JP2018121118A - Radar antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radar antenna with low height and a simple layout.SOLUTION: A radar antenna is set an electromagnetic wave of which a wavelength in a free space is λas reception and transmission targets. The radar antenna comprises: an array antenna part; two waveguide plates; and a waveguide device. The array antenna part includes a plurality of antenna elements arranged in a liner state. The two waveguide plates sandwich the arrangement of the antenna elements, and waveguide the electromagnetic wave. The waveguide device is structured by a plurality of parasitic antennas arranged in a progressing direction of an electromagnetic wave in each antenna element. An interval hin an arrangement part of the antenna elements of each waveguide plate satisfies an inequality below, where λ/2<h<λ. When a wavelength of the electromagnetic wave in a space sandwiched by the parallel each waveguide plate of which the interval is his λ, an interval d of both antenna elements satisfies an inequality below, where 0.8λ<d<0.8λ. The length of the arrangement of the waveguide device is longer than that of the progressing direction of the electromagnetic wave of the waveguide plate.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a radar antenna used for radar reception or transmission, and more particularly to a radar antenna for ship radar.

  Non-patent document 1 discloses a technique related to ship radar. In ship radar, horizontally polarized waves are used to reduce the influence of sea surface reflection. As a radar antenna mounted on a ship, an array antenna in which a plurality of antenna elements are arranged horizontally is used. It always rotates horizontally. A technique related to the array antenna is disclosed in Non-Patent Document 2 and the like. Non-Patent Document 3 shows that the wavelength of the radio wave is longer than that in free space in a space sandwiched by waveguide plates that are narrower than the wavelength in free space.

The Institute of Electronics, Information and Communication Engineers, “Knowledge Base, Knowledge Forest, Group 11 (Social Information Systems)-Part 2 (Electronic Navigation and Navigation System) Chapter 2 Marine Systems 2-2 Ship Monitoring Systems 2-2-1 Ship Radar”, [ Search on December 19, 2016], Internet <http://www.ieice-hbkb.org/files/11/11gun_02hen_02.pdf>. The Institute of Electronics, Information and Communication Engineers, “Knowledge-based Knowledge Forest, Group 4 (Communication Engineering)-Part 2 (Antenna / Propagation) Chapter 7 Array Antenna”, [Searched on December 19, 2016], Internet <http: // www .ieice-hbkb.org / files / 04 / 04gun_02hen_07.pdf>. Lars Josefsson, “A Waveguide Transverse Slot for Array Applications”, IEEE Transactions on Antennas and Propagation, Vol.41, No.7, July 1993.

  The driving means for rotating the marine radar antenna in the horizontal direction (rotating around the vertical axis) needs to be designed in consideration of the drag that the radar antenna receives due to the wind pressure. Therefore, in order to reduce the size of the driving means, it is necessary to reduce the size of the radar antenna, and in particular, it is necessary to reduce the height (shorten the length in the vertical direction). However, since the antenna gain depends on the area of the opening, there is generally a trade-off relationship between the design related to the drag due to wind pressure and the gain design. As a method of increasing the gain other than the method of increasing the area of the opening, there is a method of using a waveguide in which a plurality of parasitic antennas are arranged like the Yagi-Uda antenna. However, the distance between the antenna elements of the array antenna needs to be less than 0.8 of the wavelength of the radio wave in order to suppress the grating lobe. Accordingly, when all the antenna elements are each provided with a director, the interval between adjacent waveguides becomes narrow, so that it is necessary to design in consideration of the interference between the waveguides, which is complicated.

  The present invention has been made in view of such a situation, and an object thereof is to provide a radar antenna having a low height and easy design.

The radar antenna of the present invention receives or transmits radio waves having a wavelength of λ _{0 in} free space. The radar antenna of the present invention includes an array antenna unit, two waveguide plates, and a director. The array antenna unit has a plurality of antenna elements arranged in a straight line. The two waveguide plates guide the radio wave across the array of antenna elements. The director is composed of a plurality of parasitic antennas arranged in the traveling direction of radio waves for each antenna element. The distance _{h r1} of an array portion of the antenna element of the wave guide is a _{λ 0/2 <h r1 <} λ 0. When the wavelength of the radio wave in the space sandwiched between the parallel waveguide plates with the interval h _r1 is λ _r , the interval d between the antenna elements is 0.8λ ₀ <d <0.8λ _r . The length of the arrangement of the directors is longer than the length of the wave propagation direction of the waveguide plate.

  According to the array antenna of the present invention, since the wavelength is longer than the free space in the space between the two waveguide plates that are narrower than the wavelength in the free space, the grating is provided even if the distance between the antenna elements is widened. The lobe can be suppressed. Since the length of the arrangement of the directors is longer than that of the waveguide plate, radio waves can be guided between the free space and the antenna element. Further, since the distance between the antenna elements is wide, the waveguides can be separated from each other, and the necessity of considering the interference between the waveguides at the time of designing is low. Therefore, it is possible to provide a radar antenna that is low in height and easy to design.

The figure which shows the block diagram of the radar apparatus containing the radar antenna of this invention. The figure which shows the structural example of the radar antenna of this invention. The figure which shows one example of an antenna element. The figure which shows the structure of the antenna which has one antenna element and two waveguide plates. The figure which shows the relationship between the space | interval of a waveguide plate when it is pinched | interposed into a parallel waveguide plate, and a wavelength. The figure which shows the result of having simulated the electric field of free space (state without the waveguide board of FIG. 4). It shows the results of distance h _r is the simulation of the electric field of the space between the parallel waveguide plate of lambda ₀ (state in Fig. 4). It shows the results of distance h _r is the simulation of the electric field of the sandwiched parallel waveguide plate space (the state of FIG. 4) of 0.9λ _0. It shows the results of distance h _r is the simulation of the electric field of the sandwiched parallel waveguide plate space (the state of FIG. 4) of 0.6λ _0. 16 antenna elements ₁₂₀ 1 to the waveguide 132, ..., shows how _{the 120 16} are formed at intervals d. FIG. 11 is a diagram showing an electric field distribution when the antenna elements 120 ₁ ,..., 120 _{16 in} FIG. The figure which shows a mode that one of the antenna elements arranged by the space | interval d was cut out. The figure which shows the result of having simulated the electric field of the antenna element shown to FIG. The figure which shows the result of having simulated the electric field of the antenna element shown to FIG. The figure which shows the result of having simulated the electric field of the antenna element shown to FIG. The figure which shows the result of having simulated the electric field of the antenna element shown to FIG. The figure which shows the simulation result of the electric field of the radar antenna which arranged 10 antenna elements shown to FIG. 12 (A)-(D). The figure which shows the simulation result of the magnetic field of the radar antenna which arranged ten antenna elements shown to FIG. 12 (A)-(D). The figure which shows the result of having simulated the cross polarization of the radar antenna which arranged ten antenna elements shown in FIG.12 (D).

  Hereinafter, embodiments of the present invention will be described in detail. In addition, the same number is attached | subjected to the structure part which has the same function, and duplication description is abbreviate | omitted.

FIG. 1 shows a configuration diagram of a radar apparatus including a radar antenna of the present invention. FIG. 2 is a diagram illustrating a configuration example of a radar antenna according to the present invention, and FIG. 3 is a diagram illustrating one example of an antenna element. In the following, N and M are integers of 2 or more, n is an integer of 1 to N, and m is an integer of 1 to M. The radar apparatus 10 includes a radar antenna 100 and driving means 210. The radar antenna 100 includes an array antenna unit 110, two waveguide plates 141 and 142, and waveguides 150 ₁ ,..., 150 _N , and receives or transmits a radio wave having a wavelength of λ _{0 in} free space. To do. The adjustment unit 140 shown in FIG. 1 has two waveguide plates 141 and 142. Note that the waveguide plates 141 and 142 are actually opaque metal plates, but in FIG. 2, the inside is visible to show the structure of the radar antenna 100 and is shown by dotted lines. The same applies to FIGS.

The array antenna unit 110 includes a plurality of antenna elements 120 ₁ ,..., 120 _N and an input / output unit 130 arranged in a straight line. The input / output unit 130 may be configured by, for example, a waveguide 132 and an interface unit 131. In this case, the antenna element 120 _n may be a slit provided in the waveguide 132. The radio wave is output to the outside or input from the outside via the interface unit 131. Further, in the free space, when the wavelength of the radio wave having the wavelength λ ₀ in the waveguide is λ _g , the wavelength λ _g (or an integer multiple of the wavelength λ _g ) matches the interval d of the slit (antenna element 120 _n ). If the waveguide 132 is designed in this way, it can be a radar antenna that receives or transmits radio waves of the same phase. As will be described later, the wavelength in the space between the waveguide plates is longer than in free space. When the wavelength of the radio wave in the space sandwiched between the parallel waveguide plates with the interval h _r1 is λ _r , the interval d between the antenna elements may be 0.8λ ₀ <d <0.8λ _r . Conventionally, in order to suppress the grating lobe, it was necessary to set d <0.8λ _0. However, if 0.8λ ₀ <d <0.8λ _r , the antenna elements are more connected than the conventional array antenna. The grating lobe can be suppressed while increasing the interval.

In the case of marine radar, the arrangement of the antenna elements 120 ₁ ,..., 120 _N is set in the horizontal direction, and the slit (antenna element 120 _n ) provided in the waveguide 132 has a shape elongated in the vertical direction. Can receive or transmit radio waves. Then, the driving unit 210 rotates the radar antenna 100 about the vertical axis (rotates in the horizontal direction). The antenna element 120 _n may be formed by one slit, or may be configured by two slits 121 _n and 122 _n as shown in FIG. If two slits 121 _n and 122 _n are used, it is easy to design so as to suppress reflection of radio waves in the waveguide 132.

Two waveguide plates 141 and 142, antenna elements ₁₂₀ 1, ..., sandwiched array of 120 _N, guided through the radio. Antenna elements ₁₂₀ 1 Shirubehaban 141, ..., interval _{h r1} in sequence portion 120 _N is _{λ 0/2 <h r1 <} λ 0. Within this range, the wavelength λ _r in the space between the waveguide plates can be made longer than the wavelength λ ₀ in free space. In particular, if h _r1 ≦ 0.7λ ₀ , the wavelength λ _r can be made sufficiently longer than the wavelength λ ₀ . The waveguide plates 141 and 142 may be parallel to each other, and the interval h _r2 at a portion far from the arrangement of the antenna elements 120 ₁ ,..., 120 _N of the waveguide plates 141 and 142 is made wider than the interval h _r1. Also good. The change at the boundary between the space sandwiched between the waveguide plates 141 and 142 and the free space can be reduced by making the interval h _r2 wider than the interval h _r1 . In particular, if the distance h _r2 in the portion far from the arrangement of the antenna elements 120 ₁ ,..., 120 _N of the waveguide plates 141 and 142 is the wavelength λ ₀ (wavelength in free space), the change can be made smooth. The length _{L r} of the traveling direction of a radio wave Shirubehaban 141 and 142 may be longer than 0.75? _R. Furthermore, the vertical plane pattern can be controlled by adjusting the angles of the waveguide plates 141 and 142.

The director 150 _n includes M parasitic antennas 151 _n−1 ,..., 151 _n-M arranged in the traveling direction of the radio wave for each antenna element 120 _n . The length of the arrangement of the waveguides 150 _n is longer than the length L _r of the wave propagation direction of the wave guide plates 141 and 142.

  According to the array antenna of the present invention, since the wavelength is longer than the free space in the space between the two waveguide plates that are narrower than the wavelength in the free space, the grating is provided even if the distance between the antenna elements is widened. The lobe can be suppressed. Since the length of the arrangement of the directors is longer than that of the waveguide plate, the radio wave can be guided between the free space and the antenna element, so that the gain can be increased compared to the opening area. Further, since the distance between the antenna elements is wide, the waveguides can be separated from each other, and the necessity of considering the interference between the waveguides at the time of designing is low. Therefore, it is possible to provide a radar antenna that is low in height and easy to design.

<Verification by simulation>
FIG. 4 shows a configuration of an antenna having one antenna element and two waveguide plates. Antenna 4 includes one of the antenna elements 120 _1, there are two parallel waveguide plate 141 and 142 sandwiching the antenna element 120 _1. FIG. 5 shows the relationship between the distance between the waveguide plates and the wavelength when sandwiched between the parallel waveguide plates. The horizontal axis is the ratio of the wavelength lambda ₀ in the interval h _r and the free space when the parallel Shirubehaban 141,142. The vertical axis represents the ratio between the wavelength λ _r in the space between the waveguide plates 141 and 142 and the wavelength λ _{0 in} free space. Wavelength λ _r becomes longer as the interval _{h r} becomes narrow, cut-off (λ _r is infinite) becomes at the time of the interval _{h r} = _{λ 0/2.} Spacing is the wavelength lambda _r it is can be seen that significantly longer narrower than lambda _0. Therefore, the antenna elements ₁₂₀ 1 Shirubehaban 141, 142 ..., if the distance _{h r1} in sequence portion 120 _N to _{λ 0/2 <h r1 <} λ 0, at space between the wave guide the wavelength λ _r can be made longer than the wavelength λ ₀ in free space. In _addition, at the time of the h r1 = 0.7λ _0, is λ _r ≒ 1.5λ _0. Accordingly, particularly when h _r1 ≦ 0.7λ ₀ , the wavelength λ _r can be made sufficiently longer than the wavelength λ ₀ , so that the distance d between the antenna elements can be sufficiently separated.

FIG. 6 shows the result of simulating the electric field in free space (without the waveguide plate of FIG. 4), and FIGS. 7 to 9 show the result of simulating the electric field in the space (state of FIG. 4) sandwiched between the parallel waveguide plates. FIG. FIG. 7 shows the case where the interval h _r is the free space wavelength λ ₀ , FIG. 8 shows the case where the interval h _r is 0.9λ ₀ , and FIG. 9 shows the case where the interval h _r is 0.6λ ₀ . The directions of x, y, and z are the same as those in FIG. That is, (A) in FIGS. 6 to 9 is a diagram as viewed from above the antenna in FIG. 4, and (B) is a diagram as viewed from the right side surface. In these simulations, the length in the traveling direction of a radio wave Shirubehaban 141 and 142 is the _{length L r} is represented by (A) in FIGS. 7-9. Compared to the wavelength lambda ₀ in FIG. 6, the wavelength lambda _r in FIG. 7 1.155Ramuda _0, the wavelength lambda _r of FIG. 8 1.2λ _0, the wavelength lambda _r of FIG. 9 has a 1.81λ _0.

FIG. 10 is a diagram showing a state where ₁₆ antenna elements 120 ₁ ,..., 120 ₁₆ are formed in the waveguide 132 with a distance d, and FIG. The case where there is a waveguide plate is shown. The waveguide plates are parallel, the interval h _r is 0.65λ ₀ , the length L _r in the traveling direction of the radio wave of the waveguide plate is 1.5λ ₀ , and the interval d is 1.2λ ₀ . 11, the antenna elements ₁₂₀ 1 of FIG. 10, ..., _{120 16} shows the distribution of the electric field in the case of the same phase, if the wave guide is not, (B) may waveguide plate (A) Shows the case. In FIG. 11A, it can be seen that the electric field is not distributed parallel to the array of antenna elements, and in FIG. 11B, the electric field is distributed parallel to the array of antenna elements.

FIG. 12 is a diagram showing a state in which one of the antenna elements arranged at the interval d is cut out. (A) shows only antenna elements, (B) shows antenna elements and two waveguide plates, (C) shows antenna elements and a director, and (D) shows antenna elements and two sheets. This is a case having a waveguide plate and a director. The interval h _r1 of the waveguide elements 141 and 142 at the portion of the antenna element 120 _n is 0.7λ ₀ , and the interval h _{r2 of the} portions of the waveguide plates 141 and 142 far from the antenna element 120 _n is λ ₀ . The length L _r of the wave propagation direction of the waveguide plates 141 and 142 is 1.5λ ₀ , and the distance d is 1.2λ ₀ . The director 150 _n is composed of parasitic antennas 151 _n−1 ,..., 151 _n-M arranged so that the distance d _s is 0.35λ _{0 in} the traveling direction of the radio wave. However, the distance between the antenna element 120 _n and the parasitic antenna _{151 n-1} is 0.25 [lambda _0.

13-16 is a figure which shows the result of having simulated the electric field of the antenna element shown to FIG. 12 (A)-(D). 13 shows the results of FIG. 12 (A), FIG. 14 shows the results of FIG. 12 (B), FIG. 15 shows the results of FIG. 12 (C), and FIG. In the simulations of FIGS. 12C and 12D, the parasitic antennas 151 _nm are two antennas arranged on the plane perpendicular to the traveling direction of the radio wave so that the interval w _s is 0.26λ _0. It is configured. The length L _s of the parasitic antenna 151 _nm is 0.39λ _{0 to} 0.26λ ₀ , and is arranged so as to become longer as it is closer to the antenna element 120 _n . In the simulation, M = 21. The directions of x, y, and z are the same as those in FIG. That is, (A) in FIGS. 13 to 16 is a diagram viewed from the bottom of the antenna in FIG. 12, and (B) is a diagram viewed from the right side surface. The difference in Fig. 13, 15 and Figure 14 and 16, we are easy to make and can be seen an electric field parallel distribution arrangement of the antenna elements 120 _n in comprising Shirubehaban 141,142. Further, from FIG. 16, an electric field parallel distribution arrangement of the antenna element 120 _n by director 0.99 _n, it can be seen that can form to a more positions of the free space apart from the antenna element 120 _n. That is, since the radio wave can be guided, the gain can be increased.

FIGS. 17 and 18 are diagrams showing simulation results of a radar antenna in which ten antenna elements shown in FIGS. 12A to 12D are arranged. FIG. 17 is a diagram showing an electric field (main polarization) in the xy plane, and FIG. 18 is a diagram showing a magnetic field in the xz plane. FIG. 19 is a diagram illustrating a result of simulating cross polarization of a radar antenna in which ten antenna elements illustrated in FIG. 12D are arranged. In FIGS. 17 and 18, the result of FIG. 12A is shown by a one-dot chain line, the result of (B) is a dotted line with a long interval, the result of (C) is a dotted line with a narrow interval, and the result of (D) is a solid line. From the results of (B) and (D), it can be seen that the grating lobe generated in the portion where the angle is 60 to 90 degrees is suppressed. It can also be seen from the result (D) that the side lobe is lower than the other results. In FIG. 19, the magnetic field is indicated by a dotted line and the electric field is indicated by a solid line. From the results of FIG. 19, it can be seen that almost no cross-polarized radio waves are generated. That is, by arranging the antenna elements 120 ₁ ,..., 120 _{N in} the horizontal direction for use as a ship radar, the slit (antenna element 120 _n ) provided in the waveguide 132 is elongated in the vertical direction. It can be seen that unnecessary vertical polarization is unlikely to occur when a radio wave with horizontal polarization is received or transmitted.

  From these simulation results, as described above, “According to the array antenna of the present invention, the wavelength between the two waveguide plates narrower than the wavelength in free space is longer than that in free space. Grating lobes can be suppressed even when the spacing between antenna elements is wide.Because the length of the array of directors is longer than the waveguide plate, radio waves can be guided between the free space and the antenna elements, It can be seen that the gain can be increased compared to the opening area, and the distance between the antenna elements is wide, so that the waveguides can be separated from each other, and the need to consider interference between the waveguides during design is low.

DESCRIPTION OF SYMBOLS 10 Radar apparatus 100 Radar antenna 110 Array antenna part 120 Antenna element 121,122 Slit 130 Input / output part 131 Interface part 132 Waveguide 140 Adjustment part 141,142 Waveguide plate 150 Waveguide 151 Parasitic antenna 210 Driving means

Claims (6)

A radar antenna for receiving or transmitting a radio wave having a wavelength of λ _{0 in} free space,
An array antenna unit having a plurality of antenna elements arranged in a straight line;
Two waveguide plates for guiding the radio waves, sandwiching the array of antenna elements;
A director composed of a plurality of parasitic antennas arranged in the traveling direction of the radio wave for each antenna element;
With
Distance _{h r1} of an array portion of the antenna element of the waveguide plate is a _{λ 0/2 <h r1 <} λ 0,
When the wavelength of the radio wave in a space sandwiched between parallel waveguide plates with an interval of h _r1 is λ _r , the interval d between the antenna elements is 0.8λ ₀ <d <0.8λ _r ,
The radar antenna according to claim 1, wherein the length of the array of the directors is longer than the length of the wave guide plate in the traveling direction of the radio wave. The radar antenna according to claim 1, wherein
Radar antenna length in the traveling direction of the radio wave of the wave guide plate, characterized in that greater than 0.75? _R. The radar antenna according to claim 1 or 2,
radar antenna, which is a h _r1 ≦ 0.7λ _0. The radar antenna according to any one of claims 1 to 3,
A radar antenna, wherein an interval h _r2 at a portion of the waveguide plate far from the arrangement of the antenna elements is wider than the interval h _r1 . The radar antenna according to any one of claims 1 to 3,
A radar antenna, wherein an interval h _r2 at a portion far from the array of the antenna elements of the waveguide plate is the same as a wavelength λ ₀ . The radar antenna according to any one of claims 1 to 5,
The antenna element is a slit that is long in a direction perpendicular to the arrangement direction of the antenna elements provided in the waveguide, and the interval d between the antenna elements is an integral multiple of the wavelength of the radio wave in the waveguide. A radar antenna characterized by