Planar antenna

Abstract

To provide a planar antenna with efficiently improved gain at a low cost in order to stabilize reception.SOLUTION: A receiving antenna 1 consists of a radiator 2 and a reflector 3, the radiator 2 is approximately square, and the reflector 3 is approximately square, slightly larger than the radiator 2. A distance K between the radiator 2 and the reflector 3 is smaller than one-eighth of the wavelength of the center frequency of the receiving band, side walls 30 bent toward the radiator 2 are formed on two sides of the reflector 3, the depth D of the side wall 30 is shorter than the distance K between the radiator 2 and reflector 3, and each of the two side walls 30 is provided with a notch 5 that corresponds to the wavelength at approximately the center in the height H direction and forms a space S between the radiator 2 and the side wall 30.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention belongs to the technical field of planar antennas with improved gain for stable reception.

Background Art

[0002] The higher the gain of a receiving antenna, the better the signal quality (C / N) of the received signal and the more stable the reception. Therefore, improving the gain is important in antenna design.

[0003] For example, Patent Document 1 below discloses a patent for miniaturizing a planar antenna. In this patent, both sides of the reflector are bent to provide side portions. It is described that the antenna with side portions has improved electrical characteristics compared to the antenna without side portions. These side portions are simple and linear. It is also described that when the distance between the radiating element and the reflector is reduced, the electrical characteristics deteriorate (see Claim 1, Paragraph

[0017] , etc. of the same Document 1).

[0004] Also, Patent Document 2 below discloses that characteristics are improved by optimizing the polygonal gap shape above and below the feeding point of the front element. Further, a standing upper portion with a bent side surface is specified for the rear element (see Claim 1, Paragraphs

[0011]

[0014] , etc. of the same Document 2).

[0005] Furthermore, Patent Document 3 below describes an antenna device in which a plurality of protruding pieces protruding in the direction of the radiator are provided at intervals on the edge of a plate-like member constituting a reflector, which is bent in the direction of the radiator (see Claim 3, Paragraph

[0068] , FIG. 3, etc. of the same Document 3).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

[0007] The riser described in Patent Document 2 is simple and linear, and does not provide the effect of increasing the gain. Furthermore, while Patent Document 3 describes that there are multiple protruding pieces and that the effect of these protruding pieces does not affect the operating gain but improves the front-to-back ratio, it does not mean that they operate in a way that improves the gain.

[0008] Therefore, the object of the present invention is to provide a low-cost planar antenna that efficiently improves gain and stabilizes reception. [Means for solving the problem]

[0009] As a means to solve the problem, the invention described in claim 1 is a terrestrial digital broadcast enclosed in a roughly rectangular cube-shaped case 4 For In a planar antenna equipped with a receiving antenna 1, The receiving antenna 1 is composed of a radiator 2 and a reflector 3. The radiator 2 is roughly rectangular in shape, and the reflector 3 is formed as a roughly rectangular shape slightly larger than the radiator 2, and the distance K between the radiator 2 and the reflector 3 is less than one-eighth of the wavelength of the center frequency of the receiving band. Two sides of the reflector 3 have bent side walls 30 that face the radiator 2, and the depth D of the side walls 30 is shorter than the distance K between the radiator 2 and the reflector 3. Each of the two side walls 30 is provided with a notch 5 cut out in a stepped pattern on its end face, approximately in the center of the height direction H, with dimensions corresponding to the wavelength of the receiving frequency, so as to form a space S between the radiator 2 and the side wall 30. It is a planar antenna characterized by the following:

[0010] The invention described in claim 2 is such that the notch 5 of the side wall 30 of the reflector 3 is formed in a stepped shape by a first notch 51 and a second notch 52. The first notch 51 is formed in pairs at the upper and lower positions approximately in the center in the height H direction of the side wall 30, with each notch being formed at a height H2 of approximately 0.08λ and a depth D2 of approximately 0.01λ. The second notch 52 is formed between the upper and lower pair of first notches 51, 51, with a height H3 of approximately 0.16λ and a depth D3 extending approximately 0.01λ further from the end face 51a of the first notch 51. This is a planar antenna as described in claim 1, characterized by the following:

[0011] The invention described in claim 3 is a planar antenna as described in claim 1, characterized in that the notch 5(53) of the side wall 30 of the reflector 3 is formed in an elliptical shape approximately in the center in the height H direction of the side wall 30, with a notch height H4 of approximately 0.32λ and a maximum depth D4 of approximately 0.02λ relative to the wavelength λ of the center frequency of the receiving band. [Effects of the Invention]

[0012] According to the planar antenna of the present invention, by providing a notch in the side wall of the reflector corresponding to the wavelength of the receiving frequency, and creating a space between it and the radiator, the gain can be efficiently improved, and reception stabilization can be achieved at low cost. [Brief explanation of the drawing]

[0013] [Figure 1] This is a perspective view showing the receiving antenna of the planar antenna of the present invention. [Figure 2] This is a perspective view showing a reflector. [Figure 3] This is a side view showing the side wall of the reflector in Figure 2. [Figure 4] This is a front view showing the radiator. [Figure 5] This is an overall perspective view of the receiving antenna in a vertical stacked configuration. [Figure 6]It is a side view showing different side walls of the reflector. [Figure 7] It is an overall perspective view showing a planar antenna. [Figure 8] It is a graph showing the change in the gain of the electrical characteristics when the notch is implemented and when it is not implemented in the stacked state of FIG. 5.

Best Mode for Carrying Out the Invention

[0014] A preferred embodiment of the planar antenna of the present invention will be described below with reference to the drawings. This planar antenna includes a receiving antenna 1 surrounded by a substantially rectangular cubic case 4 (FIG. 7). The receiving antenna 1 is composed of a combination of a radiator 2 and a reflector 3 as shown in FIG. 1. In the reflector 3, the depth D of the side walls 30 provided on both sides corresponding to the polarization plane of the received linearly polarized wave is formed shorter than the distance K between the radiator 2 and the reflector 3, and a notch 5 (described later) is formed by cutting out the end face at substantially the center in the longitudinal direction of the side walls 30 with dimensions corresponding to the wavelength of the received frequency, thereby improving the gain.

[0015] Generally, it is said that when the distance between the radiator and the reflector is about 1 / 4 of the wavelength of the received frequency, the gain becomes high. However, for planar antennas, there is a requirement that they be thinner and smaller for better appearance and usability. In particular, when the thickness is reduced and the distance between the radiator and the reflector is narrowed to reduce the gap with the side walls, the gain significantly decreases. Therefore, the inventors of the present application have found that the gain can be improved by cutting out the height of the side walls in a curved shape corresponding to the long axis of an ellipse at substantially the center in the longitudinal direction of the side walls (the second embodiment below) or in a stepped shape approximating the curve (the first embodiment below). This is to allow the electric field generated between the radiator and the reflector to appropriately escape to the outside, so that the performance of the radiator and the reflector can be fully exerted.

[0016] In this embodiment, as shown in Figure 1, the radiator 2 at the front is roughly rectangular, and the reflector 3 at the back is roughly rectangular, slightly larger than the radiator 2. The distance K between the radiator 2 and the reflector 3 is set to be less than one-eighth of the wavelength of the center frequency of the receiving band. Two sides of the reflector 3 have side walls 30 that are bent toward the radiator 2 side (front), and the depth D of these side walls 30 is set to be shorter than the distance K between the radiator 2 and the reflector 3. In other words, the side walls 30 of the reflector 3 are formed on the sides corresponding to the receiving polarization of the reflector 3, and in the case of horizontal polarization P, they are formed perpendicular to the left and right sides. In the case of a vertical polarization receiving antenna, the radiator 2 and reflector 3 are rotated by 90 degrees, and the side walls 30 of the reflector 3 are formed on the top and bottom sides (illustration omitted). First Embodiment

[0017] The stepped notch 5 according to the first embodiment will now be described. The notches 5 of the reflector 3 shown in Figure 2 are provided in pairs on the left and right side walls 30 of the reflector 3, cut out approximately in the center in the height H direction corresponding to the wavelength and forming a space S between the radiator 2 and the side wall 30. As shown in Figure 3, these stepped notches 5 are formed in a stepped manner on each side wall 30 by a shallow first notch 51 and a deep second notch 52. Specifically, the first notches 51 are formed in pairs at the upper and lower positions approximately in the center of the height H direction (see Figure 2) of the side wall 30, with each notch having a height H2 of approximately 0.08λ and a depth D2 of approximately 0.01λ. The second notches 52 are formed between the upper and lower pair of first notches 51, 51, with a height H3 of approximately 0.16λ and a depth D3 of approximately 0.01λ further from the end face 51a of the first notches 51.

[0018] The following describes this first embodiment in more detail. Figure 7 shows the overall shape of a planar antenna when used as a terrestrial digital broadcasting receiving antenna. The internal receiving antenna 1 (Figure 1) is covered by a synthetic resin case 4, and a mounting bracket 6 is provided on the back for attachment to a wall or pole. The shape of the radiator 2 installed inside the synthetic resin case 4 is as shown in Figure 4, with a vertical height H5 of 265 mm and a maximum horizontal width W2 of 200 mm, and rounded corners. The reflector 3 has the shape shown in Figure 2, with a vertical height H of 270 mm and a horizontal width W of 215 mm, and the depth D of the side wall 30 is set to 27 mm.

[0019] In this embodiment, the notch shape of the side wall 30 of the reflector 3 is cut in a stepped manner, as shown in Figure 3. The dimensions of the notch 5 are such that the upper and lower first notches 51 and the second notches 52 are cut out to a depth of 5 mm from the side wall end face at a maximum height of 160 mm, with a height H2 of 40 mm. The second notch 52 is implemented on the end face of the first notch 51, with a height H3 of 80 mm from the end face, and is cut out to a depth of 5 mm, forming approximately in the center of the side wall 30 in the height direction. Second Embodiment

[0020] Figure 6 shows an embodiment in which the cutout 5 in the side wall 30 of the reflector 3 is formed in an elliptical shape. Note that the basic configuration of the reflector 3 and the radiator 2 is the same as in the first embodiment, so a description is omitted (the same applies in the third embodiment). In this embodiment, the notch 5(53) is formed in an elliptical shape approximately in the center of the height H direction (see Figure 2) of the side wall 30 of the reflector 3, with a notch height H4 of approximately 0.32λ and a maximum depth D4 of approximately 0.02λ relative to the wavelength λ of the center frequency of the receiving band. In other words, a notch 53 is formed approximately in the center of the longitudinal direction of the side wall 30, with a height of 160 mm and a maximum depth of 10 mm from the end face of the side wall 30, and is approximately elliptical in shape. Third Embodiment

[0021] As shown in Figure 5, this third embodiment, in which the receiving antenna 1, which combines the radiator 2 and reflector 3 described above, is arranged in a vertical stack configuration with two stages in the vertical direction, is also suitably implemented. By vertically stacking the receiving antenna 1 in this way, the gain is approximately doubled. Figure 8 shows the change in electrical characteristics gain with and without the notch 5 in this third embodiment. It can be seen that with the notch 5, the gain of the present invention, shown by the solid line a, is about 0.9 dB higher than the conventional gain shown by the dashed line b.

[0022] As described above, with this planar antenna, even if the antenna is thin and has a slim shape, that is, even if the distance K between the radiator 2 and the reflector 3 is narrowed, it is possible to efficiently improve the gain by providing a notch 5 in the side wall 30 formed on the reflector 3 that corresponds to the wavelength of the receiving frequency.

[0023] 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 commonly performed by those skilled in the art, without departing from the technical idea. [Explanation of symbols]

[0024] 1 Receiving antenna 2. Radiator 3 reflector 30 side wall 4 cases 5 Notch 51. First notch (staircase-shaped) 51a End face of the first notch 52. Second notch (staircase-shaped) 53. Elliptical notch 6. Mounting brackets K Distance between radiator and reflector S Space H side wall height H2 Height of the first notch H3 Height of the second notch H4 height of elliptical cutout D. Depth of the side wall D2 Depth of the first notch D3 Depth of the second notch D4 Maximum depth of elliptical cutout

Claims

1. In a planar antenna equipped with a receiving antenna for terrestrial digital broadcasting enclosed in a roughly rectangular cube-shaped case, The receiving antenna is composed of a radiator and a reflector. The radiator is roughly rectangular in shape, and the reflector is roughly rectangular in shape, slightly larger than the radiator, and the distance between the radiator and the reflector is less than one-eighth of the wavelength of the center frequency of the receiving band. Two sides of the reflector have bent side walls formed on the side facing the radiator, and the depth of the side walls is shorter than the distance between the radiator and the reflector. Each of the two side walls is provided with a stepped notch on its end face, approximately in the center in the height direction, with dimensions corresponding to the wavelength of the receiving frequency, so as to form a space between the radiator and the side wall. A planar antenna characterized by [this feature].

2. The notches in the side wall of the reflector are formed in a stepped shape by a first notch and a second notch. The first notch is formed in a pair at the upper and lower positions approximately in the center of the height direction of the side wall, with each notch having a height of approximately 0.08λ and a depth of approximately 0.01λ. The second notch is formed between the upper and lower pair of first notches, with a height of approximately 0.16λ and a depth of approximately 0.01λ further from the end face of the first notch. A planar antenna as described in claim 1, characterized by the following:

3. The planar antenna according to claim 1, characterized in that the notch in the side wall of the reflector is formed in an elliptical shape approximately in the center of the height direction of the side wall, with a notch height of approximately 0.32λ and a maximum depth of approximately 0.02λ relative to the wavelength λ of the center frequency of the receiving band.

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