising means. 8. The target discriminating means weights a plurality of range profiles used for target discrimination based on the likelihood of the observed value and uses the weights for target discrimination.
5. The target identifying radar apparatus according to claim 2, further comprising a range profile weighting means. 9. The apparatus according to claim 2, further comprising a plurality of hits judging means for judging a target having a large number of times that the target discriminating means has the same target discrimination result as a target. Target identification radar device. 10. The multi-range profile correlator of the target identification means is a multi-range profile correlator using FFT and IFFT that calculates a correlation function between observation data and reference data by multiplication in the frequency domain. The target identification radar device according to claim 2 or 4.