JP3351341B2 - 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. 2 shows a conventional direction detecting device. By Schmidt,
"Multiple Emitter Locatio
n andSignal Parameter Est
immation "IEEE Trans. on Ant
ena 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. 3 is a diagram showing an operation example of the above-described direction finding apparatus.

In FIG. 2, reference numeral 2 denotes an antenna platform B having a plurality of antennas directed in the same direction, 3 denotes a conventional signal processing device B for performing signal processing, and 4 denotes a rotation driving device B for rotating the antenna platform B. , 5-1, 5-2,..., 5-M are antennas of the same specification for receiving radio waves from radio wave sources, 6-1, 6-2,.
-M are the antennas 5-1, 5-2,..., 5-
A receiver 7 of the same specification, which amplifies radio waves received by M and performs frequency conversion, simultaneously samples the outputs of the M receivers and performs a plurality of snapshots to calculate a covariance matrix. A variance matrix calculator 8 is an eigenvalue / eigenvector calculator for calculating eigenvalues and eigenvectors from the covariance matrix, and 9 is a mode vector in a noise subspace based on the eigenvalues and eigenvectors obtained by the eigenvalue / eigenvector calculator 8. And a noise subspace projection length calculator 10 for calculating the projection length when the projection length output from the noise subspace projection length calculator 9 by scanning the virtual wave source in space is minimized. Projection length minimum value calculator for calculating the azimuth and elevation angle of the virtual wave source, 11 is a mode vector calculator for calculating the mode vector expected by the virtual wave source, 1 Is a control device for instructing a predetermined rotation angle of the rotary drive unit 4 and the mode vector calculator 11.

In FIG. 3, 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,
Eigenvectors are 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 the angle range centered on the azimuth and the elevation angle indicated by the control device B 12, and the mode vector specified by the control device B 12. Rotating antenna platform 2 to azimuth and elevation
It shall be directed by 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, the reason why the radiation pattern of each antenna is used when calculating the actual radiation pattern and mode vector of each antenna is as follows. If different in
(Α ₁ , β ₁ ), a (α ₂ , β ₂ ), ..., a (α _D , β
The projection length of _D ) to the noise subspace does not always have a minimum value, and therefore, 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]

A direction finder according to the present invention comprises a plurality of antennas having the same specifications, a plurality of rotation driving devices A having the same specifications for rotating the antennas, and a rotation angle for each of the rotation driving devices A. A control device A for instructing,
A plurality of rotary joints of the same specifications connected to the respective outputs of the antenna, the antenna, the rotary drive device A, an antenna platform A to which the rotary joint is attached, and a rotary drive device B for rotating the antenna platform, A control device B for instructing the rotation drive device B of a rotation angle; a plurality of receivers of the same specifications connected to the rotary joints; and a covariance matrix calculation for calculating a covariance matrix from the outputs of the respective receivers An eigenvalue / eigenvector calculator for calculating eigenvalues and eigenvectors based on a covariance matrix output from the covariance matrix calculator; and a plurality of antennas based on a predetermined rotation angle given by the control device B. Mode vector that calculates the mode vector based on the And a noise part for projecting the mode vector output from the mode vector calculator to a noise subspace based on the eigenvalue and the eigenvector output from the eigenvalue / eigenvector calculator, and calculating the projection length. A spatial 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, and the control device A The rotation drive device A is again instructed of the rotation angle, and the processing from the antenna to the projection length minimum value calculator is performed. The azimuth and the azimuth of the radio wave source obtained corresponding to the rotation angle instructed by the control device A An average value calculator for calculating an average value of elevation angles is provided.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment. FIG. 1 is a block diagram showing an embodiment of the present invention.
,..., 5-M are M antennas of the same specification having directivity in the same direction, 13-1, 13-2,.
Are M rotary drive units A of the same specification for rotating the corresponding antennas 5-1 5-2,..., 5-M, and 14 are rotary drive units A, 13-1, 13-2,. 13-M control devices A, 1 for instructing a predetermined rotation angle
5-1,..., 15-M are M rotary joints having the same specification, and 17 is an antenna 5-1 5-2.
, 5-M are mounted in the same directional direction, and antenna platforms A, 6-1, 6-2,..., M rotation drive devices A, M rotary joints and control device A are mounted. 6-M are a plurality of receivers of the same specification connected to the rotary joints 15-1, 15-2,..., 15-M, respectively.
A covariance matrix calculator for calculating a covariance matrix from the outputs of 2,..., 6-M, and an eigenvalue / eigenvector calculator 8 for calculating eigenvalues and eigenvectors based on the covariance matrix output from the covariance matrix calculator 7 Unit 9 projects a mode vector onto a noise subspace based on the eigenvalues and eigenvectors output from the eigenvalue / eigenvector calculator 8, calculates a projection length of the noise subspace, and 10 denotes a noise portion. A projection length minimum value calculator for obtaining the azimuth and elevation angle of the radio source when the projection length output from the spatial projection length calculator 9 is minimum, 11 is a mode vector calculator for calculating a mode vector, and 4 is an antenna. Rotary drive devices B and 12 for rotating platform A
Is a control device B for instructing the rotation drive device B of a predetermined rotation angle, and 16 is an average value calculator for averaging the estimated values of the azimuth angle and the elevation angle of the radio wave source.

Next, the operation will be described. First, the antenna platform A 17 is turned to the predetermined azimuth and elevation outputted from the controller B 12 using the rotary drive B 4.

It is assumed that there are D mutually uncorrelated plural radio sources within the instantaneous field of view of the antenna 5 about the above-mentioned predetermined azimuth and elevation. Radio waves from the plurality of radio sources are received by antennas 5-1, 5-2,..., 5-M, and are respectively received by rotary joints 15-1, 15-15.
Receivers 6-1, 6-2 via 2,..., 15-M
.., 6-M. At this time, 14
1 of the rotation drive device A based on the rotation angle instructed by
3-1, 13-2, ..., 13-M
.., 5-M are each rotated by a predetermined rotation angle about the directivity direction as an axis.

The outputs of the receivers 6-1, 6-2,..., 6-M are amplified and frequency-converted before being 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 outputs these results to 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 from 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-mentioned assumption that the D plurality of radio sources are uncorrelated with each other.

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,} ..., 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.

In the mode vector calculator 11, the controller B
A mode vector is calculated based on the arrangement of the antennas 5-1, 5-2,..., 5-M fixed to the antenna platform A 17 oriented at a predetermined azimuth and elevation angle in accordance with the instruction from No. 12.

For example, as shown in FIG. 4, the direction (Z axis) of the surface of the antenna platform A 17 is directed to a predetermined azimuth angle and elevation angle by an instruction from the control device B 12 to the rotary drive device 4. It is assumed that seven antennas 5 are arranged at intervals d in the x-axis direction and the y-axis direction on the surface 17 (xy plane) of the antenna platform A.

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

[0037]

(Equation 6)

The virtual radio wave source has an azimuth based on the Z axis in FIG.
Assuming that the elevation angles are 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 controller B 12 to the mode vector calculator 11. , (7).

[0039]

(Equation 7)

Next, 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 (α, β) expressed by Expression 5 is output from the noise subspace projection length calculator 9.

In the projection length minimum value calculator 10, the projection length Rb of the mode vector b (α, β) is obtained as a function of α and β, and the value of the D group α and β that gives the minimum value of Rb, (α ₁₁ , Β
₁₁ ), (α ₁₂ , β ₁₂ ),..., (Α _1D , β _1D ) are calculated.

Then, a different rotation angle from the previously specified rotation angle to each of the rotation driving devices A, 13-1, 13-2,... The processing up to the minimum value calculator 10 is repeated, and the outputs (α ₂₁ , β ₂₁ ), (α ₂₂ , β ₂₂ ) of the projection length minimum value calculator 10 are calculated.
..., (α _2D , β _2D ) are obtained.

If the above process is repeated J times, DJ (α, β) combinations are obtained, and these are input to the average value calculator 16.

The average calculator 16 calculates the average of (α, β) for each of the D radio wave sources. In calculating the average value, for example, if an arithmetic average is used, the estimated values (α ＾ _i , β ＾ _i ) of the angle measurement values of each radio source are expressed by the following equation (8).
Given by Here, i = 1, 2,..., D.

[0045]

(Equation 8)

FIG. 5 is a conceptual diagram for obtaining (α ＾ _i , β ＾ _i ) from the above DJ combinations of (α, β).
Here, i = 1, 2,..., D.

[0047]

According to the present invention, the antenna 5 is driven by one of the rotary drive units A based on an instruction from the control unit 14.
By rotating by 3, it is possible to improve the angle measurement accuracy of the D radio sources even when the actual radiation pattern of the M antennas 5 and the radiation pattern of each antenna when calculating the mode vector are different.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a configuration of a conventional direction detection device.

FIG. 3 is a diagram showing an operation example of a conventional direction finding device.

FIG. 4 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. 5 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 B, 3
Signal processing device B, 4 rotation drive device B, 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, 1
2 Control device B, 13 Rotary drive device A, 14 Control device A, 15 Rotary joint, 16 Average value calculator, 17 Antenna platform A

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-8-82662 (JP, A) JP-A-8-278359 (JP, A) JP-A-10-111349 (JP, A) JP-A-11-111 295407 (JP, A) Patent 3220899 (JP, B2) Patent 3173455 (JP, B2) Patent 3189826 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01S 3/00-3 / 74

Claims (1)

(57) [Claims] 1. A plurality of antennas of the same specification for receiving radio waves from a radio wave source, and a plurality of rotation driving devices of the same specification mounted on each of the antennas and rotating the antennas while maintaining the directional direction of the antennas. A, a control device A for instructing each of the rotation drive devices A of a rotation angle, a plurality of rotary joints of the same specification connected to respective outputs of the antenna, the antenna, the rotation drive device A, and the rotary joint , A rotation driving device B for rotating the antenna platform A, a control device B for instructing the rotation driving device B to rotate, and a plurality of the same specifications connected to the rotary joint, respectively. Receiver and covariance for calculating a covariance matrix from the output of each of the receivers A matrix calculator, 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 vector calculator for calculating a mode vector based on an array of antennas, and a mode vector output from the mode vector calculator in a noise subspace based on eigenvalues and eigenvectors output from the eigenvalue / eigenvector calculator. And a noise subspace projection length calculator for calculating the projection length thereof, and an azimuth angle and an elevation angle of the radio wave source when the projection length outputted from the noise subspace projection length calculator becomes a minimum are obtained. The projection length minimum value calculator, and the control device A instructs the rotation drive device A again to indicate the rotation angle. The average value calculator that performs the processing from the antenna to the projection length minimum value calculator again, and calculates the average value of the azimuth and elevation angle of the radio wave source obtained corresponding to the rotation angle indicated by the controller A. A direction finding device characterized by comprising: