JP2896398B2 - 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 finder that uses a plurality of antennas, processes the output from each antenna by a music method, and detects arrival of radio waves from a plurality of directions arriving at the same time.

[0002]

2. Description of the Related Art The direction of arrival of an instantaneous radio wave is detected by detecting the phase difference between radio waves received by these antennas using three or more omnidirectional antennas without rotating the direction of the antenna. Some are also detectable. However, this cannot detect the direction of arrival of radio waves arriving simultaneously from a plurality of directions.

[0003] Using three or more antennas, the reception output from each antenna is converted to music (MUSIC; Multiple Sig).
nal Classification) method, it is possible to detect each direction of radio waves arriving simultaneously from multiple directions. IEEE ・ Trans.ANTENA ANDPROPAGATION vol, AP-34,
No. 3, March 1986, pp. 276-280. However, a direction finder implementing this method has not been realized yet.

An object of the present invention is to realize a direction finder using processing by the music method.

[0005]

According to the first aspect of the present invention,
N (N is an integer of 3 or more) receiving the output of the non-directional or directional antenna is supplied to each of the N receiver including a logarithmic amplifier, each of the output of the N receivers N number of A
Are converted to digital signals by an A / D converter, and the outputs of these A / D converters are converted to linear signals by N log-linear converters, respectively, and these converted outputs are output by N Fourier converters, respectively. Fourier transform is performed, and the output of the Fourier transform is processed by the data processing unit by the music method, and the arrival direction of the radio wave received by the antenna is calculated.

An odd number of antennas is desirable .

Further , in the inner product calculation of the eigenvector and the antenna voltage vector in the arithmetic processing of the music method, the detection angle area is divided, and for each of the divided areas, a predetermined angle α ° larger than the unit angle of the desired accuracy.
The inner product calculation is performed for each of them, and only a predetermined number a is selected from the smaller one of the calculation results, and the inner product is calculated for an angle corresponding to each of the a numbers for an angle smaller by α ° / 2, and the calculation result is obtained. And a predetermined number b is selected from the smaller one of the a and the inner product for each point of the desired accuracy in an area smaller than the area of the angle α by a unit angle with respect to the angle b with respect to the b. And calculate the minimum value of the calculated inner product in the region for each of the b values,
The smaller (N−
1) is selected, and a smaller estimated reception number M is selected from all of the (N-1) minimum values of the divided regions similarly processed in parallel.

[0008]

FIG. 1 shows an embodiment of the present invention.
The N's antennas 11 ₁ to 11 _N for example, a monopole antenna, are provided at equal intervals on the same circle. Reception output of the antenna 11 ₁ to 11 _N are supplied to the receiver 12 ₁ to 12 _N, respectively. Receivers 12 _{1 to} 12 _N
Is the same configuration, the one receiver 12 Stated for _one example attenuator 13- RF amplifier 14 first frequency converter 15 first intermediate frequency amplifier 16 second frequency converter 17 a second intermediate frequency It comprises a logarithmic amplifier 18 for amplification and a buffer amplifier 19. The logarithmic amplifier 18 has an input / output characteristic of a logarithmic function, and a large input tends to be saturated.

A local signal from a frequency-variable local oscillator 21 is commonly supplied to each of the first frequency converters 15 of the receivers 12 _{1 to} 12 _{N, and} a fixed frequency local oscillator is supplied to each of the second frequency converters 17. A common local signal is supplied from 22. After the outputs of the receiver 12 ₁ to 12 _N is that have been processed are converted respectively into a digital value by the respective digital processor 23 ₁ ~ 23 _N, display processing is performed by being supplied to the data processing unit 24 Music Method 25 is displayed.

[0010] Digital processor 23 ₁ ~ 23 _N are ho Isuzu same configuration, the digital processing unit 23 _1, as shown in FIG. 2, the output of the receiver 12 ₁ is converted into a digital signal by the AD converter 26 . For example, the input signal is 500kHz
And one cycle is sampled from 8 to 32, and
Convert to a bit digital signal. The output of the AD converter 26 is input to a logarithmic-linearity converter 27, where the logarithmic characteristic is converted to a linearity characteristic, that is, a digital signal linearly corresponding to the input signal of the logarithmic amplifier 18. This conversion is performed by, for example, a ROM storing the conversion characteristics.
The output of the log-linearity converter 27 is subjected to a discrete Fourier transform (DFT) by a Fourier transformer 28. The Fourier transformer 28 includes a sin / cos data ROM 29 and a multiplication accumulator 31. The multiplication accumulator 31 is an LFT for DFT operation.
A commercially available SI can be used.

The clock from the synchronous timing circuit 32 to the AD converter 26, the accumulation control of the multiplying accumulator 31, the generation of the read address of the sin / cos data ROM 29, and the latch circuit 3 of the Fourier transform result
3, a command to stop the output of the log-linearity converter 27 at the time of latching, an end signal when Fourier transforming one data, for example, 64 to 512 waves of a 500 kHz signal, and the like. . Also, the synchronization signal SYN
Outputs C and the clock signal CK, and supplies to the other digital processing unit 23 ₂ ~ 23 _N of the synchronous timing circuit 32,
All digital processing unit 23 ₁ ~ 23 _N are adapted to operate in synchronism.

A digital processing unit 23 is provided for each of the end signals.₁ 
~ 23_NData processing of all Fourier transform results
It is taken into the unit 24 and operated by the music method.
Antenna 11₁ ~ 11_NArrival direction of radio waves received by
Is calculated. The processing by the music method is described in the above literature.
But this is briefly described with reference to FIG.
You. First, as described above, the time
Data is imported (S ₁ ). Now there are M incoming radio waves
And the amplitude of the m-th radio wave is S_m(T), direction of arrival
Is φ_m, Θ_m(Φ elevation angle, θ horizontal angle)
The output voltage when received by the eye antenna is ∫S_m(Τ) β_n(Φ_m, Θ_m, T−τ) dτ. ∫ is from −∞ to + ∞. At this time,
The total voltage received by the eye antenna is V_n(T) = Σ∫S_m(Τ) β_n(Φ_m, Θ_m, T−τ) dτ + n_n(T)... (1) n_nIs noise, Σ is from m = 1 to M, ∫ is
From -∞ to + ∞. This is Fourier Transformer 28
Perform discrete Fourier transform (S_Two ). Its sampling cycle
Period is Δt, and V_nFourier for data length Q of (t)
D The result of the conversion is as follows.

[0013]

(Equation 1) ω is the angular frequency. The V _np is the frequency component with respect to time data from the time t _p of the n-th antenna to _{t p + (Q-1)} Δt. Next, a correlation matrix is created from the frequency components (data) (S ₃ ). The following is defined.

[0014]

(Equation 2) At this time, the frequency data of the reception voltage of each antenna can be approximated by the following equation.

V _np (ω) = ΣS _mp (ω) B _n (φ _m , θ
_m , ω) + W _np (ω) (3) Σ is from m = 1 to M. S _mp (ω) is the frequency spectrum of the signal, B _n (φ
_m , θ _m , ω) is the frequency spectrum of the antenna response, W
_np (ω) corresponds to the frequency spectrum of the noise, respectively. Define the vector of the following equation. V _p = _{[V 1p (ω) ... V Np} (ω) ] ^{_{T A nm = B n (φ}} m, θ m, ω) S p = _{[S 1p (ω) ... S Mp} (ω) ] ^T n = [N ₁ (ω)... _{N N} (ω)] ^T T indicates transposition. At this time, the expression (3) becomes the following expression.

V _p = AS _p + n _p (4) The correlation matrix R is defined by the following equation.

[0017]

(Equation 3) * Indicates conjugate transposition. This correlation matrix is obtained by averaging p data.

Next, the eigenvalues and eigenvectors of the correlation matrix
(S_Four ). That is, the eigenvalue decomposition of the correlation matrix R is performed.
You. N = N square matrix A is A = A^*Hermie
The correlation matrix R is a Hermitian matrix.
AV_i= Λ _iV_iEigenvalue satisfying
λ_iAnd the eigenvector V_iAnd N groups.

[0019]

(Equation 4) Is called eigenvalue decomposition. The eigenvalues are arranged in descending order.

[0020] _{λ 1> λ 2>...>} λ M> λ M + 1 ≒ λ M + 2 ≒ ... ≒ λ N = δ 2 (6) M -th in the state in which the M-number of radio waves has arrived smallest eigenvalue lambda _M smaller eigenvalue lambda _{M + 1} following are the substantially equal. The corresponding eigenvectors are e ₁ , e ₂ ,
..., and e _N. Thus determine the number M of the signal from the magnitude of the resulting eigenvalues (S _5). That is, the number M of eigenvalue signals until the magnitudes of the eigenvalues become substantially equal is estimated, and this is estimated as the number of incoming radio waves.

The eigenvectors corresponding to the N−M eigenvectors are selected from the smaller eigenvalues (S ₆ ). That is, the eigenvalues λ _{M + 1} , λ
_{M + 2,} ..., eigenvector corresponding to λ _N e _{M + 1,} e
_{M +} 2, ..., retrieves the e _N, the matrix E _N ≡ [e _{M +} 1, e
_{M +} 2, ..., make the e _N]. The inner product of the eigenvector E _N thus selected and the antenna reception voltage vector of the radio wave arriving from a certain azimuth and elevation angle is calculated, and the reciprocal is obtained (S ₇ ). That is, if an antenna voltage vector when a radio wave arrives from a certain azimuth and elevation angle is a (φ, θ),
The following quantities are obtained for each (φ, θ).

[0022]

(Equation 5) Antenna voltage vector a (φ, θ) is _{[B 1 (φ, θ, ω} ) B 2 (φ, θ, ω) ... B N (φ,
θ, ω)] ^T. In equation (7), a peak occurs in the direction of the incoming radio wave. The term of the denominator in the equation (7) is a term for normalization that eliminates the influence of changing the antenna output due to the antenna directivity (φ, θ).

M are selected in descending order of the peak of P _MU (φ, θ), and the azimuth and elevation angle at that time are set as the estimated azimuth and elevation angle of the arriving radio wave (S ₈ ). In other words, when M radio waves are arriving, M peaks appear, and φ _m and θ _{m at} which the peaks appear become the estimated azimuth and elevation angle of the arriving radio wave. Next, the intensity of each incoming radio wave is determined (S ₉ ). The intensity of the arriving radio wave is aligned with the diagonal component of (A ^* A) ^-1 (R-δ ² R ₀ ) (A ^* A) ^-1 . That is, M directions (φ ₁ θ ₁ ),
After estimating (φ ₂ θ ₂ ),... (Φ _M , θ _M ), matrix A = [a (φ ₁ , θ ₁ ) a (φ ₂ , θ ₂ ).
(Φ _M , θ _M ). Here, the intensity of the arriving radio wave (φ _m , θ _m ) is the m-th diagonal component.

In the above description, the antennas 11 _{1 to} 11 _N are omnidirectional in a horizontal plane, but may be directional. In particular, two antennas may be used if an antenna having an 8-character directivity such as a horizontal dipole is used for a vertical polarization, such as a loop antenna or an Adcock antenna, and a horizontal dipole is used for a horizontal polarization. The two antennas may be configured such that the eight-character directional characteristics are angularly shifted by 90 ° in the horizontal plane at the same position.
This is because the phase of the reception output is inverted between one directional direction and the opposite directional direction of the 8-character directional characteristic, and by using this relationship, the arrival direction of the radio wave can be obtained even with two antennas by the music method. Can be measured. Here, a line connecting the center of the N circular antenna arrangements to the antenna 11 ₁ is used as a reference line, and the angle of the line connecting the i-th antenna 11 _i from the antenna 11 ₁ and the center to the reference line is α. _Assuming that _i , the reception voltage B _i of the i-th antenna 11 _i is as follows.

[0025] B _i = D exp _{[jωr cos (θ-α i)} sin φ ] (8) D: antenna factor, r: Antenna Factor D _L radius loop antenna of the antenna arrangement circle is given by the following. _{D L = -jωN he cos (θ} -α i) he: antenna effective length, N: antenna factor D _A of turns Adcock antenna is given by the following.

[0026] _{D A = -jω he S cos (} θ-α i) S: Antenna Factor D _D of antenna spacing horizontal dipole antenna is given by the following. D _D = he sin (θ−α _i ) The antenna coefficient D to be used is substituted into Expression (8), and B ₁ (φ, θ, ω) and B ₂ (φ, θ,
ω),... B _N (φ, θ, ω), and using these, the antenna voltage vector a is determined as shown in the definition of equation (7).
By calculating (φ, θ), the calculation of equation (7) can be performed.

When using two 8-character antennas,
r = 0, N = 2, α ₂ = 90 °, B _i = D, and the radio wave arrival angle φ cannot be obtained, but the radio wave arrival direction θ can be obtained. When it is desired to detect the arrival direction of the radio wave with high accuracy in the calculation of the expression (7), if all the expressions (7) are calculated for each point of (φ, θ) with the desired accuracy, the amount of calculation becomes extremely large, and the processing time Is also longer. From this point, the following may be performed. That is, the (φ, θ) region is divided into a plurality of regions at any one of the elevation angle φ and the azimuth θ. For example, the elevation angle direction is divided into five at 18 °, and these five regions are processed in parallel. FIG. 4 shows an example of the processing. First, for φ and θ, the inner product of the eigenvector and the antenna voltage vector for each predetermined angle α °, that is, the denominator of equation (7) (hereinafter simply referred to as inner product F) is calculated. For example, α =
In the case of δ, the inner product F is calculated for φ and θ of each point of φ and θ coordinates in units of α ° = δ ° shown in FIG. 5A (S ₁ ).

From the smaller of the calculation results of the inner product F, a
An individual is selected (S ₂ ). For each point (θ, φ) for the “a” points, each inner product F of the points smaller by α ° / 2 (θ, φ) is calculated (S ₃ ). That is, for example, as shown in FIG.
= Δ, one of the a selected points (φ ₁ ,
θ ₁ ), (φ ₁ −3, θ ₁ ) and (φ ₁ , θ ₁ −
3) and (φ ₁ -3, θ ₁ -3), the inner product F at that point is calculated.

Step S_Two And the inner product of a
Top S_Three During 4a inner products with 3a inner products calculated in
B are selected from the smaller one (S_Four ). For that b
For each point (θ, φ), α ° × α ° around this point
Each point of the desired accuracy in the area inside by the desired accuracy unit
(F, θ) of the inner product F is calculated (S_Five ). α =
If the desired accuracy is 1 degree in δ, one out of b is shown in FIG. 5B.
(Φ₁ −3, θ ₁ ), Then (φ₁ −
3, θ₁ ) At the center of (δ-1) ° x (δ-1) °
Within the region, a point with unit accuracy of one degree, that is, (φ₁ −
3, θ₁ ), A point one degree apart, ie, φ₁ , Θ₁ Little
At least one of the eight points with one changed, and (φ₁ −3, θ
₁ ), A point two degrees apart, ie, φ₁ , Θ₁ At least
A total of 24 points including 10 points of each point with one changed by 2 (x in FIG. 5B)
The dot product F is calculated for each of the marked points).

With respect to each of the selected b points, a minimum value (not a minimum value) of the inner product F in an area α ° × α ° centered on the b points is obtained (S ₆ ). In the example of FIG. 5B, the points where the local minimum value can exist are (φ ₁ −1, θ ₁ ) and a point separated from the point by a total of 9 points. In this way, the drop point of the inner product F is determined with the desired accuracy, that is, in this example, with one degree of accuracy. Next, N-1 (N: the number of antennas) are selected from the smaller local minimum value obtained for the selected b points (S
₇ ).

The total number of N-1 local minimum values obtained by performing parallel processing on each divided area in this manner, in this example, the number of signals from the smaller one of 5 × (N-1), That is, only the estimated M is selected, and each is set as the direction of the incoming signal. Since the (φ, θ) region is divided into a plurality (5 in the above example), the number of a can be made relatively small. In other words, a weak radio wave has a small dip angle range of the inner product F, and a strong radio wave has a wide dip angle range of the inner product F. In particular, if the wavelength is long, the dip angle range becomes even longer. On the other hand, a plurality of points may be selected within the number of a, and the drop due to the weak radio wave may not be removed. However, the above-mentioned division eliminates the possibility of a relatively small a. Further, α may be changed so that α becomes larger as the wavelength is longer according to the detection radio wave wavelength.

The direction of arrival (φ, θ) and the intensity of the radio wave obtained as described above are displayed on the display unit 25. The display is, for example, as shown in FIG. That is, the vertical baseline 4
For one, θ is indicated by a clockwise angle, and φ is indicated by the distance to the center 42 thereof. Assuming that the radius of the display surface is r, y = rcos φcos θ x = rcos φsin θ is calculated for the angle (φ, θ) obtained by the data processing unit 24, and the x, y coordinates (from the center 42) are calculated. At the point (relative coordinates), "1" indicating the presence of an incoming radio wave or its radio wave intensity is written into the video RAM corresponding to the display surface of the display 25. Markers and scales are written in the fixed display video RAM. If the intensity of the incoming radio wave is strong and the direction of arrival is stable, the radio wave is displayed at one point,
Direction and elevation can be read correctly. If the intensity of the arriving radio wave is weak, the detection direction (φ, θ) is not constant, but fluctuates and is displayed in a distributed manner. When the display 25 is a CRT, integration is performed temporally, so that the brightness in the likely direction of arrival increases.

In this example, 0 to 360 ° of θ is set on the x-axis, the reception frequency for θ in the arrival direction is displayed as a display 43 in the y-axis direction, φ in the arrival direction is set in the y-axis direction, and the reception frequency is Is displayed as the display 44 in the x-axis direction. In this case, when the display surface is over, the display color is changed and displayed as a display 43 '. The probability of arrival can be known from the frequency distribution.

As shown in FIG. 7A, the azimuth θ and the elevation angle φ are the same as those shown in FIG. 6, and the azimuth θ is the angle with respect to the base line 41 centered on the point 42, and the elevation angle φ is the radial distance from the center 42. A display portion (hereinafter referred to as a circular display portion) 46;
A frequency distribution display unit that takes the azimuth on the horizontal axis and displays the reception frequency for each azimuth on the vertical axis (hereafter, one of the horizontal axis and vertical axis is a variable, and the other is a rectangular display unit that displays the results. 47) may be displayed side by side on the display surface 48.

An azimuth cursor 49 is displayed on the circular display section 46 as a straight line extending in the radial direction from the center 42, and a vertical azimuth cursor 51 is displayed on the square display section 47 at the azimuth angle θ indicated by the azimuth cursor 49. You. Display 2
5 is provided with an azimuth cursor setting means. When an azimuth angle θ to be instructed is input, the cursor 49,
51 is displayed. In other words, for the set azimuth angle θ, r sin θ and r cos θ are calculated, and if a line connecting this point and the center 42 is drawn, the cursor 49 is displayed. The cursor 51 is displayed by drawing a line parallel to the vertical axis from the position of the azimuth angle θ in the rectangular display unit 47 on the upper side.
When the azimuth cursor 49 or 51 is pointed to an arbitrary azimuth angle θ in this manner, the azimuth angle θ is numerically displayed on a part of the display surface 48, in the lower part in FIG. The elevation angle φ having a high degree is also displayed numerically.

As shown in FIG. 7B, the circular display section 46 and the square display section 47 are displayed side by side. In this example, the vertical display section 47 has an elevation angle of 0 to 90 ° and the horizontal axis has each elevation. An elevation angle reception number distribution may be displayed by taking the reception frequency at an angle. In this example, an elevation cursor 52 that intersects the azimuth cursor 49 at a right angle is displayed.
, An elevation cursor 53 is displayed as a horizontal straight line. An elevation angle cursor setting means is provided on the display 25, and when an arbitrary elevation angle φ is set, (r sin θ cos φ, r cos θ cos
φ), that is, the azimuth cursor 49 and the elevation cursor 52
And from this point ± (L cos θ, −L sin θ) (L
Draws a line connecting two points separated by ２ of the length of the elevation cursor 52, thereby displaying the elevation cursor 52. The elevation cursor 53 is displayed by drawing a horizontal line to the right from the set elevation angle φ in the range of 0 to 90 ° on the vertical axis. Further, the elevation angle φ designated by the elevation cursor 52 and the designated azimuth angle θ of the azimuth cursor 49 are numerically displayed on a part of the display surface 48.

The elevation cursor 53 is moved to the azimuth cursor 4.
9 without moving the elevation cursor 53 to the reference line 4
Alternatively, the user may move the upper position to indicate an arbitrary elevation angle. In this case, as the numerical display, the azimuth (θ) indicates the azimuth having the highest reception frequency at the designated elevation angle φ. As shown in FIG. 8A, the reception frequency distribution for the elevation angle 0 to 90 ° at the azimuth angle θ indicated by the azimuth cursor 49 may be displayed on the square display unit 47. As illustrated in FIG. 8B, the elevation angle cursor 52 may be pointed on the reference line 41, and the reception frequency distribution for the azimuth 0 to 360 ° at the pointed elevation angle φ may be displayed on the square display unit 47.

Alternatively, as shown in FIG. 8C, the reception frequency distribution with respect to the azimuth angle is performed by the square display unit 47, and the reception frequency distribution with respect to the elevation angle at the azimuth angle indicated by the azimuth cursor 51 is used as the square display unit 47. May be displayed side by side. Further, the _{PMU of the} formula (7) is displayed on the display 25.
(Φ, θ) (reciprocal of the inner product of the eigenvector and the antenna reception voltage vector) can be displayed using φ as a parameter. For example, as shown in FIG.
= 0 °, φ = 20 ° , φ = 40 °, the phi = 80 ° is a case of displaying the P _MU curve over 0 to 360 °. The horizontal axis indicates the azimuth, and the vertical axis indicates the level of the _PMU . Each _PMU curve is displayed by one measurement (for example, several times a second), and the state where the peak appears, that is, the state of estimation of the arrival direction by calculation appears each time, and confirms that the display of the measurement result is correct. be able to. Further, from this display, it is possible to distinguish between a case where the sharp peak appears close and the approaching direction is displayed, and a case where the approaching direction is displayed because of one relatively broad peak. That is, it is understood that the former comes from the direction from which the two radio waves approached, and the latter shows the same direction because the radio waves are the same, but the reception level is low and the approaching direction is displayed due to instability.

Further, arrival from different elevation angles can be known. For example, a value of every 0 ° to 20 ° is used as the parameter elevation angle φ.
_Does not appear enough in the _MU curve. Therefore, a _PMU curve may be displayed using the φ as a parameter for the estimated direction of arrival angle. The display of the _PMU curve may be always displayed on the square display unit 47 side by side with the display by the circular display unit 46, or the azimuth direction reception frequency distribution is always displayed on the square display unit 47, and by operating a button. A _PMU curve may be displayed temporarily instead of the frequency distribution display.
Alternatively, the display may be performed by the circular display unit 46 at all times, and the _PMU curve may be displayed instead, if necessary. FIG. 9B
As shown in the figure, the azimuth direction reception frequency distribution display and the _PMU curve display can be displayed side by side with the azimuth angle axis being common, and a common azimuth cursor 48 can be displayed.

As described above, the antenna 2 having the 8-character directional pattern
When the direction of arrival of radio waves is obtained by using a single unit, only the azimuth direction (or only the elevation direction) is obtained, but the display method can be applied to the various cases described above. It may be omitted. An arbitrary direction (elevation angle) may be indicated by the cursor on the display shown in FIG.

FIG. 10 shows vertical antennas arranged at equal angles around the circumference.
Maximum measurable antenna for the number of antennas
The experimental data for determining the interval (span) is shown. This figure 7
When the number N of antennas is odd,
If the same system has a large span and a wide frequency range
It can be seen that radio waves in the band can be detected. In the above
The arrival direction of the radio wave was obtained for the elevation angle φ and the azimuth θ,
Apply this invention even when only one of them is required
Can be. Receiver 12₁ ~ 12 _NInput a common test signal
Force to vary the phase and amplitude among the N systems.
It can be corrected by software.

[0042]

As described above, according to the present invention, since the signal is received by using the logarithmic amplifier, the level range of the received radio wave is wide, and the digital processing is returned to the linearity characteristic. Easy. In other words, the conventional ordinary direction finder that detects only the phase can perform limiter amplification, the level range of the received radio wave is wide, and the one that detects the amplitude is provided with an AGC circuit in the receiver. Although a relatively large level range of the received radio wave, in this invention it is necessary to detect the phase and amplitude, adding the AGC circuit in each receiver 12 ₁ to 12 _N in FIG. 1, the receiver 12 ₁ to 12 _The operation is performed so that there is no difference between the amplitudes of the outputs of _N , and the azimuth cannot be detected. However, in the present invention, since a logarithmic amplifier is used, simultaneous reception of weak radio waves and strong radio waves can be detected,
In addition, measurement is possible even if the level difference is large.

According to the second aspect of the present invention, since the odd number of antennas is used, the detectable frequency band is wider than that of the even number even if the antennas have substantially the same scale .

As described above, according to the present invention, the direction of arrival can be detected at high speed with a small amount of calculation. Particularly, as in the embodiment, φ = 0 ° is the outer circumference, φ = 90 °
Is displayed as the center, originally, φ = 90 °
, It is difficult to increase the azimuth resolution, and as 方位 = 0 °, the azimuth resolution can be increased, and a display matching this can be obtained.

It is possible to understand the degree of reception of each azimuth and elevation angle, to understand the certainty of the direction of the arriving radio wave, and to determine whether the radio wave is a noise radio wave or a primary radio wave. Their <br/> respectively measured radio waves coming direction, it is possible to know the probability of elevation.

[0046] Also by using the cursor, it is possible to numerically display the azimuth or elevation angle, and in that the azimuth or elevation, or to display the elevation or azimuth reception frequency distribution, and displays the elevation angle or azimuth of the maximum received power be able to. When _PMU curve is displayed
The measurement display orientation, it is possible to make such certainty and the proximity radio or unstable waves of the distinction of elevation angle.

[Brief description of the drawings]

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

2 is a block diagram showing a specific example of the digital processing unit 23 ₁ in FIG.

FIG. 3 is a flowchart showing a processing example in a data processing unit 24;

FIG. 4 is a flowchart showing an example of speeding up inner product processing in the data processing unit 24.

FIG. 5 is a view for explaining each inner product calculation point in the processing of FIG. 4;

FIG. 6 is a diagram showing a display example of a display 25.

FIG. 7 is a view showing a parallel display example of a circular display and a square display.

FIG. 8 is a diagram illustrating an example in which an azimuth (elevation angle) reception frequency distribution display based on designation of a cursor appears.

FIG. 9 is a diagram showing a display example of a _PMU curve.

FIG. 10 is an experimental data diagram showing a relationship between the number of antennas and the maximum measurable span.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kazuhiko Kaiga 4-13-2 Motonakayama, Funabashi-shi, Chiba 103 Fujimi-so 103 (56) References JP-A-62-233781 (JP, A) JP-A-59-51371 (JP, A) JP-A-1-100480 (JP, A) JP-A-1-101480 (JP, A) JP-B-55-28514 (JP, B1) RALPHO. SCHMIDT, "MULTIPLE EMITTER LO CATION AND SIGNAL PARAMETER ESTIMATION ON" IEEE TRANSACTION ON ANTENS AND P ROPAGATION, VOL. AP-34, NO3, MARCH 1986, P. 276-280 RALPHO. SCHMIDT, "MULTIPLE SOURCE DF SIGNAL PROCESSING G: AN EXPERIMENTAL SYSTEM", IEEE TRANSACTION ON ANTENAS A ND PROPAGATION, VOL. AP-34, NO3, MARCH 1986, P.E. 281-290 (58) Field surveyed (Int. Cl. ⁶ , DB name) G01S 3/00-3/74

Claims (2)

(57) [Claims] 1. N (N is an integer of 3 or more) antennas and N receptions each receiving an output of each antenna.
And the output of each of these receivers to a digital signal.
N AD converters, and N outputs for performing Fourier transform on the outputs of these AD converters, respectively.
Pieces and Fourier converter, the output of the Fourier transformer and treated with music method
To calculate the direction of arrival of the radio wave received by the antenna
Comprising a data processing unit, the Anne and eigenvectors of the data processing unit
As a means for calculating the inner product with the tenor voltage vector, the detection angle area is divided into a plurality of areas, and the divided areas are
A predetermined angle greater than the unit angle of the desired accuracy for the area
means for calculating the inner product for each α °, and a predetermined number a from the smaller one of the calculated inner products
Means for selection and α ° / 2 small for the angle for the selected a
Means for calculating the inner product with respect to the angle, and calculating each inner product calculated for these α ° / 2 smaller angles
A predetermined number b from the smaller of the selected inner products of a
Only the means to select and the angle to the selected b
In the area smaller than the area of the angle by the above unit angle
Calculate the inner product for each point of the desired accuracy in
Means and calculating for each of the above regions for the selected b
Means for calculating the minimum value of the inner product, and selecting (N-1) pieces from the smaller one of the obtained minimum values.
And all of the (N-1) minimum values selected from each of the divided areas.
Means for selecting the estimated number of received radio waves M from the smaller one from the body
And a direction finder comprising: 2. The direction finder according to claim 1, wherein N is an odd number.