antenna

Abstract

An antenna for wireless communication through a lossy medium, wherein the structure thereof is optimized and transmission characteristics such as the transmission coefficient are improved.　The antenna comprises at least one pair of electrodes and a sheath part. The sheath part contains wiring that electrically connects each electrode of the at least one pair of electrodes and a corresponding power supply terminal. The sheath part is also referred to as a sheath. In this antenna, the minimum diameter of the electrodes is greater than the width of the wiring that is contained in the sheath part. The shape of each electrode of the at least one pair of electrodes is, for example, substantially spherical.

Description

[Technical Field]

[0001] The present technology relates to antennas, and more particularly to antennas for wireless communication through lossy media. [Background technology]

[0002] A half-sheath dipole antenna, with a part of the element exposed, has been proposed as an antenna for wireless communication through a lossy medium. This half-sheath dipole antenna is known to have higher impedance characteristics than a dipole antenna without a sheath and a transmission coefficient superior to a full-sheath dipole antenna (see, for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] H. Sato et al., "Dipole antenna with sheath-cover for seawater use," 2017 International Symposium on Antennas and Propagation (ISAP), 1376, pp. 1-2 (2017). Summary of the Invention [Problem to be solved by the invention]

[0004] Although the transmission characteristics of the above-mentioned half-sheath dipole antenna have been analyzed using electromagnetic field simulations, the principles have not been fully elucidated, and the optimal structure is not necessarily clear.

[0005] This technology was developed in light of these circumstances, and aims to optimize the structure of antennas for wireless communication via lossy media to improve transmission characteristics. [Means for solving the problem]

[0006] The present technology has been made to solve the above-mentioned problems, and a first aspect thereof is an antenna including at least a pair of electrodes and a sheath containing wiring electrically connecting each of the at least a pair of electrodes to its corresponding power supply terminal, the minimum diameter of the electrodes being larger than the width of the wiring. This brings about the effect that the minimum diameter of the electrodes connected to the wiring contained in the sheath is larger than the width of the wiring. As will be described later, it is preferable that the diameter of the electrodes is larger.

[0007] In this first aspect, the distance between the at least one pair of electrodes may be longer than the smallest diameter of the electrodes. As will be described later, it is preferable that the distance between the electrodes is wide.

[0008] In this first aspect, each of the at least one pair of electrodes may be substantially spherical, spheroidal, or polyhedral. As will be described later, the closer the electrode shape is to a sphere, the better.

[0009] In addition, in this first aspect, the sheath may have a columnar shape extending in a direction connecting the at least one pair of electrodes, and the sheath may have a shape branching from the columnar shape.

[0010] In this first aspect, the sheath may contain air or pure water therein. The sheath may also contain a material having a conductivity of less than 1 S / m therein.

[0011] In addition, in this first aspect, each of the at least one pair of electrodes may have a coating on the surface.

[0012] In addition, in this first aspect, it is desirable that the magnitude of the impedance at the operating frequency between each of the at least one pair of electrodes and the external medium is smaller than the impedance when the coating is not provided.

[0013] In addition, in this first aspect, each of the at least one pair of electrodes may contain a material therein having a conductivity of less than 1 S / m.

[0014] In addition, in this first aspect, each of the at least one pair of electrodes may have a cavity therein. In this case, each of the at least one pair of electrodes may have at least one hole penetrating into the cavity.

[0015] In addition, in the first aspect, a voltage transformer may be further provided in which the number of turns of the coil connected to the power supply terminal is smaller than the number of turns of the other coil, thereby achieving impedance matching.

[0016] In addition, in this first aspect, a switching power amplifier may be further provided connected to the power supply terminal, thereby achieving the effect of impedance matching. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram illustrating an example of the overall configuration of a wireless communication system according to an embodiment of the present technology. [Figure 2] 2A to 2C are diagrams illustrating examples of shapes of electrodes 130 of antennas 101 and 102 according to an embodiment of the present technology. [Figure 3] 10A and 10B are diagrams illustrating an example of a structure of wiring connections inside an electrode 130 according to an embodiment of the present technology. [Figure 4] 3A and 3B are diagrams illustrating an example of the structure of a cavity inside an electrode 130 according to an embodiment of the present technology. [Figure 5] 10 is a diagram showing an example in which two pairs of electrodes 130 are provided in the embodiment of the present technology. FIG. [Figure 6] 1 is a diagram showing equivalent circuits of antennas 101 and 102 according to an embodiment of the present technology. [Figure 7] 10A and 10B are diagrams illustrating an example of an electric field generated around an electrode 130 according to the embodiment of the present technology. [Figure 8]1 is a diagram showing an example of arrangement of antennas 101 and 102 according to an embodiment of the present technology. [Figure 9] 10 is a diagram illustrating an example of the relationship between the center-to-center distance of electrodes 130 and the transmission coefficient according to the embodiment of the present technology. FIG. [Figure 10] 10 is a diagram illustrating an example of the relationship between the closest distance and the transmission coefficient of the electrode 130 according to the embodiment of the present technology. FIG. [Figure 11] 10 is a diagram illustrating an example of the relationship between the conductivity and the transmission coefficient of an electrode 130 according to the embodiment of the present technology. [Figure 12] 5 is a diagram showing an example of the relationship between the coating thickness and the permeability coefficient of the electrode 130 according to the embodiment of the present technology. FIG. [Figure 13] 4 is a diagram illustrating a first example of measures to deal with impedance of an antenna according to the embodiment of the present technology. [Figure 14] FIG. 10 is a diagram illustrating a second example of measures to deal with impedance of the antenna according to the embodiment of the present technology. [Figure 15] 10A and 10B are diagrams illustrating another example of the structure of the sheath 110 according to the embodiment of the present technology. [Figure 16] 10A and 10B are diagrams illustrating still another structural example of the sheath portion 110 according to the embodiment of the present technology. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, modes for carrying out the present technology (hereinafter referred to as embodiments) will be described in the following order. 1. Embodiment (antenna) 2. Application example (connection to radio)

[0019] <1. Embodiment> [Wireless communication system] FIG. 1 is a diagram showing an example of the overall configuration of a wireless communication system according to an embodiment of the present technology.

[0020] This wireless communication system includes a transmission circuit 310 and a reception circuit 320 as radio devices that perform wireless communication. That is, the transmission circuit 310 transmits a wireless signal to the reception circuit 320, and the reception circuit 320 receives the wireless signal from the transmission circuit 310. The transmission circuit 310 and the reception circuit 320 include antennas 101 and 102, respectively, and perform wireless communication via the antennas 101 and 102.

[0021] The wireless communication between the transmitting circuit 310 and the receiving circuit 320 is carried out via a lossy medium, which may be, for example, seawater or the human body.

[0022] Each of the antennas 101 and 102 includes a pair of electrodes 130 and a sheath 110. The sheath 110 contains a pair of wires 120 that electrically connect the electrodes 130 to the power supply terminals 190 corresponding to the electrodes 130. The sheath 110 is also called a sheath.

[0023] The sheath 110 has, for example, a columnar shape extending in a direction connecting the pair of electrodes 130. This columnar shape may be a circular cylinder or a rectangular cylinder. As will be described later, it may also be a columnar shape that branches off midway.

[0024] The sheath 110 may contain a low-loss dielectric inside. Examples of the low-loss dielectric include air, pure water, resin, glass, and ceramic materials. The low-loss dielectric inside the sheath 110 may be made of multiple materials.

[0025] Here, air has the lowest loss as a low-loss dielectric inside the sheath 110, but is not suitable for environments with high water pressure. On the other hand, pure water is more suitable as a low-loss dielectric inside the sheath 110 in environments with high water pressure.

[0026] Furthermore, when resin, glass, ceramic, or the like is used as the low-loss dielectric inside the sheath 110, care must be taken to prevent external media such as seawater from penetrating and coming into contact with the wiring 120. However, it is acceptable for external media to penetrate into the low-loss dielectric as long as they do not come into contact with the wiring 120.

[0027] The conductivity of the low-loss dielectric inside the sheath 110 is preferably less than 1 S / m, and more preferably less than 0.1 S / m.

[0028] [electrode] FIG. 2 is a diagram showing an example of the shape of the electrodes 130 of the antennas 101 and 102 according to the embodiment of the present technology.

[0029] The electrode 130 is preferably spherical as shown in Fig. 1A, but any shape close to a sphere will suffice. For example, it may be ellipsoidal as shown in Fig. 1B.

[0030] Furthermore, for manufacturing reasons, the surface may not be smooth, and a polyhedron may be used, as shown in Fig. 1C. In this case, a polyhedron with 20 or more faces is desirable, but it does not necessarily have to have 20 or more faces, and it does not necessarily have to be a regular polyhedron.

[0031] Regardless of the shape of the electrode 130 , it is desirable that the minimum diameter of the electrode 130 be greater than the width of the wiring 120 .

[0032] Possible materials for the electrode 130 include, for example, highly corrosion-resistant metals such as copper (Cu), aluminum (Al), gold (Au), platinum (Pt), and silver (Ag), as well as alloys of these metals.

[0033] Furthermore, a dielectric may be provided inside electrode 130. In this case, the dielectric inside electrode 130 may be made of a plurality of materials. In this case, the conductivity of the dielectric inside electrode 130 is less than 1 S / m.

[0034] A coating for corrosion prevention may be applied to the surface of the electrode 130. The type of coating may be any of a metal coating, an inorganic coating, and an organic coating.

[0035] For example, plating, metal spraying, metal diffusion, etc. are used to coat the surface of the electrode 130 with metal. In this case, it is desirable to use a material with high electrical conductivity as the metal substance.

[0036] When applying an inorganic coating to the surface of the electrode 130, for example, a coating or lining of glass, enamel, mortar, concrete, or the like is used. When applying an organic coating to the surface of the electrode 130, for example, a coating or lining of paint, rubber, plastic, or the like is used. However, it is preferable to make the coating as thin as possible or to select a material with as high a dielectric constant as possible so that the capacitance generated by the coating is sufficiently large. Specifically, it is desirable that the magnitude of the impedance at the operating frequency between the electrode and the external medium be smaller than the impedance when the surface of the electrode 130 is not provided with a coating.

[0037] FIG. 3 is a diagram showing an example of the structure of the internal wiring connection of the electrode 130 according to the embodiment of the present technology.

[0038] The wiring 120 connected to the power supply terminal 190 and the electrode 130 may be connected in any manner. That is, the connection may be at the nearest point as shown in a in the figure, or at the farthest end as shown in b in the figure. Alternatively, the connection may be midway between the nearest point and the farthest end as shown in c in the figure. Furthermore, the connection may be made at multiple points on the electrode 130 as shown in d in the figure.

[0039] FIG. 4 is a diagram showing an example of the structure of the cavity inside the electrode 130 according to the embodiment of the present technology.

[0040] In order to avoid deformation due to the pressure difference between the inside and outside of the electrode 130, a cavity 138 may be provided inside the electrode 130, and at least one hole 139 may be provided that penetrates the cavity 138. An external medium such as seawater will enter the cavity 138 through this hole 139. In this case, it is desirable to secure a low-loss material on the inside near the electrode 130.

[0041] A certain number of holes 139 may be provided penetrating the cavity 138. However, if there are too many holes 139, the surface area of ​​the electrode 130 will be reduced, which may cause the electric field to be concentrated in certain areas, resulting in loss.

[0042] FIG. 5 is a diagram showing an example in which two pairs of electrodes 130 are provided in the embodiment of the present technology.

[0043] In this example, electrodes 130 are provided at each of the four ends of a cross-shaped sheath portion 110, and wiring 120 is included to electrically connect each electrode 130 to a corresponding power supply terminal 190.

[0044] By providing two pairs of electrodes 130 in this way, it becomes possible to apply the antenna to circularly polarized waves or dual polarized waves.

[0045] [Characteristics analysis] FIG. 6 is a diagram showing equivalent circuits of the antennas 101 and 102 according to the embodiment of the present technology.

[0046] Here, the impedance is formulated by assuming that the portion corresponding to electrode 130 is cylindrical. The equivalent circuits for antennas 101 and 102 are assumed to be antennas in a lossy medium, and are shorter than the wavelength. The length corresponding to sheath 110 is Ls, and the length corresponding to electrode 130 is L. The radius of the cylindrical conductor corresponding to electrode 130 is rcyl.

[0047] The antenna portion of the cylindrical conductor can be considered as a series connection of an inductance 611 or 612 and a resistance 621 or 622. Here, the reactance of the inductance 611 or 612 is set to Lhs / 2, respectively. Also, the resistance value of the resistance 621 or 622 is set to Rhs / 2, respectively.

[0048] The external medium such as seawater can be considered as a parallel connection of resistance 631 or 632 and capacitance 641 or 642. Here, the conductance of resistance 631 or 632 is assumed to be 2 Ghs, and the electrostatic capacity of capacitance 641 or 642 is assumed to be 2 Chs.

[0049] In this case, the impedance Zhs seen from the power supply terminal 190 is obtained by the following equation.

number

number

[0050] Furthermore, when the electrodes 130 at both ends of the sheath 110 are far enough apart that their electric field does not affect the charge distribution, the conductance between the electrodes 130 is half that of a single electrode. Therefore, the conductance Ghs is given by the following equation: where rell is defined as half the value of the minor axis of an ellipse with the same area as a cylinder of length l and radius rcyl and whose focal coordinates are (±l / 2,0).

number

[0051] Thus, the real part of the impedance Zhs is given by the following equation:

number

[0052] That is, the smaller the radius rcyl of the cylindrical conductor corresponding to electrode 130, the larger the real part of the impedance, making impedance matching easier. However, as the impedance increases, the current decreases under constant power conditions, and the charge on electrode 130 decreases. This weakens the electric field and reduces efficiency. Furthermore, as the impedance increases, the surrounding electric field remains unchanged under constant current conditions, but the voltage increases, increasing the input power and reducing efficiency. Therefore, under any conditions, efficiency decreases as the radius rcyl decreases. This shows that a larger diameter for electrode 130 is preferable.

[0053] FIG. 7 is a diagram showing an example of an electric field generated around the electrode 130 according to the embodiment of the present technology.

[0054] The electric field around a conductor with the same charge is considered to be isotropic at a distance sufficiently large compared to the size of the conductor, regardless of the shape of the conductor. In other words, for objects with the same surface area, the charge density on the surface is the same, so the density of electric field lines near the surface of the conductor, i.e., the electric field strength, is the same.

[0055] On the other hand, when considering a location farther from the conductor, the electric field strength decreases inversely proportional to the square of the distance for the sphere shown in FIG. 1A. In contrast, the electric field strength decreases more gradually near the conductor for the cylinder shown in FIG. 1B. This results in increased loss for the cylinder. Therefore, it can be seen that a spherical shape is better for electrode 130.

[0056] FIG. 8 is a diagram showing an example of the arrangement of antennas 101 and 102 according to the embodiment of the present technology.

[0057] Under the condition of a distance d between antennas 101 and 102, the transmission coefficient τ between the antennas is expressed by the following equation: where Kcorr is a correction coefficient for correcting the electrostatic field distribution to a high-frequency electric field distribution that includes the contributions of displacement current and radiation.

number

number

[0058] As a result, the transmission coefficient τ is inversely proportional to the square of the impedance. In other words, the lower the impedance, the larger the transmission coefficient τ. Since the transmission coefficient indicates the power efficiency when the transmitter and receiver are ideally matched, it can be seen that the lower the impedance, the better the power efficiency.

[0059] Fig. 9 is a diagram showing an example of the relationship between the center-to-center distance of electrodes 130 and the transmission coefficient according to the embodiment of the present technology. Fig. 10 is a diagram showing an example of the relationship between the closest distance of electrodes 130 and the transmission coefficient according to the embodiment of the present technology.

[0060] These results were obtained by performing a finite element method full-wave analysis (HFSS) at 10 kHz in seawater (relative permittivity εr = 80, conductivity σ = 4 S / m). The diameter of the sheath 110 was 0.1 m, and the spacing between the electrodes 130 was variable. Copper was assumed to be the material for the electrodes 130. The physical properties of the sheath 110 were: relative permittivity εr = 80, conductivity σ = 0.01 S / m.

[0061] Here, three types of shapes were assumed for electrode 130: (1) a sphere with a diameter of 0.5 m, (2) a spheroid with a major axis of 0.5 m and a minor axis of 0.2 m, and (3) a cylinder (HS in the figure) with a length of 0.5 m and a diameter of 0.01 m. The first two correspond to this embodiment, and the latter corresponds to a conventional half-sheath dipole antenna.

[0062] Comparing these, the transmission coefficients are largest for (1) sphere, (2) spheroid, and (3) cylinder, regardless of the center-to-center distance of the electrodes 130 or the closest distance of the electrodes 130. Therefore, even in light of this analysis result, it is desirable for the electrode 130 to be spherical.

[0063] Furthermore, from this result, it can be seen that a wider interval is better when comparing the intervals between the electrodes 130. Specifically, it is desirable that the interval between the electrodes 130 be longer than the smallest diameter of the electrodes 130.

[0064] Furthermore, compared to a conventional half-sheath dipole antenna, this embodiment, which uses a roughly spherical electrode, achieves an improvement of about 15 dB. This corresponds to an expansion of the far-field area to about λ / 3 for the same power, and a reduction of power consumption of about 15 dB (to 1 / 30 or less) for the same communication area.

[0065] FIG. 11 is a diagram showing an example of the relationship between the conductivity and the transmission coefficient of the electrode 130 according to the embodiment of the present technology.

[0066] Here, the structure of electrode 130 is assumed to be one in which a thin film is formed on the surface of the dielectric, and the analysis results are shown for when the conductivity of the dielectric is varied while εr' is fixed at 80. As a result, it can be seen that even if the conductivity is varied, there is no significant effect on the permeability coefficient as long as the conductivity is less than 0.1 S / m. Therefore, there is almost no effect if the conductivity is around tap water (0.01 S / m), and it is thought that the dielectric material does not need to be particularly low-loss.

[0067] FIG. 12 is a diagram showing an example of the relationship between the coating thickness of the electrode 130 and the permeability coefficient according to the embodiment of the present technology.

[0068] Here, the structure of electrode 130 is assumed to be a conductor with a dielectric coating on its surface, and the relative permittivity εr and conductivity σ are varied. The electrode 130 is assumed to be spherical with a radius of 0.25 m, the sheath 110 has a radius of 0.05 m, the length of sheath 110 is 1 m, the radius of wiring 120 is 5 mm, and the distance between antenna 101 and antenna 102 is 2 m.

[0069] The results show that the thinner the coating, the less degradation there is. For example, if the conductivity is σ = 0.1 S / m, even a 1 mm thick coating will only degrade by about 0.5 dB. On the other hand, the amount of degradation increases with lower conductivity.

[0070] <2. Application Examples> [Impedance measures] As described above, the antenna according to the embodiment of the present technology is expected to be used under low impedance conditions. Therefore, when using an antenna with a very low impedance of, for example, about 0.1 ohms, matching with a standard 50 ohm system becomes an issue. Therefore, two methods for dealing with the impedance drop will be described below.

[0071] FIG. 13 is a diagram illustrating a first impedance countermeasure example for an antenna according to the embodiment of the present technology.

[0072] In this example, the transmitter circuit 310 and the receiver circuit 320 are provided with transformers 312 and 322, respectively, to step up and step down the voltage. A transmission signal input to the transmitter circuit 310 with an impedance of 50 ohms is amplified by a power amplifier 311 and supplied to the transformer 312. In this transformer 312, the number of turns of the coil connected to the feed terminal 190 of the antenna 101 is smaller than the number of turns of the other coil connected to the power amplifier 311. This matches the impedance of the transmission signal input to the transmitter circuit 310 and the signal output to the feed terminal 190 of the antenna 101.

[0073] Similarly, in the transformer 322, the number of turns of the coil connected to the power supply terminal 190 of the antenna 102 is smaller than the number of turns of the other coil connected to the LNA (Low Noise Amplifier) ​​321. This allows the impedance of the signal input from the power supply terminal 190 of the antenna 102 to match the impedance of the received signal output from the receiving circuit 320.

[0074] For example, if the turns ratio of the transformers 312 and 322 is set to 6:1, the impedance ratio can be set to 36:1. This makes even a 0.15 ohm antenna appear as 5.4 ohms when viewed from the amplifier side, achieving good matching with a 5 ohm amplifier.

[0075] FIG. 14 is a diagram illustrating a second example of measures to deal with impedance of the antenna according to the embodiment of the present technology.

[0076] In this example, a switching type power amplifier 313 is provided in the transmission circuit 310. This power amplifier 313 can be realized by, for example, a class D amplifier or a class E amplifier. The output of this power amplifier 313 is supplied to the power feeding terminal 190 of the antenna 101.

[0077] Since switching power amplifier 313 is a constant voltage source, ideally the impedance is 0 ohms and the power efficiency is 100%. As a specific example, the impedance of antennas 101 and 102 is approximately 0.15 ohms at an operating frequency of 10 kHz, making it possible to operate with low impedance.

[0078] Although the example shown here is one in which the transformers 312 and 322 and the power amplifier 313 are provided in the transmitting circuit 310, these may be configured as part of the antenna 101 or 102.

[0079] [Sheath structure] In the above-described embodiment, the structure of the sheath 110 is assumed to be a columnar shape extending in the direction connecting the pair of electrodes 130. However, various modifications of the structure of the sheath 110 are possible, as described below.

[0080] FIG. 15 is a diagram showing another structural example of the sheath portion 110 according to the embodiment of the present technology.

[0081] This example of sheath 110 has a T-shaped structure that branches off midway through the pillar shape, allowing wiring 120 to be drawn into wireless device 300. Note that wireless device 300 may be either transmission circuit 310 or reception circuit 320 described above.

[0082] FIG. 16 is a diagram showing yet another structural example of the sheath portion 110 according to the embodiment of the present technology.

[0083] As yet another structural example of the sheath portion 110, as shown in a in the same figure, the sheath portion 110 may be arranged to be attached to the radio device 300, and the wiring 120 may be connected to the radio device 300 so as to pass through the sheath portion 110.

[0084] Also, as shown in FIG. 1B, the entire sheath 110 may be configured to be incorporated inside the wireless device 300.

[0085] Thus, according to an embodiment of the present technology, by providing an exposed electrode 130 at the end of the sheath portion 110 that contains the wiring 120, it is possible to improve the transmission characteristics of an antenna for wireless communication via a lossy medium.

[0086] Note that the above-described embodiment shows an example for realizing the present technology, and the matters in the embodiment and the matters specifying the invention in the claims correspond to each other. Similarly, the matters specifying the invention in the claims and the matters in the embodiment of the present technology having the same name correspond to each other. However, the present technology is not limited to the embodiment, and can be realized by applying various modifications to the embodiment within the scope of the gist thereof.

[0087] The effects described in this specification are merely examples and are not limiting, and other effects may also be present.

[0088] The present technology can also be configured as follows. (1) at least one pair of electrodes; a sheath portion containing wiring that electrically connects each of the at least one pair of electrodes to the corresponding power supply terminal; The minimum diameter of the electrode is greater than the width of the wiring antenna. (2) The distance between the at least one pair of electrodes is greater than the minimum diameter of the electrodes. The antenna described in (1) above. (3) Each of the at least one pair of electrodes is substantially spherical. The antenna according to (1) or (2). (4) Each of the at least one pair of electrodes has a spheroid shape. The antenna according to (1) or (2). (5) Each of the at least one pair of electrodes has a polyhedral shape. The antenna according to (1) or (2). (6) The sheath portion has a columnar shape extending in a direction connecting the at least one pair of electrodes. The antenna according to any one of (1) to (5). (7) The sheath portion has a shape branching from the columnar shape. The antenna according to (6) above. (8) The sheath contains air inside. The antenna according to any one of (1) to (7). (9) The sheath contains pure water inside. The antenna according to any one of (1) to (7). (10) The sheath contains a material having a conductivity of less than 1 S / m. The antenna according to any one of (1) to (7). (11) Each of the at least one pair of electrodes has a coating on its surface. The antenna according to any one of (1) to (10). (12) The magnitude of the impedance at the operating frequency between each of the at least one pair of electrodes and the external medium is smaller than the impedance when the coating is not provided. The antenna according to (11) above. (13) Each of the at least one pair of electrodes contains a material having a conductivity of less than 1 S / m. The antenna according to any one of (1) to (12). (14) Each of the at least one pair of electrodes has a cavity therein. The antenna according to any one of (1) to (13). (15) Each of the at least one pair of electrodes has at least one hole penetrating into the cavity. The antenna according to (14) above. (16) The antenna according to any one of (1) to (15) above, further comprising a transformer in which the number of turns of the coil connected to the power supply terminal is smaller than the number of turns of the other coil. (17) The antenna according to any one of (1) to (15) above, further comprising a switching power amplifier connected to the power supply terminal. [Explanation of symbols]

[0089] 101, 102 Antennas 110 Scabbard part 120 Wiring 130 electrodes 138 Cavity 139 holes 190 Power supply terminal 300 Radio 310 Transmitting circuit 311, 313 power amplifier 312 Transformer 320 receiving circuit 321 LNA (Low Noise Amplifier) 322 Transformer 611, 612 Inductance 621, 622, 631, 632 Resistors 641, 642 Capacitance

Claims

1. At least a pair of electrodes, each of which is substantially spherical, spheroidal, or polyhedral in shape; a sheath portion containing wiring that electrically connects each of the at least one pair of electrodes to the corresponding power supply terminal; The minimum diameter of the electrode is greater than the width of the wiring antenna.

2. The distance between the at least one pair of electrodes is greater than the minimum diameter of the electrodes.

2. The antenna of claim 1.

3. The sheath portion has a columnar shape extending in a direction connecting the at least one pair of electrodes.

2. The antenna of claim 1.

4. The sheath portion has a shape branching from the columnar shape.

4. The antenna of claim 3.

5. The sheath contains air therein.

2. The antenna of claim 1.

6. The sheath contains pure water therein.

2. The antenna of claim 1.

7. The sheath contains a material therein having a conductivity of less than 1 S / m.

2. The antenna of claim 1.

8. Each of the at least one pair of electrodes has a coating on its surface.

2. The antenna of claim 1.

9. The magnitude of the impedance between each of the at least one pair of electrodes and the external medium at the operating frequency is smaller than the impedance without the coating.

9. The antenna of claim 8.

10. Each of the at least one pair of electrodes contains a material therein having a conductivity of less than 1 S / m.

2. The antenna of claim 1.

11. Each of the at least one pair of electrodes has a cavity therein.

2. The antenna of claim 1.

12. Each of the at least one pair of electrodes has at least one hole extending into the cavity. The antenna of claim 11.

13. 2. The antenna according to claim 1, further comprising a transformer in which the number of turns of the coil connected to said power supply terminal is smaller than the number of turns of the other coil.

14. 2. The antenna according to claim 1, further comprising a switching power amplifier connected to said power supply terminal.

15. At least one pair of electrodes; a sheath portion containing wiring that electrically connects each of the at least one pair of electrodes to the corresponding power supply terminal; the minimum diameter of the electrode is greater than the width of the wiring; The sheath portion has a columnar shape extending in a direction connecting the at least one pair of electrodes, and has a shape branching from the columnar shape. antenna.

16. At least one pair of electrodes; a sheath portion containing wiring that electrically connects each of the at least one pair of electrodes to the corresponding power supply terminal; the minimum diameter of the electrode is greater than the width of the wiring; The sheath contains either air or pure water inside. antenna.

17. At least one pair of electrodes; a sheath portion containing wiring that electrically connects each of the at least one pair of electrodes to the corresponding power supply terminal; the minimum diameter of the electrode is greater than the width of the wiring; The sheath contains a material therein having a conductivity of less than 1 S / m. antenna.

Images