JP6278500B2 - Dielectric loaded antenna - Google Patents

Description

  The present invention relates to a dielectric loaded antenna.

  In recent years, millimeter wave radar devices that detect moving objects (vehicles, people, etc.) using millimeter wave radio waves have become widespread. An antenna mounted on such a millimeter wave radar device is required to have a characteristic capable of covering a relatively wide range with high gain and low loss, and is particularly required to be small.

  In order to achieve the above object, the present inventors have developed a dielectric-loaded antenna in which a dielectric lens is loaded on a coaxial groove horn antenna that has improved the wide-angle directivity by exciting and controlling the coaxial waveguide mode ( Non-patent document 1).

  As shown in FIG. 8A, the conventional example described in Non-Patent Document 1 includes a primary radiator 100 composed of a coaxial groove horn antenna, and a dielectric lens loaded in the opening (right side in the figure) of the primary radiator 100. It consists of 110. The primary radiator 100 is formed by forming a groove 102 having a coaxial structure around an opening in the circular waveguide 101. The dielectric lens 110 has an annular shape in which the thickness of the central portion is sufficiently smaller than the thickness of the peripheral portion, and the first surface 111 inserted into the inside from the opening of the primary radiator 100 and the primary radiator 100 The second surface 112 exposed to the outside from the opening is formed in a different curved surface shape.

  FIG. 8B shows a comparison between the measured value and the calculated value of the radiation pattern at 24 GHz of the conventional example. In the figure, the horizontal axis indicates the angle from the center of the circular waveguide 101, and the vertical axis indicates the gain. Further, in the figure, a solid line I indicates a measured value on the H plane, a one-dot broken line II indicates a measured value on the E plane, a broken line III indicates a calculated value on the H plane, and a dotted line IV indicates a calculated value on the E plane. As is apparent from the respective measured values and calculated values, the gain reduction from the front direction in the ± 60 ° direction is about several decibels, and a sufficiently wide radiation characteristic is obtained.

Akihiro Kobayashi, Akihiro Omori, Hiroyuki Deguchi, Mikio Tsuji, “Dielectric Lens Horn Antenna for Wide Angle Beam Irradiation”, Proceedings of the IEICE General Conference 2012 Communications (1), 58

  The conventional example described in Non-Patent Document 1 can obtain sufficiently wide-angle radiation characteristics while achieving downsizing as described above. However, when the dielectric lens is made of a synthetic resin material (for example, polyethylene), the shape of the first surface 111 and the second surface 112 is complicated, which increases the manufacturing cost such as mold costs. Occurs.

  The present invention has been made in view of the above problems, and an object of the present invention is to obtain a compact and wide-angle radiation characteristic while suppressing the complexity of the shape as compared with the prior art.

The dielectric-loaded antenna of the present invention is a dielectric-loaded antenna including a feeding surface and a radiation surface for radiating radio waves, the waveguide including an opening opened from the feeding surface side toward the radiation surface side, and the conductor. A primary radiator in which a groove having a coaxial structure is formed around the opening on the radiation surface side of the wave portion; and a dielectric lens loaded on the radiation surface side of the primary radiator, the dielectric lens Includes a main part formed in a truncated cone shape that covers the opening and the groove of the primary radiator and protrudes forward, and an insertion part that protrudes from the rear surface of the main part and is inserted into the groove, In addition, a gap is provided between the distal end of the insertion portion and the inner bottom surface of the groove, and the main portion and the insertion portion are integrally formed of a dielectric material.

  In this dielectric-loaded antenna, it is preferable that the opening and the waveguide section are coaxial.

  In this dielectric-loaded antenna, it is preferable that the dielectric lens has a conical surface formed on the rear surface of the main portion facing the opening.

In this dielectric-loaded antenna, the dielectric lens is preferably formed so that the center of the bottom surface of the main portion and the apex of the conical surface are positioned coaxially with the waveguide portion and the groove.

  The dielectric-loaded antenna of the present invention includes a truncated cone-shaped main portion and an insertion portion inserted into the groove of the primary radiator, and both the main portion and the insertion portion are integrally formed of a dielectric material. Since the dielectric lens is loaded on the primary radiator, the shape of the dielectric lens is simplified compared to the conventional example. For this reason, it is possible to suppress the complexity of the shape, and it is possible to obtain a more compact and wide-angle radiation characteristic than before.

1 shows an embodiment of a dielectric loaded antenna according to the present invention, where (a) is a cross-sectional view and (b) is a characteristic diagram of a radiation pattern at 24 GHz. It is a perspective view same as the above. It is a frequency characteristic figure of voltage standing wave ratio same as the above. 4 shows another embodiment of a dielectric loaded antenna according to the present invention, wherein (a) is a cross-sectional view and (b) is a characteristic diagram of a radiation pattern at 24 GHz. FIG. 7 shows a comparative example 1 of a dielectric loaded antenna according to the present invention, in which (a) is a cross-sectional view and (b) is a characteristic diagram of a radiation pattern at 24 GHz. Comparative Example 2 of the dielectric loaded antenna according to the present invention is shown, (a) is a cross-sectional view, and (b) is a characteristic diagram of a radiation pattern at 24 GHz. Comparative Example 3 of the dielectric loaded antenna according to the present invention is shown, (a) is a cross-sectional view, and (b) is a characteristic diagram of a radiation pattern at 24 GHz. A conventional example is shown, (a) is a sectional view, and (b) is a characteristic diagram of a radiation pattern at 24 GHz.

  Hereinafter, embodiments of a dielectric loaded antenna according to the present invention will be described in detail with reference to the drawings.

  The dielectric loaded antenna of this embodiment includes a primary radiator 1 in which a groove 11 having a coaxial structure is formed around an opening on the front side of a circular waveguide, as shown in FIGS. And a dielectric lens 2 loaded on the front side of the primary radiator 1. However, the front side of the primary radiator 1 is the free space side, that is, the traveling direction side of the radio wave radiated from the dielectric lens side through the waveguide, and the radio wave is radiated, and the rear side of the primary radiator 1 is the feeding surface side. It becomes.

  The primary radiator 1 is made of a metal material, and a central waveguide 10 and an annular groove 11 are formed coaxially. The waveguide 10 is a member that propagates radio waves from the feeding surface side toward the radiation surface side (front side). The waveguide 10 in this embodiment is a cylindrical shape that draws a uniform circle along the long axis (center axis) of the dielectric-loaded antenna that connects the radiation surface and the power feeding surface, from the power feeding surface side to the radiation surface side. It has an opening that opens toward it. However, the shape of the waveguide 10 is not limited to a cylindrical shape, and if the radiation surface and the feeding surface exist on the same circumference along the long axis of the dielectric loaded antenna connecting the radiation surface and the feeding surface, Good. From the viewpoint of performing radio wave propagation uniformly, the waveguide 10 is preferably on the same circumference and has a uniform shape. Specifically, the waveguide 10 may be a prismatic shape in addition to the cylindrical shape, and in particular, the cylindrical shape is preferable from the above viewpoint. Here, the wall separating the waveguide 10 and the groove 11 is referred to as an inner peripheral wall 12, and the outer peripheral wall of the groove 11 is referred to as an outer peripheral wall 13. The height dimension from the inner bottom surface of the groove 11 to the front ends of the inner peripheral wall 12 and the outer peripheral wall 13 is slightly larger than the height dimension to the front end of the outer peripheral wall 13 (see FIG. 1A). ).

  The dielectric lens 2 is formed integrally from a material (for example, a synthetic resin material such as polyethylene) in which a truncated cone-shaped main portion 20 and a cylindrical insertion portion 21 protruding from the rear surface of the main portion 20 are dielectric materials. Being done. The main portion 20 is a member for radiating a radio wave propagating through the waveguide 10 in the dielectric lens 2 to the free space side, and the shape of this member determines the radiation angle of the radio wave. In the main portion 20 in the present embodiment, the radius r1 of the bottom surface on the rear side substantially coincides with the radius r2 of the primary radiator 1 (see FIG. 1A).

  The insertion portion 21 is a member for radiating radio waves propagating through the waveguide 10 to the free space side, and is for expanding the radiation angle. The insertion portion 21 in the present embodiment has a radial width dimension slightly smaller than the width dimension of the groove 11, and is inserted into the groove 11 from the front. Further, the insertion portion 21 has a height dimension in the front-rear direction smaller than the depth dimension of the groove 11. Therefore, when the rear surface of the main part 20 hits the front end of the outer peripheral wall 13 of the primary radiator 1, a gap is generated between the tip (rear end) of the insertion part 21 and the inner bottom surface of the groove 11. Further, the dielectric lens 2 has a conical surface 22 formed on the rear surface of the main portion 20 facing the opening (waveguide 10).

  The dielectric lens 2 in this embodiment is formed so that the center of the bottom surface of the main portion 20 and the apex of the conical surface 22 are positioned coaxially with the waveguide 10 and the groove 11. As described above, when the center of the bottom surface of the main portion 20 and the apex of the conical surface 22 are formed so as to be coaxial with the waveguide 10 and the groove 11, the structure is symmetrical with respect to the central axis, so that the directivity is uniform. Since an effect is acquired, it is preferable.

  Further, in the present embodiment, the shape of the dielectric lens 2 is such that the apex located on the front side is a horizontal shape, but the inclined surface of the dielectric lens 2 facing the apex is not recessed on the rear side. If it is. For example, the shape where both inclined surfaces were connected on the straight line or the curve in the state protruded to the front side may be sufficient.

  In the dielectric lens 2, from the viewpoint of improving the radiation characteristics, it is preferable that the radius r1 of the main part and the radius r2 to the outermost contour of the waveguide 10 and the primary radiator 1 are r1 = r2.

  Here, in developing the dielectric loaded antenna according to the present embodiment, a brief description will be given of comparative examples variously studied by the present inventors. However, all of the primary radiators 1 in the following comparative examples are the same as the primary radiator 1 in the present embodiment.

(Comparative Example 1)
The first comparative example 1 examines the influence of simplification (planarization) of the first surface 111 of the dielectric lens 110 in the conventional example on the radiation characteristics. Specifically, in Comparative Example 1, as shown in FIG. 5A, an insertion portion 113 is provided on the first surface 111 of the dielectric lens 110 in the conventional example, and the inside of the insertion portion 113 is a flat surface. is there. FIG. 5B shows the calculated value of the radiation pattern of Comparative Example 1 at 24 GHz. In the figure, the horizontal axis indicates the angle from the center of the waveguide 10, and the vertical axis indicates the gain. In the figure, a dotted line I indicates a calculated value of the H plane, a solid line II indicates a calculated value of the E plane, and a broken line III indicates a calculated value of the cross polarization component.

  As can be seen from FIG. 5B, although the radiation characteristics are slightly changed as compared with the conventional example, the effect of the simplification (planarization) of the first surface 111 of the dielectric lens 110 on the radiation characteristics is small. Conceivable.

(Comparative Example 2)
The second comparative example 2 examines the influence of the simplification of the second surface 112 of the dielectric lens 110 in the comparative example 1 on the radiation characteristics. Specifically, in Comparative Example 2, as shown in FIG. 6A, the cross section of the second surface 112 of the dielectric lens 110 in Comparative Example 1 is simplified by approximating a straight line. FIG. 6B shows the calculated value of the radiation pattern of Comparative Example 2 at 24 GHz. In the figure, the horizontal axis indicates the angle from the center of the waveguide 10, and the vertical axis indicates the gain. In the figure, a dotted line I indicates a calculated value of the H plane, a solid line II indicates a calculated value of the E plane, and a broken line III indicates a calculated value of the cross polarization component.

  As can be seen from FIG. 6B, the influence of simplification of the second surface 112 of the dielectric lens 110 on the radiation characteristics is considered to be small.

(Comparative Example 3)
The third comparative example 3 examines further simplification of the shape of the dielectric lens 110 in the comparative example 2. Specifically, in Comparative Example 3, as shown in FIG. 7A, the second surface 112 of the dielectric lens 110 in Comparative Example 2 is brought close to a truncated cone shape. FIG. 7B shows the calculated value of the radiation pattern of Comparative Example 3 at 24 GHz. In the figure, the horizontal axis indicates the angle from the center of the waveguide 10, and the vertical axis indicates the gain. In the figure, a dotted line I indicates a calculated value of the H plane, a solid line II indicates a calculated value of the E plane, and a broken line III indicates a calculated value of the cross polarization component.

  As can be seen from FIG. 7B, the radiation patterns of the E plane and the H plane agree very well, and almost no gain decrease from the front direction is seen up to about ± 55 °. Moreover, the peak value of the cross polarization component is a low level of -20 dB or less. However, since the dielectric lens 110 of Comparative Example 3 has a special shape in which the wedge-shaped groove 114 is provided around the central axis of the second surface 112, it is disadvantageous for suppressing the manufacturing cost.

  FIG. 4A is a sectional view showing another embodiment of the dielectric loaded antenna according to the present invention. In this embodiment, the wedge-shaped groove 114 in Comparative Example 3 is filled with a dielectric, and the embodiment shown in FIG. 1A differs from the embodiment shown in FIG. The only difference is that they are formed on a flat surface.

  FIG. 4B shows the calculated value of the radiation pattern at 24 GHz in this embodiment. In the figure, the horizontal axis indicates the angle from the center of the waveguide 10, and the vertical axis indicates the gain. In the figure, a dotted line I indicates a calculated value of the H plane, a solid line II indicates a calculated value of the E plane, and a broken line III indicates a calculated value of the cross polarization component.

  As can be seen from FIG. 4B, there is almost no difference between the radiation pattern and the cross polarization component of Comparative Example 3.

  Therefore, a dielectric lens 2 in which a main part 20 having a truncated cone shape and an insertion part 21 inserted into the groove 11 of the primary radiator 1 are integrally formed of a dielectric material is loaded on the primary radiator 1. As a result, it is possible to obtain a more compact and wide-angle radiation characteristic than before. In addition, since the shape of the dielectric lens 2 is simplified as compared with the conventional example, the complexity of the shape can be suppressed.

  Here, in the embodiment shown in FIG. 4, the voltage standing wave ratio at 24 GHz is about 1.9 (reflection coefficient is −10.2 dB).

  On the other hand, in the embodiment shown in FIG. 1, the voltage standing wave ratio is improved (decreased) while suppressing deterioration of the characteristics of the radiation pattern as much as possible by forming a conical surface 22 on the rear surface of the main portion 20 that faces the opening. can do.

  FIG. 3 shows the frequency characteristics of the voltage standing wave ratio calculated when the surface facing the opening on the rear surface of the main portion 20 is a plane (solid line II) and when it is a conical surface (broken line I). As can be seen from FIG. 3, the value of the voltage standing wave ratio at 24 GHz is improved on the conical surface 22 than on the flat surface.

  Moreover, FIG.1 (b) has shown the calculated value of the radiation pattern in 24 GHz of embodiment shown to Fig.1 (a). In the figure, the horizontal axis indicates the angle from the center of the waveguide 10, and the vertical axis indicates the gain. In the figure, a dotted line I indicates a calculated value of the H plane, a solid line II indicates a calculated value of the E plane, and a broken line III indicates a calculated value of the cross polarization component.

  As can be seen from FIG. 1 (b), the gain reduction from the front direction in the ± 60 ° direction is about several decibels, and a wide-angle radiation characteristic is obtained.

  In addition, since the dielectric loaded antenna of the present embodiment is provided with the groove 11 between the primary radiator 1 and the insertion portion 21 which is a constituent member of the dielectric lens 2, compared with the case without the groove, It is possible to reduce the influence of the reflected wave when the lens frequency changes. Therefore, as a result, an effect that a wide frequency characteristic can be obtained is obtained.

1 Primary radiator 2 Dielectric lens
10 Waveguide (aperture)
11 groove
20 Main part
21 Insertion section

Claims (4)

A dielectric loaded antenna comprising a feeding surface and a radiation surface for radiating radio waves,
A primary radiator in which a waveguide having an opening opened from the feeding surface side toward the radiation surface side, a groove having a coaxial structure around the opening on the radiation surface side of the waveguide portion, and the primary A dielectric lens loaded on the radiation surface side of the radiator,
The dielectric lens includes a main part formed in a truncated cone shape that covers the opening and the groove of the primary radiator and protrudes forward, and an insertion part that protrudes from the rear surface of the main part and is inserted into the groove. And a gap is provided between the distal end of the insertion portion and the inner bottom surface of the groove,
The dielectric-loaded antenna, wherein the main portion and the insertion portion are integrally formed from a material that is a dielectric.   The dielectric-loaded antenna according to claim 1, wherein the opening and the waveguide section are coaxial.   The dielectric-loaded antenna according to claim 1 or 2, wherein the dielectric lens has a conical surface formed on a rear surface of the main portion facing the opening. 4. The dielectric according to claim 3, wherein the dielectric lens is formed so that a center of a bottom surface of the main portion and a vertex of the conical surface are positioned coaxially with the waveguide portion and the groove. Loading antenna.

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