JP4466729B2 - Double resonance antenna - Google Patents

Description

  The present invention relates to a compact multi-resonant antenna comprising a plurality of parallel metal wirings as a basic structure, and a plurality of identical or similar unit circuits arranged in a line in the direction of the metal wiring and connected to each other. In particular, the present invention relates to a dipole antenna and an inverted L-type antenna.

  As shown in Non-Patent Document 6, since the left-handed medium has been realized, its research has been actively conducted and applied to antennas. Here, the left-handed medium is a material whose dielectric constant and permeability are both negative. When electromagnetic waves propagate through the left-handed medium, the group velocity and the phase velocity are reversed. Further, in the left-handed medium, there is a characteristic that the wavelength becomes shorter as the frequency of the electromagnetic wave becomes lower.

  Non-Patent Document 1 discloses a leaky wave antenna, Non-Patent Documents 2 to 4 disclose a small antenna formed on the ground, and Patent Document 1 discloses a dipole antenna.

  FIG. 21 shows a linear dipole antenna A10 operating in the left-handed system disclosed in Patent Document 1. Two parallel metal wirings p10 and q10 have a basic structure, and six unit circuits U10 having a length a are connected in the x-axis direction (the direction of the metal wirings p10 and q10). The unit circuit U10 includes two capacitors CSE10 connected in series on a part of the metal wiring p10, and a communication unit that connects the metal wiring p10 and the metal wiring q10 via the inductor LSH10. ing. A feeding point F composed of two points FL and FR is located at the center of the metal wiring p10.

  Since the dipole antenna A10 has a configuration in which the capacitor CSE10 and the inductor LSH10 are periodically arranged, the dipole antenna A10 can be operated in a left-handed system. In the left-handed system, the wavelength can be shortened as the frequency decreases as described above. Therefore, the antenna length L10 of the dipole antenna A10 can be reduced to about 1/10 of the operating wavelength by controlling the capacitance value of the capacitor CSE10 and the inductance value of the inductor LSH10.

Non-Patent Document 5 shows a two-resonance antenna operated in a right-handed system and a left-handed system.
JP 2006-295873 A L. Liu, C. Caloz, and T. Itoh, "Dominant mode leaky-wave antena with backfire-to-endfire scanning capability", Electron. Lett., Vol.38, no.23, pp.1414-1416, Nov .2002 M. Schuessler, J. Freese, and R. Jakoby, "Design of compact planar antennas using LH-transmission lines", 2004 IEEE MTT-S Int. Microwave Symp. Dig., Vol.1, pp.209-212, Fort Worth, TX, jun. 2004 CJ Lee, KMH Leong, and T. Itoh, "Design of resonant small antenna using composite right / left-handed transmission line", IEEE Int. Antennas Propagat. Symp. Dig., Vol. 2B, pp. 218-221, Washington DC, Jul. 2005 F. Qureshi, MA Antoniades, and GV Eleftheriades, "A compact and low-profile metamaterial ring antenna with vertical polarization", IEEE Antennas and Wireless Propagat. Lett., Vol.4, pp.333-336, 2005 S. Otto, A. Rennings, C. Caloz, P. Waldow, and T. Itoh, "Composite Right / Left-Handedλ-Resonator Ring Antenna for Dual-Frequency Operation", IEEE Int. Antennas Propagat. Symp. Dig., vol.1A, pp.684-687, Washington DC, Jul.2005 RA Shelby, DR Smith, and S. Schultz, “Experimental verification of a negative index of refraction,” Science, vol.292, pp.77-79, Apr. 2001.

  In the tire pressure warning system and smart entry system, which are in-vehicle applications, the 400 MHz band is allocated in Europe, and the 300 MHz band is allocated in North America and Japan. Since the mounting locations of the antennas used for these are limited, an antenna that is small and can share two frequencies of the 300 MHz band and the 400 MHz band is desired.

  However, with a normal right-handed antenna, for example, when the first resonance occurs at 300 MHz, the second resonance occurs around 900 MHz, which is approximately three times that of the first resonance. The dipole length corresponds to ½ times the operating wavelength in the first resonance, and 3/2 times the operating wavelength in the second resonance. As described above, an antenna operating in a right-handed system has a wide frequency interval between the first resonance and the second resonance, and cannot be used for the above-described applications.

  On the other hand, in the left-handed system, the frequency is lowered, the wavelength is shortened, and the frequency interval can be shortened. That is, the first resonance can be generated near 400 MHz (1/2 wavelength), and the second resonance can be generated near 300 MHz (3/2 wavelength). However, when the antenna length is shorter than the operating wavelength, the conventional dipole antenna A10 does not operate as an antenna because the currents cancel out in the opposite direction due to the second resonance.

  Further, in the method of realizing a two-resonance antenna by operating in a left-handed system and a right-handed system as in Non-Patent Document 5, the interval between resonant frequencies cannot be reduced. In addition, it is necessary to improve impedance by matching impedance at the feeding point.

  Accordingly, an object of the present invention is to realize a small and multi-resonant antenna that resonates at a narrow frequency interval. Another object of the present invention is to provide a structure that facilitates impedance matching at the feeding point.

A first invention is a dipole antenna comprising a plurality of parallel metal wirings as a basic structure and a plurality of identical or similar unit circuits arranged in a line in the direction of the metal wiring and connected to each other. The unit circuit includes a connecting portion that connects metal wirings to each other via at least one first inductor, and at least one first wiring inserted on at least one of the metal wirings. Each of the metal wirings is bent in a direction of 90 degrees with respect to the base and the base, passes through the central part of the plurality of metal wirings constituting the base, and has a symmetry axis perpendicular to each other. A pair of extension portions formed of metal wirings that are line-symmetric with respect to each other, and the ratio of the length of the base portion to one extension portion of the pair of extension portions is 1: n (n is a positive integer) Can resonate at two or more frequencies It is a dipole antenna, characterized in that it was.

  The base is a part that becomes a radiation source and a reception source. That is, the transmission antenna is a portion formed in the polarization direction of the transmission radio wave, and the reception antenna is a portion formed in the polarization direction in which the reception radio wave can be received most efficiently. The extension portion is a portion that is bent in the direction of 90 degrees with respect to the base portion and is continuously formed on the base portion.

  Similar unit circuits include circuits that are symmetrical to each other obtained by symmetrical transformation such as line symmetry, point symmetry, and rotational symmetry. In addition, in the unit circuit including the power feeding unit and the unit circuit disposed at the end, the input / output boundary conditions may be different from those of the other unit circuits. Circuits that have undergone slight modification or element capacitance adjustment to adjust the peculiarities of the boundary conditions are also included in similar unit circuits. The angle formed by the base portion and the extension portion does not need to be strictly 90 degrees, and may be any as long as it can be regarded as equivalent in terms of excitation.

Extension, through the central portion of a plurality of metal wires constituting the base, that is formed in line-symmetrical pair with respect to a vertical axis of symmetry, respectively. At both ends of the base portion, in the direction of 90 degrees, the extension portions parallel to each other are formed. This parallelism is not limited to being strictly parallel, but may be anything that can be regarded as equivalent in terms of excitation.

The second invention is characterized in that the value of n is 1 in the first invention.
The third invention is characterized in that, in the first or second invention, the resonable frequency exists from the 300 MHz band to the 400 MHz band.
The fourth invention is characterized in that, in any one of the first to third inventions, the continuum of the base portion and the pair of extension portions has a U-shape.
The fifth invention is characterized in that, in any one of the first to fourth inventions, the axis of symmetry is perpendicular to an arrangement surface constituted by a plurality of metal wirings constituting the base. That is, a base portion and an extension portion are configured in which a plane formed by a plurality of metal wirings is bent at 90 degrees.

The sixth invention is characterized in that, in any one of the first to fourth inventions, the symmetry axis is located in an arrangement surface constituted by a plurality of metal wirings constituting the base portion. In this case, the plurality of metal wirings are bent at 90 degrees on the plane formed by the plurality of metal wirings to form a base portion and an extension portion.
Also in these inventions, it is not necessary that the dipole antenna of the present invention has a strictly line-symmetric shape. Further, the plurality of metal wirings need not be strictly parallel.

According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the actual base portion that is a half of the length of the base portion is erected on the ground conductor, and one extension portion is Arranged in parallel to the ground conductor , the base is composed of a base real part and a mirror image of the base real part, and the pair of extension parts is composed of one extension part and a mirror image of the extension part. It is characterized by. An inverted L-type antenna is erected on the ground conductor. In this antenna, a ground conductor is used as a mirror surface, and a base part and an extension part standing on the ground conductor, and a mirror image thereof, a pair of upper and lower base parts perpendicular to the ground conductor, and a pair of parallel parts parallel to the ground conductor. An extension is formed.

An eighth invention is characterized in that, in any one of the first to sixth inventions, the invention comprises one or a plurality of the unit circuits, arranged in parallel to the base, and connected to the extension. And That is, the connection line is composed of unit circuits similar to the base and the extension. And the connecting line is provided in the side which has the edge part of an extension part with respect to a base in parallel with a base. The distance between the connection line and the base is desirably the length of the unit circuit or 1/2 of the length.

Further, a ninth aspect of the invention is the eighth aspect of the invention, wherein the base actual part that is a half of the base length and the connection line real part that is a half of the length of the connection line. Is extended up on the ground conductor, and one extension is arranged in parallel to the ground conductor, and the base is composed of a base real part and a mirror image of the base real part. Is constituted by a connection line actual part and a mirror image of the connection line actual part, and the pair of extension parts is constituted by one extension part and a mirror image of the extension part . The present invention is an antenna having a connection line, that is, an inverted F-type antenna is erected on a ground conductor. In this antenna, a ground conductor is used as a mirror surface, and a base portion, a connection line, and an extension portion that are erected on the ground conductor, and their mirror images, are parallel to the pair of upper and lower base portions, the connection line, and the ground conductor perpendicular to the ground conductor A pair of parallel extensions is formed.

According to a tenth aspect , in the first to ninth aspects, the feeding point is provided at the base. The eleventh invention is characterized in that, in the eighth or ninth invention, the feeding point is provided in the connection line.

  According to a twelfth aspect, in any one of the first to eleventh aspects, each unit circuit includes the same circuit, and each unit circuit is periodically arranged in the direction of the metal wiring and connected to each other. A dipole antenna.

  A thirteenth invention is a dipole antenna according to any one of the first to twelfth inventions, wherein both ends of each metal wiring are open ends.

  In a fourteenth aspect based on any one of the first to thirteenth aspects, the unit circuit is a second inserted in series on another metal wiring different from the metal wiring on which the first capacitor is disposed. This is a dipole antenna having an inductor.

  A fifteenth aspect of the present invention is the dipole antenna according to any one of the first to fourteenth aspects, wherein the connecting portion of the unit circuit includes a second capacitor connected in parallel to the first inductor. It is.

  A sixteenth aspect of the invention is a dipole antenna according to any one of the first to fifteenth aspects, wherein the inductor is formed of a meander-shaped inductor pattern.

  A seventeenth invention is a dipole antenna according to any one of the first to sixteenth inventions, wherein the capacitor is formed of a comb-shaped interdigital capacitor pattern.

  An eighteenth aspect of the invention is a dipole antenna according to any one of the first to seventeenth aspects of the invention, wherein the capacitor and the inductor are composed of lumped constant elements.

  According to a nineteenth aspect of the invention, in any one of the first to eighteenth aspects of the invention, there is provided a flexible substrate in which a conductor pattern is laminated, the inductor is constituted by a meander-shaped inductor pattern comprising a conductor pattern, and the capacitor is A dipole antenna comprising a comb-shaped interdigital capacitor pattern made of a conductor pattern.

Since the dipole antennas according to the first to seventh aspects of the present invention have a configuration in which unit circuits including a first capacitor and a first inductor are periodically arranged, the dipole antenna can be operated left-handed. In addition, by providing a line-symmetric structure by providing a bent portion, the current components of the extension in the direction of the symmetry axis can be canceled in opposite directions, and the current component of the base in the direction orthogonal to the symmetry axis is reversed. Directional components can be prevented from occurring. As a result, according to the configuration of the dipole antenna of the present invention, multiple resonance characteristics can be obtained. In addition, since it operates in a left-handed system, the frequency interval of resonance can be narrowed and a small antenna can be realized. In addition, a dipole antenna having n + 1 resonance characteristics can be realized.

Further, according to the eighth and ninth inventions, since the connection line connected to the extension portion is provided in parallel to the base portion, the impedance viewed from the antenna side from the feeding point can be increased, and at the feeding point, Impedance matching can be realized. As a result, power efficiency can be improved.
Further, according to the seventh or ninth invention, the symmetrically arranged portion is formed by a mirror image with the ground conductor as a mirror surface, so the size of the antenna is about half the size of the dipole antenna of the other invention. it is Ru can be.

  According to the twelfth invention, the design, configuration, and manufacture of the antenna can be simplified.

  Further, according to the thirteenth invention, the current near the feeding portion of the antenna becomes strong, that is, the antinode of resonance is generated near the central feeding portion, so that the generation and increase of reflected waves in the feeding portion are controlled. Can do.

  Further, according to the fourteenth and fifteenth inventions, it is easy to design a left-handed circuit.

  Further, if the metal wiring is formed with a conductor pattern and the inductor on the circuit is formed with a meander-shaped inductor pattern as in the sixteenth aspect of the invention, a small-sized antenna having multiple resonance characteristics can be obtained even with such a configuration. realizable. The sixteenth invention is preferably used in combination with the following seventeenth invention.

  Further, if the metal wiring is formed with a conductor pattern and the capacitor on the circuit is formed with an interdigital capacitor pattern as in the seventeenth aspect of the invention, a small-sized antenna having multiple resonance characteristics can be realized even with such a configuration. it can.

  According to the sixteenth and seventeenth inventions, the dipole antenna of the present invention can be formed on an inexpensive substrate.

According to the eighteenth aspect of the invention, since an antenna can be configured with metal wiring and lumped constant elements (chip elements), a dipole antenna having desired characteristics can be manufactured in a short period of time.
According to the nineteenth invention, the dipole antenna of the present invention can be formed using only a conductor pattern, and the bent portion can be easily provided by using a flexible substrate.

  Hereinafter, specific examples of the present invention will be described with reference to the drawings. However, the present invention is not limited to the examples.

  FIG. 1 is a perspective view of a dipole antenna A1 according to the first embodiment. The dipole antenna A1 has two parallel metal wirings p1 and q1 as a basic structure, and is a unit of length (length in the parallel direction of the metal wirings p1 and q1) a and width (interval between the metal wirings p1 and q1) d. The circuit U1 is configured by connecting six in the length direction.

  The unit circuit U1 includes two capacitors CSE1 (first capacitor of the present invention) connected in series on a part of the metal wiring p1 and two series connected on a part of the metal wiring q1. Inductor LSE1 (second inductor of the present invention) and a connecting portion that connects between metal wiring p1 and metal wiring q1 via inductor LSH1 (first inductor of the present invention). . The inductor LSE1 is provided for adjusting two resonance frequencies and impedance.

  The dipole antenna A1 includes a base 10 made of metal wirings p1b and q1b formed in the polarization direction of the radiated radio wave, and a pair of metal wirings p1a bent at 90 degrees with respect to the base 10 by bending portions 11 and 13. And a pair of extension portions 30 and 31 made of a pair of metal wirings q1a bent at 90 degrees by the bent portions 12 and 14. In the central portion of the base 10, a feeding point F composed of points FT and FB is provided at the midpoint of the metal wiring q1b in which the inductor LSE1 is inserted in the wiring in series.

  Bending portions (11, 12) and (13, 14) of 90 degrees with respect to the plane including the metal wirings p1 and q1, that is, the arrangement surface (xz plane in FIG. 1) of the base 10 which is the central portion of the metal wiring. Two metal wirings q1 are symmetrical with respect to the y-axis direction straight line passing through the feeding point F, that is, the symmetry axis L1, and the metal wiring p1 is symmetrical with respect to the y-axis direction passing through the middle point of the metal wiring, that is, symmetrical. The shape is axisymmetric with respect to the axis L2 (a U-shaped shape). Of the U-shaped shape, the extension 30 composed of two line segments of the parallel metal wirings p1 and q1 (that is, the line segments p1 and q1 along the y-axis direction in the drawing) p1a and q1a, Each 31 includes two unit circuits U1. Further, the base 10 composed of line segments p1b and q1b of metal wirings p1 and q1 connected perpendicularly to the line segments p1a and q1a (that is, line segments p1 and q1 along the z-axis direction in the figure) is composed of two unit circuits. Consists of U1. Therefore, the length L of the line segments p1a and q1a of the extension portions 30 and 31 and the length 2h of the line segments p1b and q1b of the base portion 10 are 1: 1. L and 2h are set to 60 mm. Further, both ends of the dipole antenna A1 (both ends of the metal wirings p1 and q1) are open ends.

  The dipole antenna A1 can be operated in a left-handed system by periodically arranging a capacitor CSE1 inserted on the metal wiring p1 and an inductor LSH1 inserted between the metal wiring p1 and the metal wiring q1. it can. The currents I1 and I2 flowing through the metal wirings q1 and p1 are in opposite phases and have different amplitudes. Therefore, | I1 |-| I2 | is a current component contributing to radiation.

  Next, the operation of the dipole antenna A1 as a two-resonance antenna in the left-handed system will be described with reference to FIGS. 2a to 2e showing the relationship between the current distribution and the excitation mode. Here, the resonance order n, the excitation current wavelength λa, and the antenna length 2 (h + L) have a relationship of 2 (h + L) = | n | λa / 2.

  FIGS. 2A to 2E show distributions of current (| I1 | − | I2 |) when n = −1 to −5, respectively. 2A to 2E show distribution diagrams of the current | I1 |-| I2 |, the shape of the dipole antenna A1 is a U-shape on the yz plane in which the metal wirings p1 and q1 are represented by one. Represented as a figure. Accordingly, the line segments p1a and q1a of the extension 30 on the upper side in the z-axis direction in FIG. 1 are the line segment a in FIG. 2, and the line segments p1a and q1a of the extension 31 on the lower side in the z-axis direction are the line segments in FIG. b, line segments p1b and q1b of the base 10 in FIG. 1 correspond to the line segment c in FIG. Further, the circle mark of the line segment c indicates the position of the feeding point F.

  As shown in FIGS. 2A to 2E, the currents in the two parallel line segments a and b are opposite to each other. Therefore, when the length 2h of the line segment c is sufficiently smaller than the free space wavelength, they cancel each other and do not contribute to radiation. Further, as shown in FIGS. 2B and 2D, when n is an even number, the current is minimum at the position of the feeding point F, and the input impedance becomes a very large value. On the other hand, as shown in FIGS. 2A, 2C, and 2E, when n is an odd number, the current is maximized at the position of the feeding point F, and impedance matching can be achieved. Further, when n = −1 and n = −3, the current flowing through the line segment c which is the base portion 10 becomes a radiant wave source, and when n = −5, the current flowing through the line segment c of the base portion 10 has a component in the opposite direction. The amount is very small. As described above, the dipole antenna A1 is a two-resonance antenna that operates in two modes of n = −1 and n = −3.

  FIGS. 3A to 3C show simulation results for the current distribution when n = −1, −3, and −5. In the cone mark shown on the track, the apex direction of the cone represents the direction of current, and the size of the cone represents the strength of current. It can be confirmed that current flows as shown in FIGS. 2 (a), 2 (c) and 2 (e), respectively. The resonance frequency was 315 MHz when n = −1, 436 MHz when n = −3, and 398 MHz when n = −5. In general, in the left-handed system, | n | increases and the resonance frequency decreases, but in the dipole antenna A1, the resonance frequency decreases in the order of n = -3, n = -5, and n = -1. This is due to the inductor LSE1 provided to facilitate adjustment of the resonance frequency and impedance.

  4A and 4B are diagrams showing the relationship between the reflection amplitude, the reflection phase, and the frequency. From FIG. 4A, it can be confirmed that resonance is obtained at two frequencies of n = −1 (315 MHz) and n = −3 (436 MHz). On the other hand, from FIG. 4B, it can be confirmed that resonance appears at n = −1, −3, and −5. However, as described above, when n = −5, the current flowing through the line segment c of the base 10 also has a component in the opposite direction, so that the radiation is extremely small, and a resonance of n = −5 appears in FIG. Not.

  FIGS. 5A to 5D are diagrams showing directivity on the xy plane and the xz plane when n = −1 (315 MHz) and n = −3 (436 MHz). FIGS. 5A and 5C show the directivity on the xy plane, and it can be seen that both n = −1 and n = −3 are omnidirectional. FIGS. 5b and 5d show the directivity on the xz plane, and it can be seen that both n = −1 and n = −3 have an 8-character directivity having the maximum radiation direction in the x-axis direction. . From this, it can be confirmed that the current flowing through the line segment c (line segments q1b, p1b) is a radiation wave source.

  FIG. 6 is a plan view of the dipole antenna A2 according to the second embodiment. The dipole antenna A2 has two basic metal wirings p2 and q2 as a basic structure, and the metal wirings p2 and q2 are arranged in the xy plane. The dipole antenna A2 is on the base 20 extending in the polarization direction (y-axis direction) of the radiated radio waves of the metal wirings p2 and q2, and on the installation surface of the base 20 and bent in the direction of 90 degrees with respect to the base 20 Extension portions 40 and 41 formed in this manner. In the center of the base 2 of the metal wiring q2, a feeding point F including points FT and FB is provided. The metal wiring q2 has the same shape as the metal wiring q1. In other words, the shape has two 90-degree bent portions (21, 23) so as to be symmetric with respect to the symmetry axis L3 perpendicular to the y-axis passing through the feeding point F (a U-shaped shape). . The metal wiring p2 is disposed inside the metal wiring q2 with a gap d, and has a U-shape symmetrical with respect to the symmetry axis L3 having two 90 degree bent portions (22, 24). Therefore, the metal wiring q2 is longer than the metal wiring p2.

  The dipole antenna A2 is configured by connecting six substantially identical unit circuits. As in the case of the dipole antenna A1, the unit circuit is connected in series with two capacitors CSE1 connected in series on a part of the metal wiring p2 and two in series on a part of the metal wiring q2. Inductor LSE1 and a connecting portion for connecting metal wiring p1 and metal wiring q1 via inductor LSH1.

  The dipole antenna A2 can also be operated in a left-handed system by periodically arranging the capacitor CSE1 inserted on the metal wiring p2 and the inductor LSH1 inserted between the metal wiring p2 and the metal wiring q2. it can. In addition, the U-shaped shape of the metal wirings p2 and q2 can cancel the current component in the x-axis direction and prevent the reverse current component from being generated in the current component in the y-axis direction. Obtainable.

  In the first and second embodiments, the dipole antennas A1 and A2 are provided with the inductor LSE1 in order to facilitate the adjustment of the resonance frequency and impedance. However, even if the inductor LSE1 is not provided, the dipole antennas A1 and A2 are operated as a two-resonance antenna in the left-handed system. be able to.

  Further, the unit circuit is not limited to the configurations of the first and second embodiments, and the configuration shown in Patent Document 1 can be used. For example, like the unit circuit U2 shown in FIG. 7, the inductor LSE2 connected in series with the capacitor CSE2 on the metal wiring p3, or the capacitor CSH2 connected in parallel with the inductor LSH2 between the metal wirings p3 and q3 (this (The second capacitor of the invention). By providing the inductor LSE2 and the capacitor CSH2, the circuit design of the left-handed circuit becomes easy.

  In the dipole antennas A1 and A2, the capacitor CSE1 and the inductors LSE1 and LSH1 are configured using lumped constant elements, but the metal wirings p1 and q1 are conductor patterns, and the capacitor CSE1 is a comb-shaped interdigital capacitor pattern shown in FIG. A dipole antenna may be configured by forming Cp1 and Cp2 and inductors LSE1 and LSH1 as meander-shaped inductor patterns Lp shown in FIG. 9 and laminating them on a flexible substrate. Since it is a flexible substrate, a 90-degree bent portion can be easily formed, and a small two-resonance antenna used in the several GHz band can be realized at low cost.

  The dipole antenna A1 of this embodiment is formed using a multilayer printed wiring board. That is, as shown in FIG. 10, the metal wiring p1 and the capacitor CSE1 are formed on the front surface of the substrate 10 having a thickness d, the metal wiring q1 and the inductor LSE1 are formed on the back surface of the substrate, and the inductor LSH1 is formed in the through hole 11. The dipole antenna A1 can be configured.

  As shown in FIG. 11, the dipole antenna A <b> 1 may be configured on the side surface of the rectangular substrate 20.

  Further, if the inverted L-type antenna A3 shown in FIG. 12 in which half of the dipole antenna A1 divided into two with respect to the axis of symmetry is formed on the ground is used, a smaller two-resonance antenna can be obtained. This is because the dipole antenna A1 can be obtained by virtually forming a mirror image antenna having a ground surface as a mirror surface in the ground.

  In the dipole antenna A1 of Example 1, two resonance characteristics were obtained by setting the ratio of 2h and L to 1: 1, but if 2h: L = 1: 2, three resonance characteristics were obtained, and generally 2h: L = 1. : If n, n + 1 resonance characteristics can be obtained. The same applies to the dipole antenna A2 of the second embodiment.

  In addition, the present invention is not limited to the U-shape as in the first embodiment, and a 90-degree bent portion is formed so that each metal wiring is line-symmetric with respect to an axis of symmetry perpendicular to the metal wiring. It only has to be. With such a shape, it is possible to cancel the current other than the current in the z-axis direction as in the first embodiment and obtain a double resonance characteristic. For example, in the dipole antenna A4 shown in FIG. 13, metal wirings p4 and q4 having a U-shape and the same length are arranged on the xy plane with a distance d therebetween. The metal wiring p4 and the metal wiring q4 intersect at the portion B, but are insulated. The shape of the dipole antenna A4 is not symmetric as a whole, but the metal wirings p4 and q4 are symmetric in shape. Even in such a shape, the current components in the x-axis direction flowing through the metal wirings p4 and q4 cancel each other out so that no reverse direction component is generated in the current component in the y-axis direction, so that multiple resonance characteristics can be obtained. .

  In the first and second embodiments, the number of metal wirings is two. However, the number of metal wirings may be three or more.

  FIG. 14 shows a perspective view of a dipole antenna A5 according to Embodiment 7 of the present invention. The present embodiment is characterized in that a connection line 50 made of metal wirings r1 and s1 is provided on the extension portions 30 and 31 side in parallel to the base portion 10 with respect to the dipole antenna A1 of the first embodiment. However, unlike FIG. 1, among the metal wirings r1 and s1 constituting the connection line 50, a feeding point F including points FT and FB is provided at the midpoint of the metal wiring r1 in which the capacitor CSE1 is inserted in series. Yes.

This dipole antenna A5 comprises a dipole antenna using eight unit circuits of length a and width d. The unit circuit includes two series capacitors CSE1 in part of the metal wiring p1, two series inductors LSE1 in part of the metal wiring q1, and one parallel inductor LSH1 between the metal wiring p1 and the metal wiring q1. Have. Similarly, two series capacitors CSE1 are formed on a part of the metal wiring r1 constituting the connection line 50, two series inductors LSE1 are formed on a part of the metal wiring s1 constituting the connection line 50, and the metal wiring r1 and the metal wiring. One parallel inductor LSH1 is provided between s1.

  A feeding point F composed of the two points FT and FB is located substantially at the center of the metal wiring r1. The metal wirings p1 and q1 having a total length 6a have a “U” shape having two 90 ° bent portions (11, 12) and (13, 14). A pair of parallel extension portions 30 and extension portions 31 having a length 2a (twice the unit circuit) from both ends of the “U” -shaped metal wires p1 and q1 are arranged in the y-axis direction. . Further, the metal wiring of the base portion 10 having a length 2a between the extension portion 30 and the extension portion 31 is arranged in the z-axis direction that is the polarization direction of the radiated radio wave. The metal wirings r1 and s1 constituting the connection line 50 having a length 2a are arranged in the z-axis direction in parallel with the base 10, and the distance from the base 10 is a / 2. The lengths of the antenna A5 in the x, y, and z directions were set to d = 20 mm, L = 2a = 60 mm, and 2h = 2a = 60 mm, respectively.

  As in the first embodiment, this antenna operates in a left-handed system by the series capacitor CSE1 and the parallel inductor LSH1. The series inductor LSE1 is provided to adjust two resonance frequencies and impedance. The currents I1 and I2 flowing through the metal wirings q1 and p1 have opposite phases, and their amplitudes have different values. Therefore, the current amplitude difference | I1 |-| I2 | is a current component contributing to radiation.

  FIGS. 15A, 15B, and 15C show current distributions at frequencies of 335 MHz, 407 MHz, and 451 MHz. The direction of the arrow on the metal wiring indicates the direction of the current, and the magnitude indicates the strength of the current. When the height 2h of the antenna is sufficiently smaller than the free space wavelength, the currents in the x and y axis components cancel each other and thus do not contribute to radiation. The current contributing to radiation becomes the z-axis component. The current flowing through the metal wirings q1 and p1 of the base 10 is in the opposite direction. Similarly, the current flowing through the metal wires s1 and r1 of the connection line 50 is also directed in the opposite direction. In FIG. 15, the current flowing through the metal wiring q1 of the base 10 in the z-axis direction and the metal wiring s1 of the connection line 50 is further indicated by arrows. At 335 MHz and 451 MHz, the currents flowing through the metal wirings q1 and s1 are in the same direction. Therefore, strong radiation is generated and radiation resistance is increased. On the other hand, at 407 MHz, the current flowing through the metal wirings q1 and s1 is in the opposite direction. The radiation is therefore very small.

  The amplitude and phase of the impedance are shown in FIGS. 16 (a) and 16 (b), respectively. From the amplitude distribution normalized to 20Ω in FIG. 16A, it can be confirmed that resonance is obtained at two frequencies of 335 MHz and 451 MHz. The radiation resistance is 14Ω and 25Ω, respectively. On the other hand, from the phase distribution of FIG. 16B, it can be confirmed that resonance appears at frequencies of 335 MHz, 407 MHz, and 451 MHz. The reason why resonance does not appear in the amplitude distribution at 407 MHz is that, as described above, the current component in the z direction is canceled and the radiation becomes extremely small.

  17A to 17D show the directivities of the xy plane and the yz plane at frequencies of 335 MHz and 451 MHz. 17A and 17C show that both frequencies are omnidirectional on the xy plane. 17B and 17D, it can be seen that, on the yz plane, both frequencies have an 8-shaped directivity having the maximum radiation direction in the y-axis direction. In addition, the directivity on the zx plane was similar to the characteristics shown in FIGS. 5 (b) and 5 (d). From this, it can be confirmed that the current flowing through the metal wiring in the z-axis direction (base 10 and connection line 50) is a radiation wave source.

  A perspective view of the dipole antenna A6 according to the eighth embodiment of the present invention is shown in FIG. In the dipole antenna A5 of the seventh embodiment, the power feeding portion F is provided in the approximate center of the metal wiring r1 on the side where the capacitor CSE1 of the connection line 50 is inserted. In the dipole antenna A6 of the eighth embodiment, the feeding point F is provided at the approximate center of the metal wiring p1 of the base 1. Other configurations are the same as those of the seventh embodiment.

FIG. 19 shows a perspective view of the dipole antenna A7 according to the ninth embodiment of the present invention. In the dipole antenna A7 according to the ninth embodiment, the distance between the metal wirings p1 and q1 of the base 10 arranged in the z-axis direction and the metal wirings r1 and s1 of the connection line 50 arranged in the z-axis direction is a distance. The point a is different from the seventh embodiment. Other configurations are the same as those of the seventh embodiment.

  Since the connection line 50 is provided in parallel to the base 10 as in the seventh, eighth, and ninth embodiments, the impedance viewed from the antenna side in the power feeding unit F can be increased. Impedance matching can be achieved. As a result, power efficiency is improved.

  As shown in FIG. 20, the dipole antennas A5, A6 and A7 are configured in the same manner as in the fifth embodiment shown in FIG. The monopole antenna A8 may be formed so as to be symmetric with respect to the ground conductor. According to this configuration, an even smaller antenna can be configured. That is, the connection line 50 is also erected on the ground conductor in parallel with the base 10.

[Modification]
In the dipole antennas A5, A6 and A7, the series inductor LSE1 is loaded in order to easily adjust the resonance frequency and impedance. .

  In the dipole antennas A5, A6 and A7, the capacitor CSE1 and the inductors LSH1 and LSE1 which are lumped constants are loaded on the metal wiring. However, as shown in FIGS. 8 and 9, the metal wiring is a conductor pattern, and the capacitor CSE1 is a comb-shaped. The interdigital capacitor pattern and the inductors LSH1 and LSE1 may be laminated on a flexible substrate or the like as a meander-shaped inductor pattern. As shown in FIG. 7, a capacitor CSE2 and an inductor LSE2 are connected in series to a metal line p1 and a line r1 of a connection line 50, the metal lines q1 and s1 are only conductor lines, and a connection portion between the metal lines p1 and q1 and a metal You may provide the parallel connection circuit of capacitor CSH2 and inductor LSH2 in the connection part of track | line r1 and s1.

  In the first embodiment, the power feeding unit F is provided on the metal wiring q1 on the side where the inductor LSE1 is inserted, but may be provided on the metal wiring p1 side on which the capacitor CSE1 is inserted.

  In addition, in the dipole antennas A5, A6 and A7, the ratio of 2h to L is 1: 1 and two resonance characteristics are obtained. However, the length L of the extension portions 30 and 31 is set to be longer than the length 2h of the base portion 10. By increasing the value, characteristics of 3 resonances or more can be obtained. In order to satisfy this, it is sufficient that no antiphase component is present in the current in the z direction.

  Although the dipole antennas A5, A6 and A7 have been described as two-resonance antennas, it goes without saying that they can be used as one-resonance antennas.

  Further, for the dipole antennas A5, A6, and A7 of Examples 7 and 9, the metal wiring p1, the metal wiring r1, and the capacitor CSE1 are arranged on the surface of the substrate 10 as in Example 3 shown in FIG. A dipole antenna may be configured by disposing the metal wiring q1, the metal wiring s1, and the inductor LSE1, and forming the inductor LSH1 in the through hole 11.

  6 and 13, an antenna provided with a connection line 50 in parallel with the base 10 may be used.

  The present invention can be applied to an antenna used in a smart entry system that is an in-vehicle application.

FIG. 3 is a perspective view illustrating a configuration of a dipole antenna A1 according to the first embodiment. The figure which shows the electric current distribution in each resonance order of the dipole antenna A1 of Example 1. FIG. The figure which shows the current distribution in n = -1, -3, -5 of the dipole antenna A1 of Example 1. FIG. The figure shown about the relationship of the reflection amplitude of the dipole antenna A1 of Example 1, and a reflection phase, and a frequency. The figure which shows the directivity in n = -1 and -3 of the dipole antenna A1 of Example 1. FIG. The top view which shows the structure of the dipole antenna A2 of Example 2. FIG. The figure which shows the structure of the unit circuit U2. The figure which shows the interdigital capacitor pattern of a comb shape. The figure which shows a meander-shaped inductor pattern. The perspective view which shows the example which formed the dipole antenna of Example 3 in the board | substrate. The perspective view which shows the example which formed the dipole antenna of Example 4 in the board | substrate side surface. The figure which shows the inverted L type antenna which concerns on the dipole antenna A3 of Example 5. FIG. FIG. 10 is a plan view showing the configuration of a dipole antenna A4 according to Example 6. The perspective view which shows the structure of the dipole antenna A5 of Example 7. FIG. The figure which shows the current distribution in each resonance order of the dipole antenna A5 of Example 7. The figure shown about the reflection amplitude of the dipole antenna A5 of Example 7, the relationship between a reflection phase, and a frequency. The figure which shows the directivity in n = -1 and -3 of the dipole antenna A5 of Example 7. FIG. FIG. 10 is a plan view showing a configuration of a dipole antenna A6 of Example 8. The top view which shows the structure of the dipole antenna A7 of Example 9. FIG. FIG. 10 is a plan view showing a configuration of a dipole antenna A7 in Example 10. The top view which shows the structure of the dipole antenna A10 which operate | moves with the conventional left-handed system.

A1, A2, A3, A4: Dipole antenna p1, q1, p2, q2, r1, s1: Metal wiring F: Feed point CSE1, CSH1: Capacitor LSH1: Inductor 10: Base 30, 31: Extension 50: Connection line

Claims (19)

A dipole antenna constituted by arranging a plurality of parallel metal wirings as a basic structure and connecting a plurality of identical or similar unit circuits in a row in the direction of the metal wirings,
The unit circuit is
A connecting portion for connecting the metal wirings to each other via at least one first inductor;
And at least one first capacitor inserted on at least one of the metal wirings,
Each said metal wiring is
A base portion, bent in a direction of 90 degrees with respect to the base portion, passed through a central portion of the plurality of metal wirings constituting the base portion, and formed of metal wiring lines symmetrical with respect to a symmetry axis perpendicular to each. A pair of extensions
Have
The ratio between the length of the base and the length of one of the pair of extensions is 1: n (n is a positive integer),
A dipole antenna characterized by being able to resonate at two or more frequencies . 2. The dipole antenna according to claim 1, wherein the value of n is 1. The dipole antenna according to claim 1 or 2, wherein the resonable frequency exists in a 300 MHz band to a 400 MHz band. The dipole antenna according to any one of claims 1 to 3 , wherein a continuous body of the base and the pair of extension portions has a U-shape. 5. The dipole antenna according to claim 1 , wherein the axis of symmetry is perpendicular to an arrangement surface constituted by the plurality of metal wirings constituting the base portion. 5. The dipole antenna according to claim 1 , wherein the axis of symmetry is located in an arrangement surface constituted by the plurality of metal wirings constituting the base portion. 6. 1/2 region of the length of the base solid portion of said base is erected on the ground conductor, one of the extension portion is disposed parallel to said ground conductor, said base, said is constituted by a base solid portion and a mirror image of said base solid portion, a pair of said extensions, said the one of the extensions, claims 1 to, characterized in that it is constituted by a mirror image of the extended portion 7. The folded antenna according to any one of items 6 . Consists of one or more of said unit circuits are arranged in parallel to the base, according to any one of claims 1 to 6, characterized in that it has a connection line connected to the extension portion Dipole antenna. The base actual part, which is a half of the length of the base , and the connection line actual part, which is a half of the length of the connection line , are erected on a ground conductor. The one extension is disposed in parallel to the ground conductor, the base is constituted by the base real part and a mirror image of the base real part, and the connection line is connected to the connection line real part. The folded portion according to claim 8 , further comprising: a mirror image of the real part of the connection line, wherein the pair of extension portions includes the one extension portion and a mirror image of the extension portion. antenna. The dipole antenna according to any one of claims 1 to 9 , wherein a feeding point is provided at the base. The dipole antenna according to claim 8 or 9 , wherein a feeding point is provided in the connection line.   12. Each of the unit circuits is composed of the same circuit, and each of the unit circuits is periodically arranged in the direction of the metal wiring and connected to each other. 2. The dipole antenna according to item 1.   The dipole antenna according to any one of claims 1 to 12, wherein both ends of each metal wiring are open ends.   14. The unit circuit includes a second inductor inserted in series on another metal wiring different from the metal wiring in which the first capacitor is disposed. The dipole antenna according to any one of the above.   15. The dipole antenna according to claim 1, wherein the communication unit of the unit circuit includes a second capacitor connected in parallel to the first inductor. .   The dipole antenna according to any one of claims 1 to 15, wherein the inductor includes a meander-shaped inductor pattern.   The dipole antenna according to any one of claims 1 to 16, wherein the capacitor includes a comb-shaped interdigital capacitor pattern.   The dipole antenna according to any one of claims 1 to 17, wherein the capacitor and the inductor are configured by a lumped constant element. It has a flexible board on which conductor patterns are laminated,
The inductor is
It is composed of a meander-shaped inductor pattern made of the conductor pattern,
The capacitor is
It is composed of a comb-shaped interdigital capacitor pattern made of the conductor pattern,
The dipole antenna according to any one of claims 1 to 18, wherein the dipole antenna is provided.

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