JP2009246460A - Microstrip antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small microstrip antenna capable of performing directivity control. <P>SOLUTION: The microstrip antenna comprises a dielectric substrate 1, a patch 3 arranged on the dielectric substrate 1, a pair of parasitic elements 10a and 10b (20a and 20b) prepared at outside of the edge of the patch 3 and prepared with a space perpendicular to dielectric substrate 1, which constitute a waveguide device or a reflector of dipole version, and a reactance variable circuit connected to the pair of parasitic elements 10a and 10b (20a and 20b). It is characterized in that the reactance variable circuit is attached at a member 14 (24) prepared between the dielectric substrate 1 and an intermediate portion 13 (23) inserted between the pair of parasitic elements 10a and 10b (20a and 20b). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a microstrip antenna including a reactance variable circuit.

  Conventionally, as a patch-type microstrip antenna, one or a plurality of linear or strip-like non-excitations are perpendicular to the antenna main axis and orthogonal to each other on the P-axis and Q-axis. The element is provided close to the outer periphery of the patch, the resonance mode direction of the patch is P-axis, and the non-excitation element provided in the direction on the P-axis is an element perpendicular to the dielectric substrate, and is on the Q-axis. The non-excited element provided in the direction of is parallel to the dielectric substrate surface and is separated from the dielectric substrate surface and extends in the P-axis direction or the center of the horizontal element is the dielectric substrate surface. There is known a microstrip antenna characterized in that it is a T-type element grounded on the ground (see, for example, Patent Document 1).

On the other hand, as an antenna structure that can control the directivity of the antenna, a feeding element and at least one parasitic element are arranged at a predetermined interval, and these elements are of a loop type or an inverted F type, An antenna structure is known in which a parasitic element includes a variable reactance element and has an electric length changeable (see, for example, Patent Document 2).
Japanese Patent Publication No. 6-82777 JP-A-2005-252406

  However, in the microstrip antenna, when the directivity of the antenna is controlled by changing the reactance by the reactance variable circuit connected to the non-excitation element, depending on the installation location of the reactance variable circuit, the microstrip antenna becomes large as a whole, It is not possible to take advantage of the miniaturization of the microstrip antenna.

  Therefore, an object of the present invention is to provide a small microstrip antenna capable of directivity control.

In order to achieve the above object, a microstrip antenna according to the present invention includes:
A dielectric substrate;
A patch provided on the dielectric substrate;
A pair of non-excited elements constituting a dipole-type director or reflector, provided outside the edge of the patch and spaced apart in a direction perpendicular to the dielectric substrate;
A reactance variable circuit connected to the pair of non-excitation elements, and a microstrip antenna,
The reactance variable circuit is attached to a member provided between an intermediate portion sandwiched between the pair of non-excitation elements and the dielectric substrate.

  Here, a first virtual plane that passes through a first end portion on the intermediate portion side of the first non-excitation element, which is one element of the pair of non-excitation elements, is perpendicular to the dielectric substrate. A second virtual plane perpendicular to the dielectric substrate and passing through the second end of the second non-excitation element, which is the other element of the pair of non-excitation elements, on the intermediate portion side It is preferable that the reactance variable circuit is attached to the member within a range sandwiched between the members.

The reactance variable circuit is set to each of the first non-excitation element and the second non-excitation element,
It is preferable that a first reactance variable circuit is connected to the first non-excitation element, and a second reactance variable circuit is connected to the second non-excitation element. In addition, it is preferable that the reactance variable circuit is attached to an attachment surface of the member perpendicular to the dielectric substrate. Furthermore, it is preferable that the perpendicular direction of the mounting surface coincides with the extending direction of the pair of non-excitation elements or the direction perpendicular to the extending direction.

  According to the present invention, a microstrip antenna capable of directivity control can be reduced in size.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a microstrip antenna 100 according to an embodiment of the present invention. The microstrip antenna 100 is an Esper antenna that can electrically control its directivity. The microstrip antenna 100 is provided outside the side 3 d that is one of the four sides of the dielectric substrate 1, the rectangular patch (conductor) 3 provided on the surface of the dielectric substrate 1, and the patch 3. A pair of non-exciting elements 10a and 10b constituting a dipole-type director, and a pair of non-exciting elements 20a constituting a dipole-type director provided outside the side 3c facing the side 3d of the patch 3 20b, a reactance variable circuit (attached to the vertical member 14) electrically coupled to the pair of non-excitation elements 10a and 10b, and a reactance variable circuit (vertical) electrically coupled to the pair of non-excitation elements 20a and 20b. Attached to the member 24). In FIG. 1, an X direction and a Y direction are directions parallel to the surface of the dielectric substrate 1 (the surface of the patch 3) and are orthogonal to each other. That is, the X direction and the Y direction are perpendicular to the direction of the radiation main axis of the patch 3 (Z direction). In the case of FIG. 1, the Y direction is a direction parallel to the side 3d (3c) of the patch 3, and the X direction is a direction perpendicular to the side 3d (3c).

  A patch 3 is formed on the front surface of the dielectric substrate 1, and a conductive ground plate 2 is formed on the back surface of the dielectric substrate 1 by a conductive material such as copper foil. Power supply to the patch 3 that is a radiating element is performed from the back side of the dielectric substrate 1, and 4 is the power supply point. The feed point 4 has, for example, a pin structure that connects the front surface side and the back surface side of the dielectric substrate 1. The feeding point 4 and its pin are not electrically connected to the ground plane 2. That is, the power feeding part on the back side of the dielectric substrate 1 is covered with a conductive material except for a slight periphery of the power feeding part on the back side. The feeding point 4 is located at the center of the patch 3 in the Y direction and is shifted to one side of the patch 3 in the X direction (in FIG. 1, it is shifted to the side 3d). Therefore, the X direction is the direction in which the resonance current flows and the direction of the resonance mode.

  The non-exciting elements 10a and 10b and the non-exciting elements 20a and 20b are linear or strip-shaped elements, and are disposed at positions where electromagnetic coupling can be established with the patch 3 that is a radiator. For example, the non-exciting elements 10 a and 10 b and the non-exciting elements 20 a and 20 b are located at the same distance from the center of the patch 3. As a specific example, when the wavelength of the electromagnetic wave is λ, the interval in the X direction between the non-excitation elements 10a and 10b and the side 3d that is the edge of the patch 10 is set to 0.05λ or more and 0.5λ or less, The interval in the Z direction between the non-excitation elements 10a and 10b and the dielectric substrate 1 is preferably set to 0.1λ or more and 0.2λ or less. The same applies to the non-excitation elements 20a and 20b.

  The non-excitation elements 10a and 10b are provided on the surface of the pedestal 11 made of a dielectric material or the like. The non-excitation elements 10a and 10b extend in opposite directions to each other in the Y direction while being spaced apart and parallel to the surface of the dielectric substrate 1. Further, spacers 12a and 12b are provided for stably disposing the non-excitation elements 10a and 10b away from the dielectric substrate 1 at predetermined positions. The spacers 12a and 12b fix the pedestal 11. The non-excitation elements 20a and 20b and the peripheral structure thereof are the same as the non-excitation elements 10a and 10b as shown in FIG. Hereinafter, the description may be omitted for the same reason.

  FIG. 2 is an example of a reactance variable circuit connected to a non-excitation element. A non-excitation element can change directivity by connecting with a reactance variable circuit. The reactance variable circuit X is provided in each of the non-excitation elements 10a and 10b. The reactance variable circuit X is connected in series from the input terminal dc to the output terminal RF in the order of the resistor 51, the first inductive element 53, and the second inductive element 55, and the resistor 51, the first inductive element 53, In the circuit, a capacitive element 52 is provided between the intermediate point and the ground point, and a varactor 54 is provided between the intermediate point between the first inductive element 53 and the second inductive element 55 and the ground point. is there. The reactance variable circuit X is a circuit that changes the reactance by displacing the characteristics of the varactor 54 in accordance with the DC voltage value input from the input terminal dc. The output terminal RF is connected to the non-excitation element. The directivity of the microstrip antenna 100 can be changed because the pair of non-excited elements become waveguides (or become reflectors) according to the reactance value.

  FIG. 3 is an explanatory diagram of the arrangement of the reactance variable circuit X. FIG. 3 shows four configuration examples A to D in which a pair of non-excitation elements are attached to a pedestal. (A *) and (b *) are in a front-back relationship, (a *) is a view from the front side, and (b *) is a view from the back side. A is a normal dipole-type waveguide. B is a director obtained by adding a reactance variable circuit X to the configuration of A. When the reactance variable circuit X is added on the surface of the pedestal 51, the total length B2 of the non-excitation element becomes long and may be longer than the length of one side of the patch 3. That is, in the dipole-type director, λ / 4 elements are arranged with a small distance A1 from each other as in A, but the reactance variable circuit X is interposed in the distance A1, so that λ / The four elements are separated (A1 <A2), which may affect directivity and impedance characteristics. In addition, a configuration in which the reactance variable circuit X is installed on the back side of the pedestal 51 as in C is conceivable. However, since the reactance variable circuit X exists immediately below the λ / 4 element, it may interfere with antenna radiation.

  Therefore, as shown in D, the reactance variable circuit X1a connected to the non-excitation element 10a and the non-excitation are provided on the back side (dielectric substrate 1 side) of the base 11 within a range between the pair of non-excitation elements 10a and 10b. A reactance variable circuit X1b connected to the element 10b is installed. By installing in this way, the influence on directivity and impedance characteristics can be suppressed, and the characteristics of a normal λ / 2 antenna can be obtained.

  FIG. 4 is a detailed layout diagram of the reactance variable circuit X. The reactance variable circuit X is attached to the vertical member 14. For example, the vertical member 14 is a member that extends from the intermediate portion 13 sandwiched between the non-excitation elements 10a and 10b in a direction perpendicular to the extension direction of the pair of non-excitation elements 10a and 10b. The vertical member 14 contacts the surface of the dielectric substrate 1. The vertical member 14 has a mounting plane on which a reactance variable circuit X or a circuit board on which the reactance variable circuit X is mounted can be mounted. The mounting plane is, for example, a plane perpendicular to the surface of the dielectric substrate 1.

  FIG. 4A shows a case where the perpendicular direction of the mounting plane 14a and the mounting plane 14b coincides with the extending direction of the non-excitation elements 10a and 10b. FIG. 4B shows a case where the perpendicular direction of the mounting plane 14c and the mounting plane 14d coincides with the direction perpendicular to the extending direction of the non-excitation elements 10a and 10b (14d is the opposite surface of 14c). Therefore, no indication on the diagram).

  In the case of FIG. 4A, the reactance variable circuit X1a connected to the non-excitation element 10a via the conductor 15a is attached to the mounting plane 14a, and the reactance variable circuit X1b connected to the non-excitation element 10b via the conductor 15b. Is attached to the mounting plane 14b. In the case of FIG. 4B, the reactance variable circuit X1c connected to the non-excitation element 10a via the conductor 15a is attached to the mounting plane 14c, and the reactance variable circuit X1d connected to the non-excitation element 10b via the conductor 15b. Is attached to the attachment plane 14d (X1d is attached to the attachment plane 14d, which is the opposite surface of 14c, and is not indicated in the figure).

  In addition, the non-excitation element installed on the front surface side of the pedestal 11 and the reactance variable circuit installed on the back side of the pedestal 11 are connected to each other via a conductive wire passing through the through hole of the pedestal 11. The conducting wire 15a is connected to the end portion 10aa on the intermediate portion 13 side of the non-excitation element 10a. The conducting wire 15b is connected to the end portion 10bb on the intermediate portion 13 side of the non-excitation element 10b. A virtual plane passing through the end portion 10aa to which the conducting wire 15a is connected and is perpendicular to the surface of the dielectric substrate 1 and a virtual plane passing through the end portion 10bb to which the conducting wire 15b is connected and The reactance variable circuit X is attached to the plane of the vertical member 14 in a space sandwiched between a virtual plane P2 perpendicular to the surface. When the reactance variable circuit X is in this space, the antenna radiation is not disturbed as in the case of FIG. 3C, and the influence on the radiation characteristics of the antenna due to the arrangement of the reactance variable circuit can be suppressed. Further, as compared with the case of FIG. 3B, it is possible to suppress the total length of the non-excitation elements from being increased, and to suppress the influence on the radiation characteristics of the antenna due to the separation of the non-excitation elements.

  In addition, when the height of the component of the reactance variable circuit X (the component such as the inductive element, the capacitive element, and the varactor shown in FIG. 2) from the mounting plane is low, it is arranged as shown in FIG. However, the distance in the extending direction between the end 10aa and the end 10bb can be reduced. Further, when the height of the component of the reactance variable circuit X from the mounting plane is high, the distance between the end portion 10aa and the end portion 10bb becomes long, so that the arrangement as shown in FIG. By doing, the distance of the extending direction between edge part 10aa and edge part 10bb can be narrowed.

  FIG. 4 shows a case where the perpendicular direction of the virtual planes P1 and P2 is the same direction as the extending direction of the non-excitation elements 10a and 10b. Ideally, it should be within this range, but the reactance variable circuit X is attached to the plane of the vertical member 14 in the space between the virtual planes P1 and P2 when the direction is not the same as the extending direction. May be.

  Therefore, even if the microstrip antenna 100 is provided with a reactance variable circuit, the microstrip antenna 100 can be easily miniaturized and good antenna characteristics can be obtained. Further, even if the dielectric constant of the non-exciting element is not increased, the necessary length of the non-exciting element is ensured and effective directivity induction is possible.

  The microstrip antenna 100 is particularly suitable for use as an in-vehicle antenna device for wirelessly transmitting / receiving or receiving data to / from a communication facility or broadcasting facility outside the vehicle. Since it has the main plate 2, it is easy to install on the outer plate of the vehicle. The in-vehicle antenna device in this case is preferably used as an antenna for detecting an obstacle around the own vehicle such as a person or a bicycle. The in-vehicle antenna device also includes, for example, detection information related to obstacles around the vehicle such as people and bicycles, vehicle periphery information, vehicle registration information, audio information, image information, call information, inter-vehicle communication information, ETC communication information. It is preferably used for receiving or transmitting / receiving data such as television broadcast waves. In particular, it is suitable to be used in a microwave or millimeter wave frequency band, and for example, it can be used in a frequency band of 2.4 GHz band or 5.8 GHz band.

  FIG. 5 is a configuration diagram of a microstrip antenna 200 according to an embodiment of the present invention. The microstrip antenna 200 includes a pair of non-excited elements that constitute a dipole-type waveguide outside all four sides of the rectangular patch 3. The non-exciting elements 30a and 30b and the non-exciting elements 40a and 40b need not be described because the structure including the peripheral structure and the arrangement relationship with the patch 3 may be considered in the same manner as in the above-described embodiment. Thereby, in addition to the directivity control in the X direction, the directivity in the Y direction can be easily controlled, and the directivity can be induced in a range of 360 °. In FIG. 5, the reactance variable circuit X3d connected to one of the non-exciting elements 30a and 30b is the mounting surface of the vertical member 34 whose vertical line coincides with the Y direction (in the case of FIG. Although it is attached to the surface 34d), it may be attached to an attachment surface whose vertical line coincides with the X direction. Note that another reactance variable circuit different from the reactance variable circuit X3d is connected to the other non-excitation element different from the non-excitation element connected to the reactance variable circuit X3d and attached to the vertical member 34. The same applies to the reactance variable circuit X4c connected to one of the non-excitation elements 40a and 40b.

  FIG. 6 is a configuration diagram of a microstrip antenna 300 according to an embodiment of the present invention. In the microstrip antenna 300, λ / 4 type monopoles 16 and 26 are arranged in the direction perpendicular to the dielectric substrate 1 outside the non-excitation elements arranged in the X direction (on the side opposite to the patch 3 with respect to the non-excitation elements). Equipped upright. By arranging 16 and 26, the directivity control in the X direction can be further strengthened.

  FIG. 7 is a configuration diagram of a microstrip antenna 400 according to an embodiment of the present invention. The microstrip antenna 400 includes T-type monopoles 17 and 27 equivalent to λ / 4 outside the non-excitation elements arranged in the X direction. By providing 17, 27, it is possible to reduce the height of the microstrip antenna compared to the case of FIG. 6 while enhancing the directivity in the X direction. This is because the simple monopole illustrated in FIG. 6 is long in the Z direction, so that the height of the radome covering the microstrip antenna becomes high. Further, a low-profile non-excitation element such as an inverted F antenna may be used.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  For example, in the above-described embodiment, the feeding method to the patch 3 is a two-point feeding method in which the phase is shifted, or a one-point feeding method using a degenerative separation element, so that the patch 3 is not limited to a linearly polarized wave. The waves can be controlled.

  Further, the vertical member such as 14 may be a polygonal column having a side surface to which the reactance variable circuit can be attached, or may be a column in which the side surface of the column is cut to form the side surface. Further, the reactance variable circuit may be built in the vertical member.

It is a block diagram of the microstrip antenna 100 which is one Embodiment of this invention. It is an example of the reactance variable circuit connected to a non-excitation element. FIG. 6 is an explanatory diagram regarding an arrangement of a reactance variable circuit X. 3 is a detailed layout diagram of a reactance variable circuit X. FIG. It is a block diagram of the microstrip antenna 200 which is one Embodiment of this invention. It is a block diagram of the microstrip antenna 300 which is one Embodiment of this invention. It is a block diagram of the microstrip antenna 400 which is one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dielectric substrate 2 Ground plane 3 Patch 4 Feeding point 10, 20, 30, 40, 50 Non-excitation element 11, 21, 31, 41, 51 Base 12, 22, 32, 42 Spacer 13, 23, 33, 43 Intermediate part 14, 24, 34, 44 Vertical member 100, 200, 300, 400 Microstrip antenna X Reactance variable circuit

Claims (5)

A dielectric substrate;
A patch provided on the dielectric substrate;
A pair of non-excited elements constituting a dipole-type director or reflector, provided outside the edge of the patch and spaced apart in a direction perpendicular to the dielectric substrate;
A reactance variable circuit connected to the pair of non-excitation elements, and a microstrip antenna,
The microstrip antenna, wherein the reactance variable circuit is attached to a member provided between an intermediate portion sandwiched between the pair of non-excitation elements and the dielectric substrate.   A first virtual surface that passes through a first end portion on the intermediate portion side of the first non-excitation element, which is one element of the pair of non-excitation elements, and is perpendicular to the dielectric substrate; A second virtual surface passing through the second end portion on the intermediate portion side of the second non-excitation element, which is the other element of the pair of non-excitation elements, and perpendicular to the dielectric substrate; The microstrip antenna according to claim 1, wherein the reactance variable circuit is attached to the member within a range sandwiched between the members. The reactance variable circuit is set to each of the first non-excitation element and the second non-excitation element,
The microstrip antenna according to claim 1 or 2, wherein a first reactance variable circuit is connected to the first non-excitation element, and a second reactance variable circuit is connected to the second non-excitation element.   The microstrip antenna according to any one of claims 1 to 3, wherein the reactance variable circuit is attached to an attachment surface of the member perpendicular to the dielectric substrate.   5. The microstrip antenna according to claim 4, wherein a perpendicular direction of the mounting surface coincides with an extending direction of the pair of non-excitation elements or a direction perpendicular to the extending direction.

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