JP7120106B2 - antenna device - Google Patents

Description

The present invention relates to an antenna device having a radome.

2. Description of the Related Art Conventionally, there is an antenna device using a spiral antenna to radiate radio waves with a small difference in amplitude value between a parallel component and a vertical component over a wide band and wide angle (see, for example, Patent Document 1). If the antenna device is to be resistant to pressure from multiple directions such as water pressure, the antenna element may be protected by providing a thick radome (see, for example, Patent Documents 2 and 3). ).

A radio wave radiated from an antenna element may be reflected by the radome, degrading the antenna characteristics depending on the thickness of the radome, and it is necessary to suppress this. In Patent Literature 2, the space between the radome and the antenna element is appropriately adjusted (1/2 wavelength, 1/4 wavelength, etc. of the frequency used) to suppress reflected waves from the radome. Further, in Patent Document 3, antenna characteristics are improved by inserting a dielectric at a position and thickness appropriate to the wave source in a part of the space between the radome and the antenna element to cancel the reflected wave from the radome. Prevents deterioration.

JP 2011-205537 A JP-A-2001-127523 Japanese Patent Application Laid-Open No. 2004-200895

However, the radome described in Patent Document 2 has a problem that it is difficult to radiate radio waves over a wide band because the radome has high frequency dependence and narrow band characteristics. The radome described in Patent Document 3 has a problem that it is difficult to radiate radio waves from an antenna whose wave source is located in a wide range because the position of the wave source is restricted.

The present invention has been made to solve the above-mentioned problems. An object of the present invention is to obtain an antenna device that reduces deterioration of antenna characteristics.

An antenna device according to the present invention comprises a substrate, a conductor pattern of a spiral antenna formed on the substrate, a feeding section connected to the conductor pattern, and a hemispherical radome provided in the radio wave radiation direction of the conductor pattern. and a conductor pattern formed in a first region inside the outer periphery of the substrate including the power feeding portion of the substrate radiates radio waves of a first frequency, and a second region outside the first region of the substrate The conductor pattern formed in the region of radiates radio waves of a second frequency lower than the first frequency, and faces the first region of the substrate of the facing surface, which is the surface facing the substrate of the radome. At least part of the surface facing the second region is characterized by being farther from the substrate than the surface of the facing surface facing the second region.

According to the present invention, it is possible to obtain an antenna device in which degradation of antenna characteristics is reduced even when an antenna that radiates radio waves over a wide band and at a wide angle is desired to have resistance to pressure from multiple directions. can.

1 is a cross-sectional view of an antenna device according to Embodiment 1 of the present invention; FIG. 1 is a top view of a substrate according to Embodiment 1 of the present invention; FIG. FIG. 4 is a diagram showing how the conductor pattern radiates according to the first embodiment of the present invention; FIG. 4 is a diagram showing incident angles of radio waves with respect to two types of radome shapes; 4 is a graph showing an example of power transmittance with respect to incident angle θi of radio waves to the flat plate radome. 1 is a cross-sectional view of a radome according to Embodiment 1 of the present invention; FIG. FIG. 4 is a top view of the substrate showing the positions of the recesses according to the first embodiment of the present invention; FIG. 2 is an enlarged view of a power feeding section according to Embodiment 1 of the present invention; FIG. 4 shows a top view of a substrate of another configuration of the antenna device according to Embodiment 1 of the present invention; FIG. 4 is a cross-sectional view of an antenna device having another configuration of the antenna device according to Embodiment 1 of the present invention; It is a cross-sectional view of an antenna device according to Embodiment 2 of the present invention. FIG. 5 is a top view of a substrate according to Embodiment 2 of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals are given to the same or equivalent parts.

Embodiment 1.
FIG. 1 is a cross-sectional view of an antenna device 100 according to Embodiment 1. FIG. This cross section is a plane perpendicular to the substrate 1 and passing through the power supply section 7 . The antenna device 100 includes an antenna section 2 and a radome 3 .

The antenna section 2 is composed of a substrate 1 (spiral substrate 1 ), a power supply substrate 5 , a power supply connector 6 , a power supply section 7 and an antenna case 8 . The antenna case 8 holds the substrate 1 , the power supply substrate 5 , the power supply connector 6 and the power supply portion 7 . The antenna case 8 is a cylindrical case with one side open. A substrate 1 is provided on the opening surface of the antenna case 8 so as to close the opening. A power feeding portion 7 is formed on the substrate 1 . One end of the feeding portion 7 has a protruding portion protruding from the substrate 1 on the side opposite to the surface on which the antenna case 8 is provided. One end of the power supply board 5 is connected to the other end of the power supply part 7 opposite to the projecting part. The other end of the feeding board 5 is connected to a feeding connector 6 provided outside the antenna case 8 . As a result, the power feeding board 5 is provided inside the antenna case 8 .

FIG. 2 is a top view of the substrate 1. FIG. The substrate 1 is a substrate such as a circular printed circuit board. Here, the shape of the substrate 1 is circular, but the shape is arbitrary. As shown in FIG. 2, the conductive pattern of the spiral antenna is formed by etching or the like on the surface of the substrate 1 opposite to the surface on which the antenna case 8 is provided. It can be said that the conductor pattern of the spiral antenna is formed on the surface of the substrate 1 opposite to the surface to which the feeding substrate 5 is connected. The conductor pattern of the spiral antenna is helical arms 1a and 1b having a self-complementary structure. The arms 1a and 1b are fed in parallel from the feeder 7 with a phase difference of 180 degrees. In this manner, the spiral antenna has a conductor pattern (arm 1a and arm 1b) that forms a two-dimensional curved spiral. Arm 1a and arm 1b have a point-symmetrical structure centered on a spiral of two-dimensional curve. Although the shape of the conductor pattern is circular here, it may be other shapes such as an elliptical shape or a shape in which the widths of the arms 1a and 1b are not constant.

The power feeder 7 is connected to the conductor pattern. The power supply portion 7 is formed on the substrate 1 in the central portion of the conductor pattern (the portion surrounded by the dotted line in FIG. 2). The power supply portion 7 is a portion where the conductor patterns (arm 1a and arm 1b) and the power supply substrate 5 are electrically connected. As a result, a high-frequency signal is input from the power supply connector 6 and excites the conductor pattern formed on the board 1 through the power supply board 5 and the power supply section 7 . Radio waves are radiated from the excited conductor pattern.

Assuming that the radius of the arms 1a and 1b, which are the conductor patterns of the spiral antenna (the distance from the feeder to the arm 1a or the arm 1b), is r, on the arms 1a and 1b with the radius r, the circumference 2πr and the wavelength λ are When they are equal, radio waves having a frequency corresponding to the wavelength λ are radiated from the arms 1a and 1b having the radius r. As a result, in the operating frequency band, the spiral antenna can radiate from the vicinity of the central portion in a high frequency band with a short wavelength, and radiate from the vicinity of the peripheral portion in a low frequency band with a long wavelength. That is, in the spiral antenna, broadband characteristics can be obtained by extending the arm length and increasing the diameter. Furthermore, since the spiral antenna (arms 1a and 1b) has a point-symmetrical structure as described above, it is possible to radiate radio waves with a small difference between the amplitude values of the parallel component and the vertical component over a wide angle.

FIG. 3 is a top view of the substrate 1, showing how the conductor pattern according to the first embodiment radiates. As shown in FIG. 3, in the first embodiment, on the substrate 1, a region including the power supply portion 7 and inside the outer periphery of the substrate 1 is defined as a first region 11 (the upper right hatched portion in FIG. 3), A region outside the first region 11 is set as a second region 12 (dotted portion in FIG. 3). At this time, the first region 11 has a circular shape centered on the power supply portion 7 . The second area 12 is an area outside the first area 11 and inside a circle centered on the feeding portion 7 having a radius larger than that of the first area 11 . Here, the circle (the outer periphery of the second region) centered on the feeding portion having a radius larger than that of the first region 11 is defined as the outer periphery of the substrate 1, but may be set inside the outer periphery of the substrate 1. . When the regions on the substrate 1 are set in this way, part of the conductor pattern (arm 1a and arm 1b) formed in the second region 12 is part of the first region due to the configuration of the spiral antenna described above. A radio wave having a frequency lower than that of the conductor patterns (arm 1a and arm 1b) formed in 11 is radiated. Although the first region 11 and the second region 12 are circular here, they may have other shapes such as an elliptical shape.

As shown in FIG. 1, the antenna section 2 is provided with a radome 3 in the radio wave radiation direction of the conductor pattern (arm 1a and arm 1b). The radome 3 is a hemispherical radome provided to protect the antenna section 2 from environmental factors. Radome 3 has a thickness and is close to substrate 1 . In other words, the inside of the radome 3 is not hollow, but filled with vertical stripes in FIG. Radio waves radiated from the conductor patterns (arm 1a and arm 1b) are radiated to the outside through this radome 3 . Of the outer peripheral surface of the radome 3 , a surface corresponding to the bottom surface of the hemisphere (referred to as a facing surface) faces the substrate 1 . Among the outer surfaces of the radome 3, the surface opposite to the facing surface is a surface corresponding to the curved surface of the hemisphere (referred to as a curved surface). Here, the curvature of the curved surface of the hemisphere of the radome 3 may not be the curvature of a true sphere. In other words, the radome 3 may have a convex three-dimensional shape with a smooth curved surface. Moreover, the radome 3 has a structure in which the facing surface of the radome 3 is supported by the adjacent substrate 1 .

Since the radome 3 has a hemispherical shape, it can have uniform resistance to pressure even when it receives pressure from multiple directions such as underwater.

In addition, since the radome 3 has a thick structure, it is possible to increase the strength and prevent deformation of the radome 3 when subjected to pressure from the outside. Moreover, since the radome 3 has a thickness and is configured to be close to the substrate 1, multiple reflection due to space can be reduced.

FIG. 6 shows a sectional view of the radome 3 according to the embodiment of the invention. Of the surfaces facing the substrate 1, the radome 3 has a surface facing the first region 11 of the substrate 1 (a facing surface in a portion of the radome 3 facing the first region). A recessed portion 4 which is hemispherically recessed toward the curved surface is formed. The recess 4 is a hemispherical space. In other words, among the facing surfaces of the radome 3, the surface facing the first region 11 of the substrate 1 is closer to the substrate 1 than the surface facing the second region 12 of the substrate 1, among the facing surfaces of the radome 3. is far away. With this configuration, it is possible to reduce reflection by the radome 3 of radio waves radiated from the conductor pattern formed in the first region 11 facing the thick portion of the radome 3 . In other words, it is possible to promote radiation of short-wavelength, high-frequency radio waves, and to reduce the deterioration of the characteristics of the spiral antenna that radiates radio waves over a wide band and wide angle. Here, the size of the recessed portion 4 (the radius of the first region) is arbitrarily determined according to the desired performance of the antenna, taking into consideration the dielectric constant of the radome 3 and the like.

Here, the surface of the facing surface of the radome 3 that faces the first region 11 is positioned at the center of the facing surface. As a result, the recessed portion 4 is provided in the central portion of the facing surface. By providing the recessed portion 4 in the central portion of the facing surface, in addition to the effect of the hemispherical shape of the radome 3, when receiving pressure from multiple directions, it has uniform resistance to pressure. It has the effect of being able to Although the resistance to pressure from multiple directions is reduced, a configuration in which the concave portion 4 is not provided in the central portion of the facing surface of the radome 3 may be adopted.

Further, since the concave portion 4 is hemispherical, the difference between the amplitude values of the parallel component and the vertical component of the radio waves incident on the radome 3 can be suppressed. Similarly, since the curved surface of the radome 3 is hemispherical, it is possible to suppress the difference between the amplitude values of the parallel component and the vertical component of the radio waves incident on the interface between the radome 3 and the outside from within the radome 3 . The parallel and perpendicular components of the radio wave are defined by whether the electric field component is perpendicular or parallel to the plane on which the incident wave exists.

FIG. 4 is a diagram showing incident angles of radio waves with respect to two types of radome shapes. FIG. 4(a) is a cross-sectional view of the flat plate-shaped radome 3a, and shows the state of the incident angle of radio waves with respect to the flat plate-shaped radome 3a. FIG. 4(b) is a cross-sectional view of the hemispherical radome 3b, showing the angle of incidence of radio waves on the hemispherical radome 3b. As an example, the wave source 9 is a point facing the central portion of the plate-like radome 3a and the hemispherical radome 3b. showing. From FIG. 4, it can be seen that when the antenna radiates radio waves over a wide angle, the incident angle .theta.i to the radome at a wide angle is larger in the flat radome 3a than in the hemispherical radome 3b. Also, although not shown, the incident angle θj from the inside of the radome to the boundary surface between the radome and the outside is similarly larger in the flat radome 3a than in the hemispherical radome 3b at a wide angle.

FIG. 5 is a graph showing an example of power transmittance with respect to the incident angle θi of radio waves to the flat plate radome. In this example, the dielectric constant and thickness of the radome are arbitrary. The horizontal axis is the incident angle θi of the radio wave to the flat plate radome, and the vertical axis is the power transmittance. The vertical component is shown as a solid line and the parallel component is shown as a dashed line. From FIG. 5, it can be seen that as the incident angle .theta.i to the radome increases, the difference in power transmittance between the parallel component and the perpendicular component increases. That is, in the planar radome 3a shown in FIG. 4(a), the incident angle .theta.i to the radome at a wide angle is large, so the difference in power transmittance between the parallel component and the perpendicular component is large. On the other hand, in the hemispherical radome 3b shown in FIG. 4B, the incident angle .theta.i to the radome does not increase even at a wide angle, so it can be seen that the difference in amplitude value between the parallel component and the vertical component can be suppressed. This is a characteristic that does not depend on the wavelength of radio waves. This characteristic also applies to the incident angle θj from inside the radome to the interface between the radome and the outside. In other words, by making the shape of the radome 3 hemispherical as shown in FIG. can be reduced. This makes it possible to maintain the wideband characteristics of the spiral antenna.

Although FIG. 4 shows an example in which the wave source is the point facing the center of the radome, in the spiral antenna, not only the point facing the center of the radome but also the entire conductor pattern serves as the wave source. Therefore, in any wave source, the incident angle .theta.i to the radome and the incident angle .theta.j from the inside of the radome to the interface between the radome and the outside must be brought close to 0 degree. Therefore, by approximating the curvature of the concave portion 4 and the curvature of the curved surface of the radome 3 to the curvature of a true sphere, the incident angle θi to the radome and the incident angle θj from the inside of the radome to the boundary surface between the radome and the outside are obtained in the entire conductor pattern. can approach 0 degrees.

Although the concave portion 4 has a hemispherical shape here, it may have a non-hemispherical configuration. For example, it may have a shape corresponding to the shape of the first region 11 of the substrate 1 . Also, the shape may be different from that of the first region. FIG. 7 is a top view of the substrate showing the recessed portion facing surface 4a which is the position facing the recessed portion 4. FIG. At least a part of the surface of the substrate 1 facing the first region 11 is farther from the substrate 1 than the surface of the substrate 1 facing the second region 12 among the facing surfaces of the radome 3. If it is Therefore, as shown in FIG. 7, the first region may be configured to have recesses 4 only in the direction in which radio waves are desired to be radiated. In FIG. 7, the concave portion facing surface 4a is elliptical, but may be of another shape. Here, of the cross sections perpendicular to the recess facing surface 4a, the curvature of the cross section passing through the long axis of the elliptical shape of the recess facing surface 4a approaches the curvature of a perfect circle. As a result, in a cross section passing through the major axis of the recessed portion facing surface 4a, the above-described characteristic can provide the effect of suppressing the difference in amplitude value between the parallel component and the vertical component in a wide range of the radiated radio waves. be able to. In this way, if the curvature of at least one of the cross sections perpendicular to the substrate 1 of the recessed portion 4 is close to a perfect circle, then in that cross section, the parallel component and the vertical component in a wide range of the radiated radio waves It is possible to obtain the effect of being able to suppress the difference in amplitude value.

Furthermore, since the radome 3 has the recessed portion 4 , it becomes possible to provide the projecting portion of the power feeding portion 7 projecting from the substrate 1 toward the radome 3 inside the recessed portion 4 . Since the projecting portion is provided inside the recessed portion 4 , there is an effect that even if the allowable range of the size of the projecting portion 5 is widened to a range that fits within the recessed portion 4 , it does not interfere with the radome 3 . FIG. 8 shows an enlarged view of the power feeding portion 7. As shown in FIG. FIG. 8(a) shows a configuration in which a portion of the power supply portion 7 protrudes from the substrate 1. As shown in FIG. As shown in the figure, the protruding portion is provided inside the recessed portion 4 of the radome 3 so that it does not interfere with the radome 3 . Therefore, there is an effect that it is not necessary to process the radome 3 into a shape corresponding to the protrusion. Further, FIG. 8B shows a configuration in which part of the power supply portion 7 and the power supply substrate 5 protrude from the substrate 1 . If it is desired to prevent the power supply section 7 from being damaged by an external force such as vibration, a part of the power supply board 5 is made to protrude from the board 1 . In this way, even if a part of the power supply board 5 in addition to the power supply part 7 protrudes from the board 1, the projecting part can be configured so as not to interfere with the radome 3, so that the radome 3 can be processed easily. can be omitted.

Furthermore, since the radome 3 has the concave portion 4, it is possible to reduce the refraction of high-frequency radio waves having a high wavelength shortening rate.

As described above, the antenna device according to the present embodiment reduces deterioration of antenna characteristics even when it is desired to make an antenna that radiates radio waves over a wide band and a wide angle have resistance to pressure from multiple directions. can be made

FIG. 9 shows a top view of substrate 14 of antenna device 200, which is another configuration of antenna device 100 according to the first embodiment. The antenna device 100 has two spiral arms (arm 1a and arm 1b) that are the conductor patterns of the spiral antenna, but the antenna device 200 has one spiral arm that is the conductor pattern of the spiral antenna. (Arm 1c). FIG. 10 is a cross-sectional view of a plane perpendicular to the substrate 10 of the antenna device 200 and passing through the feeding portion 7. FIG. A ground 13 is provided on the surface of the substrate 10 opposite to the surface on which the conductor pattern is formed. Since other points are substantially the same as the antenna device 100, description thereof is omitted here.

Even in the antenna device 200 configured in this way, deterioration of the antenna characteristics can be prevented even if the antenna that radiates radio waves over a wide band and wide angle is desired to be resistant to pressure from multiple directions. can be reduced.

Embodiment 2.
FIG. 11 is a cross-sectional view of the antenna device 300 according to the second embodiment. This cross section is a plane perpendicular to the substrate 1 and passing through the power supply section 7 . The antenna device 300 differs from the antenna device 100 or the antenna device 200 according to Embodiment 1 in the shapes of the concave portion 4 and the concave portion facing surface 4a. Other configurations are substantially the same. Hereinafter, the same reference numerals are given to the same or corresponding configurations as those described in the above embodiments, and the description of those configurations will not be repeated.

FIG. 12 is a top view of the substrate 1 showing the recessed portion facing surface 4a which is the position facing the recessed portion 4. FIG. In the antenna device 100 or the antenna device 200, the concave portion facing surface 4a was circular or elliptical as shown in FIG. In the antenna device 300 , the first region 11 of the substrate 1 is formed with an annular (doughnut-shaped) recessed portion facing surface 4 a that is a region surrounded by two circles. The recessed portion facing surface 4a is an area outside the power feeding portion that is the central portion of the first area 11 and inside the second area. The concave portion facing surface 4a may be an area surrounded by two ellipses or an area surrounded by two polygons.

As a result, the conductor pattern formed on the recess-facing surface 4a of the substrate 1 radiates radio waves having a longer wavelength and a lower frequency than the conductor pattern formed in the central portion of the first region 11. . Also, the conductor pattern formed on the concave portion facing surface 4a of the substrate 1 radiates radio waves having a shorter wavelength and a higher frequency than the conductor pattern formed on the second region. In other words, the surface 4a facing the concave portion of the substrate 1 radiates radio waves in the middle range at the operating frequency.

A concave portion 4 is formed on a surface of the substrate 1 facing the concave portion facing surface 4 a on the facing surface of the radome 31 . Here, since the recessed portion facing surface 4a is an annular region outside the power supply portion that is the central portion of the first region 11 and inside the second region, the radome 31 is formed in an annular shape. A recessed recess 4 is formed. The contour of the recessed portion 4 on the side opposite to the surface facing the substrate 1 is rounded. As shown in FIG. 11, the recessed portion 4 has a semicircular cross-sectional shape perpendicular to the recessed portion facing surface 4a. That is, the recessed portion 4a has a shape obtained by arranging semicircles on the circumference of a circle.

At this time, it is preferable to bring the curvature of the semicircle of the cross section perpendicular to the concave portion facing surface 4a close to the curvature of a perfect circle. As a result, it is possible to obtain the effect of suppressing the difference between the amplitude values of the parallel component and the vertical component in the wide area of the radiated radio waves due to the characteristics described in the first embodiment. Thus, if the curvature of the cross section of the recessed portion 4 perpendicular to the substrate 1 is close to a perfect circle, it is possible to suppress the difference in the amplitude value between the parallel component and the vertical component in the wide area of the radiated radio wave in the cross section. You can get the effect of being able to

In this manner, the surface of the radome 31 facing the first region 11 can be configured to have the recessed portion 4 only in a portion where radio wave radiation is desired to be promoted. In the antenna device 300, by forming the ring-shaped recessed portion 4 on the facing surface of the radome 3, it is possible to promote radiation in the middle range at the operating frequency. In addition, by rounding the outer shape of the concave portion 4 on the side opposite to the surface facing the substrate 1, it is possible to suppress the difference in the amplitude value between the parallel component and the vertical component in the wide area of the radiated radio wave. Obtainable.

As described above, in the antenna device 300 according to the present embodiment as well, even if the antenna that radiates radio waves over a wide band and at a wide angle is desired to have resistance to pressure from multiple directions, the deterioration of the antenna characteristics can be prevented. can be reduced.

1, 10 spiral substrate,
1a, 1b arms,
2 antenna part,
3 radome,
3a tabular radome,
3b hemispherical radome,
4 recess,
4a concave portion facing surface,
5 feeding substrate,
6 power supply connector,
7 power supply,
8 antenna case,
9 wave source,
11 first region,
12 second area,
13 ground 100, 200, 300 antenna device

Claims (8)

a substrate, a conductor pattern of a spiral antenna formed on the substrate, a feeder connected to the conductor pattern, and a hemispherical radome provided in the radio wave radiation direction of the conductor pattern,
The conductor pattern formed in a first region inside the outer circumference of the substrate including the power feeding portion of the substrate radiates radio waves of a first frequency, and is outside the first region of the substrate. The conductor pattern formed in a certain second region radiates radio waves of a second frequency lower than the first frequency,
At least part of the surface of the radome facing the first region of the facing surface facing the substrate is more sensitive than the surface facing the second region of the facing surface An antenna device having a long distance from the substrate. 2. The antenna device according to claim 1, wherein said radome has a hemispherical recess formed on said facing surface in a portion facing said first region. 3. The antenna device according to claim 2, wherein the feeding portion is formed in the central portion of the conductor pattern, and the recessed portion is provided in the central portion of the facing surface. 2. The antenna device according to claim 1, wherein the facing surface of the radome has a concave portion formed on a surface facing a region outside the feeding portion and inside the second region in the substrate. 5. The antenna device according to claim 4, wherein a region of said substrate outside said feeding portion and inside said second region is annular. 6. The antenna device according to any one of claims 1 to 5, wherein the feeding section has a protruding section that protrudes from the substrate toward the radome. The antenna device according to any one of claims 1 to 6, wherein the first region has a circular shape centered on the feeding portion. 8. The antenna device according to claim 7, wherein the second area is inside a circle centered on the feeding portion having a radius larger than that of the first area and outside the first area.

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