Patent Grant
9905919
1. Field of the Invention
The present invention generally relates to an antenna, an antenna device, and a wireless device such as a mobile phone.
2. Description of the Related Art
Techniques are known for controlling the directivity of an antenna by switching a connection destination of a feeding point. For example, Japanese Laid-Open Patent Publication No. 2012-186562 (Patent Document 1) discloses an antenna including a switch for switching the directivity of a radiating conductor by controlling a feeding point to come into contact with either one of two end points of the radiating conductor.
On the other hand, Japanese Patent No. 4422767 (Patent Document 2) discloses an antenna that is operable in multiple frequency bands by having a feeding element and a parasitic element that are coupled without being in contact.
However, it has been difficult to control the directivity of an antenna that has a contactless feeding system as disclosed in Patent Document 2 where a feeding element connected to a feeding point is coupled to a radiating element (parasitic element) without being in contact. For example, the switching technique disclosed in Patent Document 1 that involves controlling the directivity of an antenna by switching the connection point of a feeding element to a radiating element cannot be implemented in the antenna disclosed in Patent Document 2 because the feeding element and the radiating element have to be coupled without being in contact. Also, various constrains may be imposed on the arrangement and shape of the feeding element in order to prevent coupling at unintended locations when a connection point is switched, for example.
In view of the above, there is a demand for a technique for controlling the directivity of an antenna having a feeding element and a radiating element that are coupled without being in contact.
An aspect of the present invention relates to implementing a technique for controlling the directivity of an antenna, an antenna device, and a wireless device having a feeding element and a radiating element that are coupled without being in contact.
According to one aspect of the present invention, an antenna, an antenna device, and a wireless device are provided that include a feeding element that is connected to a feeding point; a first radiating element that is spaced apart from the feeding element and is fed by being coupled to the feeding element through electromagnetic field coupling to function as a radiating conductor; a second radiating element that is spaced apart from the feeding element and is fed by being coupled to the feeding element through electromagnetic field coupling to function as a radiating conductor; a first control element that is connected to the feeding element via a first impedance variable unit and is arranged such that when an impedance of the first impedance variable unit at a resonant frequency of the first radiating element is decreased, the electromagnetic field coupling between the feeding element and the first radiating element is weakened and the function of the first radiating element as the radiating conductor is degraded; a second control element that is connected to the feeding element via a second impedance variable unit and is arranged such that when an impedance of the second impedance variable unit at a resonant frequency of the second radiating element is decreased, the electromagnetic field coupling between the feeding element and the second radiating element is weakened and the function of the second radiating element as the radiating conductor is degraded; and a control unit that controls the first impedance variable unit to adjust the connection between the feeding element and the first control element, and controls the second impedance variable unit to adjust the connection between the feeding element and the second control element.
According to another aspect of the present invention, an antenna, an antenna device, and a wireless device are provided that include a feeding element that is connected to a feeding point; a first radiating element that is spaced apart from the feeding element and is fed by being coupled to the feeding element through electromagnetic field coupling to function as a radiating element; a second radiating element that is spaced apart from the feeding element and is fed by being coupled to the feeding element through electromagnetic field coupling to function as a radiating element; a first control element that is connected to the feeding element via a first impedance variable unit; a second control element that is connected to the feeding element via a second impedance variable unit; and a control unit that controls the first impedance variable unit to adjust the connection between the feeding element and the first control element, and controls the second impedance variable unit to adjust the connection between the feeding element and the second control element. The first control element is arranged such that a high impedance portion of the first control element having a high impedance at a resonant frequency of the first radiating element and a low impedance portion of the first radiating element having a low impedance at the resonant frequency of the first radiating element are positioned close to each other, and the second control element is arranged such that a high impedance portion of the second control element having a high impedance at a resonant frequency of the second radiating element and a low impedance portion of the second radiating element having a low impedance at the resonant frequency of the second radiating element are positioned close to each other.
In the following, embodiments of the present invention will be described with reference to the accompanying drawings.
<Antenna 1>
The antenna 1 includes a feeding point 11, a ground plane 70, a feeding element 20, a first radiating element 30, a second radiating element 40, a first feeding portion 35, a second feeding portion 45, a first control element 50, a second control element 60, and an impedance control unit 120. Note that in the following descriptions, the first radiating element 30, the second radiating element 40, the first feeding portion 35, the second feeding portion 45, the first control element 50, and the second control element 60 may simply be referred to as “radiating element 30,” “radiating element 40,” “feeding portion 35,” “feeding portion 45,” “control element 50,” and “control element 60,” respectively. Note that the feeding portion 35 is a feeding portion for feeding the radiating element 30, and the feeding portion 45 is a feeding portion for feeding the radiating element 40. That is, the feeding portions 35 and 45 do not constitute feeding portions for the antenna 1. The feeding point 11 constitutes the feeding portion for feeding the antenna 1.
The feeding point 11 is a feeding portion that is connected to a predetermined transmission line or a feeding line that uses the ground plane 70. Specific examples of a predetermined transmission line includes a microstrip line, a strip line, a coplanar waveguide with a ground plane (coplanar waveguide having a ground plane arranged on a surface opposing a conductor surface), and the like. Specific examples of a feeding line include a feeder line, a coaxial cable, and the like. The feeding point 11 may be arranged at a central portion of an outer edge 71 of the ground plane 70.
The feeding element 20 is a conductor that is connected to the feeding point 11 that uses the ground plane 70 as a ground reference. The feeding element 20 may be connected to a feeding circuit that is mounted on a substrate 80 (e.g., an integrated circuit such as an IC chip, which is not shown) via the feeding point 11, for example. The feeding element 20 and the feeding circuit may be interconnected via one or more of the various types of transmission lines and feeding lines described above.
The feeding element 20 is a conductor that is arranged a predetermined distance apart from the radiating element 30 and the radiating element 40. For example, the feeding element 20 may be spaced apart from the radiating element 30 and the radiating element 40 by a gap having a parallel direction component in the Z-axis.
In the example illustrated in
The feeding element 20 is capable of feeding the radiating element 30 via the feeding portion 35 of the radiating element 30 without being in contact with the radiating element 30. Also, the feeding element 20 is capable of feeding the radiating element 40 via the feeding portion 45 of the radiating element 40 without being in contact with the radiating element 40. For example, the feeding element 20 may be a linear conductor having at least a portion of the feeding element 20 and the ground plane 70 arranged to not overlap in plan view from a direction normal to the ground plane 70. Note that a direction normal to the ground plane 70 corresponds to a direction parallel to the Z-axis in
The feeding element 20 may be a linear conductor having a linear conductor portion extending from the feeding point 11, as a starting point, to an end portion 21, in a direction away from the outer edge 71 of the ground plane 70, which is parallel to the XY plane. The end portion 21 is a portion located at the tip of the feeding element 20 in the direction away from the outer edge 71. In
Note that although
The feeding element 20 extends from the feeding point 11 to the end portion 21 in a direction toward a gap 130 formed between one end portion 33 of the radiating element 30 and one end portion 43 of the radiating element 40 in plan view from a direction normal to the ground plane 70. The feeding element 20 includes the end portion 21, which is spaced apart by a predetermined distance from the end portion 33 of the radiating element 30 and the end portion 43 of the radiating element 40, and the end portion 21 is positioned in the vicinity of the gap 130.
Note that although
The radiating element 30 is a radiating conductor that includes the end portion 33 and another end portion 34, and extends linearly from the end portion 33 to the other end portion 34. Note that the end portion 33 and the end portion 34 are open ends that are not connected to another conductor. For example, the radiating element 30 may be a linear conductor having at least a portion of the radiating element 30 and the ground plane 70 arranged to not overlap in plan view from a direction normal to the ground plane 70.
For example, the radiating element 30 may be a linear conductor having a linear radiating conductor portion arranged along the outer edge 71 of the ground plane 70. The radiating element 30 may include a conductor portion 31 that is spaced apart from the outer edge 71 by a predetermined shortest distance and extends in a direction parallel to the outer edge 71 facing the outer edge 71 of the ground plane 70, for example. Note that a direction parallel to the outer edge 71 corresponds to a direction parallel to the X-axis in
Note that although
The radiating element 40 may have a configuration identical or similar to the configuration of the radiating element 30 as described above. As such, detailed descriptions thereof are omitted. The radiating element 40 is an antenna conductor that includes one end portion 43 and another end portion 44, and extends linearly from the end portion 43 to the other end portion 44. The radiating element 40 may include a conductor portion 41 that is spaced apart from the outer edge 71 by a predetermined shortest distance and extends in a direction parallel to the outer edge 71 facing the outer edge 71 of the ground plane 70, for example.
The radiating element 30 and the radiating element 40 are conductors that extend in different directions from each other. That is, the radiating element 30 and the radiating element 40 extend in directions away from each other from the feeding element 20. Note that although
The control element 50 is a conductor that is spaced apart by a predetermined distance from the radiating element 30. For example, the control element 50 may be spaced apart from the radiating elements 30 by a gap having a parallel direction component in the Z-axis. The control element 50 is connected to the end portion 21 of the feeding element 20 via an impedance control unit 120 and extends linearly from the impedance control unit 120 to an end portion 51. The end portion 51 is an open end that is not connected to another conductor. For example, the control element 50 may be a linear conductor having at least a portion of the control element 50 and the ground plane 70 arranged so as not to overlap in plan view from a direction normal to the ground plane 70.
For example, the control element 50 may be a linear conductor having a linear conductor portion arranged along the radiating element 30. Note that although
The control element 60 is a conductor that is spaced apart by a predetermined distance from the radiating element 40. The control element 60 may have a configuration identical or similar to the configuration of the control element 50 as described above. As such, detailed descriptions thereof are omitted. The control element 60 is connected to the end portion 21 of the feeding element 20 via the impedance control unit 120 and extends linearly from the impedance control unit 120 to an end portion 61.
Note that although
For example, in
In a case where the radiating elements 30 and 40 are arranged on the surface of the cover glass, the radiating elements 30 and 40 may be formed by applying a conductive paste such as copper or silver on the surface of the cover glass and performing a firing process thereon, for example. Note that the conductive paste used in this case is preferably a type that can be fired at a sufficiently low temperature so as to not affect the reinforced properties of the chemically reinforced glass used for the cover glass. Also, a plating process may be performed in order to prevent deterioration of the conductors due to oxidation, for example. Also, a decorative printing process may be performed on the cover glass and the conductors may be formed on the decorative printed portions. Also, in a case where a black concealing layer is arranged at the peripheral edge of the cover glass for the purpose of concealing wiring and the like, the radiating elements 30 and 40 may be formed on the black concealing layer, for example.
Also, the positions of the feeding element 20, the radiating elements 30 and 40, the control elements 50 and 60, and the ground plane 70 with respect to a height direction parallel to the Z-axis may be different from one another, partially the same, or all the same.
Also, in some examples, one feeding element may be configured to feed a plurality of radiating elements. By utilizing a plurality of radiating elements, multi-band operation, wide-band operation, and/or directivity control may be facilitated, for example. Also, in some examples, a plurality of antennas may be installed in one wireless communication device.
Note that although
In one example, a chip component including the feeding element 20 and a medium in contact with the feeding element 20 may be mounted to the substrate 80. In this way, the feeding element 20 that is in contact with the medium may be easily mounted to the substrate 80.
The substrate 80 may be made from a dielectric material, a magnetic material, or a combination of dielectric and magnetic materials. Specific examples of dielectric materials include resin, glass, glass ceramics, LTCC (Low Temperature Co-Fired Ceramics), alumina, and the like. Specific examples of a combination of dielectric and magnetic materials include hexagonal crystal system ferrites, spinel ferrites (Mn—Zn ferrites, Ni—Zn ferrites, etc.), garnet ferrites, permalloy, Sendust (registered trademark), and other materials including a transition metal element such as Fe, Ni, or Co, and a metal or an oxide including a rare earth element such as Sm or Nd, for example.
The substrate 80 includes the ground plane 70, and the feeding point 11 that uses the ground plane 70 as a ground reference. Note that although
The substrate 80 includes a transmission line having a strip conductor 82 that is connected to the feeding point 11. The strip conductor 82 may be a signal line formed on the surface of the substrate 80 such that the substrate 80 may be interposed between the strip conductor 82 and the ground plane 70, for example.
The radiating elements 30 and 40 are positioned apart from the feeding element 20 and the control elements 50 and 60. For example, as illustrated in
The feeding element 20 and the radiating elements 30 and 40 may be spaced apart from each other by a distance that enables electromagnetic field coupling between the feeding element 20 and the radiating elements 30 and 40, for example. By coupling the feeding element 20 and the radiating element 30 through electromagnetic field coupling, noncontact feeding of the radiating element 30 at the feeding portion 35 via the feeding element 20 may be realized. By feeding the radiating element 30 in this manner, the radiating element 30 may function as a radiating conductor of the antenna 1. In the case where the radiating element 30 is a linear conductor connecting two points as illustrated in
Electromagnetic field coupling refers to coupling that utilizes a resonance phenomenon of an electromagnetic field as disclosed, for example, in the following non-patent literature: A. Kurs et. al., “Wireless Power Transfer via Strongly Coupled Magnetic Resonances,” Science Express, Vol. 317, No. 5834, pp. 83-86, July 2007. Electromagnetic field coupling, also referred to as “electromagnetic field resonance coupling” or “electromagnetic field resonant coupling,” is a technique in which resonators that resonate at the same frequency are brought close to each other, one of the resonators is caused to resonate to generate a near field (non-radiation field area) between the resonators, and energy is transmitted to another one of the resonators via coupling at the near field. Also, electromagnetic field coupling refers to coupling via an electric field and a magnetic field at a high frequency excluding electrostatic capacitive coupling and electromagnetic induction coupling. Here, “excluding electrostatic capacitive coupling and electromagnetic induction coupling” does not necessarily mean electrostatic capacitive coupling and electromagnetic induction coupling are completely eliminated, but indicates that their influence is negligible. A medium between the feeding element 20 and the radiating elements 30 and 40 may be air or a dielectric material such as glass or resin. It is preferable to not place a conductor material such as a ground plane or a display between the feeding element 20 and the radiating elements 30 and 40.
By coupling the feeding element 20 and the radiating elements 30 and 40 through electromagnetic field coupling, a durable structure that is resistant to impact may be obtained. That is, by utilizing electromagnetic field coupling, feeding of the radiating elements 30 and 40 may be implemented using the feeding element 20 without requiring physical contact between the feeding element 20 and the radiating elements 30 and 40, and thus, a durable structure that is resistant to impact may be obtained as compared to a contact type feeding mechanism that requires physical contact between the feeding element and the radiating element.
Also, as compared with feeding using electrostatic capacitive coupling, when feeding using electromagnetic field coupling is implemented, the total efficiency (antenna gain) of the radiating elements 30 and 40 may be less likely to decrease even if the distance between the feeding element 20 and the radiating elements 30 and 40 (coupling distance) is increased. Note that the total efficiency is calculated based on the radiation efficiency×return loss of the antenna, and the total efficiency is defined as the efficiency of the antenna with respect to the input power. Therefore, by coupling the feeding element 20 and the radiating elements 30 and 40 through electromagnetic field coupling, a greater degree of freedom for determining the arrangement positions of the feeding element 20 and the radiating elements 30 and 40 may be obtained and position robustness may be increased. Note that when high position robustness is achieved, this means that the total efficiency of the radiating elements 30 and 40 may be less likely to be affected even when variations occur in the arrangement positions of the feeding element 20 and the radiating elements 30 and 40. Also, by obtaining a greater degree of freedom for determining the arrangement positions of the feeding element 20 and the radiating elements 30 and 40, the space required for installing the antenna 1 may be easily reduced. Also, by feeding the radiating elements 30 and 40 through electromagnetic field coupling as opposed to feeding through electrostatic capacitive coupling, for example, feeding of the radiating elements 30 and 40 may be performed via the feeding element 20 without the use of other components such as a capacitance plate, and as such, feeding may be realized through a simple structure.
Also, in
The impedance of the radiating element 30, when in dipole mode, becomes higher as the distance from the central portion 32 toward the end portion 33 or the end portion 34 of radiating element 30 increases. In the case of coupling at high impedance by electromagnetic field coupling, even when slight variations occur in the impedance between the feeding element 20 and the radiating element 30, its impact on impedance matching may be relatively small as long as the feeding element 20 and the radiating element 30 are coupled at a sufficiently high impedance of at least a certain level. Thus, to facilitate matching, the feeding portion 35 of the radiating element 30 is preferably positioned at a high impedance portion of the radiating element 30.
For example, to facilitate impedance matching of the antenna 1, the feeding portion 35 may be positioned at a region spaced apart from the region having the lowest impedance at the resonant frequency of the fundamental mode of the radiating element 30 (the central portion 32 in the present case) by a distance greater than or equal to ⅛ of the total length of the radiating element 30 (preferably greater than or equal to ⅙ of the total length, and more preferably greater than or equal to ¼ of the total length). In
The feeding portion 45 corresponds to a part of the radiating element 40 at which feeding of the radiating element 40 is implemented. Note that because features of the feeding portion 45 may be substantially identical to those of the feeding portion 35, detailed descriptions thereof will be omitted. Note that in the case where the fundamental mode of resonance of the radiating elements corresponds to the loop mode, the feeding portion may be positioned at a region spaced apart from the region having the highest impedance at the resonant frequency of the fundamental mode of the radiating element by a distance less than or equal to 3/16 of the inner circumference of the loop (preferably less than or equal to ⅛ of the inner circumference, and more preferably less than or equal to 1/16 of the inner circumference).
Also, assuming Le20 denotes the electrical length that imparts the fundamental mode of resonance to the feeding element 20, Le30 and Le40 respectively denote the electrical lengths that impart the fundamental mode of resonance to the radiating elements 30 and 40, and λ denotes a wavelength on the feeding element 20 or the radiating element 30 or 40 at a resonant frequency f1 of the fundamental mode of the radiating elements 30 and 40, Le20 is preferably less than or equal to (⅜)λ, Le30 and Le40 are preferably greater than or equal to (⅜)λ and less than or equal to (⅝)λ in the case where the fundamental mode of resonance of the radiating elements 30 and 40 corresponds to the dipole mode, and Le30 and Le40 are preferably greater than or equal to (⅞)λ and less than or equal to ( 9/8)λ in the case where the fundamental mode of resonance of the radiating elements 30 and 40 corresponds to the loop mode.
The electrical length Le20 is preferably less than or equal to (⅜)λ. Also, in order to allow a greater degree of freedom in the configuration including the presence/absence of the ground plane 70, the electrical length Le20 may preferably be greater than or equal to (⅛)λ and less than or equal to (⅜)λ, and more preferably greater than or equal to ( 3/16)λ and less than or equal to ( 5/16)λ. By arranging the electrical length Le20 to be within the above ranges, resonance of the feeding element 20 may occur at the design frequency (resonant frequency f1) of the radiating elements 30 and 40, and in this way, the feeding element 20 and the radiating elements 30 and 40 may resonate without depending on the ground plane 70 of the antenna 1 and desirable electromagnetic field coupling may be achieved.
Also, when the ground plane 70 is formed such that the outer edge 71 extends along the radiating elements 30 and 40, a resonance current (standing wave current distribution) may be formed on the feeding element 20 and the ground plane 70 as a result of an interaction between the feeding element 20 and the outer edge 71, and the feeding element 20 may resonate and be coupled with the radiating elements 30 and 40 through electromagnetic field coupling. For this reason, there is no specific lower limit for the electrical length Le20 of the feeding element 20 as long as the feeding element 20 has a physical length that is sufficient to be coupled to the radiating elements 30 and 40 by electromagnetic field coupling.
Note that when electromagnetic field coupling is achieved this means that impedance matching is achieved. Also, in this case, the electrical length Le20 of the feeding element 20 does not have to be designed to a suitable electrical length according to the resonant frequency of the radiating elements 30 and 40, and the feeding element 20 may be freely designed as a radiating conductor. In this way, the antenna 1 may be easily designed to support multiple frequencies. Note that the sum of the length of the outer edge 71 of the ground plane 70 extending along the radiating elements 30 and 40 and the electrical length of the feeding element 20 is preferably greater than or equal to (¼)λ of the design frequency (resonant frequency f1).
When the feeding element 20 does not include a component such as a matching circuit, a physical length L20 of the feeding element 20 (L14 in the case of
In the case where the fundamental mode of resonance of the radiating elements 30 and 40 corresponds to the dipole mode (i.e., when the radiating elements 30 and 40 are linear conductors having open ends), Le30 and Le 40 are preferably greater than or equal to (⅜)λ and less than or equal to (⅝)λ, more preferably greater than or equal to ( 7/16)λ and less than or equal to ( 9/16)λ, and more preferably greater than or equal to ( 15/32)λ and less than or equal to ( 17/32)λ. When a higher-order mode is taken into account, Le30 and Le40 are preferably greater than or equal to (⅜)λm and less than or equal to (⅝)λm, more preferably greater than or equal to ( 7/16)λm and less than or equal to ( 9/16)λm, and more preferably greater than or equal to ( 15/32)λm and less than or equal to ( 17/32)λm. Here, m denotes a mode number of a higher-order mode and is represented by a natural number. The value of m is preferably an integer between 1 through 5, and more preferably an integer between 1 through 3. In this case, m=1 represents the fundamental mode. When Le30 and Le40 are within the above ranges, the radiating elements 30 and 40 may function sufficiently as radiating conductors, and the efficiency of the antenna 1 may be desirably high.
Also, in the case where the fundamental mode of resonance of the radiating elements 30 and 40 corresponds to the loop mode (i.e., when the radiating elements 30 and 40 are looped conductors), Le30 and Le 40 are preferably greater than or equal to (⅞)λ and less than or equal to ( 9/8)λ, more preferably greater than or equal to ( 15/16)λ and less than or equal to ( 17/16)λ, and more preferably greater than or equal to ( 31/32)λ and less than or equal to ( 33/32)λ. When a higher-order mode is taken into account, Le30 and Le40 are preferably greater than or equal to (⅞)λm and less than or equal to ( 9/8)λm, more preferably greater than or equal to ( 15/16)λm and less than or equal to ( 17/16)λm, and more preferably greater than or equal to ( 31/32)λm and less than or equal to ( 33/32)λm.
Note that physical lengths L30 and L40 of the radiating elements 30 and 40 (corresponding to length L15 in the case of
Also, in the case where the interaction between the feeding element 20 and the outer edge 71 of the ground plane 70 is utilized as illustrated in
The physical length L20 of the feeding element 20 when utilizing the radiating function of the feeding element 20, assuming the feeding element 20 does not include a component such as a matching circuit, is determined by λg3=λ1k1, where λ1 denotes the radio wave wavelength in vacuum at the resonant frequency f2 of the feeding element 20, and k1 denotes a shortening coefficient of a wavelength shortening effect in an actual environment. Here, k1 is calculated based on, for example, a relative permittivity and a relative permeability such as an effective relative permittivity (∈r1) and an effective relative permeability (μr1) of a medium (environment) such as a dielectric substrate at which the feeding element 20 is arranged, a thickness of the medium (environment), and the resonant frequency. That is, L20 is greater than or equal to (⅛)λg3 and less than or equal to (⅜)λg3, and preferably greater than or equal to ( 3/16)λg3 and less than or equal to ( 5/16)λg3. The physical length L20 of the feeding element 20 is a physical length that gives Le20. In an ideal case where no other factor is considered, the physical length L20 is equal to Le20. When the feeding element 20 includes a matching circuit, for example, L20 is preferably greater than zero and less than or equal to Le20. By using a matching circuit such as an inductor, L20 can be reduced (i.e., the size of the feeding element 20 can be reduced).
Also, assuming λ0 denotes the radio wave wavelength in vacuum at the resonant frequency f1 of the fundamental mode of the radiating elements 30 and 40, a shortest distance x between the feeding element 20 and the radiating elements 30 and 40 is preferably less than or equal to 0.2×λ0 (more preferably less than or equal to 0.1×λ0, and more preferably less than or equal to 0.05×λ0). By arranging the feeding element 20 and the radiating elements 30 and 40 to be spaced apart by the shortest distance x as described above, the total efficiency (antenna gain) of the radiating elements 30 and 40 may be improved.
Note that the shortest distance x refers to the linear distance between a portion of the feeding element 20 and portions of the radiating elements 30 and 40 that are closest to each other, is the linear distance between portions that are closest. Also, the orientations of the feeding element 20 and the radiating elements 30 and 40 are not particularly limited as long as the feeding element 20 and the radiating elements 30 and 40 are coupled through electromagnetic field coupling. That is, the feeding element 20 and the radiating elements 30 and 40 may or may not be intersecting one another as viewed from a given direction, and their intersection angles may be set to any arbitrary angle.
Also, in the dipole mode, a distance over which the feeding element 20 and the radiating elements 30 and 40 run parallel to each other spaced the shortest distance x apart is preferably less than or equal to ⅜ of the length of the radiating elements 30 and 40. More preferably, the distance is less than or equal to ¼ of the length of the radiating elements, and more preferably less than or equal to ⅛ of the length of the radiating elements. In the loop mode, the distance is preferably less than or equal to 3/16 of the inner circumference of the loop formed by the radiating elements, more preferably less than or equal to ⅛ of the inner circumference, and more preferably less than or equal to 1/16 of the inner circumference. Also, in a monopole mode (described below), the distance is preferably less than or equal to ¾ of the length of radiating elements 160 and 170, more preferably ½ of the length of the radiating element, and more preferably ¼ of the length of the radiating elements. The position where the feeding element 20 and the radiating elements 30 and 40 are spaced apart by the shortest distance x corresponds to where coupling between the feeding element 20 and the radiating elements 30 and 40 is strong, and when the distance over which the feeding element 20 and the radiating elements 30 and 40 run parallel to each other spaced the shortest distance x apart is too long, strong coupling may occur at both a high impedance portion and a low impedance portion of the radiating elements 30 and 40, and as such, impedance matching may become difficult. Thus, to obtain strong coupling only at a region where there is little variation in the impedance of the radiating elements 30 and 40, the distance over which the feeding element 20 and the radiating elements 30 and 40 run parallel to each other spaced the shortest distance x apart is preferably arranged to be relatively short, and in this way, advantageous effects may be achieved in terms of impedance matching.
In
In
On the other hand, the feeding element 20 is a linear feeding conductor that is capable of feeding the radiating elements 30 and 40. Also, the feeding element 20 may be fed by the feeding point 11 and thereby function as an antenna operating in monopole mode (e.g., λ/4 monopole antenna).
The radiating element 30 has the feeding portion 35 positioned toward the end portion 33 with respect to the central portion 32, and in this way, high impedance electromagnetic field coupling between the radiating element 30 and the feeding element 20 may be realized. Similarly, the radiating element 40 has the feeding portion 45 positioned toward the end portion 43 with respect to a central portion 42, and in this way, high impedance electromagnetic field coupling between the radiating element 40 and the feeding element 20 may be realized.
In the state where the feeding element 20 is coupled to both the radiating elements 30 and 40 through high impedance electromagnetic field coupling, the directivity of the antenna 1 may be linearly symmetrical with respect to a YZ plane passing through the feeding element 20, provided the environment is uniform.
The impedance control unit 120 includes an impedance variable unit that interconnects the feeding element 20 and the control element 50, and an impedance variable unit that interconnects the feeding element 20 and the control element 60. The impedance variable unit is for varying the impedance between the feeding element and the control element from low impedance to high impedance or from high impedance to low impedance. For example, an impedance adjusting unit that is capable of adjusting the impedance may be used as the impedance variable unit.
The impedance variable unit may be, for example, a switch that is capable of selectively switching the impedance between the feeding element and the control element to either low impedance or high impedance. For example, when the switch is turned on, the impedance between the feeding element and the control element may be switched to low impedance, and when the switch is turned off, the impedance between the feeding element and the control element may be switched to high impedance. Alternatively, the impedance variable unit may be configured to continuously change the impedance between the feeding element and the control element in an increasing direction or a decreasing direction, for example.
The control element 50 may be arranged such that when the impedance of the impedance variable unit between the control element 50 and the feeding element 20 at the resonant frequency of the radiating element 30 is decreased, the electromagnetic field coupling between the feeding element 20 and the radiating element 30 is weakened and the function of the radiating element 30 as a radiating conductor is degraded, for example. The control element 50 may be arranged such that when the impedance variable unit between the control element 50 and the feeding element 20 is set to low impedance, the electromagnetic field coupling between the feeding element 20 and the radiating element 30 may be weakened such that the radiating element 30 loses its function as a radiating conductor, for example. In
The control element 60 may be arranged in a manner similar to the control element 50. For example, the control element 60 may be arranged such that when the impedance of the impedance variable unit between the control element 60 and the feeding element 20 at the resonant frequency of the radiating element 40 is decreased, the electromagnetic field coupling between the feeding element 20 and the radiating element 40 is weakened and the function of the radiating element 40 as a radiating conductor is degraded. For example, the control element 60 may be arranged such that when the impedance variable unit between the control element 60 and the feeding element 20 is set to low impedance, the electromagnetic field coupling between the feeding element 20 and the radiating element 40 is weakened such that the radiating element 40 loses its function as a radiating conductor, for example. In
In the antenna 1 having the feeding element 20 coupled to a high impedance portion of the radiating element 30 (feeding portion 35) through electromagnetic field coupling, the impedance control unit 120 establishes low impedance connection between the feeding element 20 and the control element 50. By establishing low impedance connection between the feeding element 20 and the control element 50 via the impedance control unit 120, the electromagnetic field coupling between the feeding element 20 and the radiating element 30 is weakened. That is, because the end portion 51 corresponding to a high impedance portion of the control element 50 and the central portion 32 corresponding to a low impedance portion of the radiating element 30 at the resonant frequency of the radiating element 30 are arranged close to each other, by establishing low impedance connection between the feeding element 20 and the control element 50, the electromagnetic field coupling between the feeding element 20 and the radiating element 30 may be weakened. Similarly, in the antenna 1 having the feeding element 20 coupled to a high impedance portion of the radiating element 40 (feeding portion 45) through electromagnetic field coupling, the impedance control unit 120 establishes low impedance connection between the feeding element 20 and the control element 60. By establishing low impedance connection between the feeding element 20 and the control element 60 via the impedance control unit 120, the electromagnetic field coupling between the feeding element 20 and the radiating element 40 may be weakened.
Thus, when the feeding element 20 is coupled to both the radiating element 30 and the radiating element 40 through electromagnetic field coupling, the electromagnetic field coupling between the feeding element 20 and the radiating element 30 may be weakened by establishing low impedance connection between the feeding element 20 and the control element 50. In this way, the antenna gain of the radiating element 30 may become smaller than the antenna gain of the radiating element 40 and the radiation from the radiating element 40 may become dominant such that the directivity of the antenna 1 may be altered and controlled. Similarly, when the feeding element 20 is coupled to both the radiating element 30 and the radiating element 40 through electromagnetic field coupling, by establishing low impedance connection between the feeding element 20 and the control element 60, the electromagnetic field coupling between the feeding element 20 and the radiating element 40 may be weakened. In this way, the antenna gain of the radiating element 40 may become smaller than the antenna gain of the radiating element 30 and the radiation from the radiating element 30 may become dominant such that the directivity of the antenna 1 may be altered and controlled.
Also, by weakening the electromagnetic field coupling between the radiating element 30 and the feeding element 20 and the electromagnetic field coupling between the radiating element 40 and the feeding element 20, the antenna gain of both the radiating element 30 and the radiating element 40 may be reduced. In this way, the SAR (Specific Absorption Rate) of the antenna 1 and a wireless device equipped with the antenna 1 may be reduced, and their impact on the human body may be reduced, for example.
Thus, by arranging the antenna 1 to have the above-described configuration, the directivity of the antenna 1 may be switched and controlled without having the feeding element 20 arranged in contact with the radiating element 30 or the radiating element 40.
Note that in
The impedance control unit 120 may include an impedance adjusting unit 121 that is configured to lower the impedance between the feeding element 20 and the control element 50 to thereby degrade the function of the radiating element 30 as a radiating conductor, for example. The impedance adjusting unit 121 may be configured to lower the impedance between the feeding element 20 and the control element 50 close to zero to thereby weaken the electromagnetic field coupling between the radiating element 30 and the feeding element 20, for example. Note that the impedance adjusting unit 121 is an example of the impedance variable unit that is capable of increasing or decreasing the impedance between the feeding element 20 and the control element 50, and may be implemented by an element such as a variable capacitance diode or a circuit including such an element, for example. The impedance adjusting unit 121 may be capable of gradually changing (decreasing or increasing) the impedance between the feeding element 20 and the control element 50 and thereby continuously change the directivity of the antenna 1, for example. Note that the impedance control unit 120 may also be configured to switch and control the directivity of the antenna 1 by turning on/off a switch element such as a transistor included in the impedance adjusting unit 121.
By controlling the impedance between the feeding element 20 and the control element 50 to low impedance (e.g., ON), the impedance adjusting unit 121 may increase the RF current flowing between the feeding element 20 and the control element 50. In this way, the electromagnetic field coupling between the radiating element 30 and the feeding element 20 that is connected to the control element 50 with low impedance may be weakened, and the function of the radiating element 30 as a radiating conductor may be degraded. Conversely, by controlling the impedance between the feeding element 20 and the control element 50 to high impedance (e.g., OFF), the impedance adjusting unit 121 may reduce or stop the RF current flowing between the feeding element 20 and the control element 50. In this way, the radiating elements 30 may be coupled to the feeding element 20 through electromagnetic field coupling.
Similarly, the impedance control unit 120 may include an impedance adjusting unit 122 that is configured to lower the impedance between the feeding element 20 and the control element 60 to thereby degrade the function of the radiating element 40 as a radiating conductor, for example. The impedance adjusting unit 122 may be configured to lower the impedance between the feeding element 20 and the control element 60 close to zero to thereby weaken the electromagnetic field coupling between the radiating element 40 and the feeding element 20, for example. Note that features and functions of the impedance adjusting unit 122 may be substantially identical to those of the impedance adjusting unit 121, and as such, detailed descriptions thereof will be omitted.
The capacitor 147 and the inductor 148 are connected in series, one end of the capacitor 147 is connected to the end portion 21 of the feeding element 20, and one end of the inductor 148 is connected to the ground plane 70. One end of the control element 50 is connected to an intermediate connection point between the capacitor 147 and the inductor 148 via the variable capacitance diode 145, and one end of the control element 60 is connected to the intermediate connection point between the capacitor 147 and the inductor 148 via the variable capacitance diode 146. The inductor 143 and the DC voltage source 141 are connected in series, one end of the inductor 143 is connected to an intermediate connection point between the variable capacitance diode 145 and the control element 50, and one end of the DC voltage source 141 is connected to the ground plane 70. The inductor 144 and the DC voltage source 142 are connected in series, one end of the inductor 144 is connected to an intermediate connection point between the variable capacitance diode 146 and the control element 60, and one end of the DC voltage source 142 is connected to the ground plane 70.
When the DC voltage source 141 increases its DC voltage output, the capacitance of the variable capacitance diode 145 decreases, and as a result, the impedance between the feeding element 20 and the control element 50 increases such that the RF current flowing through the control element 50 may be reduced or stopped. In this way, the connection between the feeding element 20 and the control element 50 may be weakened or disconnected such that the radiating element 30 that is coupled to the feeding element 20 through electromagnetic field coupling may be able to implement its function as a radiating conductor.
Conversely, when the DC voltage source 141 decreases or stops its DC voltage output, the capacitance of the variable capacitance diode 145 increases, and as a result, the impedance between the feeding element 20 and the control element 50 decreases such that the RF current flowing through the control element 50 may be increased. In this way, the connection between the feeding element 20 and the control element 50 may be strengthened such that the function of the radiating element 30, which is electromagnetically coupled to the feeding element 20, as a radiating conductor may be suppressed or blocked, for example.
Similarly, when the DC voltage source 142 increases its DC voltage output, the capacitance of the variable capacitance diode 146 decreases, and as a result, the impedance between the feeding element 20 and the control element 60 increases, such that the RF current flowing through the control element 60 may be reduced or stopped. In this way, the connection between the feeding element 20 and the control element 60 may be weakened or disconnected such that the radiating element 40 that is coupled to the feeding element 20 through electromagnetic field coupling may implement its function as a radiating conductor.
Conversely, when the DC voltage source 142 decreases or stops its DC voltage output, the capacitance of the variable capacitance diode 146 increases, and as a result, the impedance between the feeding element 20 and the control element 60 decreases such that the RF current flowing through the control element 60 may be increased. In this way, the connection between the feeding element 20 and the control element 60 may be strengthened such that the function of the radiating element 40, which is electromagnetically coupled to the feeding element 20, as a radiating conductor may be suppressed or blocked, for example.
By using the impedance control unit 120 as illustrated in
The antenna 1 has a symmetrical configuration with respect to the YZ plane passing through the feeding point 11. Thus, in a case where the impedance between the feeding element 20 and the control element 50 is low, and the impedance between the feeding element 20 and the control element 60 is high, as opposed to the case of
In
By using the matching circuit 90, even when the resonant frequency of the fundamental mode of the radiating element 30 or the radiating element 40 changes as a result of a change in the coupling state between the radiating element 30 and the feeding element 20 or the coupling state between the radiating element 40 and the feeding element 20, the matching circuit 90 may correct such change in the resonant frequency, for example.
Note that
If the matching circuit 90 is not operated when the impedance adjusting unit 122 is switched from ON to OFF, the resonant frequency of the fundamental mode of the radiating element 30 (1.485 GHz in the present example) may deviate in some cases (e.g., change from “c” to “a” in
Note that upon obtaining the S11 characteristic measurements, the dimensions L11-L16 of the configuration illustrated in
L11: 60
L12: 30
L13: 130
L14: 10.5
L15: 58
L16: 30
Also, the line widths of the feeding element 20, the radiating elements 30 and 40, the control elements 50 and 60 were set to 1 mm.
Also, upon obtaining the S11 characteristic measurements, the dimensions of the configuration illustrated in
<Antenna Device 201>
The antenna 2 of the antenna device 201 may have a configuration that is substantially identical to the configuration of the antenna 1, and is arranged on the opposite side of the antenna 1 with respect to the ground plane 70. The antenna 2 includes a feeding element 22, a radiating element 36, a radiating element 46, a control element 52, a control element 62, an impedance control unit 125, and a matching circuit 91.
The feeding element 22 is a conductor that uses the ground plane 70 as a ground reference and is connected to a feeding point 12. The feeding point 12 may be arranged at a central portion of an outer edge 72 of the ground plane 70, for example. The outer edge 72 is located at the opposite side of the outer edge 71 with respect to the central portion of the ground plane 70.
The radiating element 36 and the radiating element 46 are both coupled to the feeding element 22 through electromagnetic field coupling. The control element 52 is spaced apart from the radiating element 36 in a direction parallel to the Z-axis, and the control element 62 is spaced apart from the radiating element 46 in a direction parallel to the Z-axis.
The impedance control unit 125 is an example of a control unit that controls an impedance variable unit to establish low impedance connection between the feeding element 22 and the control element 52, or between the feeding element 22 and the control element 62. The impedance control unit 125 may include an impedance adjusting unit 123 that may be substantially identical to the impedance adjusting unit 121 described above. For example, the impedance adjusting unit 123 may be configured to lower the impedance between the feeding element 22 and the control element 52 to thereby weaken the electromagnetic field coupling between the radiating element 36 and the feeding element 22. Similarly, the impedance control unit 125 may include an impedance adjusting unit 124 that may be substantially identical to the impedance adjusting unit 122 described above. For example, the impedance adjusting unit 124 may be configured to lower the impedance between the feeding element 22 and the control element 62 to thereby weaken the electromagnetic field coupling between the radiating element 46 and the feeding element 22.
The matching circuit 91 may be similar to the matching circuit 90 as described above. That is, the matching circuit 91 may operate in conjunction with the operation of the impedance control unit 125 to adjust the resonant frequency of the fundamental mode of the radiating element 36 and the radiating element 46.
By including the antennas 1 and 2, the antenna device 201 may function as a MIMO (Multiple Input Multiple Output) antenna. Also, the antenna device 201 may be capable of switching and controlling the directivity of each of the antennas 1 and 2 while maintaining the correlation coefficient between the antenna 1 and the antenna 2 at a desirably low value regardless of the impedances set up by the impedance adjusting units 121, 122, 123, and 124.
<Antenna 3>
The antenna 3 includes a ground plane 70, a plate conductor 150, a feeding element 20, a radiating element 160, a radiating element 170, a control element 50, a control element 60, an impedance control unit 120, and optionally, a matching circuit 90. Note that the feeding element 20, the control element 50, the control element 60, the impedance control unit 120, and the matching circuit 90 may be substantially identical to those described above with reference to
The ground plane 70 is a planar ground pattern having at least one side as an outer edge. In
The plate conductor 150 is a flat conductor arranged parallel to the ground plane 70 and spaced apart from the ground plane 70 in a direction parallel to the Z-axis. In
By arranging the plate conductor 150 to have at least one outer edge extending along at least one outer edge of the ground plane 70, resonance between the plate conductor 150 and the ground plane 70 may be facilitated, and the number of resonance of the antenna 3 may be increased. In
The plate conductor 150 includes a portion spaced apart from the ground plane 70 in a direction parallel to the Z-axis and facing the ground plane 70. In
The feeding element 20 is a conductor that is spaced apart from the radiating element 160 and the radiating element 170 by a predetermined distance. The feeding element 20 may be spaced apart from the radiating element 160 and the radiating element 170 by a gap having a direction component parallel to the Z-axis.
In
The feeding element 20 is a conductor that is capable of performing noncontact feeding of the radiating element 160 via the feeding portion 165 of the radiating element 160, performing noncontact feeding of the radiating element 170 via the feeding portion 175 of the radiating element 170.
In plan view from a direction normal to the ground plane 70, the feeding element 20 extends from the feeding point 11 to the end portion 21 in a direction toward a gap 131 between one end portion 163 of the radiating element 160 and one end portion 173 of the radiating element 170. The feeding element 20 includes the end portion 21 that is spaced apart from the end portion 163 of the radiating element 160 and the end portion 173 of the radiating element 170 by a predetermined distance, and the end portion 21 is positioned in the vicinity of the gap 131.
The radiating element 160 is a linear radiating conductor that is connected to the plate conductor 150 and protrudes from the outer edge 151 of the plate conductor 150 in an opposite direction from the plate conductor 150. The radiating element 160 is arranged such that at least a portion of the radiating element 160 does not overlap with the ground plane in plan view from a direction parallel the Z-axis. The radiating element 160 includes the end portion 163 and another end portion 164, and is arranged into an L-shape that extends from one end portion 164 to the other end portion 163 via a bent portion 167. The end portion 164 is a root portion that is connected to a portion of the plate conductor 150 in the vicinity of one end portion 155 of the outer edge 151 of the plate conductor 150, and the end portion 163 is an open end that is not connected to another conductor.
The radiating element 160 may include a linear radiating conductor portion that is arranged along the outer edge 71 of the ground plane 70, for example. The radiating element 160 may include a conductor portion 161 that is arranged opposite the outer edge 71 of the ground plane 70 and extends in a direction parallel to the outer edge 71 while being spaced apart from the outer edge 71 by a predetermined shortest distance, for example. Note that a direction parallel to the outer edge 71 corresponds to a direction parallel to the X axis in
Note that although
The radiating element 170 may have the same or similar configuration as the radiating element 160, and as such, descriptions thereof are simplified. The radiating element 170 is an antenna conductor that includes one end portion 174 and another end portion 173, and is arranged into an L-shape extending from the end portion 174 to the end portion 173 via a bent portion 177. The end portion 174 is a root portion that is connected to a portion of the plate conductor 150 in the vicinity of an end portion 156 of the outer edge 151 of the plate conductor 150, and the end portion 173 is an open end that is not connected to another conductor. The radiating element 170 may include a conductor portion 171 that is arranged opposite the outer edge 71 of the ground plane 70 and extends in a direction parallel to the outer edge 71 while being spaced apart from the outer edge 71 by a predetermined shortest distance, for example.
The radiating element 170 and the radiating element 160 are conductors extending in different directions from each other, in directions toward the feeding element 20. Note that although
Also, although
The feeding element 20 and the radiating element 160 may be spaced apart from each other by a certain distance so as to enable high frequency coupling between the radiating element 160 and the feeding element 20. Noncontact feeding of the radiating element 160 may be implemented via the feeding element 20. By feeding the radiating element 160 in this manner, the radiating element 160 may function as a radiating conductor of an antenna. As illustrated in
The radiating element 170 may have the same or similar configuration as the radiating element 160, and as such descriptions thereof are simplified. The feeding element 20 and the radiating element 170 may be spaced apart by a certain distance so as to enable electromagnetic field coupling between these elements. Noncontact feeding of the radiating element 170 may be implemented via the feeding element 20. By feeding the radiating element 170 in this manner, the radiating element 170 may function as a radiating conductor of an antenna.
Also, assuming Le160 and Le170 denote the electrical lengths that impart the fundamental mode of resonance to the radiating elements 160 and 170, and λ denotes the wavelength on the radiating elements 160 and 170 at the resonant frequency f1 of the fundamental mode of the radiating elements 160 and 170, Le160 and Le170 are greater than or equal to (⅛)λ and less than or equal to (⅜)λ.
Also, in a case where the fundamental mode of resonance of the radiating elements corresponds to the monopole mode (i.e., the radiating elements are connected to the outer edge of the plate conductor and have open ends), Le160 and Le170 are preferably greater than or equal to (⅛)λ and less than or equal to (⅜)λ, more preferably greater than or equal to ( 3/16)λ and less than or equal to ( 5/16)λ, and more preferably greater than or equal to ( 7/32)λ and less than or equal to ( 9/32)λ. By arranging Le160 and Le170 to be within the above ranges, the radiating elements 160 and 170 may adequately function as radiating conductors, and the antenna 3 may achieve desirably high efficiency, for example.
Also, assuming L160 and L170 denote the physical lengths of the radiating elements 160 and 170 (corresponding to L18+L19 in
In
In the monopole mode, the impedance of the radiating elements 160 and 170 increases from the end portions 164 and 174 toward the end portions 163 and 173 of the radiating elements 160 and 170. In the case of implementing high impedance coupling between the feeding element 20 and the radiating elements 160 and 170 through electromagnetic field coupling, even when slight variations occur in the impedance between the feeding element 20 and the radiating elements 160 and 170, their impact on impedance matching may be relatively small as long as the feeding element 20 and the radiating elements 160 and 170 are coupled at a sufficiently high impedance of at least a certain level. Thus, to facilitate matching, the feeding portions 165 and 175 of the radiating elements 160 and 170 are preferably positioned at high impedance portions of the radiating elements 160 and 170.
For example, to facilitate impedance matching of the antenna 3, the feeding portions 165 and 175 may be positioned at a region spaced apart from the region having the lowest impedance at the resonant frequency of the fundamental mode of the radiating elements 160 and 170 (end portions 164 and 174 in the present example) by a distance greater than equal to ¼ of the total length of the radiating elements 160 and 170 (preferably greater than or equal to ⅓ of the total length, and more preferably greater than or equal to ½ of the total length). Further, the feeding portions 165 and 175 are preferably arranged at positions toward the end portions 163 and 173 from the central portions 162 and 172. In
In the antenna 3 having the above-described configuration, even when the plate conductor 150 having a relatively large area is arranged, because noncontact feeding of the radiating elements 160 and 170 by the feeding element 20 is implemented, restrictions on the configurations and layout of the radiating elements 160 and 170 and/or the feeding element 20 may be reduced. That is, as long as the feeding element 20 and the radiating elements 160 and 170 are spaced apart by a suitable distance that enables noncontact feeding of the radiating elements 160 and 170, the positional relationship between the feeding element 20 and the radiating elements 160 and 170 may be freely designed and functions of the antenna 3 may be implemented with relative ease.
The ground plane 70 and the plate conductor 150 may be DC coupled via a connection conductor 84, for example. Note that any number of connection conductors 84 may be provided. In a case where a heating element 83 is arranged on the substrate 80, heat emitted by the heating element 83 may be transferred to the plate conductor 150 via the substrate 80 and the connection conductor 84.
The plate conductor 150 is capable of functioning as a heat sink that dissipates heat. The plate conductor 150 may release the heat generated by the heating element 83 mounted on the substrate 80, or release heat generated by a heating element (not shown) mounted on the substrate 110, for example.
Specific examples of the connection conductor 84 include a metal plate and wiring such as a via or a wire. Specific examples of the heating element 83 include circuit components mounted on the substrate 80 (transistor, IC, etc.).
In
The radiating element 160 has the feeding portion 165 arranged at a position toward the end portion 163 from the central portion 162, and in this way, the feeding element 20 may be coupled to a high impedance portion of the radiating element 160 through electromagnetic field coupling. Likewise, the radiating elements 170 has the feeding portion 175 arranged at a position toward the end portion 173 from the central portion 172, and in this way, the feeding element 20 may be coupled to a high impedance portion of the radiating element 170 through electromagnetic filed coupling.
In the case where the feeding element 20 is electromagnetically coupled to both the radiating element 160 and the radiating element 170 at high impedance portions and impedance matching with the radiating elements 160 and the radiating element 170 are achieved, the directivity of the antenna 3 may be linearly symmetrical with respect to the YZ plane that passes through the feeding element 20, provided the surrounding environment is uniform.
The impedance control unit 120 is an example of a control unit that controls an impedance variable unit to connect the feeding element 20 to the control element 50 or the control element 60 and vary the impedance between the feeding element 20 and the control element 50 or the impedance between the feeding element 20 and the control element 60. Note that the impedance control unit 120 of
The antenna 3 has a symmetrical configuration with respect to an YZ plane that passes through the feeding point 11. Thus, in a case where the impedance between the feeding element 20 and the control element 50 is low, and the impedance between the feeding element 20 and the control element 60 is high, as opposed to the case of
In
By using the matching circuit 90, even when the resonant frequency of the fundamental mode of the radiating element 160 or the radiating element 170 is changed as a result of a change in the coupling state between the radiating element 160 and the feeding element 20 or the coupling state between the radiating element 170 and the feeding element 20, the matching circuit 90 may be able to correct such a change in the resonant frequency, for example.
In the case where the matching circuit 90 is not operated, when the impedance adjusting unit 122 is switched from ON to OFF, the resonant frequency of the fundamental mode of the radiating element 160 (1.175 GHz in the present example) may deviate in some cases (e.g., change from “f” to “d” in
Note that when measuring the S11 characteristics of the antenna 3, the dimensions of the configuration illustrated in
L11: 120
L12: 80
L13: 60
L14: 10.5
L16: 29.5
L17: 80
L18: 10.5
L19: 26.5
L22: 60
Also, the line widths of the feeding element 20, the radiating elements 160 and 170, the control elements 50 and 60 were set to 1 mm.
Also, the dimensions of the configuration illustrated in
<Antenna Device 202>
The antenna 4 may have a configuration that is substantially identical to the configuration of the antenna 3, and is arranged on the opposite side of the antenna 3 with respect to the ground plane 70. The antenna 4 includes a feeding element 22, a radiating element 166, a radiating element 176, a control element 52, a control element 62, an impedance control unit 125, and a matching circuit 91.
The radiating element 166 and the radiating element 176 are each coupled to the feeding element 22 through electromagnetic field coupling. The control element 52 is spaced apart from the radiating element 166 in a direction parallel to the Z-axis, and the control element 62 is spaced apart from the radiating element 176 in a direction parallel to the Z-axis.
By including the antennas 3 and 4, the antenna device 202 can function as a MIMO (Multiple Input Multiple Output) antenna. Also, the antenna device 202 is capable of switching and controlling the directivity of each of the antennas 3 and 4 while maintaining the correlation coefficient between the antenna 3 and the antenna 4 to a desirably low value, regardless of the impedance of the impedance adjusting units 121, 122, 123, and 124.
In
Note that the dimensions of the configurations illustrated in
<Antenna 5>
The antenna 5 corresponds to a modification of the antenna 3 that is obtained by cutting out the plate conductor 150 of the antenna illustrated in
<Antenna 6>
The antenna 6 has the same components as those of the antenna 1 of
The radiating element 30 includes a conductive portion extending along the outer edge 71, and a conductive portion extending along the outer edge 73. The radiating element 40 includes a conductive portion extending along the outer edge 71, and a conductive portion extending along the outer edge 74. The ground plane 70 includes the outer edge 73 and outer edge 74 that oppose each other.
By arranging the radiating element 30 and the radiating element 40 such that the ground plane 70 may be interposed between the conductive portion of the radiating element 30 and the conductor portion of the radiating element 40, directivity control of the antenna 6 may be facilitated. For example, by arranging the radiating element 30 to include a conductive portion that extends along the outer edge 73, and by arranging the radiating element 40 to include a conductor portion that extends along the outer edge 74 opposing the outer edge 73, the directivity control of the antenna 6 may be facilitated.
One end of the inductor 251 is connected to one end of the control element 50, and the other end of the inductor 251 is connected to the end portion 21 of the feeding element 20. A series circuit including the capacitor 253 and the inductor 243 is connected between the positive terminal of the DC voltage source 241 and a connection point between the inductor 251 and the control element 50. A series circuit including the capacitor 249 and the inductor 247 is connected to a negative terminal of the DC voltage source 241 and a connection point between the inductor 251 and the feeding element 20. The negative terminal of the DC voltage source 241 is connected to the ground plane 70. The variable capacitance diode 245 includes a cathode that is connected to a connection point between the capacitor 253 and the inductor 243, and an anode that is connected to a connection point between the capacitor 249 and the inductor 247.
One end of the inductor 252 is connected to one end of the control element 60, and the other end of the inductor 252 is connected to the end portion 21 of the feeding element 20. A series circuit including the capacitor 254 and the inductor 244 is connected to a positive terminal of the DC voltage source 242 and a connection point between the inductor 252 and the control element 60. A series circuit including the capacitor 250 and the inductor 248 is connected to the negative terminal of the DC voltage source 242 and a connection point between the inductor 252 and the feeding element 20. The negative terminal of the DC voltage source 242 is connected to the ground plane 70. The variable capacitance diode 246 includes a cathode that is connected to a connection point between the capacitor 254 and the inductor 244, and an anode that is connected to a connection point between the capacitor 250 and the inductor 248.
When the DC voltage source 241 controls the output of a DC voltage V1, adjusts the capacitance of the variable capacitance diode 245, and increases the impedance between the feeding element 20 and the control element 50, an RF current flowing through the control element 50 may be suppressed or stopped. In this way, the connection between the feeding element 20 and the control element 50 may be weakened or disconnected such that the radiating element 30 that is electromagnetically coupled to the feeding element 20 may be able to implement its function as a radiating conductor.
Conversely, when the DC voltage source 241 controls the output of the DC voltage V1, adjusts the capacitance of the variable capacitance diode 245, and decreases the impedance between the feeding element 20 and the control element 50, the RF current flowing though the control element 50 may be increased. In this way, the connection between the feeding element 20 and the control element 50 may be strengthened such that the function of the radiating element 30, which is electromagnetically coupled to the feeding element 20, as a radiating conductor may be suppressed or stopped.
Similarly, when the DC voltage source 242 controls the output of a DC voltage V2, adjusts the capacitance of the variable capacitance diode 246, an increases the impedance between the feeding element 20 and the control elements 60, the RF current flowing through the control element 60 may be suppressed or stopped. In this way, the connection between the feeding element 20 and the control element 60 may be weakened or disconnected such that the radiating element 40 that is electromagnetically coupled to the feeding element 20 may implement its function as a radiating conductor.
Conversely, when the DC voltage source 242 controls the output of the DC voltage V2, adjusts the capacitance of the variable capacitance diode 246, and decreases the impedance between the feeding element 20 and the control element 60, the RF current flowing through the control element 60 may be increased. In this way, the connection between the feeding element 20 and the control element 60 may be strengthened such that the function of the radiating element 40, which is electromagnetically coupled to the feeding element 20, as a radiating conductor may be suppressed or stopped.
By using the impedance control unit 120 as illustrated in
As illustrated in
Note that in measuring the directivity of the antenna 6 in
L11: 120
L12: 68.2
L13: 38.75
L14: 8.525
L15a: 21.475
L15b: 34.1
L16a: 23.675
L16b: 8.525
L23: 60
Also, the line widths of the feeding element 20, the radiating elements 30 and 40, and the control elements 50 and 60 were set to 1 mm.
Also, in obtaining the measurements of
Also, in obtaining the measurements of FIG. 30 the component illustrated in
<Antenna Device 203>
By including the antennas 211, 212, 213, and 214 in the antenna device 203, the antenna device 203 may function as a four-channel MIMO (Multiple Input Multiple Output) antenna. Also, even when the antennas of the antenna device 203 share the same ground plane 70, the antenna device 203 may be capable of switching and controlling the directivity of each of the antennas while maintaining the correlation coefficients between the antennas to desirably low values, regardless of the impedance of the impedance adjusting units 121 and 122 of the antennas.
The antenna device 204 may also function as a four-channel MIMO (Multiple Input Multiple Output) antenna in a manner similar to the antenna device 203 of
Although an antenna, an antenna device, and a wireless device according to the present invention have been described above with respect to certain illustrative embodiments, the present invention is not limited to these embodiments and various modifications and improvements may be made without departing from the scope of the present invention.
For example, the configuration of the antenna is not limited to the specific embodiments described above. For example, the antenna may include a conductor portion that is directly connected to a radiating element or indirectly connected to the radiating element via a connection conductor. Also, the antenna may include a conductor portion that is coupled to a radiating element through high-frequency (e.g., capacitive) coupling.
Also, the feeding element, the radiating element, and the control element are not limited to linear conductors extending linearly but may include a curved conductor portion. For example, the feeding element, the radiating element, and/or the control element may include an L-shaped conductor portion, a meander-shaped conductor portion, or a conductor portion with branches spreading out from an intermediate point.
Also, the transmission line including the ground plane is not limited to a microstrip line. For example, a strip line or a coplanar waveguide with a ground plane (coplanar waveguide with a ground plane arranged on a surface on the opposite side of a conductor surface) may be used.
Also, the outer profile of the ground plane is not limited those illustrated in the drawings. That is, the ground plane may be a conductive pattern having other outer profiles. Also, the ground plane is not limited to a planar shape and may alternatively be arranged into a curved shape, for example. Similarly, the outer profile of the plate conductor is not limited to those illustrated in the drawings but it may be a conductor having other outer profiles. Also, the plate conductor is not limited to a planar shape and may alternatively be arranged into a curved shape.
Also, note that the term “plate” used above in describing the configuration of a conductor and the like may also encompass configurations arranged into a “foil” or a “film”, for example.
Also, note that by arranging the lengths of the radiating elements (e.g., radiating elements 30 and 40 in the case of
Also, by controlling the directivity of the antennas provided in an antenna device to be directed in the same direction, the antenna device may function as a diversity antenna.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-131195 | Jun 2013 | JP | national |
The present application is a continuation application filed under 35 U.S.C. 111(a) claiming benefit under 35 U.S.C. 120 and 365(c) of PCT International Application No. PCT/JP2014/066334 filed on Jun. 19, 2014 and designating the U.S., which claims priority to Japanese Patent Application No. 2013-131195 filed on Jun. 21, 2013. The entire contents of the foregoing applications are incorporated herein by reference.
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| Number | Date | Country | |
|---|---|---|---|
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| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2014/066334 | Jun 2014 | US |
| Child | 14960967 | US |
