Patent Grant
9537203
The present invention relates to an antenna device which uses a liquid that has electric conductivity (hereinafter, referred to as a conductive liquid) as a radiating element.
In recent years, antenna devices which use a conductive liquid as a radiating element have been attracting attention.
Since it is possible for a conductive liquid to operate as an antenna in any shape by flowing an electric current through the conductive liquid, a conductive liquid can be used as various types of antennas if an electric power can be fed in an efficient manner.
Conventional methods of feeding power to a conductive liquid include the following method.
Patent Document 1 described below discloses an antenna device in which a conducting wire is wound around a ring-shaped magnetic body and a current is passed through the conducting wire to generate a magnetic flux in the magnetic body. In the antenna device, by linearly ejecting a conductive liquid through a hole provided, in the ring-shaped magnetic body, power is fed to the conductive liquid due to magnetic field coupling.
Note that an operating frequency can be adjusted by controlling the ejection force of the conductive liquid and, accordingly, low-frequency communication can be performed without installing a large-size antenna.
Patent Document 1: U.S. patent application Ser. No. 12/539,834
Since a conventional antenna device is configured as described above, a magnetic body is used to feed power to a conductive liquid. However, there is a problem in that radiation efficiency deteriorates due to a significant loss at the magnetic body.
In addition, an unnecessary current flows in a water supply-side of the conductive liquid, and since no means for suppressing the unnecessary current is provided, there is a problem in that loss or an impedance mismatch is created by the unnecessary current on the water supply-side.
The present invention has been made in order to solve the problems described above and an object thereof is to obtain an antenna device which is capable of preventing radiation efficiency from deteriorating and which is capable of suppressing an unnecessary current.
An antenna device according to the present invention includes: a grounding conductor on which a hole is formed; a conductive hollow tube which is brought into tight contact with a surface of the grounding conductor at a position where a first end of the conductive hollow tube having an opening plane whose inner diameter matches a diameter of the hole formed on the grounding conductor overlaps with the hole and which is bent so that an opening plane of a second end of the conductive hollow tube on an opposite side to the first end faces an opposite direction to the surface of the grounding conductor and that an intermediate portion between the first end and the second end is arranged parallel to the grounding conductor; and a power feeder line conductor with one end connected to a high-frequency power supply and another end connected to a side surface of the intermediate portion at a position at a distance of ¼ wavelength in an operating frequency from the first end, wherein a conductive liquid supplied from the opening plane of the first end is passed through the conductive hollow tube and discharged to the outside from the opening plane of the second end.
By adopting the configuration described above, the present invention achieves the effects of preventing radiation efficiency from deteriorating and suppressing an unnecessary current.
Hereinafter, in order to describe the present invention in greater detail, modes for carrying out the present invention will be described with reference to the accompanying drawings.
In
A conductive hollow tube 3 is brought into tight contact with a top surface (a front surface) of the grounding conductor 1a at the position where a first end thereof (in the diagrams, the left-side end), which has an opening plane 4a whose inner diameter matches a diameter of the hole 2a formed on the grounding conductor 1, overlaps with the hole 2a.
In addition, the conductive hollow tube 3 is bent so that an opening plane 4b of a second end (in the diagrams, the right-side end) on an opposite side to the first end faces a top surface direction (an opposite direction to the top surface of the grounding conductor 1) and that an intermediate portion between the first end and the second end is arranged parallel to the grounding conductor 1.
A meshed conductor 5a is a conductor arranged so as to cover the opening plane 4a of the first end in the conductive hollow tube 3.
A meshed conductor 5b is a conductor arranged so as to cover the opening plane 4b of the second end in the conductive hollow tube 3.
Mesh coarseness of the meshed conductors 5a and 5b is desirably selected so as to be coarse enough not to obstruct the flow of conductive liquids 8a and 8b but sufficiently fine with respect to the wavelength of an operating frequency (a frequency to be used).
A coaxial line outer conductor 6 is a hollow tube conductor which has an inner diameter that matches a diameter of the hole 2b of the grounding conductor 1 and which is brought into tight contact with a bottom surface of the grounding conductor 1a at a position where one end thereof overlaps with the hole 2b.
A coaxial line inner conductor 7 is a conductor having an outer diameter that is smaller than the inner diameter of the coaxial line outer conductor 6 and is arranged to be coaxial with the coaxial line outer conductor 6.
One end of the coaxial line inner conductor 7 is connected to a high-frequency power supply (not shown in drawings) and another end is connected to a side surface of the intermediate portion of the conductive hollow tube 3 at the position at the distance of ¼ wavelength in an operating frequency from the first end of the conductive hollow tube 3.
Note that, a coaxial line structure that is made up of the coaxial line outer conductor 6 and the coaxial line inner conductor 7 constitute a power feeder line conductor.
The conductive liquid 8a is a liquid with electric conductivity that is supplied to the inside of the conductive hollow tube 3 through the opening plane 4a of the conductive hollow tube 3 from the lower side of the hole 2a formed on the grounding conductor 1.
The conductive liquid 8b is a liquid with electric conductivity that is ejected to the outside from the opening plane 4b of the second end through the inside of the conductive hollow tube 3 and operates as an antenna.
Moreover, the distance between a tip of the conductive liquid 8b and the grounding conductor 1 has the height corresponding to ¼ wavelength in the operating frequency.
Next, operations will be described.
When the high-frequency power supply (not shown in drawings) connected to one end of the coaxial line inner conductor 7 generates high-frequency voltage, the coaxial line outer conductor 6 and the coaxial line inner conductor 7 operate as a power feeder line and high-frequency power is supplied via the conductive hollow tube 3 connected to the other end of the coaxial line inner conductor 7 to the conductive liquid 8b that operates as an antenna.
In this case, since high-frequency power is not only supplied to the conductive liquid 8b that operates as an antenna but is also supplied to the water supply-side conductive liquid 8a, antenna performance is adversely affected.
In the antenna device shown in
The input impedance Zt when viewing a short-circuit side (the side of the opening plane 4a of the first end) from a supply point of high-frequency power (the point where the coaxial line inner conductor 7 is connected to the conductive hollow tube 3) is expressed by the expression (1) below.
Zt=jZ0 tan {(2π/λ)L} (1)
Z0: characteristic impedance of transmission line constituted by conductive hollow tube 3 and grounding conductor 1
L: distance between supply point of high-frequency power to short-circuit point
λ: wavelength with respect to operating frequency
As is apparent from expression (1), when the distance L is set to a length around ¼ wavelength, the input impedance Zt when the short-circuit side is viewed from the supply point of high-frequency power becomes infinitely large.
In the antenna device shown in
In
In the following numerical calculations, sea water is adopted as an example of the conductive liquids 8a and 8b, and relative permittivity is assumed to be 81, and conductivity is assumed to be 4 S/m.
In
In
In this case, since the distance from a tip of the ejected conductive liquid 8b to the grounding conductor 1 corresponds to the length of ¼ wavelength in the operating frequency, the conductive liquid 8b enters a resonant state and radiates high-frequency waves.
Is shown in
This indicates that the antenna device is sufficiently operating as a monopole antenna on the grounding conductor 1.
In addition, radiation efficiency is approximately 70% with a loss of 30%. However, as described above, since an unnecessary current to the water supply-side conductive liquid 8a is suppressed, most of the loss is due to the ejected conductive liquid 8b and the loss at a power feeding section is approximately zero.
As is apparent from the description provided above, by configuring Embodiment 1 so as to include the conductive hollow tube 3 which is brought into tight contact with the top surface of the grounding conductor 1a at a position where the first end having the opening plane 4a whose inner diameter matches a diameter of the hole 2a formed on the grounding conductor 1 overlaps with the hole 2a, and which is bent so that the opening plane 4b of the second end faces a top surface direction and that the intermediate portion between the first end and the second end is arranged parallel to the grounding conductor 1, wherein a conductive liquid supplied from the opening plane 4a of the first end is passed through the conductive hollow tube 3 and discharged to the outside from the opening plane 4b of the second end, the effects of preventing radiation efficiency from deteriorating and suppressing an unnecessary current can be achieved.
In other words, according to Embodiment 1, since a loss at a power feeding section can be substantially eliminated by directly supplying high-frequency power to the conductive liquid 8b, an effect of suppressing deterioration of radiation efficiency can be achieved. In addition, by shorting the conductive hollow tube 3 at a position apart from the power supply point by around ¼ wavelength to the grounding conductor 1, an effect of suppressing an unnecessary current that flows to the conductive liquid 8a can be achieved.
In
A hole 2c is formed on a grounding conductor 1.
In a conductive hollow tube 11, the distance between a first end (in the diagrams, the left-side end) arranged on the rear surface side of the grounding conductor 1 and a second end (in the diagrams, the right-side end) having an opening plane 12b whose outer diameter is smaller than the diameter of the hole 2c formed on the grounding conductor 1 is the length of ¼ wavelength in an operating frequency.
In addition, the conductive hollow tube 11 is arranged so that the height of the second end is the same as the height of a top surface (a front surface) of the grounding conductor 1 and a central axis of the opening plane 12b of the second end is aligned with a central axis of the hole 2c, and is bent so that an intermediate portion between the first end and the second end is arranged parallel to the grounding conductor 1.
A meshed conductor 13a is a conductor arranged so as to cover an opening plane 12a of the first end in the conductive hollow tube 11.
A meshed conductor 13b is a conductor arranged so as to cover the opening plane 12b of the second end in the conductive hollow tube 11.
Mesh coarseness of the meshed conductors 13a and 13b is desirably selected so as to be coarse enough not to obstruct the flow of conductive liquids 8a and 8b but sufficiently fine with respect to the wavelength of an operating frequency.
A coaxial line outer conductor 14 is a hollow tube conductor which is arranged so that a side surface thereof comes into tight contact with the top surface of the grounding conductor 1. In
A coaxial line inner conductor 15 is a columnar conductor having an outer diameter that is smaller than the inner diameter of the coaxial line outer conductor 11 and is arranged to be coaxial with the coaxial line outer conductor 14.
One end of the coaxial line inner conductor 15 is connected to a high-frequency power supply (not shown in drawings) and another end is connected to an outer circumference of the second end of the conductive hollow tube 11.
Moreover, a coaxial line structure that is made up of the coaxial line outer conductor 14 and the coaxial line inner conductor 15 constitute a power feeder line conductor.
One end of a shorting conductor 16 is connected to the grounding conductor 1 and another end is connected to an outer circumference of the first end of the conductive hollow tube 11.
While the shorting conductor 16 is used to make a short-circuit between the grounding conductor 1 and the conductive hollow tube 11, alternatively, the grounding conductor 1 and the conductive hollow tube 11 may be brought into direct contact with each other.
Next, operations will be described.
When the high-frequency power supply (not shown in drawings) connected to one end of the coaxial line inner conductor 15 generates high-frequency voltage, the coaxial line outer conductor 14 and the coaxial line inner conductor 15 operate as a power feeder line and high-frequency power is supplied via the conductive hollow tube 11 connected to the other end of the coaxial line inner conductor 15 to the conductive liquid 8b that operates as an antenna.
In this case, since high-frequency power is not only supplied to the conductive liquid 8b that operates as an antenna but is also supplied to the water supply-side conductive liquid 8a, antenna performance is adversely affected.
In the antenna device shown in
In addition, since the distance between the first end of the conductive hollow tube 11 (a short-circuit point with respect to the grounding conductor 1) and the second end of the conductive hollow tube 11 (a supply point of high-frequency power) corresponds to the length of ¼ wavelength in the operating frequency, the input impedance Zt when the short-circuit side is viewed from the supply point of high-frequency power becomes infinitely large and high-frequency power is not supplied to the short-circuit side. Therefore, consumption of high-frequency power by the water supply-side conductive liquid 8a can be suppressed.
In the antenna device shown in
In addition, in the antenna device shown in
As shown in
From
As is apparent from the description provided above, according to Embodiment 2, in addition to achieving similar effects to Embodiment 1, since the conductive hollow tube 11 is arranged on the bottom surface (rear surface) of the grounding conductor 1, an effect of suppressing cross polarization in the top surface direction of the grounding conductor 1 can be achieved.
In
A hole 2d is formed on a grounding conductor 1.
In a conductive hollow tube 21 that is a first conductive hollow tube, the distance between a first end (in the diagrams, the upper end) having an opening plane 22a whose inner diameter matches a diameter of the hole 2d formed on the grounding conductor 1 and a second end (in the diagrams, the lower end) having an opening plane 22b with an inner diameter matching a diameter of the hole 2d is the length of ¼ wavelength in an operating frequency.
In addition, the conductive hollow tube 21 is arranged perpendicular to the grounding conductor 1 so as to come into tight contact with the bottom surface (rear surface) of the grounding conductor 1 at a position where the first end overlaps with the hole 2d.
In a conductive hollow tube 23 that is a second conductive hollow tube, the distance between a first end having an opening plane 24a with an outer diameter that is smaller than an inner diameter of the conductive hollow tube 21 and a second end having an opening plane 24b with an outer diameter that is smaller than an inner diameter of the conductive hollow tube 21 is the length of ¼ wavelength in the operating frequency.
In addition, the conductive hollow tube 23 is arranged to be coaxial with the conductive hollow tube 21 so that the height of the first end is the same as the height of the top surface (the front surface) of the grounding conductor 1.
A meshed conductor 25a is a conductor arranged so as to cover the opening plane 24a of the first end in the conductive hollow tube 23.
A meshed conductor 25b is a conductor arranged so as to cover the opening plane 24b of the second end in the conductive hollow tube 23.
Mesh coarseness of the meshed conductors 25a and 25b is desirably selected so as to be coarse enough not to obstruct the flow of conductive liquids 8a and 8b but sufficiently fine with respect to the wavelength of an operating frequency.
A coaxial line outer conductor 26 is a hollow tube conductor which is arranged so that a side surface thereof comes into tight contact with the top surface of the grounding conductor 1. In
A coaxial line inner conductor 27 is a columnar conductor having an outer diameter that is smaller than the inner diameter of the coaxial line outer conductor 26 and is arranged to be coaxial with the coaxial line outer conductor 26.
One end of the coaxial line inner conductor 27 is connected to a high-frequency power supply (not shown in drawings) and another end is connected to an outer circumference of the first end of the conductive hollow tube 23.
Moreover, a coaxial line structure that is made up of the coaxial line outer conductor 26 and the coaxial line inner conductor 27 constitute a power feeder line conductor.
A shorting conductor 28 is a conductor which shorts the second end of the conductive hollow tube 21 and the second end of the conductive hollow tube 23 to each other.
Next, operations will be described.
When the high-frequency power supply (not shown in drawings) connected to one end of the coaxial line inner conductor 27 generates high-frequency voltage, the coaxial line outer conductor 26 and the coaxial line inner conductor 27 operate as a power feeder line and high-frequency power is supplied via the conductive hollow tube 23 connected to the other end of the coaxial line inner conductor 27 to the conductive liquid 8b that operates as an antenna.
In this case, since high-frequency power is not only supplied to the conductive liquid 8b that operates as an antenna but is also supplied to the water supply-side conductive liquid 8a, antenna performance is adversely affected.
In the antenna device shown in
In addition, since the distance between the first end of the conductive hollow tube 23 (a supply point of high-frequency power) and the second end that is a tip of the conductive hollow tube 23 (a short-circuit point) corresponds to the length of ¼ wavelength in the operating frequency, the input impedance Zt when the short-circuit side is viewed from the supply point of high-frequency power becomes infinitely large and high-frequency power is not supplied to the short-circuit side. Therefore, consumption of high-frequency power by the water supply-side conductive liquid 8a can be suppressed.
Furthermore, since the conductive hollow tube 21 and the conductive hollow tube 23 operate as a coaxial line, matching can be realized, at a desired impedance by changing the diameter of the conductive hollow tube 21 or the conductive hollow tube 23.
As shown in
As is apparent from the description provided above, according to Embodiment 3, in addition to achieving similar effects to Embodiment 1, since a coaxial line that is made up of the conductive hollow tube 21 and the conductive hollow tube 23 form a tip-shorted transmission line and the length of the coaxial line corresponds to the length of ¼ wavelength in the operating frequency, the following effects can be achieved: it is possible to adjust impedance matching; and the cross polarization that is radiated from the present antenna device can be suppressed in all directions.
In
A slotted hole 31 is a hole having a linearly extending shape formed on a grounding conductor 1 so as to extend along an intermediate portion of a conductive hollow tube 3.
A shorting conductor 32 is a conductor that establishes conduction between the grounding conductor 1 and the conductive hollow tube 3 in a state of being inserted into the slotted hole 31 formed on the grounding conductor 1 and is movable along the slotted hole.
In other words, the shorting conductor 32 is a columnar (or prismatic) conductor with a diameter similar to the hole width of the slotted hole 31 and is arranged so that the grounding conductor 1 and the conductive hollow tube 3 are electrically shorted to each other.
In this Embodiment 4, by adjusting the water amount of a conductive liquid 8a that is supplied from the hole 2a, the distance between a tip of a conductive liquid 8b and the grounding conductor 1 can be controlled to the height of around ¼ wavelength corresponding to a desired operating frequency.
In addition, the conductive hollow tube 3 is shorted to the grounding conductor 1 via the shorting conductor 32 and a tip-shorted transmission line is formed by the intermediate portion where the conductive hollow tube 3 and the grounding conductor 1 are arranged parallel to each other.
In this case, by moving the shorting conductor 32 inside the slotted hole 31, the distance from the supply point of high-frequency power to the short-circuit point of the conductive hollow tube 3 and the grounding conductor 1 (the point at the position of the shorting conductor 32) can be controlled to the length of around ¼ wavelength corresponding to the desired operating frequency.
As is apparent from the description provided above, according to this Embodiment 4, in addition to achieving similar effects to Embodiment 1, by adjusting the position of the shorting conductor 32 while controlling the election momentum of the conductive liquid 8b, an effect of obtaining an antenna device with variable operating frequency can be achieved.
A hole 40 is a water supply hole formed at a lower position (on a side of a second end) of a conductive hollow tube 21.
A conductive liquid 8c is a second conductive liquid which is supplied from the hole 40 and which is stored inside a coaxial line structure constituted by conductive hollow tubes 21 and 23 and a shorting conductor 23.
In this Embodiment 5, by adjusting the water amount of the conductive liquid 8a that is supplied from the opening plane 24b, the distance between a tip of the conductive liquid 8b and the grounding conductor 1 can be controlled to the height of around ¼ wavelength corresponding to a desired operating frequency.
In addition, since the conductive hollow tube 21 and the conductive hollow tube 23 are shorted to each other at the position of the water surface of the conductive liquid 8c, a tip-shorted transmission line is formed.
By adjusting the water amount of the conductive liquid 8c that is supplied from the hole 40, the distance between the supply point of high-frequency power and the position of the water surface of the conductive liquid 8c (a short-circuit point) can be controlled to around ¼ wavelength corresponding to the desired operating frequency.
As is apparent from the description provided above, according to this Embodiment 5, in addition to achieving similar effects to Embodiment 3, by controlling a force by which the conductive liquid 8b is ejected and adjusting the water amount of the conductive liquid 8c, an effect of obtaining an antenna device with variable operating frequency can be achieved.
Note that, it is to be understood that the respective embodiments of the present invention may be combined in any way and any component of the respective embodiments of the present invention may be modified or omitted without departing from the spirit and scope of the invention.
Since the antenna device according to the present invention is configured so as to be provided with a conductive hollow tube which includes: a first end having an opening plane whose inner diameter matches a diameter of a hole formed on a grounding conductor and brought into tight contact with a surface of the grounding conductor at a position where the opening plane and the hole overlap with each other; and a second end on an opposite side to the first end and having an opening plane in an opposite direction to the grounding conductor, and which is bent so that an intermediate portion between the first end and the second end becomes parallel to the grounding conductor, wherein a conductive liquid supplied from the opening plane of the first end is passed through the conductive hollow tube and discharged to the outside from the opening plane of the second end, the antenna device is capable of preventing radiation efficiency from deteriorating and suppressing an unnecessary current, and can be preferably used in cases where a conductive liquid is used as a radiating element.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-018449 | Feb 2014 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2015/051875 | 1/23/2015 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2015/115333 | 8/6/2015 | WO | A |
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| 4498086 | Sandler | Feb 1985 | A |
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| 8368605 | Tam | Feb 2013 | B1 |
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| Number | Date | Country | |
|---|---|---|---|
| 20160308273 A1 | Oct 2016 | US |
