JP2001108733A - Direction finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a phenomenon as if a moving radio wave source exists in a direction along which no moving radio wave source exists when a distance between antennas is larger than a wavelength, in the arrayed antennas. SOLUTION: An antenna platform arrayed with the plural antennas is rotated without changing an instantaneous directional field of view, or rotated while changing the instantaneous directional field of view, and a resulting locus of the moving radio wave source is found to suppress the phenomenon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direction detecting device for measuring the direction of a wave propagating from a single or a plurality of mobile radio wave sources.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional direction finder, and FIG. Schmidt, "M
multiple Emitter Location a
nd Signal Parameter Estima
Tion "IEEE Trans. on Antenna
and Propagation, vol. AP-3
4, no. 3 is a configuration diagram of a direction detection device based on the content described in March 1986.

FIG. 4 is a diagram showing an operation example of the above-described direction detecting device.

In FIG. 3, reference numeral 2 denotes an antenna platform on which a plurality of antennas directed in the same direction are mounted, 3 denotes a conventional signal processing device B for performing signal processing, 4 denotes a rotation driving device for rotating the antenna platform 2,
5-1, 5-2,..., 5-M are antennas of the same specification for receiving radio waves from the mobile radio source, 6-1, 6-1,.
-M are the antennas 5-1, 5-2,..., 5-
A receiver of the same specification for amplifying and frequency converting the radio wave received by M, and a covariance 7 for simultaneously sampling the outputs of the M receivers and performing snapshots a plurality of times to calculate a covariance matrix. A matrix calculator, 8 is an eigenvalue / eigenvector calculator for calculating an eigenvalue and an eigenvector from the covariance matrix, and 9 is a mode vector in a noise subspace based on the eigenvalue and the eigenvector obtained by the eigenvalue / eigenvector calculator 8. A noise subspace projection length calculator that projects and calculates the projection length, scans a virtual radio wave source in space, and performs a process when the projection length output from the noise subspace projection length calculator 9 becomes minimum. Projection length minimum value calculator for calculating the azimuth and elevation angle of the virtual radio source, 11 is a mode vector calculator for calculating the mode vector expected by the virtual radio source 12 is a control device for instructing a predetermined rotation angle in the rotation drive device 4 and the mode vector calculator 11.

[0005] In Fig. 4, reference numeral 1 denotes an orbiting satellite as an example of a mobile radio wave source.

Next, the operation will be described. Mobile radio source 1
Is smaller than the number M of the antennas 5, and the signals from the mobile radio sources are uncorrelated with each other. Now, the outputs of the M antennas 5 are respectively input to the receiver 6, where amplification and frequency conversion are performed.

[0007] The outputs of the M receivers 6 are input to a covariance matrix calculator 7. Here, when the outputs of the M receivers 6 are S ₁ , S ₂ ,..., S _M , respectively, the signal vector is represented by Equation 1.

[0008]

(Equation 1)

[0009] If it is assumed that the snapshot is performed P times in obtaining the covariance matrix, the covariance matrix calculator 7 calculates the value shown in Expression 2.

[0010]

(Equation 2)

Equation 2 is the output of the covariance matrix calculator 7.
Here, * represents conjugate or Hermitian conjugate.

The eigenvalue / eigenvector calculator 8 calculates M eigenvalues based on the obtained covariance matrix.
Eigenvectors are calculated for each eigenvalue,
These results are input to the noise subspace projection length calculator 9. ₁ above the eigenvalues λ, λ _2, ..., λ and _M, X ₁ and corresponding eigenvectors, X _2, ..., is given by Equation 3 using X _M Tosureba number 2.

[0013]

(Equation 3)

At this time, the covariance matrix is a positive definite matrix, and all eigenvalues are larger than zero. Assuming that the receiver noises of the receivers 6 are all equal and the standard deviation is σ, Equation 4 holds from the above assumption that the D signals are uncorrelated.

[0015]

(Equation 4)

The eigenvectors corresponding to the eigenvalues λ ₁ , λ ₂ ,..., Λ _D are X ₁ , X ₂ ,..., X _D, and λ _{D + 1} , λ _{D + 2} ,.
The eigenvector corresponding to the _{M X D + 1, X D} + 2, ..., if _{X M X 1, X 2,} ..., signal subspace and X _{D + 1} spanned by the X _D,
The noise subspaces spanned by X _{D + 2} ,..., X _M are mutually orthogonal complement spaces.

When the M antennas 5 are arrayed, the mode vector calculator 11 stores the data of the M antenna outputs, that is, the mode vectors, when it is assumed that the radio wave source exists at a certain angle. Usually, this angle is over a predetermined range.

However, the mode vector calculator 11 generates a mode vector corresponding to the angle range centered on the azimuth and elevation angle specified by the control device 12, and the rotation driving device 4 is specified by the control device 12. Antenna platform 2 facing azimuth and elevation
Move.

Accordingly, a mode vector at a certain azimuth angle α and a certain elevation angle β is generated by the mode vector calculator 11 and input to the noise subspace projection length calculator 9. On the other hand, the noise subspace projection length calculator 9 projects the mode vector to the noise subspace based on the input eigenvalue / eigenvector. Let this mode vector be a (α,
Then, the projection length given by Expression 5 is output from the noise subspace projection length calculator 9.

[0020]

(Equation 5)

The projection length minimum value calculator 10 obtains the projection length of the mode vector a (α, β) as a function of α and β, and gives the minimum values of α and β (α ₁ , β ₁ ),
(Α ₂ , β ₂ ),..., (Α _D , β _D ) are obtained.

Assuming that the mobile radio source hardly moves during the P number of snapshots, (α ₁ , β ₁ ),
(Α ₂ , β ₂ ),..., (Α _D , β _D ) are angle estimation values of directions in which D mobile radio sources exist at a certain time.

[0023]

Since the conventional direction finding apparatus is configured as described above, the aperture of the antenna is increased in order to increase the S / N (signal to noise) ratio of the output of each antenna. In this case, if the distance between the antennas is made to be wider than the wavelength, grating lobes are generated, and there is a problem that a mobile radio source exists even in a direction where no mobile radio source exists.

The present invention has been made to solve the above problems, and has as its object to suppress this phenomenon.

[0025]

According to a first aspect of the present invention, there is provided a direction finding apparatus comprising: a plurality of antennas for receiving radio waves from a mobile radio wave source; and an antenna platform having the plurality of antennas mounted so as to be directed in the same direction. Instantaneous view invariant rotation driving means for rotating the antenna platform while maintaining the directional directions of the plurality of antennas in accordance with the rotation angle command, and generating a plurality of different rotation angle commands for the instantaneous view invariant rotation drive Control means for supplying the respective rotation angle commands to a plurality of antennas; a plurality of receivers connected to the plurality of antennas to supply output signals of the antennas; A covariance matrix calculator for calculating a covariance matrix from
An eigenvalue / eigenvector calculator for calculating an eigenvalue and an eigenvector based on the covariance matrix output from the covariance matrix calculator, the rotation angle command supplied from the control means to the instantaneous visual field invariant rotation driving means, and A mode vector calculator for calculating a mode vector based on the arrangement of the plurality of antennas; and a noise subspace based on the eigenvalues / eigenvectors output from the eigenvalue / eigenvector calculator output from the mode vector calculator. And a azimuth angle of the radio source when the projection length output from the noise subspace projection length calculator becomes a minimum. And a projection length minimum value calculator for obtaining an elevation angle and the projection length minimum value for each rotation angle command. A trajectory calculator for calculating a trajectory based on the azimuth and elevation of the mobile radio source obtained from the value calculator, and determining whether or not the trajectory is based on the mobile radio source based on the shape of the trajectory obtained from the trajectory calculator And a determiner that performs the determination.

Further, the direction detecting device according to the second aspect of the present invention comprises:
A plurality of antennas for receiving radio waves from a mobile radio wave source, an antenna platform on which the plurality of antennas are mounted so as to be directed in the same direction, and a pointing direction of the plurality of antennas which varies according to a rotation angle command. Instantaneous field-of-view variation rotation drive means for rotating the antenna platform, and control means for generating a plurality of different rotation angle commands and supplying the respective rotation angle commands to the instantaneous field-of-view variation rotation drive means; A plurality of receivers connected to each of the plurality of antennas and supplied with output signals of the antennas; a covariance matrix calculator for calculating a covariance matrix from an output of the receiver; An eigenvalue / eigenvector calculator for calculating an eigenvalue and an eigenvector based on a covariance matrix output from the calculator; A mode vector calculator for calculating a mode vector based on the rotation angle command supplied from the control means to the instantaneous visual field fluctuation rotation driving means and the arrangement of the plurality of antennas, and an output from the eigenvalue / eigenvector calculator. A noise subspace projection length calculator for projecting a mode vector output from the mode vector calculator to a noise subspace extended based on the eigenvalues / eigenvectors to be calculated, and calculating a projection length thereof; A projection length minimum value calculator for obtaining an azimuth angle and an elevation angle of the radio wave source when the projection length output from the calculator is a minimum, and for each of the rotation angle commands,
A trajectory calculator for calculating a trajectory based on the azimuth and elevation of the mobile radio source obtained from the projection length minimum value calculator; and a trajectory based on the mobile radio source based on the shape of the trajectory obtained from the trajectory calculator. And a determiner for determining whether or not the determination is made.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a block diagram showing a first embodiment of the present invention. In the figure, reference numeral 2 denotes an antenna platform, 5-1, 5-2,.
Are M antennas of the same specification, fixed to the antenna platform and having directivity in the same direction,
, 6-M are the antennas 5-1 and 5-
, 5-M connected to the respective receivers, 7 are covariance matrices for calculating covariance matrices from the outputs of the receivers 6-1, 6-2,. The estimator 8 calculates eigenvalues and eigenvectors based on the covariance matrix output from the covariance matrix calculator 7.
An eigenvector calculator 9 projects a mode vector onto a noise subspace based on the eigenvalues and eigenvectors output from the eigenvalue / eigenvector calculator 8 and calculates a noise subspace projection length calculator that calculates the projection length.
Reference numeral 10 denotes a projection length minimum value calculator for obtaining the azimuth and elevation angle of the mobile radio wave source when the projection length output from the noise subspace projection length calculator 9 becomes minimum, and 11 denotes a mode vector for calculating a mode vector. A calculator, 12 is a control device, 13 is a signal processing device A, 14 is an instantaneous visual field invariable rotation driving device for rotating the antenna platform 2 while keeping the pointing direction of the antenna 5 constant, and 15 is a trajectory of a moving radio wave source. The trajectory calculator 16 is a determiner for determining the authenticity of the mobile radio wave source.

Next, the operation will be described. First, the antenna platform 2 is pointed by using the instantaneous visual field invariable rotation driving device 14 so as to direct a predetermined azimuth angle and elevation angle output from the control device 12. Here, it is assumed that there are D mutually uncorrelated multiple mobile radio sources in the instantaneous field of view of the antenna 5 about the above-mentioned predetermined azimuth and elevation. Radio waves from the plurality of mobile radio sources are received by antennas 5-1, 5-2,..., 5-M, and input to receivers 6-1, 6-2,. The outputs of the receivers 6-1, 6-2,..., 6-M are amplified,
After the frequency conversion, it is input to the covariance matrix calculator 7. The signal input to the covariance matrix calculator 7 is as shown in Expression 1.

The covariance matrix calculator 7 calculates the covariance matrix shown in Expression 2, and calculates the eigenvalue / eigenvector calculator 8
Is input to The eigenvalue / eigenvector calculator 8 calculates M eigenvalues based on the input covariance matrix, calculates eigenvectors corresponding to the respective eigenvalues, and then calculates these results by the noise subspace projection length calculator 9. Is input to

Let the above eigenvalue be λ₁, Λ_Two, ..., λ_Mage,
X the corresponding eigenvector₁, X_Two,…, X _MThen, Equation 3
The eigenvalues and eigenvectors are calculated according to
You.

Since Equation 2 is a positive definite matrix, the eigenvalue λ
₁ , λ ₂ ,..., Λ _M are all greater than zero. Receiver 6
Assuming that the standard deviation of the receiver noise is σ, Equation 4 holds from the above assumption that the D mobile radio sources are uncorrelated with each other.

The eigenvectors corresponding to the eigenvalues λ ₁ , λ ₂ ,..., Λ _D are X ₁ , X ₂ ,..., X _D, and λ _{D + 1} , λ _{D + 2} ,.
The eigenvector corresponding to the _{M X D + 1, X D} + 2, ..., if _{X M X 1, X 2,} ..., signal subspace and X _{D + 1} spanned by the X _D,
The noise subspaces spanned by X _{D + 2} ,..., X _M are mutually orthogonal complement spaces.

The mode vector calculator 11 controls the controller 1
An antenna 5 fixed to the antenna platform 2 oriented at a predetermined azimuth and elevation according to an instruction from the antenna 2
A mode vector is calculated based on the arrangement of -1, 5-2,..., 5-M.

For example, as shown in FIG. 5, the direction (z axis) of the surface of the antenna platform 2 is directed to a predetermined azimuth and elevation by an instruction from the control device 12 to the instantaneous visual field invariable rotation drive device 14. It is assumed that seven antennas are arranged on the surface (on the xy plane) of the antenna platform 2 at intervals d in both the x-axis direction and the y-axis direction.

At this time, the position coordinates of the antenna 5 are given by Equation (6).
It is represented by

[0036]

(Equation 6)

The virtual radio wave source has an azimuth based on the z-axis in FIG.
Assuming that the elevation angle exists in the directions of α and β, respectively, the mode vector calculator 11 calculates the mode vector corresponding to the virtual radio wave source based on the instruction from the control device 12 to the mode vector calculator 11, and 7 is obtained.

[0038]

(Equation 7)

In Equation 7, γ is x while fixing the z-axis in FIG.
The angle λ when the antenna 5 is rotated in the y-plane is the wavelength of the virtual radio wave source. FIG. 5 is a diagram when γ = 0, and the initial value of γ is zero.

Now, the noise subspace projection length calculator 9 calculates
A noise subspace is created based on the input eigenvalues and eigenvectors, and the mode vector calculated by the mode vector calculator 11 is projected onto the noise subspace. If this mode vector is b (α, β), the projection length _Rb expressed by Expression 8 is output from the noise subspace projection length calculator 9.

[0041]

(Equation 8)

The projection length R _b of projection length minimum value calculator 10 in the mode vector b (α, β) is alpha, obtained as a function of beta, of Group D, which gives the minimum value alpha, the value of beta, (alpha ₁₁ , β
₁₁ ), (α ₁₂ , β ₁₂ ),..., (Α _1D , β _1D ) are obtained.

Next, the controller 12 sets γ = γ ₁ ≠ 0, and the mode vector calculator 11 outputs the mode vector given by Equation 7 to the noise subspace projection length calculator 9.

Further, the control device 12 instructs the instantaneous visual field invariant rotation driving device to the rotation angle γ ₁ , and rotates the antenna platform 2 by the angle γ ₁ in the xy plane while the z axis is fixed.

Again, the processing from the antenna 5 to the projection length minimum value calculator 10 is repeated, and the outputs (α ₂₁ , β ₂₁ ), (α ₂₂ , β ₂₂ ),. _2D , β
_2D ).

If the above processing is repeated J times, DJ (α, β) combinations will be obtained, which are input to the trajectory calculator 15.

The trajectory calculator 15 obtains DJ (α, β) plots.

For example, D = 2, J = 10, and both mobile radio sources are within the instantaneous visual field of the antenna 5, ie, the antenna 5
If the beam width is within the 3 dB beam width, the locus calculator 15 obtains the plot shown in FIG. If one of the two mobile radio sources is outside the instantaneous field of view of the antenna 5,
The plot shown in FIG. 7 is obtained from the locus calculator 15. Based on the shape of the trajectory obtained from the trajectory calculator 15, the determiner 16 assumes that two true moving radio sources exist in the instantaneous visual field if the plot is almost continuous as shown in FIG. If the plots are dispersed as shown in FIG. 7, it is determined that one true mobile radio source exists in the instantaneous visual field.

In the present embodiment, since the instantaneous visual field invariable rotation drive device 14 is provided, the antenna platform 2 on which the antenna 5 is installed is simply rotated,
Without changing the array coefficient (array factor), the effect of the grating lobe can be suppressed while keeping the number and arrangement of the antennas 5 constant. As a result, it is not necessary to switch the antennas and increase the number of antennas 5. Become. Further, since the trajectory calculator 15 and the determiner 16 are provided, the direction of the true moving radio wave source within the instantaneous visual field can be measured without error.

Embodiment 2 FIG. 2 is a configuration diagram showing a second embodiment of the present invention. In the drawing, reference numeral 17 denotes a direction (z-axis) of the surface of the antenna platform 2 in a predetermined direction, and based on an instruction from the control device 12. This is an instantaneous field-of-view variation rotation drive device for rotating the surface of the antenna platform 2 so as to be shifted from the predetermined direction, and the other components are the same as those in FIG.

Next, the operation will be described. Control device 12
The antenna platform 2 is directed in a predetermined direction by the instantaneous visual field change rotation driving device 18 based on the instruction from the user.

The mode vector calculator 11 controls the controller 1
The mode vector corresponding to the virtual radio wave source when the antenna platform 2 is directed in the predetermined direction designated by 2 is calculated.

The processing from the antenna 5 to the minimum projection length calculator 10 is the same as in the first embodiment of the present invention. Then, the control device 12 is rotated by the instantaneous visual field change rotation driving device 17 so that the direction of the surface of the antenna platform 2 is deviated from the initially set direction.

The processing from the antenna 5 to the minimum projection length calculator 10 is performed again. The trajectory of the angle of the mobile radio wave source obtained by repeating such an operation is used as a trajectory calculator 1.
5, the determiner 16 determines whether or not the source is a true moving radio wave source within the instantaneous visual field based on the shape of the trajectory obtained from the trajectory calculator 15 as in the first embodiment.

[0055]

According to the first aspect of the present invention, the antenna platform is rotated by the instantaneous visual field invariant rotation driving means based on an instruction from the control means, and a predetermined mode vector is changed based on the instruction from the control means. The effect of the grating lobe caused by the antenna arrangement, that is, the position estimated as the true position of the mobile radio source, becomes large by calculating the angle trajectory of the obtained mobile radio source by the calculator. Different phenomena can be suppressed.

According to the second aspect of the present invention, the antenna platform is rotated while varying the directivity of the antenna by the instantaneous field-of-view changing rotation driving means based on an instruction from the control means, and a rotation angle command from the control means is provided. A predetermined mode vector is calculated from the mode vector calculator based on the above, and the trajectory of the obtained angle of the moving radio wave source is obtained by the trajectory calculator, so that the influence of the grating lobe caused by the antenna arrangement can be reduced. It can be suppressed as well as the effect.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of a direction finding apparatus according to the present invention.

FIG. 2 is a diagram showing a second embodiment of a direction finding apparatus according to the present invention;

FIG. 3 is a diagram showing a configuration of a conventional direction detection device.

FIG. 4 is a diagram showing an operation example of a conventional direction detection device.

FIG. 5 is a diagram showing an example of an antenna arrangement and a coordinate system of the direction finding apparatus according to the present invention.

FIG. 6 is a diagram illustrating an example of a locus of angle measurement values of a radio source obtained according to the present invention when two moving radio sources are both within the instantaneous field of view (3 dB beam width) of the antenna.

FIG. 7 is a diagram illustrating an example of a locus of angle measurement values of a radio source obtained according to the present invention when one of two mobile radio sources is out of the instantaneous field of view (3 dB beam width) of the antenna.

[Explanation of symbols]

1 orbiting satellite, 2 antenna platform, 3 signal processor B, 4 rotation drive, 5 antenna, 6
Receiver, 7 covariance matrix, 8 eigenvalue / eigenvector calculator, 9 noise subspace projection length calculator, 10 projection length minimum value calculator, 11 mode vector calculator, 12 controller, 13 signal processor A, 14 instantaneous Field-of-view invariant rotary drive, 15 trajectory calculator, 16 decision unit, 17 Instantaneous field-of-view variable rotary drive.

Claims (2)

[Claims] A plurality of antennas for receiving radio waves from a mobile radio wave source; an antenna platform having the plurality of antennas mounted so as to point in the same direction; An instantaneous visual field invariant rotation driving means for rotating the antenna platform while maintaining the direction, and a plurality of different rotation angle commands for generating the instantaneous visual field invariant rotation driving means.
Control means for supplying the respective rotation angle commands; a plurality of receivers connected to each of the plurality of antennas to which the output signals of the antennas are supplied; and a covariance matrix from the output of the receiver. A covariance matrix calculator for calculating, an eigenvalue / eigenvector calculator for calculating eigenvalues and eigenvectors based on the covariance matrix output from the covariance matrix calculator, and A mode vector calculator for calculating a mode vector based on the supplied rotation angle command and the arrangement of the plurality of antennas, and a noise portion based on the eigenvalue / eigenvector output from the eigenvalue / eigenvector calculator Project the mode vector output from the mode vector calculator into space,
A noise subspace projection length calculator for calculating the projection length, and a projection length minimum value for obtaining the azimuth and elevation of the radio source when the projection length output from the noise subspace projection length calculator is minimal A calculator, a trajectory calculator for calculating a trajectory based on the azimuth and elevation of the mobile radio source obtained from the projection length minimum value calculator for each of the rotation angle commands, and a trajectory obtained from the trajectory calculator. A direction finder for determining whether or not the trajectory is based on the shape of the trajectory to be determined by the moving radio wave source. 2. A plurality of antennas for receiving radio waves from a mobile radio wave source, an antenna platform having the plurality of antennas mounted so as to point in the same direction, and a plurality of antennas pointing in accordance with a rotation angle command. An instantaneous field-of-view variation rotation driving means for rotating the antenna platform so as to change the direction, and generating a plurality of different rotation angle commands, and supplying the respective rotation angle commands to the instantaneous field-of-view variation rotation drive means Control means for connecting to each of the plurality of antennas,
A plurality of receivers to which the output signal of the antenna is supplied,
A covariance matrix calculator for calculating a covariance matrix from the output of the receiver, an eigenvalue / eigenvector calculator for calculating eigenvalues and eigenvectors based on the covariance matrix output from the covariance matrix calculator, A mode vector calculator for calculating a mode vector based on the rotation angle command supplied from the means to the instantaneous visual field variation rotation driving means and the arrangement of the plurality of antennas, and output from the eigenvalue / eigenvector calculator. A noise subspace projection length calculator for projecting a mode vector output from the mode vector calculator onto a noise subspace extended based on eigenvalues / eigenvectors and calculating the projection length; and a noise subspace projection length calculator The projection length for obtaining the azimuth and elevation angle of the radio source when the projection length output from the minimum becomes minimum A small value calculator, a trajectory calculator for calculating a trajectory based on the azimuth and elevation of the mobile radio source obtained from the projection length minimum value calculator for each of the rotation angle commands, and the trajectory calculator A direction finder comprising a determiner for determining whether or not the trajectory is based on the moving radio wave source based on the shape of the trajectory obtained from the trajectory.