Antenna device and antenna system

An antenna device includes: a ground plate; a first patch, provided on one surface side of the ground plate and including two first power feeding portions provided in a region surrounded by a first contour at positions spaced away from a first position with a first distance, configured to resonate with a first frequency; a second patch, provided between the ground plate and the first patch and including two second power feeding portions provided in a region surrounded by a second contour at positions spaced away from a second position with a second distance and a slit formed in the region, configured to resonate with a second frequency lower than the first frequency; and an inter-patch connection portion configured to electrically couple the first position of the first patch and the second position of the second patch.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2014-099460, filed on May 13, 2014, the entire contents of which are incorporated herein by reference.

FIELD

The embodiments discussed herein are related to an antenna device and an antenna system.

BACKGROUND

A patch antenna is used as a multi-frequency shared antenna that resonates with frequencies different from each other.

Japanese Laid-open Patent Publication No. 2003-309424 is an example of the related art.

SUMMARY

According to an aspect of the embodiment, an antenna device includes: a ground plate; a first patch, provided on one surface side of the ground plate and including two first power feeding portions provided in a region surrounded by a first contour at positions spaced away from a first position with a first distance, configured to resonate with a first frequency; a second patch, provided between the ground plate and the first patch and including two second power feeding portions provided in a region surrounded by a second contour at positions spaced away from a second position with a second distance and a slit formed in the region, configured to resonate with a second frequency lower than the first frequency; and an inter-patch connection portion configured to electrically couple the first position of the first patch and the second position of the second patch.

DESCRIPTION OF EMBODIMENTS

For example, a multi-frequency shared antenna includes a ground plate, a plurality of patch antenna elements for different frequencies which are laminated on an upper side of the ground plate with an interval therebetween, a plurality of conductive support units each supporting the center of each of the patch antenna elements to a patch antenna element on a lower side or to the ground plate, and a plurality of power feeding units each being coupled to a certain position of each of the patch antenna elements.

The multi-frequency shared antenna, which uses the plurality of patch antenna elements (patches), forms a laminated patch antenna that resonates with a plurality of frequencies. In the laminated patch antenna, the plurality of patches may be provided at positions close to each other for miniaturization. According to this, the plurality of patches may be electromagnetically coupled to each other or interfere each other in accordance with a frequency that is used, and thus antenna characteristics may deteriorate.

In the drawings, the same reference numeral or the same reference sign is given to the same or similar element.

The antenna device may be a laminated patch antenna that resonates with a plurality of frequencies. The laminated patch antenna may be referred to as a stacked patch antenna. The antenna device may be referred to as a multi-band patch antenna. For example, the antenna device may be used in a base station, an access point, a router, a reader/writer (R/W) of a wireless tag, and the like. A plurality of frequencies may be arbitrary frequencies which are determined in accordance with a communication environment in which the antenna device is used. For example, the plurality of frequencies may include frequencies of a frequency band of 5 GHz and a frequency band of 2 GHz. For example, the frequency band of 5 GHz may be determined based on standard specification IEEE802.11a of a wireless local area network (WLAN), and as an example, frequencies such as 5.15 GHz to 5.35 GHZ, and 5.47 GHz to 5.2725 GHz may be used. For example, the frequency band of 2 GHz may be determined based on a standard specification IEEE802.11b of a wireless local area network, and as an example, frequencies such as 2.4 GHz to 2.5 GHz may be used.

FIG. 1illustrates an example of an antenna device. InFIG. 1, attention is paid to a conductive layer of an antenna device100. For example, an insulating layer disposed between conductive layers may be omitted inFIG. 1. The antenna device100includes at least a ground plate G that is provided on an xy plane, a first patch1that is provided on one side of the ground plate G, a second patch2that is provided between the ground plate G and the first patch1, and an inter-patch connection portion12.

The ground plate G may be referred to as a ground conductor, a ground plane, a GND, and the like. The ground plate G may be formed from a metal plate, or may be conductive pattern that is formed on an insulating layer and is processed. The ground plate G may have appropriate arbitrary shape and size, and may have a size larger than that of the first and second patches1and2. As an example, the ground plate G has a planar shape that is point-symmetric about the origin OG. InFIG. 1, the ground plate G has a square shape. The ground plate G is formed from an appropriate arbitrary material with high conductivity.FIG. 2illustrates an example of a ground plate. InFIG. 2, a plan view of the ground plate G illustrated inFIG. 1is illustrated. Two power feeding lines11-1and11-2are electrically coupled to the first patch1on one side (in a z-axis positive direction). Two power feeding lines21-1and21-2are also electrically coupled to the second patch2on one side. The four power feeding lines11-1,11-2,21-1, and21-2respectively pass through penetration holes13-1,13-2,23-1, and23-2and penetrate through the ground plate G, and are coupled to a power feeding circuit35(FIG. 1) through coaxial cables15-1,15-2,25-1, and25-2, respectively.

The power feeding line11-1and an insulating material portion that exists around the power feeding line11-1are included on an inner side of the penetration hole13-1. The power feeding line11-2and an insulating material portion that exists around the power feeding line11-2are included on an inner side of the penetration hole13-2. The power feeding line21-1and an insulating material portion that exists around the power feeding line21-1are included on an inner side of the penetration hole23-1. The power feeding line21-2and an insulating material portion that exists around the power feeding line21-2are included on an inner side of the penetration hole23-2.

FIG. 3illustrates an example of a coaxial cable. The coaxial cable includes an inner conductor31, a tubular outer conductor32that surrounds the inner conductor31, and an insulating material portion33that is interposed between the inner conductor31and the outer conductor32. For example, the inner conductor31of the coaxial cable corresponding to the reference numeral15-1ofFIG. 1may be coupled to the power feeding line11-1, and the outer conductor32may be coupled to the ground plate G. The inner conductor31of the coaxial cable corresponding to the reference numeral15-2may be coupled to the power feeding line11-2, and the outer conductor32may be coupled to the ground plate G. The inner conductor31of the coaxial cable corresponding to the reference numeral25-1may be coupled to the power feeding line21-1, and the outer conductor32may be coupled to the ground plate G. The inner conductor31of the coaxial cable corresponding to reference numeral25-2may be coupled to the power feeding line21-2, and the outer conductor32may be coupled to the ground plate G.

InFIGS. 1, 2, and 3, the power feeding circuit35may be coupled to the first and second patches1and2through the coaxial cables, and may be coupled to the first and second patches1and2through an appropriate arbitrary power feeding method. For example, the power feeding circuit35may be coupled to the first and second patches1and2through a microstrip line, a coplanar line, and the like.

InFIGS. 1 and 2, power feeding of the two patches of the first and second patches1and2is performed by a two-point power feeding method, respectively, and thus a total of four power feeding lines are used. For example, three or more patches may be provided to the antenna device, and six or more power feeding lines and penetration holes may be provided.

As illustrated inFIG. 1, the antenna device100includes the first patch1. The first patch1is provided to be spaced away from the ground plate G with an appropriate distance on one surface side of the ground plate G (inFIG. 1, the z-axis positive direction). To increase the gain of the antenna device100, the first patch1may be provided at a distance far away from the ground plate G. However, the position and the height of the first patch1may be determined with limitation from the viewpoint of miniaturization and the like. For example, the first patch1may be provided at a height of approximately 4.5 mm from the ground plate G. The first patch1may be formed from an appropriate arbitrary conductive material with high conductivity. For example, the first patch1may be formed from copper (Cu), gold (Au), silver (Ag), stainless steel, and the like.

FIG. 4illustrates an example of a first patch. InFIG. 4, a plan view of the first patch1illustrated inFIG. 1is illustrated. The first patch1has a shape, a size, and the like to resonate with a first frequency. The first frequency may be appropriate arbitrary frequency. For example, the first frequency may be set to a frequency band of 5 GHz. The first patch1may have a first contour having a planar shape that is symmetric about the center O1. The term “symmetric about an arbitrary point” represents point symmetry, line symmetry, approximate point symmetry, or approximate line symmetry about the arbitrary point. For example, the first patch1may have a shape such as a rectangular shape, a circular shape, and a polygonal shape in a plan view. InFIGS. 1 and 4, the first patch1has a square contour. For example, the first patch1may have a square contour in which the length of one side is approximately 26 mm, and may have a thickness of approximately 50 μm. For example, inFIGS. 1, 2, and 4, the origin OGin the ground plate G, and the center O1of the first patch1may exist on a z-axis.

The first patch1includes a pair of power feeding portions P1Aand P1B. The power feeding portion P1Aon one side is connected to the power feeding line11-1(FIG. 1). The power feeding portion P1Bon the other side is connected to the power feeding line11-2(FIG. 1). The pair of power feeding portions P1Aand P1Bis provided at positions spaced away from the center O1with a certain distance. For example, the power feeding portion P1Aon one side may be provided at a position at which a power-feeding impedance at the position of the power feeding portion P1Aon one side reaches a certain matching impedance. Similarly, the power feeding portion P1Bon the other side may be provided at a position at which the power-feeding impedance at the position of the power feeding portion P1Bon the other side reaches a certain matching impedance. For example, the certain matching impedance may be a value such as 50 ohms and 75 ohms. When the voltage and the phase of a signal that flows to the power feeding portion P1Aon one side, and the voltage and the phase of a signal that flows to the power feeding portion P1Bon the other side are appropriately controlled, the first patch1transmits and receives an arbitrary polarized wave. For example, the first patch1may transmit and receive a linearly polarized wave or a circularly polarized wave. For simplification of control of the polarized wave, an angle P1AO1P1Bmay be substantially 90°.

As illustrated inFIG. 1, the antenna device100includes the second patch2. The second patch2is provided between the ground plate G and the first patch1. For example, the second patch2is provided at a height that is lower than that of the first patch1on one surface side of the ground plate G (inFIG. 1, the z-axis positive direction). To increase the gain of the antenna device100, the second patch2may be provided at a distance far away from the ground plate G, and the position and the height of the second patch2may also be determined with limitation for miniaturization. For example, the second patch2may be provided at a height of approximately 3.0 mm from the ground plate G. The second patch2may be formed from an appropriate arbitrary conductive material with high conductivity. For example, the second patch2may be formed from copper (Cu), gold (Au), silver (Ag), stainless steel, and the like.

FIG. 5illustrates an example of a second patch. InFIG. 5, a plan view of the second patch2illustrated inFIG. 1is illustrated. The second patch2may have a shape, a size, and the like to resonate with a second frequency. The second frequency may be an appropriate arbitrary frequency lower than the first frequency. For example, the second frequency may be set to a frequency band of 2 GHz. The second patch2may have a second contour having a planar shape that is symmetric about the center O2. For example, the second patch2may have a shape such as a rectangular shape, a circular shape, and a polygonal shape in a plan view. InFIGS. 1 and 5, the second patch2may have a circular contour. For example, the second patch2may have a circular contour in which a diameter length is approximately 60 mm, and may have a thickness of approximately 50 μm. With regard toFIGS. 1, 2, and 5, the origin OGin the ground plate G, the center O1of the first patch1, and the center O2of the second patch2may exist on the z-axis.

The second patch2includes a pair of power feeding portions P2Aand P2B. The power feeding portion P2Aon one side is coupled to the power feeding line21-1(FIG. 1). The power feeding portion P2Bon the other side is connected to the power feeding line21-2(FIG. 1). The pair of power feeding portions P2Aand P2Bis provided at positions spaced away from the center O2with a certain distance. For example, the power feeding portion P2Aon one side may be provided at a position at which a power-feeding impedance at the position of the power feeding portion P2Aon one side reaches a certain matching impedance. Similarly, the power feeding portion P2Bon the other side may be provided at a position at which a power-feeding impedance at the position of the power feeding portion P2Bon the other side reaches a certain matching impedance. For example, the certain matching impedance may be a value such as 50 ohms and 75 ohms. When the voltage and the phase of a signal that flows through the power feeding portion P2Aon one side, and the voltage and the phase of a signal that flows through the power feeding portion P2Bon the other side are appropriately controlled, the second patch2transmits and receives an arbitrary polarized wave. For example, the second patch2may transmit and receive a linearly polarized wave or a circularly polarized wave. For simplification of control of the polarized wave, an angle P2AO2P2Bmay be substantially 90°.

The second patch2includes a slit. The slit forms an elongated hole obtained by removing a conductive material. InFIGS. 1 and 5, a first slit24-1is formed in a first quadrant (x>0, y>0), and a second slit24-2is formed in a second quadrant (x<0, y>0), a third slit24-3is formed in a third quadrant (x<0, y<0), and a fourth slit24-4is formed at a fourth quadrant (x>0, y<0). A slit position, a slit number, a slit shape, and the like which are illustrated inFIGS. 1 and 5are illustrative only, and one or more slits having an appropriate arbitrary shape may be formed. Each of the slits may have a shape conforming to at least a part of the contour of the first patch1in a plan view. For example, as illustrated inFIG. 5, a region of the first slit24-1may overlap a part of the square contour of the first patch1, for example, a portion that pertains to the first quadrant. Similarly, a region of the second slit24-2may overlap a part of the square contour of the first patch1, for example, a portion that pertains to the second quadrant. A region of the third slit24-3may overlap a part of the square contour of the first patch1, for example, a portion that pertains to the third quadrant. A region of the fourth slit24-4may overlap a part of the square contour of the first patch1, for example, a portion that pertains to the fourth quadrant.

The power feeding line11-1, which extends from the power feeding portion P1Aof the first patch1, penetrates through the first slit24-1and penetrates through the penetration hole13-1of the ground plate G. On an inner side of a hole formed by the first slit24-1illustrated inFIG. 5, a portion other than the power feeding line11-1is filled with an insulating material. The insulating material in the hole exists to surround the power feeding line11-1, and thus the power feeding line11-1penetrates through the slit24-1without electrical contact with the second patch2. Similarly, the power feeding line11-2, which extends from the power feeding portion P1Bof the first patch1, penetrates through the third slit24-3and penetrates through the penetration hole13-2of the ground plate G. On an inner side of a hole formed by the third slit24-3, a portion other than the power feeding line11-2is filled with an insulating material. The insulating material in the hole exists to surround the power feeding line11-2, and thus the power feeding line11-2penetrates through the slit24-2without electrical contact with the second patch2. Holes formed by the second and fourth slits24-2and24-4are filled with the insulating material, respectively.

The first to fourth slits24-1to24-4which are formed in the second patch2may be formed in various manners in accordance with the shape of the first patch1. The number of slits may be four, or an arbitrary number that is equal to or greater than 1. For example, the slit may be formed at a plurality of positions which are symmetric about the center O2so as to equalize control of a polarized wave with respect to an x-axis direction, and control of a polarized wave with respect to a y-axis direction.

FIG. 6illustrates an example of a slit. The slit illustrated inFIG. 6may be the fourth slit24-4illustrated inFIG. 5. The slit has a length Dx in the x-axis direction, and a length Dy and a width w in the y-axis direction. The total of the length Dx in the x-axis direction and the length Dy in the y-axis direction represents the length of the slit, and the width w represents the slit width. The same length and width may be set in the other slits24-1,24-2, and24-3. InFIG. 6, the slit has an L-shape that is bent in accordance with the angle of the first patch1.

FIG. 7illustrates an example of a slit. The slit illustrated inFIG. 7has a strip shape that is not bent. InFIG. 7, a strip-shaped slit71having a length Dx in the x-axis direction and a width w, and a strip-shaped slit72having a length Dy in the y-axis direction and a width w are formed.

FIG. 8illustrates an example of the slit. Unlike inFIGS. 1, 5, 6, and 7, inFIG. 8, the first patch1is assumed to have a curvature shape or a circular shape of a radius R. InFIG. 8, a slit81is formed along an arc having a width w and the radius R. The length of the arc may represent the length of the slit.

As illustrated inFIG. 1, the antenna device100includes an inter-patch connection portion12that electrically couples a central portion (region including the center O1) of the first patch1and a central portion (region including the center O2) of the second patch2. The electrical connection may be short-circuited. The inter-patch connection portion12may be formed as one line conforming to a line segment (central line or central axis O1O2) that couples the center O1of the first patch1and the center O2of the second patch2, or may be formed as a plurality of lines (a bundle of lines). In a case where the inter-patch connection portion12is formed as the plurality of lines along the central line O1O2, the plurality of lines may be disposed at positions which are symmetric about the central line O1O2so as to equalize positional relationships with respect to the pair of power feeding portions P1Aand P1B(or P2Aand P2B). The term “symmetric about the central line” represents line symmetry or approximate line symmetry about the central line. The term “symmetric about the central line” represents point symmetry on a cross-section perpendicular to the central line or approximate point symmetry on a cross-section perpendicular to the central line.

FIG. 9illustrates an example of a patch connection portion. InFIG. 9, four lines12-1to12-4are disposed at positions which are symmetric about the central line O1O2along the z-axis.

FIG. 10illustrates an example of a plan view of an antenna device. The antenna device illustrated inFIG. 10may be the antenna device100illustrated inFIG. 1.

FIG. 11illustrates an example of a cross-sectional view of an antenna device.FIG. 11illustrates a cross-sectional view taken along line I-I illustrated inFIG. 10. The antenna device100includes a ground plate G, a first insulating layer10provided on the ground plate G, a second patch2provided on the first insulating layer10, a second insulating layer20provided on the second patch2, and a first patch1provided on the second insulating layer20. The first and second insulating layers10and20may be formed by using an existing insulating substrate, and may be formed by using a process of forming and processing an insulating material. The first and second insulating layers10and20may be formed from an appropriate arbitrary material. For example, materials such as a glass epoxy resin, styrene foam, a fluorine resin, ceramics, and Teflon (registered trademark) may be used. To suppress energy loss, a material having a small dielectric tangent (tan δ) may be used. For reduction in weight of the antenna device, a material such as the styrene foam may be used.

InFIG. 11, the power feeding line21-1, which is coupled to the power feeding portion P2Aof the second patch2, penetrates through the first insulating layer10, penetrates through the ground plate G through the penetration hole23-1, and is coupled to the inner conductor of the coaxial cable25-1.

FIG. 12illustrates an example of a cross-sectional view of an antenna device.FIG. 12illustrates a cross-sectional view taken along line II-II illustrated inFIG. 10. InFIG. 12, the inter-patch connection portion12that couples the first patch1and the second patch2penetrates through the second insulating layer20. InFIG. 12, the power feeding line21-2, which is coupled to the power feeding portion P2Bof the second patch2, penetrates through the first insulating layer10, penetrates through the ground plate G through the penetration hole23-2, and is coupled to the inner conductor of the coaxial cable25-2.

FIG. 13illustrates an example of a cross-sectional view of an antenna device.FIG. 13illustrates a cross-sectional view taken along line III-III illustrated inFIG. 10. InFIG. 13, the power feeding line11-2, which is coupled to the power feeding portion P1Bof the first patch1, penetrates through the second insulating layer20, penetrates through the third slit24-3, penetrates through the first insulating layer10, penetrates through the ground plate G through the penetration hole13-2, and is coupled to the inner conductor of the coaxial cable15-2.

FIG. 14illustrates an example of a cross-sectional view of an antenna device.FIG. 14illustrates a cross-sectional view taken along line IV-IV illustrated inFIG. 10. InFIG. 14, the power feeding line11-1, which is coupled to the power feeding portion P1Aof the first patch1, penetrates through the second insulating layer20, penetrates the first slit24-1, penetrates through the first insulating layer10, penetrates through the ground plate G through the penetration hole13-1, and is coupled to the inner conductor of the coaxial cable15-1.

The positions of the power feeding portion P1Aand P1Bof the first patch1depend on a wavelength of an electric wave, the material of the insulating layer (for example, a specific dielectric constant), patch size, and the like, and thus the slit may not exist immediately below the power feeding portion P1Aand P1B. In a case where the slit does not exist immediately below the power feeding portion P1Aand P1B, when coupling the power feeding portion P1Aand P1Bto the coaxial cables15-1and15-2at positions immediately below the power feeding portion P1Aand P1B, a penetration hole may be formed separately in the second patch2. The power feeding line may be bent instead of separately providing the penetration hole separately.

FIG. 15illustrates an example of a power feeding line. InFIG. 15, in a case where the position of the power feeding portion P1Bof the first patch1illustrated inFIG. 13deviates toward the right side (an x-axis positive direction) in the drawing, the power feeding line11-2is bent and the third slit24-3is utilized. The power feeding line11-2, which is coupled to the power feeding portion P1Bof the first patch1, penetrates a third insulating layer30, extends between the second and third insulating layers20and30in a direction (an x-axis negative direction) to be distant from the center therebetween, penetrates through the second insulating layer20, and penetrates through the third slit24-3. Similar toFIG. 13, the power feeding line11-2penetrates through the first insulating layer10, penetrates through the ground plate G through the penetration hole13-2, and is coupled to the inner conductor of the coaxial cable15-2.

The antenna device100, which is illustrated inFIG. 1and the like, resonates with the first frequency by the first patch1, and resonates with the second frequency lower than the first frequency by the second patch2. The first and second frequencies may be appropriate arbitrary frequencies. For example, the first frequency may be a frequency that pertains to a frequency band of 5 GHz, and the second frequency may be a frequency that pertains to a frequency band of 2 GHz. For convenience, the first patch1is referred to as a high-frequency patch1, and the second patch2may be referred to as a low-frequency patch2.

FIG. 16illustrates an example of an antenna device.FIG. 16illustrates a circuit diagram of the antenna device100that is illustrated inFIG. 1and the like. In a case of transmitting an electric wave with the high-frequency patch1, when a high-frequency signal is fed from the power feeding circuit35to the pair of power feeding portions P1Aand P1B, an electric wave is transmitted in the z-axis direction. When the voltage and the phase of the high-frequency signal that flows to each of the pair of power feeding portions P1Aand P1Bare appropriately controlled, an arbitrary polarized wave such as a linearly polarized wave, an elliptically polarized wave, and a circularly polarized wave is generated. In a case of receiving an electric wave by the high-frequency patch1, a high-frequency signal is generated in the pair of power feeding portions P1Aand P1Bdue to the electric wave received from the z-axis direction, and the generated high-frequency signal is applied to the power feeding circuit35. This is true of the low-frequency patch2, and an arbitrary polarized wave is transmitted and received through the pair of power feeding portions P2Aand P2B.

In a laminated patch antenna that resonates with a plurality of frequencies, a plurality of patches are provided at positions adjacent to each other for miniaturization, and thus the plurality of patches may interfere each other in accordance with frequencies that are used. In the antenna device100, the slits24-1to24-4or the inter-patch connection portion12is formed, and thus the interference or electromagnetic interference is effectively reduced. Accordingly, antenna characteristics such as gain may be improved.

In a simulation with respect to the antenna device, four kinds of antenna models are used in accordance with the existence or non-existence of the slits24-1to24-4and the existence or non-existence of the inter-patch connection portion12. Any antenna model may include the ground plate, the high-frequency patch, and the low-frequency patch provided between the ground plate and the high-frequency patch.

FIG. 17illustrates an example of classification of a graph illustrating a simulation result.FIG. 17illustrates that a graph illustrating the simulation result corresponds to which model among the four kinds of antenna models. The antenna device100illustrated inFIG. 1and the like corresponds to an antenna model including a slit24-i(i=1 to 4), and the inter-patch connection portion12.

A graph illustrated with “lower patch S11” illustrates a return loss in a case where a signal is fed to the low-frequency patch, for example, the second patch. The return loss is expressed by S11that is one of S parameters of two-terminal pair circuit. The return loss may be referred to as a reflection loss.

A graph illustrated with “higher patch S11” illustrates a return loss in a case where a signal is fed to the high-frequency patch (first patch).

A graph illustrated with “lower patch S12”illustrates a coupling coefficient in a case where a signal is fed to the low-frequency patch, for example, the second patch. The coupling coefficient is expressed with S12or S21which is one of S parameters of two-terminal pair circuit, and S12equals to S21in a linear system. The coupling coefficient may be referred to as an insertion loss. For example, a graph of the lower patch S12illustrates a signal component that leaks toward the high-frequency patch1side from the low-frequency patch2.

A graph illustrated with “higher patch S21” illustrates a coupling coefficient in a case where a signal is fed to the high-frequency patch, for example, the first patch. For example, the graph of the higher patch S21illustrates a signal component that leaks toward the low-frequency patch2side from the high-frequency patch1.

A graph illustrated with “higher patch gain” illustrates a gain [dBi] in a case where a signal is fed to the high-frequency patch, for example, the first patch. The gain [dBi] indicates energy in the maximum electric wave radiation direction, and is set based on a virtual isotropic antenna.

FIG. 18illustrates an example of frequency dependency of a return loss and a coupling coefficient.FIG. 18illustrates the frequency dependency of the return loss (lower patch S11) and the coupling coefficient (lower patch S12) in a case where a signal is fed to the low-frequency patch of an antenna model in which the slit and the inter-patch connection portion are not provided. The return loss (lower patch S11) decreases to approximately −14 dB in the vicinity of approximately 2.45 GHz, and resonance occurs. In the vicinity of approximately 2.45 GHz, the coupling coefficient (lower patch S12) increases to a value exceeding approximately −4 dB. Accordingly, power fed to the low-frequency patch may leak toward the high-frequency patch side.

FIG. 19illustrates an example of frequency dependency of a coupling coefficient.FIG. 19illustrates the frequency dependency of the coupling coefficient (higher patch S21) in a case where a signal is fed to the high-frequency patch. A graph of “without slit” illustrates the coupling coefficient in a case where a signal is fed to the high-frequency patch of an antenna model in which the slit is not provided but the inter-patch connection portion is provided. A graph of “with slit” illustrates the coupling coefficient in a case where a signal is fed to the high-frequency patch of an antenna model in which the slit and the inter-patch connection portion are provided, for example, the antenna device100illustrated inFIG. 1and the like. In a case of “without slit”, the coupling coefficient S21is approximately −15 dB at approximately 5.2 GHz. The coupling coefficient S21increases as the frequency increases, and exceeds −10 dB at approximately 5.5 GHz or higher. In a case of “with slit”, the coupling coefficient becomes approximately −15 dB from approximately 5 GHz to approximately 5.5 GHz, and decreases as the frequency increases from approximately 5.5 GHz. Accordingly, with regard to a frequency band of at least 5 GHz, when the slit24-i(i=1 to 4) is formed in the antenna device, the coupling coefficient S21of the high-frequency patch with respect to the low-frequency patch may be effectively reduced.

FIG. 20illustrates an example of frequency dependency of a gain.FIG. 20illustrates the frequency dependency of the gain in a case where a signal is fed to the high-frequency patch. A case of “without slit” and a case of “with slit” may be similar to the cases illustrated inFIG. 19. In a frequency range from approximately 5.1 GHz to approximately 5.7 GHz, the case of “with slit” has a gain that is more excellent than that in the case of “without slit” by approximately 1 dBi or more.

FIG. 21illustrates an example of frequency dependency of a gain. InFIG. 21, the frequency dependency of the gain in a case where a signal is fed to the high-frequency patch is illustrated for each of a horizontally polarized wave and a vertically polarized wave. The antenna model may be an antenna model in which the slit and the inter-patch connection portion are provided, for example, the antenna device100illustrated inFIG. 1and the like. For example, a signal may be fed to only one of the pair of power feeding portions P1Aand P1Bof the high-frequency patch1, for example, only the P1B, and a horizontally polarized wave, for example, an electric wave in which an amplitude direction of an electric field follows the x-axis direction may be generated. A signal may be fed to only one of the pair of power feeding portions P1Aand P1Bof the high-frequency patch1, for example, only P1A, and a vertically polarized wave, for example, an electric wave in which an amplitude direction of an electric field follows the y-axis direction may be generated. As illustrated inFIG. 21, the horizontally polarized wave and the vertically polarized wave have gains which are substantially the same in a range from approximately 5.1 GHz to approximately 5.7 GHz. Accordingly, in the antenna device100, polarized wave control for transmission and reception of various polarized waves may be appropriately executed to equally control the horizontally polarized wave and the vertically polarized wave.

FIG. 22illustrates an example of frequency dependency of a coupling coefficient.FIG. 22illustrates the frequency dependency of the coupling coefficient (lower patch S12) in a case where a signal is fed to the low-frequency patch. A graph of “without inter-patch connection portion” illustrates the coupling coefficient S12in a case where a signal is fed to the low-frequency patch of an antenna model in which the slit is provided but the inter-patch connection portion is not provided. A graph of “with inter-patch connection portion” illustrates the coupling coefficient S12in a case where a signal is fed to the low-frequency patch of an antenna model in which the slit and the inter-patch connection portion are provided, for example, the antenna device100illustrated inFIG. 1and the like. In the case of “without inter-patch connection portion”, the coupling coefficient S12increases as the frequency increases from approximately 2 GHz, decreases after reaching approximately −4 dB in the vicinity of approximately 2.45 GHz, and decreases to approximately −15 dB at approximately 3 GHz. In the case of “with inter-patch connection portion”, the coupling coefficient S12also increases as the frequency increases from approximately 2.1 GHz. However, the coupling coefficient S12merely becomes approximately −10 dB in the vicinity of approximately 2.45 GHz, and then decreases up to approximately −23 dB at approximately 3.4 GHz. Accordingly, with regard to a frequency band of at least 2 GHz, when the inter-patch connection portion12is provided, the coupling coefficient S12of the low-frequency patch with respect to the high-frequency patch may be reduced.

FIG. 23illustrates an example of an energy intensity of an electric wave. The energy intensity of an electric wave, which is radiated in a case where a signal of a frequency of approximately 2.45 GHz is fed to the low-frequency patch, is illustrated inFIG. 23. A case of “without inter-patch connection portion” illustrated on a left side ofFIG. 23illustrates a beam that is radiated in a case where a signal is fed to the low-frequency patch of an antenna model in which the slit is provided but the inter-patch interconnection portion is not provided. The beam obtains a gain of approximately 6.9 dBi. A case of “with inter-patch connection portion” which is illustrated on a right side ofFIG. 23illustrates a beam that is radiated in a case where a signal is fed to an antenna model in which the slit and the inter-patch connection portion are provided, for example, the low-frequency patch of the antenna device100illustrated inFIG. 1and the like. The beam obtains a gain of approximately 7.9 dBi. According to this, with regard to a frequency band of at least 2 GHz, when the inter-patch connection portion12is provided, the gain may be improved.

FIG. 24illustrates an example of frequency dependency of a return loss and a coupling coefficient.FIG. 24illustrates the frequency dependency, the return loss (lower patch S11), and the coupling coefficient (lower patch S12) in a case where a signal is fed to the low-frequency patch. An antenna model in which the slit is not provided but the inter-patch connection portion is provided is used. The return loss (lower patch S11) decreases to approximately −18 dB in the vicinity of approximately 2.45 GHz, and resonance occurs. The coupling coefficient (lower patch S12) is approximately −7.5 dB in the vicinity of approximately 2.45 GHz. The coupling coefficient (lower patch S12) is relatively great, approximately −12 dB, in the vicinity of approximately 5.3 GHz at which the high-frequency patch operates. According to this, a high-frequency component among signals to be fed to the low-frequency patch may slightly leak to the high-frequency patch.

FIG. 25illustrates an example of frequency dependency of a return loss and a coupling coefficient.FIG. 25illustrates the frequency dependency of the return loss (lower patch S11) and the coupling coefficient (lower patch S12) in a case where a signal is fed to the low-frequency patch. An antenna model in which the slit and the inter-patch connection portion are provided, for example, the antenna device100illustrated inFIG. 1and the like may be used. A graph of the coupling coefficient (lower patch S12) illustrated inFIG. 25may be substantially the same as the graph of “with inter-patch connection portion” illustrated inFIG. 22. The return loss (lower patch S11) decreases to approximately −28 dB in the vicinity of approximately 2.45 GHz, and resonance occurs. The return loss (lower patch S11) also decreases to approximately −20 dB in the vicinity of approximately 4.4 GHz. However, differently from the example illustrated inFIG. 24, the return loss in the vicinity of approximately 5.3 GHz with which the high-frequency patch operates is retained to be high. The coupling coefficient (lower patch S12) is suppressed to approximately −10 dB in the vicinity of approximately 2.45 GHz. Unlike in the example illustrated inFIG. 24, the coupling coefficient (lower patch S12) is suppressed to a value as small as approximately −22 dB in the vicinity of approximately 5.3 GHz with which the high-frequency patch operates. Accordingly, in a case where a signal is fed to the low-frequency patch, coupling may be suppressed not only in the vicinity of approximately 2.45 GHz but also in the vicinity of approximately 5 GHz.

FIG. 26illustrates an example of a return loss with respect to a low-frequency patch and a return loss with respect to the high-frequency patch.FIG. 26illustrates the return loss (lower patch S11) with respect to the low-frequency patch and the return loss (higher patch S11) with respect to the high-frequency patch of the antenna device100illustrated inFIG. 1and the like. A graph of the return loss (lower patch S11) illustrated inFIG. 26may be substantially the same as the graph of the return loss (lower patch S11) illustrated inFIG. 25. The return loss (lower patch S11) with respect to the low-frequency patch is as low as approximately −28 dB at a desired frequency of approximately 2.45 GHz, and resonance occurs with the frequency. The return loss (higher patch S11) with respect to the high-frequency patch is as low as approximately −26 dB at a desired frequency of approximately 5.3 GHz, and resonance occurs with the frequency.

The low-frequency patch2may resonate with approximately 2.45 GHz (FIG. 26), and the coupling coefficient (lower patch S12) of the low-frequency patch2with respect to the high-frequency patch1may be reduced in the vicinity of approximately 2.45 GHz and approximately 5 GHz, (FIG. 25). The high-frequency patch1may resonate in the vicinity of approximately 5.3 GHz (FIG. 26), and the coupling coefficient (higher patch S21) of the high-frequency patch1with respect to the low-frequency patch2may be reduced in the vicinity of approximately 5.3 GHz (“with slit” inFIG. 19).

As shown in a simulation result, in the antenna device100, the slits24-1to24-4and the inter-patch connection portion12are formed, and thus coupling between patches is suppressed, and thus antenna characteristics such as a gain may be improved.

The slits24-1to24-4are formed by partially removing a conductive material of the low-frequency patch2(second patch2), and thus a kind of opening is formed between the high-frequency patch1(first patch1) and the ground plate G. In the opening, the conductive material of the low-frequency patch2is partially removed, and thus coupling between the high-frequency patch1and the low-frequency patch2may be suppressed. The opening promotes a mutual operation between the high-frequency patch1and the ground plate G, for example, appropriate formation of a line of electric force which ranges from the ground plate G to an end of the high-frequency patch1, and the like. According to this, the high-frequency patch1may appropriately transmit and receive an electric wave. To promote an operation of the high-frequency patch1by suppressing coupling between the high-frequency patch1and the low-frequency patch2, a wide opening may be formed in the slit.

An electromagnetic field that is generated between the high-frequency patch1and the low-frequency patch2is stronger on an end side in comparison to the central portion, and thus an electromagnetic field that occurs at the end has a greater effect on an electric wave, which is transmitted and received, in comparison to the central portion. To promote an operation of the high-frequency patch1, at least the end of the high-frequency patch1may overlap the slit in a plane view.

On the other hand, the degree of suppression of the coupling between the high-frequency patch1and the low-frequency patch2may be adjusted by an area of the opening formed by the slit, and the like. For example, the slit width w and the slit length (Dx, Dy, and the like) which are described inFIGS. 6 to 8may be adjusted. For example, the slit width w may be narrow so as to adjust the degree of suppression of the coupling between the high-frequency patch1and the low-frequency patch2in detail over a wide range. When the slit width w is excessively narrow, a function as the opening is less likely to be exhibited, and thus the slit width w may be large to a certain degree.

In a case where the slit and the inter-patch connection portion are not provided, the high-frequency patch functions like a passive element with respect to the low-frequency patch. Accordingly, a signal that is fed to the low-frequency patch may leak to the high-frequency patch in accordance with a frequency. For example, as illustrated inFIG. 18, in a case where the slit and the inter-patch connection portion are not provided, the coupling coefficient S12is relatively large not only in the vicinity of approximately 2.45 GHz but also in the vicinity of approximately 5.3 GHz, and thus loss due to leakage may occur. When the inter-patch connection portion12directly couples the high-frequency patch1and the low-frequency patch2, a circuit constant, which allows resonance or coupling to occur, is changed in comparison to a case where the inter-patch connection portion12does not exist. As illustrated inFIG. 25, the coupling coefficient (lower patch S12) in a case of feeding power to the low-frequency patch2is suppressed to a value as low as approximately −22 dB at a frequency of approximately 5.5 GHz, and thus with regard to a frequency in the vicinity of the above-described frequency, coupling of the low-frequency patch2to the high-frequency patch1may be effectively suppressed.

The antenna device100may resonate with two frequencies or three or more frequencies. The number of patches which are provided on the ground plate G of the antenna device100may be two, or three or more.

FIG. 27illustrates an example of an antenna device. InFIG. 27, a circuit diagram of an antenna device300is illustrated. The antenna device300includes a ground plate G, a first patch1that is provided at a position spaced away from the ground plate G with a certain distance, a second patch2that is provided between the first patch1and the ground plate G, and a third patch3that is provided between the second patch and the ground plate G. Power is fed to the first patch1by a pair of power feeding portions P1Aand P1B, and the first patch1resonates with a first frequency. Power is fed to the second patch2by a pair of power feeding portions P2Aand P2B, and the second patch2resonates with a second frequency. Power is fed to the third patch3by a pair of power feeding portions P3Aand P3B, and the third patch3resonates with a third frequency. InFIG. 27, the first and second patches1and2are coupled by an inter-patch connection portion12. Alternatively or additionally, the second and third patches2and3may be coupled by an inter-patch connection portion. The first, second, and third frequencies may be different from each other, and among the three frequencies, two frequencies may be the same as each other. The first frequency may be higher than the third frequency, and the second frequency may be equal to or lower than the first frequency and equal to or higher than the third frequency.

FIG. 28illustrates an example of n patches.FIG. 28illustrates a case where n patches1, . . . , and n exist on the ground plate G. n may be an integer of two or greater. With regard to an arbitrary k that is equal to or greater than 1 and equal to or less than (n−1). A kthpatch k and a (k+1)thpatch (k+1) may be coupled by an inter-patch connection portion. Frequencies with which individual patches resonate may be different from each other. Two or more frequencies may be the same as each other (case of n≧3). A frequency with which the first patch1resonates is higher than a frequency with which an nthpatch n resonates, and a frequency with which the kthpatch resonates is equal to or higher than a frequency with which the (k+1)thpatch resonates.

FIG. 29illustrates an example of a first patch.FIG. 30illustrates an example of a second patch.FIG. 31illustrates an example of a third patch.FIG. 32illustrates an example of a ground plate. InFIGS. 29 to 32, plan views of a plurality of conductive layers of the antenna device300as illustrated inFIG. 27are illustrated. The plurality of conductive layers include the first to third patches1,2, and3, and the ground plate G.

InFIG. 29, a plan view of the first patch1of the antenna device300is illustrated. The first patch1has a shape (square shape inFIG. 29) symmetric about the center O1that is positioned on the z-axis, and resonates with the first frequency. The first patch1includes a pair of power feeding portions P1Aand P1B. The power feeding portion P1Aon one side may be positioned at an end portion of a first quadrant which is close to the y-axis, the power feeding portion P1Bon the other side may be positioned at an end portion of a third quadrant which is close to the x-axis, and an angle P1AO1P1Bmay be substantially 90°. When the voltage and the phase of a signal that flows to each of the pair of power feeding portions P1Aand P1Bare controlled, various polarized waves may be transmitted and received.

InFIG. 30, a plan view of the second patch2of the antenna device300is illustrated. The second patch2has a shape (square shape inFIG. 30) symmetric about the center O2that is positioned on the z-axis, and resonates with the second frequency. The second patch2may have a shape which is larger than that of the first patch1. The second patch2includes a pair of power feeding portions P2Aand P2B. The power feeding portion P2Aon one side may be positioned at an end portion of a first quadrant which is close to the x-axis, the power feeding portion P2Bon the other side may be positioned at an end portion of a third quadrant which is close to the y-axis, and an angle P2AO2P2Bmay be substantially 90°. When the voltage and the phase of a signal that flows to each of the pair of power feeding portions P2Aand P2Bare controlled, various polarized waves may be transmitted and received.

The second patch2includes first to fourth L-shaped slits24-1to24-4which conform to the contour of the first patch1in the first to fourth quadrants. The power feeding line11-1, which is coupled to the power feeding portion P1Aon one side of the first patch1, penetrates through the first slit24-1. The power feeding line11-2, which is coupled to the power feeding portion P1Bon the other side of the first patch1, penetrates through the third slit24-3.

At the central portion including the center O2, the second patch2is coupled to the central portion of the first patch1by the inter-patch connection portion12.

InFIG. 31, a plan view of the third patch3of the antenna device300is illustrated. The third patch3has a shape (square shape inFIG. 31) symmetric about the center O3that is positioned on the z-axis, and resonates with the third frequency. The third patch3may have a shape larger than that of the second patch2.

The third patch3includes first to fourth L-shaped slits34-1to34-4which conform to the contour of the second patch2in the first to fourth quadrants. The power feeding line11-1, which is coupled to the power feeding portion P1Aon one side of the first patch1, penetrates through the first slit34-1at a position of the first quadrant which is close to the y-axis. The power feeding line21-1, which is coupled to the power feeding portion P2Aon one side of the second patch2, penetrates through the first slit34-1at a position of the first quadrant which is close to the x-axis. The power feeding line11-2, which is coupled to the power feeding portion P1Bon the other side of the first patch1, penetrates through the third slit34-3at a position of the third quadrant which is close to the x-axis. The power feeding line21-2, which is coupled to the power feeding portion P2Bon the other side of the second patch2, penetrates through the third slit34-3at a position of the third quadrant which is close to the y-axis.

The third patch3includes a pair of power feeding portions P3Aand P3B. The power feeding portion P3Aon one side is positioned on the x-axis which is close to the power feeding line21-1between the first slit34-1and the fourth slit34-4. The power feeding portion P3Bon the other side is positioned on the y-axis which is close to the power feeding line21-2between the third slit34-3and the fourth slit34-4. With regard to the pair of power feeding portions P3Aand P3B, an angle P3AO3P3Bmay be substantially 90°. When the voltage and the phase of a signal that flows to each of the pair of power feeding portions P3Aand P3Bare controlled, various polarized waves may be transmitted and received.

InFIG. 32, a plan view of the ground plate G of the antenna device300is illustrated. The two power feeding lines11-1and11-2, which are coupled to the pair of power feeding portions P1Aand P1Bof the first patch1, pass through penetration holes13-1and13-2, respectively, penetrate through the ground plate G, and are coupled to a power feeding circuit inFIG. 32. The two power feeding lines21-1and21-2, which are coupled to the pair of power feeding portions P2Aand P2Bof the second patch2, pass through penetration holes23-1and23-2, respectively, penetrate through the ground plate G, and are coupled to the power feeding circuit inFIG. 32. The two power feeding lines31-1and31-2, which are coupled to the pair of power feeding portions P3Aand P3Bof the third patch3, pass through penetration holes33-1and33-2, respectively, penetrate through the ground plate G, and are coupled to the power feeding circuit inFIG. 32.

Positional relationships of the six power feeding lines illustrated inFIGS. 29 to 32are illustrative only, and other appropriate arrangements may be used.

In the antenna device, a laminated patch antenna in which a plurality of patches are laminated is formed, and the size of the patches gradually decreases as it goes away from the ground plate, and a patch that is far away from the ground plate resonates with a frequency higher than that of a patch that is close to the ground plate. When the patches are laminated, an area occupied by the antenna device corresponds to an area of one patch, and thus simplification and miniaturization of the antenna device may be achieved.

The plurality of patches are laminated with a positional relationship in which the centers are aligned, and thus power is fed to the plurality of patches by a pair of power feeding portions. When lamination is performed by aligning the centers of the patches, a horizontally polarized wave and a vertically polarized wave are controlled in a substantially equal manner, and thus control of polarized waves may be appropriately executed in the antenna device.

The second patch2that is positioned between the first patch1and the ground plate G includes the slits24-1to24-4, and thus an opening is formed between the first patch1and the ground plate G. The opening is formed by removing a part of the second patch2, and thus coupling between the first patch1and the second patch2in the antenna device may be suppressed. A mutual operation between the first patch1and the ground plate G is promoted through the opening, and thus an operation of the first patch1in the antenna device may be promoted.

The first patch and the second patch are coupled to each other by the inter-patch connection portion, and thus a circuit constant during operation of the second patch is different from a circuit constant in a case where the inter-patch connection portion does not exist. In the antenna device, when changing the circuit constant during operation of the second patch, coupling between the first patch and the second patch may be suppressed.

In the antenna device, the coupling between the first patch and the second patch is suppressed, and thus antenna characteristics such as a gain may be improved.

The antenna device may resonate with frequencies of a frequency band of 2 GHz and a frequency band of 5 GHz. The embodiments disclosed herein are not limited to the above-described examples, and various modification examples, variations, alternative examples, substitution examples, and the like may be applied. The coordinates (and the coordinate system) which are used to explain geometrical positional relationships such as a structure and a shape are illustrative only, and other appropriate coordinates (and a coordinate system) may be used. The numerical values are illustrative only, and other appropriate values may be used.