JP3173455B2 - Direction finder - Google Patents

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 determining the direction of a wave propagating from a single or plural radio wave sources with high accuracy.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional direction finding apparatus. Schmidt, "M
multiple Emitter Location
andSignal Parameter Estim
ation "IEEE Trans. on Anten
na and Propagation, vol. AP
-34, no. FIG. 3 is a configuration diagram of a direction detecting device based on the content described in March 1986.

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

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 radio wave sources, and 6-1, 6-2,.
Are receivers of the same specifications for amplifying and frequency converting radio waves received by the antennas 5-1, 5-2,..., 5-M, respectively, and 7 are simultaneously sampling the outputs of the M receivers, And a covariance matrix calculator that calculates a covariance matrix by performing snapshots a plurality of times, 8 is an eigenvalue / eigenvector calculator that calculates eigenvalues and eigenvectors from the covariance matrix, and 9 is an eigenvalue and eigenvector calculator 8. A noise subspace projection length calculator that projects a mode vector onto a noise subspace spanned based on the eigenvalues and the eigenvectors, and calculates the projection length, scans the virtual wave source in space and projects the noise subspace projection length. A projection length minimum value calculator 11 for calculating the azimuth and elevation angle of the virtual wave source when the projection length output from the calculator 9 is minimized. Mode vector calculator for calculating a vector, 12 denotes a control device for instructing a predetermined rotation angle in the rotation drive device 4 and the mode vector calculator 11.

In FIG. 1, reference numeral 1 denotes an artificial satellite as an example of a radio wave source.

Next, the operation will be described. It is assumed that the number D of the radio sources 1 is smaller than the number M of the antennas 5, and the signals from the 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, the outputs of the M receivers 6 are represented by S ₁ (t), S ₂ (t),.
_{When M} (t) is used, the signal vector is represented by Expression 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)

Here, * represents a complex conjugate or a Hermitian conjugate.

The eigenvalue / eigenvector calculator 8 calculates M eigenvalues based on the obtained covariance matrix.
An eigenvector is calculated for each eigenvalue, and these eigenvalues and eigenvectors are input to the noise subspace projection length calculator 9. Let the above eigenvalues be λ ₁ , λ ₂ ,
, Λ _M , and the corresponding eigenvectors are X ₁ , X ₂ ,
.., X _M are given by Equation 3 using Equation 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 standard deviations of the receiver noises of the receiver 6 are all equal and the standard deviation is σ, Equation 4 holds from the above-mentioned assumption that D signals are uncorrelated.

[0015]

(Equation 4)

[0016] The eigenvalues _{λ 1, λ 2, ...,} X 1 the eigenvector corresponding to λ _D, X _2, ..., and _{X D, λ D + 1,} λ D + 2
, ..., λ _M are represented by X
_{D + 1, X D + 2} , ..., X 1, X 2 if X _M, ..., X _D
, X _{D + 1} , X _{D + 2} ,..., X
_The noise subspaces spanned by _M are mutually orthogonal complement spaces.

Now, when the M antennas 5 are arranged, the mode vector calculator 11 stores the data of the M antenna outputs, that is, the mode vectors, assuming that the wave source exists in the direction of a certain angle. Usually, this angle is over a predetermined range.

However, the mode vector calculator 11 generates a mode vector corresponding to an angle range centered on the azimuth and elevation designated by the controller 12, and generates the azimuth and elevation designated by the controller 12. The antenna platform 2 is directed by the rotary driving device 4.

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 10. On the other hand, the noise subspace projection length calculator 10 projects the image onto the noise subspace based on the input eigenvalues and eigenvectors. If this mode vector is a (α, β), the projection length given by Equation 5 is output from the noise subspace projection length calculator 9.

[0020]

(Equation 5)

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

(Α ₁ , β ₁ ), (α ₂ , β ₂ ),.
(Α _D , β _D ) are the angle estimation values in the direction in which the D wave sources are present.

[0023]

Since the conventional direction finding apparatus is configured as described above, if the radiation patterns of the antennas are not uniform in amplitude or phase, a (α ₁ , β ₁ ) , A (α ₂ , β ₂ ), ..., a
The projection length of (α _D , β _D ) onto the noise subspace does not always have a minimum value, so that there is a problem that a large error occurs in the estimated values of the azimuth and elevation of the D radio sources.

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

[0025]

According to a first aspect of the present invention, there is provided a direction finding apparatus comprising: M antennas having the same specifications; an antenna platform having the antenna oriented in the same direction; An instantaneous visual field invariant rotation driving device for rotating the antenna platform while keeping the same; a control device for instructing the instantaneous visual field invariant rotation driving device to perform a predetermined rotation; a signal processing device A for processing a signal from the antenna; As components of the processing device A, a receiver of the same specification connected to each of the antennas, a covariance matrix calculator for calculating a covariance matrix from an output of the receiver, and a covariance matrix calculator An eigenvalue / eigenvector calculator for calculating an eigenvalue and an eigenvector based on the output covariance matrix,
A mode vector calculator that calculates a mode vector corresponding to a virtual radio wave source based on the azimuth and elevation angle indicated by the control device and based on the antenna arrangement,
A noise subspace projection length calculator that projects the mode vector output from the mode vector calculator to a noise subspace that is based on the eigenvalues and eigenvectors output from the eigenvalue / eigenvector calculator and calculates the projection length. And a projection length minimum value calculator for obtaining an azimuth and an elevation angle of the virtual radio source when the projection length output from the noise subspace projection length calculator is minimal, and a rotation angle specified by the control device. And an average value calculator for calculating an average value of the azimuth angle and the elevation angle of the virtual radio source obtained in correspondence with the above.

Further, the direction detecting device according to the second invention includes an instantaneous visual field varying rotation driving device instead of the instantaneous visual field invariable rotating driving device according to the first invention, and an antenna platform such that the directivity directions of a plurality of antennas are varied. Is to be rotated.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a block diagram showing Embodiment 1 of the present invention. In the drawing, reference numeral 2 denotes an antenna platform, and 5-1 to 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 radio wave source when the projection length outputted from the noise subspace projection length calculator 9 becomes minimum, and 11 denotes a mode vector calculation for calculating a mode vector. Vessel, 12 is a control device, 1
3 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, 15 is an azimuth of a radio wave source,
This is an average value calculator that averages the estimated values of the elevation angles.

Next, the operation will be described. First, the antenna platform 2 is pointed to the predetermined azimuth and elevation output from the control device 12 using the instantaneous visual field invariable rotation driving device 14. It is assumed that there are D mutually uncorrelated plural radio sources in the instantaneous visual field of the antenna 5 centered on the predetermined azimuth and elevation. The radio waves from the plurality of radio points are received by antennas 5-1, 5-2,..., 5-M, and are respectively received by receivers 6-1, 6-2,.
Is input to .., 6-M
Are amplified and frequency-converted and 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 and eigenvector calculator 8 calculates M eigenvalues based on the input covariance matrix, calculates eigenvectors corresponding to the respective eigenvalues, and then calculates these results into the noise subspace projection length calculator 9. Is input to

If the above eigenvalues are λ ₁ , λ ₂ ,..., Λ _M , and the corresponding eigenvectors are X ₁ , X ₂ ,..., X _M , these eigenvalues and eigenvectors are calculated by Equation 3.

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

The eigenvalues λ _1, λ _2, ..., eigenvectors X ₁ corresponding to λ _D, X _2, ..., and _{X D, λ D + 1,} λ D + 2
,..., Λ _M are represented by X _{D + 1} , X
_{D + 2,} ..., if _{X M X 1, X 2,} ..., signal subspace and X _{D + 1} spanned by the _{X D, X D + 2,} ..., noise subspace spanned by X _M orthogonal to each other Complementary space.

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, it is assumed that 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. , Seven antennas 5 on the surface of the antenna platform 2 (on the xy plane).
Are arranged at an interval 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)

An imaginary radio wave source has an azimuth based on the Z axis in FIG.
When it is assumed that the elevation vectors are present in the directions of α and β, respectively, the mode vector calculator 11 calculates a mode vector corresponding to the virtual radio wave source based on an instruction from the control device 12 to the mode vector calculator 11. 7 is obtained.

[0038]

(Equation 7)

In Equation 7, γ is an angle when the antenna 5 is rotated in the xy plane while fixing the Z axis in FIG.
λ is the wavelength of the virtual radio source. FIG. 5 shows that 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, γ), the projection length R _b (α, β, γ) expressed by Expression 8 is output from the noise subspace projection length calculator 9.

[0041]

(Equation 8)

The projection length minimum value calculator 10 obtains the projection length R _{b of the} mode vector b (α, β, γ) as a function of α, β, γ. In this case, when γ = 0, the minimum value of R _b is obtained. The values of α and β of the D group given are (α ₁₁ , β ₁₁ ), (α ₁₂ , β ₁₂ ),
, (Α _1D , β _1D ) are obtained.

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

[0044] Further, the control device 12 from the instructed rotation angle gamma ₁ instantaneously viewing invariant rotary drive unit 14, the angle gamma ₁ antenna platform 2 in the xy plane remains fixed in the Z-axis
Just rotate.

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

If the above process is repeated J times, DJ (α, β) combinations are obtained, and these are input to the average value calculator 15.

The average calculator 15 calculates the average of (α, β) for each of the D radio wave sources. Assuming that, for example, an arithmetic mean is used in calculating the average value, the estimated values (α ＾ _i , β ＾ _i ) of the angle measurement values of each radio wave source are given by Expression 9. Here, i = 1, 2,..., D.

[0048]

(Equation 9)

FIG. 6 is a conceptual diagram for finding (α ＾ _i , β ＾ _i ) from the above combinations of DJ (α, β).
Here, i = 1, 2,..., D.

Embodiment 2 FIG. 2 is a block diagram showing a second embodiment of the present invention. In the drawing, reference numeral 16 denotes a direction in which the surface of the antenna platform 2 (Z-axis) is oriented 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 16 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 is the same as that of the first embodiment of the present invention. And
The control device 12 is rotated by the instantaneous visual field variation driving device 16 so that the direction of the surface of the antenna platform 2 is shifted from the initially set direction.

The processing from the antenna 5 to the minimum projection length calculator 10 is performed again. The average value of the angle measurement values of the D radio sources obtained by repeating such an operation is obtained by the average value calculator 15. When calculating the average value, for example, if an arithmetic average is used, the estimated value (α ＾ _i , β ＾ _i ) of the angle measurement value of each radio source is given by Expression 9. Here, i = 1, 2,..., D.

[0055]

According to the first aspect of the present invention, the antenna platform 2 is rotated by the instantaneous visual field invariable rotation driving device 14 based on an instruction from the control device 12, and a predetermined mode is set based on the instruction from the control device 12. The vector is calculated by the mode vector calculator 11 and the average value of the obtained angle measurement values of the radio wave source is obtained by the average value calculator 15, so that the radiation patterns of the M antennas are mutually irregular in amplitude and phase. Even in this case, the angle measurement accuracy of the D radio wave sources can be improved.

According to the second aspect of the present invention, the antenna platform 2 is rotated by the instantaneous visual field change rotation driving device 16 based on the instruction from the control device 12, and the predetermined mode is set based on the instruction from the control device 12. The vector is calculated by the mode vector calculator 11 and the average value of the obtained angle measurement values of the radio wave source is obtained by the average value calculator 15, so that the radiation patterns of the M antennas are mutually irregular in amplitude and phase. Even in this case, the angle measurement accuracy of the D radio wave sources can be improved.

[Brief description of the drawings]

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

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

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 conceptual diagram for obtaining an estimated value from an angle measurement value of a radio wave source obtained by the direction finding apparatus according to the present invention.

[Explanation of symbols]

1 artificial satellite, 2 antenna platform, 3 signal processing device B, 4 rotation drive device, 5 antennas, 6
Receiver, 7 covariance matrix calculator, 8 eigenvalue / eigenvector calculator, 9 noise subspace projection length calculator, 10 projection length minimum value calculator, 11 mode vector calculator, 12
Control device, 13 signal processing device A, 14 instantaneous visual field invariable rotation driving device, 15 average value calculator, 16 instantaneous visual field fluctuating rotation driving device.

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01S 3/00-3/74

Claims (2)

(57) [Claims] 1. A plurality of antennas having the same specifications for receiving radio waves from a radio wave source, an antenna platform having the plurality of antennas directed in the same direction, and a directional direction maintained by the plurality of antennas. An instantaneous visual field invariant rotation driving device for rotating the antenna platform, a control device for instructing the instantaneous visual field invariant rotation driving device to perform predetermined rotation, and a plurality of reception units of the same specification connected corresponding to the plurality of antennas, respectively. Machine, a covariance matrix calculator to calculate a covariance matrix from the output of the receiver,
An eigenvalue / eigenvector calculator for calculating an eigenvalue and an eigenvector based on a covariance matrix output from the covariance matrix calculator, and a mode based on a predetermined rotation angle provided by the control device and based on the plurality of antenna arrays. A mode vector calculator for calculating a vector,
A noise subspace projection length calculator that projects the mode vector output from the mode vector calculator to a noise subspace that is based on the eigenvalues and eigenvectors output from the eigenvalue / eigenvector calculator and calculates the projection length. And a projection length minimum value calculator for obtaining an azimuth and an elevation angle of the radio wave source when the projection length output from the noise subspace projection length calculator is minimal; and the mode vector calculator from the control device. And instructs the instantaneous visual field invariant rotation driving device to perform a rotation different from the predetermined rotation angle previously given, performs the processing from the antenna to the projection length minimum value calculator again, and performs the rotation given by the control device. And a mean value calculator for calculating an average value of the azimuth angle and the elevation angle of the radio source obtained corresponding to the angle. 2. An antenna for receiving radio waves from a radio wave source, having a plurality of antennas having the same specifications, an antenna platform having the plurality of antennas directed in the same direction, and an antenna for changing the directivity of the antennas. An instantaneous visual field fluctuation rotation driving device for rotating the platform, a control device for instructing the instant visual field fluctuation rotation driving device to perform a predetermined rotation, and a plurality of receivers of the same specification connected corresponding to each of the plurality of antennas; A covariance matrix calculator that calculates a covariance matrix from the output of the receiver, an eigenvalue / eigenvector calculator that calculates eigenvalues and eigenvectors based on the covariance matrix output from the covariance matrix, and the control device The mode vector is calculated based on the predetermined rotation angle given by And a mode vector output from the mode vector calculator to a noise subspace based on the eigenvalues and eigenvectors output from the eigenvalue / eigenvector calculator, and calculates a projection length of the mode vector. A noise subspace projection length calculator; a projection length minimum value calculator for obtaining an azimuth and an elevation angle of the radio wave source when the projection length output from the noise subspace projection length calculator is minimal; The apparatus instructs the mode vector calculator and the instantaneous visual field variation rotation drive device to rotate differently from the previously given predetermined rotation angle, and performs the processing from the antenna to the projection length minimum value calculator again. A mean value calculator for calculating an average value of the azimuth angle and the elevation angle of the radio wave source obtained corresponding to the rotation angle given by the control device. Direction finding apparatus according to claim.