JP2008035424A - Array antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To materialize a compact array antenna which facilitates a scan control or shape control of electromagnetic wave beams in a high frequency bandwidth of 1 GHz or more also, and is easy to obtain a high gain. <P>SOLUTION: A via VA formed by plugging a metal in a cylindrical hole is formed to cause a grounding plate 16 formed on the back of a dielectric substrate 15 and an end of a stab 12 to be short-circuited with respect to at least a high frequency. Trunk connection parts 16a are formed in an island shape on the back side of the dielectric substrate 15 by forming a slit S in a ring shape coaxial with this via VA in the grounding plate 16. The respective trunk connection parts 16a are all connected to the grounding plate 16 through one capacitance C. This capacitance C causes a stripe line 14 and the grounding plate 16 to be short-circuited with respect to a high frequency, and simultaneously to be insulated with respect to a direct current. Further, one capacitance C is connected to a direct current power supply so as to provide a potential difference (i.e., in parallel) at both ends thereof. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an array antenna (leakage wave antenna) having a strip line formed by periodically and repeatedly arranging a predetermined unit pattern made of a conductor on the front side of a dielectric substrate having a ground plate on the back surface. In particular, the present invention relates to an antenna having controllable directivity.
The present invention is useful for radars and communication devices that transmit or receive electromagnetic waves in the millimeter wave band or microwave band, and is very useful for reducing the size of antennas or the space required for installation.

  A configuration example of a conventional strip array antenna (leakage wave antenna) having a CRLH (Composite Right and Left Handed) transmission line on a dielectric substrate is illustrated in FIG. The CRLH line is provided with a gap that periodically divides the transmission line (main line in the X-axis direction), a stub branched from the transmission line, and the like. In this antenna, the direction of the group velocity and the phase velocity of transmitted electromagnetic waves can be opposite to each other in a certain frequency band by the action of the capacitance provided by the gap and the inductance provided by the stub. As a result, the frequency of the transmitted electromagnetic wave can be changed, so that the direction of the electromagnetic wave propagates on the main line is inclined from the positive z-axis direction to the negative x-axis direction in the figure. Electromagnetic waves can be emitted even in the angle region where θ <0. As a result, when the direction of the radiation beam is changed, the scanning range of the radiation beam can be widened. Such a principle that the phase velocity and the group velocity are opposite to each other is disclosed in detail in, for example, Non-Patent Document 1 below.

  Non-Patent Document 2 below discloses a control method for variably controlling the radiation angle of a radiation beam based on predetermined electronic control while fixing the frequency of an electromagnetic wave input from a feeding point to a constant value. . In this radiation angle control method, for example, a varactor diode is arranged close to each gap or stub of a wiring pattern as shown in FIG. 16 and the capacitance of each varactor diode is variably controlled to radiate the radiation beam. The radiation angle is variably controlled. The directivity can be controlled by controlling the voltage applied to each strip line. That is, the directivity (that is, the directivity related to the angle θ in FIG. 16) along the transmission direction around the direction perpendicular to the surface of the dielectric substrate, such as near the feeding point or near the termination point, is It changes based on the power supply voltage to each unit pattern.

  Further, in Patent Document 1 below, a beam scanning antenna (FIG. 17-A) using a reflector having an EBG structure (Electrical Band Gap structure) in which a metal patch having a via in the center is periodically arranged on a dielectric substrate. , -B) has been proposed. This beam scanning antenna variably controls the traveling direction of the reflected wave of electromagnetic waves incident on the reflector from a predetermined direction, that is, the directivity of reflection, by changing the capacitance between the metal patches of the reflector. Therefore, the capacitance between the metal patches is variably controlled by moving the movable plate to which the metal patches are attached in the horizontal direction.

In general, in the field of electromagnetic wave sensing or wireless communication, it is desirable that the directivity of the radiation beam of the antenna can be controlled without changing the frequency of the radiated electromagnetic wave.
Tatsuo Ito and two others, 'CHARACTERISTICS AND APPLICATIONS OF PLANAR NEGATIVE REFRACTIVE INDEX MEDIA', MWE2003, WS02-03 Tatsuo Ito and two others, 'Electronically-Controlled Metamaterial-Based Transmission Line as a Continuous-Scanning Leaky-Wave Antenna', 2004 IEEE MTT-S Digest TU1D-4. US Patent: US 6,552,696 B1

  However, in the conventional array antenna described in Non-Patent Document 1, the directivity of the beam over a wide range including the angle region where θ <0 as described above is used unless the frequency of the feed power is greatly changed. Therefore, it is difficult to arbitrarily control the radiation angle of the radiation beam of the electromagnetic wave having a constant frequency with this conventional antenna. For this reason, the antenna which employ | adopted this system is disadvantageous or unsuitable at least for uses, such as communication and sensing.

In the conventional array antenna described in Non-Patent Document 2, a varactor diode is used as a variable capacitor. However, since a varactor diode generally has a large transmission loss, a varactor is used in a frequency band of several GHz or more. It is difficult to operate the diode as a desired variable capacitor. For this reason, this prior art cannot be used for an array antenna that handles electromagnetic waves in a frequency band of several GHz or more.
Further, even in a frequency band of 1 GHz or less in which the radiation angle can be variably controlled, it is not always easy to ensure a sufficiently large capacity displacement ratio (change rate) with respect to a standard capacity (predetermined reference capacity) in a varactor diode. Therefore, it is not always easy to ensure a large variation range of the radiation angle.

Further, the conventional beam scanning antenna (FIGS. 17A and 17B) described in Non-Patent Document 3 has the following problems relating to productivity and controllability, and downsizing and thinning. .
(1) As shown in FIGS. 17A and 17B, since a beam scanning antenna is configured using a reflector having an EBG structure, another power feeding antenna for irradiating electromagnetic waves to the reflector is separately provided. It is necessary to prepare. Further, since the above-described reflector is interposed in the radiation of the electromagnetic wave beam, it is difficult to obtain a desired radiation beam with high gain unless high reflection efficiency is realized.
(2) Although the directivity of the radiation beam of the antenna can be variably controlled by moving the movable plate in the horizontal direction, each metal patch has a strong restriction on the periodic positional relationship. The position cannot be controlled independently. For this reason, a beam shaping technique such as variably controlling the beam width and beam pattern cannot be introduced to this conventional beam scanning antenna.

  In addition, the dielectric constant or permeability of the dielectric substrate constituting the target antenna is variably controlled by an actively controlled electric field or magnetic field, whereby the radiation angle of the array antenna radiation beam can be varied to a desired angle. Although a control method can be considered, when a material such as ferrite whose dielectric constant changes is used for the antenna substrate, the power loss of the electromagnetic wave propagating in the antenna becomes very large, so the antenna gain It is difficult to secure a large value.

  The present invention has been made to solve the above-described problems, and its purpose is to easily perform scanning control or shape control of an electromagnetic wave beam and to obtain a high gain even in a high frequency band of 1 GHz or higher. This is to realize a small array antenna.

In order to solve the above problems, the following means are effective.
That is, the first means of the present invention includes a strip line formed by arranging a plurality of identical or similar unit patterns made of planar conductors in a predetermined direction on the front side of a dielectric substrate, and the dielectric substrate. In an array antenna having a ground plate made of a conductor formed on the back surface of the substrate, a dielectric constant variable member whose dielectric constant changes according to an applied electric field, and an electric field setting means for applying an electric field to the dielectric constant variable member The unit pattern includes a transmission line, a gap that divides the transmission line in the middle, and a stub that branches from the transmission line, and the dielectric constant variable member approaches the gap or stub. The relay connection portion formed on the back surface of the dielectric substrate in an island shape independent of the ground plate and the stub are electrically connected to the dielectric substrate. A via provided by the electric field setting means, by variably controlling the DC potential applied to the relay connection unit, and to variably control the electric field.

However, any of the array antennas of the present invention may be a single line antenna or a planar antenna composed of a plurality of strip lines. In other words, the unit patterns described above may be arranged in one column, or may be arranged in a plurality of columns.
In addition, the variable control of the electric field may be one in which the electric field intensity can be continuously changed or may be changed in stages, and is based on simple on / off control of the DC potential. Also good. Therefore, for example, the dielectric constant in each direction of the dielectric constant variable member can be variably controlled monotonically and continuously by adjusting the electric field strength applied by the electric field setting means.
Note that a metal conductor is embedded in the via.

According to a second means of the present invention, in the first means, the variable dielectric constant member is made of liquid crystal or a ferroelectric.
According to a third means of the present invention, in the first or second means, the electric field setting means is individually provided for each unit pattern, and the variable control of the direct current potential is performed in these units. This is performed independently for each pattern.
According to a fourth means of the present invention, in any one of the first to third means, the relay connection portion and the ground plate are short-circuited to a high frequency via a capacitor.

According to a fifth aspect of the present invention, there is provided a strip line formed by arranging a plurality of identical or similar unit patterns made of planar conductors in a predetermined direction on the front side of the dielectric substrate, and the dielectric substrate. In an array antenna having a ground plate made of a conductor formed on the back surface of the metal plate, it is composed of at least one of a dielectric, a magnetic material, a metal conductor, or a composite thereof, and the height h from the strip line varies A movable member that can be moved and an actuator that mechanically acts on the movable member to change the height h of the movable member are provided, and the transmission line and the transmission line are divided in the unit pattern. A gap and a stub branching from the transmission line are provided, and the movable member is brought close to the strip line or the unit pattern so that the strip line or Position disposed to cover the pattern, to the dielectric substrate, is to provide a via shorting said stub and the ground plate with respect to high frequency.
However, a metal conductor is embedded in the via. The height h is a distance measured perpendicularly from the surface of the dielectric substrate on which the unit patterns are arranged.

According to a sixth means of the present invention, in the fifth means, an actuator and a movable member are individually provided for each unit pattern, and the variable control for the height h is performed for each unit pattern. It is to execute each independently.
According to a seventh means of the present invention, in any one of the fifth and sixth means, the via and the ground plate are connected to a high frequency via a capacitor on the back side of the dielectric substrate. Short circuit.
By the above means of the present invention, the above-mentioned problem can be effectively or rationally solved.

As a configuration form of the stub of the CRLH leakage wave antenna, a method of virtually replacing the ground connection by providing a wide end region having a certain area (that is, a pseudo grounding capacity) at the tip of the stub; There can be considered two types of methods in which vias filled with metal conductors are provided in a dielectric substrate, and the terminal portion of the stub on the front side is short-circuited to the ground (ground plate) on the back side of the substrate at least in high frequency via the vias. .
According to the latter method using vias, it is not necessary to provide the above-described end region. Therefore, in the unit pattern, the radiation area on the front side of the dielectric substrate is reduced as compared with the case where the former method is adopted. As a result, the current flowing through the stub decreases. Therefore, according to the latter method, when many unit patterns made of conductors are arranged on the surface of the dielectric substrate, wasteful radiation from the unit patterns arranged in the vicinity of the power feeding portion can be effectively suppressed and at the same time. The feeding power can be efficiently distributed to the unit pattern far from the feeding point. For this reason, the radiation amount is made uniform between the unit patterns, or at least the bias of the radiation amount is effectively reduced between the unit patterns. As a result, the gain of the antenna is improved and the shape of the radiation beam is narrower than that of the former method.
Therefore, according to the array antenna of the present invention employing the latter method using vias, high gain and excellent directivity can be obtained simultaneously.

Hereinafter, each operation and effect by each means of the above-mentioned present invention is explained.
For example, according to the first means of the present invention, since the electric field in the space region where the dielectric constant variable member is placed can be variably controlled using the electric field setting means, those dielectric constant variable members It is possible to variably control the direction of the moment vector of the electric dipole at the molecular level constituting the desired direction. Therefore, based on this variable action, the dielectric constant in each direction of the dielectric constant variable member can be controlled. Furthermore, due to the change in the dielectric constant of the variable dielectric constant member, the capacitance of each of the above-mentioned gabs constituting the strip line, the inductance of each of the stubs, or the capacitance between each unit pattern and the ground plate Or admittance changes.

Therefore, according to the first means of the present invention, the directivity of the antenna can be arbitrarily controlled over a wide area based on these variable actions (directivity variable control function). Further, since the above variable operation is based on a molecular level operation of liquid crystal or the like, it is advantageous for speeding up the scanning operation and reducing the size of the apparatus.
The relay connection portion arranged on the back side of the via is grounded at a high frequency with respect to the DC power source provided in the electric field setting means. The capacity may be supplemented as in the fourth means of the invention, or may not be supplemented. By using such a via, it is not necessary to provide the aforementioned wide end region at the front end of the stub on the front side, so that excellent directivity and high gain can be obtained as described above.

According to the first means of the present invention, since the relay connection portion is connected to the DC power source of the electric field setting means, the stub constituting a part of the unit pattern located on the front side is a high frequency Is grounded through the via. In addition, since the relay connection portion is disposed on the back surface side of the dielectric substrate, the bias line connecting the relay connection portion and the DC power source can be hidden on the back surface side of the dielectric substrate.
Therefore, according to the first means of the present invention, leakage of the high frequency radiated from the bias line to the front side can be effectively suppressed, so that the adverse effect of the bias line on the radiation characteristics of the array antenna is effectively reduced. Can be eliminated. For this reason, the design of the antenna becomes easy, and the radiation characteristics of the antenna become better than before.

In addition, the relay connection portion and the ground plate on the back side of the substrate are not short-circuited in a direct current, and an arbitrary direct-current potential difference can be given between them by the electric field setting means. Variable control function is guaranteed.
Incidentally, if the above-mentioned bias line is sufficiently narrowed to, for example, about 10 μm, high frequency is not transmitted based on its reactance, so it may be provided on the front side. However, in light of the current technical level of etching processing, the width of the wiring that can be formed on the substrate is limited to about 80 to 100 μm. For this reason, it is not easy to achieve the above-mentioned desired processing accuracy. Therefore, a method of sufficiently narrowing the wiring width and disposing the bias line on the front side of the substrate is at least very realistic for now. It's not a good approach.
On the other hand, according to the first means of the present invention, since the bias line is hidden on the back side of the dielectric substrate, the wire bonding or the like, which tends to be slightly thicker, can be used on the back side of the dielectric substrate. Can be introduced more freely than before, and the processing of the wiring is easy.

  In addition, according to the second means of the present invention, the variable range of the dielectric constant indicated by the dielectric constant variable member can be ensured wider, so that the range of the scanning angle of the radiation beam can be ensured larger. it can. Further, according to the second means of the present invention, even when the shape of the radiation beam is controlled to a desired shape, the controllability (degree of freedom) thereof can be secured higher.

  Further, when the movable member of the fifth means of the present invention is mechanically moved perpendicularly to the substrate, this changes the equivalent dielectric constant in the vicinity of the gap or stub, or provides the capacitor or stub provided by the gap. The electrical length of the inductor can be changed. That is, since the gap capacitance and the stub inductance can be changed by variably controlling the height h, the intensity and phase distribution of electromagnetic waves radiated from the array antenna can be variably controlled. it can. Therefore, according to the fifth means of the present invention, the directivity of the array antenna can be variably controlled by variably controlling the height h using the actuator.

In addition, since the fluctuation range of the height h at this time can be kept to a sufficiently small length of less than 1 mm, according to the fifth means of the present invention, even in a high frequency band of 1 GHz or higher, a predetermined range is obtained. It is possible to realize an array antenna with a much smaller beam than the conventional one having a wide beam-oriented scanning range with respect to the frequency. This is because the directivity of the radiation beam can be variably controlled based on the minute displacement of each movable member, so compared to the conventional method in which the directivity is variably controlled by mechanically changing the orientation of the entire array antenna. This is because a desired array antenna can be formed more compactly.
In the fifth means of the present invention, it is not necessary to provide the aforementioned wide end region at the front end of the stub on the front side by using the above-described via, and as a result, excellent directivity and high gain can be obtained. As described above.

  Further, according to the third or sixth means of the present invention, the above-described capacitance and inductance can be controlled for each unit pattern, so that the beam width and beam shape of the antenna can be variably controlled. it can.

  For example, since the effective length of the antenna can be variably controlled by controlling the capacitance and inductance for each unit pattern, the beam width of the antenna can be variably controlled. This effective length is the length of the portion of the array of unit patterns constituting the antenna that actually acts effectively as an antenna. This length is the amount of radiation of each unit pattern. Can be determined based on More specifically, the effective length of these antennas can be variably controlled by providing an arrangement of unit patterns that are difficult to operate for a predetermined frequency band on the terminal end side of the antenna and forming a band gap there. The effective length of the antenna can be set shorter as the arrangement length of the unit patterns (unit pattern length × number of unit patterns), which is difficult to operate in a predetermined frequency band, is longer.

Further, if the directivity is controlled for each unit pattern by variably controlling the phase for each unit pattern, a null can be formed in the beam shape of the array antenna. Further, if an appropriate radiation pattern such as a tailor distribution is employed, a beam shape with a small side lobe can be realized by controlling the capacitance and inductance for each unit pattern.
In addition, by combining these variable controls arbitrarily, various desired functions such as the radiation beam directivity variable function and the radiation beam shape variable function described above can be combined and realized simultaneously. Can do.

  In addition, according to the fourth or seventh means of the present invention, when designing the capacity between each unit pattern and the ground plate, the capacity of each of the gaps, etc., the degree of design freedom regarding these capacities is increased. growing. Therefore, according to the fourth or seventh means of the present invention, tuning of the radiation beam directivity, beam shape, scanning range, etc. of a desired antenna becomes easy. In addition, the introduction of such a degree of freedom can effectively contribute to downsizing of the apparatus.

The unit patterns are desirably arranged in the same pattern periodically, at least from the viewpoint of ease of design and manufacturing, but it is not always necessary to periodically arrange the unit patterns. In addition, the unit pattern as a constituent element of the strip line does not necessarily have to have the same dimensions such as the thickness and length of each part such as the transmission line and the stub, and the gaps and the like may not be uniform.
The stub may be provided only on one side of the strip line, on both sides at the same position, or the side provided along the traveling direction may be alternately reversed. In general, the stub is provided at a right angle to the strip line, but the angle may be generally arbitrary. Further, the opposite part of the strip line constituting the gap may be configured to have a wide width in the direction perpendicular to the transmission direction in order to increase the capacitance.

  In addition, the frequency of the electromagnetic wave radiated or received by the array antenna of each example illustrated below is assumed to be a substantially fixed frequency in the range of 10 GHz to 300 GHz (millimeter wave band and quasi-millimeter wave band). Of course, the pattern formation period when the unit pattern is repeatedly formed in the x-axis direction may be determined according to the frequency as in the conventional case. However, the operations and effects that can be obtained by the present invention are not necessarily limited to the array antenna that handles electromagnetic waves in the above frequency band.

  In particular, when the dielectric constant variable member is composed of liquid crystal, a plate (for example, an orientation) in which grooves are carved in that direction in order to align the liquid crystal molecules in a desired direction when the electric field is not applied. It is desirable to use a film. That is, for example, techniques in the field of liquid crystal display can be applied or applied to such alignment control of liquid crystal molecules.

  In particular, when the above-described fifth means of the present invention is employed, the following embodiments are also effective. That is, for example, the actuator can be configured using, for example, a piezoelectric element (piezo element) or the like, and in this case, the height h can be electrically controlled. However, the height h may be variably controlled using a mechanical drive control mechanism.

In addition, when the movable member is composed of a composite of a dielectric and a metal conductor, or a composite of a magnetic and a metal conductor, a metal conductor may be provided on the surface of the dielectric or magnetic body. Alternatively, a metal conductor may be provided inside the dielectric or magnetic material.
However, if a metal conductor that is connected over a wide area so as to cover the entire strip line or the entire unit pattern is disposed, the radiation of electromagnetic waves from the array antenna is blocked. It is not used for the structure of the movable member. When these metal conductors are used, the metal conductors are locally distributed as at least a part of the movable member, for example, locally included in a dielectric substrate.

  The movable member does not necessarily have to be disposed so as to cover the entire unit pattern. For example, only the gap may be covered from above by the movable member, only the stub may be covered from above, or both of them may be covered from above. The portion of the movable member disposed in the vicinity of the gap predominantly changes the gap capacitance, and the portion disposed in the vicinity of the stub predominantly changes the inductance of the stub.

  In addition, as a material of said movable member, a fluororesin, ceramics, etc. are suitable, for example. If these materials are used, the relative permittivity of the movable member can be controlled to 2 to 10, so that it can be used in a high frequency band of 1 GHz or more and is a small array antenna having a wide beam-oriented scanning range. Can be realized at low cost.

Hereinafter, the present invention will be described based on specific examples.
However, the embodiments of the present invention are not limited to the following examples.

FIG. 1 shows a plan view of the array antenna 100 of the first embodiment. A rectangular pool region 15a is formed at the center of the dielectric substrate 15 made of tetrafluoroethylene resin having a relative dielectric constant of 2.2. In this pool region 15a, photomultiplication is performed on a nematic liquid crystal. Liquid crystal 13 (dielectric constant variable member) made by mixing a polymer is filled. In addition, alignment grooves extending in the x-axis direction are formed on each surface surrounding the liquid crystal 13. Most portions of the strip line 14 developed from the feeding point p ₁ to the terminal point p ₂ are patterned on the liquid crystal 13. The strip line 14 can be formed from a conductor such as copper, and most of the strip line 14 is formed by periodically repeating the unit pattern U. The unit pattern U includes a main line 11 extending in the x-axis direction, a stub 12 extending in the y-axis direction using the main line 11 as a trunk, and a gap G1 that divides the main line 11 in the middle.

  The array antenna 100 is configured by arranging the above unit patterns U in the x-axis direction for 16 periods. The gap G1 formed from the facing surface of the divided main line 11 constitutes a capacitor, and the facing portions 11a and 11b are expanded in the y-axis direction in order to increase the capacitance of the gap G1. Is formed. A via VA is formed at the end of the stub 12 protruding in the y-axis direction.

2A, -B, and -C show a plan view of the unit pattern U of the array antenna 100, and cross-sectional views of the cross section α and cross section β, respectively. A ground plate 16 made of a flat conductor is formed on the back surface of the dielectric substrate 15. The via VA is for short-circuiting the ground plate formed on the back surface of the dielectric substrate 15 and the end portion of the stub 12 at least with respect to high frequency, and is a cylinder dug in the dielectric substrate 15 in the z-axis direction. It is formed by filling a metal in a shape hole. The back side of the via VA is connected to the relay connection portion 16a. The relay connection portion 16 a is formed in an island shape on the back surface side of the dielectric substrate 15 by forming a ring-shaped slit S coaxial with the via VA in the ground plate 16. Each relay connection portion 16a is connected to the ground plate 16 through one capacitor C. The capacitor C causes the strip line 14 and the ground plate 16 to be short-circuited with respect to high frequencies and at the same time to be insulated from direct current. Further, a DC power source is connected to one capacitor C so as to provide a potential difference at both ends (that is, in parallel). That is, one wiring q ₁ of this DC power supply is connected to the relay connection portion 16 a and the other wiring q ₂ is connected to the ground plate 16. Such a DC power supply may be provided for each unit pattern U, or one DC power supply may be shared among the unit patterns U by, for example, parallel connection.

Using such electric field setting means (the above-described DC power supply, wirings q ₁ , q _2, etc.), an electric field is applied in the z-axis direction to the liquid crystal 13 (dielectric constant variable member) disposed under the strip line 14. When applied, the liquid crystal molecules constituting the liquid crystal 13 rotate and change direction, and at this time, the dielectric constant in the z-axis direction increases.
For example, when the thickness of the liquid crystal 13 in the z-axis direction is set to about 0.127 mm, when a voltage of 100 V is applied between the strip line 14 and the ground plate 16 by the electric field setting means, the z of the liquid crystal 13 is set. The axial dielectric constant varies from about 2.2 to about 2.8. When this voltage is 50 V, the relative dielectric constant of the liquid crystal 13 in the z-axis direction is about 2.4.

  FIG. 3A is a wiring diagram in the radiation simulation of the array antenna 100. Here, the DC power source is a variable voltage power source, and each unit pattern U is connected in parallel to the power source so as to be shared among the unit patterns U.

On the other hand, FIG. 3-B shows a configuration of a comparative example for the radiation simulation. In this array antenna 900 by using the wire q ₃ from the wide end 12a of the direct stub 12 without providing the vias, and the method of providing a DC potential to the strip line of the unit pattern. Here, the reason why the end portion 12a is formed to be wide is to embody a grounding point in a pseudo manner by this portion, thereby forming a virtual grounding capacitance.
In the array antenna 100 of the present embodiment, since the area of the strip line 14 on the front side is smaller than that of the array antenna 900, the capacity between the strip line 14 and the ground plate 16 is also small. It can be compensated or adjusted by the capacity C (FIG. 2-C). Similarly, the capacitance (the ground capacitance) produced by the wide end portion 12a can be supplemented or adjusted by the capacitance C (FIG. 2-C).

  Therefore, if such adjustment is appropriately performed, the array antenna 100 can be configured as a circuit that is substantially equivalent to the array antenna 900 (comparison column) in terms other than its radiation area. In other words, the grounding method of the stub of the array antenna 100 of the first embodiment is excellent in that these adjustment parameters can be easily provided using a lumped constant element. According to the grounding system via the antenna, tuning of the radiation beam directivity, beam shape, scanning range, etc. of a desired antenna becomes easy. The introduction of such a degree of freedom also contributes to the miniaturization of the target array antenna.

4A to 4C show the results (radiation characteristics) of the radiation simulation of the first embodiment. From the simulation results, the following can be understood. However, in this radiation simulation, it was assumed that the frequency of the high frequency to be fed was 76 GHz, and the capacitance C was 5 pF.
(1) In the array antenna 100 according to the first embodiment having vias, the azimuth angle θ of the radiation peak of the radiation beam can be swung from + 28 ° to −24 ° by changing the voltage of the DC power source from 0V to 100V. it can.
(2) The gain of the array antenna 100 (with vias) is about 1 dBi higher than that of the array antenna 900.
(3) The beam width of array antenna 100 (with vias) is narrower than that of array antenna 900. (This radiation characteristic is very advantageous when narrowing down the target to be observed.)

These simulation results show that in the array antenna 100, useless radiation from the unit pattern U arranged in the vicinity of the feeding point is suppressed, and the corresponding feeding power efficiently reaches the unit pattern near the termination point. For this reason, it is considered that this is caused as a result of the uniform radiation between the unit patterns.
In the array antenna 900, the bias line (wiring q ₃ ) must be exposed to the front side of the dielectric substrate, but in the array antenna 100, these wirings (wirings q ₁ and q ₂₎ are introduced by introducing the via VA. ) Can be concealed on the back side, so that the radiation from these bias lines can also adversely affect the radiation characteristics of the desired array antenna.

5A and 5B show wiring diagrams in the radiation simulation of the second embodiment. In the present embodiment, the array antenna 110 is newly formed by providing the switch SW on the wiring q ₁ for each unit pattern with respect to the array antenna 100 of the first embodiment. Based on the off state, the width of the radiation beam of the antenna can be variably controlled.

The voltage of the DC power source in FIGS. 5-A and -B is 100V, but in the connection state a shown in FIG. 5-A, all 16 switches SW are in the off state. The relative permittivity in the z-axis direction of the variable rate member (liquid crystal 13) remains 2.2. On the other hand, in the connection state b shown in FIG. 5B, the switches SW corresponding to the eight unit patterns U near the feeding point are in the off state, and the eight units near the terminal point P _{2 in the} other half. For the pattern U, the corresponding switches SW are in the on state. For this reason, the relative dielectric constant in the z-axis direction of each dielectric constant variable member (liquid crystal 13) of the eight unit patterns U near the termination point P ₂ is changed to 2.8.

At this time, in the connection state b (FIG. 5-B), the effective antenna length is substantially half that of the connection state a (FIG. 5-A). This is because, when each dipole moment composed of individual molecules of the liquid crystal 13 is aligned in the z-axis direction according to the electric field, it becomes difficult for the high frequency to propagate through the gap G1 portion (capacitance) in FIG. is because the high frequency is easily grounded to the ground plate 16, on the basis of this action, eight each unit patterns U of the connection state b in end point P ₂ closer hardly operate as an antenna element (radiating elements) . Hereinafter, the non-operating portion of the array antenna formed by the group sequence of such non-operating unit patterns U is referred to as a band gap.

FIG. 6 shows the result of this radiation simulation (radiation characteristics). As can be seen from this graph, in the vicinity of the gain of 3 dBi to 4 dBi, the width of the radiation beam in the connection state a of the array antenna 110 is approximately half that in the connection state b. Further, the gain at the radiation peak is 10.1 dBi in the connection state a and 7.6 dBi in the connection state b. From these results, when it is desired to detect a wide range of objects at short distances, the control should be performed as shown in FIG. 5-B. When a remote object is detected at a narrow angle, the control as shown in FIG. It can be seen that the form is suitable.
Further, the width of the radiation beam of the antenna is set to a non-operational state (that is, the dipole moment of the liquid crystal is aligned in the z-axis direction, as illustrated later with reference to FIG. ) It can be controlled by the number of unit patterns U.

Furthermore, in the connection form b of FIG. 5-B, the same simulation was performed by changing the voltage of the DC power source from 100V to 50V. The result is shown in graph b of FIG. However, the graph a in FIG. 7 is a copy of the graph with vias in FIG. 4-A as it is for comparison and reference. When the voltage of each power source is controlled in such a relatively narrow range (0 V to 50 V), no band gap is formed, and the amount of radiation from each unit pattern U and the direction of radiation can be controlled arbitrarily. it can.
Although there is almost no difference in the peak gain between the graph a and the graph b in FIG. 7, a null is formed around + 2 ° in the graph b. This is because the radiation beams from the eight unit patterns U on the feeding side are directed toward the backward side, and the radiation beams from the eight unit patterns U on the termination side are directed toward the forward side. Null is facing in the direction of. Further, the direction in which the null faces can be controlled by changing the voltage of the DC power supply.
Therefore, for example, when the direction of the noise source is known, the S / N ratio of the array antenna can be effectively improved by aligning the null direction with that direction.

  The array antenna 120 of the third embodiment shown in FIG. 8 is the same as the array antenna 100 of the first embodiment except that the DC power supply of FIG. 2-C is provided for each unit pattern U, and the voltage of each of these DC power supplies. Can be variably controlled individually. Since the beam width adjusting function and the null forming function in the second embodiment are realized by variably controlling the magnitude of the electric field applied to each unit pattern U, of course, the array antenna of the third embodiment. The same function can be realized by 120.

  Similarly, in this structure, in particular, when the voltage of each power source is controlled within a relatively narrow range (eg, 0 V to 50 V), no band gap (the above non-operating portion) is formed, and each unit pattern The amount of radiation from U and the direction of radiation can be arbitrarily controlled. For this reason, if the array antenna 120 of the third embodiment is used, for example, the following functions can be realized in addition to the above-described null forming function.

(Side lobe suppression function)
This sidelobe suppression function suppresses the radiation level of the sidelobe appearing on the xz plane, and this function is realized by making the distribution of radiation from each unit pattern U into a generally known Taylor distribution. can do.

  FIG. 9 shows a perspective view and a cross-sectional view of the array antenna 200 of the fourth embodiment. The dielectric substrate 1 is made of a plate-like material having a thickness of about 0.13 mm formed from a tetrafluoroethylene resin (: relative dielectric constant 2.2), and this corresponds to a movable member whose height can be varied. . The dielectric substrate 1 is connected to a main body 10 of the antenna via a piezo element 2. The piezo element 2 can be expanded and contracted in the normal direction of the dielectric substrate 1, that is, the z-axis direction in the drawing by applying a voltage to the surface thereof. That is, the piezo element 2 corresponds to an actuator that changes the height h of the dielectric substrate 1.

  As shown in the cross-sectional view of FIG. 9, the main body 10 is formed based on a dielectric substrate 15, and a strip line 14 is formed on the upper surface of the dielectric substrate 15. A ground plate 16 formed of a metal layer is laminated on the back surface of the dielectric substrate 15. Further, the ground plate 16 and the strip line 14 are short-circuited by a via VA. This via VA is formed by filling a metal in a cylindrical hole dug in the dielectric substrate 15 in the z-axis direction.

  FIG. 10 shows a plan view of the main body 10. The strip line 14 is formed by a periodic arrangement of the unit patterns U of the first embodiment in the x-axis direction, and the via VA is provided at the tip of the stub 12 constituting a part of the strip line 14. It has been. That is, these wiring patterns are formed in the same manner as the wiring pattern of FIG. However, the dielectric substrate 15 of the main body 10 does not have a region filled with liquid crystal, and the array antenna 200 of the fourth embodiment uses no liquid crystal.

  The height h in FIG. 9 indicates the distance from the top surface of the dielectric substrate 15 that forms the base of the main body 10 to the back surface of the dielectric substrate 1, and is measured in the z-axis direction. The height h can be freely variably controlled by the expansion / contraction operation of the piezo element 2 (actuator) whose applied voltage can be variably controlled as described above.

FIG. 11 shows the result of the radiation simulation of the array antenna 200, that is, the dependence characteristic related to the directivity height h. The directivity is measured by changing the height h in the following three ways. However, the frequency of the feeding power at this time was 76 GHz. The peak position (angle θ) of the radiation pattern at this time is θ = −14 ° when h = 1.0 mm, θ = + 2 ° when h = 0.6 mm, and when h = 0.2 mm. θ = + 20 °.
For example, in this way, in the array antenna 200 of this embodiment, the direction of the radiation beam can be variably controlled by variably controlling the height h with the actuator.

  FIG. 12 shows a comparative example for the array antenna 200 of the fourth embodiment. The stripline 14 in FIG. 12 is formed in the same manner as that in FIG. 3B, and in this comparative example, a simulation substantially equivalent to the above was performed using the main body 10 ′ in FIG. However, the main body 10 'of FIG. 12 is not provided with a liquid crystal and, of course, is not connected to a DC power supply or its bias line.

  FIG. 13 shows the result of the radiation simulation according to this comparative example. This directivity is measured by changing the height h in three ways: h = 0.1 mm, 0.05 mm, and 0.025 mm. The frequency of the feed power was 76.5 GHz. The peak position (angle θ) of the radiation pattern at this time is θ≈0 ° (in the z-axis direction) when h = 0.05 mm, θ≈ + 25 ° when h = 0.1 mm, and h = 0. At 025 mm, θ≈−28 °.

As can be seen by comparing the graphs of FIG. 11 and FIG. 13, rather than the method of providing the end 12 a on the stub 12 and realizing the virtual ground state, the vias VA are actually used to directly contact the ground plate 16 on the back surface. The method of grounding the tip of the stub 12 can make the width of the radiation beam narrower. This is due to the same action as that shown in the first embodiment. That is, in the array antenna 200, unnecessary radiation from the unit pattern U arranged near the feeding point is suppressed, and the corresponding feeding power efficiently reaches the unit pattern near the termination point. It is considered that the radiation is made uniform between unit patterns.
In addition, the radiation characteristics with such a narrow beam width are very advantageous when narrowing down the target to be observed.

  FIG. 14 is a perspective view of the array antenna 210 according to the fifth embodiment. The array antenna 210 is an improvement of the array antenna 200 of the above-described fourth embodiment. The main body 10 is the same material and the same structure as that used for the array antenna 200 of the fourth embodiment. However, although the configuration of each unit pattern U is the same, the number of repetitions of the unit pattern U in the x-axis direction is 11 units.

  The array antenna 210 is characterized in that the dielectric substrate 1 of the array antenna 200 is divided and arranged in correspondence with each unit pattern U. In other words, in this array antenna 210, the dielectric substrate 1 of the array antenna 200 is divided into a total of 11 pieces of 1a to 1k and arranged in the x-axis direction. Further, along with this division, the piezo elements 2 (actuators) of the array antenna 200 are also arranged individually corresponding to the respective dielectric substrates 1a to 1k. That is, for example, the piezo element 2k is an actuator for translating the dielectric substrate 1k in the z-axis direction. The same applies to the piezo elements 2a to 2j.

(Operation and effect of Example 5)
The height h of each dielectric substrate 1a-1k can be variably controlled by variably controlling the voltage applied to each piezoelectric element 2a-2k. Then, by executing the variable control of the height h independently for each unit pattern, the following actions and effects can be obtained.

(1) Change the beam width of the antenna freely For example, the capacitance component of the gap and the inductance component of the stub can be variably controlled by using the actuator described above. The frequency can be controlled to be inactive. In this case, a band gap can be formed on the end side of the array antenna, that is, on the side opposite to the feeding point, by the unit pattern in the non-operating state. The length can be variably controlled. At that time, the shorter the effective length of the array antenna, the wider the beam width of the array antenna, so that the beam width of the antenna can be variably controlled. However, the above-mentioned effective length is the length of the portion of the array of unit patterns constituting the antenna that actually acts effectively as an antenna. This length is the length of each unit pattern. It can be determined based on each radiation amount.

  FIG. 15 illustrates the result (azimuth-gain characteristic) of the radiation simulation of the array antenna 210. For example, when the frequency of the feeding power is 76.0 GHz, the height h of the dielectric substrates 1a to 1c is 0.1 mm, and the height h of the dielectric substrates 1d to 1k is 0.025 mm, respectively, FIG. A beam shape as shown in (c) is obtained. When the height h of the dielectric substrates 1a to 1g is set to 0.1 mm and the height h of the dielectric substrates 1h to 1k is set to 0.025 mm at the same frequency, a beam as shown in FIG. A shape is obtained. Further, when the heights h of the dielectric substrates 1a to 1k are all 0.1 mm at the same frequency, a beam shape as shown in FIG. 15A is obtained.

(2) Suppressing unwanted side lobe radiation If the variable control of the height h is executed independently for each unit pattern, the side lobe level can also be suppressed. That is, by using the actuator, it is possible to control the distribution of each radiation amount of the unit pattern to an appropriate distribution that exerts a sidelobe suppression action such as the well-known Taylor distribution. The amount of radiation of the side lobe of the array antenna can be reduced.

(3) Null is formed in a desired direction. Further, if variable control of the height h is executed independently for each unit pattern, each directivity of the unit pattern is controlled in a plurality of different directions, Nulls can be formed in directions that deviate from those directions, thereby reducing the reception of signals from any direction. For example, when nulls are to be formed in the front direction of the antenna, the beam direction of half of the unit pattern is directed toward the backward wave (ie, the direction of the left-handed beam) and the remaining half of the unit pattern The pattern beam may be directed toward the forward wave (ie, the direction of the right-handed beam). Thereby, reception of the signal from the front direction can be reduced.

  However, for example, when controlling the directivity of unit patterns in two different directions, each unit pattern belonging to a set of unit patterns to be radiated in one direction is not necessarily continuous on the unit pattern array. There is no need to arrange them together. That is, unit patterns that give different directivities may be arranged alternately, or a set of unit patterns that radiate in one direction may be combined into a continuous set on the array. The plurality of directions may be three directions or four or more directions.

[Other variations]
The embodiment of the present invention is not limited to the above-described embodiment, and other modifications as exemplified below may be made. Even with such modifications and applications, the effects of the present invention can be obtained based on the functions of the present invention.
(Modification 1)
For example, in the previous second embodiment, the simulation was performed with the voltage of the DC power supply of the array antenna 110 (FIGS. 5-A and -B) fixed to 100V. A DC power source that can be variably controlled may be used. In this case, as can be seen from the simulation results of Examples 1 and 2, the width of the radiation beam is controlled to an arbitrary width using a switch, and at the same time, the DC voltage is variably controlled to further increase the arbitrary width. It is possible to freely perform scanning control of the radiation beam over a wide angle region.

(Modification 2)
The DC power source may be an AC power source. As can be seen from the simulation results in FIGS. 4A to 4C, if the voltage of the DC power source is periodically changed, the scanning control of the radiation beam can be performed according to the cycle. Therefore, if a 10 Hz AC power source is used instead of the DC power source, for example, 10 scanning operations per second can be realized.

(Modification 3)
In the above-described fourth and fifth embodiments, the dielectric is moved up and down as the movable member. However, for example, a metal piece may be placed inside these dielectrics. In that case, it is possible not only to control the dielectric constant but also to control the electrical length of the gap and stub at the same time, so that the change of the beam angle θ with respect to the movement of the dielectric can be set more sensitively. . Therefore, if such a modification is made, it is possible or easier to secure a wider range of change in the beam direction, or to further downsize the actuator.

(Modification 4)
In the fourth and fifth embodiments, the movable member is translated in the vertical direction (z-axis direction), but the movement of the movable member may be a translational reciprocating motion or a rotating motion. The height h can be variably controlled by any form of motion.

(Modification 5)
The array antenna of the present invention may be used as a radiation source built in the slot antenna. In other words, for example, in order to adjust the gain of the antenna or reduce the sidelobe level, a slot plate for slot radiation may be provided on the upper portion of the array antenna of the present invention in parallel to the substrate. .

  The present invention is useful for wireless communication and electromagnetic wave sensing. For example, an object search for a wireless communication device, an obstacle sensor used in a vehicle accident prevention system, an auto cruise control system, or other objects around the vehicle. It can be used as a means.

Plan view of array antenna 100 of the first embodiment Plan view of unit pattern U of array antenna 100 Sectional view in section α of unit pattern U of array antenna 100 Sectional view in section β of unit pattern U of array antenna 100 Wiring diagram for radiation simulation of array antenna 100 The top view which shows the structure of the comparative example with respect to the radiation simulation Graph showing the radiation simulation results (radiation characteristics) Graph showing the radiation simulation results (radiation characteristics) Graph showing the radiation simulation results (radiation characteristics) Wiring diagram in radiation simulation of Example 2 Wiring diagram in radiation simulation of Example 2 Graph showing the radiation simulation results (radiation characteristics) Graph showing the radiation simulation results (radiation characteristics) Wiring diagram of array antenna 120 of the third embodiment The perspective view and sectional drawing of the array antenna 200 of Example 4. FIG. Plan view of main body 10 of array antenna 200 Graph showing the result of radiation simulation of array antenna 200 A plan view of a main body 10 'of a comparative example of the array antenna 200 Graph showing radiation simulation results for the comparative example The perspective view of the array antenna 210 of Example 5. FIG. Graph showing the result of radiation simulation of array antenna 210 A perspective view showing the structure and operation of a conventional strip array antenna Plan view of a conventional beam scanning antenna having a reflector having an EBG structure Side view showing the structure and operation of the beam scanning antenna

Explanation of symbols

100: Array antenna 11: Main line 12: Stub 13: Liquid crystal 14: Strip line 15: Dielectric substrate 16: Ground plate G1: Gap VA: Via U: Unit pattern

Claims (7)

A strip line formed by arranging a plurality of identical or similar unit patterns made of planar conductors in a predetermined direction on the front side of a dielectric substrate, and a ground plate made of a conductor formed on the back surface of the dielectric substrate In an array antenna having
A dielectric constant variable member whose dielectric constant changes according to a given electric field;
Electric field setting means for applying an electric field to the dielectric constant variable member,
The unit pattern is
A transmission line;
A gap for dividing the transmission line in the middle;
A stub branching from the transmission line,
The dielectric constant variable member is:
Arranged close to the gap or the stub,
The dielectric substrate is
A relay connection portion formed in an island shape independent of the ground plate on the back surface, and a via for electrically connecting the stub;
The electric field setting means includes
An array antenna, wherein the electric field is variably controlled by variably controlling a DC potential applied to the relay connection portion. The dielectric constant variable member is:
2. The array antenna according to claim 1, wherein the array antenna is made of a liquid crystal or a ferroelectric. The electric field setting means includes
Each unit pattern is provided individually,
The array antenna according to claim 1 or 2, wherein the variable control of the DC potential is performed independently for each unit pattern. The relay connection portion and the ground plate are:
4. The array antenna according to claim 1, wherein the array antenna is short-circuited via a capacitor with respect to a high frequency. A strip line formed by arranging a plurality of identical or similar unit patterns made of planar conductors in a predetermined direction on the front side of a dielectric substrate, and a ground plate made of a conductor formed on the back surface of the dielectric substrate In an array antenna having
A movable member made of at least one of a dielectric, a magnetic material, a metal conductor, or a composite thereof, and a height h from the stripline that can be varied;
An actuator that mechanically acts on the movable member to change the height h of the movable member;
The unit pattern is
A transmission line;
A gap for dividing the transmission line in the middle;
A stub branching from the transmission line,
The movable member is
Close to the strip line or the unit pattern, and disposed so as to cover the strip line or the unit pattern,
The dielectric substrate is
An array antenna comprising a via for short-circuiting the stub and the ground plate with respect to a high frequency. The actuator and the movable member are:
Provided individually for each unit pattern,
The variable control related to the height h is
The array antenna according to claim 5, wherein the array antenna is executed independently for each unit pattern. The via and the ground plate are
The array antenna according to claim 5 or 6, wherein the rear surface side is short-circuited to a high frequency via a capacitor.

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