JP2009278356A - Antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain a flat antenna which is constituted of a single dielectric substrate, whose manufacturing process is easy, and whose operation frequency range is wide. <P>SOLUTION: In the antenna 100, an EBG 10 is arranged adjacent to both sides along the longitudinal direction of a radiator 102 on the same surface of that of the radiator 102, and formed by periodically arranging metal layers in the predetermined shapes. Furthermore, a grounding electrode 104 consists of a metal layer, and is arranged so as to cover the whole surface or approximately the whole surface of an area equivalent to the rear surface side in the area where the radiator 102 and the EBG 10 are arranged on the other surface of the dielectric substrate 101. Then the EBG 10 is set so as to cause resonance to be high impedance in a resonance frequency of the radiator 102. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an antenna formed on a plate-like dielectric.

  Conventionally, there is a patch antenna as a typical structure of a planar antenna. A patch antenna uses a rectangular or circular metal pattern with dimensions that resonate in a high-frequency signal to be transmitted and received on one surface of a dielectric substrate as a radiator, and a metal film formed on the back surface of the substrate is a ground electrode. It is the structure used as. As described above, since the general patch antenna has the ground electrode on the back surface, the radio wave exhibits directivity directed toward the front surface (front surface) of the antenna.

  Also, thanks to the ground electrode, the antenna radiating element is shielded even if it is attached directly to the metal casing of the mobile device, so that it operates correctly. Taking advantage of this feature, patch antennas are often used for applications in which radio waves are transmitted and received in the front direction of an antenna by being attached to the surface of a device or installed on a wall surface.

  On the other hand, the patch antenna uses a resonance phenomenon of a metal electrode formed on a dielectric substrate, and steep resonance occurs due to an electric field confinement phenomenon from a short part of the metal electrode toward the dielectric. As a result, the resonating band, that is, the frequency band capable of operating as an antenna becomes narrow.

  By the way, in combination with an antenna, as a technology for suppressing unnecessary radiation of the antenna and reducing the size, there is a structure called HIP (high impedance plane), PBG (photonic band gap) or EBG (electromagnetic band gap). Yes (for example, see Patent Document 1 and Patent Document 2). Note that HIP, PBG, and EBG basically indicate the same structure, and thus are represented as EBG as a representative in this specification.

  As an example of EBG, as disclosed in Patent Document 1, a dielectric substrate is used, a metal patch periodically disposed on the surface, a ground electrode disposed on the back surface, and a metal on the surface provided on each patch. A so-called mushroom structure formed by a via hole connecting the patch and the ground electrode on the back surface is known.

  In this EBG, it is known that an equivalent circuit of a periodic structure has a characteristic in which an inductor L and a capacitor C are connected in series, and these LCs have a high impedance due to series resonance, and take this high impedance. The frequency band is called the band gap.

  As a combination of an EBG and a patch antenna, Patent Document 1 discloses a technique for combining a curl antenna obtained by processing a metal wire into a spiral shape and an EBG to make a planar antenna having a high gain. When the EBG is used at a band gap frequency, the impedance of the EBG surface is high, so that even if the EBG is grounded in the vicinity of the curl antenna, the antenna operates correctly without preventing the current flowing in the metal wire from being interrupted by the EBG. As a result, the EBG can efficiently reflect radio waves and improve the gain of the antenna.

Further, in this prior art, since a metal wire is used for the radiating element, there are advantages that the resonance strength is generally smaller than that of the patch antenna and the operating frequency band is wide.
As another example, Patent Document 2 discloses a technique for operating the EBG structure itself as an antenna by directly feeding power to a structure similar to the EBG. This prior art also has the effect of extending the operating frequency range of the antenna.

Thus, a conventional technique for forming a planar antenna that can be used in a wide frequency range is known.
On the other hand, wireless communication systems using these antennas can be broadly classified into a form in which a base station and a mobile station communicate with each other, and a form in which mobile stations directly communicate with each other, and different antenna characteristics are required for each.

  The form of communication between the base station and the mobile station includes data distribution for mobile information terminals such as mobile phones, automobile fee billing systems, communication for commercial mobile units, and the like. TVs and radios are also broadcasts, but they also use antennas. In addition, GPS and satellite telephones using artificial satellites are also a kind of this form. In these systems, the base station often installs an antenna at a relatively high position in consideration of the ease of radio wave flight. Therefore, since the mobile station that receives them needs to receive radio waves coming from above and transmit radio waves upward, the mobile station antenna must have a vertical beam facing upwards. Is required.

On the other hand, as an example of a form in which mobile stations directly communicate with each other, there is use of inter-vehicle communication in which wireless communication is performed between vehicles. Here, FIG. 18 shows a usage form of inter-vehicle communication. The inter-vehicle communication device mounted on the automobile 201 communicates with surrounding vehicles using wireless communication, and exchanges the positions of the vehicles with each other. Based on the exchanged information, the inter-vehicle communication device prevents an accident by detecting and warning a vehicle having a risk of collision, such as a vehicle in the shadow (dead zone) of the building 202, for example. In this case, the vehicle such as the automobile 201 needs to communicate mainly with the front and rear vehicles, and it is desirable that the horizontal antenna beam has a strong gain in the front-rear direction. In addition, on the vertical plane, for example, when the antenna is mounted on the roof of a car, it is preferable to have a strong gain in the front-rear horizontal direction, not the zenith. That is, since the antenna used for vehicle-to-vehicle communication is located at the same height as itself, especially in the vertical plane beam characteristics, the antenna beam characteristics (for example, 203) different from the form in which the base station and mobile station communicate with each other. The directivity shown in Fig. 1 is required.
JP2007-235460A JP2007-104211

  Extending the usable frequency range of the antenna allows a single antenna to use a plurality of frequency channels and a plurality of systems, and the use range is wide. However, the conventional technique disclosed in Patent Document 1 has a structure in which a metal wire and an EBG are stacked, and thus it is necessary to manufacture a plurality of dielectric substrates and processed metal wires, which complicates the manufacturing process. There is a problem.

  In this regard, Patent Document 2 has a merit that it can be easily configured in a general printed circuit board manufacturing process because it has a structure in which metal layers are arranged on the front and back of a single dielectric substrate. However, there is a problem that the method of feeding the antenna is a differential feeding, and the connection with a general electronic circuit is complicated.

  Further, the technique of Patent Document 2 has a characteristic that the direction in which the antenna beam is emitted is strongest in the direction orthogonal to the antenna plane. This characteristic may not be preferable depending on the application using the antenna. In other words, when this antenna is mounted on the roof of an automobile, for example, the beam characteristics are suitable for communication with a base station or an artificial satellite, but when a strong gain is required in the horizontal direction, such as inter-vehicle communication. Has the problem of becoming unsuitable.

  In view of these problems, an object of the present invention is to realize a planar antenna having a structure with a simple manufacturing process and a wide operating frequency range, which is formed of a single dielectric substrate. In addition, it is an object to realize a desired beam even in response to a request for an antenna beam pattern that varies depending on the application of the antenna.

  In order to achieve this object, the antenna according to claim 1 is configured by including a radiator, a periodic structure, and a back-side metal layer on a plate-shaped dielectric. The radiator includes a connection portion to which wiring from an external device is connected, and is configured from a metal layer disposed on one surface of the dielectric and formed in a band shape.

And the periodic structure is arrange | positioned adjacent to the both sides along the longitudinal direction of a radiator on the same surface as a radiator, and forms the metal layer of a predetermined shape periodically. further,
The back surface side metal layer is made of a metal layer, and is disposed on the other surface of the dielectric so as to cover the entire surface or substantially the entire surface corresponding to the back surface side in the region where the radiator and the periodic structure are disposed. . The periodic structure is set so as to cause a resonance with a high impedance at the resonance frequency of the radiator.

  That is, in the present invention, first, an elongated strip-shaped metal is used for the antenna radiation element (radiator). This is because a band-like metal is expected to have a wider band than a patch antenna when used in a radiating element, like a metal wire that is a conventional technique. However, when a band-shaped metal is simply arranged on the dielectric as a radiating element and a ground electrode is arranged on the back surface, an image current in the direction opposite to the current of the radiating element is excited on the back surface electrode and does not operate as an antenna. For this reason, the technique of Patent Document 1 further solves this problem by arranging an EBG below the linear antenna (on the opposite side to the radio wave transmission direction) to suppress the image current.

  On the other hand, in the present invention, the EBG structure is arranged adjacent to the strip-shaped metal radiation element in the same plane. Conventionally, the idea of disposing the EBG structure as in the present invention has not been disclosed, but the present inventor has an image current suppressing effect even with the disposition of the present invention, and can make the radiation element operable. Because it was proved.

  The reason why the effect of enabling operation of the radiating element in the configuration of the present invention can be considered as follows. That is, the current flowing through the patch-like radiator (see FIG. 1C) is diffused throughout the radiator, and the current direction at that time is difficult to be defined in one direction, whereas it is formed in a band shape. The current flowing through the radiator (see FIG. 1B) is easily defined in one direction.

  For this reason, it is expected that the magnetic field generated by the current flowing through the radiator formed in a belt shape is uniformly generated in a certain direction. Here, in the present invention, since the EBG is disposed adjacent to the radiator, it is considered that this magnetic field can be effectively cut off (see FIG. 1A). In the patch-shaped radiator, the radiator itself has a wide shape, so the direction of the magnetic field is not uniform. Further, even if the EBG is disposed close to the radiator, the central portion of the radiator cannot be brought close to the EBG. Therefore, it is considered that the radiator formed in a band shape can effectively block the generated magnetic field more than the patch-shaped radiator.

  In the conventional technology, the patch-type radiator is made thin (or the dielectric constant is increased) to increase the resonance strength of the patch (Q is increased). There is also known a method in which the flowing current is aligned in one direction without spreading. However, it is known that increasing Q has the side effect of narrowing the operating frequency band. On the other hand, in the band-shaped radiator, the current direction can be aligned without increasing the Q, so that the frequency band can be widened. Also from this point, it is effective to use a belt-like radiator.

However, the “strip shape” as used in the present invention refers to a shape in which the direction of current in the radiator is generally defined in one direction. The back side metal layer acts as a shield.
With this structure, it is possible to operate a strip-shaped metal radiating element with a structure using a single dielectric layer, and to realize a structure in which a ground electrode is arranged on the back surface like a patch antenna. it can. As a result, the antenna can be easily manufactured with a well-known printed circuit board manufacturing technique, and can be applied directly to a metal casing as with a patch antenna. Thus, an operating frequency band wider than that of the patch antenna can be obtained.

  By the way, in the antenna according to claim 1, the periodic structure has an inductor component and a capacitance component that are periodically formed as described in claim 2, and LC resonance occurs when resonating. It may be set to wake up.

  According to such an antenna, since the periodic structure has a structure exhibiting high impedance by causing LC resonance, the periodic structure can be realized by the conventional EBG, and the resonant frequency can be realized by using the conventional EBG design method. Can be calculated and designed.

  In the antenna according to claim 1 or 2, the antenna can have a so-called monopole structure or a dipole structure. First, when the antenna has a monopole structure, it may be configured as described in claims 3 to 5, for example.

  That is, as in the antenna according to claim 3, the radiator has a connection portion at one end and the other end is in an open state. It may be set to (2n-1) / 4 times the wavelength in the line at the resonance frequency of the device (where n is a natural number).

  According to such an antenna, the radiator can be efficiently resonated at a desired frequency. Moreover, since a connection part can be comprised by one point (one place), a coaxial cable etc. can be connected easily, for example.

  Further, in the antenna according to claim 3, as described in claim 4, the antenna is made of one or a plurality of metals arranged on the same plane as the radiator with a periodic structure separated from the radiator. A parasitic element may be provided.

  According to such an antenna, the radiating element and the parasitic element are electromagnetically coupled, and a current flows through the parasitic element, so that the parasitic element becomes a radiation source in addition to the radiator. And it becomes possible to change the direction of an antenna beam by arrange | positioning the impedance and position of a parasitic element appropriately.

  Further, in the antenna according to claim 4, the parasitic element is formed by a band-shaped metal layer arranged in parallel to the radiator as described in claim 5, and one of the metal layers is formed. The end portion may be connected to the back side metal layer by a metal connecting member, and the other end portion of the metal layer may be in an open state.

  According to such an antenna, the entire antenna functions as a monopole antenna as a Yagi Uta antenna. As a result, the Yagi-Uta antenna design method, which is a well-known technique, can be applied. For example, by setting the length of the parasitic element to be shorter than that of the radiating element, it is possible to act as a waveguide in which the antenna beam faces the parasitic element side. it can. Conversely, by setting the length of the parasitic element longer than that of the radiating element, it is possible to act as a reflector in which the antenna beam is directed to the opposite side of the parasitic element.

Next, when the antenna has a dipole structure, it may be configured as described in claims 6 to 9, for example.
That is, like the antenna according to claim 6, the radiator is composed of two strip-shaped metal layers arranged in a straight line, and wirings connected to an external device are provided at the ends of the metal layers on the sides close to each other. Each of the power supply units to be connected is provided, and the total length of each metal layer in the radiator is (2n-1) / 2 times the wavelength in the line at the resonance frequency of the radiator (where n is a natural number). ) Should be set.

  According to such an antenna, a dipole antenna that has been widely used in the past can be realized as a planar antenna. In addition, since this antenna can operate in a state where the back side metal layer is covered with another metal layer, an installation method in which the antenna is directly attached to a metal housing or the like is also possible.

  In the antenna according to claim 6, as described in claim 7, the parasitic element made of one or more metals arranged on the same plane as the radiator with the periodic structure separated from the radiator is provided. An element may be provided.

According to such an antenna, the effect of controlling the antenna beam pattern by the parasitic element can be realized in the dipole antenna.
In the antenna described in claim 7, as described in claim 8, the parasitic element is formed of a band-shaped metal layer, and both ends may be open.

  According to such an antenna, the well-known Yagi Uta antenna can be configured as a planar antenna. Therefore, it is possible to apply the Yagi-Uta antenna design technique, such as changing the length of the parasitic element to act as a director or a reflector.

  In the antenna according to any one of claims 6 to 8, as described in claim 9, each power feeding unit in the radiator is configured to be differentially fed with phases opposite to each other. Also good.

According to such an antenna, power can be efficiently supplied to the dipole antenna.
Furthermore, in the antenna according to any one of claims 1 to 9, the back-side metal layer is set to a ground potential as viewed from the device that feeds power to the antenna as described in claim 10. It may be.

According to such an antenna, it becomes possible to share the ground potential with the device connected to the antenna, and to suppress the influence of unnecessary radiation and noise on the antenna and the device.
Note that, depending on a circuit to which the antenna is connected, the integrated circuit (IC) can be used for the purpose of directly connecting to the antenna.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 2 is a plan view and a cross-sectional view showing the basic structure of the monopole antenna 100 of the first embodiment. 2A is an explanatory diagram showing back surface feeding, which is a connection method in which wiring from an external device (transmitter / receiver or receiver) is connected to the back surface of the dielectric substrate 101, and FIG. It is explanatory drawing which shows the side surface electric power feeding which is a connection method in which an external apparatus is connected to the side surface of the dielectric substrate.

  In the monopole antenna 100 of the present embodiment, as shown in FIGS. 2A and 2B, a radiator 102 made of a band-shaped metal is disposed at the center of the surface of the dielectric substrate 101. And the structure of EBG10 (periodic structure) was arrange | positioned in the same plane as the radiator 102, and the both sides of the radiator 102. FIG.

  The EBG structure will be described in detail later. The EBG 10 may be disposed at least in regions on both sides in the longitudinal direction of the radiator 102, but may be disposed so as to surround the periphery of the radiator 102. FIG. 2B shows an example in which the EBG 10 surrounds three sides of the radiator 102.

  Next, on the back surface of the dielectric substrate 101, the ground electrode 104 (back surface side metal layer) was disposed almost entirely. The ground electrode 104 is made of a metal layer and is disposed so as to cover at least the entire region corresponding to the back side of the region where the radiator 102 and the EBG 10 are disposed.

  In particular, in the back surface power feeding shown in FIG. 2A, a power feeding portion 103 (connecting portion) is provided at one end of the radiator 102. In the power feeding unit 103, a hole was made in the dielectric substrate 101, and the dielectric substrate 101 was connected to the radiator 102 through the core wire of the coaxial cable 105 from the back surface. Further, the outer conductor of the coaxial cable 105, that is, the ground conductor, was connected to the ground electrode 104 on the back side of the power feeding unit 103.

  In addition, as shown in FIG. 2B, in the side feeding, the radiator 102 is shifted from the edge of the substrate so that the feeding unit 103 comes to the end of the dielectric substrate, and the coaxial cable 105 is arranged from the side of the substrate. And the core wire of the coaxial cable 105 may be connected to the radiator 102, and the outer conductor of the coaxial cable 105 may be connected to the ground electrode 104.

  Here, the operating frequency of the monopole antenna 100 can be set by adjusting both the length of the radiator 102 and the resonance frequency of the EBG 10. Specifically, since the ground electrode 104 on the back surface, the dielectric substrate 101, and the radiator 102 on the front surface constitute a microstrip line, the ratio of the dielectric substrate 101 is determined based on various parameters such as the shape of these components. It is possible to calculate the in-line wavelength considering the dielectric constant.

For example, the length of the radiator 102 resonates at a length of (2n-1) / 4 times the wavelength in the line (where n is a natural number, for example, 3/4 times).
For EBG 10, a design method for obtaining a resonance frequency from an equivalent inductor component L and capacitance component C is known. In each antenna in this specification, the surface of the EBG 10 is set to have a high impedance at the LC series resonance frequency.

  More precisely, the EBG structure is analyzed by an electromagnetic field simulator, the reflection phase on the EBG surface is calculated, and the frequency band in which this phase falls within the range of −90 degrees to +90 degrees is adjusted to the operating frequency of the antenna. Use it.

  A more detailed embodiment of the EBG 10 is shown in FIG. FIG. 3 shows the shape of a unit metal structure (EBG unit cell) formed on the surface (first conductive layer) of the dielectric substrate 101. In the EBG 11 of the band-like cell, unit cells are periodically arranged in the horizontal direction of the paper, and show EBG characteristics, but the vertical direction of the paper is a continuous metal and operates as a normal metal band. The EBG 11 is a kind of so-called one-dimensional EBG.

  The square cell EBG 12 is a two-dimensional EBG exhibiting EBG characteristics in any direction in the plane. Furthermore, the hexagonal cell EBG 13 is also a two-dimensional EBG similar to 12 although the unit cell has a hexagonal shape. Here, all of the EBGs 11 to 13 are formed with via holes 25 arranged at a specific interval P, and the via unit electrically connects the unit cell on the front surface and the ground electrode 104 on the back surface. ing.

  In these EBGs, the gap portion where the unit cells face each other is a capacitance component C, and the connection portion between the unit cell and the via hole acts as an inductor component L to create the characteristics of the EBG.

  As another EBG embodiment, an EBG 14 having a uniplanar structure may be used. This EBG produces L and C components only with the metal layer on the surface. Therefore, an EBG can be formed without providing a via hole.

  Among these EBGs, more detailed structures of the EBG 11 of the strip cell, the EBG 12 of the square cell, and the EBG 13 of the hexagonal cell combined with the monopole radiator 102 are shown in FIGS.

  In the monopole antenna 111 (Example 1) shown in FIG. 4, among the EBGs of the band-like cells, the direction serving as the EBG is arranged so as to be parallel to the monopole radiator 102. Further, in the monopole antennas 112 (example 2) and 113 (example 3) shown in FIGS. 5 and 6, the relationship between the rectangular and hexagonal cell arrangement and the radiator 102 is shown as an example.

  In order to evaluate the performance of the first embodiment of the present invention as an antenna, the frequency dependence of the reflection loss of the antenna was compared. The result is shown in FIG. This result is obtained by modeling each antenna structure and calculating the characteristics using electromagnetic field analysis software widely used in antenna design. It has been confirmed that the calculated value is almost the same as the actual antenna.

  Here, in this analysis, in addition to the antennas 111, 112, and 113 shown in FIGS. 4 to 6, a patch antenna 119 that is a known technique shown in FIG. 8 was used for comparison. These antennas all use a common dielectric substrate 101.

  Specifically, the size of the dielectric substrate 101 is 60 × 60 × 3.2 mm, and the relative dielectric constant is 2.6. In 111, 112, and 113, the length of the radiator 102 is Le = 22.5 mm, the width of the radiator is We = 2.0 mm, and the distance Ge between the radiator and the EBG is 0.4 mm. These are all designed to resonate at a frequency in the 5-6 GHz band. The patch antenna 119 studied for comparison was also designed to resonate at 5.5 GHz.

  From the results shown in FIG. 7, it can be seen that in each antenna, a region where the reflection loss is low is observed, and the antenna resonates and operates correctly without reflection of radio waves. Comparing the frequency range in which the reflection loss is smaller than −10 dB, which is a guideline for the operating frequency band, it can be seen that the operating frequency range of all of the antennas 111, 112, and 113 is wider than that of the patch antenna 119 of the prior art. . Thus, it was confirmed that the antenna of the present invention can surely exhibit the effect of widening the operating frequency, which is one of the problems.

  As described above, the antenna structure can be configured by simply forming a pattern on the surface of a single dielectric substrate and providing a via hole as needed in the portion constituting the EBG. This structure can be easily manufactured by the printed circuit board manufacturing method.

(Effect by 1st Embodiment)
In the antennas 100 and 111 to 113 described in detail above, the radiator 102, the EBG 10, and the ground electrode 104 are formed on the dielectric substrate 101 formed in a plate shape. The radiator 102 includes a power feeding unit 103 to which wiring (coaxial cable 105 or the like) from an external device (transmitter / receiver or receiver) is connected. The radiator 102 is disposed on one surface of the dielectric substrate 101 and formed in a band shape. It is composed of a metal layer.

  And EBG10 is arrange | positioned adjacent to the both sides along the longitudinal direction of the radiator 102 in the same surface as the radiator 102, and the metal layer of a predetermined shape is arranged side by side periodically. Further, the ground electrode 104 is made of a metal layer, and is disposed on the other surface of the dielectric substrate 101 so as to cover the entire surface or substantially the entire surface corresponding to the back surface side in the region where the radiator 102 and the EBG 10 are disposed. ing. The EBG 10 is set so as to cause resonance with high impedance at the resonance frequency of the radiator 102.

  That is, in this embodiment, the EBG structure is arranged adjacent to the strip-shaped metal radiator 102 in the same plane. Conventionally, the idea of disposing the EBG structure as in the present invention has not been disclosed, but the present inventor has an image current suppression effect even with the disposition of the present invention, and enables the radiation element to operate. It was proved that it was possible.

  The reason why the effect of enabling operation of the radiating element in the configuration of the present invention can be considered as follows. That is, the current flowing through the patch-shaped radiator (see FIG. 1C) is diffused throughout the radiator, and its direction is difficult to be defined in one direction, whereas the radiator 102 formed in a band shape ( In the current flowing through FIG. 1B, the direction of the current in the radiator 102 is easily defined in one direction.

  For this reason, it is expected that the magnetic field generated by the current flowing through the radiator 102 formed in a band shape is uniformly generated in a certain direction. Here, in the present invention, since the EBG 10 is disposed adjacent to the radiator 102, it is considered that this magnetic field can be effectively blocked (see FIG. 1A). In the patch-shaped radiator, the radiator itself has a wide shape, so the direction of the magnetic field is not uniform. Further, even if the EBG 10 is disposed close to the radiator, the central portion of the radiator cannot approach the EBG. Therefore, it is considered that the radiator 102 formed in a strip shape can more effectively block the generated magnetic field than the patch-shaped radiator.

However, the “strip shape” as used in the present invention refers to a shape in which the direction of current in the radiators 102 and 107 is generally defined in one direction. The ground electrode 104 acts as a shield.
With this structure, it is possible to operate a band-shaped metal radiating element with a structure using a single dielectric substrate 101 layer, and a ground electrode is disposed on the back surface in the same manner as the patch antennas 100 and 111 to 113. Can be realized. As a result, the antennas 100 and 111 to 113 can be easily manufactured by a widely known printed circuit board manufacturing technique. An operating frequency band wider than that of the patch antennas 100 and 111 to 113 can be obtained by the effect of the band-shaped metal.

  In the antennas 100 and 111 to 113, the EBG 10 has an inductor component and a capacitance component that are periodically configured, and is set to cause LC resonance when resonating.

  According to such antennas 100 and 111 to 113, since the EBG 10 has a structure exhibiting high impedance by causing LC resonance, the EBG 10 can be realized by the conventional EBG, and is resonated by using a conventional EBG design method. The frequency can be calculated and designed.

  Further, in the antennas 100 and 111 to 113, the radiator 102 includes the power feeding unit 103 at one end, and the other end is in an open state. The length of the radiator 102 is radiated. It is set to (2n-1) / 4 times the wavelength in the line at the resonance frequency of the capacitor 102 (where n is a natural number).

  According to such antennas 100 and 111 to 113, the radiator 102 can be efficiently resonated at a desired frequency. Further, since the power feeding unit 103 can be configured at one point (one place), for example, the coaxial cable 105 or the like can be easily connected.

Further, in the antennas 100 and 111 to 113, the ground electrode 104 is set to the ground potential as viewed from a device that supplies power to the antennas 100 and 111 to 113.
According to such antennas 100 and 111 to 113, the ground potential is shared by the devices connected to the antennas 100 and 111 to 113, and the influence of unnecessary radiation and noise on the antennas 100, 111 to 113 and the devices is suppressed. It becomes possible.

Note that, depending on a circuit connecting the antennas 100 and 111 to 113, the integrated circuit (IC) can be used for the purpose of directly connecting the antennas 100 and 111 to 113.
(Second Embodiment)
FIG. 9 shows an antenna 110 with parasitic elements according to a second embodiment of the present invention. In this embodiment, a parasitic element is newly added to the configuration of the first embodiment. In the following description of the second embodiment, the description will focus on parts that are different from the first embodiment.

  In the antenna 110 with parasitic elements in this embodiment, as shown in the plan view of FIG. 9, in addition to the monopole radiator 102 common to the first embodiment, the parasitic elements 106 are arranged in parallel therewith. In the present embodiment, as shown in the AA sectional view of FIG.

  As shown in the BB cross-sectional view of FIG. 9, the parasitic element-equipped antenna 110 is electrically connected to the parasitic element 106 at one end thereof to the ground electrode 104 on the back surface by a via hole. Further, the other end of the parasitic element 106 is in an open state.

  EBGs 10 are arranged on the left and right sides of these parasitic elements 106. That is, the parasitic element 106 is arranged with the EBG 10 arranged adjacent to the radiator 102 being spaced apart, and the EBG 10 (unit cell constituting the EBG 10) is also adjacent to both sides along the longitudinal direction of the parasitic element 106. Are arranged side by side.

  Further, in this embodiment, the parasitic element 106 is set slightly shorter than the radiator 102 and is arranged in parallel with the radiator so that it acts as a waveguide of the Yagi Uta antenna of the prior art, and the side where the parasitic element is present The antenna beam was controlled to increase the antenna gain.

  In the structure of the antenna with parasitic elements 110 shown in FIG. 9, the feeding of the coaxial cable 105 is feeding from the back side of the substrate (backside feeding). However, as described in the first embodiment, the coaxial cable 105 is fed. A method of feeding power by connecting to the side of the substrate (side feeding) may be used.

  More specific examples according to this embodiment are shown in FIGS. An antenna 114 shown in FIG. 10 is a first example of the second embodiment, and uses an EBG 11 of a band cell. Moreover, the antenna 115 shown in FIG. 11 is a 2nd example, and uses EBG13 of a hexagonal cell.

In each example, the radiator 102 is arranged in the center, the EBG is arranged on both sides thereof, and the parasitic element 106 is arranged on the side thereof. Further, an EBG is also arranged beside the parasitic element 106.
For the second embodiment shown in FIGS. 10 and 11, the frequency dependence of the reflection loss of the antenna was also analyzed. FIG. 12 shows a calculation example. This calculation result was also simulated by using the widely used electromagnetic field analysis software by modeling the antenna structure.

  In the analyzed embodiment, a dielectric substrate 101 having a size of 60 × 60 × 3.2 mm and a relative dielectric constant of 2.6 was used for both the antennas 114 and 115. The length of the radiator 102 is Le = 22.5 mm, the width is We = 2.0 mm, the length of the parasitic element 106 is Lp = 19.5 mm, and the width is We = 2.0 mm. The distance between the radiator and the parasitic element and the EBG is Ge = Gp = 0.5 mm, and the distance between the radiator and the parasitic element is Dp = 14.8 mm.

  The antenna 114 of Example 1 shows a reflection loss of −6 dB in the range of 5.0 to 5.5 GHz, and it can be seen that resonance occurs although it is weak. It was found that the antenna of 115 in Example 2 has strong resonance, and a range in which the reflection loss is −10 dB or less around 5.8 GHz is obtained at 500 MHz or more. Thus, when it is desired to take a wide operating frequency range, the structure of Example 2 may be used. Although the operating frequency range is slightly narrower than that without the parasitic element 106, as shown by 119 in FIG. It can be seen that a wide frequency can still be obtained as compared with a patch antenna using conventional technology.

  Here, the feature of the second embodiment is that the beam pattern of the antenna can be controlled by the parasitic element 106. Therefore, the inventors actually made a prototype of the antenna and measured its beam pattern.

  FIG. 13 shows an antenna beam pattern measurement method. The antenna gain is obtained by placing the prototype antenna in the anechoic chamber, transmitting the reference signal from the reference antenna installed in the darkroom, receiving the reference signal with the prototype antenna, and measuring the received power intensity. Was measured. In this state, the antenna was rotated to determine the change in gain in each direction, and the pattern of the antenna beam was measured. This time, the horizontal polarization gain Gφ was measured in the vertical plane (z-x plane), and the horizontal polarization gain Gφ and the vertical polarization gain Gθ were measured in the horizontal plane (xy plane).

  An example of measured data is shown in FIG. Here, the beam patterns of the antenna 113 of the first embodiment / example 3 shown in FIG. 6 and the antenna 115 of the second embodiment / example 2 shown in FIG. 10 were compared. These are monopole antennas using hexagonal cell EBGs, 113 having no parasitic elements, and 115 having parasitic elements 106 arranged on both sides of the radiator.

  Looking at the gain on the vertical plane (z-x plane) shown in FIG. 14A, in the case where the parasitic element is arranged, the gain in the direction where the parasitic element is present, that is, the direction of ± 90 degrees, is not present in the parasitic element. It can be seen that it is about 10 dB higher than. Further, this tendency appears also in the data on the horizontal plane (xy plane) shown in FIG. 14B. When the parasitic elements are arranged, the gains in the directions of 0 degrees and 180 degrees do not have the parasitic elements. It is higher than

  Also, it is confirmed that the vertical polarization gain Gθ shown in FIG. 14C is higher in the region where the parasitic elements are arranged, in the region close to 0 degree and 180 degrees than that without the parasitic elements. did it. The beam pattern control using this parasitic element is performed, for example, when the antenna is disposed on the ceiling of an automobile and the x-axis is set in the forward direction in FIG. Close to the required beam pattern. That is, it can be seen that the vertical plane has a strong front-rear horizontal gain, and the horizontal plane has a strong front-rear gain.

(Effect by 2nd Embodiment)
The antennas 114 and 115 described in detail above include one or more metal parasitic elements 106 arranged on the same plane as the radiator 102 with the EBG 10 being spaced from the radiator 102.

  According to such antennas 114 and 115, the radiating element and the parasitic element 106 are electromagnetically coupled and a current flows through the parasitic element 106, so that the parasitic element 106 in addition to the radiator 102 also serves as a radiation source. Then, by appropriately arranging the impedance and position of the parasitic element 106, the beam directions of the antennas 114 and 115 can be changed.

  In the antennas 114 and 115, the parasitic element 106 is formed by a band-shaped metal layer arranged in parallel to the radiator 102, and one end of the metal layer is formed by the metal power feeding unit 103. While being connected to the ground electrode 104, the other end of the metal layer is opened.

  According to such antennas 114 and 115, the antennas 114 and 115 as a whole function as a monopole antenna Yagi Uta antenna. As a result, the Yagi-Uta antenna design method, which is a known technique, can be applied. For example, by setting the length of the parasitic element 106 to be shorter than that of the radiating element, the waveguide in which the beams of the antennas 114 and 115 are directed toward the parasitic element 106 Can act as Conversely, by setting the length of the parasitic element 106 to be longer than that of the radiating element, it is possible to act as a reflector in which the beams of the antennas 114 and 115 are directed to the side opposite to the parasitic element 106.

(Third embodiment)
FIG. 15 shows an antenna 120 with parasitic elements according to the third embodiment. This embodiment is an example in which the basic configuration is the same as that of the second embodiment, but there is only one parasitic element 106. The configuration of the radiator, the parasitic element, the power feeding method, and the like are the same as those in the second embodiment, and are omitted.

  Here, if the length of the parasitic element 106 is set slightly shorter than that of the radiator 102, it acts as a director of the Yagi Uta antenna and controls the beam so that the antenna gain on the side where the director is located becomes high. Can do.

  Furthermore, in this embodiment, the design theory of the conventional Yagi Uta antenna and array antenna can be applied to the effect of the parasitic element. Therefore, the parasitic element is set longer than the radiator and used as a reflector, opposite to the reflector. It is also possible to increase the gain in the direction, or to increase the gain in the front direction by using a parasitic element having the same length as the radiator. That is, an appropriate beam pattern can be obtained according to the application.

(Fourth embodiment)
FIG. 16 shows a dipole antenna 130 of the fourth embodiment. This embodiment has the same basic configuration as that of the first embodiment except that the radiator 107 is not a monopole but a dipole antenna. The radiator 107 is formed as a band-shaped metal on the dielectric substrate 101 substrate 101, but is composed of two separate bands, and the power feeding unit 103 is provided on each of the inner sides.

  The power feeding unit 103 may be differentially fed so that the phases are opposite to each other, as is widely done with dipole antennas of the prior art. More specifically, as shown in FIG. 16A, a method of performing differential power feeding using two coaxial cables may be used.

  Further, when an antenna is directly connected to an IC or a high-frequency integrated module that integrates the functions of a radio device, the IC antenna output terminal is directly connected to the terminal of the dipole radiator 107 as shown in FIG. May be.

  As is well known in the art, the length of radiator 107 is such that the total length of both radiators 107 is (2n−1) / 2 times the in-line wavelength of the radio wave at the antenna operating frequency (where n Is a natural number (for example, 1/2 times). Moreover, the structure of EBG10 should just use the structure similar to 1st Embodiment, and should just match the resonant frequency of EBG with the operating frequency of an antenna.

(Effect by 4th Embodiment)
In the antenna 130 described in detail above, the radiator 107 is composed of two strip-shaped metal layers arranged in a straight line, and wirings connected to an external device are connected to the ends of the metal layers on the sides close to each other. Each of the power supply units 103 is provided, and the total length of each metal layer in the radiator 107 is (2n−1) / 2 times the in-line wavelength at the resonance frequency of the radiator 107 (where n is a natural number). ) Is set.

  According to such an antenna 130, the dipole antenna 130 that has been widely used conventionally can be realized as a planar antenna. In addition, since the antenna 130 can operate in a state where the ground electrode 104 is covered with another metal layer, an installation method in which the antenna 130 is directly attached to a metal housing or the like is also possible.

(Fifth embodiment)
FIG. 17 shows an antenna 131 of the fifth embodiment. This embodiment implements a structure similar to the widely known Yagi Uta antenna. The structure of the radiator is a dipole structure, which is the same as that of the fourth embodiment. Therefore, the power feeding method can be the same as that in the fourth embodiment.

  In the antenna 131 of this embodiment, on the dielectric substrate 101, in addition to the radiator 107, the reflector 141 and the waveguide 142 are formed on the same plane using the same first conductive layer as the radiator 107. . EBGs 10 are disposed between and on both sides of the radiator 107, the reflector 141, and the waveguide 142. The reflector 141 and the director 142 are band-shaped metal, and both ends are opened.

(Effect by 5th Embodiment)
The antenna 131 includes a waveguide 142 which is one or more metal parasitic elements arranged on the same plane as the radiator 107 with the EBG 10 being spaced from the radiator 107. In the antenna 131, the director 142 is formed of a band-shaped metal layer, and both ends are open.

According to such an antenna 131, the effect of controlling the antenna beam pattern by the director 142 can be realized in a dipole antenna.
According to such an antenna 131, a well-known Yagi Uta antenna can be configured as a planar antenna. Therefore, the design method of the Yagi Uta antenna can be applied, for example, by changing the length of the director 142 so as to act as a director or a reflector.

  Further, by taking this form, it becomes possible to concentrate the antenna beam sharply in the direction of the director 142. In the example of this embodiment, each of the directors / reflectors has one configuration. However, as in the case of the conventional Yagi Uta antenna, a plurality of directors are arranged and guided. It is also possible to further concentrate the antenna beam in the direction of the vessel and narrow the beam narrowly.

  In this case, the EBG may be disposed between the plurality of waveguides disposed on the side of the waveguide positioned at the tip. By adopting this structure, an antenna having an effect equivalent to that of the Yagi-Uta antenna can be realized even with a planar antenna structure.

Further, in the antenna 131, each feeding unit 103 in the radiator 107 is configured to be differentially fed with phases opposite to each other.
According to such an antenna 131, it is possible to efficiently supply power to the dipole antenna.

It is explanatory drawing which shows the principle of invention. It is the top view and sectional drawing which show the basic structure of the monopole antenna 100 of 1st Embodiment. It is the top view and sectional drawing which show the more detailed embodiment of EBG10. It is a top view which shows embodiment which employ | adopted EBG11 of the strip | belt-shaped cell in 1st Embodiment. It is a top view which shows embodiment which employ | adopted square cell EBG12 in 1st Embodiment. It is a top view which shows embodiment which employ | adopted EBG13 of the hexagonal cell in 1st Embodiment. It is a graph which shows the calculation result of the frequency dependence of the reflection loss in each antenna shown in a 1st embodiment. It is a top view which shows the patch antenna 119 which is a well-known technique. It is the top view and sectional drawing which show the antenna 110 with a parasitic element of 2nd Embodiment. It is a top view which shows embodiment which employ | adopted EBG11 of the strip | belt-shaped cell in 2nd Embodiment. It is a top view which shows embodiment which employ | adopted EBG13 of the hexagonal cell in 2nd Embodiment. It is a graph which shows the calculation result of the frequency dependence of the reflection loss in each antenna shown in a 2nd embodiment. It is explanatory drawing which shows the measuring method of an antenna beam pattern. It is explanatory drawing which shows the measurement result of an antenna beam pattern. It is the top view and sectional drawing which show the antenna 120 with a parasitic element of 3rd Embodiment. It is the top view and sectional drawing which show the dipole antenna 130 of 4th Embodiment. It is the top view and sectional drawing which show the antenna 131 of 5th Embodiment. It is a bird's-eye view which shows the utilization form of vehicle-to-vehicle communication.

Explanation of symbols

  10-14 ... EBG, 25 ... via hole, 100,110-115,119,120,130,131 ... antenna, 101 ... dielectric substrate, 102 ... radiator, 103 ... feeding part, 104 ... ground electrode, 105 ... coaxial Cable 106 106 Parasitic element 107 Radiator 141 Reflector 142 Wave director 201 Automobile

Claims (10)

A radiator comprising a metal layer formed in a strip shape, disposed on one surface of a plate-shaped dielectric, having a connection portion to which wiring from an external device is connected;
A periodic structure that is arranged adjacent to both sides along the longitudinal direction of the radiator on the same surface as the radiator, and is formed by periodically arranging metal layers having a predetermined shape;
On the other surface of the dielectric, a back surface side metal layer comprising a metal layer covering the entire surface or substantially the entire surface corresponding to the back surface side in the region where the radiator and the periodic structure are disposed;
With
The antenna is characterized in that the periodic structure is set so as to cause a resonance having a high impedance at a resonance frequency of the radiator. The antenna according to claim 1, wherein
The periodic structure has an inductor component and a capacitance component that are periodically configured, and is configured to cause LC resonance when resonating. The antenna according to claim 1 or 2,
The radiator includes the connecting portion at one end, and the other end is in an open state.
The antenna is characterized in that the length of the radiator is set to (2n-1) / 4 times the wavelength in the line at the resonance frequency of the radiator (where n is a natural number). The antenna according to claim 3,
An antenna comprising one or more metal parasitic elements arranged on the same plane as the radiator with the periodic structure being spaced apart from the radiator. The antenna according to claim 4, wherein
The parasitic element is formed by a band-shaped metal layer arranged in parallel to the radiator, and one end of the metal layer is connected to the back-side metal layer by a metal connecting member. And the other end of the metal layer is in an open state. The antenna according to claim 1 or 2,
The radiator is composed of two strip-shaped metal layers arranged in a straight line, and each of the metal layers includes a power feeding unit to which a wiring connected to an external device is connected to an end portion on the side close to each other,
The total length of each metal layer in the radiator is set to (2n-1) / 2 times the wavelength in the line at the resonance frequency of the radiator (where n is a natural number). Antenna. The antenna according to claim 6,
An antenna comprising one or more metal parasitic elements arranged on the same plane as the radiator with the periodic structure being spaced apart from the radiator. The antenna according to claim 7, wherein
The antenna is characterized in that the parasitic element is formed of a band-shaped metal layer, and both ends are open. The antenna according to any one of claims 6 to 8,
The antenna is characterized in that differential feeding is performed on each feeding section of the radiator in opposite phases. The antenna according to any one of claims 1 to 9,
The antenna, wherein the back side metal layer is at a ground potential as viewed from a device that feeds power to the antenna.