JP5135595B2 - Direction measuring device - Google Patents

Description

  The present invention relates to an azimuth measuring apparatus that measures an azimuth of an incoming radio wave using an antenna element, for example, when monitoring illegal radio waves.

  By using a plurality of antenna elements to measure the time difference or phase difference of arrival of the same radio wave, the direction of arrival of the radio wave can be measured.

FIG. 5 shows the direction measurement principle when two antenna elements are used. The first antenna element 101 ₁ and the second antenna element 101 ₂ are fixed to be separated by a distance d (hereinafter referred to as an antenna distance d). It is assumed that the radio wave source is sufficiently far away. It is assumed that the radio wave 102 arrives from the direction θ. At this time, in the arrangement relationship shown in FIG. 5 , the first antenna element 101 ₁ is farther from the radio wave source by a distance l (el) than the second antenna element 101 ₂ . Therefore, the radio wave arrives at the first antenna element 101 ₁ after the elapse of a delay time corresponding to the distance (path difference) 1 from the second antenna element 101 ₂ . A relational expression between the path difference and the arrival direction can be expressed by the following expression (1).

sin θ = 1 / d
∴ θ = sin ⁻¹ l / d (1)

  The path difference l can be detected as the phase difference of the same radio wave. Therefore, it is possible to calculate the arrival direction of the received radio wave by measuring the phase difference of the radio wave at two points whose distances are known. Assuming that the measurement error of the path difference is constant, it is apparent from the equation (1) that the azimuth measurement error can be reduced as the antenna distance d increases.

  In the conventional azimuth measuring device, the antenna elements are arranged at equal intervals. If the measurement orientation can be specified to some extent, there is an example in which it is arranged in a straight line in a direction substantially perpendicular to this orientation, but in order to enable measurement of the entire circumference, generally a plurality of antenna elements on the steel tower Are arranged in a circular shape.

  FIG. 6 shows an example of a five-element antenna in which five antenna elements are arranged at equal intervals on the circumference. In the figure, each antenna element 101 is represented by a black dot. In this example, five antenna elements 101 are arranged at equal intervals on a circumference 111 having a predetermined diameter. Thereby, two of the five antenna elements 101 can increase the antenna interval d (FIG. 5) regardless of the direction from which the radio wave comes.

  By the way, in order to improve the accuracy of the measurement direction, it is necessary to secure a large opening area while securing the element spacing of each antenna element. For this purpose, it is necessary to change the arrangement of all antenna elements and to change the number of elements.

  FIG. 7 shows an example of a conventional antenna apparatus that improves the accuracy of the measurement direction as compared with the antenna apparatus of FIG. In order to increase the opening area, more antenna elements 101 are arranged on a circumference (not shown) having a larger diameter than the circumference 111 arranged at the same position as in FIG. In this example, a total of nine antenna elements 101 are arranged.

  In the case of the antenna apparatus shown in FIG. 7, the accuracy of the measurement direction can be further improved. However, when an improvement is made from the antenna apparatus of FIG. 6, it is necessary to change the arrangement of all the antenna elements 101. Further, the number and arrangement area of the antenna elements 101 are greatly increased. Therefore, for example, when a 5-element antenna as shown in FIG. 6 is arranged on a steel tower, the steel tower itself must be enlarged or reinforced.

  Further, when each antenna element is separately arranged at a high place such as a rooftop of a building, the arrangement space is often limited like the area of the rooftop. Therefore, in many cases, the arrangement shown in FIG. 6 cannot be expanded to the arrangement shown in FIG. Furthermore, since the number of antenna elements 101 is significantly increased, there is a problem that the scale of the orientation measuring device is greatly increased and the cost is greatly increased.

While arranging a plurality of antenna elements along the circumference, it has also been proposed to arrange one antenna element at a position different from these (see, for example, Patent Document 1). In this proposal, as shown in FIG. 5 or FIG. 6, antenna elements are arranged at equal intervals on the circumference, and one antenna line is positioned at a position that is clearly shifted up or down at the center position of the circumference. Elements are arranged.
JP-A-4-157383 (first page, lower right column, 5th to 8th lines, FIGS. 2 and 5)

  This proposal makes it possible to measure the incident angle in the height direction and measure the three-dimensional orientation in addition to the conventional two-dimensional orientation measurement. This is because the added one antenna element is arranged at the center position of the circumference, so that the effect of expanding the antenna interval d cannot be expected as is apparent from the discussion in FIG.

  Therefore, as described above, in the conventional azimuth measuring device, in order to increase the accuracy of the azimuth measurement, it is necessary to change the circumference on which the antenna element is arranged to a larger one, and thereby the scale of the azimuth measuring device. Will increase significantly, and the cost will increase.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an azimuth measuring apparatus that can improve the accuracy of measurement azimuth without greatly increasing the number of antenna elements.

In the present invention, (a) a desired point fixedly located at a predetermined height from the ground is included in a plane having the same height as the origin when the origin is determined, and a predetermined point centered on the origin is included. An antenna element group in which a plurality of first antenna elements are arranged at equal intervals on the circumference of the diameter ; and (b) a specific one of the first antenna elements constituting the antenna element group . when the position with a specific vertex, the position of the vertex of the remaining two positions mentioned above of the antenna element groups described above on the side to a position other than that of the first antenna element and the viewed from the specific vertex and the The distances from the position of the specific vertex to the position of the remaining two vertices described above are equal in the area outside the circle constituting the circumference, and these distances are the same as the remaining 2 described above. to be larger in length than the distance connecting the position of a vertex point A second antenna element arranged each of the remaining two positions the position of the vertices and the on position, (iii) any two points from the plurality of first antenna element disposed on a circumference which is The first antenna element is selected, and the direction of the target radio wave source is calculated using the relational expression between the path difference between the two first antenna elements at these two locations and the arrival direction of the radio wave with respect to this direction. The first antenna element use measuring means, and (d) one of the second antenna elements existing at the remaining two vertices and the first vertex existing at the specific vertex. The first and second antenna element measuring means for calculating the direction of the target radio wave source using the relational expression between these path differences and the arrival direction of the radio wave. And (e) when these first antenna elements are used alone It means a direction measuring device and a measuring time selecting means for selecting at the time of measurement the desired measurement means of the first and second antenna elements using the measurement means comprises.

As described above, according to the present invention, the antenna element of the azimuth measuring device is composed of the antenna element group and the second antenna element added to the antenna element group. Measurement accuracy can be easily improved, and existing facilities can be used effectively. In addition, in the case of measurement that does not require so much accuracy as in the primary measurement, it is possible to measure only the antenna element group by selecting the first measuring element when using the antenna element alone . Measurement efficiency can be improved by measuring the first and second antenna elements and using the second antenna element in the added form.

  Hereinafter, the present invention will be described in detail with reference to examples.

FIG. 1 shows a two-dimensional arrangement of antenna elements constituting the azimuth measuring apparatus of the present embodiment. In FIG. 1, the X axis and the Y axis are included in a plane having the same height as the origin “0”, which is a point at a certain height on the ground. About the origin "0", first to fifth antenna elements 201 _{1 to 201 5} is on the circumference of the first circle 202 of radius a, are arranged at regular intervals at an angle of every 72 degrees Yes. Here, the symbol a is an arbitrary length depending on the wavelength of the radio wave to be measured.

In this embodiment, the sixth and seventh antenna elements 201 _6, 201 ₇ away from the antenna element group consisting of antenna elements 201 _{1 to 201 5} of the first to fifth in distance manner also, the same direction measuring device 200 It arranges as what constitutes. Here, the sixth and seventh antenna elements 201 _6, 201 _7, most distantly distant respect first. 1 to X-axis component in the fifth antenna element 201 _{1 to 201 5} fifth antenna element 201 ₅ are arranged at the positions of the three vertices of the triangle that are substantially equilateral triangles. That is, the antenna element 201 _{5-201 7} of fifth to seventh, it can be said that almost located radially long circumference on the second circle 203 than the first circle 202.

Arrangement of the antenna elements 201 _{1 to 201 7} such first to seventh, realized in several ways. As the first approach, the antenna element 201 _{1 to 201 5} of the first to fifth is 5 element antenna placed on top of the existing tower, antenna elements 201 ₆ remaining sixth and seventh, 201 ₇ is composed of one-element antennas respectively arranged on two newly constructed steel towers. In this case, the new architecture the two towers sixth and seventh antenna elements 201 _6, 201 ₇ first to seventh embodiment by simply placed, one of these antenna elements 201 it is possible to realize the arrangement of _{1-201 7.}

Of course, the first to seventh antenna elements 201 have a structure in which a total of seven steel towers are built directly on a relatively high place such as the rooftop of a building, or a single element antenna is arranged on each of these places and flats. it is also possible to realize the arrangement of _{1-201 7.}

FIG. 2 shows the overall configuration of an azimuth measuring apparatus using these first to seventh antenna elements. A first reception signal 211 ₁ based on radio waves received by the _first antenna element 201 ₁ constituting the azimuth measuring apparatus 200 is input to the first receiver 212 ₁ . A reference signal 215 corresponding to a measurement frequency created by a local transmitter 214 controlled by a control processing unit 213 using a CPU (Central Processing Unit) (not shown) is input to the first receiver 212 ₁ .

The first receiver 212 ₁ converts the frequency of the first received signal 211 ₁ based on the reference signal 215 and converts the first signal 217 ₁ as an output thereof to the first A / D converter 218. Enter ₁ The first A / D conversion unit 218 ₁ supplies the first digital signal 219 ₁ obtained by the A / D conversion to the first orthogonal transformation unit 220 ₁ . The first orthogonal transform unit 220 ₁ converts the first digital signal 219 ₁ into first complex data 221 ₁ composed of a real part I and an imaginary part Q. The first complex data 221 ₁ is input to the azimuth processing unit 222.

Although the radio wave received in the first antenna element 201 ₁ is described the process until the input is converted first to the complex data 221 ₁ to the azimuth processing unit 222, the second antenna element 201 _2, second The same processing is performed for the antenna element 2007 of _seven . Therefore, description of these circuit portions is omitted.

The direction processing unit 222 is connected to the steering vector storage unit 223 and the control processing unit 213. The steering vector storage unit 223, first to the pattern data of the seventh antenna elements 201 _{1 to 201 7} corresponding to the arrival direction is stored as a result of preliminary measurement for each measurement frequency. The direction processing unit 222 extracts pattern data corresponding to the set frequency from the steering vector storage unit 223. Then, by correlating the first to seventh complex data 221 ₁ to 221 ₇ as a receiving data inputted from the first to the seventh orthogonal transformer 220 220 ₁ -220 _7, the orientation of the arriving radio waves It comes to calculate.

  There are algorithms such as the MUSIC (Multiple Signal Classification) method and ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques) method for calculating the bearing, and it is free to decide which algorithm the bearing processing unit 222 adopts. . Here, the principle of azimuth calculation will be briefly described on the assumption that the MUSIC method is adopted.

An input vector by the array antenna consisting of antenna elements 201 _{1 to 201 7} of the first to seventh and X (t). Let K be the number of elements of the array antenna. In this embodiment, the number of elements K is “7”, but the general expression representing the input vector X (t) is as shown in the following expression (2).

  X (t) = {X1 (t), X2 (t),..., XK (t)} (2)

  Using this equation (2), a K-dimensional autocorrelation matrix S is calculated by the following equation (3).

S = E [X (t) X ^H (t)] (3)
Here, the symbol H represents conjugate transpose.

  When the general eigenvalue problem of the autocorrelation matrix S is solved, the obtained eigenvalue is expressed by the following equation (4).

λ ₁ ≧ λ ₂ ≧… ≧ λ _L > λ _{L + 1} = λ _{L + 2} ... = λ _K (4)

In this equation (4), the code L is the number of incoming waves. From the relationship between the code L and the eigenvector {e _{L + 1} ... E _K } obtained here and the relationship of {e _{L + 1} ... E _K } which is a function of the arrival direction θ, the evaluation function P _mu ( θ) can be obtained from the following equation (5).

However, the symbol E _N is expressed by the following equation (6).

E _N = [e _{L + 1} ,..., E _K ] (6)
Further, a (θ) is an array response vector.

{ΘL,..., ΘK} in which the evaluation function P _mu (θ) indicates a peak is the calculated arrival direction of the radio wave.

Thus, in this embodiment, when the first to fifth antenna element 201 _{1 to 201 5} on the circumference of the first circle 202 and the existing antenna element group, the sixth and seventh antenna elements to 201 are disposed _6, 201 ₇ additionally. Accordingly, it is possible to perform azimuth measurement mainly using the _{fifth to seventh} antenna elements 201 _{5 to} 2007 on the circumference of the second circle 203 having a longer radius than the first circle 202.

  The control processing unit 213 illustrated in FIG. 2 outputs the measurement result 225 of the orientation obtained by the calculation to the output terminal 226. A printer or a display (not shown) is connected to the output terminal 226 according to the type of data output as the measurement result 225.

  <First Modification of Invention>

FIG. 3 shows the arrangement structure of the first to seventh antenna elements in the first modification of the present invention. On the circumference of the first circle 202, the first to fifth antenna elements 201 _{1 to 201 5} is arranged as in FIG. In this figure, it is assumed that the outer frame 301 is a space where a steel tower can be built on the roof of the building. First circle 202, and is disposed at a position offset to one of the outer frame 301 as shown, and installing additional two of the sixth and seventh antenna elements 201 _6, 201 _7. In this case, the sixth and seventh sixth and seventh as one of the antenna elements 201 _6, 201 ₇ two and the first to fifth antenna elements 201 _{1 to 201 5} constitute the equilateral triangle it is also possible to determine the position of the antenna element 201 _6, 201 _7. However, by effectively utilizing the space in the outer frame 301, is better to determine the position of the sixth and seventh antenna elements 201 _6, 201 _7, as shown in a shape close to an isosceles triangle indicated by one-dot chain line 302 The accuracy of azimuth measurement for all directions is improved.

Sixth and seventh antenna elements 201 _6, 201 ₇ this is located outside the first circle 202 of the antenna element group such forms, for example each vertex of the fifth antenna element 201 ₅ and equilateral triangle It does not have to be in position. However, these sixth and seventh antenna elements 201 _6, 201 _7, present in orientation respectively different when the center or first to fifth base point antenna elements 201 _{1 to 201 5} of the first circle 202 There is a need to. Assuming that the antenna element 201 _{5-201 7} of fifth to seventh had been all arranged on the same straight line, the measurement of the orientation in a direction approximating the direction perpendicular to the straight lines is performed accurately, the This is because the accuracy of measuring the orientation in a direction where the inclination is not much different from the straight line is not sufficiently improved.

  <Second Modification of Invention>

FIG. 4 shows the arrangement structure of the first to eighth antenna elements in the second modification of the present invention. In the second modification, Ideal When adding three antenna elements of the antenna element 201 _{6-201 8} of sixth to eighth against antenna element 201 _{1 to 201 5} of the first to fifth The arrangement is shown. Each position of the antenna element 201 _{5-201 8} of the eighth coincides with the vertices of a square indicated by dashed line 311. This means that the _{fifth to eighth} antenna elements 201 _{5 to} 2018 are positioned on the circumference of the second circle 312 having a radius larger than that of the first circle 202, respectively. Of the opening area.

In the embodiment and each modified example, the description has been made on the assumption that all the antenna elements are located in the same plane. However, the added _{sixth to eighth} antenna elements 201 _{6 to} 2018 are added. You may arrange | position in the up-down position different from the surface where the 1st circle | round | yen 202 exists. This makes it possible to measure not only the direction but also the elevation angle and depression angle.

Although in the embodiment and the modifications described as the first to fifth antenna elements 201 _{1 to 201 5} is arranged on the circumference of the first circle 202, these antenna elements are measured in all directions Of course, the number is not particularly limited as long as it is three or more. Of course, the number of antenna elements arranged outside the first circle 202 is not particularly limited.

It is arrangement | positioning explanatory drawing which showed the two-dimensional arrangement | positioning of the antenna element which comprises the azimuth | direction measuring apparatus in one Example of this invention. It is a block diagram showing the whole structure of the azimuth | direction measuring apparatus of a present Example. It is arrangement | positioning explanatory drawing which showed the arrangement structure of the 1st-7th antenna element in the 1st modification of this invention. It is arrangement | positioning explanatory drawing which showed the arrangement structure of the 1st-8th antenna element in the 2nd modification of this invention. It is explanatory drawing which showed the direction measurement principle at the time of using two antenna elements. It is arrangement | positioning explanatory drawing which showed the example of the 5-element antenna which arranged five antenna elements on the circumference at equal intervals. It is arrangement | positioning explanatory drawing showing an example of the conventional antenna apparatus which improves the precision of a measurement direction rather than the antenna apparatus of FIG.

Explanation of symbols

200
201 _{1-201 5} first to fifth antenna elements (antenna element group)
201 _{5 to} 2018 _{5th to 8th} antenna elements 202 1st circles 203 and 312 2nd circle 213 Control processing unit 222 Direction processing unit

Claims (3)

When a desired point that is fixedly located at a predetermined height from the ground is defined as the origin, it is included in a plane with the same height as the origin, and on a circle with a predetermined diameter centered on the origin An antenna element group in which a plurality of first antenna elements are arranged at equal intervals;
When a particular vertex positions of a specific one point of said first antenna elements constituting the antenna element group, wherein the position of the vertex of the remaining two positions as viewed from the particular vertex first The antenna element is disposed in a region outside the circle constituting the circumference of the antenna element group on the other side of the antenna element, and from the position of the specific vertex to the positions of the remaining two vertices A second antenna element in which the distances of the remaining two vertices are respectively arranged at positions where the distances are equal and these distances are longer than a distance connecting the positions of the remaining two vertices ; ,
Any two first antenna elements are selected from the plurality of first antenna elements arranged on the circumference, and the direction of the target radio wave source is set to the two directions with respect to this direction. A first antenna element single-use measuring means for calculating using a relational expression between the path difference of the first antenna element and the arrival direction of radio waves;
Select one of the second antenna elements existing at the remaining two vertices and the first antenna element present at the specific vertex, and the direction of the target radio wave source , Using the first and second antenna elements when using the relationship between these path differences and the direction of arrival of radio waves,
A measurement time selection means for selecting a desired measurement means among the first and second antenna element use measurement means at the time of measurement. A characteristic orientation measuring device.   The azimuth measuring apparatus according to claim 1, wherein the plurality of first antenna elements and the second antenna elements are both arranged on the same plane. Wherein said second antenna element each present at the apex of the remaining two positions with respect to a plane formed by the plurality of first antenna elements, characterized in that it is arranged at a distance in the vertical direction Item 3. An orientation measuring apparatus according to item 1.

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