JP2017005663A - Planar antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a planar antenna forming a single directivity pattern, enabling miniaturization and plain formation.SOLUTION: A planar antenna (1) includes a plurality of zeroth-order resonant metamaterial elements (10, 20) respectively including: bottom plates (11, 21) which are conductors of a tabular shape; flat plates (12, 22) disposed in a manner to face the bottom plates apart therefrom; and at least each one short-circuit part (13, 23) which short-circuits between the bottom plate and the flat plate. One of the plurality of metamaterial elements is configured as a feed element (10) having a feeding part connected to the flat plate to feed, whereas other metamaterial elements than the feed element are configured as passive elements (20) having passive parts (24) which make the flat plate short-circuited with the bottom plate. The feed element and the passive element are arranged along a beam radiation direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique for forming a unidirectional pattern of an antenna.

  Conventionally, as a small unidirectional antenna, a Yagi / Uda antenna is known in which a plurality of monopoles each acting as a feeding element, an induction element, and a reflection element are arranged (see Patent Document 1). The Yagi / Uda antenna forms unidirectionality in the forward direction by arranging an inductive element in front of the feed element and a reflective element in the rear.

JP 2001-189620 A

  However, each monopole composing the Yagi / Uda antenna needs to be about 1/4 wavelength of the operating frequency, and is not suitable for in-vehicle antennas that require further miniaturization and planarization. was there.

  The present invention has been made in view of these problems, and an object thereof is to provide a planar antenna that forms a unidirectional pattern that can be miniaturized and planarized.

  The planar antenna of the present invention includes a ground plate, a flat plate, and at least one short-circuit portion, and includes a plurality of metamaterial elements configured to perform zero-order resonance. The ground plane is a conductor formed in a plate shape, and the flat plate is a conductor disposed so as to be opposed to the ground plane. A short circuit part short-circuits between a ground plane and a flat plate. One of the plurality of metamaterial elements includes a power feeding element including a power feeding unit that is connected to a flat plate to feed power, and the metamaterial element other than the power feeding element includes a parasitic unit that short-circuits the flat plate to the ground plane. The feeding element and the parasitic element are arranged along the radiation direction of the beam. Note that a planar antenna with zero-order resonance can obtain the same characteristics as a monopole antenna.

  According to such a configuration, a unidirectional pattern equivalent to that of a Yagi / Uda antenna can be realized by a planar antenna that can be made smaller and more planar than a monopole antenna.

  In addition, the code | symbol in the parenthesis described in the claim shows the correspondence with the specific means as described in embodiment mentioned later as one aspect, Comprising: The technical scope of this invention is limited is not.

It is a perspective view of the planar antenna of a 1st embodiment. It is a figure which shows the structure of the planar antenna of 1st Embodiment, (a) is a top view, (b) is sectional drawing. It is a graph which shows the radiation characteristic of a planar antenna, (a) is a planar antenna of 1st Embodiment, (b) is a planar antenna comprised only by the feed element which is a comparative example. It is a figure which shows the structure of the planar antenna of 2nd Embodiment, (a) is a top view, (b) is sectional drawing. It is a graph which shows the radiation | emission characteristic in the vertical plane of a planar antenna, (a) isolate | separates a ground plane, (b) shows the case where a ground plane is united. It is a top view which shows the structure of the planar antenna of 3rd Embodiment. It is a top view which shows the structure of the modification of 3rd Embodiment. It is a top view which shows the structure of other embodiment of a planar antenna.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
[1. First Embodiment]
[1.1. Constitution]
The planar antenna 1 of the present embodiment includes a first metamaterial element 10 and a second metamaterial element 20 as shown in FIGS. 1 and 2.

[1.2. First metamaterial element / feeding element]]
The first metamaterial element 10 includes a ground plane 11, a flat plate 12, a short-circuit portion 13, and a power feeding portion 14.

Each of the ground plane 11 and the flat plate 12 is made of a conductor formed in a rectangular plate shape, and both are spaced apart from each other.
The short-circuit portion 13 is formed of a cylindrical or columnar conductor that electrically connects the ground plane 11 and the flat plate 12 to short-circuit, and is disposed at the center of the flat plate 12.

  The power feeding unit 14 is connected between the ground plane 11 and the flat plate 12 and includes a power feeding conductor 141 and a power feeding circuit 142. The power supply conductor 141 is a conductor formed in a rod shape, and one end thereof is connected to the flat plate 12. The power supply circuit 142 has one end connected to the ground plane 11 and the other end connected to the flat plate 12 via the power supply conductor 141. The power feeding circuit 142 includes an oscillator, an amplifier circuit, an impedance matching circuit, and the like, and applies a high frequency signal between the ground plane 11 and the flat plate 12.

  The first metamaterial element 10 has a size of each part and a material used so that the first metamaterial element 10 becomes a zero-order resonator in which both the dielectric constant and the magnetic permeability are negative values and the order of the resonance mode is zero. Selected. In addition, since the structure method of the metamaterial element which carries out 0th order resonance is well-known, the description about the detail is abbreviate | omitted here. Hereinafter, the first metamaterial element 10 is referred to as a power feeding element 10.

  In the power supply element 10 configured as described above, a current flows through a current path from the power supply circuit 142 through the ground plane 11 and the short-circuit portion 13 to the flat plate 12. As a result, a vertical electric field is generated between the ground plane 11 and the flat plate 12, and radio waves are radiated from the end of the flat plate 12 in all directions along the plane of the flat plate 12. Further, the resonance frequency f of the power feeding element 10 has a relationship expressed by the equation (1), where L is an inductance component of the flat plate 12 and the short-circuit portion 23 and C is a capacitance component of the capacitor formed by the ground plane 11 and the flat plate 12. . The power feeding circuit 142 generates a high-frequency signal having an operating frequency using the resonance frequency f as an operating frequency.

［１．３．第２メタマテリアル素子／無給電素子］
第２メタマテリアル素子２０は、地板２１、平板２２、短絡部２３、無給電部２４を備える。

[1.3. Second metamaterial element / parasitic element]
The second metamaterial element 20 includes a ground plane 21, a flat plate 22, a short-circuit portion 23, and a parasitic portion 24.

  Since the ground plane 21, the flat plate 22, and the short circuit part 23 are the same as the ground plane 11, the flat plate 12, and the short circuit part 13 of the 1st metamaterial element 10, description is abbreviate | omitted. However, the ground plane 21 is formed integrally with the ground plane 11 and is in a conductive state.

  Similarly to the power supply conductor 141, the non-feeding portion 24 is made of a rod-shaped conductor, and one end is connected to the ground plate 21 and the other end is connected to the flat plate 22, and the ground plate 21 and the flat plate 22 are short-circuited. . The flat plate 22 is arranged such that the distance between the centers of the flat plates 12 and 22 is about λ / 4, where λ is the wavelength of the high frequency signal having the resonance frequency f.

  And the 2nd metamaterial element 20 is comprised so that it may become a 0th order resonator similarly to the electric power feeding element 10. FIG. However, the resonance frequency is configured to be lower than that of the feeding element 10. Hereinafter, the second metamaterial element 20 is referred to as a parasitic element 20.

  In the parasitic element 20 configured as described above, a current flows from the flat plate 22 through the short-circuit portion 23, the ground plane 21, and the parasitic portion 24 to the flat plate 22. Thereby, the radiated wave from the power feeding element 10 is received, and the radio wave is re-radiated from the end of the flat plate 22 in all directions along the surface of the flat plate 22.

  The resonance frequency of the parasitic element 20 is set to be lower than the resonance frequency of the feed element 10 by making the flat plate 22 have a larger area than the flat plate 12 of the feed element 10. That is, the capacitance of the capacitor formed by the ground plane 21 and the flat plate 22 is larger than the capacitance of the capacitor formed by the ground plane 21 and the flat plate 22, and as a result, as can be seen from the equation (1), the resonant frequency of the parasitic element 20. Is lower than the resonance frequency (that is, the operating frequency) of the feed element 10. In this case, the parasitic element 20 is inductive at the operating frequency, the phase of the current flowing in the parasitic element 20 is delayed when the parasitic element 20 receives a direct wave, and the positional relationship with the feeder element 10. Therefore, it functions as a reflecting element that reflects the direct wave radiated from the feeding element 10.

[1.4. Operation]
As shown in FIG. 3A, the planar antenna 1 configured as described above has a beam formed in a direction from the parasitic element 20 toward the feeding element 10, and radiation in the opposite direction is suppressed. Has radiation characteristics. This radiation characteristic is such that the operating frequency is 2400 MHz, the distance between the ground planes 11 and 21 and the flat plates 12 and 22 is 5 mm, the diameters of the short-circuit portions 13 and 23 are 1 mm, and the flat plate 12 of the feeding element 10 has a side of 20.2 [ mm], the flat plate 22 of the parasitic element 20 is a square having a side of 22 [mm], and the distance between the centers of the flat plates 12 and 22 is 22 [mm]. For reference, FIG. 3B shows the radiation characteristics of a planar antenna composed only of the feed element 10. In this case, it can be seen that the radiation characteristic is equivalent to that of the monopole antenna.

[1.5. effect]
As described above, according to the planar antenna 1, a unidirectional pattern equivalent to that of the Yagi / Uda antenna can be realized by a smaller and planar structure as compared with the case of using a monopole antenna. it can.

[2. Second Embodiment]
[2.1. Constitution]
Since the basic configuration of the planar antenna 1a of the second embodiment is the same as that of the planar antenna 1 of the first embodiment, the description of the common configuration will be omitted, and differences will be mainly described.

  In the first embodiment, the ground plates 11 and 21 of the feeding element 10 and the parasitic element 20 are integrally formed. On the other hand, as shown in FIG. 4, the planar antenna 1a according to the second embodiment is configured such that the ground plane 11a of the feed element 10a and the ground plane 21a of the parasitic element 20a are separated from each other and become non-conductive. .

  In addition, since it becomes difficult to fix the positional relationship between the feeding element 10a and the parasitic element 20b by separating the ground planes 11a and 21a, the ground planes 11a and 21a are formed on the same printed circuit board 3. .

[2.2. effect]
According to the planar antenna 1a configured as described above, an effect equivalent to that of the planar antenna 1 of the first embodiment can be obtained. Furthermore, in the planar antenna 1a, by separating the ground planes 11a and 21a, the operations of the feeding element 10a and the parasitic element 20a can be balanced, and as a result, as shown in FIG. Compared with the radiation characteristic of the flat antenna 1 (see FIG. 5B), the launch in the maximum radiation direction with respect to the horizontal plane can be suppressed (see FIG. 5A).

[3. Third Embodiment]
Since the basic configuration of the planar antenna 1b according to the third embodiment is the same as that of the planar antenna 1 according to the first embodiment, the description of the common configuration will be omitted, and differences will be mainly described.

[3.1. Constitution]
As illustrated in FIG. 6, the planar antenna 1 b includes a first metamaterial element (hereinafter referred to as a power feeding element) 10 b and a second metamaterial element (hereinafter referred to as a parasitic element) 20 b.

[3.2. First Metamaterial Element / Feeding Element]
The power feeding element 10 b includes a ground plane 11 b, a flat plate 12 b, M (M = 4 in the drawing) short-circuit portions 13, and a power feeding portion 14.

  Each of the ground plane 11b and the flat plate 12b is made of a conductor formed in a rectangular plate shape, and the both are spaced apart from each other. The flat plate 12b is formed in a shape in which M flat plates 12 of the first embodiment are connected in a row, and is arranged so that the short direction of the shape of the flat plate 12b coincides with the arrangement direction of the feeding element 10b and the parasitic element 20b. ing.

  The short circuit part 13 is each arrange | positioned in the center of each site | part which divided the flat plate 12b into M by the magnitude | size of the flat plate 12 in the longitudinal direction. In other words, the M short-circuit portions 13 are arranged in a line along the direction orthogonal to the arrangement direction of the feeding element 10b and the parasitic element 20b, that is, the longitudinal direction of the shape of the flat plate 12b.

  The power feeding unit 14 includes a power feeding conductor 141 and a power feeding circuit 142, and is disposed near the center of the flat plate 12b. Specifically, it is arranged at a position slightly shifted in the short direction from the center of the flat plate 12b.

  In other words, the power supply element 10b is obtained by connecting the unit cells in a row with the unit cell excluding the power supply element 14 from the power supply element 10 of the first embodiment, and providing the power supply part 14 near the center. Has a structure.

[3.3. Second metamaterial element / parasitic element]
The parasitic element 20 b includes a ground plane 21 b, a flat plate 22 b, N (N = 4 in the figure) short-circuit portions 23, and a power supply portion 24.

  Each of the ground plane 21b and the flat plate 22b is made of a conductor formed in a rectangular plate shape, and both are spaced apart from each other. The flat plate 22b is formed in a shape in which N flat plates 22 of the first embodiment are connected in a row, and is arranged so that the short direction of the shape of the flat plate 22b coincides with the arrangement direction of the feeding element 10b and the parasitic element 20b. ing. In addition, the ground plane 21b is comprised integrally with the ground plane 11b.

  The short circuit part 23 is each arrange | positioned in the center of each site | part which divided the flat plate 22b into the size of the flat plate 22 in the longitudinal direction. In other words, the N short-circuit portions 23 are arranged in a line along a direction orthogonal to the arrangement direction of the feeding element 10b and the parasitic element 20b, that is, the longitudinal direction of the shape of the flat plate 22b. Specifically, it is arranged at a position slightly shifted from the center of the flat plate 22b in the short direction.

The power feeding unit 24 is disposed near the center of the flat plate 22b.
That is, the parasitic element 20b is formed by removing the parasitic element 24 from the parasitic element 20 of the first embodiment as a unit cell, connecting the unit cells in a row, and forming a parasitic cell near the center. The portion 24 is provided.

[3.4. Action / Effect]
In the planar antenna 1b configured as described above, the resonance frequencies of the feeding element 10c and the parasitic element 20c are determined by the capacitance per unit cell and the inductance. That is, as a feature of the metamaterial element that performs zero-order resonance, even if unit cells are connected in parallel, the resonance frequency does not change and a vertical electric field having the same phase is generated in each unit cell. Is obtained.

  According to the planar antenna 1b configured as described above, an effect equivalent to that of the planar antenna 1 of the first embodiment can be obtained. Furthermore, in the planar antenna 1b, since the feeding element 10b and the parasitic element 20b are configured by a plurality of unit cells, the size in the longitudinal direction of the flat plate 12b corresponding to the antenna opening surface can be sufficiently secured. As a result, the directional beam can be made more narrowed.

  Note that the number of unit cells constituting the feeding element 10b and the parasitic element 20b, that is, the numbers M and N of the short-circuit portions 13 and 23 are the same as those of the planar antenna 1c shown in FIG. It may be different from 20c. In the figure, the case of M = 2 and N = 4 is shown. The ground planes 11c and 21c are integrally formed, the flat plate 12c is formed in a size corresponding to M unit cells, and the flat plate 22c is formed in a size corresponding to N unit cells.

[4. Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention can take a various form, without being limited to the said embodiment.

  (1) In the above embodiment, in order to set the resonance frequency of the parasitic element 20 to a value different from the resonance frequency (operation frequency) of the feed element 10, the areas of the flat plates 12 and 22 are made different. Although the capacity | capacitance part of the element 10 and the parasitic element 20 is adjusted, it is not restricted to this. For example, like the planar antenna 1d shown in FIG. 8, the flat plate 22d of the parasitic element 20d is made the same size as the flat plate 12 of the feed element 10, and the diameter of the short-circuit portion 23d is different from that of the short-circuit portion 13. The inductance of the parasitic element 20d may be adjusted.

  (2) In the said embodiment, it is comprised so that a parasitic element may function as an inductive reflective element by setting the resonant frequency of a parasitic element lower than the resonant frequency (operating frequency) of a feeder element. However, the present invention is not limited to this. For example, the resonant frequency of the parasitic element is set higher than the operating frequency, specifically, the area of the flat plate of the parasitic element is reduced or the diameter of the short-circuited portion is increased compared to the feeder element. Thus, the parasitic element may be configured to function as a capacitive director.

  (3) In the above embodiment, the resonance frequency of the parasitic element is different from the operating frequency, but may be the same as the operating frequency. In this case, the phase of the re-radiated wave from the parasitic element going from the parasitic element to the side of the feed element and the phase of the radiated wave from the feeding element going in the same direction are the same as the phase of the radiated wave from the parasitic element. What is necessary is just to adjust the arrangement | positioning space | interval with the electric power feeding element 20 suitably.

  (4) In the above embodiment, the case where there is one parasitic element has been described, but the present invention is not limited to this. For example, an inductive parasitic element that functions as a reflecting element and a capacitive parasitic element that functions as a director may be arranged in a row on both sides of the feeding element. Furthermore, a plurality of capacitive parasitic elements that function as a director may be provided. The arrangement of the plurality of parasitic elements can be designed in the same manner as the Yagi / Uda antenna configured using a dipole antenna.

  (5) The functions of one component in the above embodiment may be distributed to a plurality of components, or the functions of a plurality of components may be integrated into one component. Further, at least a part of the configuration of the above embodiment may be replaced with a known configuration having the same function. Moreover, you may abbreviate | omit a part of structure of the said embodiment. Further, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment. In addition, all the aspects included in the technical idea specified only by the wording described in the claim are embodiment of this invention.

  (6) In addition to the planar antenna described above, the present invention can be realized in various forms such as a system including the planar antenna as a constituent element.

  DESCRIPTION OF SYMBOLS 1,1a-1d ... Planar antenna, 10, 10a-10c ... 1st metamaterial element (feeding element), 11, 11a-11c, 21, 21a, 21c ... Ground plane, 12, 12b, 12c, 22, 22b-22d ... Flat plate, 13, 23, 23d ... Short circuit part, 14, 24 ... Feeding part, 20, 20a to 20d ... Second metamaterial element (parasitic element), 141 ... Feeding conductor, 142 ... Feeding circuit

Claims (7)

Each of them is a ground plate (11, 21) which is a conductor formed in a plate shape, flat plates (12, 22) which are conductors arranged so as to be spaced apart from the ground plate, and short-circuits between the ground plate and the flat plate A plurality of metamaterial elements (10, 20) having at least one short-circuited portion (13, 23) and having zero-order resonance,
One of the plurality of metamaterial elements is a power feeding element (10) including a power feeding unit (14) connected to the flat plate to feed power, and the metamaterial elements other than the power feeding element short-circuit the flat plate to a ground plane. It is configured as a parasitic element (20) with a parasitic part (24),
The planar antenna, wherein the feeding element and the parasitic element are arranged along a beam radiation direction.   At least one of the parasitic elements is configured as a capacitive parasitic element whose resonance frequency is set higher than that of the feeding element, or an inductive parasitic element whose resonance frequency is set lower than that of the feeding element. The planar antenna according to claim 1, wherein:   The resonance frequency of the parasitic element is adjusted by making the area per short-circuited portion obtained by dividing the area of the flat plate by the number of short-circuited portions different from that of the power-feeding element. The described planar antenna.   The planar antenna according to claim 2, wherein the resonance frequency of the parasitic element is adjusted by making a diameter of the short-circuit portion different from that of the feeder element.   The said short circuit part is arrange | positioned along the orthogonal direction with respect to the arrangement direction of the said metamaterial element, as for the said metamaterial element (10b, 10c, 20b, 20c) provided with the said multiple short circuit part, The said short circuit part is arrange | positioned. The planar antenna according to any one of claims 1 to 4.   The planar antenna according to any one of claims 1 to 5, wherein a ground plane constituting the feeding element and a ground plane constituting the parasitic element are electrically connected.   The planar antenna according to any one of claims 1 to 5, wherein a ground plane constituting the feeder element and a ground plane constituting the parasitic element are non-conductive.

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