Antenna equipment

Abstract

To provide an antenna device which has improved gain while maintaining the compactness that is an advantage of small antennas.SOLUTION: In an antenna device for linear polarization, equipped with a small antenna 1 in which a reflecting element 10 and a feeding element 11 that constitute the antenna are covered with resin 13, at least one resonating element 2 made of a metal conductor longer than 1 / 2 the wavelength of the center frequency of the frequency band used is arranged above and below the small antenna 1 so as to be parallel to the internal elements 10 and 11 of the small antenna 1 covered with the resin 13, and the resonating element 2 is fixed to the tip 30 of a support 3 fixed to a mast mounting bracket main body 4 that attaches the small antenna 1 to a mast 8.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an antenna device that accommodates a reflective element and a feeding element inside a resin, and more particularly, belongs to the technical field of an antenna device that improves gain while maintaining the compactness, which is an advantage of small antennas, when used as a shared reception antenna for apartments and small condominiums. [Background Art]

[0002] In recent years, for antennas receiving terrestrial digital television broadcasting (470 to 710 MHz), design antennas with antenna elements covered by resin have become mainstream, replacing Yagi-Uda antennas with exposed antenna elements. As an antenna device that accommodates elements constituting an antenna in a resin case, there is one disclosed in the following Patent Document 1 (Japanese Patent No. 5360808). This is a conventional terrestrial digital television broadcasting receiving antenna, which is compact and can be used by being mounted on a mast attached to a balcony or a side wall of a roof. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent No. 5360808 [Patent Document 2] Japanese Patent No. 4519034 [Summary of Invention] [Problem to be Solved by the Invention]

[0004] The antenna of Patent Document 1 is relatively small, so the gain is particularly low in terms of reception performance. Therefore, improvement of the gain is required for use as a shared reception antenna for apartments and small condominiums. Generally, antennas with high gain tend to be large. If the entire large antenna is encased in resin, the resulting case becomes large and very expensive. Furthermore, the mold used to create the case also becomes large and very expensive. There is also the problem that a larger surface area leads to a larger wind-receiving area and a decrease in wind speed resistance. In addition, to improve gain, there are antennas like the one disclosed in Patent Document 2 (Patent No. 4519034) that use two sets of antennas, each consisting of a director element, a feeding element, and a reflecting element, inside a resin case and combine the signals to improve gain. However, this method has many components and is costly, which is a problem that needs to be solved.

[0005] Therefore, the object of the present invention is to provide an antenna device that improves gain while maintaining the compactness that is an advantage of small antennas. [Means for solving the problem]

[0006] As a means to solve the problem, the invention described in claim 1 is a linear polarization antenna device comprising a small antenna 1 in which the reflecting element 10 and the feeding element 11 constituting the antenna are covered with resin 13, The antenna device is characterized in that one or more resonant elements 2, made of a metal conductor whose wavelength is longer than half the wavelength of the center frequency band used, are arranged above and below the small antenna 1 so as to be parallel to the internal elements 10 and 11 of the small antenna 1 covered with the resin 13.

[0007] The invention described in claim 2 is the antenna device described in claim 1, characterized in that the resonant element 2 is fixed to the tip 30 of a support 3 which is fixed to the mast mounting bracket body 4 for attaching the small antenna 1 covered with the resin 13 to the mast 8.

[0008] The invention described in claim 3 is an antenna device according to claim 1 or 2, characterized in that one or more resonant elements 2 arranged above and below the small antenna 1 are cylindrical metal conductors 2A, and their diameter is formed to be thicker than 1 / 50 of the wavelength of the center frequency of the operating frequency band.

[0009] The invention described in claim 4 is an antenna device according to claim 1 or 2, characterized in that one or more resonant elements 2 arranged above and below the small antenna 1 are flat metal conductors 2B, and the length of the shorter side is formed to be longer than 1 / 50 of the wavelength of the center frequency of the operating frequency band.

[0010] The invention described in claim 5 is such that the mast mounting bracket body 4 to which the small antenna 1 is attached is fixed to the support 3, a groove 50 is formed in a cross shape on the back portion 51 of the mast mounting fastener 5 which is fixed to the mast mounting bracket body 4, and notches 60 are formed on the four sides 61 of the box-shaped mast mounting adjustable device 6 which is fixable to the mast mounting fastener 5 and has a front opening. The antenna device according to claim 2 is characterized in that, when the mast mounting fixture 5 and the mast mounting adjustable fixture 6 are fixed to the mast 8, the entire small antenna 1 can be rotated 90° together with the groove 50 of the mast mounting fixture 5 and the notch 60 of the mast mounting adjustable fixture 6 and fixed to the mast 8, and the small antenna 1 is configured to be selectable between a horizontal polarization receiving type where it is positioned horizontally and a vertical polarization receiving type where it is positioned vertically. [Effects of the Invention]

[0011] According to the antenna device of the present invention, high gain can be achieved simply by adding resonant elements to the top and bottom of a conventional small antenna covered with resin. Therefore, there is no need to prepare a particularly large resin case, and a decrease in wind resistance can be prevented. Furthermore, despite the significant improvement in gain, it does not use a method that places multiple directors in front of the feed point and a large reflector behind it, as is the case with Yagi antennas. Therefore, when installed near a wall, it does not protrude far forward from the wall, making it compact and easy to install, and the configuration of simply arranging resonant elements at the top and bottom also contributes to cost reduction. [Brief explanation of the drawing]

[0012] [Figure 1] This is a perspective view showing the antenna device of the present invention. [Figure 2] This is a perspective view showing the internal structure of a small antenna. [Figure 3] Figure 1 is a side view of an antenna device in which the resonant element is a cylindrical metal conductor. [Figure 4] This is a perspective view showing an antenna device in which the resonant element is a flat metal conductor. [Figure 5] Figure 4 is a side view of an antenna device in which the resonant element is a flat metal conductor. [Figure 6] This is a perspective view showing the procedure for attaching the mast mounting bracket body and mast mounting fastener to the support, and further, the procedure for attaching the adjustable mast mounting device to the mast mounting fastener. [Figure 7] This is a perspective view (A) of a mast mounting bracket shown from the rear, a perspective view (B) of the same mast mounting bracket shown from the front, and a perspective view (C) of a different mast mounting bracket shown from the front. [Figure 8] This is a rearward perspective view of the antenna device mounted on the mast when applied for horizontal polarization reception. [Figure 9] This is a rearward perspective view of the antenna device mounted on the mast when applied for vertical polarization reception. [Figure 10] This graph shows a comparison of gains. BEST MODE FOR CARRYING OUT THE INVENTION

[0013] Preferred embodiments of the antenna device according to the present invention will be described below with reference to the drawings. This antenna device is a small antenna 1 covered with resin 13, and the gain can be significantly improved by providing resonant elements 2 above and below the antenna. The basic configuration of the antenna device of the present embodiment is a linearly polarized antenna device including a small antenna 1 in which a reflecting element 10 and a feeding element 11 constituting the antenna are covered with resin 13, and has a structure with a small wind-receiving area that is less susceptible to strong winds such as typhoons. As shown in Fig. 2, the internal elements of the small antenna 1 are preferably implemented in a configuration including a reflecting element 10, a feeding element 11, and a waveguide element 12. Resonant elements 2, which are made of a metal conductor longer than 1 / 2 of the wavelength of the center frequency of the used frequency band, are arranged one each on the top and bottom (two in total) of the small antenna 1 covered with resin 13 so as to be parallel to the internal elements 10 and 11 of the small antenna 1. That is, as shown in Fig. 8, the resonant elements 2 are fixed to the upper and lower distal ends 30 of the support 3 fixed to the mast mounting bracket main body 4 for attaching the small antenna 1 to the mast 8, so as to be arranged parallel to the internal elements of the small antenna 1. However, the number and arrangement of the resonant elements 2 are not limited thereto, and an embodiment in which one or more resonant elements are arranged at desired positions can also be adopted.

[0014] A specific example will be described in which the antenna device of the present embodiment is used as a terrestrial digital television broadcast receiving antenna. The used frequency band is 470 MHz to 710 MHz, the center frequency is 590 MHz, and 1 / 2 of its wavelength is 254 mm. The small antenna 1 located in the center shown in Fig. 1 has a reflecting element 10, a feeding element 11, and a waveguide element 11, which constitute the antenna, incorporated at predetermined intervals in a resin case 13 having an outer dimension of 270×120×70 mm (Fig. 2). The feeding element 11 is connected to an output connector (not shown), and this small antenna portion alone functions as an antenna. The compact small antenna 1 is attached to a mast mounting bracket composed of a mast mounting bracket body 4 and a mast mounting fixture 5 (Figs. 1 and 2). The support 3 is formed in a C-shape, and may be made of a square pipe made of metal such as aluminum, or may be made of resin or the like. The mast mounting bracket body 4 of the small antenna 1 is fixed to the central portion of the support 3 in a vertically arranged state, and the center of the resonant element 2 having a length equal to or more than 1 / 2 of the wavelength of the center frequency of the used frequency band is fixed to each of the upper and lower tip portions 30 of the C-shaped support 3.

[0015] The gain reaches the maximum when the spacing between the internal elements 10, 11, 12 of the small antenna 1 and the resonant elements 2 provided above and below the small antenna 1 is about 1 / 2 of the wavelength of the center frequency of the used frequency band, but the spacing may be narrower or wider than that (see Figs. 3 and 5). For the resonant element 2, the larger the diameter, or the wider the width of the short side of the conductor, the more the gain tends to improve over a wide frequency band. When this is expressed by the wavelength of the center frequency of the used frequency band, if the resonant element 2 is cylindrical, the effect becomes noticeable starting from about 1 / 50 of the wavelength, and the gain does not increase much when the diameter is more than 1 / 12 of the wavelength. The optimal dimension is around 1 / 15 of the wavelength. If the resonant element 2 is flat-plate-shaped, the optimal width of the short side is about 1 / 5 of the wavelength.

[0016] The resonant element 2 may be a cylindrical (pipe-shaped) metal conductor 2A as shown in Figure 1, or a rectangular (flat plate-shaped) metal conductor 2B made of a flat plate as shown in Figure 4. In the case of the cylindrical resonant element 2 shown in Figures 1 and 3, it is made of aluminum, has a diameter of 30 mm, and a length of 300 mm (longer than half the wavelength of the center frequency of the operating frequency band). This cylindrical resonant element 2 may be directly attached to the support 3, or it may be mounted inside a resin case for design reasons (not shown). When mounted inside a resin case, the resonant element 2 may be made by forming a cylinder out of aluminum foil. Alternatively, an aluminum plate may be made into a flat plate-shaped resonant element 2 measuring 100 mm x 300 mm and covered with a resin case before mounting. The separation distance between the resonant element 2 and the small antenna 1 is 250 mm both vertically and horizontally.

[0017] Next, the procedure for attaching the mast mounting bracket body 4 and the mast mounting fastener 5 to the support member 3 will be explained. As shown in Figure 6, the mast mounting bracket body 4 has a vertical front section 40, with side sections 41 formed on both the left and right sides, and two bolt holes 42 drilled in each of the side sections 41. In addition, an L-shaped upper section 43 and an L-shaped lower section 44 are formed above and below the front section 40, and the vertical sections of these are fixed via bolts 45 so that the front section 40 is positioned approximately in the center of the support 3. On the other hand, the mast mounting fixture 5 has a vertical back portion 51, with side portions 53 formed on both the left and right sides, and two bolt holes 54 are drilled in each of the side portions 53. The back portion 51 has a cross-shaped V-groove 50, which will be described later. Therefore, the side portions 53 of the mast mounting fixture 5 and the side portion 41 of the mast mounting bracket body 4 overlap and meet, and bolts 7 are tightened from the side into the bolt holes 54 and 42, respectively, to fix the two together. Thus, the support 3 to which the small antenna 1 is attached is secured to the mast 8 by bolts 7, sandwiching the mast 8 between the mast mounting fastener 5 and the mast mounting adjustable fastener 6 at the front and rear of the mast 8 (Figures 6 and 8).

[0018] The size of the mast mounting bracket body 4 varies depending on the diameter of the mast 8 to which it is attached. For example, if the diameter of the mast 8 is 48.5 mm, the groove portion 50 on the back portion 51 of the mast mounting fixture 5 (which has two bolt holes 52), where a V-groove is formed in a cross shape in the depth direction, will be approximately 85 x 85 mm in size and will be made from a 1.6 mm thick steel plate by press bending. The adjustable mast mounting bracket 6 corresponds to the groove 50 of the mast mounting fastener 5 and is also made of a steel plate in the shape of a perfect square of 85 x 85 mm by press bending. The four sides 61 are processed into a box shape with a front opening, with the four sides protruding about 15 mm from the vertically positioned back surface 62 (which has two bolt holes 63). A V-shaped notch 60 is formed in the center of each side of the four sides 61. The notch 60 may be formed with a jagged V-shape at the end face to increase the fixing force to the mast 8, as shown in Figures 7A and 7B, or it may be a V-shaped notch 60' with a flat end face without jagged edges, as shown in Figure 7C. Therefore, the V-shaped groove 50 of the mast mounting fixture 5 and the V-shaped notch 60 of the mast mounting adjustable fixture 6 face each other, sandwiching the mast 8, and both 5 and 6 are fixed together by two bolts 7 screwed from the back into matching bolt holes 52 and 63. In addition, since the V-shaped groove 50 and the V-shaped notch 60 are cross-shaped and can contact the mast 8 at 90° intervals, the mast 8 can be easily sandwiched and used for both horizontal and vertical polarization.

[0019] The following describes the selection and use of a horizontal polarization receiving type (Figure 8) in which the small antenna 1 is positioned horizontally, and a vertical polarization receiving type (Figure 9) in which it is positioned vertically. Antennas need to be aligned with the polarization plane of incoming radio waves, and linear polarization has both horizontal and vertical polarization. As shown in Figures 8 and 9, receiving antennas need to be installed to match this polarization plane. Conventionally, it was necessary to remove the mounting bracket from the antenna body and change its position, for example, from horizontal polarization reception to vertical polarization reception. Alternatively, in Yagi antennas with a bracket that allows for movement between horizontal and vertical polarization reception, it was necessary to move this movable part.

[0020] In this respect, the antenna device of this embodiment has a cross-shaped V-shaped groove 50 formed on the back surface 51 of the mast mounting fixture 5 which is fixed to the mast mounting bracket body 4 as described above, and V-shaped notches 60 are formed on each of the four sides 61 of the corresponding mast mounting adjustable fixture 6. Therefore, it is possible to immediately switch between horizontal polarization reception (Figure 8) and vertical polarization reception (Figure 9) without changing the mounting position of the fixture or moving the movable parts. In other words, the fixing device 5 and the adjustable device 6 are secured to the mast 8 by tightening them with bolts 7 (Figures 8 and 9). However, whether receiving horizontal or vertical polarization, the mast mounting bracket body 4 does not need to be removed from the antenna body. By simply loosening the bolts 7 and rotating the entire small antenna 1 by 90° along with the groove 50 of the fixing device 5 and the notch 60 of the adjustable device 6, the antenna device can be inserted from the top of the mast 8 and easily secured to either polarization plane. In this sense, both the mast mounting fixing device 5 and the mast mounting adjustable device 6 can be considered horizontal / vertical compatible devices.

[0021] Figure 10 shows the gain characteristics of the antenna device described above for each frequency. The dashed line shows the gain characteristics of a conventional small antenna, and the solid line shows the gain characteristics of the proposed antenna. The gain has increased by approximately 1.5 dB to 3 dB at all frequencies. This improvement in gain is because, unlike conventional small antennas where the electric field of received radio waves arriving from above or below simply passes through, this embodiment places resonant elements 2 at positions 1 / 2 wavelength apart above and below the small antenna 1, thereby retaining the passing electric field and coordinating it with the electric field of the central small antenna portion, thereby improving reception sensitivity.

[0022] Although 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 design modifications and variations in application that are ordinarily performed by those skilled in the art, without departing from the technical idea. [Explanation of Symbols]

[0023] 1. Small antenna 10 Reflector 11 Power supply element 12 Waveguide elements 13. Resin (case) 2. Resonant element 2A cylindrical metal conductor 2B Flat metal conductor 3 Supports 30 Tip 4. Mast mounting bracket body 5. Mast mounting fasteners 50 groove section 51 Back section 6. Mast mounting device 60 Notch 61 Quadrilateral 7 volts 8 Mast

Claims

1. In a linear polarization antenna device comprising a small antenna in which the reflecting element and feeding element constituting the antenna are covered with resin, An antenna device characterized in that one or more resonant elements, made of a metal conductor whose wavelength is longer than half the wavelength of the center frequency of the operating frequency band, are arranged above and below a small antenna so as to be parallel to the internal elements of the small antenna covered with resin.

2. The antenna device according to claim 1, characterized in that the resonant element is fixed to the end of a support fixed to a mast mounting bracket body for attaching the resin-covered small antenna to the mast.

3. The antenna device according to claim 1 or 2, characterized in that one or more resonant elements arranged above and below the small antenna are cylindrical metal conductors, and their diameter is thicker than 1 / 50 of the wavelength of the center frequency of the operating frequency band.

4. The antenna device according to claim 1 or 2, characterized in that one or more resonant elements arranged above and below the small antenna are flat metal conductors, and the length of the shorter side is longer than 1 / 50 of the wavelength of the center frequency of the operating frequency band.

5. The mast mounting bracket body to which the small antenna is attached is fixed to the support, and a groove is formed in the shape of a cross on the back of the mast mounting fastener fixed to the mast mounting bracket body, and notches are formed on all four sides of a box-shaped mast mounting adjustable device that can be fixed to the mast mounting fastener and has a front opening. The antenna device according to claim 2, characterized in that when the mast mounting fixture and the adjustable mast mounting fixture are fixed to the mast, the entire small antenna can be rotated 90° together with the groove of the mast mounting fixture and the notch of the adjustable mast mounting fixture and fixed to the mast, and the device is configured to allow selection of a horizontal polarization receiving type in which the small antenna is positioned horizontally and a vertical polarization receiving type in which it is positioned vertically.

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