JP6563805B2 - Antenna, method for manufacturing cylindrical periodic structure, cylindrical periodic structure, and sheet for cylindrical periodic structure - Google Patents

Description

  The present invention relates to an antenna, a method for manufacturing a cylindrical periodic structure, a cylindrical periodic structure, and a sheet for a cylindrical periodic structure.

  For example, an antenna for a mobile communication base station such as a mobile phone includes an antenna element that transmits and receives a radio signal, a reflector for adjusting directivity, and a director (a parasitic element). It is known (see, for example, Patent Document 1).

JP 2006-229337 A JP 2012-114550 A JP 2011-223201 A JP 2012-049779 A JP 2012-049769 A

However, since the antenna needs to include a reflector and a director in addition to the antenna element, there is a problem in that the weight of the entire antenna increases and the manufacturing cost increases.
The present invention has been made in view of the above problems, and an object thereof is to enable adjustment of the directivity of an antenna element with a simple configuration.

  An antenna according to an aspect of the present invention includes an antenna element, and a cylindrical periodic structure that includes a plurality of unit cells periodically arranged in a circumferential direction and an axial direction, and covers the antenna element. The unit cell includes a loop outer conductor, an inner conductor disposed inside the loop outer conductor, and a loop slot formed between the loop outer conductor and the inner conductor, and the cylindrical period The structure includes an antenna including a plurality of types of unit cells having different outer peripheral lengths of the loop slot.

  A manufacturing method of a cylindrical periodic structure according to an aspect of the present invention is a manufacturing method of a cylindrical periodic structure that includes a plurality of unit cells that are periodically arranged in a circumferential direction and an axial direction and covers an antenna element. A sheet provided with a plurality of unit cells periodically arranged in one direction and the other direction, wherein the unit cell includes a loop outer conductor, an inner conductor disposed inside the loop outer conductor, and Preparing a sheet including a plurality of types of unit cells having a loop slot formed between the outer loop conductor and the inner conductor and having different outer peripheral lengths of the loop slot; and preparing a core rod The step of laminating a plurality of coating layers on the peripheral surface of the core rod, and the inner cell or the outer peripheral surface of any one of the plurality of coating layers, the plurality of unit cells are One coating layer The wound sheet process and method of manufacturing a tubular periodic structure comprising a so as to be arranged along the circumferential direction and the axial direction.

  A manufacturing method of a cylindrical periodic structure according to an aspect of the present invention is a manufacturing method of a cylindrical periodic structure that includes a plurality of unit cells that are periodically arranged in a circumferential direction and an axial direction and covers an antenna element. A base cell, a unit cell having a loop outer conductor, an inner conductor disposed inside the loop outer conductor, and a loop slot formed between the loop outer conductor and the inner conductor And, the step of printing a plurality of types of the unit cells having different outer peripheral lengths of the loop slot along the circumferential direction of the outer peripheral surface of the basic cylinder, and the outer peripheral surface of the plurality of unit cells, Forming a protective layer for protecting the unit cell. A method for manufacturing a cylindrical periodic structure.

  A cylindrical periodic structure according to one embodiment of the present invention is a cylindrical periodic structure that covers an antenna element, and the directivity of the antenna element is changed by covering the antenna element with the cylindrical periodic structure. A cylindrical periodic structure comprising a plurality of unit cells periodically arranged in the circumferential direction and the axial direction.

  The cylindrical periodic structure sheet according to one aspect of the present invention is a cylindrical periodic structure sheet disposed along the circumferential direction as a constituent member of the cylindrical periodic structure covering the antenna element, The unit cell includes a plurality of unit cells periodically arranged in one direction that is the circumferential direction and the other direction, and the unit cell includes a loop outer conductor, an inner conductor disposed inside the loop outer conductor, and A sheet for a cylindrical periodic structure having a plurality of types of unit cells, each having a loop slot formed between an outer conductor of a loop and a loop slot formed between the inner conductors, and having different outer peripheral lengths.

  According to the present invention, the directivity of an antenna element can be adjusted with a simple configuration.

The antenna which concerns on 1st Embodiment of this invention is shown, (a) is a top view, (b) is a sectional side view. It is an expanded view of a frequency selection board. The unit cell single-piece | unit is shown, (a) is a front view, (b) is a perspective view. It is a cross-sectional schematic diagram in the use condition which curved the frequency selection board. In the case where all the unit cells arranged on the frequency selection plate have loop slots with the maximum outer peripheral length, the FSS characteristics are shown when the frequency selection plate is arranged on a plane. In the case where all the unit cells arranged on the frequency selection plate have loop slots with the minimum outer peripheral length, the FSS characteristics are shown when the frequency selection plate is arranged on a plane. It is explanatory drawing which shows the manufacturing method of a cylindrical periodic structure. It is explanatory drawing which shows the manufacturing method of a cylindrical periodic structure. It is explanatory drawing which shows the other manufacturing method of a cylindrical periodic structure. The directivity of the antenna element of the comparative example 1 is shown, (a) is horizontal surface directivity, (b) is vertical surface directivity. The directivity of the antenna element of the comparative example 2 is shown, (a) is horizontal surface directivity, (b) is vertical surface directivity. The directivity of the antenna element of this embodiment is shown, (a) is horizontal surface directivity, (b) is vertical surface directivity. The directivity of the antenna element when the slot outer peripheral length difference is changed is shown. (A) and (b) are horizontal plane directivity and vertical plane directivity when the slot outer peripheral length difference is 4.0, (c ) And (d) are horizontal plane directivity and vertical plane directivity when the slot outer peripheral length difference is 6.0. FIG. 6 shows changes in the directivity of the antenna element when the slot outer peripheral length difference is changed, where (a) shows changes in the beam widths of the horizontal plane directivity and vertical plane directivity, and (b) shows the F / of horizontal plane directivity. This is a change of B. The directivity of the antenna element when the number of rows of unit cells in the circumferential direction is changed is shown. (A) is the horizontal plane directivity, and (b) is the vertical plane directivity. It is a cross-sectional schematic diagram which shows the modification of a frequency selection board. It is an enlarged view which shows the modification of a unit cell. It is an enlarged view which shows the other modification of a unit cell. It is sectional drawing of the cylindrical periodic structure of the antenna which concerns on 2nd Embodiment of this invention. The directivity of the antenna element of 2nd Embodiment is shown, (a) is horizontal surface directivity, (b) is vertical surface directivity. The directivity of the antenna element when the center angle of the reflecting plate is changed in the second embodiment is shown, and (a) and (b) are the horizontal plane directivity and vertical plane directivity when the center angle is 51 °. , (C) and (d) are the horizontal plane directivity and vertical plane directivity when the central angle is 102 °. The change of the directivity of the antenna element when the center angle of the reflector is changed is shown. (A) shows changes in the beam widths of the horizontal plane directivity and the vertical plane directivity, and (b) shows the horizontal plane directivity. This is a change in F / B. It is a cross-sectional schematic diagram of the cylindrical periodic structure of the antenna which concerns on 3rd Embodiment of this invention. The directivity of the antenna element of 3rd Embodiment is shown, (a) is horizontal surface directivity, (b) is vertical surface directivity. It is a cross-sectional schematic diagram of the cylindrical periodic structure of the antenna which concerns on 4th Embodiment of this invention. It is a side view of the frequency selection plate 4 of FIG. 25, (a) is a side view seen from the 0 degree direction, (a) is a side view seen from the 180 degree direction. The directivity of the antenna element of 4th Embodiment is shown, (a) is horizontal surface directivity, (b) is vertical surface directivity. It is a cross-sectional schematic diagram of the cylindrical periodic structure of the antenna which concerns on 5th Embodiment of this invention. It is the side view which looked at the frequency selection board in the cylindrical periodic structure of FIG. 28 from the 0 degree direction. The directivity of the antenna element of 5th Embodiment is shown, (a) is horizontal surface directivity, (b) is vertical surface directivity. It is a cross-sectional schematic diagram of the cylindrical periodic structure of the antenna which concerns on 6th Embodiment of this invention. FIG. 32 is a side view of the frequency selection plate in the cylindrical periodic structure of FIG. 31, (a) is a side view seen from the 0 ° direction, and (a) is a side view seen from the 180 ° direction. The directivity of the antenna element of 6th Embodiment is shown, (a) is horizontal surface directivity, (b) is vertical surface directivity. It is a cross-sectional schematic diagram of the cylindrical periodic structure of the antenna which concerns on 7th Embodiment of this invention. The directivity of the antenna element of 7th Embodiment is shown, (a) is horizontal surface directivity, (b) is vertical surface directivity. It is a cross-sectional schematic diagram of the cylindrical periodic structure of the antenna which concerns on 8th Embodiment of this invention. It is a side view of the frequency selection plate in the cylindrical periodic structure of FIG. 36, (a) is a side view seen from the 0 ° direction, (a) is a side view seen from the 180 ° direction. The directivity of the antenna element of 8th Embodiment is shown, (a) is horizontal surface directivity, (b) is vertical surface directivity. It is a cross-sectional schematic diagram of the cylindrical periodic structure of the antenna which concerns on 9th Embodiment of this invention. It is the side view of the frequency selection board in the cylindrical periodic structure of FIG. 39, (a) is the side view seen from the 0 degree direction, (a) is the side view seen from the 180 degree direction. The directivity of the antenna element of 9th Embodiment is shown, (a) is horizontal surface directivity, (b) is vertical surface directivity. It is a cross-sectional schematic diagram of the cylindrical periodic structure of the antenna which concerns on 10th Embodiment of this invention. It is a side view of the frequency selection board in the cylindrical periodic structure of FIG. 42, (a) is a side view seen from the 0 degree direction, (a) is a side view seen from the 180 degree direction. The directivity of the antenna element of 10th Embodiment is shown, (a) is horizontal surface directivity, (b) is vertical surface directivity.

[Description of Embodiment of the Present Invention]
First, the contents of the embodiment of the present invention will be listed and described.
(1) As a result of earnest research, the inventor of the present application, due to the difference in the outer peripheral length of loop slots formed in a plurality of unit cells periodically arranged in the circumferential direction and the axial direction in the cylindrical periodic structure, The present inventors have found that the directivity of the antenna element changes, and have completed the embodiment of the present invention based on such knowledge.

That is, an antenna according to an embodiment of the present invention includes an antenna element and a cylindrical periodic structure that includes a plurality of unit cells periodically arranged in the circumferential direction and the axial direction and covers the antenna element. The unit cell includes a loop outer conductor, an inner conductor disposed inside the loop outer conductor, and a loop slot formed between the loop outer conductor and the inner conductor, and the tube The mold periodic structure includes a plurality of types of unit cells having different outer peripheral lengths of the loop slots.
According to the antenna of (1) above, the directivity of the antenna element can be adjusted with a simple configuration in which the antenna element is covered with a cylindrical periodic structure having a plurality of types of unit cells having different outer peripheral lengths of the loop slot. Can do.

(2) In the antenna, the cylindrical periodic structure is preferably formed in a true cylindrical shape.
As a result of further earnest research, the inventor of the present application has found that the directivity of the antenna element is effectively changed by making the cylindrical periodic structure into a true cylindrical shape. Based on this finding, the above (2) An embodiment of the invention has been completed. Thereby, the directivity of the antenna element can be adjusted.

(3) In the antenna, the cylindrical periodic structure has a plurality of divided regions divided in a circumferential direction, and each divided region includes a predetermined number of the unit cells, It is preferable that the predetermined number of unit cells in the divided region is formed such that the outer peripheral length of the loop slot decreases stepwise from one circumferential direction to the other circumferential side of the divided region.

  As a result of further diligent research, the inventor of the present application has formed a loop slot with an outer peripheral length that gradually decreases from one side in the circumferential direction to the other side in the circumferential direction of the predetermined number of unit cells in each divided region. Thus, the directivity of the antenna element was found to change effectively, and the embodiment of the invention according to the above (3) was completed based on this knowledge. Thereby, the directivity of the antenna element can be adjusted effectively.

(4) In the antenna, the cylindrical periodic structure is formed such that an outer shape in a cross-sectional view orthogonal to an axis thereof is a non-circular shape having at least two focal points separated from each other. Each of the focal points has a curved region formed by a quadratic curve or a group of straight lines approximating the quadratic curve, and each curved region includes a predetermined number of the unit cells, The predetermined number of unit cells in the bent region may be formed such that the outer peripheral length of the loop slot decreases stepwise from one circumferential direction side to the other circumferential side of the bent region.

  As a result of further earnest research, the inventor of the present invention has made the cross-sectional outer shape of the cylindrical periodic structure into a non-circular shape having two focal points, and the circumferential direction from one circumferential side of the bending region formed around each focal point. It has been found that the beam width of the horizontal plane directivity of the antenna element becomes narrower by forming the outer peripheral length of the loop slot to be gradually reduced toward the other side, and based on such knowledge, the implementation of the invention according to the above (4) Completed the form. Thereby, the beam width of the horizontal directivity of the antenna element can be narrowed.

(5) In the antenna, the cylindrical periodic structure further includes a non-arrangement region in which the unit cell is not disposed in a part of the circumferential direction, and one end in the circumferential direction of the non-arrangement region has one It is preferable that one side in the circumferential direction of the bent region is connected, and the other side in the circumferential direction of the non-arranged region is connected to one side in the circumferential direction of the other bent region.

  As a result of further earnest study, the inventor of the present application has determined that a part of the cylindrical periodic structure in the circumferential direction is a non-arranged region where no unit cells are arranged, and each of the circumferential ends of the non-arranged region has a circumference of the bent region. Based on this knowledge, we found that the beam width of the antenna element in the horizontal plane is narrowed by connecting the unit cell side part having a loop slot whose outer peripheral length is larger than that of the other loop slot. Thus, the embodiment of the invention according to the above (5) has been completed. Thereby, the beam width of the horizontal directivity of the antenna element can be narrowed.

(6) In the antenna, the predetermined number of unit cells are arranged so as to gradually move away from a direction in which the directivity of the antenna element is directed from the one side in the circumferential direction toward the other side in the circumferential direction. Is preferred.
As a result of further earnest research, the inventor of the present application has arranged the predetermined number of unit cells such that the outer peripheral length of the loop slot becomes smaller as the distance from the direction in which the directivity of the antenna element is directed sequentially becomes smaller. It was found that the directivity was improved, and the embodiment of the invention according to the above (6) was completed based on such knowledge. Thereby, the directivity of the antenna element can be adjusted more effectively.

(7) In the antenna, the outer peripheral length of the loop slot is preferably 0.55λ or less (λ is a free space wavelength in a desired frequency band).
As a result of further earnest research, the inventor of the present application has found that the frequency selection plate having the characteristic of allowing electromagnetic waves to pass in a frequency band higher than the desired frequency band when arranged in a plane, that is, the outer circumference of the loop slot corresponds to the free space wavelength of the desired frequency band It was found that the directivity of the antenna element was improved by using a frequency selection plate that was shorter than the length to be used, and the embodiment of the invention according to (7) was completed based on this knowledge. Thereby, the directivity of the antenna element can be adjusted more effectively.

(8) In the antenna, in a cross-sectional view orthogonal to the axis of the cylindrical periodic structure, the loop slots of the plurality of unit cells sandwich an imaginary straight line passing through the center of the cylindrical periodic structure. It is preferably formed in line symmetry. In this case, the cylindrical periodic structure can be further simplified.

(9) In the antenna, it is preferable that the plurality of unit cells are arranged such that distances between centers of loop slots of the unit cells adjacent in the circumferential direction are the same. In this case, the cylindrical periodic structure can be further simplified.

(10) In the antenna, it is preferable that the slot widths of the loop slots in the plurality of unit cells are the same. In this case, the cylindrical periodic structure can be further simplified.

(11) In the antenna, the cylindrical periodic structure may further include a reflector disposed in a part of the circumferential direction, and the reflector may include the reflector in at least one of the plurality of divided regions. It is preferable that it is arranged at a position on the other side in the circumferential direction or at a position close thereto.
As a result of further earnest research, the inventor of the present application made a part of the cylindrical periodic structure in the circumferential direction a reflecting plate, and the reflecting plate has an outer peripheral length that is the other side in the circumferential direction of the divided region, that is, the other loop slot. It has been found that the F / B in the directivity of the antenna element is improved by disposing it at the position of the unit cell where the small loop slot is formed or at a position close thereto, and based on this knowledge, the invention according to the above (11) An embodiment was completed. Thereby, F / B in the directivity of the antenna element can be improved.

(12) In the antenna, it is preferable that the outer peripheral lengths of the loop slots in the plurality of unit cells arranged adjacent to each other in the axial direction of the cylindrical periodic structure are the same. In this case, the cylindrical periodic structure can be further simplified.

(13) In the antenna, it is preferable that the cylindrical periodic structure is a radome. In this case, the antenna can have a simple configuration.

(14) A method for manufacturing a cylindrical periodic structure according to an embodiment of the present invention includes a plurality of unit cells periodically arranged in a circumferential direction and an axial direction, and manufacturing a cylindrical periodic structure covering an antenna element. A sheet comprising a plurality of unit cells arranged periodically in one direction and the other direction, wherein the unit cells are arranged outside the loop outer conductor and the inner loop outer conductor. Preparing a sheet including a conductor and a plurality of types of unit cells having loop slots formed between the outer loop conductor and the inner conductor, the outer circumferences of the loop slots being different from each other; In the step of preparing a rod, the step of laminating a plurality of coating layers on the circumferential surface of the core rod, and the inner or outer circumferential surface of any one of the plurality of coating layers, the plurality of units The cell is And a step of winding the sheet so as to be arranged along the circumferential direction and the axial direction of the coating layer.
According to the manufacturing method of the cylindrical periodic structure, the cylindrical periodic structure of the antenna described in (1) can be obtained.

(15) In the method for manufacturing a cylindrical periodic structure, in the step of winding the sheet, when the coating layer is stacked on the outer peripheral side of the sheet, the coating layer is stacked on the outermost peripheral side among the plurality of coating layers. Preferably, the method further includes a step of providing the covering layer with a mark that allows the direction of directivity of the antenna element to be visually recognized.
In this case, the direction of directivity of the antenna element can be easily confirmed by the mark.

(16) A method for manufacturing a cylindrical periodic structure according to an embodiment of the present invention includes a plurality of unit cells periodically arranged in the circumferential direction and the axial direction, and manufacturing the cylindrical periodic structure covering an antenna element. A method of preparing a base cylinder, a loop outer conductor, an inner conductor disposed inside the loop outer conductor, and a loop slot formed between the loop outer conductor and the inner conductor A plurality of types of unit cells having different outer peripheral lengths of the loop slots, and printing the plurality of unit cells along the circumferential direction of the outer peripheral surface of the basic cylinder, and outer peripheries of the plurality of unit cells Forming a protective layer for protecting the unit cell on the surface.
According to the manufacturing method of the cylindrical periodic structure, the cylindrical periodic structure of the antenna described in (1) can be obtained.

(17) In the method for manufacturing a cylindrical periodic structure according to (16), it is preferable that the method further includes a step of providing the protective layer with a mark that allows the direction of directivity of the antenna element to be visually recognized. In this case, the direction of directivity of the antenna element can be easily confirmed by the mark.

(18) A cylindrical periodic structure according to an embodiment of the present invention is a cylindrical periodic structure that covers an antenna element, and the antenna element is covered with the cylindrical periodic structure, thereby directing the antenna element. A plurality of unit cells periodically arranged in the circumferential direction and the axial direction are provided so that the characteristics change.
As described in the above (1), the inventor of the present application changes the directivity of the antenna element by the plurality of unit cells periodically arranged along the circumferential direction and the axial direction in the cylindrical periodic structure. And the embodiment of the invention of (15) was completed based on this finding.

  According to the cylindrical periodic structure of the above (18), the antenna element is covered with a simple structure in which the antenna element is covered with the cylindrical periodic structure including a plurality of unit cells periodically arranged in the circumferential direction and the axial direction. The directivity of the element can be adjusted.

(19) In the cylindrical periodic structure, the unit cell is formed between a loop outer conductor, an inner conductor disposed inside the loop outer conductor, and the loop outer conductor and the inner conductor. It is preferable that a plurality of types of unit cells having a loop slot and having different outer peripheral lengths of the loop slot are provided.
In this case, the same effect as the antenna described in (1) is achieved by covering the antenna element with the cylindrical periodic structure.

(20) The cylindrical periodic structure sheet according to the embodiment of the present invention is a cylindrical periodic structure sheet disposed along the circumferential direction as a constituent member of the cylindrical periodic structure covering the antenna element. A plurality of unit cells periodically arranged in one circumferential direction and the other direction, wherein the unit cell includes a loop outer conductor and an inner conductor disposed inside the loop outer conductor. And a plurality of types of unit cells having outer circumferential lengths of the loop slots different from each other.
According to the cylindrical periodic structure sheet, the antenna element is covered with the cylindrical periodic structure provided with the cylindrical periodic structure sheet, so that the same effect as the antenna described in (1) above can be obtained. Play.

(21) In the cylindrical periodic structure sheet, the plurality of unit cells may have an outer peripheral length of the loop slot as they go from the central portion of the one direction to both ends of the cylindrical periodic structure sheet. It is preferable that it is formed so as to be reduced stepwise.
As described in (6) above, the inventor of the present application arranges a plurality of unit cells so that the outer peripheral length of the loop slot becomes smaller as the distance from the direction in which the directivity of the antenna element is directed becomes smaller. The embodiment of the invention according to the above (21) has been completed based on this finding.

  Thereby, the directivity of the antenna element can be adjusted with high accuracy by arranging the central portion of the sheet for the cylindrical periodic structure in a direction in which the directivity of the antenna element is directed. Further, by arranging the cylindrical periodic structure sheet as described above, both end portions in the circumferential direction of the cylindrical periodic structure sheet are not arranged in the direction in which the directivity of the antenna element is directed. Therefore, it is possible to prevent the adjustment accuracy of the directivity of the antenna element from being deteriorated due to the occurrence of a gap between the both end portions.

[Details of the embodiment of the present invention]
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
[overall structure]
FIG. 1 shows an antenna 1 according to a first embodiment of the present invention, where (a) is a plan view and (b) is a side sectional view. The antenna 1 of this embodiment is suitably used as an antenna (transmission / reception antenna) of a base station that performs wireless communication with a mobile terminal such as a mobile phone. The antenna 1 includes an antenna element 2 and a cylindrical periodic structure 3 that covers the antenna element 2. The cylindrical periodic structure 3 of the present embodiment is a cylindrical periodic structure formed in a true cylindrical shape.
The antenna element 2 is disposed at the center of the cylindrical periodic structure 3. The cylindrical periodic structure 3 changes the directivity of the antenna element 2, and also functions as a radome in this embodiment.

The cylindrical periodic structure 3 according to the present embodiment is curved in a cylindrical shape along a basic cylindrical body 3A made of resin such as FRP (Fiber Reinforced Plastics) and a peripheral surface of the basic cylindrical body 3A. And a fixed frequency selective plate 4 (FSS; Frequency Selective Surface). The basic cylinder 3A of the present embodiment is a basic cylindrical body formed in a cylindrical shape. The frequency selection plate 4 (sheet for a cylindrical periodic structure) has a characteristic (FSS characteristic) that allows electromagnetic waves to pass or reflect in a predetermined frequency band (see FIG. 5).
The cylindrical periodic structure 3 may be provided separately from the radome. In this case, the cylindrical periodic structure 3 may be configured only by the frequency selection plate 4.

  FIG. 2 is a development view of the frequency selection plate 4. The frequency selection plate 4 is configured by periodically disposing unit cells 6 which are metal elements on a substrate 5 made of a dielectric (see also FIG. 4). The unit cells 6 of this embodiment are arranged in a matrix in the circumferential direction (left and right direction in FIG. 2) and the axial direction (up and down direction in FIG. 2) of the cylindrical periodic structure 3.

[Unit cell]
FIG. 3 shows the unit cell 6 alone, where (a) is a front view and (b) is a perspective view. The unit cell 6 of this embodiment is formed by etching a metal foil (for example, a copper foil, a brass foil, or an aluminum foil) joined on the substrate 5.
3A, the unit cell 6 has an outer shape formed in a regular square shape, and includes an outer loop conductor 7, an inner conductor 8 disposed inside the outer loop conductor 7, and an outer loop conductor 7. And a loop slot 9 formed between the inner conductor 8 and the inner conductor 8. The loop outer conductors 7 of the unit cells 6 that are adjacent to each other in the circumferential direction and the axial direction are arranged without a gap (see FIG. 2).

The outer loop conductor 7 is a hatched portion in the figure of the metal foil, and its outer shape and inner shape are formed in a regular square shape. The inner conductor 8 is composed of the cross-hatched portion in the figure of the metal foil, and its outer shape is formed in a regular square shape. The loop slot 9 is formed by a white portion in the figure formed between the inner shape of the outer conductor 7 and the outer shape of the inner conductor 8. For this reason, the outer shape and inner shape of the loop slot 9 are also formed in a regular square shape. As shown in FIG. 3B, the hatched portion of the outer loop conductor 7, the cross-hatched portion of the inner conductor 8, and the opening portion of the loop slot 9 formed between these hatched portions are arranged on the same plane. Has been.
The unit cell 6 may be formed by printing a metal paste on the substrate 5, or a metal foil previously formed in each shape of the loop outer conductor 7 and the inner conductor 8 may be attached to the substrate 5. Good.

In FIG. 2, the frequency selection plate 4 has a plurality of (here, two) divided regions 4A and 4B divided in the circumferential direction. The divided regions 4A and 4B of the present embodiment are equally divided by 180 ° in the circumferential direction across the circumferential center line C of the frequency selection plate 4 (see also FIG. 4).
Each divided region 4A, 4B includes a predetermined number of unit cells 6. In each of the divided areas 4A and 4B, the predetermined number of unit cells 6 are formed so that their circumferences are all the same. Further, in the divided areas 4A and 4B, a plurality of types (here, seven types) of unit cells 6 having different outer peripheral lengths, which are the outer peripheral length of the loop slot 9, are arranged in a plurality of rows (here, seven rows) in the circumferential direction. Has been.

In each row, the loop slots 9 in the plurality of unit cells 6 arranged adjacent to each other in the axial direction are formed so that their outer peripheral lengths are the same. Further, the plurality of unit cells 6 arranged in the circumferential direction and the axial direction are arranged such that the distances P between the centers of the adjacent loop slots 9 are the same. Further, the slot widths W (see FIG. 3A) of the loop slots 9 in the plurality of unit cells 6 are formed to be the same.
The plurality of unit cells 6 may be arranged so that the distance P between the centers is different in at least one of the circumferential direction and the axial direction.

The plurality of rows of unit cells 6 in the first divided area 4A are directed from the circumferential one side (right side in FIG. 2) on the center line C side of the first divided area 4A toward the other circumferential side (left side in FIG. 2). The outer circumferential length of the loop slot 9 is formed so as to decrease step by step for each row.
Similarly, the plurality of rows of unit cells 6 in the second divided region 4B are arranged on the center line C side of the second divided region 4B from one circumferential side (left side in FIG. 2) to the other circumferential side (right side in FIG. 2). The outer circumferential length of the loop slot 9 is formed so as to become smaller step by step as it goes to.

As a result, the plurality of rows of unit cells 6 in the frequency selection plate 4 have the outer peripheral lengths of the loop slots 9 as they go from the center portion (center line C) in the circumferential direction of the frequency selection plate 4 to both ends in the circumferential direction. It is formed so as to become smaller in stages.
Here, “decrease in steps” means not only the case where the outer peripheral lengths of the plurality of loop slots 9 arranged in the circumferential direction are reduced by one as in the present embodiment, but also by a plurality of pieces. It also includes the case where it becomes smaller for every random number. However, from the viewpoint that many loop slots 9 having different outer peripheral lengths can be arranged in a limited space, it is preferable to decrease the number by one.

FIG. 4 is a schematic cross-sectional view in a use state in which the frequency selection plate 4 is curved. Note that the loop slot 9 in the drawing is shown in a state of being protruded radially outward from the unit cell 6 for easy understanding of the outer shape (FIGS. 16, 19, 23, 25, which will be described later). The same applies to FIGS. 28, 31, 34, 36, 39 and 42). In addition, although there is no actual delimitation between the unit cells 6 adjacent in the circumferential direction, in the drawing, the demarcation is shown by a solid line for easy understanding (FIGS. 16, 19, 23, and 23 described later). 25, 28, 31, 31, 34, 36, 39 and 42).
4, the loop slot 9 of the unit cell 6 in the divided region 4A and the loop slot 9 of the unit cell 6 in the divided region 4B are the center of the cylindrical frequency selection plate 4 (cylindrical periodic structure 3). Are symmetric with respect to a virtual straight line K passing through the center line C (see also FIG. 2).

  The virtual straight line K is disposed along the direction in which the directivity of the antenna element 2 is directed (the direction of the thick arrow in FIG. 4). As a result, the unit cells 6 in the plurality of columns in each of the divided regions 4A and 4B have directivity of the antenna element 2 from the one side in the circumferential direction (upper side in FIG. 4) to the other side in the circumferential direction (lower side in FIG. 4). It is arranged so that it is gradually away from the direction of facing.

[Relationship between outer circumference of loop slot and FSS characteristics]
In FIG. 3A, when the length of one side of the unit cells 6 is L1, the length L1 of one side of all the unit cells 6 is set to be 0.15λ or less. Here, λ is a free space wavelength (hereinafter the same) in the desired frequency band. In the present embodiment, the desired frequency band is 2.0 GHz, and the length L1 of one side of the unit cell 6 is set to 22.3 mm (= 0.15λ). When the slot width, which is the width of the loop slot 9, is W, the slot width W of all the loop slots 9 is set to 0.9 mm. The length L1 of one side of the unit cell 6 is the same length as the center-to-center distance P (see FIG. 2) between the adjacent loop slots 9.

  When the length of one side of the outer shape of the loop slot 9 is L2, the outer peripheral length (= 4 × L2) of the loop slot 9 is set to be 0.55λ or less. In the present embodiment, the length L2 of the loop slot 9a (see FIG. 2) having the longest outer peripheral length is set to 20.75 mm. Thereby, the outer peripheral length (maximum outer peripheral length) of the loop slot 9a is set to 83.0 mm (= 4 × 20.75 = 0.55λ). Further, the length L2 of the loop slot 9g (see FIG. 2) having the smallest outer peripheral length is set to 8.75 mm. Thereby, the outer peripheral length (minimum outer peripheral length) of the loop slot 9g is set to 35.0 mm (= 4 × 8.75 = 0.23λ).

  Each of the five loop slots 9b to 9f (see FIG. 2) disposed between the loop slot 9a having the maximum outer peripheral length and the loop slot 9g having the minimum outer peripheral length has an order of 75.0 mm, It is set to 67.0 mm, 59.0 mm, 51.0 mm, and 43.0 mm. That is, in the present embodiment, the difference in the outer peripheral length (slot outer peripheral length difference) dS of the loop slots 9 adjacent in the circumferential direction in the seven loop slots 9a to 9g is set to 8.0 mm.

  FIG. 5 shows the FSS characteristics when the frequency selection plates are arranged on a plane when all the unit cells arranged on the frequency selection plate have the loop slot 9a having the maximum outer peripheral length. As shown in FIG. 5, this frequency selection plate has FSS characteristics that allow electromagnetic waves to pass in a 3.5 GHz band that is higher than the 2.0 GHz band of the desired frequency band.

  FIG. 6 shows the FSS characteristics when the frequency selection plates are arranged on a plane when all the unit cells 6 arranged on the frequency selection plate have the loop slot 9g having the minimum outer peripheral length. As shown in FIG. 6, this frequency selection plate has an FSS characteristic that allows electromagnetic waves to pass in a 10.9 GHz band that is higher than the 2.0 GHz band of the desired frequency band.

Therefore, based on the FSS characteristics of FIGS. 5 and 6, the frequency selection plate 4 of the present embodiment has an outer circumference length that becomes an FSS characteristic that allows electromagnetic waves to pass in a frequency band higher than the desired frequency band when arranged on a plane. It can be said that a plurality of unit cells 6 each having a loop slot 9 having a plurality of are provided.
The frequency selection plate 4 has at least one type of unit cell 6 in which a loop slot 9 having an outer peripheral length that does not have an FSS characteristic that allows electromagnetic waves to pass in a frequency band higher than a desired frequency band when formed on a plane is formed. It may be provided.

[Manufacturing method of cylindrical periodic structure]
FIG. 7 is an explanatory view showing a method for manufacturing the cylindrical periodic structure 3. As shown in FIG. 7, the cylindrical periodic structure 3 of the present embodiment can be manufactured by, for example, a filament winding method. The cylindrical periodic structure 3 may be manufactured by a sheet winding method, a hand lay-up method, a spray-up method, or the like other than the filament winding method.
Hereinafter, the manufacturing method of this embodiment will be described with reference to FIG. First, as shown in FIG. 2, a frequency selection plate 4 (sheet) including a plurality of types of unit cells 6 having different outer peripheral lengths of the loop slot 9 is prepared.

Next, as shown in FIG. 7, a plurality of (three in this case) glass rovings 21 in which strands 21 a in which glass filaments (short fibers) are converged are aligned in a predetermined number and wound into a cylindrical shape, A resin impregnation tank 23 storing a thermoplastic resin 22 and a cylindrical mandrel 24 are prepared.
Both ends of the mandrel 24 in the axial direction are supported by the support base 25 so as to be rotatable around the axis X of the mandrel 24. The preparation process of the mandrel 24 may be performed before the preparation process of the frequency selection plate 4.

  Next, after the strands 21a drawn from the plurality of glass rovings 21 are impregnated with the thermoplastic resin 22 in the resin impregnation tank 23, the strands 21a are continuously wound around the rotating mandrel 21 while applying tension. . As a result, as shown in FIG. 8A, a basic cylindrical body 3 </ b> A in which a large number of coating layers 3 </ b> B are laminated is formed on the peripheral surface of the mandrel 24.

  Next, as shown in FIG. 8B, the frequency selection plate 4 is wound in a cylindrical shape along the outer peripheral surface of the covering layer 3B laminated on the outermost peripheral side of the basic cylindrical body 3A. The frequency selection plate 4 is fixed to the outer peripheral surface. Finally, the basic cylindrical body 3A is extracted from the mandrel 21, whereby the cylindrical periodic structure 3 can be obtained.

The step of extracting from the mandrel 21 may be performed before the step of winding the frequency selection plate 4 around the basic cylindrical body 3A. In this case, the frequency selection plate 4 may be wound in a cylindrical shape along the inner peripheral surface of the coating layer 3B arranged on the innermost peripheral side of the basic cylindrical body 3A.
Further, the winding process of the frequency selection plate 4 may be performed before the process of laminating the coating layer 3 </ b> B on the peripheral surface of the mandrel 24. In this case, the frequency selection plate 4 may be wound around the peripheral surface of the mandrel 24 in a cylindrical shape, and then the coating layer 3 </ b> B may be laminated along the outer peripheral surface of the wound frequency selection plate 4. Furthermore, the winding process of the frequency selection plate 4 may be performed during the process of laminating the coating layer 3 </ b> B on the peripheral surface of the mandrel 24.

  When the winding process of the frequency selection plate 4 is performed before or during the process of laminating the coating layer 3B as described above, it is the coating layer 3B that is disposed on the outermost peripheral side of the basic cylindrical body 3A. The selection plate 4 cannot be visually recognized. Therefore, in this case, as will be described later, a step of providing a mark 11 (see FIG. 9C) that can visually recognize the direction of directivity of the antenna element 2 to the covering layer 3B that is laminated on the outermost peripheral side. Further included. Thereby, even if the coating layer 3 </ b> B is laminated on the outer peripheral side of the frequency selection plate 4, the direction in which the directivity of the antenna element 2 is directed can be easily confirmed by the mark 11.

[Other manufacturing method of cylindrical periodic structure]
FIG. 9 is an explanatory view showing another method for manufacturing the cylindrical periodic structure 3. Hereinafter, the manufacturing method will be described with reference to FIG.
First, as shown in FIG. 9A, a basic cylindrical body 3A formed in advance by, for example, extrusion molding is prepared. Next, as shown in FIG. 9B, a plurality of types of unit cells 6 having different outer peripheral lengths of the loop slots 9 are arranged on the outer peripheral surface of the basic cylindrical body 3A by a printing machine (not shown) in the circumferential direction of the outer peripheral surface. Print along. Thereby, the metal conductor layer 3C including the unit cell 6 is formed on the outer peripheral surface of the basic cylindrical body 3A.

  Next, as shown in FIG. 9C, a protective coating is applied to the entire outer peripheral surface of the metal conductor layer 3 </ b> C to form a protective layer 3 </ b> D that protects the unit cell 6. Finally, a mark 11 that can visually recognize the direction in which the directivity of the antenna element 2 is directed is given to the protective layer 3D.

The cylindrical periodic structure 3 can be obtained by the above manufacturing method. Even if the unit cell 6 is covered with the protective layer 3D, the direction of directivity of the antenna element 2 can be easily confirmed by the mark 11.
In FIG. 9C, a black circle is provided as a mark 11 at a position in the circumferential direction that is the direction in which the directivity is directed in the protective layer 3D. However, if the mark 11 can be visually recognized, Any shape may be given. Moreover, in the said manufacturing method, although the unit cell 6 is printed on 3 A of basic cylinders, the frequency selection board (sheet | seat) provided with the unit cell 6 is affixed on the outer peripheral surface or inner peripheral surface of 3 A of basic cylindrical bodies. Also good. In the case of the above manufacturing method, the basic cylindrical body 3A may be formed of other resin materials such as ABS resin (acrylonitrile / butadiene / styrene resin) in addition to FRP.

[Direction of antenna elements]
FIG. 10 shows the directivity of the antenna element of Comparative Example 1, where (a) shows the horizontal plane directivity and (b) shows the vertical plane directivity. The antenna of Comparative Example 1 does not have the cylindrical periodic structure 3, that is, is configured by the antenna element 2 alone. FIGS. 10A and 10B are horizontal plane orientations of the antenna element 2 alone. The directivity (directionality of the XY plane of FIG. 1) and the vertical directivity (directivity of the XZ plane of FIG. 1) are shown.
As shown in FIG. 10A, the horizontal directionality of the antenna element 2 is omnidirectional with a beam width of 360 °, and F / B (Front to Back ratio) is 0 dB. As shown in FIG. 10B, in the vertical plane directivity of the antenna element 2, the beam width in the 90 ° direction (270 ° direction) is 80 °.

  FIG. 11 shows the directivity of the antenna element of Comparative Example 2, where (a) is the horizontal plane directivity and (b) is the vertical plane directivity. The antenna of Comparative Example 2 has a cylindrical periodic structure, and the cylindrical periodic structure has a frequency selection plate having the FSS characteristic shown in FIG. 5 (the outer peripheral length of the loop slot 9 of all unit cells 6). This is different from the present embodiment in that a frequency selection plate having a maximum perimeter length is provided.

When the vertical plane directivity of Comparative Example 1 in FIG. 10B and the vertical plane directivity of Comparative Example 2 in FIG. 11B are compared, the 90 ° direction (the direction in which the directivity of the antenna element 2 is directed) is compared. The beam width was 80 ° in Comparative Example 1, but changed to 33 ° in Comparative Example 2. However, when the horizontal plane directivity of Comparative Example 1 in FIG. 10A and the horizontal plane directivity of Comparative Example 2 in FIG. 11A are compared, the beam widths of both hardly change.
Therefore, when the frequency selection plate having the FSS characteristic shown in FIG. 5 is curved in a cylindrical shape, it is understood that the vertical plane directivity of the antenna element 2 can be adjusted, but the horizontal plane directivity cannot be adjusted.

FIG. 12 shows the directivity of the antenna element 2 of the present embodiment, where (a) is the horizontal plane directivity and (b) is the vertical plane directivity. The cylindrical periodic structure 3 in the antenna 1 of the present embodiment has a frequency selection plate 4 shown in FIG. 2, that is, an outer periphery of the loop slot 9 as it goes from one side to the other side in the circumferential direction in each of the divided regions 4A and 4B. The frequency selection plate 4 is formed so that the length is gradually reduced for each row and the slot outer circumferential length difference dS is set to 8.0.
When the horizontal plane directivity of Comparative Example 1 in FIG. 10A and the horizontal plane directivity of the present embodiment in FIG. 12A are compared, the beam width in the 0 ° direction (the direction in which the directivity of the antenna element 2 is directed). Is 360 ° in the comparative example 1, but is changed to 105 ° in the present embodiment. Further, F / B was 0 dB in the comparative example 1, but is changed to 21.3 dB in the present embodiment.

Further, when comparing the vertical surface directivity of Comparative Example 1 in FIG. 10B and the vertical surface directivity of the present embodiment in FIG. 12B, the beam width in the 90 ° direction is 80 in Comparative Example 1. In this embodiment, the angle is changed to 39 °.
Therefore, it can be seen that when the frequency selection plate 4 of this embodiment is curved in a cylindrical shape, both the horizontal plane directivity and the vertical plane directivity of the antenna element 2 can be adjusted.

[Directivity of the antenna element when the slot outer peripheral length difference of the loop slot is changed]
FIG. 13 shows the directivity of the antenna element 2 when the slot outer peripheral length difference dS of the seven loop slots 9a to 9g having different outer peripheral lengths is changed in the present embodiment. FIGS. 13A and 13B show horizontal plane directivity and vertical plane directivity when the slot outer peripheral length difference dS = 4.0, and FIGS. 13C and 13D show the slot outer peripheral length difference dS = 6. The horizontal plane directivity and the vertical plane directivity when 0 is set.

  When changing the slot outer peripheral length difference dS, the outer peripheral length (83.0 mm) of the loop slot 9a which is the maximum outer peripheral length is a fixed value, and the outer peripheral lengths of the loop slots 9b to 9g are based on the maximum outer peripheral length. Changed the length. Therefore, here, the larger the slot outer peripheral length difference dS is, the smaller the outer peripheral length of the loop slot 9g which is the minimum outer peripheral length is.

  FIG. 14 shows a change in directivity of the antenna element 2 when the slot outer peripheral length difference dS is changed as described above. FIG. 14A shows changes in the beam widths of the horizontal plane directivity and the vertical plane directivity, and FIG. 14B shows changes in F / B of the horizontal plane directivity. Here, the values of the beam width and F / B in Comparative Example 2 (see FIGS. 11A and 11B) were used with the slot outer peripheral length difference dS = 0. Further, assuming that the slot outer peripheral length difference dS = 8.0, the values of the beam width and F / B of this embodiment (see FIGS. 12A and 12B) were used.

As shown in FIG. 14A, it can be seen that the beam width of the horizontal plane directivity gradually narrows as the slot outer peripheral length difference dS increases. Further, it can be seen that the beam width of the vertical plane directivity maintains a beam width (about 40 °) narrower than the beam width (80 °) of the single antenna even when the slot outer peripheral length difference dS increases.
Further, as shown in FIG. 14B, as the slot outer peripheral length difference dS increases, the horizontal plane directivity F / B value gradually increases, and it can be seen that F / B is improved. .

[Directivity of antenna elements when the number of rows of unit cells in the circumferential direction is changed]
FIG. 15 shows the directivity of the antenna element 2 when the number N of columns of the unit cells 6 in the circumferential direction is changed in this embodiment, where (a) is a horizontal plane directivity and (b) is a vertical plane directivity. It is. In FIG. 2 of the present embodiment, since the unit cells 6 are arranged in seven columns in each of the divided regions 4A and 4b, the number N of columns in the present embodiment is 14. On the other hand, FIG. 15 shows the directivity when the number of columns N is 10.
When changing the number of columns N, the number of columns N was changed by changing the diameter of the cylindrical periodic structure 3 without changing the size (peripheral length) of the unit cell 6 alone.

When comparing the horizontal plane directivity of FIG. 15A with the horizontal plane directivity of Comparative Example 1 (antenna element 2 alone) of FIG. 10A, the beam width in the 0 ° direction is from 360 ° of Comparative Example 1. In FIG. 15A, the angle changes to about 120 °. Further, when the vertical surface directivity of the present embodiment in FIG. 15B and the vertical surface directivity of Comparative Example 1 in FIG. 10B are compared, the beam width in the 90 ° direction is 80 of Comparative Example 1. In FIG. 15B, the angle is changed to about 45 °.
Therefore, it can be seen that both the horizontal plane directivity and the vertical plane directivity of the antenna element 2 can be adjusted even when the number of columns N of the unit cells 6 in the circumferential direction is changed.

[Function and effect]
As described above, according to the antenna 1 of the first embodiment, the antenna element 2 is covered with the cylindrical periodic structure 3 having the plurality of types of unit cells 6 whose outer peripheral lengths of the loop slots 9 are different from each other. The directivity of 2 can be adjusted.

  Moreover, the cylindrical periodic structure 3 has a plurality of divided regions 4A and 4B divided in the circumferential direction and the axial direction, and a predetermined number of unit cells 6 in each divided region 4A and 4B are included in the divided regions. Since the outer circumferential length of the loop slot 9 decreases stepwise from one circumferential side to the other circumferential side, the directivity of the antenna element 2 can be adjusted effectively.

  Further, the predetermined number of unit cells 6 in each of the divided regions 4A and 4B are arranged so as to gradually move away from the direction in which the directivity of the antenna element 2 is directed from the one side in the circumferential direction toward the other side in the circumferential direction. Therefore, the directivity of the antenna element 2 can be adjusted more effectively.

The outer peripheral length of the loop slot 9 of the unit cell 6 is set to be 0.55λ or less with respect to the free space wavelength λ of the desired frequency band. That is, the frequency selection plate 4 is a unit cell in which a loop slot 9 having an outer peripheral length having an FSS characteristic that allows electromagnetic waves to pass in a frequency band higher than a desired frequency band (2.0 GHz) when arranged on a plane is formed. 6 is provided, the directivity of the antenna element 2 can be adjusted more effectively.
In addition, in a cross-sectional view orthogonal to the axis Y of the cylindrical periodic structure 3 (see FIG. 4), the loop slots 9 of the plurality of unit cells 6 have a virtual straight line K passing through the center of the cylindrical periodic structure. Since they are formed symmetrically with respect to each other, the cylindrical periodic structure 3 can be further simplified.

Further, since the plurality of unit cells 6 are arranged so that the center distance P (see FIG. 2) between the loop slots 9 of the adjacent unit cells 6 is the same, the cylindrical periodic structure 3 is further provided. A simple configuration can be obtained.
Further, since the slot widths W (see FIG. 3A) of the loop slots 9 in the plurality of unit cells 6 are the same, the cylindrical periodic structure 3 can be further simplified.

The unit cell 6 has a cylindrical periodic structure because the outer peripheral lengths of the loop slots 9 in the plurality of unit cells 6 arranged adjacent to each other along the axial direction of the cylindrical periodic structure 3 are the same. The body 3 can be further simplified.
Further, since the cylindrical periodic structure 3 is a radome, the antenna 1 can have a simple configuration.

Further, the plurality of unit cells 6 are formed such that the outer peripheral length of the loop slot 9 decreases stepwise from the center in the circumferential direction of the frequency selection plate 4 toward both ends. For this reason, the directivity of the antenna element 2 can be adjusted with high accuracy by arranging the central portion of the frequency selection plate 4 in the direction in which the directivity of the antenna element 2 is directed.
Further, by arranging the frequency selection plate 4 as described above, both ends of the frequency selection plate 4 in the circumferential direction are not arranged in the direction in which the directivity of the antenna element 2 is directed. Therefore, it is possible to prevent the directivity adjustment accuracy of the antenna element 2 from being lowered due to the occurrence of a gap between the both end portions.

[Modification of frequency selection plate]

  FIG. 16 is a schematic cross-sectional view showing a modified example of the frequency selection plate 4. In this modification, when the position of the central portion (center line C) in the circumferential direction of the frequency selection plate 4 is 0 °, the direction in which the directivity of the antenna element 2 is directed (the direction indicated by the thick line arrow) is 0 °. Direction and 180 ° direction. Accordingly, the frequency selection plate 4 of this modification has four divided regions 4A, 4B, 4C, 4D divided by 90 ° in the circumferential direction.

In each of the divided areas 4A to 4D, a plurality of rows (here, four rows) of unit cells 6 are arranged in the circumferential direction. In the plurality of rows of unit cells 6 in the first divided region 4A, the outer circumferential length of the loop slot 9 is stepwise for each row from the one circumferential side (upper side in FIG. 16) to the other circumferential side (left side in FIG. 16). It is formed to be smaller.
In the plurality of rows of unit cells 6 in the second divided region 4B, the outer circumferential length of the loop slot 9 is stepwise for each row from the one circumferential side (upper side in FIG. 16) to the other circumferential side (right side in FIG. 16). It is formed to be smaller.

The plurality of rows of unit cells 6 in the third divided region 4C have an outer circumferential length of the loop slot 9 for each row from the one side in the circumferential direction (lower side in FIG. 16) to the other side in the circumferential direction (right side in FIG. 16). It is formed so as to become smaller in stages.
The plurality of rows of unit cells 6 in the fourth divided region 4D are arranged such that the outer peripheral length of the loop slot 9 is increased for each row from the one circumferential side (the lower side in FIG. 16) to the other circumferential side (the left side in FIG. 16). It is formed so as to become smaller in stages.

  Thereby, the plurality of unit cells 6 in the frequency selection plate 4 are formed such that the outer peripheral length of the loop slot 9 gradually decreases from the 0 ° position toward the 90 ° and 270 ° positions, respectively. The outer circumferential length of the loop slot 9 is formed in a stepwise manner as it goes from the 180 ° position to the 90 ° and 270 ° positions.

  The loop slot 9 of the unit cell 6 in the first and fourth divided regions 4A and 4D and the loop slot 9 of the unit cell 6 in the second and third divided regions 4B and 4C are the center (axis line) of the cylindrical periodic structure 3. Y) and an imaginary straight line K passing through the center line C are formed symmetrically. The virtual straight line K is disposed along the 0 ° direction and the 180 ° direction, which are directions in which the directivity of the antenna element 2 is directed.

Thereby, the unit cells 6 in a plurality of columns of the divided regions 4A and 4B are directed to the antenna element 2 from the one side in the circumferential direction (near 0 °) toward the other side in the circumferential direction (near 90 ° or 270 °). It is arranged to gradually move away from the direction of directing sex.
Similarly, the plurality of rows of unit cells 6 in each of the divided regions 4C and 4D are directed to the antenna element 2 from the one side in the circumferential direction (around 180 °) toward the other side in the circumferential direction (near 90 ° or 270 °). It is arranged to gradually move away from the direction of directing sex. The frequency selection plate 4 may be divided into three or more divided areas.
[Modification of unit cell]

  FIG. 17 is an enlarged view showing a modification of the unit cell 6. In the unit cell 6 shown in FIG. 17A, the inner shape of the outer loop conductor 7 and the outer shape of the inner conductor 8 are formed in a perfect circle. Thereby, the loop slot 9 is formed in a perfect circular shape. In the unit cell 6 shown in FIG. 17B, the inner shape of the outer loop conductor 7 and the outer shape of the inner conductor 8 are formed in a regular triangle shape. Thus, the outer shape and inner shape of the loop slot 9 are also formed in a regular triangle shape. In the unit cell 6 shown in FIG. 17C, the inner shape of the outer loop conductor 7 and the outer shape of the inner conductor 8 are formed in an elliptical shape. Thereby, the loop slot 9 is formed in an elliptical ring shape.

FIG. 18 is an enlarged view showing another modification of the unit cell 6. In the unit cell 6, the outer shape and inner shape of the loop outer conductor 7 are formed in a regular hexagonal shape, and the outer shape of the inner conductor 8 is also formed in a regular hexagonal shape. Thereby, the outer shape and inner shape of the loop slot 9 are also formed in a regular hexagonal shape.
The plurality of unit cells 6 are arranged in a honeycomb shape. In the illustrated example, the unit cells 6 are arranged on the lower left side, the unit cells 6 are arranged on the upper center side, and the unit cells 6 are arranged on the lower right side. In order, the outer circumferential length of the loop slot 9 is arranged to be smaller.

In the modification shown in FIG. 18, the center-to-center distance P between the adjacent loop slots 9 can be shortened compared to the case where a plurality of regular square unit cells 6 are arranged as in the present embodiment. This is advantageous in that the types of unit cells 6 having different outer peripheral lengths of the slots 9 can be increased.
The unit cell 6 may be formed in a shape other than the shapes shown in FIGS.

[Second Embodiment]
FIG. 19 is a cross-sectional view of the cylindrical periodic structure 3 of the antenna 1 according to the second embodiment of the present invention. The cylindrical periodic structure 3 of the present embodiment is different from the first embodiment in that the reflector 10 is provided in a part of the circumferential direction. The reflecting plate 10 of the present embodiment is made of a metal conductor, and has a circular arc shape having a predetermined center angle η with the axis Y of the cylindrical periodic structure 3 as the center in the sectional view of FIG.

Accordingly, the frequency selection plate 4 of the present embodiment is curved in an arc shape so as to have a central angle of (360−η) ° which is an angle range in which the reflection plate 10 is not arranged in the cross-sectional view of FIG. doing.
In the present embodiment, the central angle η of the reflecting plate 10 is set to 153 °, and the central angle of the frequency selection plate 4 is set to 207 ° (= 360 ° -153 °). As a result, the frequency selection plate 4 is divided equally by 103.5 ° in the circumferential direction across the center line C in the circumferential direction, and has divided regions 4A and 4B.

The reflector 10 is formed symmetrically with respect to the virtual straight line K at a position opposite to the direction in which the directivity of the antenna element 2 is directed (the direction of the thick arrow in FIG. 19). One end portion in the circumferential direction (left end portion in the figure) of the reflecting plate 10 is disposed close to the other circumferential side side (left end portion in the drawing) of the first divided region 4A, and the other end portion in the circumferential direction of the reflecting plate 10 The (right end portion in the figure) is disposed close to the other circumferential side of the second divided region 4B (right end portion in the figure).
When comparing the cylindrical periodic structure 3 of the present embodiment shown in FIG. 19 and the cylindrical periodic structure 3 of the first embodiment shown in FIG. 4, the reflector 10 of the present embodiment has the frequency of the first embodiment. In the selection plate 4, the unit cells 6 are arranged in place of the unit cells 6 in which the loop slots 9 e to 9 g having outer peripheral lengths smaller than those of the other loop slots 9 a to 9 d are formed. . In addition, although the reflecting plate 10 of this embodiment is arrange | positioned adjacent to the circumferential direction other side of division area 4A, 4B, the circumferential direction other side in division area 4A, 4B of 1st Embodiment (refer FIG. 4). At the position on the side (for example, the position where the loop slots 9e to 9g are formed), it may be arranged so as to cover the outer peripheral side. Further, at the position on the other circumferential side of the first embodiment, the loop slots 9e to 9g are eliminated, that is, the loop outer conductor and the inner conductor are integrated, so that one of the frequency selection plates 4 can be obtained. A part may be used as the dividing plate 10. Moreover, the point which abbreviate | omitted description in 2nd Embodiment is the same as that of 1st Embodiment.

[Direction of antenna elements]
FIG. 20 shows the directivity of the antenna element 2 of the second embodiment, where (a) is the horizontal plane directivity and (b) is the vertical plane directivity. When comparing the horizontal plane directivity of the second embodiment of FIG. 20A and the horizontal plane directivity of the first embodiment of FIG. 12A, the beam width in the 0 ° direction in the second embodiment is the first. It can be seen that the same beam width as that of the embodiment is maintained. It can also be seen that the F / B has a 180 ° gain reduction in the second embodiment.

Further, when the vertical plane directivity of the second embodiment in FIG. 20B and the vertical plane directivity of the first embodiment in FIG. 12B are compared, the beam width in the 90 ° direction in the second embodiment is compared. It can be seen that the same beam width as that in the first embodiment is maintained.
Therefore, by arranging the reflector 10 in place of the unit cell 6 in which the loop slots 9e to 9g having a small outer peripheral length are formed, the beam width of the antenna element 2 with the horizontal plane directivity and the vertical plane directivity is maintained. It can be seen that / B can be improved.

  FIG. 21 shows the directivity of the antenna element 2 when the center angle η of the reflector 10 is changed in the present embodiment. FIGS. 21A and 21B show the horizontal plane directivity and the vertical plane directivity when the central angle η = 51 °, and FIGS. 21C and 21D show the central angle η = 102 °. The horizontal plane directivity and the vertical plane directivity are shown.

  FIG. 22 shows a change in directivity of the antenna element 2 when the center angle η of the reflector 10 is changed as described above. FIG. 22A shows changes in beam widths of horizontal plane directivity and vertical plane directivity, and FIG. 22B shows changes in F / B of horizontal plane directivity. Here, the values of the beam width and F / B of the first embodiment (see FIGS. 12A and 12B) were used with the center angle η = 0 °. Further, assuming that the central angle η = 153 °, the values of the beam width and F / B of the second embodiment (see FIGS. 20A and 20B) were used.

As shown in FIG. 22 (a), it can be seen that even if the central angle η of the reflector 10 changes, the beam width of the horizontal plane directivity changes in the range of 95 ° to 105 ° and is almost constant. . It can also be seen that the beam width of the vertical plane directivity is constant at 38 ° and maintains a beam width narrower than the beam width (80 °) of the single antenna.
Further, as shown in FIG. 22B, as the central angle η of the reflector 10 increases, the horizontal plane directivity F / B value ranges from 21 dB (η = 0) to 25 dB (η = 153 °). It gradually increases and it can be seen that F / B is improved.

  As described above, according to the antenna 1 of the second embodiment, a part of the cylindrical periodic structure 3 in the circumferential direction is the reflecting plate 10, and the reflecting plate 10 is the other circumferential side of the divided areas A and B, that is, the outer peripheral length. F / B in the horizontal plane directivity of the antenna element can be improved by arranging it close to the unit cell 6 in which the loop slot 9 having a small length is formed.

[Third Embodiment]
FIG. 23 is a schematic cross-sectional view of the cylindrical periodic structure 3 of the antenna 1 according to the third embodiment of the present invention. This embodiment is a modification of the first embodiment, and is formed so that the cylindrical periodic structure 3 has a perfect circular approximate polygonal shape in a cross-sectional view orthogonal to the axis Y as shown in FIG. This is different from the first embodiment.
In FIG. 23, the cylindrical periodic structure 3 of the present embodiment is fixed along a basic cylindrical body 3A having an outer shape formed in a regular tetragon in the cross-sectional view, and an outer peripheral surface of the basic cylindrical body 3A. A frequency selection plate 4 is provided.

The frequency selection plate 4 is configured by arranging each row of unit cells 6 in a plurality of rows (here, 14 rows) on each surface of the substrate 5 formed by bending into a regular tetragon in the cross-sectional view. .
In addition, the cross-sectional external shape of the cylindrical periodic structure 3 (basic cylindrical body 3A) may be formed in a polygon other than a regular tetragon. Moreover, the point which abbreviate | omitted description in 3rd Embodiment is the same as that of 1st Embodiment.

  FIG. 24 shows the directivity of the antenna element 2 according to the third embodiment, where (a) shows the horizontal plane directivity and (b) shows the vertical plane directivity. When comparing the horizontal plane directivity of the third embodiment in FIG. 24A and the horizontal plane directivity of Comparative Example 1 in FIG. 10A, the beam width in the 0 ° direction was 360 ° in Comparative Example 1. However, in this embodiment, it is changed to 99.1 °. Further, F / B was 0 dB in the comparative example 1, but is changed to 20.8 dB in the present embodiment.

Further, when comparing the vertical surface directivity of the third embodiment in FIG. 24B and the vertical surface directivity of Comparative Example 1 in FIG. 10B, the beam width in the 90 ° direction is The angle of 80 ° is changed to 38.5 ° in the third embodiment.
Therefore, both the horizontal plane directivity and the vertical plane directivity of the antenna element 2 can be adjusted even when the cross-sectional outer shape of the cylindrical periodic structure 3 is formed to be a perfect circle approximate polygonal shape as in this embodiment. I understand.

[Fourth Embodiment]
FIG. 25 is a schematic cross-sectional view of the cylindrical periodic structure 3 of the antenna 1 according to the fourth embodiment of the present invention. This embodiment is a modification of the first embodiment, and the outer shape of the cylindrical periodic structure 3 in a cross-sectional view shown in FIG. 25 is formed in a non-circular shape having two focal points F1 and F2 that are separated from each other. This is different from the first embodiment.
The basic cylindrical body 3A of the cylindrical periodic structure 3 in the present embodiment includes a pair of semicircular arc portions 3A1, 3A2 formed in a semicircular arc shape centering on the focal points F1, F2 in the cross-sectional view, and these semicircular arcs. It is formed in an oval shape by a pair of linear portions 3A3 and 3A4 that connect the end portions of the portions 3A1 and 3A2. The semicircular arc portions 3A1 and 3A2 are formed to have the same diameter as the basic cylindrical body 3A of the first embodiment.

The focal points F1 and F2 are separated from each other in a direction (left and right direction in the figure) orthogonal to the direction in which the directivity of the antenna element 2 is directed (the direction of the thick line arrow in FIG. 25). They are arranged in line symmetry.
The straight line portion 3A3 is disposed at a position in the direction in which the directivity is directed, and the straight line portion 3A4 is disposed at a position opposite to the direction in which the directivity is directed.

The frequency selection plate 4 of the cylindrical periodic structure 3 is fixed along the outer peripheral surface of the basic cylindrical body 3A, and is formed in a semicircular arc shape along the semicircular arc portion 3A1 of the basic cylindrical body 3A in the cross-sectional view. The first divided area 4A and the second divided area 4B formed in a semicircular arc shape along the semicircular arc portion 3A2 of the basic cylinder 3A.
In the present embodiment, the first divided region 4A is a first curved region formed by a quadratic curve (arc curve) around the focal point F1, and the second divided region 4B is a quadratic curve around the focal point F2. The second curved region is formed by (arc curve). In addition, although the bending area | region of this embodiment is formed by the circular arc curve, you may form by other quadratic curves, such as an elliptic curve, a parabola, or a hyperbola.

The frequency selection plate 4 further includes a first straight region 4E and a second straight region 4F that connect the respective ends of the first bent region 4A and the second bent region 4B.
The first straight region 4E is disposed outside the straight portion 3A3, that is, at a position in the direction in which directivity is directed. The second straight region 4F is arranged outside the straight portion 3A4, that is, at a position opposite to the direction in which directivity is directed.

FIG. 26 is a side view of the frequency selection plate 4 of FIG. 25, (a) is a side view seen from the 0 ° direction, and (a) is a side view seen from the 180 ° direction.
25 and 26, each bending area 4A, 4B includes a predetermined number of unit cells 6. Specifically, in each of the bent areas 4A and 4B, a plurality of types (seven types here) of unit cells 6 having different outer peripheral lengths of the loop slot 9 are arranged in the circumferential direction (seven rows here). Yes.

In the plurality of rows of unit cells 6 in the first bent region 4A, the outer peripheral length of the loop slot 9 increases from one circumferential direction on the first linear region 4E side to the other circumferential side on the second linear region 4F side. Each column is formed so as to become smaller step by step.
Similarly, the plurality of rows of unit cells 6 in the second bent region 4B are arranged in the loop slot 9 from the one circumferential direction on the first straight region 4E side toward the other circumferential direction on the second straight region 4F side. The outer peripheral length is formed so as to decrease stepwise for each row.

The first straight line region 4E includes a predetermined number of unit cells 6 in only one column. These unit cells 6 have loop slots 9h having the same outer peripheral length as the loop slot 9a having the largest outer peripheral length in each of the bending regions 4A and 4B.
Similarly to the first straight line region 4E, the second straight line region 4F includes a predetermined number of unit cells 6 in only one column. These unit cells 6 have loop slots 9i having the same outer peripheral length as the loop slot 9g having the smallest outer peripheral length in each of the bending regions 4A and 4B.

  The loop slot 9h in the unit cell 6 of the first straight region 4E may have an outer peripheral length that is greater than the outer peripheral length of the loop slot 9a. Similarly, the loop slot 9i in the unit cell 6 in the second straight region 4F may have an outer peripheral length smaller than the outer peripheral length of the loop slot 9g. Moreover, the point which abbreviate | omitted description in 4th Embodiment is the same as that of 1st Embodiment.

  FIG. 27 shows the directivity of the antenna element 2 of the fourth embodiment, where (a) shows the horizontal plane directivity and (b) shows the vertical plane directivity. When comparing the horizontal plane directivity of the fourth embodiment of FIG. 27A and the horizontal plane directivity of the first embodiment of FIG. 12A, the beam width in the 0 ° direction is 105 ° in the first embodiment. In contrast, in the fourth embodiment, the angle is narrowed to 78.5 °. Moreover, F / B of 4th Embodiment is 20.6 dB, and it turns out that it is comparable as F / B (21.3 dB) of 1st Embodiment.

Further, when the vertical plane directivity of the fourth embodiment in FIG. 27B and the vertical plane directivity of the first embodiment in FIG. 12B are compared, the beam width in the 90 ° direction in the fourth embodiment is compared. Is 31.5 °, which is comparable to the beam width (39 °) of the first embodiment.
Therefore, as in the present embodiment, the cross-sectional outer shape of the cylindrical periodic structure 3 is a non-circular shape (oval shape), and the loop slot 9 increases as it goes from one circumferential side to the other circumferential side of each bending region 4A, 4B. The horizontal length of the antenna element 2 is reduced stepwise so that the horizontal plane directivity F / B and the vertical plane directivity beam width of the antenna element 2 are maintained at the same level as in the first embodiment. You can see that the width can be narrowed.

  As described above, according to the antenna 1 of the fourth embodiment, the cylindrical periodic structure 3 has the two focal points F1 and F2 that are separated from each other in a cross-sectional view orthogonal to the axis Y (see FIG. 25). The loop slot 9 is formed so as to have a perfect circular shape, and the outer circumferential length of the loop slot 9 is gradually reduced from the circumferential direction one side to the other circumferential side of the bent regions 4A and 4B formed around the focal points F1 and F2. By forming, the beam width of the horizontal directivity of the antenna element 2 can be narrowed.

[Fifth Embodiment]
FIG. 28 is a schematic cross-sectional view of the cylindrical periodic structure 3 of the antenna 1 according to the fifth embodiment of the present invention. FIG. 29 is a side view of the frequency selection plate 4 in the cylindrical periodic structure 3 of FIG. 28 viewed from the 0 ° direction.
28 and 29, the present embodiment is a modification of the fourth embodiment, and differs from the fourth embodiment in that the unit cell 6 is not disposed in the first linear region 4E of the frequency selection plate 4.

  The first straight region 4E of the frequency selection plate 4 in the present embodiment is a non-arranged region in which the unit cells 6 are not disposed on the substrate 5. As a result, the circumferential end of the non-arranged region 4E (the left end in FIG. 28) is connected to the circumferential end on the loop slot 9a side having the maximum outer peripheral length of the first bent region 4A. An end (the right end in FIG. 28) is connected to a peripheral end on the loop slot 9a side having the maximum outer peripheral length of the second bent region 4B. In addition, the point which abbreviate | omitted description in 5th Embodiment is the same as that of 4th Embodiment.

  FIG. 30 shows the directivity of the antenna element 2 of the fifth embodiment, where (a) shows the horizontal plane directivity and (b) shows the vertical plane directivity. Comparing the horizontal plane directivity of the fifth embodiment of FIG. 30 (a) with the horizontal plane directivity of the first embodiment of FIG. 12 (a), the beam width in the 0 ° direction is 105 ° in the first embodiment. In contrast, in the fifth embodiment, the angle is narrowed to 79.1 °. Moreover, F / B of 5th Embodiment is 21.6 dB, and it turns out that it is comparable as F / B (21.3 dB) of 1st Embodiment.

Furthermore, when the vertical plane directivity of the fifth embodiment in FIG. 30B and the vertical plane directivity of the first embodiment in FIG. 12B are compared, the beam width in the 90 ° direction in the fifth embodiment is compared. Is 30 °, which is about the same as the beam width (39 °) of the first embodiment.
Therefore, as in the present embodiment, even if the first straight region 4E in the cylindrical periodic structure 3 is a non-arranged region in which the unit cells 6 are not disposed, the horizontal plane directivity F / B and the vertical of the antenna element 2 are used. It can be seen that the horizontal-directional beamwidth can be narrowed while maintaining the surface-directive beamwidth at the same level as in the first embodiment.

  As described above, according to the antenna 1 of the fifth embodiment, a part of the cylindrical periodic structure 3 in the circumferential direction is the non-arranged region 4E in which the unit cells 6 are not disposed, and both peripheral ends of the non-arranged region 4E. In addition, the beam width of the horizontal directivity of the antenna element 2 can be narrowed by connecting the peripheral ends on the loop slot 9 side having the maximum outer peripheral length of each of the bent regions 4A and 4B.

[Sixth Embodiment]
FIG. 31 is a schematic cross-sectional view of the cylindrical periodic structure 3 of the antenna 1 according to the sixth embodiment of the present invention. 32 is a side view of the frequency selection plate 4 in the cylindrical periodic structure 3 of FIG. 31, (a) is a side view seen from the 0 ° direction, and (a) is seen from the 180 ° direction. FIG.
31 and FIG. 32, this embodiment is a modification of the fourth embodiment, and is the point that the cross-sectional outer shape of the cylindrical periodic structure 3 is formed in a flat oval shape as compared with the fourth embodiment. Different from the fourth embodiment.

Specifically, the bending regions 4A and 4B of the frequency selection plate 4 in the present embodiment are formed to have a smaller diameter than that of the fourth embodiment, and the linear regions 4E and 4F are more than those of the fourth embodiment. It is formed long.
Further, in the frequency selection plate 4 of the present embodiment, six rows of unit cells 6 are arranged in each of the bending regions 4A and 4B, and two rows of unit cells 6 are arranged in each of the straight regions 4E and 4F.

  The six rows of unit cells 6 in each of the bending regions 4A and 4B have an outer circumferential length of the loop slot 9 from the one circumferential direction on the first linear region 4E side toward the other circumferential direction on the second linear region 4F side. Is formed so as to become smaller step by step for each column. In the present embodiment, the slot outer peripheral length difference dS of the adjacent loop slots 9 in the loop slots 9a to 9f formed in each of the bending regions 4A and 4B is set to 9.6 mm.

The two rows of unit cells 6 in the first straight region 4E have loop slots 9h having the same outer peripheral length. These loop slots 9h have the same outer peripheral length as the loop slot 9a having the largest outer peripheral length in each of the bent regions 4A and 4B.
The two rows of unit cells 6 in the second straight region 4F have loop slots 9i having the same outer peripheral length. These loop slots 9i have the same outer peripheral length as the loop slot 9f having the smallest outer peripheral length in each of the bent regions 4A and 4B.

  The loop slot 9h in the unit cell 6 of the first straight region 4E may have an outer peripheral length that is greater than the outer peripheral length of the loop slot 9a. Similarly, the loop slot 9i in the unit cell 6 in the second straight region 4F may have an outer peripheral length smaller than the outer peripheral length of the loop slot 9f. In addition, each linear region 4E. 4F may include three or more rows of unit cells 6, and in this case, each linear region 4E. The unit cells 6 in a plurality of rows of 4F are connected to the straight line region 4E. The outer peripheral length of the loop slot 9 may be formed so as to decrease stepwise for each row from the central portion in the longitudinal direction of 4F toward both ends. Moreover, the point which abbreviate | omitted description in 6th Embodiment is the same as that of 4th Embodiment.

  FIG. 33 shows the directivity of the antenna element 2 of the sixth embodiment, where (a) is the horizontal plane directivity and (b) is the vertical plane directivity. When comparing the horizontal plane directivity of the sixth embodiment in FIG. 33 (a) with the horizontal plane directivity of the first embodiment in FIG. 12 (a), the beam width in the 0 ° direction is 105 ° in the first embodiment. In contrast, in the sixth embodiment, the angle is narrowed to 71.8 °. Moreover, F / B of 6th Embodiment is 21.6 dB, and it turns out that it is comparable as F / B (22.4 dB) of 1st Embodiment.

Further, when the vertical plane directivity of the sixth embodiment in FIG. 33B and the vertical plane directivity of the first embodiment in FIG. 12B are compared, the beam width in the 90 ° direction in the sixth embodiment is compared. Is 31.5 °, which is comparable to the beam width (39 °) of the first embodiment.
Therefore, as in the present embodiment, the cross-sectional outer shape of the cylindrical periodic structure 3 is a flat oval shape, the number of columns of the unit cells 6 arranged in each of the bent regions 4A and 4B is reduced, and each linear region 4E, Even when the number of columns of the unit cells 6 arranged in 4F is increased, the horizontal plane directivity F / B and the vertical plane directivity beam width of the antenna element 2 are maintained at the same level as in the first embodiment. It can be seen that the beam width can be narrowed.

[Seventh Embodiment]
FIG. 34 is a schematic cross-sectional view of the cylindrical periodic structure 3 of the antenna 1 according to the seventh embodiment of the present invention. This embodiment is a modification of the fourth embodiment, and differs from the fourth embodiment in that a plurality of antenna elements 2 are provided.
The antenna 1 in the present embodiment includes two antenna elements 2 in a cylindrical periodic structure 3. These two antenna elements 2 are arranged at non-circular (oval-shaped) focal points F1 and F2 that are cross-sectional outlines of the cylindrical periodic structure 3, respectively. Since the other configuration of the present embodiment is the same as that of the fourth embodiment, description thereof is omitted.

  FIG. 35 shows the directivity of the antenna element 2 of the seventh embodiment, where (a) shows the horizontal plane directivity and (b) shows the vertical plane directivity. Comparing the horizontal plane directivity of the seventh embodiment in FIG. 35 (a) with the horizontal plane directivity of the first embodiment in FIG. 12 (a), the beam width in the 0 ° direction is 105 ° in the first embodiment. In contrast, in the seventh embodiment, the angle is narrowed to 77.1 °. Moreover, F / B of 7th Embodiment is 21.3 dB, and it turns out that it is comparable as F / B (22.4 dB) of 1st Embodiment.

Furthermore, comparing the vertical plane directivity of the seventh embodiment in FIG. 35B and the vertical plane directivity of the first embodiment in FIG. 12B, the beam width in the 90 ° direction in the seventh embodiment. Is 31.7 °, which is comparable to the beam width (39 °) of the first embodiment.
Therefore, even when the cross-sectional outer shape of the cylindrical periodic structure 3 is a non-circular shape (oval shape) and the two antenna elements 2 are arranged inside the cylindrical outer structure 3 as in this embodiment, the horizontal plane of the antenna element 2 It can be seen that the beam width of the horizontal plane directivity can be narrowed while maintaining the beam width of the directivity F / B and the vertical plane directivity at the same level as in the first embodiment.

[Eighth Embodiment]
FIG. 36 is a schematic cross-sectional view of the cylindrical periodic structure 3 of the antenna 1 according to the eighth embodiment of the present invention. 37 is a side view of the frequency selection plate 4 in the cylindrical periodic structure 3 of FIG. 36, (a) is a side view seen from the 0 ° direction, and (a) is seen from the 180 ° direction. FIG.
36 and 37, this embodiment is a modification of the fourth embodiment, and the direction in which the directivity of the antenna element 2 is directed (the direction indicated by the thick line arrow) is both the 0 ° direction and the 180 ° direction. This is different from the fourth embodiment in that it is oriented.

The frequency selection plate 4 of the present embodiment includes four first to fourth divided regions 4A to 4D and two first to second straight regions 4E and 4F. The first divided region 4A is formed in an arc shape from the peripheral end position on the 270 ° side to the peripheral end position on the 0 ° side in the semicircular arc portion 3A1 of the basic cylinder 3A. The first divided area 4A is a first bent area formed by a quadratic curve (arc curve) around the focal point F1.
The second divided region 4B is formed in an arc shape from the circumferential end position on the 0 ° side to the circumferential end position on the 90 ° side in the semicircular arc portion 3A2 of the basic cylinder 3A. The second divided region 4B is a second bent region formed by a quadratic curve (arc curve) around the focal point F2.

The third divided region 4C is formed in an arc shape from the circumferential end position on the 90 ° side to the circumferential end position on the 180 ° side in the semicircular arc portion 3A2 of the basic cylinder 3A. The third divided region 4C is a third curved region formed by a quadratic curve (arc curve) around the focal point F2.
The fourth divided region 4D is formed in an arc shape from the circumferential end position on the 180 ° side to the circumferential end position on the 270 ° side in the semicircular arc portion 3A1 of the basic cylinder 3A. The fourth divided region 4D is a fourth curved region formed by a quadratic curve (arc curve) around the focal point F1.

The first straight region 4E connects the peripheral edges on the 0 ° side of the first bent region 4A and the second bent region 4B, and the second straight region 4F includes the third bent region 4C and the fourth bent region 4D. The peripheral ends on the 180 ° side are connected to each other.
In this embodiment, the 90 ° side peripheral ends of the second bent region 4B and the third bent region 4C and the 270 ° side peripheral ends of the fourth bent region 4D and the first bent region 4A are Are also directly connected, but may be connected via a straight line area configured similarly to the straight line areas 4E and 4F. In this case, the cylindrical periodic structure 3 is formed as a non-circular shape having four focal points that are the center points of the four bending regions 4A to 4D. Moreover, what is necessary is just to arrange | position the loop slot 9i mentioned later in the linear area | region which connects the said 90 degree side peripheral ends, and the linear area | region which connects the said 270 degree side peripheral ends.

  Each bending area 4A to 4D includes a predetermined number of unit cells 6. Specifically, in each of the bending regions 4A to 4D, a plurality of types (here, three types) of unit cells 6 having different outer peripheral lengths of the loop slot 9 are arranged in a plurality of rows (here, three rows) in the circumferential direction. Yes.

In the plurality of rows of unit cells 6 in the first bent region 4A, the outer circumferential length of the loop slot 9 is stepwise for each row from the circumferential one side that is 0 ° toward the other circumferential side that is 270 °. It is formed to be smaller.
In the plurality of rows of unit cells 6 in the second bent region 4A, the outer circumferential length of the loop slot 9 is gradually increased for each row from the one circumferential side that is 0 ° toward the other circumferential side that is 90 °. It is formed to be smaller.

The plurality of rows of unit cells 6 in the third bend region 4C have an outer circumferential length of the loop slot 9 stepwise for each row from the one side in the circumferential direction which is 180 ° toward the other side in the circumferential direction which is 90 °. It is formed to be smaller.
The plurality of rows of unit cells 6 in the fourth bent region 4D have the outer circumferential length of the loop slot 9 stepwise for each row from the one side in the circumferential direction that is 180 ° toward the other side in the circumferential direction that is 270 °. It is formed to be smaller. In the present embodiment, the slot outer peripheral length difference dS of the adjacent loop slots 9 in the loop slots 9a to 9c formed in each of the bent regions 4A to 4D is set to 20.0 mm.

One row of unit cells 6 is arranged across the two bent regions 4B and 4C at the connecting portion between the peripheral ends on the 90 ° side of the second bent region 4B and the third bent region 4C. Similarly, a row of unit cells 6 is disposed across the two bent regions 4D and 4A at the connecting portion between the peripheral ends on the 270 ° side of the fourth bent region 4D and the first bent region 4A.
The unit cells 6 arranged at these connecting portions have loop slots 9i having the same outer peripheral length as the loop slot 9c having the smallest outer peripheral length in the adjacent bent regions 4B and 4C (4D, 4A). The loop slot 9i may have an outer peripheral length that is smaller than the outer peripheral length of the loop slot 9c.

The first straight line region 4E includes a predetermined number of unit cells 6 in only one column. These unit cells 6 have loop slots 9h having the same outer peripheral length as the loop slot 9a having the longest outer peripheral length in the adjacent bent regions 4A and 4B.
Similarly to the first straight line region 4E, the second straight line region 4F includes a predetermined number of unit cells 6 in only one column. These unit cells 6 have loop slots 9h having the same outer peripheral length as the loop slot 9a having the largest outer peripheral length in the adjacent bent regions 4C and 4D.

  Note that at least one loop slot 9h of the unit cell 6 in the straight line region 4E and the unit cell 6 in the straight line region 4F may have a larger outer peripheral length than the outer peripheral length of the loop slot 9a. In the present embodiment, the center of the unit cell 6 is arranged in the 0 ° direction of the linear region 4E, but the boundary between the adjacent unit cells 6 may be arranged in the 0 ° direction. Moreover, the point which abbreviate | omitted description in 8th Embodiment is the same as that of 4th Embodiment.

  FIG. 38 shows the directivity of the antenna element 2 according to the eighth embodiment, where (a) shows the horizontal plane directivity and (b) shows the vertical plane directivity. Comparing the horizontal plane directivity of the eighth embodiment of FIG. 38A and the horizontal plane directivity of the first embodiment of FIG. 12A, the beam width in the 0 ° direction is 105 ° in the first embodiment. In contrast, in the eighth embodiment, the angle is narrowed to 61.9 °. Further, comparing the vertical plane directivity of the eighth embodiment in FIG. 38B and the vertical plane directivity of the first embodiment in FIG. 12B, the beam width in the 90 ° direction in the eighth embodiment. Is 34.9 °, which is comparable to the beam width (39 °) of the first embodiment.

Therefore, as in the present embodiment, the cross-sectional outer shape of the cylindrical periodic structure 3 is a non-circular shape (oval shape), and the direction in which the directivity of the antenna element 2 is directed is bidirectional between 0 ° and 180 °. Even in this case, it can be seen that the beam width of the horizontal plane directivity can be narrowed while maintaining the beam width of the vertical plane directivity of the antenna element 2 at the same level as in the first embodiment.
The antenna 1 of this embodiment is particularly effective when adjusting the directivity in one direction in the horizontal direction and in the opposite direction in an underground shopping mall, for example.

  In the present embodiment, the direction in which the directivity of the antenna element 2 is directed is the 0 ° direction and the 180 ° direction, but may be the 90 ° direction and the 270 ° direction. In this case, if the frequency selection plate 4 is formed with loop slots 9 having minimum outer peripheral lengths on the 0 ° side and 180 ° side, and loop slots 9 having maximum outer peripheral lengths on the 90 ° side and 270 ° side. Good.

[Ninth Embodiment]
FIG. 39 is a schematic cross-sectional view of the cylindrical periodic structure 3 of the antenna 1 according to the ninth embodiment of the present invention. This embodiment is a modification of the fourth embodiment, and differs from the fourth embodiment in that the cross-sectional outer shape of the cylindrical periodic structure 3 is formed in an elliptical shape.
Specifically, the basic cylindrical body 3A of the cylindrical periodic structure 3 in the present embodiment is directed to the direction in which the directivity of the antenna element 2 is directed (the direction of the thick arrow in the drawing) in the cross-sectional view shown in FIG. It is formed in an elliptical shape having two focal points F1 and F2 that are separated from each other in an orthogonal direction (left and right direction in the figure).

The frequency selection plate 4 of the cylindrical periodic structure 3 has two first and second divided regions 4A and 4B that are equally divided by 180 ° in the circumferential direction across the virtual straight line K (center line C). doing.
In the present embodiment, the first divided region 4A is a first curved region formed by a quadratic curve (elliptical curve) around the focal point F1, and the second divided region 4B is a quadratic curve around the focal point F2. The second bent region is formed by (elliptical curve).

40 is a side view of the frequency selection plate 4 in the cylindrical periodic structure 3 of FIG. 39, (a) is a side view seen from the 0 ° direction, and (a) is a side view seen from the 180 ° direction. FIG.
39 and 40, a predetermined number of unit cells 6 are included in each of the bending regions 4A and 4B. Specifically, in each of the bent areas 4A and 4B, a plurality of types (seven types here) of unit cells 6 having different outer peripheral lengths of the loop slot 9 are arranged in the circumferential direction (seven rows here). Yes.

In the plurality of rows of unit cells 6 in the first bent region 4A, the outer circumferential length of the loop slot 9 is stepwise for each row from the one circumferential side that is 0 ° toward the other circumferential side that is 180 °. It is formed to be smaller.
Similarly, the plurality of rows of unit cells 6 in the second bent region 4B have the outer circumferential length of the loop slot 9 for each row from the circumferential direction one side which is 0 ° to the circumferential direction other side which is 180 °. It is formed so as to become smaller in stages.

One row of unit cells 6 is disposed across the two bent regions 4A and 4B at the connecting portion between the peripheral edges on the 0 ° side of the first bent region 4A and the second bent region 4B. These unit cells 6 have loop slots 9h having the same outer peripheral length as the loop slot 9a having the longest outer peripheral length in the adjacent bent regions 4A and 4B.
In addition, the loop slot 9h in the unit cell 6 arrange | positioned at the said connection part may have outer peripheral length larger than the outer peripheral length of the loop slot 9a. Moreover, although the center of the unit cell 6 is arrange | positioned in the 0 degree direction in the said connection part, the boundary of the adjacent unit cell 6 may be arrange | positioned in the said 0 degree direction.

One row of unit cells 6 is arranged across the two bent regions 4A and 4B at the connecting portion between the peripheral ends on the 180 ° side of the first bent region 4A and the second bent region 4B. These unit cells 6 have loop slots 9i having the same outer peripheral length as the loop slot 9g having the smallest outer peripheral length in the adjacent bent regions 4A and 4B.
In addition, the loop slot 9i in the unit cell 6 arrange | positioned at the said connection part may have outer peripheral length smaller than the outer peripheral length of the loop slot 9g. Moreover, the point which abbreviate | omitted description in 9th Embodiment is the same as that of 4th Embodiment.

  FIG. 41 shows the directivity of the antenna element 2 of the ninth embodiment, where (a) shows the horizontal plane directivity and (b) shows the vertical plane directivity. When comparing the horizontal plane directivity of the ninth embodiment in FIG. 41A and the horizontal plane directivity of the first embodiment in FIG. 12A, the beam width in the 0 ° direction is 105 ° in the first embodiment. In contrast, in the ninth embodiment, the angle is narrowed to 74.9 °. Moreover, F / B of 9th Embodiment is 27.4 dB, and it turns out that it is comparable as F / B (22.4 dB) of 1st Embodiment.

Further, comparing the vertical surface directivity of the ninth embodiment in FIG. 41B and the vertical surface directivity of the first embodiment in FIG. 12B, the beam width in the 90 ° direction in the ninth embodiment. Is 29.1 °, which is comparable to the beam width (39 °) of the first embodiment.
Accordingly, even when the cross-sectional outer shape of the cylindrical periodic structure 3 is elliptical as in the present embodiment, the horizontal plane directivity F / B and the vertical plane directivity beam width of the antenna element 2 are set to the first embodiment. It can be seen that the beam width of the horizontal plane directivity can be narrowed while maintaining the same level.

  In the present embodiment, the cross-sectional outer shape of the cylindrical periodic structure 3 is formed in an elliptical shape, but may be an elliptical approximate polygonal shape, or the elliptical shape or the approximated polygonal shape may be an imaginary straight line K ( 39), and the cut peripheral ends may be connected by a linear region as in the fourth embodiment.

[Tenth embodiment]
FIG. 42 is a schematic cross-sectional view of the cylindrical periodic structure 3 of the antenna 1 according to the tenth embodiment of the present invention. 43 is a side view of the frequency selection plate 4 in the cylindrical periodic structure 3 of FIG. 42, (a) is a side view seen from the 0 ° direction, and (a) is seen from the 180 ° direction. FIG.
42 and 43, the present embodiment is a modification of the fourth embodiment, and is different from the fourth embodiment in that the cross-sectional outer shape of the cylindrical periodic structure 3 is formed in an approximate polygonal shape of an oval shape. Different.

  Specifically, the outer shapes of the semicircular arc portions 3A1 and 3A2 of the basic cylindrical body 3A in the cylindrical periodic structure 3 of the present embodiment are semicircular arcs centered on the respective focal points F1 and F2 in the sectional view shown in FIG. It is formed by a straight line group that approximates the shape (hereinafter also referred to as an approximate straight line group). And each straight line part which comprises this approximate straight line group is all formed in the same length. That is, the semicircular arc portions 3A1 and 3A2 of the present embodiment are cut into two by cutting the basic cylindrical body 3A having an outer shape formed in the regular 14-gon shape of the third embodiment (FIG. 23) on the virtual straight line K. It has the same shape as the divided one.

The frequency selection plate 4 of the cylindrical periodic structure 3 is fixed along the outer peripheral surface of the basic cylindrical body 3A, and is formed along the approximate straight line group of the semicircular arc portion 3A1 of the basic cylindrical body 3A in the cross-sectional view. The first divided region 4A and the second divided region 4B formed along the approximate straight line group of the semicircular arc portion 3A2 of the basic cylindrical body 3A.
In the present embodiment, the first divided region 4A is a first bent region formed by a group of straight lines that approximate a quadratic curve (arc curve) around the focal point F1, and the second divided region 4B is the focal point F2. A second curved region formed by a group of straight lines approximating a quadratic curve (arc curve) is formed around.

  In each of the bent areas 4A and 4B, one row of unit cells 6 is arranged in each portion corresponding to each straight line portion of the approximate straight line group, and a total of seven rows are arranged in the circumferential direction. In addition, since the other structure of this embodiment is the same as that of 4th Embodiment, description is abbreviate | omitted.

  FIG. 44 shows the directivity of the antenna element 2 according to the tenth embodiment, where (a) shows the horizontal plane directivity and (b) shows the vertical plane directivity. Comparing the horizontal plane directivity of the tenth embodiment of FIG. 44 (a) with the horizontal plane directivity of the first embodiment of FIG. 12 (a), the beam width in the 0 ° direction is 105 ° in the first embodiment. In contrast, in the tenth embodiment, the angle is narrowed to 74.6 °. Moreover, F / B of 10th Embodiment is 23.9 dB, and it turns out that it is comparable as F / B (22.4 dB) of 1st Embodiment.

Further, comparing the vertical surface directivity of the tenth embodiment of FIG. 44B and the vertical surface directivity of the first embodiment of FIG. 12B, the beam width in the 90 ° direction in the tenth embodiment. Is 30.2 °, which is comparable to the beam width (39 °) of the first embodiment.
Therefore, even when the cross-sectional outer shape of the cylindrical periodic structure 3 is an oval approximate polygonal shape as in the present embodiment, the horizontal plane directivity F / B and the vertical plane directivity beam width of the antenna element 2 are It can be seen that the beam width of the horizontal plane directivity can be narrowed while maintaining the same level as in the first embodiment.

  In the fourth to tenth embodiments, the cross-sectional outer shape of the cylindrical periodic structure 3 is a non-circular shape having two focal points, an oval shape, an elliptical shape, and an approximate polygonal shape thereof. Although described, it may be formed in other shapes such as a ridge shape or a shape made up of a group of straight lines similar to this. That is, if there is a curved region formed by a quadratic curve or an approximate straight line group around each of at least two focal points, the shape of the portion connecting these two curved regions is a linear shape or a quadratic curve. What is necessary is just to form in arbitrary shapes, such as a shape. Moreover, the cross-sectional outer shape of the cylindrical periodic structure 3 may be formed in a non-circular shape having three or more focal points.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 Antenna 2 Antenna Element 3 Cylindrical Periodic Structure (Radome)
3A Basic cylindrical body 3A1, 3A2 Semicircular arc part 3A3, 3A4 Straight line part 3B Cover layer 3C Metal conductor layer 3D Protective layer 4 Frequency selection plate (sheet, sheet for cylindrical periodic structure)
4A 1st division area (1st curve area)
4B Second divided area (second bent area)
4C 3rd division area (3rd bend area)
4D 4th division area (4th curve area)
4E 1st straight line area (non-arrangement area)
4F 2nd linear region 5 Substrate 6 Unit cell 7 Loop outer conductor 8 Inner conductor 9 Loop slot 9a to 9i Loop slot 10 Reflector 11 Mark 21 Glass roving 21a Strand 22 Thermoplastic resin 23 Resin impregnation tank 24 Mandrel 25 Support base C Center Line dS Slot outer peripheral length difference F1 Focus F2 Focus K Virtual straight line P Center-to-center distance W Slot width X Mandrel axis Y Axis of cylindrical periodic structure

Claims (20)

An antenna element;
A plurality of unit cells periodically arranged in the circumferential direction and the axial direction, and a cylindrical periodic structure covering the antenna element,
The unit cell includes a loop outer conductor, an inner conductor disposed inside the loop outer conductor, and a loop slot formed between the loop outer conductor and the inner conductor,
The cylindrical periodic structure includes an antenna including a plurality of types of unit cells having different outer peripheral lengths of the loop slots.   The antenna according to claim 1, wherein the cylindrical periodic structure is formed in a true cylindrical shape. The cylindrical periodic structure has a plurality of divided regions divided in the circumferential direction, and each divided region includes a predetermined number of unit cells,
The predetermined number of unit cells in each divided region is formed such that the outer peripheral length of the loop slot decreases stepwise from one circumferential direction to the other circumferential side of the divided region. The antenna of Claim 1 or Claim 2. The cylindrical periodic structure is formed so that an outer shape in a cross-sectional view orthogonal to the axis thereof is a non-circular shape having at least two focal points separated from each other, and two around each of the two focal points. A curved region formed by a group of straight lines approximating a quadratic curve or a quadratic curve thereof,
Each bend region includes a predetermined number of the unit cells;
The predetermined number of unit cells in each of the bent regions are formed such that the outer peripheral length of the loop slot decreases stepwise from one circumferential direction side to the other circumferential side of the bent region. Item 10. The antenna according to Item 1. The cylindrical periodic structure further has a non-arrangement region in which the unit cells are not arranged in a part of the circumferential direction thereof,
One end in the circumferential direction of the non-arranged region is connected to one side in the circumferential direction of the one bent region,
The antenna according to claim 4, wherein the other circumferential side end of the non-arranged region is connected to the other circumferential side of the curved region.   The said predetermined number of unit cells are arrange | positioned so that it may gradually distance from the direction which directs the directivity of the said antenna element as it goes to the said circumferential direction other side from the said circumferential direction one side. The antenna as described in any one of.   The antenna according to any one of claims 1 to 6, wherein an outer peripheral length of the loop slot is 0.55λ or less (λ is a free space wavelength in a desired frequency band).   In a cross-sectional view orthogonal to the axis of the cylindrical periodic structure, the loop slots of the plurality of unit cells are formed symmetrically with respect to an imaginary straight line passing through the center of the cylindrical periodic structure. The antenna according to any one of claims 1 to 7.   The plurality of unit cells are arranged so that distances between centers of loop slots of the unit cells adjacent in the circumferential direction are equal to each other. antenna.   The antenna according to any one of claims 1 to 9, wherein slot widths of loop slots in the plurality of unit cells are the same. The cylindrical periodic structure further includes a reflector disposed in a part of the circumferential direction thereof,
The antenna according to claim 3, wherein the reflecting plate is disposed at a position on the other side in the circumferential direction in at least one of the plurality of divided regions, or a position adjacent thereto.   The outer peripheral length of the loop slot in the said some unit cell arrange | positioned adjacent to the axial direction of the said cylindrical periodic structure body is mutually the same, The Claim 1 characterized by the above-mentioned. antenna.   The antenna according to any one of claims 1 to 12, wherein the cylindrical periodic structure is a radome. A manufacturing method of a cylindrical periodic structure comprising a plurality of unit cells periodically arranged in the circumferential direction and the axial direction and covering an antenna element,
A sheet provided with a plurality of unit cells periodically arranged in one direction and the other direction, wherein the unit cell includes a loop outer conductor, an inner conductor disposed inside the loop outer conductor, and the loop. Preparing a sheet including a plurality of types of unit cells having a loop slot formed between an outer conductor and the inner conductor, and the outer peripheral length of the loop slot being different from each other;
Preparing a core rod;
A step of laminating a plurality of coating layers on the peripheral surface of the core rod;
The sheet so that the plurality of unit cells are arranged along the circumferential direction and the axial direction of the one coating layer on the inner circumferential surface or the outer circumferential surface of any one of the plurality of coating layers. Winding process,
Of manufacturing a cylindrical periodic structure.   In the step of winding the sheet, when the coating layer is laminated on the outer peripheral side of the sheet, the direction in which the directivity of the antenna element is directed to the coating layer laminated on the outermost peripheral side among the plurality of coating layers. The manufacturing method of the cylindrical periodic structure of Claim 14 which further includes the process of providing the mark which can be visually recognized. A manufacturing method of a cylindrical periodic structure comprising a plurality of unit cells periodically arranged in the circumferential direction and the axial direction and covering an antenna element,
A step of preparing a basic cylinder;
A unit cell having a loop outer conductor, an inner conductor disposed inside the loop outer conductor, and a loop slot formed between the loop outer conductor and the inner conductor, wherein an outer peripheral length of the loop slot is A step of printing a plurality of different types of unit cells along the circumferential direction of the outer peripheral surface of the basic cylinder, and
Forming a protective layer for protecting the unit cells on the outer peripheral surfaces of the plurality of unit cells;
Of manufacturing a cylindrical periodic structure.   The method for manufacturing a cylindrical periodic structure according to claim 16, further comprising a step of providing the protective layer with a mark that allows the direction of directivity of the antenna element to be visually recognized. A cylindrical periodic structure covering the antenna element,
Covering the antenna element with the cylindrical periodic structure comprises a plurality of unit cells arranged periodically in the circumferential direction and the axial direction so that the directivity of the antenna element changes,
The unit cell includes a loop outer conductor, an inner conductor disposed inside the loop outer conductor, and a loop slot formed between the loop outer conductor and the inner conductor,
A cylindrical periodic structure including a plurality of types of unit cells having different outer peripheral lengths of the loop slot. As a constituent member of the cylindrical periodic structure covering the antenna element, a cylindrical periodic structure sheet disposed along the circumferential direction,
A plurality of unit cells periodically arranged in one direction that is the circumferential direction and the other direction,
The unit cell has a loop outer conductor, an inner conductor disposed inside the loop outer conductor, and a loop slot formed between the loop outer conductor and the inner conductor,
A sheet for a cylindrical periodic structure comprising a plurality of types of unit cells having different outer peripheral lengths of the loop slot. The plurality of unit cells are formed such that an outer peripheral length of the loop slot gradually decreases from the central portion in the one direction of the sheet for the cylindrical periodic structure toward both ends. Item 20. The sheet for a cylindrical periodic structure according to Item 19 .

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