JP5557652B2 - Antenna structure and array antenna - Google Patents

Description

  The present invention relates to an antenna structure and an array antenna used in a communication system and a radar system using microwaves and millimeter waves.

  In recent years, with the advent of advanced information technology, it has been studied that the frequency of radio waves used for information transmission is from the microwave region of 1 GHz to 30 GHz to the millimeter wave region of 30 GHz to 300 GHz. Application systems such as an in-home high-speed wireless transmission system (wireless PAN: Personal Area Network) using 60 GHz radio waves have also been proposed.

  In such an application system, particularly when the frequency is as high as 60 GHz or the like, the attenuation of radio waves increases and directivity also occurs. Therefore, in the wireless communication system, it is necessary to improve the characteristics of the antenna element that radiates radio waves. For example, by arranging an array of antenna elements in a planar direction to increase the antenna gain so that radio waves can be propagated further away, and the phase of the signal input to the arrayed antenna The phased array antenna that can be scanned without using a mechanical mechanism and can propagate in a wide area even when the radiation pattern has directivity has been put to practical use.

  In addition, in a wireless PAN using radio waves with a frequency of 60 GHz, communication using a wide frequency band is being studied in order to transmit a large amount of data such as a high-definition video. Broadband characteristics are required.

  As an antenna having a wide band characteristic, a dielectric resonator antenna as disclosed in Patent Document 1 has been studied.

  In the dielectric resonator antenna described in Patent Document 1, during transmission, a high-frequency signal from the high-frequency circuit 21 is input to the space (dielectric) resonator unit 8 via the slot 9, and radio waves are radiated from the opening 4. Is done. The dielectric resonator 8 functions as an (impedance) matching device between the high-frequency circuit 21 and the slot 9 and the space above the opening 4, and the radiation of the high-frequency signal to the space becomes good, and the frequency characteristic becomes a wide band.

Japanese Patent Laid-Open No. 11-239017

  However, when the frequency of the radiated high-frequency signal is increased to 60 GHz or the like, the antenna characteristics of the aperture antenna described in Patent Document 1 deteriorate due to the influence of the upper main conductor layer 3 such that the gain of the high-frequency signal radiated from the antenna decreases. Resulting in.

  An object of the present invention is to provide an antenna structure and an array antenna that can improve antenna characteristics when a high-frequency signal having a relatively high frequency is used.

The present invention provides a dielectric substrate comprising a plurality of dielectric layers;
A surface conductor layer provided on one main surface of the dielectric substrate and having a rectangular opening for transmitting and receiving a high-frequency signal, extending parallel to the magnetic field direction of the high-frequency signal to be transmitted and received, and having a length in an electric field direction The width dimension is a pair of strip conductors that are ¼ or less of the free space wavelength of the high-frequency signal to be transmitted and received, and the pair of connection conductors that connect adjacent ends of the pair of strip conductors A surface conductor layer in which an opening is defined;
A plurality of through conductors penetrating the dielectric layer in the thickness direction, electrically connected to the surface conductor layer, and a through conductor provided circumferentially along the opening at a predetermined interval; and
A power supply electrically connected to the through conductor on a side opposite to the surface conductor layer, wherein a slot is formed in a region surrounded by the through conductor and facing a resonance region formed so that the high frequency signal resonates. The slot layer,
An antenna structure comprising: a feeding line that electromagnetically couples to the slot and transmits a high-frequency signal for feeding power to the resonance region.

In the present invention, the through conductor is provided in a plurality of dielectric layers,
An internal conductor layer that connects through conductors provided in different dielectric layers in the thickness direction and connects through conductors provided in the same dielectric layer in the surface direction, and formed in the surface conductor layer It further includes an internal conductor layer in which an opening similar to the opening is formed.

The present invention also includes a plurality of the antenna structures described above,
An array antenna characterized in that the antenna structures are arranged in an array.

  According to the present invention, the surface conductor layer is provided on one main surface of the dielectric substrate, and the surface conductor layer transmits a high frequency signal to the external space and receives a high frequency signal from the external space. A rectangular opening is formed. The opening is defined by a pair of strip conductors and a connection conductor connecting the ends of the strip conductors.

The pair of strip conductors extends parallel to the magnetic field direction of the high-frequency signal transmitted and received through the opening, and the width dimension which is the length in the electric field direction is ¼ or less of the free space wavelength of the high-frequency signal transmitted and received.

As a result, when a high frequency signal having a relatively high frequency is used, a decrease in gain in the traveling direction of the high frequency signal to be transmitted and received can be suppressed, and the antenna characteristics can be improved. Further, by making the width dimension of the strip-shaped conductor equal to or less than ¼ of the free space wavelength of the high-frequency signal to be transmitted and received, the occurrence of side lobes can be suppressed. In particular, in an array antenna having a plurality of antenna structures, side lobes affect the antenna characteristics of adjacent antenna structures, so the distance between antenna structures can be shortened by suppressing the occurrence of side lobes. The array antenna can be downsized.

  According to the invention, the through conductor is provided in a plurality of dielectric layers, and connects the through conductors provided in different dielectric layers in the thickness direction, and the through conductor provided in the same dielectric layer. An internal conductor layer is provided for connecting the conductors in the plane direction. An opening similar to the opening formed in the surface conductor layer is formed in the inner conductor layer.

  Thereby, the through conductors can be reliably connected to each other, and leakage of a high-frequency signal that resonates in the resonance region can be suppressed.

  According to the invention, there is provided an array antenna having a plurality of the antenna structures described above, wherein the antenna structures are arranged in an array. Thereby, it is possible to provide an array antenna excellent in antenna characteristics in which a decrease in gain is suppressed. In particular, when the width of the strip-shaped conductor is set to ¼ or less of the free space wavelength of the high-frequency signal to be transmitted and received, the generation of side lobes can be suppressed, so that further miniaturization is possible.

It is sectional drawing which shows the structure of the antenna structure 1 which is embodiment of this invention. 1 is a plan view of an antenna structure 1. FIG. 1 is a plan view of an array antenna 10. FIG. It is a figure which shows an example of the radiation pattern obtained by simulation. It is a graph which shows the influence which it has on the gain and side lobe of a radiation direction when Wa is changed.

  FIG. 1 is a cross-sectional view showing a configuration of an antenna structure 1 according to an embodiment of the present invention. FIG. 2 is a plan view of the antenna structure 1.

  The antenna structure 1 includes a dielectric substrate 2, a surface conductor layer 3, a through conductor 4, an internal conductor layer 5, a feed slot layer 6, and a feed line 7.

  When the antenna structure 1 transmits radio waves, for example, a high-frequency signal output from a high-frequency semiconductor element propagates through the feed line 7 and passes through the slot provided in the feed slot layer 6, the surface conductor layer 3, The light is radiated from an opening formed in the surface conductor layer 3 through a resonance region surrounded by the through conductor 4, the inner conductor layer 5, and the feed slot layer 6. When receiving radio waves, the radio waves are received through the openings formed in the surface conductor layer 3, and the high frequency signal reaches the feed line 7 in the reverse flow to that in the case of transmission.

  The dielectric substrate 2 includes a plurality of dielectric layers 2a, the surface conductor layer 3 is formed on one main surface, the feed line 7 is formed on the other main surface, and the dielectric layers 2a are interposed between the plurality of dielectric layers 2a. The inner conductor layer 5 and the feed slot layer 6 are formed, and the through conductor 4 is formed so as to penetrate the dielectric layer 2a.

  The surface conductor layer 3 includes a pair of strip-shaped conductors 3a having a predetermined width and a pair of connecting conductors 3b that connect both ends of the strip-shaped conductor 3a. Become. Although details of the surface conductor layer 3 will be described later, it is important to define the width dimension Wa of the strip-shaped conductor 3a in the antenna structure 1 of the present embodiment.

  Moreover, the opening formed in the surface conductor layer 3 becomes a radiation part in the antenna structure 1 of the present embodiment, and is, for example, an opening having a vertical dimension a and a horizontal dimension b. This opening size is determined according to the frequency of the high-frequency signal to be transmitted / received.

  The through conductor 4 is connected to the surface conductor layer 3, passes through the plurality of dielectric layers 2 a, and is connected to the power supply slot layer 6. The through conductors 4 are provided circumferentially at predetermined intervals along the opening. The interval between the through conductors 4 is set to be less than ½ of the effective wavelength of the resonating high-frequency signal, and preferably to ¼ or less of the effective wavelength so that the resonating high-frequency signal does not leak.

  The internal conductor layer 5 is provided between the dielectric layers 2a, connects the through conductors 4 provided in different dielectric layers 2a in the thickness direction, and connects the through conductors 4 provided in the same dielectric layer 2a in the plane direction. Connect to. In the inner conductor layer 5, openings having the same dimensions (a × b) as the openings formed in the surface conductor layer 3 are formed and provided between the respective layers of the dielectric layer 2a. Therefore, if the distance from the surface conductor layer 3 to the feed slot layer 6, that is, the thickness of the dielectric layer 2 a between the surface conductor layer 3 and the feed slot layer 6 is c, the resonance region A of a × b × c is It is formed.

  Here, the thickness c may be set to be ¼ of the effective wavelength of the high-frequency signal transmitted through the resonance region A. The vertical dimension a of the opening 3c is preferably set to ¼ to ¾ of the wavelength in the free space of the high-frequency signal to be transmitted.

  The feed slot layer 6 is a conductor layer in which a slot 6a facing the resonance space is formed, and the slot 6a is electromagnetically coupled to the end of the feed line 7 with the dielectric layer 2a interposed therebetween. The high-frequency signal transmitted through the feed line 7 is fed to the resonance region A through the electromagnetically coupled slot 6a, resonates in the resonance region A, and is radiated from the opening of the surface conductor layer 3 to the external space.

  The slot 6a formed in the feed slot layer 6 may be provided so as to be electromagnetically coupled to the feed line 7 and the resonance region A. For example, the shape of the slot 6a is such that the longitudinal direction is the feed line 7 and the resonance region A. The rectangular shape is parallel to the magnetic field direction of the high-frequency signal that transmits the signal, and the slot 6a is provided inside the opening 3c when viewed through the top surface. The longitudinal dimension of the slot 6a is preferably not less than 1/2 of the effective wavelength of the high-frequency signal to be transmitted in the dielectric layer 2a and not more than 1/2 of the wavelength in the free space of the high-frequency signal to be transmitted.

  The feed line 7 is a transmission line that transmits a high-frequency signal for feeding power to the resonance region A, and various transmission lines such as a strip line, a microstrip line, a hollow waveguide, and a dielectric laminated waveguide are used. it can. In the present embodiment, a part of the feed slot layer 6 is a ground conductor, and a microstrip line that transmits a signal line provided on the surface on the back surface side is configured.

  The surface conductor layer 3 will be described in detail below. As described above, the surface conductor layer 3 includes a pair of strip conductors 3a and a pair of connection conductors 3b that connect both ends of the strip conductor 3a, and the rectangular conductor 3a and the connection conductor 3b form a rectangular opening 3c. Is defined.

  The strip-shaped conductor 3a extends in parallel with the magnetic field (H) direction of the high-frequency signal to be transmitted and received, and the length in the electric field (E) direction, that is, the width dimension Wa is less than ½ of the free space wavelength of the high-frequency signal to be transmitted and received. . By making the width dimension Wa less than half of the free space wavelength of the high-frequency signal to be transmitted and received, it is possible to suppress a decrease in gain in the traveling direction of the high-frequency signal to be transmitted and received.

  In an antenna structure using a conventional dielectric resonator such as the antenna described in Patent Document 1, there is a problem that the gain is lowered particularly at a relatively high frequency exceeding 60 GHz. The inventors of the present application have found that the decrease in gain is caused by the surface conductor layer, and have found that the decrease in gain can be suppressed by defining the width dimension Wa of the strip-shaped conductor 3a as described above.

Furthermore, the width dimension Wa is set to ¼ or less of the free space wavelength of the high-frequency signal transmitted and received . Thereby, generation | occurrence | production of a side lobe can be suppressed. The generation of side lobes not only causes a loss of radiant energy but also affects adjacent antennas in the array antenna and causes antenna characteristics to deteriorate. Therefore, when side lobes occur, it is necessary to increase the distance between adjacent antennas to such a distance that the influence of side lobes is reduced.

  When an array antenna is configured by arranging a plurality of antenna structures 1 according to the present embodiment, the occurrence of side lobes is suppressed, so the distance between adjacent antennas can be shortened, and the array antenna can be downsized. it can.

  FIG. 3 is a plan view of the array antenna 10. The array antenna 10 has a configuration in which a plurality of antenna structures 1 are regularly arranged in the plane direction. For example, the antenna structures 1 are arranged in a lattice pattern as shown in FIG. In the antenna structure 1, the width dimension Wa of the strip-shaped conductor 3a is set to 1/4 or less of the free space wavelength of the high-frequency signal to be transmitted / received, thereby shortening the distance between the adjacent antenna structures 1 and further reducing the size. The array antenna 10 can be realized.

  Moreover, it is preferable that the width dimension Wa of the strip | belt-shaped conductor 3a is larger than the diameter of the penetration conductor 4, for example. Since the through conductor 4 and the strip-shaped conductor 3a need to be electrically connected, if the width dimension Wa is equal to or smaller than the diameter of the through conductor 4, a manufacturing problem such as insufficient connection occurs, which affects the antenna characteristics. Therefore, by making the width dimension Wa larger than the diameter of the through conductor 4, it is possible to suppress deterioration of the antenna characteristics.

  The connection conductor 3b extends orthogonally to the strip conductor 3a and connects adjacent ends of the pair of strip conductors 3a. It has been confirmed that the width dimension Wb, which is the length in the magnetic field (H) direction, of the high-frequency signal to be transmitted and received does not affect the antenna characteristics of the antenna structure 1. In consideration of downsizing when configured, Wb is preferably as small as possible. Considering connection with the through conductor 4, the width dimension Wb of the connection conductor 3b is, for example, not less than the diameter of the through conductor 4 and not more than the width dimension Wa of the strip conductor 3a.

  In the antenna structure 1 of the present embodiment, as the material of the dielectric layer 2a, an organic resin material, a ceramic material, a mixed material of resin and ceramics, or the like can be used. As the organic resin material, for example, an epoxy resin and a polyimide resin can be used. As the ceramic material, a metal oxide such as alumina, a nitride such as silicon nitride, a carbide such as silicon carbide, and a glass material can be used.

  Each conductor material such as the surface conductor layer 3 and the through conductor 4 may be appropriately selected according to the material of the dielectric layer 2a to be used, and a metal material such as Ag, Cu, Al, or W can be used.

  The antenna structure 1 of the present embodiment can be manufactured, for example, as follows. First, an appropriate organic solvent is added to the ceramic raw material powder, and these are mixed to produce a slurry, and a ceramic green sheet having a predetermined thickness is formed by a doctor blade method.

  Next, a through hole for forming a through conductor is formed on the obtained ceramic green sheet using a punching machine or the like, and a conductive paste containing a conductive material such as Cu or W is filled. Further, the same conductive paste as described above is applied to the surface of the ceramic green sheet by using a printing method to produce a ceramic green sheet with a conductive paste. Next, these ceramic green sheets with a conductive paste are laminated in a predetermined order, and are bonded using a hot press apparatus, and fired at a peak temperature of about 800 ° C. to 1600 ° C. depending on the material of the dielectric layer 2a. It is produced by.

  About the antenna characteristic of the antenna structure 1 of this embodiment, it evaluated based on the radiation pattern obtained by simulation. The model of the antenna structure used for the simulation is as follows.

  The dielectric substrate 2 was assumed to be alumina as the material of the dielectric layer 2a, and the relative dielectric constant was about 9. The thickness of the dielectric layer 2a was 0.1 mm, and five dielectric layers 2a were stacked.

Each conductor material was assumed to be a tungsten alloy, and the conductivity was about 10 × 10 ⁶ [S / m].

  In the surface conductor layer 3, the width dimension Wa of the strip-shaped conductor 3a was changed to 0.15 mm to 3 mm, and the width dimension Wb of the connection conductor 3b was set to 0.15 mm. The outer dimensions of the surface conductor layer 3 are 3.3 mm in length and 1.8 mm in width when the width Wa of the strip-shaped conductor 3a is 0.15 mm, and the opening dimensions of the opening 3c are 3 mm in length and 1.5 mm in width. did.

  The slot 6a of the power supply slot layer 6 is 1.3 mm in length and 0.2 mm in width, and the diameter of the through conductor 4 is 0.1 mm.

  The feed line 7 has a line width of 0.1 mm, the high-frequency signal to be transmitted has a frequency of 61.5 GHz, and the thickness of the dielectric layer 2a provided with the line conductor 7 and the feed slot layer 6 on both sides is 0. 1 mm.

  FIG. 4 is a diagram illustrating an example of a radiation pattern obtained by simulation. 4A shows a radiation pattern when Wa is 1.0 mm, and FIG. 4B shows a radiation pattern when Wa is 1.5 mm. The wavelength in the free space of the high frequency signal having a frequency of 61.5 GHz is about 4.88 mm. Therefore, when Wa is 1.0 mm, Wa is ¼ or less of the free space wavelength, and Wa is 1.5 mm. In this case, Wa exceeds 1/4 of the free space wavelength and is less than 1/2. The radial direction indicates the radiant energy intensity, and the circumferential direction indicates an angle (0 ° is a radio wave radiation direction). Therefore, a value at 0 ° indicates a gain in the radial direction, and a value near ± 90 ° indicates a side lobe.

  The gain in the radial direction is not affected by the change in Wa, but the side lobe is clearly reduced by changing Wa from 1.5 mm to 1.0 mm.

  FIG. 5 is a graph showing the influence on the gain and side lobe in the radial direction when Wa is changed. 5A, the horizontal axis indicates Wa [mm], the vertical axis indicates the radial gain [dB], and in FIG. 5B, the horizontal axis indicates Wa [mm], and the vertical axis indicates The side lobe amount [dB] is shown. The side lobe amount is a value obtained by subtracting the side lobe gain from the radial gain. The larger the value of the gain in the radiation direction, the better the antenna characteristics, and the smaller the value of the side lobe amount, the better the antenna characteristics.

  As can be seen from the graph of FIG. 5A, the gain is greatly reduced when Wa is 2.44 mm compared to when Wa is 2 mm. That is, the gain did not decrease when Wa was 2/5 of the free space wavelength, and the gain decreased when Wa was 1/2 of the free space wavelength. For this reason, it is preferable that the width dimension Wa of the strip-shaped conductor 3a is less than ½ of the free space wavelength. When Wa was 2 mm or less, the gain was a substantially constant value.

  As can be seen from the graph of FIG. 5B, when Wa exceeds 1.22 mm, which is a quarter of the free space wavelength of the high-frequency signal, the side lobe amount increases as Wa increases, and Wa is the high-frequency signal. Below ¼ of the free space wavelength, the side lobe amount is substantially constant and kept small.

DESCRIPTION OF SYMBOLS 1 Antenna structure 2 Dielectric board | substrate 2a Dielectric layer 3 Surface conductor layer 3a Strip | belt-shaped conductor 3b Connection conductor 3c Opening 4 Through conductor 5 Internal conductor layer 6 Feed slot layer 6a Slot 7 Feed line 10 Array antenna

Claims (3)

A dielectric substrate comprising a plurality of dielectric layers;
A surface conductor layer provided on one main surface of the dielectric substrate and having a rectangular opening for transmitting and receiving a high-frequency signal, extending parallel to the magnetic field direction of the high-frequency signal to be transmitted and received, and having a length in an electric field direction The width dimension is a pair of strip conductors that are ¼ or less of the free space wavelength of the high-frequency signal to be transmitted and received, and the pair of connection conductors that connect adjacent ends of the pair of strip conductors A surface conductor layer in which an opening is defined;
A plurality of through conductors penetrating the dielectric layer in the thickness direction, electrically connected to the surface conductor layer, and a through conductor provided circumferentially along the opening at a predetermined interval; and
A power supply electrically connected to the through conductor on a side opposite to the surface conductor layer, wherein a slot is formed in a region surrounded by the through conductor and facing a resonance region formed so that the high frequency signal resonates. The slot layer,
An antenna structure comprising: a feeding line that electromagnetically couples to the slot and transmits a high-frequency signal for feeding power to the resonance region. The through conductor is provided in a plurality of dielectric layers,
An internal conductor layer that connects through conductors provided in different dielectric layers in the thickness direction and connects through conductors provided in the same dielectric layer in the surface direction, and formed in the surface conductor layer The antenna structure according to claim 1, further comprising an inner conductor layer in which an opening similar to the opening is formed. A plurality of antenna structures according to claim 1 or 2 ,
An array antenna comprising the antenna structures arranged in an array.

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