WO2008018230A1 - Antenna device - Google Patents

Abstract

Provided is an antenna device wherein antenna characteristics can be adjusted as desired. The antenna device is provided with a planar first radiation plate, which is one surface of a supporting substrate and has a feeding point facing the center of the supporting substrate; a transmitting line electrically connected to the feeding point; a planar second radiation plate, which faces the transmitting line and is arranged on the other surface of the supporting substrate so that the plate faces the transmitting line but not overlapping the position of the first radiation plate; and a notch formed at an outer end portion of the second radiation plate facing the transmitting line.

Description

 Specification

 Antenna device

 Technical field

 TECHNICAL FIELD [0001] The present invention relates to an antenna device, and more particularly to an antenna device for UWB (Ultra Wideband).

 Background art

 Conventionally, as an antenna device for UWB, a bowtie antenna in which a pair of radiation plates are arranged in a bowtie shape is known. Such a bow-tie antenna has a radiation plate with a self-similar shape and exhibits broadband characteristics. Further, as shown in FIG. 15, the present inventors have increased the number of resonance points by using a combination of radiation plates 51, 52 having different shapes in plan view in the antenna device 50 using a pair of radiation plates. It has been found that a wider band characteristic can be obtained. Further, as shown in FIG. 15, the radiation plates 51 and 52 are arranged on both sides of the support substrate 53, the transmission line 54 is connected to one radiation plate 51, and the other radiation plate 52 and the transmission line 54 are supported. It has also been found that by facing through the substrate 53, it can be used as an antenna element without separately connecting a transmission line to the other radiation plate 52.

 In this way, when at least one radiation plate 51, 52 is disposed on both surfaces of the support substrate 53, the other radiation plate 52 and the transmission line 54 constitute a microstrip line. . On the other hand, as an antenna device for UWB using a coplanar waveguide, for example, an antenna device 60 using the technique described in Patent Document 1 can be cited (see FIG. 14). In this antenna device 60, the radiation plate 62, the central conductor 63, and the ground conductor 64 are arranged on one surface of the support substrate 61, and the distance between the central conductor 63 and the ground conductor 64 increases almost monotonously as the radiation plate 62 is approached. Come on! / According to such an antenna device 60, impedance matching can be achieved by changing the distance between the center conductor 63 and the ground conductor 64 almost monotonously.

 Patent Document 1: Japanese Unexamined Patent Application Publication No. 2006-121643

Disclosure of the invention Problems to be solved by the invention

 However, even with the antenna device 60 described in Patent Document 1, there is a problem in that there is a frequency region where the antenna characteristics are not good depending on the shape of the radiation plate. In other words, as shown in Fig. 3, the return loss in the frequency region around 3 to 6 GHz cannot be reduced, so the antenna characteristics cannot be adjusted and the application of the antenna device is limited. It was.

 [0005] The present invention has been made in view of these points, and an object thereof is to provide an antenna device that can be adjusted to desired antenna characteristics.

 Means for solving the problem

[0006] In order to solve the above-described problem, the invention according to claim 1 provides an antenna device comprising:

 A planar first radiation plate disposed on one surface of the support substrate with the feeding point facing the center;

 A transmission line electrically connected to the feed point;

 A planar second radiation plate disposed opposite to the transmission line and on the other surface of the support substrate at a position that does not overlap the first radiation plate in the thickness direction;

 A notch formed at a position overlapping the transmission line in the thickness direction of the support substrate at the outer edge portion of the second radiation plate;

 It is characterized by providing.

[0007] The invention according to claim 2 is the antenna device according to claim 1,

 The portion on the first radiation plate side of the outer edge portion of the second radiation plate is formed along a curve that increases the distance from the first radiation plate toward the end. And

[0008] The invention described in claim 3 is the antenna device described in claim 1 or 2,

 The curve is an elliptic curve.

[0009] The invention according to claim 4 is the antenna device according to any one of claims 1 to 3, wherein The first radiation plate side of the outer edge portion of the second radiation plate is formed along a curved line continuous with the notch.

[0010] The invention described in claim 5 is directed to the antenna device described in any one of claims 1 to 4, further comprising:

 The notch is formed in a shape that expands toward the first radiation plate.

 [0011] The invention described in claim 6 is directed to the antenna device described in any one of claims 1 to 5, wherein

 The outer edge portion of the first radiation plate has a portion that is formed in an arc shape that protrudes toward the center of the support substrate.

[0012] The invention according to claim 7 is the antenna device according to any one of claims 1 to 6, wherein

 The notch side of the outer edge portion of the first radiation plate is formed along the shape of the notch! It is characterized by having a scooping part.

[0013] The invention of claim 8 is

 A planar radiating plate disposed on one surface of the support substrate with the feeding point facing the center;

 A central conductor electrically connected to the feed point;

 An antenna device comprising a pair of ground conductors arranged at a certain distance on both sides of the central conductor, and

 The distance between the center conductor and the ground conductor increases almost monotonously as it approaches the radiation plate,

 A portion of the outer edge portion of the ground conductor on the radiation plate side is formed along a curve such that the distance from the radiation plate increases as the distance from the center conductor increases.

 The invention's effect

[0014] According to the invention described in claim 1, the transmission line and the second radiation plate are opposed to each other via the support substrate, thereby functioning as a microstrip line! / . In addition, by forming a notch at the outer edge of the second radiation plate and overlapping the transmission line in the thickness direction of the support substrate, a sudden change in impedance is avoided, and the antenna characteristics are improved. Characteristics can be obtained.

 [0015] According to the invention described in claim 2, the distance of the outer edge portion of the second radiation plate on the first radiation plate side from the first radiation plate increases toward the end. Since it is formed along an open curve, the distance between the first radiation plate and the second radiation plate can be changed gently to avoid a sudden change in impedance and improve the antenna characteristics.

 [0016] According to the invention of claim 3, the portion of the outer peripheral portion of the second radiation plate on the first radiation plate side is

 Since it is formed along an elliptic curve that increases the distance from the first radiation plate as it is directed toward the end, the impedance is rapidly changed by slowly changing the distance between the first radiation plate and the second radiation plate. It is possible to avoid such a change, improve the antenna characteristics, and simplify the shape of the second radiation plate.

[0017] According to the invention of claim 4, the first radiating plate side of the outer edge portion of the second radiating plate is formed along a curve continuous with the notch, so that the impedance is reduced. Antenna characteristics can be improved by avoiding sudden changes.

[0018] According to the invention described in claim 5, since the notch is formed in a shape that expands toward the first radiation plate, the antenna can be avoided by avoiding a sudden change in impedance. The characteristics can be improved.

According to the invention described in claim 6, the outer edge portion of the first radiation plate has a portion formed in an arc shape that protrudes toward the center of the support substrate. Antenna characteristics can be improved by avoiding drastic changes.

[0020] According to the invention of claim 7, the outer edge portion of the first radiation plate has a portion formed along the shape of the notch, so that the notch of the second radiation plate Antenna characteristics can be improved by avoiding sudden changes in impedance due to sudden changes in the distance between the part and the first radiation plate.

[0021] According to the invention of claim 8, the radiation plate, the center conductor, and the ground conductor are arranged on one surface of the support substrate, and the distance between the ground conductor and the center conductor is close to the radiation plate. The distance between the radiation plate and the ground conductor increases as the distance from the radiation plate to the radiating plate side of the outer edge of the ground conductor increases along the curve. Antenna characteristics can be improved by avoiding sudden changes in impedance due to sudden changes.

 Brief Description of Drawings

 FIG. 1 is a perspective view showing an antenna device according to a first embodiment.

 FIG. 2 is a plan view showing the antenna device according to the first embodiment.

 FIG. 3 is a graph showing antenna characteristics of the antenna device according to the first embodiment.

 FIG. 4 is a graph showing the adjustment result of the maximum width dimension of the cut in the X direction.

 FIG. 5 is a graph showing the adjustment result of the maximum width dimension of the cut in the X direction.

 FIG. 6 is a graph showing the adjustment result of the maximum width dimension in the Z direction of the cut.

 FIG. 7 is a plan view showing an antenna apparatus according to a second embodiment.

 FIG. 8 is a plan view showing a modification of the radiation plate of the antenna device according to the second embodiment.

 FIG. 9 is a graph showing antenna characteristics of the antenna device according to the second embodiment.

 FIG. 10 is a diagram showing a radiation pattern of the antenna device according to the second embodiment.

 FIG. 11 is a plan view showing a modification of the radiation plate of the antenna device according to the second embodiment.

 FIG. 12 is a plan view showing a modification of the radiation plate of the antenna device according to the second embodiment.

 FIG. 13 is a perspective view showing an antenna apparatus according to a third embodiment.

 FIG. 14 is a perspective view showing a conventional antenna device.

 FIG. 15 is a perspective view showing a conventional antenna device.

 Explanation of symbols

[0023] 1, 20, 30 Antenna device

 2 Support substrate

 3, 21 1st radiation plate

 4 Feed point

 5 Transmission line

 6, 25 Second radiation plate

7, 26 Upper side 9 Bottom side

 31 Radiation plate

 32 Center conductor

 33 Ground conductor

 34 Taper

 BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of an antenna device according to the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

 [First embodiment]

 As shown in FIG. 1, the antenna device 1 of the present embodiment includes a flat support substrate 2. As the support substrate 2, conventionally used insulating materials such as Teflon (registered trademark), glass epoxy, FR-4, and silicon can be used as appropriate. In this embodiment, it is assumed that the support substrate 2 formed with a thickness of 0.6 mm by Teflon (registered trademark) having a dielectric constant ε = 2.2 is used.

A planar first radiation plate 3 is provided on one surface of the support substrate 2. The first radiation plate 3 is formed in a thin film shape from a conductive material such as copper, aluminum, gold, silver, or platinum. The planar shape of the first radiation plate 3 is convex toward the center of the support substrate 2, and the apex portion thereof is a feeding point 4. From the viewpoint of electromagnetic wave transmission / reception efficiency, the outer edge portion of the first radiation plate 3 is preferably formed in an arc shape. That is, it is preferable that the first radiation plate 3 is formed along an arc shape that protrudes toward the center of the support substrate 2. The arc preferably has a curvature radius of about 8 to 15 mm or an elliptic curve. As shown in FIG. 2, in this embodiment, the first radiation plate 3 has a shape along an elliptic curve with a semi-major axis r = 15 mm and a semi-minor axis r = 9 mm.

 zl xl

 And The portion of the outer edge of the first radiation plate 3 that connects the ends of the shape along the elliptic curve corresponds to the minor axis of the elliptic curve, and is substantially parallel to the edge of the support substrate 2. Here, the direction substantially parallel to the semi-minor axis!: Of the first radiation plate 3 is defined as the X-axis direction. In addition, the first radiation plate 3

 xl

 The direction that is substantially parallel to the semi-major axis r is the Z-axis direction. The thickness direction of the support substrate 2 is set to the Y axis zl

The direction. [0026] One end of the transmission line 5 is electrically connected to the feeding point 4 along the Z-axis direction. Although there is no restriction on the method of electrical connection, in the present embodiment, the first radiation plate 3 and the transmission line 5 are arranged on one surface of the support substrate 2, so that they are connected to the outer edge portion of the first radiation plate 3. By simply forming a thin-film transmission line 5 to be electrically connected, electrical connection is established. The width dimension of the transmission line 5 is not particularly limited, but the optimum value is determined by the thickness of the support substrate 2 and the dielectric constant.In this embodiment, the width dimension is 1.6 mm, and the characteristic impedance is A 50 Ω transmission line! /

 On the other surface of the support substrate 2, a planar second radiation plate 6 is provided at a position facing the transmission line 5 and not overlapping the first radiation plate 3 in the Y-axis direction. As shown in FIG. 2, an upper side portion 7 is provided along the X-axis direction on the first radiation plate 3 side of the outer edge portion of the second radiation plate 6. Side portions 8 and 8 that are substantially parallel to the Z-axis direction are provided at both ends of the upper side portion 7 at the outer edge portion of the second radiation plate 6. Further, a lower side portion 9 connecting the other ends of the side side portions 8 is provided on the outer edge portion of the second radiation plate 6 so as to be positioned on the end edge of the support substrate 2. Here, in the drawings, what is provided on one surface of the support substrate 2 is indicated by a solid line, and what is provided on the other surface of the support substrate 2 is indicated by a broken line.

 [0028] A cutout 10 is formed in the upper side portion 7 at a position overlapping the transmission line 5 in the Y-axis direction. The shape of the notch 10 in plan view may be a straight line, a curved line, or a combination thereof without any particular limitation, but a shape that expands the power supply efficiency from the transmission line 5 toward the first radiation plate 3 is preferable. . The notch 10 of the present embodiment is formed by a straight line, forming an isosceles triangle! /

 The second radiation plate 6 is formed in a thin film shape using a conductive material in the same manner as the first radiation plate 3. There is no particular limitation on the gap in the Z-axis direction between the first radiation plate 3 and the second radiation plate 6, but the preferred range is determined by the shape of the radiation plate, etc.In this embodiment, it is Omm. Yes. That is, in the Z-axis direction, the apex of the convex outer edge portion of the first radiation plate 3 and the position of the upper side portion 7 of the second radiation plate 6 overlap. The outer dimensions of the second radiation plate 6 are preferably 10 to 22 mm for the upper side 7 and the lower side 9, and about 20 to 30 mm for the side 8, in the present embodiment, the upper side 7 and the lower side 9 are 18 mm, Side 8 is 20mm. In addition, let the maximum width dimension in the X-axis direction of the notch 10 be i and the maximum width dimension in the Z direction be i.

ab Then, i and i have optimum values determined by the dielectric constant and thickness of the support substrate 2 ab

 1S where i is 4 to 6 mm and i is 4 to 14 mm. In this embodiment, i = i

 a b a b

= 4mm.

 [0030] To the other end of the transmission line 5 and the center of the lower side portion 9, a signal processing device for transmitting and receiving an electrical signal from the antenna device 1 is connected (not shown). As described above, in the present embodiment, the transmission line 5 and the second radiation plate 6 overlap with each other via the support substrate 2 so that a microstrip line as a power supply unit that supplies power to the radiation plate is configured. It becomes. That is, the transmission line 5 functions as a strip conductor, and a part of the second radiation plate 6 functions as a ground conductor. In this embodiment, since the first radiator plate 3 and the second radiator plate 6 are unbalanced antennas having different planar shapes, a balanced-unbalanced conversion circuit and an impedance conversion circuit required for a balanced antenna are installed. It is not necessary to transmit and receive electrical signals via a microstrip line, which is an unbalanced line.

 [0031] The first radiating plate 3 and the second radiating plate 6 can be applied as long as they do not expand toward the center of the support substrate 2, but the first radiating plate 3 is used to improve the antenna characteristics. 3 and the second radiation plate 6 should have different shapes. In addition, the distance L1 from the feeding point 4 to the straight part of the first radiation plate 3 and the position force at which the notch 10 and the transmission line 5 intersect to the upper side 7 and the lower side 9 along the side 8 A shape different from the distance L2 is preferable. Since the resonance frequency of the antenna device 1 is determined by the length dimension of the path through which the current flows, the difference in the length dimensions LI and L2 increases the number of resonance points and provides a wider band antenna characteristic. The shape of the radiation plate is preferably axisymmetric with respect to the reference axis along the transmission line 5 in order to make the radiation pattern uniform.

 In the present embodiment, the radiation plate and the transmission line 5 form a metal layer on each surface of the support substrate 2. The metal layer may be formed by etching or the like, or may be formed by pattern printing using a conductive paint.

 Next, the operation of this embodiment will be described.

[0034] When the antenna device 1 transmits radio waves, current is transmitted to the first radiation plate 3 and the second radiation plate 6 via the transmission line 5 with a predetermined amplitude and phase based on an electrical signal from the signal processing device. Supplied. Specifically, as shown in Fig. 2, it is supplied to the feed point 4 via the transmission line 5. The incident current enters the first radiation plate 3, and the current flows along the outer edge portion of the first radiation plate 3 to the straight line portion. Further, when a current flows through the transmission line 5, the current also flows through the second radiation plate 6 at a position facing the transmission line 5. In this way, in the present embodiment, the second radiation plate 6 functions as a transmission line, so that the second radiation plate 6 is fed. The current incident on the second radiation plate 6 flows from the notch 10 to the lower side portion 9 along the outer edge portion of the second radiation plate 6. As described above, when current flows through the first radiation plate 3 and the second radiation plate 6, radio waves are transmitted from the antenna device 1.

 [0035] When the antenna device 1 receives a radio wave, when a radio wave of a predetermined frequency is received by each radiation plate, a voltage current having an amplitude and a phase corresponding to the received radio wave is transmitted from each radiation plate. Flowing into. Specifically, a current flows to the feeding point 4 along the outer edge portion of the first radiation plate 3 and enters the transmission line 5. In the case of the second radiation plate 6, a current flows from the lower side portion 9 to the notch 10 along the outer edge portion, and the current enters the position where the second radiation plate 6 overlaps the transmission line 5. The incident current is transmitted to the signal processing device and processed as an electrical signal.

 Next, the antenna characteristics of the antenna device 1 are shown by solid lines in FIG. Also, in FIG. 3, as a comparative example, the antenna characteristics of a conventional antenna device 50 (see FIG. 15) in which notches 10 are not provided in the second radiation plate 6 are shown on a surface of the support substrate 2 by a one-dotted line. The antenna characteristics of the antenna device 60 (see FIG. 14) to which the technique described in Patent Document 1 in which a metal layer such as a radiation plate is formed are shown by two-dot chain lines. Here, the feed line (microstrip line and coplanar waveguide) of each antenna device has a characteristic impedance of 50 Ω.

 [0037] One of the indicators of antenna characteristics is the return loss [dB] obtained from the ratio between the input voltage and the reflected voltage. The return loss is also called the reflection coefficient. The smaller the value, the better the matching as an antenna device. Generally, the range of the value less than 10 [dB] is used.

[0038] The antenna device 1 according to the present embodiment can reduce the return loss of 2 to 6 GHz as compared with the comparative example, and can use 3 to 9 GHz as a use band. Therefore, the powerful force that cannot be used for wireless UWB, etc., which focuses on 3-5 GHz with conventional antenna devices According to the present invention, 3-5 GHz is also used, and it can be used for wireless UWB, etc. is there. Here, the resonance frequency of the antenna device 1 is such that the 1Z2 wavelength of the resonance points Pl and P2 is determined in proportion to the distances Ll and L2. In addition, the 1Z2 wavelength of the resonance point P3 is determined in proportion to the distance L3 from the straight line portion of the first radiation plate 3 to the lower side portion 9 of the second radiation plate 6. And, as the difference between distances Ll, L2, and L3 increases, the frequency of the resonance point is dispersed, the return loss is wider, and it is preferable because it decreases in the frequency domain.

 [0040] Next, the change in antenna characteristics by adjusting the width dimension of the notch 10 of the present invention will be described. .

 [0041] First, Fig. 4 shows changes in antenna characteristics due to adjustment of i when i = 10 mm.

 b a

 As shown in Fig. 4, by adjusting i, the resonance points Pl and P2 at 3 to 5 GHz are returned.

 a

 It is possible to change the reduction rate of the run loss. That is, if i = 10mm, 3GHz

 b

 When emphasizing near, i is 4mm. When emphasizing near 5GHz, i is 6mm.

 a a

 Is preferred.

 FIG. 5 shows changes in the antenna characteristics due to adjustment of i when i = 12 mm. Figure

 b a

 As shown in Fig. 5, by adjusting i, as shown in Fig. 4, a common point P1 at 3-5GHz

 a

 , P2 return loss reduction rate can be changed. I = 12mm

 b

 I is 4 mm for emphasis around 3 GHz, i is 5.5 for emphasis near 5 GHz

 a a mm is preferred.

Further, FIG. 6 shows the change in antenna characteristics due to adjustment of i when i = 4 mm.

 a b

 As shown in Fig. 6, by adjusting i, the return loss of joint points P1 and P3 is changed.

 b

 You can make it. In other words, when i = 4 mm, place emphasis around 3 to 5 GHz.

 a

 I is 6 to 7 mm, and i is 4 to 5 mm when emphasizing over 7 GHz.

 b a

 [0044] Thus, by adjusting the length dimension of i and i, emphasis was placed on the desired band of use.

 a b

 An antenna device can be used.

[0045] As described above, according to the antenna device 1 of the present embodiment, the transmission line 5 and the second radiation plate 6 are opposed to each other with the support substrate 2 interposed therebetween, thereby functioning as a microstrip line. In addition, by forming a notch 10 at the outer edge of the second radiation plate 6 and overlapping the transmission line 5 in the Y-axis direction, antenna characteristics are improved by avoiding a sudden change in impedance, Broadband characteristics can be obtained. [0046] Further, since the outer edge portion of the first radiation plate 3 is formed along an elliptic curve that protrudes toward the center of the support substrate 2, the antenna characteristics are improved by avoiding a sudden change in impedance. Can be improved. Also, by making the first radiation plate 3 a shape along an elliptic curve rather than a semicircular shape in plan view, the width dimension in the X direction can be shortened while ensuring the length dimension of the current path L1. It is possible to downsize the antenna device 1 in the X-axis direction.

[Second Embodiment]

 Next, a second embodiment of the antenna device according to the present invention will be described focusing on differences from the first embodiment.

 As shown in FIG. 7, in the antenna device 20 according to the present embodiment, the outer edge portion of the first radiation plate 21 near the feeding point 4 is formed along the shape of the notch 22. That is, on the outer edge portion of the first radiation plate 21, there are a curved portion 23 along an elliptic curve that protrudes toward the center of the support substrate 2, and a straight portion 24 where a straight line intersecting from the curved portion 23 intersects. Are provided. The straight portion 24 is not particularly limited as long as it is convex toward the second radiation plate 25 so as to follow the shape of the notch 22, but in this embodiment isosceles triangle (dotted line in FIG. 7). The apex angle is arranged in the vicinity of the feeding point 4 so that the apex angle faces the second radiation plate 25 side. The height dimension t along the Z direction of the isosceles triangle and the bottom dimension along the X direction

 h

 The length t is a force that can be adjusted as appropriate.In this embodiment, t = 2.8 mm, t = 8.

 w w

It is 3mm. By forming the outer edge portion of the first radiation plate 21 in this way, the outer edge portion in the vicinity of the feeding point 4 can be formed into the notch 22 of the second radiation plate 25. Therefore, the distance between the first radiation plate 21 and the second radiation plate 25 can be gradually changed near the notch 22, and the antenna characteristics can be improved by avoiding a sudden change in impedance. .

Further, as shown in FIG. 7, the upper side portion 26 of the second radiation plate 25 is formed along a curve that increases the distance from the first radiation plate 3 toward the end portion thereof. That is, the portion other than the notch 22 in the upper side portion 26 is formed in an arc shape that protrudes toward the first radiation plate 21 side, and the distance from the first radiation plate 21 changes gently. . At this time, each of the curves forming the upper side portion 26 separated from the left and right around the notch 22 is an elliptic curve. The ellipse has a half major axis r of 15 mm and a half minor axis r of 10 mm z2 x2. The shape of the upper side portion 26 is not limited to the curve along the elliptic curve, and the elliptic curve is not limited to the shape in which the ellipse is arranged on the left and right of the notch 22. Therefore, as an example of the combination of the first radiation plate 21 and the second radiation plate 25 in a plan view, FIGS. 8A to 8F are given. In this way, if the upper side portion 26 is formed so that the distance from the first radiation plate 21 changes gradually, it is possible to avoid impedance changes abruptly, making impedance matching easy and improving antenna characteristics. is there.

 [0049] The antenna characteristics of the antenna device 20 according to the present embodiment are shown by solid lines in FIG. FIG. 9 shows the antenna characteristics of the antenna device 1 according to the first embodiment as a comparative example.

 [0050] As shown in FIG. 9, the upper side portion 26 of the second radiation plate 25 is formed along an elliptic curve that protrudes toward the first radiation plate 21, thereby returning the high frequency region (8 GHz or more). Loss can be greatly reduced. In addition, since a return loss of 3 to 8 GHz can be reduced as compared with the conventional antenna device 50 (see FIG. 3), a wider use band can be obtained.

 Next, FIGS. 10A and 10B show the radiation pattern of the antenna device 20 according to the present embodiment. As can be seen from FIG. 10, the radiation pattern of the antenna device 20 of the present embodiment is substantially the same as the radiation pattern of the conventional dipole antenna in both the XY plane and the ZY plane, and the directivity is not degraded.

 In addition, the side portion 8 in the present embodiment is a force that is a straight line parallel to the Z-axis direction in order to place the second radiation plate 25 on the support substrate 2, as shown in FIG. It may be formed along a curve continuous to an elliptic curve. In this way, if the side portion 8 is formed by a curve that continues to the upper side portion 26, a sudden change in the path of the current flowing through the second radiation plate 25 can be avoided, and the antenna characteristics can be further improved. It is possible to improve. On the other hand, if the side portion 8 is a straight line parallel to the Z-axis direction as shown in Fig. 7, the support substrate 2 can be downsized, and both the antenna characteristics can be improved and the antenna device 20 itself can be downsized. It is.

Further, as shown in FIG. 12, the upper side portion 26 of the antenna device 20 in the present embodiment may have a portion that forms a notch 22 along a continuous curve. In other words, the upper side portion 26 and the notch 22 have a right / left target shape with the reference axis along the transmission line 5 as the center, and each outer edge portion is formed by a curve along an elliptic curve. The ellipse The semi-minor axis r is 4 mm and the semi-minor axis r is 9 mm. Thus, notch 10 and upper side z3 x3

 By forming 7 along a continuous curve, the path of the current incident on the second radiation plate 6 can be changed gently, and the antenna characteristics can be improved. In addition, the antenna characteristics can be easily adjusted by changing the ellipse dimension and the curvature of the curve.

 As described above, according to the antenna device 20 of the present embodiment, the transmission line 5 and the second radiation plate 25 are opposed to each other with the support substrate 2 interposed therebetween, thereby functioning as a microstrip line. In addition, by forming the notch 22 at a position overlapping the transmission line 5 in the Y-axis direction of the outer edge portion of the second radiation plate 25, the antenna characteristics can be improved and the broadband characteristics can be obtained.

 [0055] In addition, the second radiation plate 25 has an upper side 2 so that the distance from the first radiation plate 21 changes gradually.

6 is provided, antenna characteristics can be improved by avoiding a sudden change in impedance due to a sudden change in the distance between the first radiation plate 21 and the second radiation plate 25.

[0056] When the upper side portion 26 of the outer edge portion of the second radiation plate 25 is formed along a curve continuous with the notch 22 as shown in FIG. 12, the second from the transmission line 5 via the notch 22 The current flows through the radiation plate 25 and the power supply efficiency can be improved immediately.

[0057] In addition, the outer edge portion of the first radiation plate 21 is formed in an arc shape convex toward the center of the support substrate 2! /, And has a curved portion 23 and a straight portion 24, so that the feeding point 4 It is possible to improve the power supply efficiency from

[0058] Further, since the outer edge portion of the first radiation plate 21 has a straight line portion 24 formed along the shape of the notch 22, the first radiation plate 21 enters the notch 22 in the Y-axis direction. It is possible to improve the antenna characteristics by avoiding a sudden change in the distance between the notch 22 of the second radiation plate 25 and the first radiation plate 21.

 [Third embodiment]

 Next, a third embodiment of the antenna device according to the present invention will be described focusing on differences from the first embodiment.

As shown in FIG. 13, the antenna device 30 of the present embodiment includes a support substrate 2 similar to that of the first embodiment. Also, one side of the support substrate 2 is fed to the center of the support substrate 2. A flat radiation plate 31 is arranged with the electric point 4 facing. The outer edge portion of the radiation plate 31 is formed along an elliptic curve that protrudes toward the center of the support substrate 2. The applicable range of the shape of the elliptic curve is the same as that of the first radiation plate 3 in the first embodiment. In this embodiment, the half major axis r is 15 mm and the half minor axis r is 9 mm.

 z4 z4

 [0060] A central conductor 32 that is electrically connected to the feed point 4 is connected to the outer edge portion of the radiation plate 31 near the feed point 4 along the Z-axis direction. The center conductor 32 is arranged in parallel with the Z-axis direction without changing its width dimension, and the other end coincides with the edge of the support substrate 2. In the present embodiment, the width dimension of the center conductor 32 in the X-axis direction is 1.6 mm.

 A pair of ground conductors 33 and 33 are arranged on both sides of the center conductor 32 so as to provide a distance between the center conductor 32. The ground conductor 33 has a symmetrical shape with the central conductor 32 as a reference axis, and the size thereof is substantially the same as that of the second radiation plate 6 in the first embodiment equally divided into two in the X-axis direction.

 [0062] The distance w between the ground conductor 33 and the center conductor 32 increases almost monotonously as the distance from the radiation plate 31 is approached. That is, in the present embodiment, by providing the tapered portion 34 in which the distance between the ground conductor 33 and the center conductor 32 monotonously increases, it is possible to function as the notch 10 of the first embodiment. . Accordingly, the distance w on both sides of the center conductor 32 is such that the width of the Z-axis direction is 4 mm and the inclination angle is 45 ° at the taper portion 34 while the bottom side force of the ground conductor 33 is maintained at 0.22 m.

 [0063] The portion on the radiation plate 31 side of the outer edge portion of the ground conductor 33 is formed along a curve such that the distance from the radiation plate 31 increases as the distance from the center conductor 32 increases. That is, in this embodiment, the outer edge portion of the ground conductor 33 facing the radiation plate 31 is formed along an elliptic curve, and the distance between the ground conductor 33 and the center conductor 32 is also along the elliptic curve. Change slowly. The diameter of the elliptic curve is the same as the curve forming the upper side portion 26 of the second radiation plate 25 in the second embodiment.

In the present embodiment, the radiation plate 31, the central conductor 32, and the round conductor 33 form a metal layer on one surface of the support substrate 2. This metal layer may be formed by etching or the like, or may be formed by pattern printing with a conductive paint. Yes.

 Here, as shown in FIG. 14, in the conventional antenna device 60 (see Patent Document 1), the radiation plate 62, the central conductor 63, and the ground conductor 64 are arranged on one surface of the support substrate 61. ing. Thus, when the central conductor 63 and the ground conductor 64 are formed on one surface of the support substrate 61 by etching or the like, if an error occurs in the size of both the central conductor 63 and the ground conductor 64, the central conductor 63 and the ground conductor 64 There is also an error in the distance w between and the desired antenna characteristics cannot be obtained. Because of these problems, precision is required for the distance w between the center conductor 63 and the ground conductor 64. However, the smaller the antenna device, the smaller the distance w and the more difficult it is to form accurately. There is also the problem of being.

 [0066] While the force is applied, the ground conductor 33 is formed so as to have a portion in which the distance from the radiation plate 31 gradually changes as in the antenna device 30 according to the present invention. Even if the above-mentioned problems occur due to the arrangement of the radiation plate 31 and other conductors, the antenna characteristics can be improved by avoiding a sudden change in impedance due to a sudden change in the path of the current flowing through the ground conductor 33. It is possible to improve. Further, by providing the ground conductor 33 with the taper portion 34, it is possible to further improve the antenna characteristics without causing a sudden change in the path of the current flowing through the ground conductor 33.

 [0067] As described above, according to the antenna device 30 according to the present embodiment, even if the radiation plate 31, the center conductor 32, and the ground conductor 33 are arranged on one surface of the support substrate 2, the tapered portion 34 is provided, Since the portion on the radiation plate 31 side of the outer edge portion of the ground conductor 33 is formed along a curve that protrudes toward the radiation plate 31 side, the antenna characteristics can be improved.

 In this embodiment, the outer edge portion of the ground conductor 33 facing the radiation plate 31 is formed along an elliptic curve, and the outer edge portion of the ground conductor 33 facing the center conductor 32 is formed by a straight line. The outer edge portion of these ground substrates may be formed with a continuous curve.

 [0069] Further, the shape of the radiation plate 31 may be formed so as to follow the shape of the tapered portion 34, similarly to the first radiation plate 21 in the second embodiment.

Claims

The scope of the claims  [1] A planar first radiation plate disposed on one surface of the support substrate with the feeding point facing the center,  A transmission line electrically connected to the feed point;  Opposite to the transmission line and on the other surface of the support substrate in the thickness direction, the first (1) a planar second radiation plate arranged at a position not overlapping with the radiation plate;  A notch formed at a position overlapping the transmission line in the thickness direction of the support substrate at the outer edge portion of the second radiation plate;  An antenna device comprising: [2] A portion on the first radiation plate side of an outer edge portion of the second radiation plate is formed along a curve that opens at a distance from the first radiation plate toward the end thereof. The antenna device according to claim 1, characterized by: [3] The antenna device according to claim 1 or 2, wherein the curve is an elliptic curve.  [4] The method according to any one of claims 1 to 3, wherein the first radiating plate side of the outer edge portion of the second radiating plate is formed along a curve continuous with the notch. The antenna device according to any one of the above items. [5] The antenna according to any one of claims 1 to 4, wherein the notch is formed in a shape expanding toward the first radiation plate. apparatus. 6. The outer edge portion of the first radiation plate has a portion formed in an arc shape that protrudes toward the center of the support substrate, according to any one of claims 1 to 5. Or the antenna device according to item 1. [7] The method according to any one of claims 1 to 6, wherein the notch side of the outer edge portion of the first radiation plate has a portion formed along the shape of the notch. either The antenna device according to item 1. [8] A planar radiating plate disposed on one surface of the support substrate with the feeding point facing the center, A central conductor electrically connected to the feed point; An antenna device comprising a pair of ground conductors arranged at a certain distance on both sides of the central conductor, and  The distance between the center conductor and the ground conductor increases almost monotonously as it approaches the radiation plate,  The antenna device according to claim 1, wherein a portion of the outer edge portion of the ground conductor on the radiation plate side is formed along a curve that increases a distance from the radiation plate as the distance from the central conductor increases.