JP2005227084A - Apparatus and method for detecting electric wave arrival direction - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simultaneously detect a plurality of electric wave arrival directions, with high detection accuracy. <P>SOLUTION: When the set of the reactance value of different variable reactance elements 12-1 to 12-6 is set, each receiving signal y(t) received according to an array antenna device 100 is detected, a correlation matrix Rh<SB>zz</SB>, based on each reception signal is calculated, the calculated correlation matrix Rh<SB>zz</SB>is subjected to characteristics value decomposition, to calculate the characteristic value α<SB>m</SB>of the correlation matrix Rh<SB>zz</SB>, a correlation matrix Rh<SB>nn</SB>based on noise is calculated, on the basis of the calculated characteristic value α<SB>m</SB>; a correlation matrix Rh<SB>yy</SB>based on a transmitted radio signal is calculated, based on the two calculated correlation matrices Rh<SB>zz</SB>and Rh<SB>nn</SB>; the calculated correlation matrix Rh<SB>yy</SB>is subjected to characteristic value decomposition to calculate a characteristic vector w<SB>k</SB>, and the arrival azimuth angle of the reception signal received, using ESPRIT method, based on the calculated characteristic vector w<SB>k</SB>and selective matrices J<SB>1</SB>, J<SB>2</SB>in the ESPRIT method, corresponding to the first and second sub arrays. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a radio wave arrival direction detection apparatus and method using an array antenna that can change the directivity of an array antenna apparatus composed of a plurality of antenna elements, and more particularly to the directivity characteristics of an electronically controlled waveguide array antenna apparatus. The present invention relates to a radio wave arrival direction detection apparatus and method using an array antenna that can be adaptively changed.

  Prior art electronically controlled waveguide array antenna devices have been proposed in, for example, Patent Document 1 and Non-Patent Documents 2 and 3. The electronically controlled waveguide array antenna device includes a feed element to which a radio signal is fed, at least one non-feed element that is provided at a predetermined interval from the feed element and is not fed with a radio signal, and the non-feed element. A directivity characteristic of the array antenna can be changed by providing an array antenna including a variable reactance element connected to the feed element and changing a reactance value of the variable reactance element.

  Patent Document 2 (hereinafter referred to as a conventional example) proposes a radio wave arrival direction detection device using this electronically controlled waveguide array antenna device. In this conventional example, “the direction of arrival of radio waves is determined by detecting the maximum received signal intensity by receiving the radio waves of the transmission pulses radiated from the transmission device while changing the reception beam direction of the detection device over all azimuth angles. In the radio wave direction-of-arrival detection device to be detected, the pulse width of the transmission pulse is set to be equal to or longer than the time relating to the processing for detecting the maximum received signal intensity by changing the reception beam direction of the detection device over all azimuth angles Control for detecting the direction of radio wave arrival by detecting the rising edge of the transmission pulse and detecting the maximum received signal strength by changing the reception beam direction of the detection device over all azimuth angles from the detection point of time. An apparatus for detecting a direction of arrival of radio waves provided with a means is disclosed. Therefore, the pulse width of the transmission pulse is included in the time related to the process of detecting the arrival direction of the radio wave by changing the reception beam direction over all azimuth angles and detecting the maximum received signal strength, The direction of the maximum intensity value that is the direction of the transmitting device (that is, the direction of arrival of radio waves) is included. Therefore, there is a specific effect that the direction of the maximum received signal strength can always be accurately detected.

Japanese Patent Laid-Open No. 2001-024431 JP 2003-114268 A R. Roy et al., "ESPRIT-Estimation of signal parameters via rotational invariance techniques", IEEE Transactions on Acoustics, Speech, and Signal Processing, Vol. 37, pp. 984-995, July 1989. J. Cheng et al, "Adaptive beamforming of ESPAR antenna based on steepest gradient algorithm", IEICE Transactions on communication, Vol. E84-B, No. 7, pp.1790-1800, July 2001. T. Ohira et al., “Electronically steerable passive array radiator antennas for low-cost analog adaptive beamforming,” 2000 IEEE International Conference on Phased Array System & Technology pp. 101-104, Dana point, California, USA, May 21-25 , 2000. A. Hirata et al., "Reactance-Domain Signal Processing for ESPAR Antennas-Spatial Correlation and Correlation Matrix", IEICE Technical Report RCS2002-148, Vol. 102, No. 282, pp. 9-14, August 2002. R. O. Schmidt et al., "Multiple Emitter Location and Signal Parameter Estimation", IEEE Transactions on Ap. Vol. AP-34, No. 3, pp. 276-280, March 1986. C. Plapous et al., "Reactance-Domain MUSIC Algorithm for ESPAR Antenna", IEICE Technical Report, RCS2002-147, Vol. 102, pp 1-8, August 2002. E. Taillefer et al., "Reactance-domain MUSIC for ESPAR antennas (experiment)", The Proceedings of IEEE Wireless Communications and Networking Conference, Vol. 1, pp. 98-102, New Orleans, USA, March 16-20, 2003. T. Ohira et al., "Equivalent weight vector and array factor formulation for ESPAR antennas", IEICE Technical Report, AP2000-44, SAT2000-41, NW2000-41, July 2000. C.M.S.See, "Sensor array calibration in presence of mutual coupling and unknown sensor gains and phases", Electronics Letters, Vol. 30, No.5, pp. 373-374, March 3, 1994. M. Wax et al., "Detection of Signals by Information Theoretic Criteria", IEEE Transactions on Acoustics, Speech, and Signal Processing, Vol. ASSP-33, No. 2, pp. 387-392, April 1985. A. Lee Swindlehurst et al., "Multiple Invariance ESPRIT", IEEE Transactions on Signal Processing, Vol. 40, No 4, pp.867-881, April 1992. A. Richter et al., "CUBA-ESPRIT for angle estimation with circular uniform beam arrays", The Proceedings of Millenium Conference on Antennas & Propagation AP2000, Davos, Switzerland, April 9-14, 2000.

  However, this conventional example has a problem that the detection accuracy of the radio wave arrival direction is low and a plurality of radio wave arrival directions cannot be detected.

  An object of the present invention is to solve the above-described problems and provide a radio wave arrival direction detection apparatus and method capable of simultaneously detecting a plurality of radio wave arrival directions with higher detection accuracy than the conventional example.

According to a first aspect of the present invention, there is provided a radio wave arrival direction detecting device including a power feeding element for receiving a radio signal, a plurality of non-power feeding elements provided at a predetermined interval from the power feeding element, and the non-power feeding elements. Variable reactance elements connected to each other, and changing the reactance value of each of the variable reactance elements causes each of the non-feed elements to operate as a director or a reflector, thereby changing the directivity characteristics of the array antenna. In a radio wave arrival direction detection device that measures the arrival azimuth angle of a radio signal arriving at an array antenna using an array antenna,
The array antenna includes a first sub-array composed of a plurality of antenna elements including the feed element and at least one non-feed element, and at least the feed element positioned when the first sub-array is moved in parallel. Configuration capable of selecting a second subarray including a plurality of antenna elements including one non-feeding element and selecting all the antenna elements by the selection of the first and second subarrays. Have
The radio wave arrival direction detection device is
Detecting each received signal y (t) received according to the array antenna when a set of reactance values of the variable reactance elements different from each other is set, and calculating a correlation matrix Rh _zz based on each received signal; Based on the calculated correlation matrix Rh _zz and the selection matrices J ₁ and J ₂ of the ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques) method corresponding to the first and second subarrays, the ESPRIT method is used. And a control means for calculating the arrival azimuth angle of the received signal received by the array antenna.

In the radio wave arrival direction sensing devices, the control means, by eigenvalue decomposition of the correlation matrix Rh _zz which is the calculated to calculate the eigenvalues alpha _m of the correlation matrix Rh _zz, based on the computed eigenvalues alpha _m Noise the correlation matrix _{Rh nn} based on calculated, based on the calculated two correlation matrices _{Rh zz} and _{Rh nn,} the correlation matrix _{Rh yy} based on radio signals transmitted are calculated, the calculated correlation matrix _{Rh yy} To calculate the eigenvector w _k, and based on the calculated eigenvector w _k and the selection matrices J ₁ and J _{2 of} the ESPRIT method corresponding to the first and second subarrays, the ESPRIT method Is used to calculate the azimuth angle of the received signal received by the array antenna.

According to a second aspect of the present invention, there is provided a radio wave arrival direction detection method including a power feeding element for receiving a radio signal, a plurality of non-power feeding elements provided at a predetermined interval from the power feeding element, and the non-power feeding elements. Variable reactance elements connected to each other, and changing the reactance value of each of the variable reactance elements causes each of the non-feed elements to operate as a director or a reflector, thereby changing the directivity characteristics of the array antenna. In a radio wave arrival direction detection method for measuring the arrival azimuth angle of a radio signal arriving at an array antenna using an array antenna,
The array antenna includes a first sub-array composed of a plurality of antenna elements including the feed element and at least one non-feed element, and at least the feed element positioned when the first sub-array is moved in parallel. Configuration capable of selecting a second subarray including a plurality of antenna elements including one non-feeding element and selecting all the antenna elements by the selection of the first and second subarrays. Have
The radio wave arrival direction detection method is as follows.
Detecting each received signal y (t) received according to the array antenna when a set of reactance values of the variable reactance elements different from each other is set, and calculating a correlation matrix Rh _zz based on each received signal; A received signal received by the array antenna using the ESPRIT method based on the calculated correlation matrix Rh _zz and the selection matrices J ₁ and J _{2 of} the ESPRIT method corresponding to the first and second subarrays. The step of calculating the arrival azimuth angle of is included.

In the radio wave arrival direction detection method, the step of calculating the arrival azimuth angle of the received signal calculates the eigenvalue α _m of the correlation matrix Rh _zz by eigenvalue decomposition of the calculated correlation matrix Rh _zz , A correlation matrix Rh _nn based on noise based on the eigenvalue α _m and a correlation matrix Rh _yy based on the transmitted radio signal based on the two calculated correlation matrices Rh _zz and Rh _nn , The eigenvector w _k is calculated by eigenvalue decomposition of the calculated correlation matrix Rh _yy , and the ESPRIT selection matrixes J ₁ , J corresponding to the calculated eigenvector w _k and the first and second subarrays are calculated. ₂ , the arrival azimuth angle of the received signal received by the array antenna is calculated using the ESPRIT method.

Therefore, according to the radio wave arrival direction detecting apparatus or method according to the present invention, each received signal y (t) received according to the array antenna when a set of reactance values of the variable reactance elements different from each other is set. Detecting and calculating a correlation matrix Rh _zz based on each received signal, and calculating the calculated correlation matrix Rh _zz and selection matrices J ₁ and J _{2 of} the ESPRIT method corresponding to the first and second subarrays. Based on this, the arrival azimuth of the received signal received by the array antenna is calculated using the ESPRIT method. Therefore, a plurality of directions of arrival of radio waves can be detected simultaneously with higher detection accuracy than the conventional example.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected about the same component.

  FIG. 1 is a block diagram showing a configuration of a radio wave arrival direction detection device according to an embodiment of the present invention. As shown in FIG. 1, the radio wave direction-of-arrival detection device of this embodiment is an array which is an electronically controlled waveguide array antenna device including one feeding element A0 and six non-feeding elements A1 to A6. The antenna device 100, the wireless receiver 10, and the controller 20 are provided.

  In FIG. 1, the array antenna device 100 includes a feed element A0 and non-feed elements A1 to A6 provided on a ground conductor 11, and the feed element A0 includes six pieces provided on a circumference of a radius R. They are arranged so as to be surrounded by the non-feed elements A1 to A6. Preferably, the non-feed elements A1 to A6 are provided on the circumference of the radius R at regular intervals. Each of the feed elements A0 and the non-feed elements A1 to A6 is configured to have a length of, for example, about λ / 4 (where λ is a wavelength of a desired wave), and the radius R is λ / It is configured to be 4. The feeding point of the feeding element A0 is connected to the low noise amplifier (LNA) 1 of the wireless receiver 10 via the coaxial cable 5, and the non-feeding elements A1 to A6 are connected to the variable reactance elements 12-1 to 12-6, respectively. The reactance values of these variable reactance elements 12-1 to 12-6 are set according to a reactance value signal from the controller 20.

  Further, as shown in FIGS. 4 to 6, for example, the array antenna apparatus 100 includes a first subarray SA1 including a plurality of antenna elements including a feeding element A0 and at least one non-feeding element, and the first subarray. The feed element A0 that is positioned when moved in parallel and the second sub-array SA2 composed of a plurality of antenna elements including at least one non-feed element are selected, and the first and second sub-arrays are selected. It has the structure which can be selected so that all the antenna elements may be included by selection. This condition is a necessary condition for the array antenna apparatus for applying the ESPRIT method, and the array antenna apparatus 100 satisfies this condition.

The controller 20 is composed of a digital computer such as a computer, for example, and each received signal y received according to the array antenna apparatus 100 when a set of reactance values of the variable reactance elements 12-1 to 12-6 different from each other is set. After detecting (t), a correlation matrix Rh _zz based on each received signal is calculated, the calculated correlation matrix Rh _zz is subjected to eigenvalue decomposition, and an eigenvalue α _m of the correlation matrix Rh _zz is calculated. A noise-based correlation matrix Rh _nn is calculated based on the calculated eigenvalue α _m , and a correlation matrix Rh _yy based on the transmitted radio signal is calculated based on the two calculated correlation matrices Rh _zz and Rh _nn. the eigenvectors w _k calculated by eigenvalue decomposition of the correlation matrix Rh _yy that is the above calculation, the calculation of And eigenvectors _{w k} was, the first and on the basis of the selection matrix _J 1, _{J 2} of the ESPRIT method corresponding to the second sub-array, the arrival azimuth angle of the signal received by the array antenna using the ESPRIT method It is characterized by calculating.

  In the prior art, most of the practical issues related to signal processing are to measure and estimate a set of constant value parameters on which the received signal depends, such as in the case of delay estimation or arrival azimuth angle DoA estimation. Related. The ESPRIT method (for example, see Non-Patent Document 1) used in the present embodiment is widely adopted as a subspace-based signal processing arrangement method applicable to the estimation of the arrival azimuth angle DoA. Parameter estimation is achieved by utilizing invariance within the sensor design. Since this ESPRIT method has only a single output port, the electronically controlled waveguide array antenna device (see, for example, Non-Patent Documents 2 and 3 and Patent Document 1), the conventional algorithm related to the ESPRIT method is applied as it is. I can't do it. Since a reactance domain technique (for example, see Non-Patent Document 4) has been proposed for an electronically controlled waveguide array antenna device, the MUSIC (MUltiple SIgnal Classification) method (for example, non-patented) is used for an electronically controlled waveguide array antenna device. Conventional methods such as Reference 4 have been proposed (for example, see Non-Patent Documents 6 and 7). In the present embodiment, a method for estimating the arrival azimuth angle DoA by combining the algorithm of the ESPRIT method and the reactance domain method is disclosed.

  FIG. 2 is a longitudinal sectional view of the array antenna device 100. The feed element A0 is electrically insulated from the ground conductor 11, and the non-feed elements A1 to A6 are grounded to the ground conductor 11 at high frequency via the variable reactance elements 12-1 to 12-6. The operation of the variable reactance elements 12-1 to 12-6 will be described. For example, when the longitudinal lengths of the feeding element A0 and the non-feeding elements A1 to A6 are substantially the same, for example, the variable reactance element 12-1 Is inductive (L property), the variable reactance element 12-1 becomes an extension coil, and the electric lengths of the non-feed elements A1 to A6 are longer than those of the feed element A0, thereby functioning as a reflector. On the other hand, for example, when the variable reactance element 12-1 has capacitance (C), the variable reactance element 12-1 becomes a shortening capacitor, and the electrical length of the non-feeding element A1 becomes shorter than that of the feeding element A0. Acts as a director. The non-feed elements A2 to A6 connected to the other variable reactance elements 12-2 to 12-6 operate in the same manner.

  Therefore, in the array antenna apparatus 100 of FIG. 1, the plane directivity characteristics of the array antenna apparatus 100 are changed by changing the reactance values of the variable reactance elements 12-1 to 12-6 connected to the non-feed elements A1 to A6. Can be changed.

  In the array antenna control apparatus of FIG. 1, the feeding element A0 of the array antenna apparatus 100 receives a radio signal y (t), and the received signal y (t), which is the received radio signal, passes through the coaxial cable 5. The signal is input to the down converter 2 via the low noise amplifier 1 of the radio receiver 10, and the down converter 2 converts the input received signal into an intermediate frequency signal having a predetermined intermediate frequency, and then converts the received signal to the A / D converter 3. Output. The A / D converter 3 converts the input analog intermediate frequency signal into a digital intermediate frequency signal, and then outputs the digital intermediate frequency signal to the controller 20. Furthermore, the controller 20 calculates the arrival angle of the radio wave of the received signal by executing an arrival angle search process, which will be described in detail later, based on the input intermediate frequency signal, and outputs the result to the CRT display 21. indicate. Here, the controller 20 executes radio wave arrival direction detection processing, which will be described in detail later.

Next, a signal model in array antenna apparatus 100 will be described. The array antenna apparatus 100 includes (M + 1) elements including one feeding element A0 and M non-feeding elements A1 to AM. In the configuration example of FIGS. 1 and 3, M = 6. . As described above, the radiation pattern of the array antenna device 100 is such that the reactance values x _m (m = 1, 2,..., M) of the variable reactance elements 12-1 to 12-M connected to the non-feed elements A1 to A6. ) Controlled according to adjusting. In an actual application, the reactance value x _m can be controlled in a predetermined region, for example, from −300Ω to 300Ω. A vector represented by the following formula (1) is called a reactance vector, and is used for pattern formation of the array antenna apparatus 100. In this specification, matrices E ^* , E ^T and E ^H represent a complex conjugate matrix of matrix E, a complex transposed matrix of matrix E, and a Hermitian transposed matrix of matrix E, respectively.

As shown in FIG. 3, the array antenna apparatus 100 used in the present embodiment is a single-port monopole array antenna apparatus in which one non-feed element A1 to AM surrounds one central feed element A0. Here, the M non-feed elements Am (m = 1, 2,..., M) that symmetrically surround the feed element A0 that is an active monopole antenna are respectively reactance values x _m (m = 1, 2, .., M) variable reactance elements 12-m (m = 1, 2,..., M) are loaded, and as described above, the radiation pattern of the array antenna device 100 can be changed by adjusting these reactance values. It is. Here, reactance vector x of M reactance x _m is expressed by the following equation. In this specification, the number number of the black brackets in which the mathematical formula is imaged and the formula number of the square brackets in which the mathematical formula is input are used in combination. The formula number is assigned to the last part of the formula using the formula (1) as the formula number (there is also a formula that is not given).

[Equation 1]
x = [x ₁ , x ₂ ,..., x _M ] ^T (1)

Here, an RF signal in which D received signals u _d (t) transmitted with an arrival azimuth angle DoA of θ _d (d = 1, 2,..., D) are incident on the array antenna apparatus 100 is expressed by the following equation. It is represented by

[Equation 2]
s (t) = [s ₀ (t), s ₁ (t),..., s _M (t)] (2)

Here, s _m (t) is a radio signal incident on the m-th antenna element Am. At this time, the radio signal s (t) is expressed by the following equation (see, for example, Non-Patent Document 2).

Here, a (θ _d ) is a directivity vector represented by the following equation.

  Here, φm expressed by the following equation is an angular position of the m-th antenna element Am with respect to an arbitrary axis. In FIGS. 1 and 3, the direction from the feeding element A0 to the non-feeding element A1 is the X direction, which is the reference axis for angle calculation (θ = 0 °).

[Equation 3]
φm = (2π / M) (m−1), (m = 0, 1,..., M) (5)

  At this time, the received signal y (t) received by the array antenna apparatus 100 is expressed by the following equation.

  Here, n (t) is additional white Gaussian noise, and i is a radio current vector. The current vector i is expressed by the following equation.

[Equation 4]
i = V _s (Z + X) ⁻¹ u ₀ (7)

  Here, X is a reactance matrix expressed by the following equation.

[Equation 5]
X = diag ([50, jx ₁ , jx ₂ ,..., Jx _M ]) (8)

Z is an impedance matrix, z _s = 50Ω is an input impedance of the receiver, and the (M + 1) -dimensional vector u ₀ is expressed by the following equation.

[Equation 6]
u ₀ = [1, 0,..., 0] ^T (9)

  Next, a method for applying the algorithm of the ESPRIT method to the array antenna apparatus 100 will be described below. The ESPRIT algorithm achieves a significant reduction in computational complexity by imposing constraints on the sensor array configuration. That is, the array must possess displacement invariance (see, for example, Non-Patent Document 1). Application to the array antenna device 100, which is an electronically controlled waveguide array antenna device, meets this standard because its shape is a regular hexagon of 7 elements. Therefore, array antenna apparatus 100 according to the present embodiment can be divided into two subarrays that are translationally separated according to movement vector Δ. That is, in the array antenna device 100 which is an electronically controlled waveguide array antenna device, as will be described in detail later, in the array antenna device 100 including a plurality of antenna elements, the first including a plurality of antenna elements including the feeding element A0. Subarray forming matrices J1 and J2 formed on the basis of the second set of antenna elements including the feed element A0 when the first set is translated by the movement vector Δ. Use the algorithm of ESPRIT method.

In practice, several parameters are required prior to the application of the ESPRIT algorithm. In particular, in the case of the array antenna device 100 which is an electronically controlled waveguide array antenna device, a matrix of the current vector I _current is necessary. I _current embodies the characteristics of the antenna configuration and must be obtained using several calibration techniques (see, for example, Non-Patent Document 9). The current vector I _current is expressed by the following equation.

[Equation 7]
I ^T = [i ₀ ^T , i ₁ ,..., I _M ^T ] (10)

Here, i _m ^T corresponds to a current vector related to the m-th reactance value set among the M + 1 reactance value sets having different directions of the main beams having directivity characteristics. Second, an estimated value from the measured value of the correlation matrix R _zz of the received signal is required. Here, z is a received signal matrix and is represented by the following equation.

[Equation 8]
z = [y ₁ , y ₂ ,..., y _{M + 1} ] ^T (11)

Note that time dependency is excluded for simplification of the equation. The received signal y _i represents the received signal of the antenna output measured when using the i th reactance value set. The vector z is constructed according to a reactance domain technique that allows the calculation of a correlation matrix with a single output port as described in [4] and [6].

Next, algorithm steps different from those of the conventional ESPRIT method will be described below. First, (M + 1) reactance value sets are selected in advance. For each of the reactance value sets {x ⁽¹⁾ , x ⁽²⁾ ,..., X ^{(M + 1)} }, the reception signal y _i of the corresponding antenna output is measured, and (M + 1) × 1 expressed by the following equation: An output vector is obtained.

[Equation 9]
z = [y ₁ , y ₂ ,..., y _{M + 1} ] ^T (12)

Therefore, the correlation matrix R _zz between the received signals can be calculated using the following equation.

[Equation 10]
^{_{R zz = E [zz H]}} = I current T AR uu A H I current * + R nn (13)

Here, E [•] is an operator of a statistical expectation value (which means an average value (time average value) for a predetermined time period). Second, an estimate of the noise correlation matrix represented by Rh _m is given according to known Akaike information criterion represented by the following formula (AIC) (e.g., Non-Patent Document 10 reference.).

[Equation 11]
Rh _nn = σh ² I _{M + 1} (14)

Here, I _{M + 1} represents a unit matrix of (M + 1) × (M + 1), and σh ² is expressed by the following equation.

Here, D is the number of received signals, and λ _i is an eigenvalue of the correlation matrix R _zz . The ESPRIT method is based on subspace decomposition of the signal correlation matrix. It is therefore necessary to find a correlation matrix that contains the most interesting data about the signal. Therefore, the following sub-space E _{s of the} received signal using a modified correlation matrix R _yy of the received signal (ie, related to the signal from which the noise is removed from the received signal, ie, the signal transmitted from the transmitting station): An estimate of is obtained.

[Equation 12]
R _yy = (I _current ^T ) ⁻¹ (R _zz −Rh _nn ) I _current ^T (16)

The subspace E _s of the received signal is formed by extending with eigenvectors corresponding to D maximum eigenvalues of the _{eigendecomposition} of the correlation matrix R _yy , and is divided according to the following equation.

  4A is a plan view showing a set S1a of antenna elements of the array antenna apparatus 100 used in the radio wave arrival direction detection method using the ESPRIT method according to the present embodiment, and FIG. 4B is the array antenna apparatus. It is a top view which shows set S1b of 100 antenna elements. Hereinafter, the set S1a and the set S1b are collectively referred to as a set S1, and the same applies to the sets S2 and S3. FIG. 5A is a plan view showing an antenna element set S2a of the array antenna apparatus 100 used in the radio wave arrival direction detection method using the ESPRIT method according to the present embodiment, and FIG. 3 is a plan view showing an antenna element set S2b of the antenna device 100. FIG. Further, FIG. 6A is a plan view showing an antenna element set S3a of the array antenna apparatus 100 used in the radio wave arrival direction detection method using the ESPRIT method according to the present embodiment, and FIG. 3 is a plan view showing an antenna element set S3b of the antenna device 100. FIG.

Here, J ₁ and J ₂ are selection matrices that depend on subarray division. One of the important parameters when applying the algorithm of the ESPRIT method to the array antenna apparatus 100 which is an electronically controlled waveguide array antenna apparatus is selection of subarray division. Subarray division is embodied in accordance with the selection matrix _{J 1} and _{J 2} corresponding respectively to the sub-array SA1, SA2. These selection matrices J ₁ and J ₂ represent the movement invariance held by the electronically controlled waveguide array antenna device. In the array antenna apparatus 100, three sets S1, S2, and S3 are possible. Here, in the subarray configuration in the set S1a, it is possible to obtain a selection matrix J ₁ and J ₂ of the formula. In the subarray arrangement in the set S 1 b, may be elements of the selection matrix J ₁ and J ₂ are obtained so as to opposite to each other.

Here, selection matrix _{J 1} is picked up so as to correspond to a row of the selection matrix _{J 1} antenna elements {A0, A3, A4, A5} in the subarrays SA1, the original seven antenna elements A0 to A6 the selection matrix the columns of J ₁ can be obtained in correspondence. The antenna elements in the selection matrix _{J 2} is subarray SA1 {A0, A1, A2, A6} pick up to correspond to a row of the selection matrix _{J 1} to the original seven antenna elements A0 to the select A6 matrix J It can be obtained corresponding to _one column. The vector Δ representing the movement invariance between the two subarrays SA1 and SA2 affects the estimation of the arrival azimuth angle DoA, and in particular, the azimuth angle reference value θ _ref value in the expression of the arrival azimuth angle DoA estimation value described later. It is an important parameter.

  The arrival azimuth angle DoA estimated value θk (set name) corresponding to these sets has the relationship of the following equation (the unit is degrees).

[Equation 13]
θ _k (set S1b) = − θ _k (set S1a) (20)
[Formula 14]
θ _k (set S2b) = 120 + −θ _k (set S2a) (21)
[Equation 15]
θ _k (set S3b) = − 120−θ _k (set S3a) (22)

Here, in the set S2a, the feeding element A0 and the non-feeding elements A4, A5, and A6 are selected to form the subarray SA1, and the feeding element A0 and the non-feeding elements A1, A2, and A3 are selected to set the subarray SA2. It is composed. In the set S2b, contrary to the selection of the sub-array in the set S2a, the feed element A0 and the non-feed elements A1, A2, A3 are selected to form the sub-array SA1, and the feed element A0 and the non-feed elements A4, A5 are selected. Sub-array SA2 is configured by selecting A6. The selection matrices J ₁ and J ₂ in this set S2a are expressed by the following equations. In the subarray arrangement in the set S2b, it can be elements of the selection matrix J ₁ and J ₂ are obtained so as to opposite to each other.

The selection matrices J ₁ and J ₂ in the set S3a are expressed by the following equations. In the subarray arrangement in the set S3b, it can be elements of the selection matrix J ₁ and J ₂ are obtained so as to opposite to each other.

FIG. 7A is a plan view showing the subarray SA1 in the three-element linear array antenna device according to the first modification used in the radio wave arrival direction detection method using the ESPRIT method according to the present embodiment. ) Is a plan view showing a sub-array SA2 in the three-element linear array antenna device. The selection matrices J ₁ and J ₂ in this case are expressed by the following equations. In the following various modifications, A0 is a feeding element, and other A1 to AM are non-feeding elements.

FIG. 8A is a plan view showing the sub-array SA1 in the 5-element linear array antenna device according to the second modification used in the radio wave arrival direction detection method using the ESPRIT method according to the present embodiment. ) Is a plan view showing a sub-array SA2 in the 5-element linear array antenna device. The selection matrices J ₁ and J ₂ in this case are expressed by the following equations.

FIG. 9A is a plan view showing the sub-array SA1 in the 6-element two-dimensional array antenna device according to the third modification used in the radio wave arrival direction detection method using the ESPRIT method according to the present embodiment. b) is a plan view showing the sub-array SA2 in the six-element two-dimensional array antenna device. The selection matrices J ₁ and J ₂ in this case are expressed by the following equations.

FIG. 10A is a plan view showing a sub-array SA1 in a 6-element two-dimensional array antenna device according to a fourth modification used in the radio wave arrival direction detection method using the ESPRIT method according to the present embodiment. b) is a plan view showing the sub-array SA2 in the six-element two-dimensional array antenna device. The selection matrices J ₁ and J ₂ in this case are expressed by the following equations.

Further, a linear array antenna apparatus to which the algorithm of the ESPRIT method can be applied will be considered in detail. FIG. 11 depicts a seven-element linear array antenna apparatus with an azimuth reference axis that is bisected at the center of the array and perpendicular to the line formed by the antenna elements. On the other hand, in the case of the array antenna device 100 which is an electronically controlled waveguide array antenna device, the azimuth reference axis is not the same, and the parasitic element A1 is used for this purpose, as shown in FIGS. Furthermore, the azimuth angle reference value θ _ref depends on the directionality of the movement vector Δ. For example, when the configuration of the set S1a illustrated in FIG. 4A is used, the movement vector Δ is perpendicular to the azimuth reference axis of the linear array antenna apparatus, and thus the azimuth reference value θ _ref is obtained by this function. It becomes 90 degrees in balance with. FIG. 12 summarizes the azimuth reference value θ _{ref according} to the directionality of the movement vector Δ. Here, the arrow corresponds to the movement vector Δ and is shown in FIG. 12 corresponding to each set.

  Next, based on the partial matrices Ex and Ey corresponding to the subspaces of the two subarrays, eigenvalue division is calculated as in the following equation.

∧ is a diagonal matrix containing the eigenvalues of E _xy . At this time, the matrix E is represented by the following equation.

Here, the matrix E _ij is a D × D submatrix. Next, the eigenvalue of the following equation Ψ is calculated, and φk as its element can be calculated.

[Equation 16]
Ψ = −E ₁₂ E ₂₂ (37)

Finally, the estimated value θ _k of the arrival azimuth angle DoA is expressed by the following equation.

[Equation 17]
θ _k = ± | sin ⁻¹ ((c / (w ₀ ‖Δ‖)) angle (φ _k )) + θ _ref |
(38)

Here, angle (·) defines the argument of the element φ _k of the eigenvalue of Ψ, ω ₀ is the frequency of the received signal, the constant c is the propagation speed, and ‖Δ‖ is the norm of the movement vector Δ In the array antenna device 100 which is an electronically controlled waveguide array antenna device, it is expressed by the following equation.

[Equation 18]
‖Δ‖ = R = λ / 4 (39)

  Further, details of processing steps of the radio wave arrival direction detection method using the ESPRIT method according to the present embodiment, which is executed by the controller 20 of FIG. 1, will be described below. Here, the radio wave arrival direction detection processing includes the following pre-processing and arrival azimuth calculation processing.

<Pretreatment>
(Step ST 1) M + 1 reactance value sets {x ⁽¹⁾ , x ⁽²⁾ ,..., X ^{(M + 1)} } having different main beam directions are selected and stored in a partial memory in the controller 20. In this embodiment, the degree of freedom is the number of elements M, and the arrival azimuth angle DoA can be calculated by using M + 1 reactance value sets.
(Step ST2) A current matrix of the following equation is calculated using a known calibration method (for example, see Non-Patent Document 4) and stored in a partial memory in the controller 20. Here, the current vector _{i m} is, M + 1 single reactance value set ^{{x (1), x (} 2), ..., x (M + 1)} is the current value on the feed element A0 of each.

[Equation 19]
^{_{I T current = [i 1 T}} , i 2 T, ..., i M + 1 T] T (40)

<Arrival azimuth calculation processing>
(Step ST11) For each of the M + 1 reactance value sets, the reception signal y _i (m = 1, 2,..., M + 1) from the antenna apparatus 100 is received to form a reception signal vector z of the following equation: And is stored in a partial memory in the controller 20.

[Equation 20]
z = [y ₁ , y ₂ ,..., y _{M + 1} ] ^T (41)

(Step ST12) Next, a correlation matrix Rhzz is calculated using the following equation based on the measured received signal vector z.

[Equation 21]
Rh _zz = zz ^H (42)

(Step ST13) Further, eigenvalue decomposition of the correlation matrix Rhzz represented by the following equation is performed to determine eigenvalues α _{1 to} α _D (where D is the number of received signals incident on the array antenna apparatus 100, and D < M + 1, and the number of signals Dd of the desired wave is calculated by subtracting 1 from the number of eigenvectors (corresponding to the number of elements in the electronically controlled waveguide array antenna device).

Here, the eigenvalues α _{1 to} α _D are given by the following equations. V _k is an eigenvector.

[Equation 22]
α ₁ ≧ α ₂ ≧ ... ≧ α _D ≧ ... ≧ α _{M + 1} (44)

(Step ST14) Next, a noise correlation matrix Rh _nn is calculated using the following equation.

[Equation 23]
Rh _nn = σh ² I _{M + 1} (45)

Here, I _{M + 1} is a unit matrix of (M + 1) × (M + 1). The noise power σh ² is expressed by the following equation.

(Step ST15) Next, a correlation matrix Ryy considering the current vector is calculated using the following equation.

[Equation 24]
R _yy = (I ^T _current ) ⁻¹ (Rh _zz −Rh _nn ) I ^T _current (47)

(Step ST16) Next, eigenvalue decomposition of the correlation matrix R _yy expressed by the following equation is executed to calculate eigenvalues β _{1 to} β _{M + 1} and eigenvector w _k .

Here, the eigenvalues β _{1 to} β _{M + 1} are expressed by the following equations. W _k is an eigenvector.

[Equation 25]
β ₁ ≧ β ₂ ≧ ... ≧ β _D ≧ ... ≧ β _{M + 1} (49)

(Step ST17) Next, matrices E _x and E _y corresponding to the subarray are calculated using the following equation.

here,
[Equation 26]
E _s = [w ₁ , w ₂ ,..., W _D ] (51)

(Step ST18) Next, eigenvalue decomposition of the matrix Exy of the following equation is performed to calculate the eigenvalue matrix E.

here,
[Equation 27]
E = [e ₁ , e ₂ ,..., E _2D ] (55)
[Equation 28]
Λ = diag ([λ ₁ , λ ₂ ,..., Λ _2D ]), (λ ₁ ≧ λ ₂ ≧... ≧ λ _2D ) (56)

Here, the eigenvalue matrix E is divided into four sub-matrices as in the following equation, and the sub-matrices E ₁₂ and E ₂₂ are calculated. E _ij is a D × D sub-matrix.

(Step ST19) Next, the following matrix Ψ is calculated.

[Equation 29]
Ψ = −E ₁₂ E ₂₂ (58)

(Step ST20) Next, eigenvalue decomposition is performed on the following matrix Ψ to calculate eigenvalues φ _k (k = 1, 2,..., D). It should be noted that, _{u k} is the eigenvector.

(Step ST21) Next, based on the calculated eigenvalue φ _k (k = 1, 2,..., D), the arrival azimuth angle θ _k is calculated using the following equation.

[Equation 30]
θh _k = ± | sin ⁻¹ (c / (w ₀ ‖Δ‖) angle (φ _k )) + θ _ref | (60)

Here, c = 3 × 10 ⁸ [m × s ⁻¹ ], and ‖Δ‖ = λ / 4 (in the case of a seven-element electronically controlled waveguide array antenna device, λ = c / f. ), W ₀ = 2πf (in the simulation, f = 2.4 GHz), angle (φ _k ) is an angle corresponding to the eigenvalue φ _k , and θ _ref = π / 2 (for example, in the case of the set S1) It is.

As described above, in this embodiment, the controller 20 sets the array antenna device when reactance value sets of the variable reactance elements 12-1 to 12-6 different from each other are set in the radio wave arrival direction detection processing. After detecting each received signal y (t) received according to 100, a correlation matrix Rh _zz based on each received signal is calculated, the calculated correlation matrix Rh _zz is subjected to eigenvalue decomposition, and the correlation matrix Rh _zz The eigenvalue α _m is calculated, the noise-based correlation matrix Rh _nn is calculated based on the calculated eigenvalue α _m , and the transmitted radio signal is calculated based on the two calculated correlation matrices Rh _zz and Rh _nn the correlation matrix _{Rh yy} calculated based on the eigenvectors _{w k} by eigenvalue decomposition of the correlation matrix _{Rh yy} which is the calculated Calculated, the the calculated eigenvectors _{w k,} the first and on the basis of the selection matrix _J 1, _{J 2} of the ESPRIT method corresponding to the second sub-array, which is received by the array antenna using the ESPRIT method Calculate the arrival azimuth of the received signal.

  The present inventors performed simulation using the radio wave arrival direction detection device of FIG. 1, and the results will be described below.

In the simulation, for example, the SNR rate was set to 10 dB and 5000 snapshots were used. The range of the number of signals that can be estimated is discussed in Non-Patent Document 11. When the number of subarrays is 2, the upper limit value d _{max of the} number of signals is the number of elements per subarray (that is, m = 4 in the embodiment). Simulations show that up to three signals can be identified that are incident on the antenna simultaneously. This algorithm has the ability to detect up to four signals, but in the case of an electronically controlled waveguide array antenna device, only three elements per subarray are considered due to overlapping subarrays. Table 1 shows that three signals can be identified and their arrival azimuth angle DoA can be estimated.

First, the angle reference value θ _ref was checked. The angle reference value θ _ref is associated with a selected set of subarrays. Therefore, the first simulation set was run to verify this fact. The value obtained according to the simulation agreed with the expected value in FIG.

  Next, the cover sector in the simulation will be described below. This second simulation determines the cover zone of the electronically controlled waveguide array antenna device, i.e., the angular range in which the estimation of the arrival azimuth angle DoA is available and reliable (hereinafter referred to as the cover sector). To do. As expected, the cover sector depends on the subarray partitioning employed by this algorithm. Table 2 summarizes the effective range sectors of arrival azimuth angle DoA by subarray division.

  FIG. 14 is a graph showing a simulation result of the radio wave arrival direction detection apparatus using the ESPRIT method according to the present embodiment and showing an azimuth angle error with respect to the arrival azimuth angle DoA in the set S1a. FIG. 15 is a graph showing a simulation result of the radio wave arrival direction detection apparatus using the ESPRIT method according to the present embodiment and showing an azimuth angle error with respect to the arrival azimuth angle DoA in the set S1b.

  The graphs shown in FIGS. 14 and 15 define a range in which the algorithm of the ESPRIT method is most efficient using the subarray division set S1a and the set S1b, respectively. The first point observed from both graphs is that the quality of the estimation of the arrival azimuth angle DoA depends on the angle value. In FIG. 14, it can be seen that the magnitude of the error increases about 10 times for the received signal having the broadside angle (angles of approximately 0 ° to 30 ° and 140 ° to 180 °). It can also be seen that the antenna does not have an effective range of 360 ° arrival azimuth DoA. This is because the algorithm of the ESPRIT method is implemented to make the electronically controlled waveguide array antenna device resemble a linear array antenna that can only detect signals within the range of 0 ° to 180 °. In short, it can be said that the estimation accuracy of the arrival azimuth angle DoA brought about by the algorithm of the ESPRIT method when applied to the electronically controlled waveguide array antenna device depends on the angle of the incident signal. Therefore, in the next simulation, the sector zone is reduced as shown in Table 3 below. Table 3 summarizes the effective operation zones of the electronically controlled waveguide array antenna device by subarray division.

  Next, a simulation result of the performance of the radio wave arrival direction detection device according to the present embodiment will be described. In the third simulation, the performance of the algorithm of the ESPRIT method is examined. Here, consider a single received signal incident on the array with an incoming azimuth angle DoA ranging from 20 ° to 160 °. The subarray division used for this simulation is set S1a. After 10,000 iterations, the error statistic of the output signal assumes that the incoming azimuth angle θ of the received signal changes from 20 ° to 160 ° in increments of 5 ° and that the signal and additional noise are generated randomly. Check the amount. In this statistical analysis, a three-dimensional cumulative distribution function (CDF) of an error magnitude expressed by the following equation due to fluctuations in the input signal is employed.

[Equation 31]
Error Error = | θ−θh | (61)

  FIG. 16 is a simulation result of the radio wave arrival direction detection apparatus using the ESPRIT method according to the present embodiment, and the CDF (three-dimensional cumulative distribution function) of the azimuth error with respect to the arrival azimuth angle DoA when SNR = −5 dB. It is a graph which shows a curve. FIG. 17 is a simulation result of the radio wave arrival direction detection device using the ESPRIT method according to the present embodiment, and is a CDF (three-dimensional cumulative distribution function) of the azimuth error with respect to the arrival azimuth angle DoA when SNR = 0 dB. ) Is a graph showing a curve. Further, FIG. 18 shows a simulation result of the radio wave arrival direction detection apparatus using the ESPRIT method according to the present embodiment. The CDF (three-dimensional cumulative distribution function of the azimuth error with respect to the arrival azimuth angle DoA when SNR = 10 dB. ) Is a graph showing a curve.

  That is, FIG. 16 to FIG. 18 are isolines of the CDF curve, that is, graphs depicting values of the following expression with respect to a predetermined arrival azimuth angle θ, and are expressed in percentage.

[Formula 32]
p [error = | θ−θh | ≦ value _Error (62)

  As is apparent from FIGS. 16 to 18, the simulation result shows that, for example, in the case of a signal incident on the array in an angle range of 50 ° to 130 °, this graph has a probability of obtaining an accuracy of ± 2 ° of 80%. It shows that there is. Furthermore, the edge effect mentioned above can also be observed. In fact, for an angle on the edge (less than 40 ° and greater than 140 °), the probability of obtaining an estimation accuracy within 2 ° error is reduced to 40%.

  Next, the influence of SNR will be considered below. In the fourth simulation, how sensitive the ESPRIT algorithm is to noise was evaluated.

  FIG. 16 is a simulation result of the radio wave arrival direction detection apparatus using the ESPRIT method according to the present embodiment, and the CDF (three-dimensional cumulative distribution function) of the azimuth error with respect to the arrival azimuth angle DoA when SNR = −5 dB. It is a graph which shows a curve. FIG. 17 is a simulation result of the radio wave arrival direction detection device using the ESPRIT method according to the present embodiment, and is a CDF (three-dimensional cumulative distribution function) of the azimuth error with respect to the arrival azimuth angle DoA when SNR = 0 dB. ) Is a graph showing a curve. Further, FIG. 18 shows a simulation result of the radio wave arrival direction detection apparatus using the ESPRIT method according to the present embodiment. The CDF (three-dimensional cumulative distribution function of the azimuth error with respect to the arrival azimuth angle DoA when SNR = 10 dB. ) Is a graph showing a curve.

  That is, FIGS. 16 and 17 show error subdivision at SNR of −5 dB and 0 dB, respectively. Also, FIG. 18 must be considered. Note that the received signal is incident on the antenna at 60 ° and the assumed accuracy is within 2 ° error. From this, the simulation results can be summarized as shown in Table 4.

  Just quoting this example, it can be said that the estimation is very sensitive to noise. It can also be seen that the estimation accuracy increases as the noise decreases.

  Further, the influence of the number of samples will be described below. The purpose in the fifth simulation is to determine how much the estimation accuracy of the arrival azimuth angle DoA changes according to the number of samples of the signal. FIG. 19 is a graph showing a simulation result of the radio wave arrival direction detection apparatus using the ESPRIT method according to the present embodiment and showing an azimuth angle error with respect to the number of samples when the arrival azimuth angle θ = 65 °.

That is, FIG. 19 considers one signal incident on the array antenna apparatus 100 at an arrival azimuth angle DoA of 65 °. It can be seen that the minimum number of signal samples to use depends on the required estimation accuracy, for example, if the desired accuracy is ± 0.5 °, at least 2000 samples are required. In FIGS. 20 through 26, used in the simulation of a radio wave arrival direction detection apparatus using the ESPRIT method according to the present embodiment, the radiation pattern corresponding to the current i _m for each reactance value set shown in the following table P ( A directivity diagram showing i _m ^T ) is shown.

Seven sets of reactance values x _mk (m = 0, 1, 2,..., 6; k = 1, 2,..., 6) of the variable reactance elements 12-1 to 12-6 shown in Table 5 are: A set for generating one omni pattern and a set for generating six sector patterns in the direction from the feed element A0 to the non-feed elements A1 to A6 are included. In the present embodiment, the above seven patterns are used. However, the present invention is not limited to this, and a plurality of predetermined patterns may be used. In Table 1, the maximum value and the minimum value mean the maximum value and the minimum value of the movable range of each reactance value of the loaded variable reactance elements 12-1 to 12-6, respectively. In the present embodiment, the sequence signal generator (not shown) of the radio transmitter on the transmission side sandwiches a predetermined guard time with each pattern shown in Table 5, and each P symbol (for example, 2 msec) ) Are sequentially generated, and a correlation matrix of the received signal including the sequence signal generated by the sequence signal generator is calculated.

  As described above, in the present embodiment, the application of the algorithm of the ESPRIT method to the electronically controlled waveguide array antenna device has been proposed. Although the electronically controlled waveguide array antenna device was not designed for the algorithm of the ESPRIT method, this application was possible. The ESPRIT algorithm requires movement invariance within the array configuration, which is a strong constraint on the antenna geometry. The estimation of the arrival azimuth angle DoA can be achieved because of the seven-element regular hexagonal electronically controlled waveguide array antenna device. In fact, DoA estimation can be determined by utilizing the fundamental translational invariance designed into an array and combining the algorithm of the ESPRIT method with the reactance domain method. The electronically controlled waveguide array antenna apparatus can detect any signal within the 360 ° cover area, but if the modified ESPRIT algorithm according to the present embodiment is applied, the cover area is set to the entire azimuth sector. Can be reduced to a half of the sector. Furthermore, the simulation results show that the performance of this algorithm is related to the angle value incident on the array so that some edge effect is observed with respect to the angle around the limit value of the cover sector. . This simulation result is predictable because the technology previously designed for linear array antennas has been adapted to electronically controlled waveguide array antenna devices. In addition, according to the present embodiment, the probability of achieving the estimation of the arrival azimuth angle DoA with an accuracy of ± 2 ° in the angle range of 50 ° to 130 ° with respect to one signal incident on the electronically controlled waveguide array antenna device. Shows an excellent result of 80% (where the sub-array split set S1a is used and SNR = 10 dB).

As described above, according to the radio wave arrival direction detecting apparatus or method according to the present invention, each received signal y (t) received according to the array antenna when a set of reactance values of different variable reactance elements is set. ) And the correlation matrix Rh _zz based on each received signal is calculated, and the calculated correlation matrix Rh _zz and the selection matrix J ₁ , J _{2 of} the ESPRIT method corresponding to the first and second subarrays are calculated. Based on the above, the arrival azimuth angle of the received signal received by the array antenna is calculated using the ESPRIT method. Therefore, a plurality of directions of arrival of radio waves can be detected simultaneously with higher detection accuracy than the conventional example.

It is a block diagram which shows the structure of the electromagnetic wave arrival direction detection apparatus which is embodiment which concerns on this invention. It is sectional drawing which shows the detailed structure of the array antenna apparatus 100 of FIG. It is a top view which shows arrival azimuth angle (theta) in the array antenna apparatus 100 used by this embodiment. (A) is a top view which shows the set S1a of the antenna element of the array antenna apparatus 100 used in the radio wave arrival direction detection method using the ESPRIT method according to the present embodiment, and (b) is the antenna element of the array antenna apparatus 100. It is a top view which shows set S1b. (A) is a top view which shows the set S2a of the antenna element of the array antenna apparatus 100 used in the radio wave arrival direction detection method using the ESPRIT method according to the present embodiment, and (b) is the antenna element of the array antenna apparatus 100. It is a top view which shows set S2b. (A) is a top view which shows the set S3a of the antenna element of the array antenna apparatus 100 used in the radio wave arrival direction detection method using the ESPRIT method according to the present embodiment, and (b) is the antenna element of the array antenna apparatus 100. It is a top view which shows set S3b. (A) is a top view which shows subarray SA1 in the 3 element linear array antenna apparatus which concerns on the 1st modification used in the electromagnetic wave arrival direction detection method using the ESPRIT method which concerns on this embodiment, (b) is said 3 It is a top view which shows subarray SA2 in an element linear array antenna apparatus. (A) is a top view which shows subarray SA1 in the 5-element linear array antenna apparatus which concerns on the 2nd modification used in the electromagnetic wave arrival direction detection method using the ESPRIT method which concerns on this embodiment, (b) is said 5 It is a top view which shows subarray SA2 in an element linear array antenna apparatus. (A) is a top view which shows subarray SA1 in the 6 element two-dimensional array antenna apparatus which concerns on the 3rd modification used in the electromagnetic wave arrival direction detection method using the ESPRIT method which concerns on this embodiment, (b) is the said It is a top view which shows subarray SA2 in a 6 element two-dimensional array antenna apparatus. (A) is a top view which shows subarray SA1 in the 6-element two-dimensional array antenna apparatus which concerns on the 4th modification used in the electromagnetic wave arrival direction detection method using the ESPRIT method which concerns on this embodiment, (b) is the said It is a top view which shows subarray SA2 in a 6 element two-dimensional array antenna apparatus. It is a top view which shows subarray SA1 and SA2 in the conventional linear array antenna apparatus used in the electromagnetic wave arrival direction detection method using the ESPRIT method which concerns on this embodiment. FIG. 7 is a plan view showing a reference azimuth angle θref in each set of FIGS. 4 to 6. 7 is a table showing subarray division and reference azimuth angle θref in each set of FIGS. 4 to 6. It is a simulation result of the radio wave arrival direction detection device using the ESPRIT method according to the present embodiment, and is a graph showing an azimuth angle error with respect to the arrival azimuth angle DoA in the set S1a. It is a simulation result of the radio wave arrival direction detection device using the ESPRIT method according to the present embodiment, and is a graph showing the azimuth angle error with respect to the arrival azimuth angle DoA in the set S1b. It is a simulation result of the radio wave arrival direction detection apparatus using the ESPRIT method according to the present embodiment, and shows a CDF (three-dimensional cumulative distribution function) curve of the azimuth angle error with respect to the arrival azimuth angle DoA when SNR = −5 dB. It is a graph. FIG. 6 is a graph showing a simulation result of the radio wave arrival direction detection device using the ESPRIT method according to the present embodiment and showing a CDF (three-dimensional cumulative distribution function) curve of the azimuth angle error with respect to the arrival azimuth angle DoA when SNR = 0 dB. It is. FIG. 6 is a graph showing simulation results of the radio wave arrival direction detection apparatus using the ESPRIT method according to the present embodiment, and showing a CDF (three-dimensional cumulative distribution function) curve of the azimuth angle error with respect to the arrival azimuth angle DoA when SNR = 10 dB. It is. It is a simulation result of the radio wave arrival direction detection apparatus using the ESPRIT method according to the present embodiment, and is a graph showing the azimuth angle error with respect to the number of samples when the arrival azimuth angle θ = 65 °. Directional characteristic diagram showing a radiation pattern P (i ₁ ^T ) corresponding to the current i ₁ ^T corresponding to the _first reactance value set used in the simulation of the radio wave arrival direction detection device using the ESPRIT method according to the present embodiment It is. Directional characteristic diagram showing a radiation pattern P (i ₂ ^T ) corresponding to the current i ₂ ^T corresponding to the second reactance value set used in the simulation of the radio wave arrival direction detection device using the ESPRIT method according to the present embodiment It is. Directional characteristic diagram showing a radiation pattern P (i ₃ ^T ) corresponding to the current i ₃ ^T corresponding to the third reactance value set used in the simulation of the radio wave arrival direction detection device using the ESPRIT method according to the present embodiment It is. Directional characteristic diagram showing a radiation pattern P (i ₄ ^T ) corresponding to the current i ₄ ^T corresponding to the fourth reactance value set used in the simulation of the radio wave arrival direction detector using the ESPRIT method according to the present embodiment It is. Directional characteristic diagram showing a radiation pattern P (i ₅ ^T ) corresponding to the current i ₅ ^T corresponding to the _fifth reactance value set used in the simulation of the radio wave arrival direction detector using the ESPRIT method according to the present embodiment It is. Directional characteristic diagram showing a radiation pattern P (i ₆ ^T ) corresponding to the current i ₆ ^T corresponding to the _sixth reactance value set used in the simulation of the radio wave arrival direction detector using the ESPRIT method according to the present embodiment It is. Directional characteristic diagram showing a radiation pattern P (i ₇ ^T ) corresponding to the current i ₇ ^T corresponding to the _seventh reactance value set used in the simulation of the radio wave arrival direction detector using the ESPRIT method according to the present embodiment It is.

Explanation of symbols

A0: Feeding element,
A1 to A6 ... non-feeding element,
1 ... Low noise amplifier (LNA),
2 ... Down converter,
3 ... A / D converter,
5 ... Coaxial cable for feeding,
10 ... wireless receiver,
11: Ground conductor,
12-1 to 12-6 ... variable reactance element,
20 ... Controller,
21 ... CRT display
100: Array antenna device.

Claims (4)

A feed element for receiving a radio signal; a plurality of non-feed elements provided at a predetermined distance from the feed element; and a variable reactance element connected to each of the non-feed elements. By changing the reactance value of the variable reactance element, each non-feeding element is operated as a director or a reflector, and a radio signal arriving at the array antenna is changed using an array antenna that changes the directivity characteristics of the array antenna. In the radio wave arrival direction detection device that measures the arrival azimuth angle,
The array antenna includes a first sub-array composed of a plurality of antenna elements including the feed element and at least one non-feed element, and at least the feed element positioned when the first sub-array is moved in parallel. Configuration capable of selecting a second subarray including a plurality of antenna elements including one non-feeding element and selecting all the antenna elements by the selection of the first and second subarrays. Have
The radio wave arrival direction detection device is
Detecting each received signal y (t) received according to the array antenna when a set of reactance values of the variable reactance elements different from each other is set, and calculating a correlation matrix Rh _zz based on each received signal; A received signal received by the array antenna using the ESPRIT method based on the calculated correlation matrix Rh _zz and the selection matrices J ₁ and J _{2 of} the ESPRIT method corresponding to the first and second subarrays. And a radio wave arrival direction detecting device, comprising: a control means for calculating an arrival azimuth angle of the radio wave. The control means, by eigenvalue decomposition of the correlation matrix Rh _zz which is the calculated to calculate the eigenvalues alpha _m of the correlation matrix Rh _zz, calculate the correlation matrix Rh _nn based on the noise based on the computed eigenvalues alpha _m Then, based on the two calculated correlation matrices Rh _zz and Rh _nn , a correlation matrix Rh _yy based on the transmitted radio signal is calculated, and eigenvalue decomposition is performed on the calculated correlation matrix Rh _yy by eigenvalue decomposition. _k is calculated and received by the array antenna using the ESPRIT method based on the calculated eigenvector w _k and the selection matrices J ₁ and J _{2 of} the ESPRIT method corresponding to the first and second subarrays. 2. The radio wave arrival direction detecting device according to claim 1, wherein an arrival azimuth angle of the received signal is calculated. A feed element for receiving a radio signal; a plurality of non-feed elements provided at a predetermined distance from the feed element; and a variable reactance element connected to each of the non-feed elements. By changing the reactance value of the variable reactance element, each non-feeding element is operated as a director or a reflector, and a radio signal arriving at the array antenna is changed using an array antenna that changes the directivity characteristics of the array antenna. In the radio wave arrival direction detection method that measures the arrival azimuth angle,
The array antenna includes a first sub-array composed of a plurality of antenna elements including the feed element and at least one non-feed element, and at least the feed element positioned when the first sub-array is moved in parallel. Configuration capable of selecting a second subarray including a plurality of antenna elements including one non-feeding element and selecting all the antenna elements by the selection of the first and second subarrays. Have
The radio wave arrival direction detection method is as follows.
Detecting each received signal y (t) received according to the array antenna when a set of reactance values of the variable reactance elements different from each other is set, and calculating a correlation matrix Rh _zz based on each received signal; A received signal received by the array antenna using the ESPRIT method based on the calculated correlation matrix Rh _zz and the selection matrices J ₁ and J _{2 of} the ESPRIT method corresponding to the first and second subarrays. A method for detecting a direction of arrival of radio waves, comprising a step of calculating an arrival azimuth angle of a radio wave. Calculating the arrival azimuth angle of the received signal, and eigenvalue decomposition of the correlation matrix Rh _zz which is the calculated to calculate the eigenvalues alpha _m of the correlation matrix Rh _zz, noise based on the computed eigenvalues alpha _m the correlation matrix _{Rh nn} based on calculated, based on the calculated two correlation matrices _{Rh zz} and _{Rh nn,} the correlation matrix _{Rh yy} based on radio signals transmitted are calculated, the calculated correlation matrix _{Rh yy} To calculate the eigenvector w _k, and based on the calculated eigenvector w _k and the selection matrices J ₁ and J _{2 of} the ESPRIT method corresponding to the first and second subarrays, the ESPRIT method 4. The radio wave arrival direction detection method according to claim 3, wherein an arrival azimuth angle of a received signal received by the array antenna is calculated using a signal.

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