Cylindrical antenna device

Abstract

To provide a cylindrical antenna device which has an elongated cylindrical shape not susceptible to large wind pressure load and efficiently receives horizontally polarized radio waves over a broad band.SOLUTION: There is provided a cylindrical antenna device in which a hole is made in a planar member, and a radiator and a reflector are built-in in a parallel state with spacing where a frame body and the planar member are together inside an antenna body. In the radiator 2, a feeding point 25 is provided approximately in the center of the radiator formed in a longitudinally long frame body 20, a square first loop 21 is provided above the feeding point, a square second loop 22 that shares one side with an upper side 27 parallel to a side 26 connected to the feeding point 25 is provided above the first loop 21, a square third loop 23 is provided below the feeding point 25, a square fourth loop 24 that shares one side with a lower side 28 parallel to the side 26 is provided below the third loop 23, and the four loops have respective total circumferential lengths different from each other. The reflector is formed of a longitudinally long planar member parallel to the radiator 2, the length of the reflector in a longitudinal direction is slightly longer than the length of the radiator in a longitudinal direction, and the length of the reflector in a transverse direction is slightly longer than the length of the radiator in a transverse direction in an arrangement parallel to the radiator 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cylindrical antenna device for receiving radio waves, and more specifically, to a cylindrical antenna device which is positioned as high above ground as possible to increase the receiving output, has a slender cylindrical shape to prevent it from being subjected to large wind pressure loads even when installed in a location where the radio waves are strong, and which efficiently receives horizontally polarized radio waves over a wide band. [Background technology]

[0002] Conventionally, for example, Patent Document 1 below discloses an antenna device that includes a radiator and a reflector, and has a plurality of vertically elongated diamond-shaped openings that are arranged so as to overlap each other on the plate surface of the reflector. Furthermore, claim 1 of Patent Document 2 discloses an antenna that includes a first loop antenna with a first short bar and a second loop antenna inside the first loop antenna that has a shorter loop length than the first loop antenna, and that connects the first loop antenna and the second loop antenna at a predetermined position with a second short bar.Claim 2 of the same patent document discloses an antenna configured as a skeleton slot antenna by forming a pair of the first loop antenna and the second loop antenna on the same plane with a feed point between them. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6073676 [Patent Document 2] Patent No. 4870496 Summary of the Invention [Problem to be solved by the invention]

[0004] The reflector described in Patent Document 1 has a large width in planar form, and when placed inside a cylinder, the diameter becomes large, which means that when installing the antenna, it is subjected to large wind pressure, requiring a large installation device and making it difficult to handle. Also, if it is made into a rectangular parallelepiped, the wind pressure coefficient becomes large. The antenna described in Patent Document 2 has a second loop antenna with a short loop length formed inside a first loop antenna, and the first and second loop antennas are connected at predetermined positions by a second short bar. However, with this configuration, the second loop antenna is on the same plane as the first loop antenna, causing interference and making it difficult to increase gain over a wide band, and these have been issues that need to be resolved.

[0005] Therefore, the object of the present invention is to solve the above-mentioned problems by providing a cylindrical antenna device that can be installed anywhere, has a small wind pressure coefficient, and has a diameter as small as possible so as to prevent large wind pressure loads, and that can, for example, receive horizontally polarized waves in a wide band from 470 MHz to 710 MHz to receive terrestrial digital broadcasting, and that achieves good gain characteristics over a wide band even when the horizontal dimension is significantly shorter than half the wavelength. [Means for solving the problem]

[0006] As a means for solving the problem, the invention described in claim 1 is a cylindrical antenna device in which a radiator 2 and a reflector 3 are built in an antenna body 1 having a vertically long cylindrical shape made of resin, The radiator 2 is a first rectangular loop 21 is provided above the feed point 25; a second rectangular loop 22 is provided above the first loop 21, sharing one side with an upper side 27 of the first loop 21 that is parallel to a side 26 having the feed point 25 of the first loop 21; a third rectangular loop 23 is provided below the feed point 25; a fourth rectangular loop 24 is provided below the third loop 23, sharing one side with a lower side 28 of the third loop 23 that is parallel to the side 26 having the feed point 25 and is connected to the feed point 25; and the four loops 21, 22, 23, and 24 have different perimeter lengths; The reflector 3 is The antenna is formed of a vertically long flat body 30 parallel to the vertically long radiator 2, and its vertical direction H is slightly longer than the length of the radiator 2, and its horizontal direction W is formed slightly larger than the radiator 2 when arranged parallel to the radiator 2, and a hole 32 is opened in the flat body 30, and bent sides 31 bent at an obtuse angle R so that the antenna can be built into the antenna body 1 are extended from both ends of the flat body 30. The radiator 2 and the reflector 3 are The frame bodies 20 and the planar bodies 30 are arranged parallel to each other at intervals that allow them to fit inside the cylindrical antenna body 1, and are built into the antenna body 1. The cylindrical antenna device is characterized by the above.

[0007] The invention described in claim 2 is characterized in that the hole 32 formed in the plane body 30 of the reflector 3 is formed in a vertically long elliptical shape S, and the hole 32 of the elliptical shape S is formed in three places, one at approximately the center in the vertical direction, and one above and one below it. The cylindrical antenna device according to claim 1 is characterized in that:

[0008] The invention described in claim 3 is characterized in that the hole 32 formed in the plane body 30 of the reflector 3 is formed in a vertically elongated octagon P, The cylindrical antenna device according to claim 1 is characterized in that: [Effects of the Invention]

[0009] The cylindrical antenna device of the present invention, despite its vertically long, slim cylindrical shape, can receive horizontally polarized waves with high gain, and can be installed in high locations such as on roofs for good reception. Furthermore, because of its cylindrical shape, the wind pressure coefficient is small even in strong winds such as typhoons, making it possible to install it with simple metal fittings, which is an excellent advantage. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a front view showing a radiator in the cylindrical antenna device of the present invention. [Figure 2] FIG. 1 is a perspective view showing a reflector with an oval hole. [Figure 3] FIG. 1 is a perspective view showing a reflector with an octagonal hole. [Figure 4] FIG. 2 is a cross-sectional view showing the internal structure of the cylindrical antenna device. [Figure 5] FIG. 2 is a perspective view showing the appearance of a cylindrical antenna device. [Figure 6] FIG. 2 is a perspective view showing a cylindrical antenna device in use. [Figure 7] 10 is a graph showing the electrical characteristics of the cylindrical antenna device. BEST MODE FOR CARRYING OUT THE INVENTION

[0011] A preferred embodiment of the cylindrical antenna device of the present invention will be described below with reference to the drawings. The cylindrical antenna device of this embodiment has a structure in which a radiator 2 and a reflector 3 are built into an antenna body 1 having a vertically long cylindrical shape made of resin as shown in Figure 5 (see Figure 4).

[0012] FIG. 1 shows a radiator 2 of the present cylindrical antenna device. Radiator 2 is formed in vertically long frame 20 and has feed point 25 located approximately in the center of radiator 2, with a square first loop 21 provided above feed point 25. Furthermore, square second loop 22 is provided above first loop 21, sharing one side with upper side 27 that is parallel to side 26 having feed point 25 of first loop 21. Furthermore, square third loop 23 is provided below feed point 25, and square fourth loop 24 is provided below third loop 23, sharing one side with lower side 28 of third loop 23 that is parallel to side 26 having feed point 25. The four loops 21, 22, 23, and 24 are formed to have different perimeter lengths.

[0013] That is, the overall length of loops 21, 22, 23, and 24 of the rectangular loop antenna is set to a dimension corresponding to the wavelength of the receiving frequency, and is set to the wavelength of each of the three frequencies at the ends, divided from low to high, and the loops are arranged with feed point 25 in the center as the reference, with loops 21 and 23 corresponding to the wavelengths of the two lowest frequencies arranged above them and loops 22 and 24 corresponding to the wavelengths of the next two highest frequencies connected in succession above them, and these four loops 21, 22, 23, and 24 arranged in succession are made into a vertically long rectangular shape, thereby reducing the width as viewed from the receiving direction and forming a slim, vertically long radiator 2 that can fit inside the cylindrical antenna device (Figure 4). Also, because the overall lengths of the four loops 21, 22, 23, and 24 are all different dimensions, the frequency characteristics of the receiving sensitivity are broadened.

[0014] More specifically, radiator 2 is a vertically elongated rectangle made of a thin metal conductor. A rectangular hole is drilled in a metal plate to form a loop-shaped antenna. Radiator 2 of this embodiment is composed of four rectangular loops (first to fourth) 21, 22, 23, and 24. These four loops 21, 22, 23, and 24 are stacked in multiple layers, with overlapping edges 26, 27, and 28 forming common edges. A second loop 22 is formed continuously with first loop 21, sharing one edge of its upper edge 27. A fourth loop 24 is formed continuously with third loop 23, sharing one edge of its lower edge 28. Edge 26 (the edge having feed point 25) shared by first loop 21 and third loop 23 in the center of this rectangular radiator 2 is cut in the middle, forming wide feed point 25 for impedance matching. The feeding point 25 of this loop antenna is balanced and is connected to a coaxial cable via a balanced-to-unbalanced balun (not shown), which is then connected to an output connector 10 provided on the lower bottom plate of the cylindrical antenna body 1 (Figure 5).

[0015] The total circumference of each rectangular loop 21, 22, 23, or 24, calculated by adding up all four sides, is the wavelength of the received frequency. When used as a receiving antenna for terrestrial digital broadcasting, the broadcast frequency band is 470 MHz to 710 MHz, so this band is divided into thirds. The frequencies at the ends of the thirds are 470 MHz, 550 MHz, 630 MHz, and 710 MHz, with wavelengths of 638 mm, 545 mm, 476 mm, and 422 mm, respectively. The actual total length of the loop is shortened by the dielectric constant of the resin that constitutes the antenna's exterior, and is therefore smaller than the calculated size. The dimensions of the radiator 2 of this embodiment, in order of frequency, for each of the loops 23, 21, 22, and 24 are approximately 554 mm (approximately 202 mm long), 474 mm (approximately 162 mm long), 414 mm (approximately 132 mm long), and 368 mm (approximately 109 mm long). In this case, the reduction due to the dielectric constant is approximately 1.15 times. In this way, by matching the overall length of each loop 23, 21, 22, 24 to the wavelength of each band of receiving frequencies, it is possible to resonate at each frequency in the receiving band. The graph in Figure 7 shows the experimental data, with the solid line showing the operating gain when the four loops 21, 22, 23, 24 of the above-mentioned radiator 2 are changed for each frequency, and the dashed line showing the operating gain of the conventional loop.

[0016] FIG. 2 shows the reflector 3 of the present cylindrical antenna device. This reflector 3 is formed of a vertically long flat body 30 that is parallel to the vertically long radiator 2, and its vertical direction H is slightly longer than the length of radiator 2, and its horizontal direction W is formed slightly larger than radiator 2 when arranged parallel to radiator 2. Holes 32 are made in flat body 30, and bent sides 31 that are bent at an obtuse angle R extend from both ends of flat body 30 so that the reflector can be built into antenna body 1.

[0017] That is, the reflector 3 of this embodiment has a reduced depth width W as viewed from the receiving direction of the antenna. Generally, the distance between the radiator and the reflector needs to be one-fourth the wavelength of the receiving frequency. If the antenna were to be made cylindrical as is, a very large diameter would be required. Therefore, a vertically elongated elliptical hole S is drilled in the reflector 3, centered on the horizontal side 26 that includes the feed point 25 at the center of the radiator 2, and three similar vertically elongated elliptical holes S are drilled in the reflector 3 corresponding to the next horizontal sides 27 and 28 from the center of the radiator 2, thereby making the distance between the radiator 2 and the reflector 3 shorter than one-fourth the wavelength of the receiving frequency.

[0018] Specifically, a thin metal conductor plate is formed into a vertically long rectangle, with three elliptical S-shaped holes 32 drilled vertically in the horizontal center. Each of the two horizontal ends is bent diagonally by a specified distance, for example, at an obtuse angle R of approximately 105°. The diagonal bending is intended to maximize gain by positioning the antenna at the farthest position from the radiator 2 within the cylindrical shape. The dimensions of each part of the terrestrial digital broadcasting receiving antenna are approximately 665 mm in length in the vertical direction H and approximately 85 mm in the horizontal direction W, with the ends bent diagonally at an obtuse angle R of approximately 105° for lengths of approximately 40 mm. The dimensions of the elliptical S-shaped holes 32 are as follows: the central one has a major axis of approximately 205 mm in the vertical direction and a minor axis of approximately 65 mm in the horizontal direction. The dimensions of the elliptical S-shaped holes 32 above and below it are both approximately 170 mm in length and approximately 65 mm in minor axis.

[0019] The reflector 3 shown in Fig. 3 is characterized in that the shape of the hole 32 opened in the reflector 3 is a vertically long octagon P, which strengthens resonance at a specific frequency and increases gain overall over a wide band from low to high frequencies, thereby achieving good electrical characteristics, i.e., high gain and good VSWR (standing wave ratio), while maintaining a constant distance between the radiator 2 and the reflector 3. By making the shape of the hole 32 a vertically long octagon P, the rectangular space formed by the long sides in the center can resonate at low frequencies, and the trapezoidal space formed by the next slanted sides can resonate at high frequencies over a wide band.

[0020] Specifically, a thin metal conductor plate is formed into a vertically long rectangle, with three octagonal P-shaped holes 32 drilled vertically in the middle of the horizontal direction, and both horizontal ends bent diagonally to a specified distance to form bent edges 31. The dimensions of each part of the terrestrial digital broadcasting receiving antenna are the same as those of the reflector 3 shown in Figure 2, with a total length of approximately 665 mm in the vertical direction and a horizontal dimension of approximately 85 mm, with extensions from both ends bent to a length of approximately 40 mm at an obtuse angle R of approximately 105°. The dimensions of the octagonal P-shaped holes 32, when implemented in a configuration with a rectangular central portion and trapezoids above and below, are such that the long side of the central rectangle is approximately 125 mm and the short side (horizontal) is approximately 65 mm. The dimensions of the trapezoids above and below each other are both approximately 40 mm high, with an upper base of approximately 15 mm, and a lower base of approximately 65 mm. The long sides of the rectangles of the octagonal holes 32 at the top and bottom are approximately 90 mm, and the upper and lower trapezoids have the same dimensions as the trapezoid in the middle.

[0021] Thus, as shown in Figure 4, the above-mentioned radiator 2 and reflector 3 are built into the antenna body 1 with their respective frame bodies 20 and planar bodies 30 arranged parallel to each other with a distance that allows them to fit inside the cylindrical antenna body 1. In this embodiment, a radiator 2 and a reflector 3 are arranged at an interval of about 65 mm within a cylindrical antenna body 1 having an inner diameter of about 107 mm.

[0022] FIG. 5 shows the appearance of the cylindrical antenna device described above. A mast fixing bracket 5 is attached to the lower end of the antenna body 1, and can also be attached to the middle of the mast 6. Furthermore, because the mast fixing bracket 5 is attached to a position behind the reflector 3, it does not affect reception performance and makes it easy to orient the cylindrical antenna device in the receiving direction when installing the antenna, facilitating direction adjustment.

[0023] FIG. 6 shows an example of installation of the cylindrical antenna device on a roof 7 as an example of use. The cylindrical antenna device is fixed with a mast fixing bracket 5 to a J-shaped mast bracket 6 attached to a gable board 70 on the gable side of the roof 7. This means that this cylindrical antenna device is positioned higher than the roof 7, and stable reception can be expected even in areas with relatively weak radio waves. When adjusting the direction, the mast fixing bracket 5 is attached to the reflector 3 side rather than the radiator 2 side, so it can be adjusted from behind the direction in which the radio waves are coming, making it a very easy-to-use structure. In addition, because the mast fixing bracket 5 is attached to the outside of the antenna main body 1, it has the advantage of being able to be attached to the middle of the long mast 6.

[0024] Although the embodiments have been described above based on the drawings, it should be noted that the present invention is not limited to the illustrated examples and includes the range of design modifications and application variations that would normally be made by a person skilled in the art, provided that they do not deviate from the technical concept of the present invention. [Explanation of symbols]

[0025] 1 Antenna body 2 Radiators 20 Frame 21 First Loop 22 Second Loop 23 The Third Loop 24 The Fourth Loop 25 Power supply point 26 Side with power supply point 27 Surface 28 Bottom 3 reflector 30 plane 31 Folded Edge 32 holes H Vertical W Horizontal S oval P Octagon R obtuse angle

Claims

1. A cylindrical antenna device in which a radiator and a reflector are built into a vertically long cylindrical antenna body made of resin, The radiator comprises: a feed point is provided at approximately the center of the radiator formed in a vertically long frame, a square first loop is provided above the feed point, a square second loop is provided above the first loop and has one side in common with an upper side parallel to the side having the feed point of the first loop, a square third loop is provided below the feed point, and a square fourth loop is provided below the third loop and has one side in common with a lower side parallel to the side having the feed point and connected to the feed point of the third loop, and the four loops have different perimeter lengths; The reflector is the antenna is formed of a vertically long flat body parallel to the vertically long radiator, the vertical direction of which is slightly longer than the length of the radiator, and the horizontal direction of which is slightly larger than the radiator when arranged parallel to the radiator, and a hole is made in the flat body, and bent sides bent at obtuse angles so as to be able to be built into the antenna main body are extended from both ends of the flat body; The radiator and the reflector are The frame body and the plane body are disposed parallel to each other at an interval sufficient to fit inside the cylindrical antenna body, and are built into the antenna body. A cylindrical antenna device characterized by:

2. The hole formed in the plane body of the reflector is formed in a vertically long elliptical shape, and the elliptical hole is formed at three locations, approximately at the center in the vertical direction, and above and below the center.

2. The cylindrical antenna device according to claim 1, wherein:

3. The hole formed in the plane of the reflector is formed in a vertically elongated octagonal shape; 2. The cylindrical antenna device according to claim 1, wherein:

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