Planar antenna

Abstract

To optimize the shape and the number of openings in a reflector of a planar antenna.SOLUTION: A planar antenna 3 is composed of a radiating element 10 consisting of a rectangular twin loop element, and a reflector 31 arranged behind and facing the radiating element 10. The reflector 31 is made into a rectangle by processing a metal plate, and five openings 31a are formed at regular intervals in the rectangular planar portion facing the radiating element 10, and bent portions 31b bent at approximately right angles toward the radiating element 10 are formed on both sides of the planar portion. The sides between the openings 31a are formed in a zigzag shape. This allows the width of the reflector 31 to be reduced.SELECTED DRAWING: Figure 13

Description

[Technical Field]

[0001] The present invention relates to a planar antenna having a reflector, and to a planar antenna suitable for receiving terrestrial digital television broadcasts. [Background technology]

[0002] Yagi antennas and planar antennas are known as conventional antennas for receiving terrestrial digital television broadcasts. Planar antennas generally have a thin case in which a planar antenna element is built into the case. Among these planar antennas, a conventional planar antenna with a reflector (see Patent Document 1) is known, in which a reflector is arranged on the back side of the antenna element.

[0003] The configuration of a planar antenna 100 fitted with a reflector disclosed in Patent Document 1 is shown in Figures 43(a), (b), and (c). Figure 43(a) is a front view of the conventional planar antenna 100 fitted with a reflector, Figure 43(b) is a rear view of the conventional planar antenna 100 fitted with a reflector, and Figure 43(c) is a side view of the conventional planar antenna 100 fitted with a reflector. As shown in these figures, a conventional planar antenna 100 with a reflector is composed of a front element 110, which is a radiating element made of a rectangular dual loop element, and a rear element 111, which is a reflector arranged behind and facing the front element 110.

[0004] Front element 110 is formed into a rectangle by processing a metal plate, and is composed of four sides that form a rectangular outer frame and two protrusions 112 formed horizontally approximately in the center. Opposing ends of protrusions 112 serve as feed points 113. Such front element 110 is a rectangular dual loop element that includes a square loop element that extends from protrusions 112 to the upper outer frame and protrusions 112, and a square loop element that extends from protrusions 112 to the lower outer frame and protrusions 112. Rear element 111 is made into a rectangular shape by processing a metal plate, and three gaps 117a, 117b, and 117c are formed in the rectangular portion facing front element 110. In addition, rising portions 116 that are bent at approximately right angles toward front element 110 are formed on both sides of the rectangular portion. The three gaps 117a, 117b, and 117c make it possible to improve the reflection characteristics of rear element 111. Two feed points 113 of the front element 110 are connected to feed lines 114, respectively, and power is fed from a feed section 115 to the ends of the two feed lines. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6668109 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a planar antenna in which the shape and number of openings provided in a reflector are optimized. [Means for solving the problem]

[0007] The planar antenna of the present invention, which can achieve the above-mentioned object, comprises a radiating element consisting of a loop element formed in a rectangular or triangular loop shape, and a reflector which is arranged facing the radiating element and spaced a predetermined distance behind it, and which has a planar portion facing the radiating element and bent portions on both sides of the planar portion bent toward the radiating element, and in which a plurality of openings are formed in the planar portion, and which is mainly characterized in that the openings formed in the reflector are rectangular in shape, and four of the openings are formed in the planar portion at predetermined intervals in the vertical direction. In the openings formed in the planar portion of the planar antenna of the present invention, the sides between the openings may be zigzag or wavy. Another planar antenna of the present invention that can achieve the above-mentioned object comprises: a first radiating element consisting of a loop element formed in a triangular loop; a second radiating element consisting of a loop element formed in a triangular loop, shaped symmetrically to the first radiating element and arranged vertically relative to the first radiating element; a reflector that faces the first radiating element and the second radiating element and is arranged rearward a predetermined distance away, facing the first radiating element and the second radiating element, and has bent portions on both sides of the planar portion that are bent toward the first radiating element and the second radiating element, and has a plurality of openings formed in the planar portion in the vertical direction at predetermined intervals, and is mainly characterized in that the sides between the openings formed in the planar portion are zigzag or wave-shaped.

[0008] In the above-described other planar antenna of the present invention, the number of the openings formed in the planar portion may be set to 2 to 9. In the above-described planar antenna of the present invention, the opening formed in the planar portion may not have an opening over a predetermined width in the central portion. [Effects of the Invention]

[0009] In the planar antenna of the present invention, the shape and number of openings in the reflector are optimized, which improves the characteristics. In addition, the sides between the openings are zigzag or wavy, which allows the size of the planar antenna to be reduced. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a front view showing the configuration of a planar antenna according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a rear view showing the configuration of the planar antenna according to the first embodiment of the present invention. [Figure 3] 1 is a top view showing the configuration of a planar antenna according to a first embodiment of the present invention. [Figure 4]1 is a side view showing the configuration of a planar antenna according to a first embodiment of the present invention. [Figure 5] 1 is a front view showing the configuration of a radiating element in a planar antenna according to a first embodiment of the present invention. [Figure 6] FIG. 2 is a front view showing the configuration of a reflector in the planar antenna according to the first embodiment of the present invention. [Figure 7] FIG. 10 is a front view showing the configuration of a planar antenna according to a second embodiment of the present invention. [Figure 8] FIG. 10 is a rear view showing the configuration of the planar antenna according to the second embodiment of the present invention. [Figure 9] FIG. 10 is a top view showing the configuration of a planar antenna according to a second embodiment of the present invention. [Figure 10] FIG. 10 is a side view showing the configuration of a planar antenna according to a second embodiment of the present invention. [Figure 11] FIG. 10 is a front view showing the configuration of a radiating element in a planar antenna according to a second embodiment of the present invention. [Figure 12] FIG. 10 is a front view showing the configuration of a reflector in a planar antenna according to a second embodiment of the present invention. [Figure 13] FIG. 10 is a front view showing the configuration of a planar antenna according to a third embodiment of the present invention. [Figure 14] FIG. 10 is a rear view showing the configuration of a planar antenna according to a third embodiment of the present invention. [Figure 15] FIG. 10 is a front view showing the configuration of a planar antenna according to a fourth embodiment of the present invention. [Figure 16] FIG. 10 is a rear view showing the configuration of a planar antenna according to a fourth embodiment of the present invention. [Figure 17] FIG. 10 is a front view showing the configuration of a reflector in a planar antenna according to a third or fourth embodiment of the present invention. [Figure 18] FIG. 10 is a bottom view showing the configuration of a reflector in the planar antenna according to the third and fourth embodiments of the present invention. [Figure 19] FIG. 10 is a front view showing the configuration of a planar antenna according to a fifth embodiment of the present invention. [Figure 20] FIG. 10 is a rear view showing the configuration of a planar antenna according to a fifth embodiment of the present invention. [Figure 21]FIG. 10 is a top view showing the configuration of a planar antenna according to a fifth embodiment of the present invention. [Figure 22] FIG. 10 is a side view showing the configuration of a planar antenna according to a fifth embodiment of the present invention. [Figure 23] 1 is a diagram showing the configuration of a power supply section in a planar antenna according to an embodiment of the present invention; [Figure 24] FIG. 10 is a front view showing the configuration of a radiating element in a planar antenna according to a fifth embodiment of the present invention. [Figure 25] 10A and 10B are a front view and a bottom view showing the configuration of a reflector in a planar antenna according to a fifth embodiment of the present invention. [Figure 26] FIG. 10 is a front view showing the configuration of a planar antenna according to a sixth embodiment of the present invention. [Figure 27] FIG. 10 is a rear view showing the configuration of a planar antenna according to a sixth embodiment of the present invention. [Figure 28] 10A and 10B are a front view and a bottom view showing the configuration of a reflector in a planar antenna according to a sixth embodiment of the present invention. [Figure 29] 13A and 13B are front views showing the configurations of first and second modified examples of a reflector in a planar antenna according to a sixth embodiment of the present invention. [Figure 30] FIG. 13 is a front view showing the configurations of third and fourth modified examples of the reflector in the planar antenna according to the sixth embodiment of the present invention. [Figure 31] FIG. 13 is a front view showing the configurations of fifth and sixth modified examples of the reflector in the planar antenna according to the sixth embodiment of the present invention. [Figure 32] 13 is a graph showing VSWR and VSWR evaluation values ​​when the reflector is one of the first to sixth modified examples in the planar antenna according to the sixth embodiment of the present invention. [Figure 33] 13A and 13B are a front view and a bottom view showing the configuration of a seventh modified example of a reflector in a planar antenna according to a sixth embodiment of the present invention, and a front view showing the configuration of a first reinforcing plate. [Figure 34] 10 is a graph showing VSWR and VSWR evaluation values ​​when the seventh modification of the reflector is used in the planar antenna according to the sixth embodiment of the present invention. [Figure 35] FIG. 13 is a front view showing the configurations of eighth and ninth modified examples of the reflector in the planar antenna according to the sixth embodiment of the present invention. [Figure 36] 13A and 13B are front views showing other configurations of tenth and eleventh examples of the reflector in the planar antenna according to the sixth embodiment of the present invention. [Figure 37] 13 is a graph showing VSWR and VSWR evaluation values ​​when the seventh to eleventh modified reflectors are used in the planar antenna according to the sixth embodiment of the present invention. [Figure 38] 10A and 10B are diagrams showing the configuration of a closing plate that can change the number and shape of openings in a reflector in a planar antenna according to a sixth embodiment of the present invention. [Figure 39] 10A and 10B are diagrams showing an example of the configuration in which the number and shape of openings are changed in a reflector in a planar antenna according to a sixth embodiment of the present invention. [Figure 40] 13 is a graph showing VSWR and VSWR evaluation values ​​when the radiating element is changed in the planar antenna according to the sixth embodiment of the present invention. [Figure 41] FIG. 13 is a front view showing the configuration of a planar antenna according to a seventh embodiment of the present invention. [Figure 42] FIG. 13 is a front view showing the configuration of a radiating element in a planar antenna according to a seventh embodiment of the present invention. [Figure 43] 1A to 1C are a front view, a rear view, and a side view showing the configuration of a conventional planar antenna 100 fitted with a reflector. DETAILED DESCRIPTION OF THE INVENTION

[0011] <Planar antenna according to the first embodiment of the present invention> A planar antenna 1 according to a first embodiment of the present invention is an antenna for receiving terrestrial digital television broadcasts, and its operating frequency band is 470 MHz to 710 MHz. The configuration of the planar antenna 1 according to the first embodiment is shown in Figs. 1 to 6. Fig. 1 is a front view of the planar antenna 1 according to the first embodiment, Fig. 2 is a rear view of the planar antenna 1 according to the first embodiment, Fig. 3 is a top view of the planar antenna 1 according to the first embodiment, Fig. 4 is a side view of the planar antenna 1 according to the first embodiment, Fig. 5 is a front view of a radiating element 10 of the planar antenna 1 according to the first embodiment, Fig. 6(a) is a front view of a reflector 11 of the planar antenna 1 according to the first embodiment, and Fig. 6(b) is a bottom view of the reflector 11 of the planar antenna 1 according to the first embodiment. As shown in these figures, the planar antenna 1 of the first embodiment is composed of a radiating element 10 made up of a rectangular twin loop element, and a reflector 11 arranged behind and facing the radiating element 10.

[0012] As shown in Fig. 5, the radiating element 10 is formed into a rectangular metal plate with two notches 10c formed at the top and bottom. It is composed of four sides (top, bottom, left, and right) that form the rectangular outer frame, and two feed elements 10a formed horizontally in the approximate center. Opposing ends of the two feed elements 10a form a feed point 10b. This radiating element 10 is a rectangular twin loop element consisting of two feed elements 10a and the upper half of the left side, the upper side, and the upper half of the right side, and another rectangular loop element consisting of two feed elements 10a and the lower half of the left side, the lower side, and the lower half of the right side. The reflector 11 is made by processing a metal plate into a rectangle, and as shown in Fig. 6, four openings 11a are formed vertically at predetermined intervals in the rectangular planar portion facing the radiating element 10. In addition, bent portions 11b are formed on both sides of the planar portion, which are bent at approximately right angles toward the radiating element 10. The four openings 11a all have the same perimeter length Lλ, and if the wavelength of the center frequency (590 MHz) of the frequency band being used is λ, then the perimeter length Lλ is approximately 1λ. The optimized number of openings 11a, four, makes it possible to improve the reflection characteristics of the reflector 11. Two feed points 10b of radiating element 10 are connected to feed lines 12, respectively, and power is fed to the ends of the two feed lines 12 from feed section 13.

[0013] The dimensions of each part of the planar antenna 1 of the first embodiment of the present invention will be explained below. The distance H1 between the radiating element 10 and the reflector 11 shown in Fig. 4 is approximately 45 mm, the height H2 of the bent portion 11b of the reflector 11 is approximately 30 mm, the width W1 of the radiating element 10 shown in Fig. 5 is approximately 220 mm, and the vertical length L1 is approximately 280 mm. The width W2 of the reflector 11 shown in Fig. 6 is approximately 240 mm, the vertical length L1 is approximately 280 mm, the width W3 of the opening 11a is approximately 200 mm, the vertical length L2 of the opening 11a is approximately 54 mm, and the width L3 of the side between the openings 11a is approximately 10 mm.

[0014] <Planar antenna according to a second embodiment of the present invention> A planar antenna 2 according to a second embodiment of the present invention is an antenna for receiving terrestrial digital television broadcasts, and operates in a frequency band of 470 MHz to 710 MHz. The configuration of the planar antenna 2 according to the second embodiment is shown in Figs. 7 to 12. Fig. 7 is a front view of the planar antenna 2 according to the second embodiment, Fig. 8 is a rear view of the planar antenna 2 according to the second embodiment, Fig. 9 is a top view of the planar antenna 2 according to the second embodiment, Fig. 10 is a side view of the planar antenna 2 according to the second embodiment, Fig. 11 is a front view of the radiating element 20 of the planar antenna 2 according to the second embodiment, Fig. 12(a) is a front view of the reflector 11 of the planar antenna 2 according to the second embodiment, and Fig. 12(b) is a bottom view of the reflector 11 of the planar antenna 2 according to the second embodiment. As shown in these figures, the planar antenna 2 of the second embodiment is a planar antenna in which the radiating element 10 of the planar antenna 1 of the first embodiment is replaced with the radiating element 20. That is, in the planar antenna 2 of the second embodiment, the radiating element 10 consisting of a rectangular twin loop element is replaced with the radiating element 20 consisting of a triangular twin loop element formed in a triangular loop shape, and the remaining configuration is the same as that of the planar antenna 1 of the first embodiment. The planar antenna 2 of the second embodiment is composed of the radiating element 20 consisting of a triangular twin loop element, and a reflector 11 arranged behind and facing the radiating element 20.

[0015] As shown in Figure 11, radiating element 20 is a rectangular metal plate with two triangular notches 20c formed at the top and bottom, and triangular notches formed on the left and right sides, creating a triangular loop shape. It consists of four sides: an upper and lower edge that form the outer frame of the triangular loop, and left and right edges that are defined as hypotenuses. The left edge that is defined as the hypotenuse consists of a hypotenuse that extends diagonally downward and right toward the center and a hypotenuse that extends diagonally upward and right toward the center. The right edge that is defined as the hypotenuse consists of a hypotenuse that extends diagonally downward and left toward the center and a hypotenuse that extends diagonally upward and left toward the center. The two hypotenuses on the left edge that extend diagonally downward and right toward the center are defined as feed elements 20a, and these two feed elements 20a and the top edge form a downward-facing triangular loop element. In addition, the two oblique sides on the left side extending diagonally upward to the right toward the center and the two oblique sides on the right side extending diagonally upward to the left toward the center are also feed elements 20a, and these two feed elements 20a and the bottom side form an upward-facing triangular loop element. The radiating element 20 in the planar antenna 2 of the second embodiment is a triangular twin loop element consisting of the two triangular loop elements described above, and the opposing vertices of the two opposing triangular loop elements are two feed points 20b. The reflector 11 is the same as the reflector 11 in the planar antenna 1 of the first embodiment, and therefore a detailed description thereof will be omitted, but as shown in Fig. 12, four openings 11a are formed in the vertical direction at predetermined intervals in the rectangular planar portion facing the radiating element 20. In addition, bent portions 11b are formed on both sides of the planar portion, which are bent at approximately right angles toward the radiating element 20. The four openings 11a all have the same perimeter length Lλ, and if the wavelength of the center frequency (590 MHz) of the frequency band being used is λ, then the perimeter length Lλ is approximately 1λ, and the optimized number of openings 11a, four, makes it possible to improve the reflection characteristics of the reflector 11. The two feed points 20b of the radiating element 20 are connected to feed lines 12, respectively, and power is fed to the ends of the two feed lines 12 from a feed section 13.

[0016] The dimensions of each part of the planar antenna 2 of the second embodiment of the present invention will be explained below. The distance H1 between the radiating element 20 and the reflector 11 shown in Fig. 10 is approximately 45 mm, the height H2 of the bent portion 11b of the reflector 11 is approximately 30 mm, the width W1 of the radiating element 20 shown in Fig. 11 is approximately 220 mm, and the vertical length L1 is approximately 280 mm. The width W2 of the reflector 11 shown in Fig. 12 is approximately 240 mm, the vertical length L1 is approximately 280 mm, the width W3 of the opening 11a is approximately 200 mm, the vertical length L2 of the opening 11a is approximately 54 mm, and the width L3 of the side between the openings 11a is approximately 10 mm.

[0017] <Planar antenna according to the third embodiment of the present invention> A planar antenna 3 according to a third embodiment of the present invention is an antenna for receiving terrestrial digital television broadcasts, and uses a frequency band of 470 MHz to 710 MHz. The configuration of the planar antenna 3 according to the third embodiment is shown in Figures 13, 14, 17, and 18. Figure 13 is a front view of the planar antenna 3 according to the third embodiment, Figure 14 is a rear view of the planar antenna 3 according to the third embodiment, Figure 17 is a front view of the reflector 31 of the planar antenna 3 according to the third embodiment, and Figure 18 is a bottom view of the reflector 31 of the planar antenna 3 according to the third embodiment. As shown in these figures, the planar antenna 3 of the third embodiment is composed of a radiating element 10 consisting of a rectangular dual loop element, and a reflector 31 arranged behind and facing the radiating element 10. The planar antenna 3 of the third embodiment is configured such that the reflector 31 has an opening 31a of a different shape instead of the reflector 11 of the planar antenna 1 of the first embodiment.

[0018] The radiating element 10 is the same as the radiating element 10 in the planar antenna 1 of the first embodiment, and therefore its description will be omitted. However, the radiating element 10 is a rectangular double loop element consisting of a rectangular loop element consisting of two feed elements 10a, the upper half of the left side, the upper side, and the upper half of the right side, and a rectangular loop element consisting of two feed elements 10a, the lower half of the left side, the lower side, and the lower half of the right side. The reflector 31 is formed by processing a metal plate into a rectangular shape. As shown in FIGS. 17 and 18, five openings 31a are formed at predetermined intervals in the rectangular planar portion facing the radiating element 10. Furthermore, bent portions 31b are formed on both sides of the planar portion, bending at approximately right angles toward the radiating element 10. The sides between the openings 31a are formed in a zigzag pattern. The three openings 31a except for the top and bottom openings 31a all have the same perimeter length Lλ. If the wavelength of the center frequency (590 MHz) of the operating frequency band is λ, the perimeter length Lλ is approximately 1λ. The sides between the openings 31a may be corrugated instead of zigzag. The top and bottom openings 31a are symmetrical with respect to the horizontal centerline of the reflector 31, and the opening 31a formed in the center is half-truncated along the horizontal centerline. By optimizing the number and shape of the openings 31a in this way, the reflection characteristics of the reflector 31 can be improved. Furthermore, the width of the reflector 31 can be reduced, and as a result, the width of the planar antenna 3 of the third preferred embodiment can be reduced, and therefore the dimensions of the planar antenna 3 can be made smaller. Two feed points 10b of radiating element 10 are connected to feed lines 12, respectively, and power is fed to the ends of the two feed lines 12 from feed section 13.

[0019] The dimensions of each part of the planar antenna 3 of the third embodiment of the present invention will be explained below. The width W4 of the planar antenna 3 shown in Fig. 14 is approximately 230 mm, the vertical length L1 is approximately 280 mm, the width W4 of the reflector 31 shown in Figs. 17 and 18 is approximately 230 mm, the vertical length L1 is approximately 280 mm, and the height H2 of the bent portion 31b is approximately 30 mm. The width W5 of the opening 31a is approximately 180 mm, the length L4 of the longest vertical part of the opening 31a is approximately 69.3 mm, the length L5 of the shortest vertical part of the opening 31a is approximately 34.6 mm, and the width D of the zigzag side between the openings 31a is approximately 10 mm. The width W1 of the radiating element 10 is approximately 220 mm, the vertical length L1 is approximately 280 mm, and although not shown, the distance H1 between the radiating element 10 and the reflector 31 is approximately 45 mm.

[0020] <Planar antenna according to the fourth embodiment of the present invention> A planar antenna 4 according to a fourth embodiment of the present invention is an antenna for receiving terrestrial digital television broadcasts, and uses a frequency band of 470 MHz to 710 MHz. The configuration of the planar antenna 4 according to the fourth embodiment is shown in Figures 15 and 16. Figure 15 is a front view of the planar antenna 4 according to the fourth embodiment, and Figure 16 is a rear view of the planar antenna 4 according to the fourth embodiment. As shown in these figures, the planar antenna 4 of the fourth embodiment is composed of a radiating element 20 consisting of a triangular twin loop element, and a reflector 31 arranged behind and facing the radiating element 20, and the planar antenna 4 of the fourth embodiment is configured with the radiating element 20 of the planar antenna 2 of the second embodiment instead of the radiating element 10 of the planar antenna 3 of the third embodiment. That is, in the planar antenna 4 of the fourth embodiment, the radiating element 10 consisting of a rectangular twin loop element is replaced with the radiating element 20 consisting of a triangular twin loop element formed in a triangular loop shape, and the remaining configuration is the same as that of the planar antenna 3 of the third embodiment.

[0021] The radiating element 20 is the same as the radiating element 20 in the planar antenna 2 of the second embodiment, and therefore its description will be omitted, but the radiating element 20 is a triangular double loop element consisting of two triangular loop elements: a downward triangular loop element formed by two feed elements 20a and the upper side, and an upward triangular loop element formed by two feed elements 20a and the lower side, and the opposing vertices of the two opposing triangular loop elements are two feeding points 20b. The reflector 31 is the same as the reflector 31 in the planar antenna 3 of the third embodiment, and therefore its description will be omitted. However, as shown in FIGS. 17 and 18 , five openings 31a are formed at predetermined intervals in a rectangular planar portion facing the radiating element 20. The sides between the openings 31a are formed in a zigzag pattern, and the three openings 31a except for the top and bottom openings 31a all have the same perimeter length Lλ. If the wavelength of the center frequency (590 MHz) of the operating frequency band is λ, the perimeter length Lλ is approximately 1λ. The sides between the openings 31a may be corrugated instead of zigzag. The top and bottom openings 31a are symmetrical with respect to the horizontal center line of the reflector 31, and the three openings 31a are half-truncated along the horizontal center line. By optimizing the number and shape of the openings 31a in this way, the reflection characteristics of the reflector 31 can be improved. Furthermore, the width of the reflector 31 can be reduced, and as a result, the width of the planar antenna 4 of the fourth preferred embodiment can be reduced, and the dimensions of the planar antenna 3 can be made smaller. The two feed points 20b of the radiating element 20 are connected to feed lines 12, respectively, and power is fed from a feeder 13 to the ends of the two feed lines 12.

[0022] 16, the width W4 of the planar antenna 4 is approximately 230 mm, the vertical length L1 is approximately 280 mm, the reflector 31 (see FIGS. 17 and 18) has a width W4 of approximately 230 mm, a vertical length L1 of approximately 280 mm, and a height H2 of the bent portion 31b of approximately 30 mm, the width W5 of the opening 31a is approximately 180 mm, the length L4 of the longest vertical portion of the opening 31a is approximately 69.3 mm, the length L5 of the shortest vertical portion of the opening 31a is approximately 34.6 mm, and the width D of the zigzag side between the openings 31a is approximately 10 mm. The width W1 of the radiating element 20 is approximately 220 mm, and the vertical length L1 is approximately 280 mm, and although not shown, the distance H1 between the radiating element 20 and the reflector 31 is approximately 45 mm.

[0023] <Planar antenna according to the fifth embodiment of the present invention> A planar antenna 5 according to a fifth embodiment of the present invention is an antenna with improved gain for receiving terrestrial digital television broadcasts, and operates in a frequency band of 470 MHz to 710 MHz. The configuration of the planar antenna 5 according to the fifth embodiment is shown in FIGS. 19 to 25. FIG. 19 is a front view of the planar antenna 5 according to the fifth embodiment, FIG. 20 is a rear view of the planar antenna 5 according to the fifth embodiment, FIG. 21 is a top view of the planar antenna 5 according to the fifth embodiment, FIG. 22 is a side view of the planar antenna 5 according to the fifth embodiment, FIG. 23 is an enlarged view of the feeder 55 of the planar antenna 5 according to the fifth embodiment, FIG. 24 is a front view of the radiating element 05 of the planar antenna 5 according to the fifth embodiment, FIG. 25(a) is a front view of the reflector 52 of the planar antenna 5 according to the fifth embodiment, and FIG. 25(b) is a bottom view of the reflector 52 of the planar antenna 5 according to the fifth embodiment. As shown in these figures, the planar antenna 5 of the fifth embodiment is composed of a radiating element 05 having a first radiating element 50 and a second radiating element 51 each consisting of a triangular double loop element, and a reflector 52 arranged behind and facing the radiating element 05.

[0024] The first radiating element 50 and the second radiating element 51, which are composed of triangular twin loop elements, provided in the radiating element 05 are similar to the radiating element 20 in the planar antenna 2 of the second embodiment, and therefore description thereof will be omitted. However, the first radiating element 50 is a triangular twin loop element consisting of two triangular loop elements: a downward triangular loop element formed by two first feed elements 50a and the upper side, and an upward triangular loop element formed by two first feed elements 50a and the lower side, with the opposing vertices of the two opposing triangular loop elements serving as two feed points 50b. The second radiating element 51 is a triangular twin loop element consisting of two triangular loop elements: a downward triangular loop element formed by two second feed elements 51a and the upper side, and an upward triangular loop element formed by two second feed elements 51a and the lower side, with the opposing vertices of the two opposing triangular loop elements serving as two feed points 51b. The reflector 52 is made from a metal plate and is formed into a vertically long rectangle, and has a rectangular planar portion facing the entire surface of the radiating element 05 as shown in Figures 19 and 20, and nine openings 52a are formed in the planar portion at predetermined intervals in the vertical direction as shown in Figures 25(a) and 25(b). In addition, on both sides of the planar portion, bent portions 52b are formed that are bent at approximately right angles toward the radiating element 05. The nine openings 52a all have the same perimeter length Lλ, and if the wavelength of the center frequency (590 MHz) of the frequency band being used is λ, then the perimeter length Lλ is approximately 1λ. The optimized number of nine openings 52a makes it possible to improve the reflection characteristics of the reflector 52.

[0025] One end of a feed line 53 is connected to each of the two feed points 50b of the first radiating element 50, and the other end of the feed line 53 is connected to each of the two feed points 51b of the second radiating element 51. A feed board 54 is provided at approximately the center of the feed line 53, and a feed section 55 is formed on the feed board 54. Power is fed from the feed section 55 to approximately the center of the two feed lines 53. The configuration of the feeder 55 is shown enlarged in Figure 23, with the approximate centers of the two feeder lines 53 connected to the upper surface of the feeder board 54 by soldering or the like. Opposing protrusions are formed approximately at the centers of the two feeder lines 53, with the shield of a coaxial cable 56 soldered to one protrusion of the feeder line 53 and the core of the coaxial cable 56 soldered to the other protrusion of the feeder line 53, so that the planar antenna 5 of the fifth embodiment is fed by the coaxial cable 56. The protrusion formed approximately at the center of the feeder line 53 allows the impedance of the feeder 55 to be adjusted. Adjustment plates 57 for adjusting the impedance of the feeder 55 are printed or attached to both sides of the surface of the feeder board 54. The adjustment plates 57 may be omitted.

[0026] 25(a) and 25(b), the width W2 of the reflector 52 is about 240 mm, the vertical length L6 is about 600 mm, the height H2 of the bent portion 52b is about 30 mm, the width of the opening 52a is about 180 mm, the vertical length L2 of the opening 52a is about 54 mm, and the width L3 of the side between the openings 52a is about 10 mm. The width W1 of each of the first radiating element 50 and the second radiating element 51 is about 220 mm, and the vertical length L1 of each of the first radiating element 50 and the second radiating element 51 is about 280 mm. The width W1 of the radiating element 50 is about 220 mm, and the vertical length L6 is about 600 mm, and the distance L8 between the first radiating element 50 and the second radiating element 51, which are arranged in the vertical direction, is about 40 mm. As shown in FIG. 23, the width W7 of the power supply board 54 is about 110 mm, the length L7 is about 30 mm, and the distance H1 between the radiating element 05 and the reflector 52 is about 45 mm. The radiating element 05 of the planar antenna 5 of the fifth embodiment has two radiating elements, a first radiating element 50 and a second radiating element 51, arranged in the vertical direction, thereby improving the gain of the planar antenna 5 of the fifth embodiment.

[0027] <Planar antenna according to the sixth embodiment of the present invention> A planar antenna 6 according to a sixth embodiment of the present invention is an antenna with improved gain for receiving terrestrial digital television broadcasts, and operates in the frequency band of 470 MHz to 710 MHz. The planar antenna 6 of the sixth embodiment is a planar antenna in which the reflector 52 in the planar antenna 5 of the fifth embodiment is replaced with a reflector 62 having a different configuration, and the configuration other than the reflector 62 is the same as that of the planar antenna 5 of the fifth embodiment. The configuration of the planar antenna 6 of the sixth embodiment is shown in Figures 26 to 28. Figure 26 is a front view of the planar antenna 6 of the sixth embodiment, Figure 27 is a rear view of the planar antenna 6 of the sixth embodiment, Figure 28(a) is a front view of the reflector 62 of the planar antenna 6 of the sixth embodiment, and Figure 28(b) is a bottom view of the reflector 62 of the planar antenna 6 of the sixth embodiment. As shown in these figures, the planar antenna 6 of the sixth embodiment is composed of a radiating element 05 having a first radiating element 50 and a second radiating element 51 each consisting of a triangular double loop element, and a reflector 62 arranged behind and facing the radiating element 05.

[0028] The configuration of the radiating element 05 is the same as that of the radiating element 05 of the planar antenna 5 of the fifth embodiment, and therefore a detailed description thereof will be omitted, but the first radiating element 50 and second radiating element 51, which are made up of triangular twin loop elements provided in the radiating element 05, are similar to the radiating element 20 in the planar antenna 2 of the second embodiment. The first radiating element 50 is a triangular twin loop element made up of two triangular loop elements: a downward triangular loop element formed by two first feed elements 50a and the upper side, and an upward triangular loop element formed by two first feed elements 50a and the lower side, and the opposing vertices of the two opposing triangular loop elements serve as two feed points 50b. In addition, the second radiating element 51 is a triangular double loop element consisting of two triangular loop elements: a downward triangular loop element connected to the two second feed elements 51a and the upper side, and an upward triangular loop element connected to the two second feed elements 51a and the lower side, and the opposing vertices of the two opposing triangular loop elements are two feeding points 51b. The reflector 62 is made from a metal plate and is formed into a vertically long rectangle, with a rectangular planar portion facing the entire surface of the radiating element 05. As shown in Figures 28(a) and 28(b), nine openings 62a are formed in the planar portion at predetermined intervals in the vertical direction. In addition, bent portions 62b are formed on both sides of the planar portion, bent at approximately right angles toward the radiating element 05 side. The sides between the openings 61a are formed in a zigzag pattern, and the nine openings 62a all have the same perimeter length Lλ. If the wavelength of the center frequency (590 MHz) of the frequency band being used is λ, the perimeter length Lλ is approximately 1λ. The sides between the openings 62a may be corrugated instead of zigzag. Small triangular openings are formed above the top opening 62a and below the bottom opening 62a because the sides between the openings 61a are formed in a zigzag pattern. By optimizing the number and shape of the openings 62a in this way, the reflection characteristics of the reflector 62 can be improved. Furthermore, the width of the reflector 62 can be reduced, thereby reducing the width of the planar antenna 6 of the sixth embodiment, thereby enabling the size of the planar antenna 6 to be reduced.

[0029] One end of a feed line 53 is connected to each of the two feed points 50b of the first radiating element 50, and the other end of the feed line 53 is connected to each of the two feed points 51b of the second radiating element 51. A feed board 54 is provided at approximately the center of the feed line 53, and a feed section 55 is formed on the feed board 54. Power is fed from the feed section 55 to approximately the center of the two feed lines 53. The feeder unit 55 has a configuration as shown in Fig. 23, with the approximate centers of the two feeder lines 53 connected to the upper surface of the feeder board 54 by soldering or the like. Opposing protrusions are formed approximately at the centers of the two feeder lines 53, with the shield of a coaxial cable 56 soldered to one of the protrusions of the feeder line 53 and the core of the coaxial cable 56 soldered to the other protrusion of the feeder line 53, and the planar antenna 6 of the sixth embodiment is fed by the coaxial cable 56. The protrusions allow the impedance of the feeder unit 55 to be adjusted. Adjustment plates 57 for adjusting the impedance of the feeder unit 55 are printed or attached to both sides of the surface of the feeder board 54. However, the adjustment plates 57 may be omitted.

[0030] Regarding the dimensions of each part of the planar antenna 6 of the sixth embodiment of the present invention, the width of the planar antenna 5 is approximately 230 mm and the vertical length is approximately 600 mm. As shown in Figures 28(a) and 28(b), the width W4 of the reflector 62 is approximately 230 mm, the vertical length L6 is approximately 600 mm, and the height H2 of the bent portion 62b is approximately 30 mm. The width of the opening 62a is approximately 180 mm, the length L9 of the longest vertical part of the opening 62a is approximately 69.3 mm, the length L10 of the shortest vertical part of the opening 62a is approximately 34.6 mm, and the width D of the zigzag side between the openings 62a is approximately 10 mm. The first radiating element 50 and the second radiating element 51 each have a width W1 of approximately 220 mm and a vertical length L1 of approximately 280 mm, the radiating element 05 has a width W1 of approximately 220 mm and a vertical length L6 of approximately 600 mm, and the distance L8 between the first radiating element 50 and the second radiating element 51 arranged in the vertical direction is approximately 40 mm. The feeder board 54 has a width W7 of approximately 110 mm and a vertical length L7 of approximately 30 mm, and the distance H1 between the radiating element 05 and the reflector 52 is approximately 45 mm. The radiating element 05 of the planar antenna 6 of the sixth embodiment has two radiating elements, a first radiating element 50 and a second radiating element 51, arranged in the vertical direction, thereby improving the gain of the planar antenna 6 of the sixth embodiment.

[0031] <Number of openings in reflector in planar antenna according to sixth embodiment of the present invention> As described above, the planar antenna 6 of the sixth embodiment of the present invention is composed of a radiating element 05 including a first radiating element 50 and a second radiating element 51 each consisting of a triangular twin loop element, and a reflector 62 arranged behind and facing the radiating element 05. As shown in FIG. 28 , nine openings 62a are formed at predetermined intervals on the planar portion of the reflector 62. Of the nine openings 62a, the central opening 62a is designated as the A5 opening. From the A5 opening upward, the opening 62a above the A5 opening is designated as the A4 opening, the opening 62a above that is designated as the A3 opening, the opening 62a above that is designated as the A2 opening, and the topmost opening 62a is designated as the A1 opening. From the A5 opening downward, the opening 62a below the A5 opening is designated as the A4 opening, the opening 62a below that is designated as the A3 opening, the opening 62a below that is designated as the A2 opening, and the bottommost opening 62a is designated as the A1 opening. The A1 openings through A4 openings, each consisting of two, are positioned symmetrically with respect to the horizontal center line of the reflector 62.

[0032] The number of openings 62a formed in the reflector 62 was changed to six, and the voltage standing wave ratio (VSWR) of the planar antenna 6 of the sixth preferred embodiment was measured in the operating frequency band of 470 MHz to 710 MHz. The number of openings 62a formed in the reflector 62 is set to six: 0, 2, 4, 6, 8, and 9. A predetermined number of openings 62a are formed vertically at positions symmetrical with respect to the horizontal center line of the reflector 62. The configurations of the reflector 62 when the number of openings 62a formed in the reflector 62 is six are shown in Figures 29 to 31. Figure 29(a) shows the configuration of a reflector 62-1 when the number of openings 62a formed in the reflector 62 is zero. As shown in this figure, no openings are formed in the planar portion of the reflector 62-1. Next, Figure 29(b) shows the configuration of a reflector 62-2 when the number of openings 62a formed in the reflector 62 is two. As shown in this figure, only two A1 openings are formed vertically at positions symmetrical with respect to the planar portion of the reflector 62-2. Next, Figure 30(a) shows the configuration of a reflector 62-3 when the number of openings 62a formed in the reflector 62 is four. As shown in this figure, four A1 openings and four A2 openings are formed in the vertical direction on the planar portion of the reflector 62-3, each at symmetrical positions. Next, FIG. 30(b) shows the configuration of a reflector 62-4 when the number of openings 62a formed in the reflector 62 is six. As shown in this figure, six A1 openings, six A2 openings, and six A3 openings are formed in the vertical direction on the planar portion of the reflector 62-4, each at symmetrical positions. Next, FIG. 31(a) shows the configuration of a reflector 62-5 when the number of openings 62a formed in the reflector 62 is eight. As shown in this figure, eight A1 openings, six A2 openings, six A3 openings, and six A4 openings are formed in the vertical direction on the planar portion of the reflector 62-5, each at symmetrical positions. Finally, FIG. 31(b) shows the configuration of a reflector 62-6 when the number of openings 62a formed in the reflector 62 is nine. The configuration of the reflector 62-6 is the same as the configuration of the reflector 62 shown in FIG. 28. As shown in this figure, eight openings, namely A1 openings, A2 openings, A3 openings, and A4 openings, are formed in the vertical direction at symmetrical positions on the planar portion of the reflector 62-6, and an A5 opening is formed in the center, for a total of nine openings 62a.

[0033] The configuration of reflector 62-1 shown in Figure 29(a) will be referred to as "no opening", the configuration of reflector 62-2 shown in Figure 29(b) will be referred to as "opening A1", the configuration of reflector 62-3 shown in Figure 30(a) will be referred to as "openings A1, A2", the configuration of reflector 62-4 shown in Figure 30(b) will be referred to as "openings A1, A2, A3", the configuration of reflector 62-5 shown in Figure 31(a) will be referred to as "openings A1, A2, A3, A4", and the configuration of reflector 62-6 shown in Figure 31(b) will be referred to as "openings A1, A2, A3, A4, A5". Fig. 32(a) shows a graph of VSWR in the operating frequency band when the reflector 62 in the planar antenna 6 of the sixth embodiment is configured as reflector 62-1 to reflector 62-6. Referring to Fig. 32(a), the horizontal axis is the frequency axis of 470 MHz to 710 MHz, and it can be seen that in the frequency band of 470 MHz to 560 MHz, the more openings 62a there are, the better the VSWR becomes. It can also be seen that in the frequency band of 650 MHz to 710 MHz, the more openings 62a there are, the better the VSWR tends to be.

[0034] Here, the VSWR evaluation value is defined as follows: VSWR evaluation value = (maximum VSWR value) x (total VSWR value for each frequency) The frequencies in the second term on the right-hand side are 470, 500, 530, 560, 590, 620, 650, 680, and 710 MHz. For example, in the planar antenna 6 of the sixth embodiment, when the reflector 62 is configured as reflector 62-1, the VSWR at 470 MHz is approximately 3.38, at 500 MHz it is approximately 2.05, at 530 MHz it is approximately 1.49, at 560 MHz it is approximately 1.53, at 590 MHz it is approximately 1.86, at 620 MHz it is approximately 2.07, at 650 MHz it is approximately 2.53, at 680 MHz it is approximately 2.48, and at 710 MHz it is approximately 2.34, and the sum of these values ​​is approximately 19.73, and when this is multiplied by the maximum VSWR value of 3.38, the VSWR evaluation value is approximately 66.74. Similarly, when the reflector 62 in the planar antenna 6 of the sixth embodiment is configured as reflector 62-2 to reflector 62-6, the VSWR evaluation value is approximately 61.00 when reflector 62-2 (opening A1) is used, approximately 47.90 when reflector 62-3 (openings A1 and A2) is used, approximately 44.24 when reflector 62-4 (openings A1, A2, and A3) is used, approximately 43.16 when reflector 62-5 (openings A1, A2, A3, and A4) is used, and approximately 46.18 when reflector 62-6 (openings A1, A2, A3, A4, and A5) is used. A graph of these calculated VSWR evaluation values ​​is shown in FIG. 32(b). In the graph of FIG. 32(b), the horizontal axis represents the cases where the reflector 62 is configured as reflector 62-1 to 62-6. 32(b), it can be seen that the more openings 62a formed in the reflector 62 in the planar antenna 6 of the sixth embodiment, the better the VSWR evaluation value. Here, assuming that the threshold for the VSWR evaluation value is 46.25, the VSWR evaluation value will be equal to or less than the threshold of 46.25 when the number of openings 62a formed in the reflector 62 is the reflector 62-4 (openings A1, A2, A3), the reflector 62-5 (openings A1, A2, A3, A4), and the reflector 62-6 (openings A1, A2, A3, A4, A5). The threshold value is satisfied when the number of openings 62a is six or more. Thus, in the planar antenna 6 of the sixth embodiment of the present invention, it is preferable that the number of openings 62a formed in the reflector 62 is six or more.

[0035] <Shape of the opening of the reflector in the planar antenna according to the sixth embodiment of the present invention> As described above, the planar antenna 6 of the sixth embodiment of the present invention is composed of a radiating element 05 including a first radiating element 50 and a second radiating element 51 each consisting of a triangular twin loop element, and a reflector 62 arranged behind and facing the radiating element 05. As shown in Fig. 28, nine identically shaped openings 62a are formed vertically at predetermined intervals on the planar portion of the reflector 62. Of the nine openings 62a, the central opening 62a is designated as the A5 opening, and going upward from the A5 opening, the opening 62a above the A5 opening is designated as the A4 opening, the opening 62a above that is designated as the A3 opening, the opening 62a above that is designated as the A2 opening, and the topmost opening 62a is designated as the A1 opening. Going downward from the A5 opening, the opening 62a below the A5 opening is designated as the A4 opening, the opening 62a below that is designated as the A3 opening, the opening 62a below that is designated as the A2 opening, and the bottommost opening 62a is designated as the A1 opening. The A1 openings to A4 openings, each of which is two in number, are arranged at positions symmetrical in the vertical direction with respect to the center line of the reflector 62 in the horizontal direction.

[0036] The shape of the openings 62a formed in the reflector 62 can be changed. The configuration of the reflector 62 when the shape of two of the A3 openings 62a is changed is shown in Figures 33(a) and 33(b) as reflector 65-1. As shown in these figures, the two A3 openings have openings of a predetermined width only on both sides. In other words, the opening is not formed in the center of the two A3 openings by a predetermined width W8. Figure 34(a) shows a graph of the VSWR frequency characteristics when the reflector 62 of the planar antenna 6 of the sixth embodiment is the reflector 65-1 and the predetermined width W8 of the two A3 openings is 40 mm, 70 mm, 110 mm, 140 mm, and 180 mm. In the graph of Figure 34(a), the horizontal axis represents the operating frequency band of 470 MHz to 710 MHz, and "110 mm (with plate)" indicates that the width L8 is 110 mm and an adjustment plate 57 is provided on the power supply unit 55. Referring to the graph in Figure 34(a), it can be seen that when the width W8 is set to 110 mm, good characteristics are obtained in the frequency band used, and when the width W8 is set to 110 mm and an adjustment plate 57 is provided, the best characteristics are obtained.

[0037] Next, Fig. 34(b) shows a graph of VSWR evaluation values ​​when the reflector 62 of the planar antenna 6 of the sixth embodiment is the reflector 65-1 and the predetermined width W8 of the two A3 openings is set to 40 mm, 70 mm, 110 mm, 140 mm, 180 mm, and 110 mm (with plate). In the graph of Fig. 34(b), the horizontal axis represents the predetermined width W8 of the A3 opening. Referring to the graph in Figure 34(b), it can be seen that a good VSWR evaluation value is obtained when the reflector 62 of the planar antenna 6 of the sixth embodiment is used as the reflector 65-1 and the predetermined width W8 of the A3 opening is 110 mm, and the best VSWR evaluation value is obtained when the width W8 is 110 mm and the adjustment plate 57 is provided. Here, assuming that the threshold for the VSWR evaluation value is 46.25, the VSWR evaluation value is below the threshold of 46.25 when the predetermined width W8 of the A3 opening is 40 mm to 110 mm, thereby satisfying the threshold. Thus, in the planar antenna 6 of the sixth embodiment of the present invention, when the shape of the A3 opening in the opening 62a formed in the reflector 62 is changed as shown in Figure 65-1, it is preferable to set the width W8 of the A3 opening to 40 mm to 110 mm. Here, one wavelength at a center frequency of 590 MHz in the operating frequency band of 470 MHz to 710 MHz is approximately 508.4 mm. If one wavelength of the center frequency of the frequency band in use is 1λ, then it is preferable that the predetermined width W8 of the central part of the opening 62a of the reflector 62 of the planar antenna 6 of the sixth embodiment where no opening is formed is approximately 0.08λ to approximately 0.216λ.

[0038] In the planar antenna 6 of the sixth embodiment, the shape of the openings 62a formed in the reflector 62 is not limited to the A3 opening, and the shapes of other openings can be changed. A reflector 62 with the A3 and A4 openings of the openings 62a changed in shape is designated as reflector 65-2 and its configuration is shown in FIG. 35(a). As shown in this figure, two of the A3 and A4 openings have openings of a predetermined width only on both sides. That is, two of the A3 and A4 openings do not have openings of a predetermined width in the center. Furthermore, a reflector 62 with the A3, A4, and A5 openings of the openings 62a changed in shape is designated as reflector 65-3 and its configuration is shown in FIG. 35(b). As shown in this figure, two of the A3 and A4 openings and the A5 opening have openings of a predetermined width only on both sides. That is, two of the A3 and A4 openings and the A5 opening do not have openings of a predetermined width in the center. Furthermore, the configuration of the reflector 62 in which the shapes of the A2, A3, A4, and A5 openings among the openings 62a are changed is shown in Figure 36(a), which is designated as reflector 65-4. As shown in this figure, the A2, A3, and A4 openings, two of each, and the A5 opening, have openings of a predetermined width only on both sides. In other words, the A2, A3, and A4 openings, two of each, and the A5 opening, do not have openings of a predetermined width in the center. Furthermore, the configuration of the reflector 62 in which the shapes of all openings 62a are changed is shown in Figure 36(b), which is designated as reflector 65-5. As shown in this figure, the A1, A2, A3, and A4 openings, two of each, and the A5 opening, have openings of a predetermined width only on both sides. In other words, the A1, A2, A3, and A4 openings, two of each, and the A5 opening, do not have openings of a predetermined width in the center.

[0039] The configuration of reflector 65-1 shown in Figure 33(a) will be referred to as the "A3 opening", the configuration of reflector 65-2 shown in Figure 35(a) will be referred to as the "A3, A4 opening", the configuration of reflector 65-3 shown in Figure 35(b) will be referred to as the "A3, A4, A5 opening", the configuration of reflector 65-4 shown in Figure 36(a) will be referred to as the "A2, A3, A4, A5 opening", and the configuration of reflector 65-5 shown in Figure 36(b) will be referred to as the "A1, A2, A3, A4, A5 opening". Fig. 37(a) shows a graph of VSWR in the operating frequency band when the shape of the opening 62a of the reflector 62 in the planar antenna 6 of the sixth embodiment is changed to form reflectors 65-1 to 65-5. Referring to Fig. 37(a), the horizontal axis is the frequency axis of 470 MHz to 710 MHz, and it can be seen that in the frequency band of 470 MHz to 560 MHz, reflector 65-1 (A3 opening) and reflector 65-2 (A3, A4 openings) provide good VSWR. It can also be seen that in the frequency band of 650 MHz to 710 MHz, reflectors 65-1 to 65-5 all exhibit substantially similar VSWR characteristics.

[0040] Next, Fig. 37(b) shows a graph of VSWR evaluation values ​​when the shape of the opening 62a of the reflector 62 in the planar antenna 6 of the sixth embodiment is changed to reflectors 65-1 to 65-5. In the graph of Fig. 37(b), the horizontal axis represents the cases when the configuration of the reflector 62 is changed to reflectors 65-1 to 65-5. 37(b), when the reflector 62 in the planar antenna 6 of the sixth embodiment is replaced by the reflector 65-1 (A3 opening), the VSWR evaluation value is approximately 42.2, when the reflector 65-2 (A3, A4 opening) is used, the VSWR evaluation value is approximately 44.7, when the reflector 65-3 (A3, A4, A5 opening) is used, the VSWR evaluation value is approximately 47.4, when the reflector 65-4 (A2, A3, A4, A5 opening) is used, the VSWR evaluation value is approximately 50.3, and when the reflector 65-5 (A1, A2, A3, A4, A5 opening) is used, the VSWR evaluation value is approximately 49.8. Thus, it can be seen that the best VSWR evaluation value is obtained when the reflector 62 in the planar antenna 6 of the sixth embodiment is replaced by the reflector 65-1 (A3 opening). Here, assuming that the threshold value for the VSWR evaluation value is 46.25, the VSWR evaluation value becomes equal to or less than the threshold value of 46.25 when the reflector 62 is configured as the reflector 65-1 (A3 opening) and the reflector 65-2 (A3, A4 openings), and it can be seen that the threshold is satisfied. As such, it is preferable that the number of openings that change the shape of the opening 62a of the reflector 62 be four or less. In this case, when one wavelength of the center frequency of the frequency band being used is 1λ, it is preferable that the predetermined width W8 of the central portion of the opening 62a of the reflector 62 where no opening is formed be approximately 0.08λ to approximately 0.216λ.

[0041] <Number and shape of openings in reflector of planar antenna according to the sixth embodiment of the present invention> In the above description, when the number of openings 62a in the reflector 62 in the planar antenna 6 of the sixth embodiment is changed, the number of openings 62a to be formed is changed. Alternatively, in the reflector 62 having nine openings 62a formed at predetermined intervals as shown in Fig. 24(a), the number of openings 62a in the reflector 62 may be changed by closing the openings 62a at predetermined positions with closing plates. The configuration of the first closing plate 58a used in this case is shown in FIG. 38(a), and the configuration of the second closing plate 58b is shown in FIG. 38(b). The first closing plate 58a shown in Fig. 38(a) has a width of W5 and is shaped to cover the A1, A3, and A5 openings and the sides between the openings. The second closing plate 58b shown in Fig. 38(b) has a width of W5 and is shaped to cover the A2 and A4 openings and the sides between the openings.

[0042] As an example of changing the number of openings 62a in the reflector 62 in the planar antenna 6 of the sixth embodiment, Figure 39(a) shows the configuration of a reflector 62-4' in which a first closing plate 58a and a second closing plate 58b are provided to the reflector 62 shown in Figure 24(a) to realize a reflector with the same number of openings 62a as the reflector 62-4 shown in Figure 30(b). 39(a), in the openings 62a of the reflector 62 shown in Fig. 24(a), a first closing plate 58a is fixed by adhesive or screwing to the surface of the reflector 62 so as to close the A5 opening, and two second closing plates 58b are fixed by adhesive or screwing to the back surface of the reflector 62 so as to close the two A4 openings, respectively. This makes it possible to obtain a reflector 62-4' having six openings 62a, the same number as the reflector 62-4.

[0043] In the above description, when the shape of the opening 62a of the reflector 62 in the planar antenna 6 of the sixth embodiment is changed, the shape of the opening 62a to be formed is changed. Alternatively, in the reflector 62 having nine openings 62a formed at predetermined intervals as shown in Figures 24(a) and 24(b), the shape of the opening 62a of the reflector 62 may be changed by closing a predetermined range of the openings 62a at predetermined positions with a closing plate. The configuration of the third closing plate 67a used in this case is shown in FIG. 38(c), and the configuration of the fourth closing plate 67b is shown in FIG. 38(d). The third closing plate 67a shown in Fig. 38(c) has a width of W8 and is shaped to cover the predetermined width W8 at the center of the A1, A3, and A5 openings and to cover the sides between the openings. The fourth closing plate 67b shown in Fig. 38(d) has a width of W5 and is shaped to cover the predetermined width W8 at the center of the A2 and A4 openings and to cover the sides between the openings.

[0044] As an example of changing the shape of the opening 62a of the reflector 62 in the planar antenna 6 of the sixth embodiment, Figure 39(b) shows the configuration of a reflector 65-2' in which a third closing plate 67a and a fourth closing plate 67b are provided to the reflector 62 shown in Figure 24(a) to realize a reflector with an opening 62a of the same shape as the reflector 65-2 shown in Figure 35(a). 39(b), in the openings 62a of the reflector 62 shown in Fig. 24(a), a third closing plate 67a is fixed by adhesive or screwing to the back surface of the reflector 62 so as to close a predetermined width W8 in the center portions of the two A3 openings, and two fourth closing plates 67b are fixed by adhesive or screwing to the front surface of the reflector 62 so as to close the predetermined width W8 in the center portions of the two A4 openings, respectively. This makes it possible to obtain a reflector 65-2' having openings 62a shaped similar to that of the reflector 65-2. It is preferable that the number of openings that change the shape of the opening 62a of the reflector 62 using the third closing plate 67a and the fourth closing plate 67b be four or less, and in this case, when one wavelength of the center frequency of the frequency band in use is 1λ, it is preferable that the predetermined width W8 of the third closing plate 67a and the fourth closing plate 67b be approximately 0.08λ to approximately 0.216λ.

[0045] <Planar antenna according to the seventh embodiment of the present invention> A planar antenna 7 according to a seventh embodiment of the present invention is an antenna with improved gain for receiving terrestrial digital television broadcasts, and operates in the frequency band of 470 MHz to 710 MHz. The planar antenna 7 of the seventh embodiment is a planar antenna in which the radiating element 05 in the planar antennas 5 and 6 of the fifth and sixth embodiments is replaced with a radiating element 07 having a different configuration, and the configuration excluding the radiating element is the same as that of the planar antennas 5 and 6 of the fifth and sixth embodiments. The configuration of the planar antenna 7 of the seventh embodiment is shown in Figures 40 and 41. Figure 40 is a front view of the planar antenna 7 of the seventh embodiment, and Figure 41 is a front view of the radiating element 07 of the planar antenna 7 of the seventh embodiment. As shown in these figures, the planar antenna 6 of the seventh embodiment is composed of a radiating element 07 having a first radiating element 70 and a second radiating element 71 each consisting of a triangular twin loop element, and a reflector 72 arranged behind and facing the radiating element 07. Note that in Figure 40, the reflector 72 is the reflector 62-1 shown in Figure 29(a), but it is also possible to use a reflector 52 having a rectangular opening 52a as shown in Figure 25(a) or a reflector 62 having openings 62a with multiple zigzag sides as shown in Figures 28(a)(b) and 33(a)(b). The reflector 72 is made by processing a metal plate into a vertically long rectangle, and has a rectangular planar portion that faces the entire surface of the radiating element 07, and bent portions 72b bent at approximately right angles toward the radiating element 07 on both sides of the planar portion.

[0046] The structure of the radiating element 07 will be described. The radiating element 07 is composed of a first radiating element 70 and a second radiating element 71 that is symmetrical to the first radiating element. As shown in FIGS. 40 and 41, the first radiating element 70 has two triangular notches formed on the top and bottom of a rectangular metal plate with their vertices facing each other, and trapezoidal notches formed on the left and right sides. The top and bottom sides are composed of a wide outer element 70a, a trapezoidal inner element 70b extending from the outer element 70a toward the center, and a narrow, dogleg-shaped slit 70d formed between the outer element 70a and the inner element 70b. The outer frame is composed of four sides: the top and bottom sides configured in this way, and the left and right sides configured of a first feed element 70c consisting of hypotenuses extending from the ends of the top and bottom sides and triangular elements connected to the hypotenuses. The triangular elements connected to the hypotenuses on the left and right sides, which are the first feed element 70c, have their bases forming the edges of the left and right sides, respectively, and their vertices face each other at the center. The hypotenuse extending diagonally downward and right toward the center of the left side is connected to another vertex of the triangular element that constitutes the left side, and the hypotenuse extending diagonally upward and right toward the center of the left side is connected to the remaining vertex of the triangular element that constitutes the left side. The hypotenuse extending diagonally downward and left toward the center of the right side is connected to the other vertex of the triangular element that constitutes the right side, and the hypotenuse extending diagonally upward and left toward the center of the right side is connected to the remaining vertex of the triangular element that constitutes the right side. A downward-facing triangular loop element is formed by the upper halves of the left and right sides configured as described above and the outer element 70a that forms the upper side, and an upward-facing triangular loop element is formed by the lower halves of the left and right sides configured as described above and the outer element 70a that forms the lower side. The first radiating element 70 in the planar antenna 7 of the seventh embodiment is a triangular dual loop element consisting of the two triangular loop elements described above, and the opposing vertices of the two opposing triangular loop elements are two feeding points 70e.

[0047] The second radiating element 71 has a symmetrical shape to the first radiating element 70, with its upper and lower edges made up of a wide outer element 71a and a trapezoidal inner element 71b connected to the outer element 71a at its center via a narrow, dogleg-shaped slit 71d and positioned inward from the outer element 71a. The outer frame is made up of four edges: the upper and lower edges, and the left and right edges made up of second feed elements 71c each consisting of a hypotenuse extending from the end of the upper and lower edges and a triangular element connected to the hypotenuse. The upper and lower edges, the upper halves of the left and right edges (second feed element 71c) and the outer element 71a (top edge) form a downward-facing triangular loop element, while the lower halves of the left and right edges (second feed element 71c) and the outer element 71a (bottom edge) form an upward-facing triangular loop element. The second radiating element 71 in the planar antenna 7 of the seventh embodiment is a triangular dual loop element consisting of the two triangular loop elements described above, and the opposing vertices of the two opposing triangular loop elements serve as two feeding points 71e. One end of a feed line 73 is connected to each of the two feed points 70e of the first radiating element 70, and the other end of the feed line 73 is connected to each of the two feed points 71e of the second radiating element 71. A feed board 74 is provided at approximately the center of the feed line 73, and a feed section 55 is formed on the feed board 74. Power is fed from the feed section 55 to approximately the center of the two feed lines 73.

[0048] The power feed unit 55 has the same configuration as shown in Fig. 23, with the approximate centers of the two power feed lines 73 connected to the upper surface of the power feed board 74 by soldering or the like. Opposing protrusions are formed approximately at the centers of the two power feed lines 73, with the shield of the coaxial cable 56 soldered to one protrusion of the power feed line 73 and the core of the coaxial cable 56 soldered to the other protrusion of the power feed line 73, so that the planar antenna 7 of the seventh embodiment is fed by the coaxial cable 56. The protrusions allow the impedance of the power feed unit 55 to be adjusted. Adjustment plates 57 for adjusting the impedance of the power feed unit 55 are printed or attached to both sides of the surface of the power feed board 74. However, the adjustment plates 57 may be omitted.

[0049] As described above, the reflector 72 in Fig. 40 is the reflector 62-1 shown in Fig. 29(a), but the reflector 52 shown in Fig. 25(a) or the reflector 62 shown in Fig. 28(a) or Fig. 33(a) can also be used. If the reflector 72 is the reflector 62, 65-1 shown in Fig. 28(a) or Fig. 33(a), the number and shape of the openings 62a can be optimized to improve the reflection characteristics of the reflector 72. Furthermore, the width of the reflector 72 can be reduced, which in turn reduces the width of the planar antenna 7 of the seventh embodiment, thereby enabling the size of the planar antenna 7 to be reduced.

[0050] 28(a)(b) and 33(a)(b) is used as the reflector 72, the width W4 of the planar antenna 7 of the seventh embodiment is about 230 mm and the vertical length L6 is about 600 mm, the width W4 of a of the reflector 72 is about 230 mm and the vertical length L6 is about 600 mm, and although not shown, the height H2 of the bent portion 72b of the reflector 72 is about 30 mm. The dimensions of each part of the planar antenna 7 of the seventh embodiment of the present invention will be described with reference to FIG. The width W1 of each of the first radiating element 70 and the second radiating element 71 (the width of the outer elements 70a, 71a) is approximately 220 mm, the vertical length L1 of each is approximately 280 mm, the vertical width L11 of the outer elements 70a, 71a is approximately 50 mm, the length W9 of the long sides of the trapezoidal inner elements 70b, 71b is approximately 168 mm, the length W10 of the short sides is approximately 110.8 mm, the vertical width L12 is approximately 30 mm, the width L13 of the slits 70d, 71d is approximately 5 mm, and the spacing W11 between the tips is approximately 50 mm.

[0051] The radiating element 07 has a width W1 of approximately 220 mm and a vertical length L6 of approximately 600 mm, and the distance L8 between the first radiating element 70 and the second radiating element 71 arranged in the vertical direction is approximately 40 mm. Although not shown, the feeder board 74 has a width W7 of approximately 110 mm and a vertical length L7 of approximately 30 mm, and the distance H1 between the radiating element 07 and the reflector 72 is approximately 45 mm. The opening 62a formed in the reflector 72 has a width of approximately 180 mm, a length L9 of the longest vertical part of the opening 62a of approximately 69.3 mm, a length L10 of the shortest vertical part of the opening 62a of approximately 34.6 mm, and a width D of the zigzag side between the openings 62a of approximately 10 mm. The radiating element 07 of the planar antenna 7 of the seventh embodiment has two radiating elements, a first radiating element 70 and a second radiating element 71, arranged in the vertical direction, thereby improving the gain of the planar antenna 7 of the seventh embodiment.

[0052] Next, Fig. 42(a) shows a graph of VSWR in the operating frequency band when the reflector 62 in the planar antenna 7 of the seventh embodiment is configured as reflector 65-1 and the width W8 is approximately 110 mm. In Fig. 42(a), the radiating element 05 is referred to as a Σ type for comparison, the radiating element 07 is referred to as a modified Σ type, and the modified Σ type with an adjustment plate 57 provided on the feed board 74 is referred to as a modified Σ type (with adjustment plate). Referring to Fig. 42(a), the horizontal axis is the frequency axis of 470 MHz to 710 MHz, and it can be seen that the VSWR is good across almost the entire frequency band from 470 MHz to 710 MHz when the radiating element is the radiating element 07 of the planar antenna 7 of the seventh embodiment, and the VSWR is particularly good when the adjustment plate 57 is provided on the feed board 74 between 590 MHz and 710 MHz.

[0053] 42(b) is a graph comparing the VSWR evaluation values ​​when the reflector 62 in the planar antenna 7 of the seventh embodiment is configured as reflector 65-1 and has a width W8 of approximately 110 mm with the Σ-type radiating element 05. In the graph of FIG. 42(b), the horizontal axis represents the cases of the Σ-type, modified Σ-type, and modified Σ-type (with adjustment plate). 42(b), when the radiating element is a Σ-type, the VSWR evaluation value is approximately 42.2, when the radiating element is a modified Σ-type, the VSWR evaluation value is approximately 28.8, and when the radiating element is a modified Σ-type (with adjustment plate), the VSWR evaluation value is approximately 24.67. Thus, it can be seen that the best VSWR evaluation value is achieved when the adjustment plate 57 is provided on the feeder board 74 in the modified Σ-type of the planar antenna 7 of the seventh embodiment. [Industrial Applicability]

[0054] In the planar antennas according to the embodiments of the present invention described above, the frequency band used is not limited to 470 MHz to 710 MHz, and other frequency bands may also be used. In the planar antenna according to the embodiment of the present invention described above, the threshold value of the VSWR evaluation value is set to 46.25, but this value is not limited to this and other values ​​may be used. When other values ​​are used as the threshold value, the predetermined width W8 of the central portion where no opening is formed and the predetermined width W8 of the closing plate are set to a length range that satisfies the threshold value. Furthermore, in the planar antenna of the embodiment of the present invention described above, the blocking plate is fixed to the front or back surface of the reflector by being glued or screwed, but this is not limited to this, and the blocking plate may be shaped so that it can fit into a specified width at the center, and the blocking plate may be fixed by fitting into a specified width at the center of the opening. Furthermore, the planar antenna according to the embodiment of the present invention described above can be housed in a thin rectangular parallelepiped case made of synthetic resin. [Explanation of symbols]

[0055] 1 planar antenna, 2 planar antenna, 3 planar antenna, 4 planar antenna, 5 planar antenna, 6 planar antenna, 7 planar antenna, 05 radiating element, 07 radiating element, 10 radiating element, 10a feeding element, 10b feeding point, 10c notch, 11 reflector, 11a opening, 11b bent portion, 12 feeding line, 13 feeding portion, 20 radiating element, 20a feeding element, 20b feeding point, 20c notch, 31 reflector, 31a opening, 31b bent portion, 50 first radiating element, 50a feeding element, 50b feeding point, 51 second radiating element, 51a feeding element, 51b feeding point, 52 reflector, 52a opening, 52b bent portion, 53 feeding line, 54 feeding board, 55 Feeding section, 56 coaxial cable, 57 adjustment plate, 58a first closing plate, 58b second closing plate, 61a opening, 62 reflecting plate, 62a opening, 62b bent section, 65 reflecting plate, 67a third closing plate, 67b fourth closing plate, 70 first radiating element, 70a outer element, 70b inner element, 70c first feeding element, 70d slit, 70e feeding point, 71 second radiating element, 71a outer element, 71b inner element, 71c second feeding element, 71d slit, 71e feeding point, 72 reflecting plate, 72b bent section, 73 feeding line, 74 feeding board, 100 planar antenna with reflector, 110 front element, 111 rear element, 112 protrusion, 113 feeding point, 114 Power supply line, 115 Power supply part, 116 Rising part, 117a Gap part, A1,A2,A3,A4,A5 Opening part

Claims

1. A radiating element comprising a loop element formed in a rectangular loop shape; a reflector disposed rearwardly and facing the radiating element at a predetermined distance, the reflector having a planar portion facing the radiating element and bent portions on both sides of the planar portion bent toward the radiating element, the planar portion having a plurality of openings formed therein; A planar antenna, characterized in that the opening formed in the reflector is rectangular in shape, and four of the openings are formed at predetermined intervals in the vertical direction on the planar portion.

2. 2. The planar antenna according to claim 1, wherein the radiating element is a rectangular twin loop element, has two feed elements extending from approximately the center of both opposing sides toward the center so as to face each other, and is fed from a feed section to two feed lines connected to the respective ends of the two feed elements.

3. A radiating element comprising a loop element formed in a triangular loop shape; a reflector disposed rearwardly and facing the radiating element at a predetermined distance, the reflector having a planar portion facing the radiating element and bent portions on both sides of the planar portion bent toward the radiating element, the planar portion having a plurality of openings formed therein; A planar antenna, characterized in that the opening formed in the reflector is rectangular in shape, and four of the openings are formed at predetermined intervals in the vertical direction on the planar portion.

4. 4. The planar antenna according to claim 3, wherein the radiating element is a triangular twin loop element, the vertices of the two opposing triangles are feed points, and power is fed from a feed section to two feed lines connected to each of the feed points.

5. 5. The planar antenna according to claim 1, wherein the openings formed in the planar portion have sides between the openings that are zigzag or wavy.

6. A first radiating element comprising a loop element formed in a triangular loop shape; A second radiating element is a loop element formed in a triangular loop shape, and is shaped symmetrically to the first radiating element and disposed vertically relative to the first radiating element; a reflector disposed rearwardly and facing the first radiating element and the second radiating element at a predetermined distance, the reflector having a planar portion facing the first radiating element and the second radiating element, and bent portions on both sides of the planar portion bent toward the first radiating element and the second radiating element, the reflector having a plurality of openings formed in the planar portion; A planar antenna, characterized in that the opening formed in the reflector is rectangular in shape, and nine of the openings are formed at predetermined intervals in the vertical direction on the planar portion.

7. 7. The planar antenna according to claim 6, wherein the first radiating element and the second radiating element are triangular twin loop elements, each of the vertices of the two opposing triangles being feed points, the planar antenna further comprises a feed board to which two first feed lines connected to the feed points of the first radiating element, respectively, and two second feed lines connected to the feed points of the second radiating element, respectively, are connected, and power is supplied to the first feed line and the second feed line from a feed section in the feed board.

8. A first radiating element comprising a loop element formed in a triangular loop shape; A second radiating element is a loop element formed in a triangular loop shape, and is shaped symmetrically to the first radiating element and disposed vertically relative to the first radiating element; a reflector disposed rearwardly of and facing the first radiating element and the second radiating element at a predetermined distance, the reflector having a planar portion facing the first radiating element and the second radiating element, and bent portions at both sides of the planar portion bent toward the first radiating element and the second radiating element, the reflector having a plurality of openings formed at predetermined intervals in a vertical direction in the planar portion; A planar antenna, characterized in that in the openings formed in the planar portion, sides between the openings are zigzag or wavy.

9. 9. The planar antenna according to claim 8, wherein the openings formed in the planar portion with sides between the openings being zigzag or wavy are formed vertically, one at a time, at symmetrical positions with respect to a horizontal center line of the planar portion.

10. The planar antenna according to claim 8, characterized in that the openings formed in the planar portion with sides between the openings being zigzag or wavy are formed in pairs in the vertical direction at symmetrical positions with respect to a horizontal center line of the planar portion.

11. 9. The planar antenna according to claim 8, characterized in that the openings formed in the planar portion with sides between the openings being zigzag or wavy are formed in threes in the vertical direction at symmetrical positions with respect to a horizontal center line of the planar portion.

12. 9. The planar antenna according to claim 8, characterized in that the openings formed in the planar portion with sides between the openings being zigzag or wavy are formed in groups of four vertically at symmetrical positions about a horizontal center line of the planar portion.

13. 9. The planar antenna according to claim 8, wherein the openings formed in the planar portion are arranged in a zigzag or wave shape such that nine openings are arranged in a vertical direction.

14. 9. The planar antenna according to claim 8, characterized in that, in the nine apertures formed vertically in the reflector with the sides between the apertures being zigzag or wavy, each of the apertures formed at a symmetrical position with respect to the horizontal center line of the planar portion has no opening formed within a predetermined width in the central portion.

15. 9. The planar antenna according to claim 8, characterized in that, in the nine apertures formed vertically in the reflector with the sides between the apertures being zigzag or wavy, in each pair of the apertures formed at positions symmetrical with respect to the horizontal center line of the planar portion, no opening is formed within a predetermined width in the central portion.

16. 9. The planar antenna according to claim 8, characterized in that, in the nine apertures formed vertically in the reflector with the sides between the apertures being zigzag or wavy, in each of the two apertures formed at symmetrical positions with respect to the horizontal center line of the planar portion and in the central aperture, no aperture is formed within a predetermined width of the central portion.

17. 9. The planar antenna according to claim 8, characterized in that, in the nine apertures formed vertically in the reflector with the sides between the apertures being zigzag or wavy, in each of the three apertures formed at symmetrical positions with respect to the horizontal center line of the planar portion and in the central aperture, no opening is formed within a predetermined width in the central portion.

18. The planar antenna according to claim 8, characterized in that in the nine openings formed vertically in the reflector, the sides between the openings are zigzag or wavy, and no opening is formed in a predetermined width in the center.

19. The planar antenna according to claim 8, characterized in that in the nine openings formed vertically in the reflector with the sides between the openings being zigzag or wavy, a predetermined width of the central portion of each of the openings, located symmetrically about the horizontal center line of the planar portion, is blocked by a blocking plate.

20. The planar antenna according to claim 8, characterized in that in the nine apertures formed vertically in the reflector with the sides between the apertures being zigzag or wavy, a predetermined width in the center of each of two of the apertures, which are symmetrical about the horizontal center line of the planar portion, is blocked by a blocking plate.

21. The planar antenna according to claim 8, characterized in that, in the nine openings formed vertically in the reflector with the sides between the openings being zigzag or wavy, two openings at symmetrical positions relative to the horizontal center line of the planar portion and a predetermined width of the center of the central opening are blocked by a blocking plate.

22. The planar antenna according to claim 8, characterized in that, of the nine openings formed vertically in the reflector with the sides between the openings being zigzag or wavy, three openings at symmetrical positions relative to the horizontal center line of the planar portion and a predetermined width of the center of the central opening are blocked by a blocking plate.

23. A planar antenna as described in any one of claims 14 to 18, characterized in that the predetermined width of the central portion where no opening is formed is approximately 0.08λ to approximately 0.216λ, where 1 wavelength of the center frequency of the frequency band used is 1λ.

24. The planar antenna according to any one of claims 19 to 22, characterized in that the predetermined width of the blocking plate is about 0.08λ to about 0.216λ, where 1λ is one wavelength of the center frequency of the frequency band used.

25. 23. The planar antenna according to claim 8, wherein the first radiating element and the second radiating element are triangular twin loop elements, each of the two opposing vertices of the triangle is a feed point, the planar antenna further comprises a feed substrate to which two first feed lines connected to the feed points of the first radiating element, respectively, and two second feed lines connected to the feed points of the second radiating element, respectively, are connected, and power is fed to the first feed line and the second feed line from a feed section in the feed substrate.

26. 26. The planar antenna according to claim 25, wherein an adjustment plate for adjusting impedance is formed on the power supply board.

27. 23. The planar antenna according to claim 8, wherein the first radiating element and the second radiating element are each a triangular twin loop element, and each of the triangular twin loop elements includes an outer element forming an upper side and a lower side, a feed element forming a triangle connecting both ends of the outer element, an inner element formed by extending from the outer element toward the center, the outer element, the feed element, and a slit formed between the outer element and the inner element.

28. 28. The planar antenna according to claim 27, further comprising a feed board to which two first feed lines connected to the feed points of the first radiating element, respectively, and two second feed lines connected to the feed points of the second radiating element, respectively, are connected, and power is supplied to the first feed line and the second feed line from a feed section in the feed board.

29. 29. The planar antenna according to claim 28, characterized in that an adjustment plate for adjusting impedance is formed on the power supply board.

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