Antenna

Abstract

This technology relates to an antenna that enables efficient communication within a conductive medium. The present invention comprises: a current antenna which is formed into a linear shape and through which a current flows; a magnetic current antenna which is arranged in an orientation perpendicular to the current antenna and generates a magnetic current; and an insulator which contains the magnetic current antenna in the interior thereof. A portion of the current antenna is covered with the insulator, and, when the current antenna is installed, another portion thereof is located within the conductive medium. This technology can be used, for example, in antennas for communication devices that are installed in a conductive medium such as seawater.

Description

antenna

[0001] The present technology relates to an antenna, for example, an antenna suitable for use in communication in liquid.

[0002] In recent years, wireless communication such as wireless local area networks (LANs) and contactless communication has become widespread. Patent Document 1 proposes a communication device that communicates with a communication device located far away underwater.

[0003] Japanese Patent Application Laid-Open No. 2010-21874

[0004] It is desirable to be able to perform stable communications even in seawater.

[0005] This technology was developed in light of these circumstances, and enables stable communication even in seawater.

[0006] An antenna according to one aspect of the present technology includes a current antenna formed in a linear shape and through which a current flows, a magnetic current antenna arranged in a direction perpendicular to the current antenna and generating a magnetic current, and an insulator that encloses the magnetic current antenna, wherein a portion of the current antenna is covered by the insulator and the other portion is an antenna that is located within a conductive medium when installed.

[0007] An antenna according to one aspect of the present technology includes a current antenna formed in a linear shape and through which a current flows, a magnetic current antenna arranged in a direction perpendicular to the current antenna and generating a magnetic current, and an insulator that contains the magnetic current antenna, and a portion of the current antenna is covered by the insulator, and the other portion is located within a conductive medium when installed.

[0008] 1 is a diagram illustrating a configuration of an embodiment of a communication system to which the present technology is applied. FIG. 1 is a diagram illustrating a configuration example of a master station. FIG. 2 is a diagram illustrating a configuration example of a slave station. FIG. 3 is a diagram illustrating a configuration example of an antenna. FIG. 4 is a diagram illustrating a configuration example of an electrode. FIG. 5 is a diagram illustrating another configuration example of an antenna. FIG. 6 is a diagram illustrating another configuration example of an antenna. FIG. 7 is a diagram illustrating an equivalent circuit of an antenna. FIG. 8 is a diagram for explaining a coordinate system. FIG. 9 is a diagram illustrating an equivalent circuit of a directional antenna. FIG. 10 is a diagram illustrating another equivalent circuit of a directional antenna. FIG. 11 is a diagram illustrating another equivalent circuit of a directional antenna. FIG. 12 is a diagram illustrating an example configuration of a power feed unit of an antenna. FIG. 13 is a diagram illustrating an example configuration of a power feed unit of an antenna. FIG. 14 is a diagram illustrating another equivalent circuit of a directional antenna. FIG. 15 is a diagram illustrating another equivalent circuit of a directional antenna. FIG. 16 is a diagram illustrating an example configuration of a communication device including a directional antenna. FIG. 17 is a diagram illustrating an installation example of a communication device. FIG. 18 is a diagram for explaining how to use a directional antenna. FIG. 19 is a diagram for explaining how to use when switching directivity.

[0009] Hereinafter, modes for carrying out the present technology (hereinafter referred to as embodiments) will be described.

[0010] <Configuration of communication system> Fig. 1 is a diagram showing the configuration of one embodiment of a communication system 1 to which the present technology is applied. The communication system 1 shown in Fig. 1 includes a master station 11, a communication station 12, a communication station 13, a satellite 14, slave stations 21-1 to 21-6, slave stations 31-1 and 31-2, and a repeater 32. In the following description, when there is no need to distinguish between the slave stations 21-1 to 21-6, they will be simply referred to as slave stations 21. The same applies to other parts.

[0011] The master station 11 and the communication station 12 communicate using, for example, local 5G. The master station 11 and the communication station 13 communicate using, for example, LPWA (Low Power Wide Area). The master station 11 is configured to be able to acquire location information from a satellite 14 using, for example, GNSS (Global Navigation Satellite System). Here, the explanation will be continued using local 5G, LPWA, and GNSS as examples, but it is also possible to configure the communication to be performed using other communication networks, for example, WLAN (Wireless Local Area Network) or a satellite communication network.

[0012] The master station 11 also communicates with the slave station 21. The part of the master station 11 that communicates with the communication stations 12, 13, and satellite 14 is located in the air, while the part that communicates with the slave station 21 is located in seawater. The slave station 21 is located in seawater.

[0013] Although the following description will be given taking the case where the environment in which the communication system 1 is installed as the ocean as an example, the communication system 1 can also be installed in environments such as lakes, ponds, rivers, and aquariums. The present technology described below can be applied to devices installed in a medium (lossy medium) other than lossless air. Lossy media include the inside of the human body as well as the above-mentioned seawater and brackish lakes.

[0014] Here, one of the base stations 11 is described as being located in the air (gas) and the other in seawater (liquid), but one of the base stations 11 may be located on the seabed (solid) or in a vacuum.

[0015] The configuration of the communication system 1 shown in Fig. 1 is an example and is not intended to be limiting. In the communication system 1 shown in Fig. 1, the master station 11 communicates with the communication stations 12, 13, and 14, but the master station 11 may also have the function of communicating with other stations, or may be configured to communicate with only one or two of these stations rather than all of them. The master station 11 may also be configured to only have the function of communicating with the slave stations 21, in other words, not have the function of communicating with the communication stations 12, 13, or 14.

[0016] Each of the slave stations 21-1 to 21-6 communicates with the master station 11. A so-called ad hoc network may be configured in which the slave stations 21 communicate with each other. The slave stations 21 are equipped with, for example, a sensor for sensing underwater and transmit the sensed data to the master station 11. The slave stations 21 may be configured to have only a transmission function for transmitting data to the master station 11, or may be configured to have both a transmission function and a reception function for transmitting and receiving data to and from the master station 11 and other slave stations 21. The slave stations 21 are installed at depths from the sea surface within a range of, for example, 0 to 10 m.

[0017] Each of the slave stations 31-1 to 31-2 communicates with a repeater 32. The slave station 31 is equipped with, for example, a sensor for sensing underwater conditions and transmits the sensed data to the repeater 32. The slave station 31 can be configured to have only a transmission function for transmitting data to the repeater 32, or can be configured to have both a transmission function and a reception function for transmitting and receiving data to and from the repeater 32 and other slave stations 31. The slave station 31 is installed on the seabed (or near the seabed).

[0018] The repeater 32 and the master station 11 may be configured to communicate by wire or by optical communication.

[0019] The paths along which signals from a substation 21 installed underwater are transmitted to the master station 11 include a direct wave that travels in a straight line between the antenna of the substation 21 and the antenna of the master station 11, and a lateral wave that travels vertically upward from the antenna of the substation 21 to the sea surface directly above it, emerges at the sea surface, travels along the sea surface, and travels from the sea surface directly above the antenna of the master station 11 to the antenna of the master station 11.

[0020] When the attenuation of the lateral waves is smaller than that of the direct waves, the lateral waves become dominant and are received by the master station 11. Since the lateral waves propagate farther than the direct waves, the greater the distance between the slave station 21 and the master station 11, the more dominant the lateral waves become. This phenomenon occurs when the antenna is not far above the sea surface.

[0021] The paths along which a signal from a substation 31 installed on the seabed propagates to the repeater 32 include a direct wave that travels in a straight line between the antenna of the substation 31 and the antenna of the repeater 32, and a signal that travels vertically downward from the antenna of the substation 31 to the seabed directly below it, travels along the seabed, and then travels from the seabed near the antenna of the repeater 32 to the antenna of the repeater 32.

[0022] Signals propagating from the slave station 31 into seawater are attenuated significantly, but signals propagating from the slave station 31 along the seabed are attenuated only slightly, so the repeater 32 receives the signals propagating along the seabed. Signals propagating along the seabed allow the network to be expanded over a wider area. Power consumption by the slave station 31 can be reduced. When a mesh network is formed using the slave stations 31, the number of terminals required for the mesh network can be reduced.

[0023] <Configuration Example of Master Station> Fig. 2 is a diagram showing a configuration example of the master station 11. The master station 11 shown in Fig. 2 includes a signal processing unit 101, a high frequency processing unit 102, and an antenna 103. The antenna 103 of the master station 11 is installed in seawater (in liquid) and is used for communication with the slave stations 21, repeaters 32, and other master stations 11 that are also installed in seawater. The antenna 103 has a structure that will be described later with reference to Fig. 4.

[0024] A signal from the slave station 21 is received by the antenna 103 of the master station 11 and supplied to the high frequency processing unit 102. The high frequency processing unit 102 is configured to process, for example, the received signal and the signal to be transmitted. The operating frequency fw of the high frequency processing unit 102 is set to, for example, 1 MHz or less.

[0025] The signal processed by the high frequency processing section 102 is supplied to the signal processing section 101. The signal processing section 101 performs processing such as temporarily storing the signal processed by the high frequency processing section 102 and processing and transmitting a received signal.

[0026] The configuration of the master station 11 shown in Fig. 2 can also be applied as the configuration of the repeater 32. When the configuration shown in Fig. 2 is the configuration of the repeater 32, the antenna 103 has a function of receiving a signal from the slave station 31 and a function of transmitting a signal to the master station 11 or another repeater 32. The high frequency processing unit 102 and the signal processing unit 101 have a function of amplifying and transmitting the received signal.

[0027] 3 is a diagram showing an example of the configuration of the slave station 21. The slave station 21 includes a sensing unit 201, a baseband processing unit 202, a high frequency processing unit 203, and an antenna 204.

[0028] The slave station 21 can be a mobile station such as an underwater drone or robot that is placed underwater. The slave station 21 has a sensing unit 201 that includes, for example, a sensor for observing water temperature, tidal currents, and the like, an image sensor, and the like, and can be installed at a specific location.

[0029] The data sensed by the sensing unit 201 is supplied to the baseband processing unit 202. The baseband processing unit 202 converts the supplied data into a baseband signal, performs necessary processing on the baseband signal, and supplies the baseband signal to the high-frequency processing unit 203. The high-frequency processing unit 203 operates at, for example, an operating frequency fw, converts the signal to a signal of frequency fw, and transmits the signal from the antenna 204 to the master station 11.

[0030] The high frequency processing section 203 is configured to process a received signal, or to process a received signal and a signal to be transmitted. The operating frequency fw of the high frequency processing section 203 is set to, for example, 1 MHz or less.

[0031] The slave station 21 may be configured to transmit and receive signals to and from the master station 11, or may be configured to transmit data to the master station 11. The antenna 204 of the slave station 21 may have a function to connect to the master station 11 so as to transmit and receive data to and from the master station 11. The antenna 204 is a linearly polarized antenna or a circularly polarized antenna, as will be described later with reference to Figure 4 and subsequent figures. Signal transmission from the slave station 21 may be intermittent transmission.

[0032] <Antenna Configuration> The antenna 103 of the master station 11 and the antenna 204 of the slave station 21 can be antennas having a configuration as shown in Fig. 4. Here, the explanation will be continued using the antenna 204 of the slave station 21 as an example, but the same can also be applied to the antenna 103 of the master station 11.

[0033] The antenna 204 is composed of a magnetic current antenna 301 and a current antenna 302. The magnetic current antenna 301 is formed of, for example, a solenoid coil. The entire magnetic current antenna 301 is enclosed in an insulator 303.

[0034] It is assumed that the antenna 204 will be installed in a conductive medium such as underwater. If there is a medium near the electric wire, the magnetic current antenna 301 may experience loss due to induced current. When installed in a conductive medium, the entire magnetic current antenna 301 is covered with an insulator 303 to prevent the magnetic current antenna 301 from coming into contact with the conductive medium.

[0035] The current antenna 302 is disposed so as to pass through the center of the magnetic current antenna 301. The current antenna 302 is formed of, for example, a dipole antenna. The portion of the current antenna 302 located inside the magnetic current antenna 301 is enclosed in an insulator 303.

[0036] The inside of the current antenna 302, in other words, approximately half of the entire current antenna 302, is covered with an insulator 303. When the antenna 204 is placed underwater (in a conductive medium), both ends of the electrodes of the current antenna 302 are exposed to the water (in a conductive medium). If the portion of the insulator 303 covering the current antenna 302 is short, loss occurs due to coupling between the exposed electrodes, which may reduce efficiency, so the configuration is such that approximately half of the current antenna is covered with the insulator 303.

[0037] The current antenna 302 is formed in a linear shape and serves as an antenna element for passing a current, and the magnetic current antenna 301 is provided as an antenna for generating a magnetic current in a direction perpendicular to the current element. The power supply part of the current antenna 302 is provided in the center of the magnetic current antenna 301, as shown in the left figure.

[0038] The left diagram in Fig. 4 is an enlarged view of the central portion of antenna 204, showing the portion where magnetic current antenna 301 and current antenna 302 are connected. Electrodes 311 and 312 of current antenna 302 are located in the central portion of antenna 204. Electrode 311 is connected to one end of magnetic current antenna 301, and electrode 312 is connected to the other end of magnetic current antenna 301. A portion of current antenna 302 centered on the power feed point (between electrodes 311 and 312) is covered with insulator 303, and the remaining portion is exposed to the conductive medium.

[0039] In the following explanation, we will continue with an example of a coordinate system such as that shown in the left diagram of Fig. 4. The direction in which current antenna 302 is arranged is defined as the Y axis, the direction in which the linear portion of magnetic current antenna 301 is arranged and intersects with the Y axis at 90 degrees is defined as the X axis, and the direction perpendicular to the plane in which the X axis and Y axis are located is defined as the Z axis.

[0040] The electrodes 311 and 312 are connected to a chip (not shown), for example, an RFIC (Radio Frequency Integrated Circuit).

[0041] While a portion of the current antenna 302 is exposed to the conductive medium, the magnetic current antenna 301 is entirely covered by the insulator 303, in other words, the magnetic current antenna 301 is completely enclosed in the insulator 303. The antenna 204 is made up of the magnetic current antenna 301, the current antenna 302, and the insulator 303 that covers them.

[0042] The insulator 303 can be made of a low-conductivity material such as pure water, a resin material, or air. The insulator 303 may be made of a plurality of materials. For example, the insulator 303 may be made of a resin housing filled with pure water, air, insulating oil, or the like, and the entire magnetic current antenna 301 and a part of the current antenna 302 may be enclosed in the housing.

[0043] The magnetic current antenna 301 is formed of a coil such as a solenoid coil. This coil can have a total length of wire that is equal to or less than 1 / 8 of the effective wavelength of the electromagnetic wave in the insulator 303. If the total length of the wire is equal to or more than 1 / 8 of the effective wavelength, the size of the antenna 204 may become large, which may cause the antenna 204 to malfunction. Therefore, the coil is designed to have a size equal to or less than the wavelength so that such inconvenience does not occur.

[0044] If it is desired to strengthen the magnetic current of the magnetic current antenna 301, the coil core may be made of ferrite.

[0045] The electrode of the current antenna 302 exposed outside the insulator 303 may be formed as a sphere, as shown in Fig. 5. In the example shown in Fig. 5, the end of the current antenna 302 on the left side in the figure is formed as a spherical electrode 331-1, and the end of the current antenna 302 on the right side in the figure is formed as a spherical electrode 331-2. A configuration in which the end of the current antenna 302 is formed from such a sphere is also possible.

[0046] In Fig. 4, the coil shape of the magnetic current antenna 301 is explained as being circular (cylindrical), but it may be rectangular (rectangular parallelepiped) as shown in Fig. 6. The magnetic current antenna 301 shown in Fig. 6 is formed of a rectangular coil, and a space is provided in the center of the coil, in which the current antenna 302 is disposed.

[0047] The magnetic current antenna 301 is divided into two parts at the position where the current antenna 302 is disposed, and may be an antenna formed in the shape of a rectangular parallelepiped.

[0048] Although antenna 204 shown in Fig. 4 is a linearly polarized antenna, it can also be a circularly polarized antenna by using a configuration as shown in Fig. 7. Circularly polarized antenna 204 shown in Fig. 7 is configured such that antennas 204-1 and 204-2, which have the same configuration as antenna 204 shown in Fig. 4, are arranged so that they intersect at right angles. Antenna 204-1 is configured from magnetic current antenna 301-1 and current antenna 302-1, and antenna 204-2 is configured from magnetic current antenna 301-2 and current antenna 302-2.

[0049] Magnetic current antenna 301-1 of antenna 204-1 and magnetic current antenna 301-2 of antenna 204-2 are coils of the same shape that intersect at right angles, but because there is a possibility that they may interfere with each other, magnetic current antenna 301-1 and magnetic current antenna 301-2 are configured to have different diameters, numbers of turns, lengths, etc., and are adjusted to prevent interference between antennas 204-1 and 204-2. In this way, interference may be prevented by changing the diameter of the coil of magnetic current antenna 301, or by slightly shifting the axis.

[0050] <Antenna Equivalent Circuit> Figure 8 shows the equivalent circuit of the antenna 204. The equivalent circuit of the magnetic current antenna 301 is represented by a series connection of a resistor Resr and an inductor Lm. The current antenna 302 can be configured as a half-sheath dipole antenna (HSDA), and the equivalent circuit of the HSDA is represented by a parallel connection of a resistor Re / 2 and a capacitor 2Ce, and a series connection of a resistor Rr / 2 and an inductor Le / 2.

[0051] Let N be the number of turns of the solenoid coil (magnetic current antenna 301), S be the cross-sectional area, le be the equivalent length of the half-sheath antenna, Im be the value of the current flowing through magnetic current antenna 301, and Ie be the value of the current flowing through current antenna 302. In the equivalent circuit shown in Figure 8 (used as symbols), Re and Ce are the resistance and capacitance due to seawater in the half-sheath antenna, respectively, and Le and Rr represent the inductance and resistance of the conductor.

[0052] Although the explanation will continue using the example of resistance and capacitance due to seawater, the resistance and capacitance used are those due to a conductive medium depending on the installation location of the antenna 204 (the equipment in which the antenna 204 is installed).

[0053] <Conditions for a Directional Antenna> The following describes the conditions for using the antenna 204 shown in FIG. 4, which is represented by the equivalent circuit shown in FIG. 8, as a directional antenna, and the configuration of the antenna 204 that satisfies those conditions.

[0054] We define three-dimensional coordinate systems as shown in Figures 9A and 9B. Point wave sources due to electric current and magnetic current are referred to as Electric Hertzian Dipole (EHD) and Magnetic Hertzian Dipole (MHD), respectively. The amplitude J of EHD is defined as J = I x l, assuming that current I flows over an infinitesimal length l, and the amplitude M of MHD is defined as M = Im x S (magnetic moment), assuming that current Im flows through a closed circuit with area S.

[0055] As shown in Figures 9A and 9B, when EHD and MHD with angular frequency ω and amplitudes J and M exist in the z direction, the electric fields Ee and Em and the magnetic fields He and Hm at point P can be expressed in a three-dimensional polar coordinate system as shown in the following equations (1) to (6).

[0056]

[0057] Here, γ is a propagation constant and can be expressed by the following equation (7).

[0058] As an approximation of the propagation coefficient γ, tan δ >> 1 holds in a conductive medium. From these equations, we can see that the far field (the 1 / r term) that contributes to radiation consists of only the θ and φ components for both EHD and MHD, and that the polarizations are orthogonal to each other. Therefore, if two wave sources are appropriately combined under the condition that one wave source vector is orthogonal to the other, they will reinforce each other in a specific direction, giving it directionality.

[0059] To derive specific conditions, we assume that EHD is oriented in the z-axis direction as shown in A of Figure 9, and that MHD is oriented in the x-axis direction as shown in B of Figure 9, rotated 90 degrees around the y-axis. In this case, the electromagnetic field in the +y-axis direction is expressed by the following equations (8) and (9). Furthermore, the electromagnetic field in the -y-axis direction has the MHD-induced terms reversed and is expressed by the following equations (10) and (11).

[0060]

[0061] When the condition M=J / γ is satisfied, the electromagnetic field in the far field in the -y-axis direction becomes zero, and the gain in the +y-axis direction increases by 6 dB, so it can be seen that it functions as a unidirectional antenna.

[0062] Even when the antenna 204 is installed underwater (in a conductive medium), a directional antenna can be realized by satisfying the condition M=J / γ, as described above. When taking into consideration that the antenna 204 is installed in a conductive medium, a directional antenna can be realized if the following equation (12) is further satisfied.

[0063]

[0064] Equation (12) is satisfied when the amplitude ratio (ωμσ) of the EHD amplitude M to the EHD amplitude J is －１／２It can be seen that it is sufficient to excite the antenna with a phase difference of -45 degrees. The following description will be given assuming that excitation with a phase difference of -45 degrees results in downward directivity. When excitation is performed with a phase difference of +135 degrees, the antenna 204 can be used as a directional antenna with upward directivity. In the following description, the case of excitation with a phase difference of -45 degrees (when the antenna 204 is used as a downward directional antenna) will be taken as an example.

[0065] Although the explanation will continue using 45 degrees and 135 degrees as examples, an appropriate phase difference other than 45 degrees or 135 degrees can be set depending on the environment in which the antenna 204 is installed, such as water temperature, depth, and salinity. Taking into account errors and other factors, any phase difference between 35 degrees and 55 degrees or between 125 degrees and 145 degrees, with 45 degrees and 135 degrees as the center values, falls within the applicable range of the present technology, and the antenna 204 having directionality can be realized. The present technology can realize the antenna 204 having directionality by designing the voltage applied to the magnetic current antenna 301 to be 35 degrees to 55 degrees ahead of the voltage applied to the current antenna 302, or 125 degrees to 145 degrees behind the voltage applied to the current antenna 302.

[0066] As described above, the equivalent circuit of the antenna 204 having the configuration shown in Fig. 4 is as shown in Fig. 8. Referring again to Fig. 8, a specific method for realizing the case where the antenna 204 is excited with a phase difference of -45 degrees will be described.

[0067] If the number of turns of the solenoid coil (magnetic current antenna 301) is N, the cross-sectional area is S, and the equivalent length of the half-sheath antenna is le, then the value of the current flowing through magnetic current antenna 301 is Im, and the value of the current flowing through current antenna 302 is Ie. In this case, the MHD amplitude is expressed as M = N × S × Im and the EHD amplitude J = le × Ie. By substituting these values ​​into equation (12), it can be seen that the following equation (13) is satisfied, and it is sufficient to design Im so that it lags behind Ie by 45 degrees (-45 degrees).

[0068]

[0069] <First Antenna Configuration> When the design is such that equation (13) is satisfied and Im lags Ie by 45 degrees (−45 degrees), the circuit configuration shown in FIG. 10 can be considered (this is the first configuration of the antenna 204).

[0070] As shown in Figure 10, the magnetic current antenna 301 and the current antenna 302 are configured to be fed separately, with appropriate amplitude ratios and phase differences created by digital signal processing. The RFIC connected to the antenna 24 has two outputs, and the phase difference is digitally applied. In the circuit configuration shown in Figure 10, a current Im delayed by -45 degrees is supplied to the magnetic current antenna 301, and a current Ie delayed by 0 degrees is supplied to the current antenna 302. For example, if the voltage on the magnetic current antenna 301 side is advanced by 45 degrees, the current will flow with a delay of 45 degrees.

[0071] The amplitude ratio can also be configured to be digitally adjusted, and the amplifier gain can also be configured to be adjusted.

[0072] <Second Configuration of Antenna> FIG. 11 is a diagram showing a second configuration example of the antenna 204 when it is designed to have directivity.

[0073] Considering that the impedance of current antenna 302 is approximately on the real axis in the first quadrant of the complex plane and the impedance of magnetic current antenna 301 is approximately on the imaginary axis in the first quadrant, as in the circuit configuration shown in Figure 11, in the case of a single power supply circuit where the power supply part is only branch wiring to two antennas, positive and negative, the current Im flowing in magnetic current antenna 301 lags behind the current Ie flowing in current antenna 302 by 90 degrees.

[0074] One possible method for achieving a 45-degree phase difference delay is to use a capacitor to advance the current Im on the magnetic current antenna 301 side by 45 degrees. In the second configuration example of the antenna 204 shown in Figure 11, capacitors Cc-1 and Cc-2 are provided in the magnetic current antenna 301. The configuration is such that capacitor Cc-1, resistor Resr, inductor Lm, and capacitor Cc-2 are connected in series between the portion corresponding to electrode 311 and the portion corresponding to electrode 312.

[0075] The configuration of the antenna 204 shown in Figure 11 is such that the magnetic current antenna 301 and the current antenna 302 are fed in parallel, and two capacitors Cc for shifting the phase are arranged in series on the magnetic current antenna 301 side of the connection point (electrodes 311 and 312) between the feed point of the magnetic current antenna 301 and the feed point of the current antenna 302, and are positioned symmetrically from the feed point.

[0076] The element value of the capacitor Cc is determined as follows.

[0077] In step S1, the characteristics of the current antenna 302, which serves as a current source, are extracted. The extracted characteristics are, for example, impedance Re+jωLe. This impedance can be calculated using a predetermined proposed formula or by simulation.

[0078] In step S2, the diameter, length, number of turns, etc. of the coil constituting the magnetic current antenna 301 are determined. The loop area S and length lm are found from the desired size of the magnetic current antenna 301, and the conditions for achieving the desired ESR (equivalent series resistance) are derived using techniques such as design formulas and parametric analysis using simulations.

[0079] In step S3, the element value of the capacitor Cc is determined by the following equation (14).

[0080]

[0081] By providing a capacitor Cc having the element value obtained in this manner in the magnetic current antenna 301, an antenna 204 can be constructed that achieves a 45-degree phase difference delay, making the antenna 204 directional.

[0082] <Third Configuration of Antenna> FIG. 12 is a diagram showing a third configuration example of the antenna 204 when designed to have directivity.

[0083] The third configuration example of the antenna 204 shown in Fig. 12 is a configuration in which an inductor Lc is added to the second configuration example of the antenna 204 shown in Fig. 11. In the third configuration example of the antenna 204 shown in Fig. 12, an inductor Lc-1 and an inductor Lc-2 are provided in the current antenna 302. The inductor Lc-1 is provided between the current antenna 302 and the capacitor Cc-1 of the magnetic current antenna 301, and the inductor Lc-2 is provided between the current antenna 302 and the capacitor Cc-2 of the magnetic current antenna 301.

[0084] The configuration of the antenna 204 shown in Figure 12 is such that the magnetic current antenna 301 and the current antenna 302 are fed in parallel, and two inductors Lc for shifting the phase are arranged in series at positions symmetrical to the feed point on the current antenna 302 side of the connection point (electrodes 311 and 312) between the feed point of the magnetic current antenna 301 and the feed point of the current antenna 302.

[0085] 12 shows a configuration including capacitor Cc, but it is also possible to adopt a configuration in which capacitor Cc is omitted. Another method for realizing a 45-degree phase difference delay is to delay the current on the current antenna 302 side by 45 degrees using inductor Lc, and such a configuration is also possible.

[0086] 12, the case where a capacitor Cc is provided is taken as an example for explanation, but providing the capacitor Cc in this way makes the design easier and increases the degree of freedom in the design. For example, if the antenna 204 is configured to include only the inductor Lc without the capacitor Cc, it is possible to obtain the antenna 204 with a phase difference of -45 degrees by adjusting the inductor of the magnetic current antenna 301, the number of turns of the coil, the cross-sectional area of ​​the coil, etc., but these adjustments may be difficult depending on the design conditions.

[0087] By providing the capacitor Cc, it becomes possible to design the antenna 204 in a design process in which, for example, after designing the number of coil turns and cross-sectional area sufficient to generate a desired magnetic current, the element value of the capacitor Cc is determined in accordance with the resulting inductance of the magnetic current antenna 301. Therefore, by providing the capacitor Cc, the design becomes easier and the degree of freedom in the design can be increased, and here, the design of such an antenna 204 will be explained.

[0088] The element values ​​of the capacitor Cc and the inductor Lc are determined as follows.

[0089] In step S11, the characteristic of the current antenna 302, which serves as a current source, is extracted. The extracted characteristic is, for example, impedance Re+jωLe. This impedance can be calculated using a predetermined proposed formula or by simulation.

[0090] In step S12, the element value of the current-side inductor Lc is determined. The inductor Lc can be calculated using the following equation (15).

[0091]

[0092] In step S13, the diameter, length, and number of turns of the coil of the magnetic current antenna 301 are determined so as to satisfy the following equation (16). In this case, the magnetic current antenna 301 is a solenoid coil, and the shape of the solenoid coil (loop shape and number of turns) is determined. In addition, the inductor of the magnetic current source coil is determined, for example, by simulation.

[0093]

[0094] In step S14, the reactance on the magnetic current antenna 301 side is adjusted by adjusting the element value of the capacitor Cc. The element value of the capacitor Cc is determined so as to satisfy the above formula (16). The capacitor Cc that satisfies the above formula (16) is calculated based on the following formula (17).

[0095]

[0096] In equation (17), if the solenoid coil is designed to the desired design value, the denominator of equation (17) will be zero, and therefore the step of setting the element value of capacitor Cc in step S14 does not need to be performed. In such a case, antenna 204 is configured without capacitor Cc.

[0097] In step S15, a capacitor for compensating the imaginary part is added to the input section as needed, and the value of the capacitor for compensating the imaginary part is set based on the imaginary part of the overall impedance.

[0098] By providing the capacitor Cc and inductor Lc having the element values ​​obtained in this manner in the magnetic current antenna 301 and the current antenna 302, it is possible to construct an antenna 204 that achieves a 45-degree phase difference delay, and to make the antenna 204 directional.

[0099] <Configuration of Power Supply Unit> An additional description will be given of the configuration of antenna 204 having the equivalent circuit described with reference to Fig. 12, particularly the configuration of the electrode portion (power supply unit). Fig. 13 is a diagram showing an example of the configuration of antenna 204 corresponding to the equivalent circuit shown in Fig. 12.

[0100] The antenna 204 shown in FIG. 13 (referred to as antenna 204b) differs from the antenna 204 shown in FIG. 4 (referred to as antenna 204a) in that it has a configuration in which a capacitor Cc and an inductor Lc are added, but is otherwise similar.

[0101] Referring to the enlarged view of the power supply section shown in the left diagram of Figure 13, a capacitor Cc-1 is connected between the electrode 311b and the magnetic current antenna 301b, and an inductor Lc-1 is connected between the electrode 311b and the current antenna 302b.

[0102] Similarly, a capacitor Cc-2 is connected between the electrode 312b and the magnetic current antenna 301b, and an inductor Lc-2 is connected between the electrode 312b and the current antenna 302b.

[0103] The inductor Lc may be an electronic component such as a wire-wound inductor or a coil made of wiring material, and the capacitor Cc may be an electronic component such as a multilayer ceramic capacitor, a film capacitor, or a variable capacitor.

[0104] 13 shows an example in which a power supply section is provided in the center of antenna 204b, and a capacitor Cc and an inductor Lc are provided in the power supply section. However, a configuration in which a power supply section is provided in a section other than the center of antenna 204b, and a capacitor Cc and an inductor Lc are provided in the power supply section, may also be used.

[0105] 14 is a diagram showing another example of the configuration of the antenna 204. The current antenna 302 is arranged so as to pass through the center of the coil of the magnetic current antenna 301, but has wiring that bends 90 degrees downward in the center and extends to the outside of the coil. The coil of the magnetic current antenna 301 is also configured so that its end is provided below the center in the figure.

[0106] A capacitor Cc-1 is connected between an electrode 311c provided outside the coil and an end of the magnetic current antenna 301c, and an inductor Lc-1 is connected between the electrode 311c and the current antenna 302c. A capacitor Cc-2 is connected between an electrode 312c provided outside the coil and the magnetic current antenna 301c, and an inductor Lc-2 is connected between the electrode 312c and the current antenna 302c.

[0107] In this way, the antenna 204 can be configured to include the capacitor Cc and the inductor Lc, and by configuring it in this way, it can be made into a directional antenna having directivity in a predetermined direction.

[0108] <Directivity Reversal Function> As described above, the antenna 204 can be made to function as a directional antenna. When the antenna 204 functions as a directional antenna, the current of the magnetic current antenna 301 can be driven with a phase difference of 45 degrees relative to the current of the current antenna 302 to have, for example, downward directivity, and the current of the magnetic current antenna 301 can be driven with a phase difference of 135 degrees to have, for example, upward directivity.

[0109] As shown in Figures 15 and 16, a switch can be provided on the antenna 204 so that the directivity can be switched between 45 degrees delay and 135 degrees advance by switching the switch, thereby allowing the directivity to be switched downward or upward.

[0110] Fig. 15 is a diagram showing an example of the configuration of the antenna 204 in which a switch 401 is provided in the antenna 204 having the circuit configuration shown in Fig. 10. The switch 401 is provided in the magnetic current antenna 301. Although not shown, the switch 401 may be provided on the current antenna 302 side. The switch 401 can be formed of, for example, an RF switch.

[0111] By providing switch 401, the positive and negative polarities of the wires can be swapped. When switch 401 is open, the antenna lags by 45 degrees, and when switch 401 is closed, the positive and negative polarities of the wires are swapped, resulting in a 135-degree lead. Therefore, by turning switch 401 on and off, the antenna can be switched from a downward to an upward direction. Furthermore, by disconnecting switch 401, the antenna can be operated as an omnidirectional positive electric dipole antenna.

[0112] Fig. 16 is a diagram showing an example of the configuration of the antenna 204 in which a switch 402 is provided in the antenna 204 having the circuit configuration shown in Fig. 12. The switch 402 is provided between the magnetic current antenna 301 and the current antenna 302. The switch 402 can be formed of, for example, an RF switch.

[0113] When switch 402 is open, the beam lags by 45 degrees, and when switch 402 is closed, the positive and negative wires are reversed, resulting in a 135-degree lead. Therefore, by turning switch 402 on and off, the beam direction can be switched downward or upward.

[0114] In this way, a configuration having a switch for switching the direction of directivity may be adopted.

[0115] 17 is a diagram showing an example of the configuration of a slave station 21 (communication device) equipped with an antenna 204. The slave station 21 includes the antenna 204 and a pressure-resistant container 451 that is mounted (enclosed) with, for example, an IC chip that includes a sensor unit, a power supply unit, a control unit, a calculation unit, etc. The pressure-resistant container 51 may be configured as an integrated unit with the insulator 303 of the antenna 204.

[0116] If the antenna 204 has directionality, a weight 452 is attached to the pressure-resistant container 451 so that the direction of the antenna 204 is directed in a desired direction when the slave station 21 is installed. By attaching the weight 452, the center of gravity is shifted downward by the weight 452, and the antenna 204 can be naturally oriented so that the directionality is directed downward.

[0117] 18, the slave stations 21 are installed underwater. The slave stations 21-1 and 21-2 are installed as stationary devices on the seabed, and are devices that observe environmental data such as water temperature, conductivity, depth, illuminance, turbidity, pH, and CO2 concentration in the sea, and transmit and receive the data wirelessly.

[0118] For example, the slave stations 21-1 and 21-2 have directivity in the downward direction, that is, in this case, toward the seabed, and communicate via the seabed. The ability of the slave stations 21-1 and 21-2 to communicate with each other with directivity allows them to actively use lateral waves for communication, thereby increasing signal strength.

[0119] The slave station 21-3 is a floating communication device that is moored via ballast. The slave station 21-3 can also function as, for example, a repeater 32 (FIG. 1). The slave station 21-3 also has directivity, so that it can point its direction in the direction of the communication partner, enabling efficient communication.

[0120] The slave station 21-4 is a communication device mounted on an underwater drone 471. The underwater drone 471 may be an ROV (Remotely Operated Vehicle) or an AUV (Autonomous Underwater Vehicle). The slave station 21-4 can be used, for example, as a device for inspecting and maintaining other slave stations 21. In this case, when communicating with a slave station 21, the direction of orientation is directed in the direction of the communication partner, enabling efficient communication.

[0121] The slave station 21-5 is a buoy-shaped communication device whose housing floats on the sea surface. The slave station 21-5 can function as the master station 11 (FIG. 1), for example, as an underwater base station that connects the slave station 21-1 installed on the seabed with land, sea, and space wireless networks.

[0122] By installing the slave station 21-5 on the seabed, i.e., with its direction of direction facing downward, it is possible to efficiently communicate with the slave station 21-1 and the slave station 21-4 installed underwater. Furthermore, since the slave station 21-5 (master station 11) can be prevented from emitting radio waves over the ocean, even if it is designed to emit strong radio waves in its direction of direction, it is possible to reduce radio waves leaking over the ocean, thereby strengthening radio waves into the ocean without violating the laws governing propagation in the air. Therefore, the slave station 21-5 can be used in shallow waters. It is also possible to reduce interference with land-based wireless systems and improve the efficiency of frequency resource utilization.

[0123] 19, by directing the directivity of the antenna 204 (communication device equipped with the antenna 204) installed underwater toward the seabed, it is possible to suppress radio waves leaking onto the surface of the sea while improving the communication performance of undersea propagation. Power efficiency can also be improved by the amount of radio waves that are reduced in unnecessary directions.

[0124] In the above description, the antenna 204 has been described as having directivity in the downward or upward direction, but it is also possible to provide directivity in the horizontal direction (leftward or rightward, for example) by installing the antenna 204 so that it has directivity in the horizontal direction. In other words, by using the directional antenna 204, it becomes possible to communicate efficiently with only a specific party, even in a conductive medium such as water.

[0125] Consider a situation in which a communication device equipped with antenna 204-11, a communication device equipped with antenna 204-12 on the left side of the figure, and a communication device equipped with antenna 204-13 on the right side of the figure are present within a conductive medium as shown in Figure 20. For example, antenna 204-11 can be set to operate in an omnidirectional standby state, and after receiving a communication request signal, to point its directivity in the direction of the intended communication partner and begin communication.

[0126] For example, when a communication request signal is received from a communication device equipped with antenna 204-12 located on the left side of the figure, antenna 204-11 turns its directivity to the left and starts communication with antenna 204-12. Also, when a communication request signal is received from a communication device equipped with antenna 204-13 located on the right side of the figure, antenna 204-11 turns its directivity to the right and starts communication with antenna 204-13.

[0127] In addition, when communication is performed after switching the directivity in the direction of the communication partner, the direction of the communication partner is either known (pre-set) or is identified after installation using some method.

[0128] By using the directional antenna 204, one-to-one communication can be performed efficiently. In the case of one-to-one communication where the communication target is fixed, it is possible to improve communication quality by directing the directivity in a specific direction. It is also possible to achieve low power consumption while maintaining communication quality.

[0129] According to the present technology, it is possible to realize an antenna that can perform good communication in a conductive medium such as underwater. According to the present technology, it is possible to perform communication with directionality in a conductive medium.

[0130] In this specification, a system refers to an entire device made up of multiple devices.

[0131] The effects described in this specification are merely examples and are not limiting, and other effects may also be present.

[0132] It should be noted that the embodiments of the present technology are not limited to the above-described embodiments, and various modifications are possible within the scope of the present technology.

[0133] The present technology can also be configured as follows. (1) An antenna comprising: a current antenna formed in a linear shape and through which a current flows; a magnetic current antenna arranged in a direction perpendicular to the current antenna and generating a magnetic current; and an insulator enclosing the magnetic current antenna, wherein a portion of the current antenna is covered by the insulator and the other portion is located within a conductive medium when installed. (2) The antenna described in (1), in which spherical electrodes are provided on both ends of the current antenna. (3) The antenna described in (1) or (2), in which the magnetic current antenna includes a coil whose total length of electric wire is equal to or less than 1 / 8 of the effective wavelength of the electromagnetic wave in the insulator. (4) The antenna described in (3), in which ferrite is provided as a core of the coil. (5) The antenna described in any of (1) to (4), in which the current antenna and the magnetic current antenna are connected via a capacitor. (6) The antenna according to (5), wherein power is supplied to the current antenna and the magnetic current antenna in parallel, and the capacitor is provided in series on the magnetic current antenna side of the portion where the current antenna and the magnetic current antenna are connected, at a position symmetrical with respect to the power supply point. (7) The antenna according to any of (1) to (4), wherein the current antenna and the magnetic current antenna are connected via an inductor. (8) The antenna according to (7), wherein power is supplied to the current antenna and the magnetic current antenna in parallel, and the inductor is provided in series on the current antenna side of the portion where the current antenna and the magnetic current antenna are connected, at a position symmetrical with respect to the power supply point. (9) The antenna according to any of (1) to (4), wherein the current antenna and the magnetic current antenna are connected via a capacitor and an inductor. (10) The antenna described in (9), wherein power is supplied to the electric current antenna and the magnetic current antenna in parallel, the capacitor is provided in series on the magnetic current antenna side of the portion where the electric current antenna and the magnetic current antenna are connected, at a position symmetrical with respect to the power supply point, and the inductor is provided in series on the electric current antenna side, at a position symmetrical with respect to the power supply point.(11) The antenna according to any one of (1) to (10), wherein the current antenna and the magnetic current antenna are arranged so that the centers of their respective wave sources are approximately aligned, wherein an amplitude J of the current source and an amplitude M of the magnetic current source have a relationship where J:M = a propagation coefficient γ:1, and wherein the phase of the magnetic current source is excited with a phase difference lag of 35 degrees to 55 degrees or a phase difference lead of 125 degrees to 145 degrees relative to the current source. (12) The antenna according to (11), wherein the phase difference is generated digitally by an RFIC (Radio Frequency Integrated Circuit), and power is supplied separately to the current antenna and the magnetic current antenna. (13) The antenna according to (12), wherein the voltage applied to the magnetic current antenna leads the voltage applied to the current antenna by 35 degrees to 55 degrees or lags by 125 degrees to 145 degrees. (14) The antenna according to any one of (1) to (13), which has two pairs of the electric current antenna and the magnetic current antenna, which are arranged in mutually orthogonal directions, have a configuration in which power is fed with a phase difference of 90 degrees, and function as a circularly polarized antenna. (15) The antenna according to any one of (1) to (14), further comprising a switch that switches the positive and negative terminals of the power feed unit of the electric current antenna or the magnetic current antenna.

[0134] REFERENCE SIGNS LIST 11 Master station, 12 Communication station, 13 Communication station, 14 Satellite, 21 Slave station, 32 Repeater, 101 Signal processing unit, 102 High frequency processing unit, 103 Antenna, 201 Sensing unit, 202 Baseband processing unit, 203 High frequency processing unit, 204 Antenna, 301 Magnetic current antenna, 303 Insulator, 311 Electrode, 312 Electrode, 331 Spherical electrode, 401 Switch, 402 Switch, 451 Pressure-resistant container, 471 Underwater drone

Claims

1. An antenna comprising: a current antenna formed in a linear shape and through which a current flows; a magnetic current antenna arranged in a direction perpendicular to said current antenna and generating a magnetic current; and an insulator enclosing said magnetic current antenna, wherein a portion of said current antenna is covered by said insulator and the other portion is located within a conductive medium when installed.

2. The antenna according to claim 1, wherein both ends of the current antenna are provided with spherical electrodes.

3. The antenna according to claim 1, wherein the magnetic current antenna includes a coil whose total length of wire is 1 / 8 or less of the effective wavelength of the electromagnetic wave in the insulator.

4. The antenna according to claim 3, wherein ferrite is provided as the core of the coil.

5. The antenna according to claim 1, wherein the electric current antenna and the magnetic current antenna are connected via a capacitor.

6. An antenna as described in claim 5, wherein power is supplied to the electric current antenna and the magnetic current antenna in parallel, and the capacitor is provided in series on the magnetic current antenna side of the portion where the electric current antenna and the magnetic current antenna are connected, at a position symmetrical with respect to the power supply point.

7. The antenna according to claim 1, wherein the electric current antenna and the magnetic current antenna are connected via an inductor.

8. An antenna as described in claim 7, wherein the electric current antenna and the magnetic current antenna are fed in parallel, and the inductor is provided in series on the electric current antenna side of the portion where the electric current antenna and the magnetic current antenna are connected, at a position symmetrical with respect to the feeding point.

9. The antenna according to claim 1, wherein the electric current antenna and the magnetic current antenna are connected via a capacitor and an inductor.

10. An antenna as described in claim 9, wherein the electric current antenna and the magnetic current antenna are fed in parallel, the capacitor is provided in series on the magnetic current antenna side of the portion where the electric current antenna and the magnetic current antenna are connected, at a position symmetrical with respect to the feed point, and the inductor is provided in series on the electric current antenna side, at a position symmetrical with respect to the feed point.

11. The antenna according to claim 1, wherein the electric current antenna and the magnetic current antenna are arranged so that the centers of the wave sources of the electric current antenna and the magnetic current antenna are approximately aligned, the amplitude J of the electric current source and the amplitude M of the magnetic current source have a relationship of J:M = propagation coefficient γ:1, and the magnetic current source is excited with a phase difference lag between 35 and 55 degrees or a phase difference lead between 125 and 145 degrees relative to the current source.

12. The antenna according to claim 11, wherein the phase difference is generated digitally by an RFIC (Radio Frequency Integrated Circuit), and the electric current antenna and the magnetic current antenna are fed separately.

13. The antenna according to claim 12, wherein the voltage applied to said magnetic current antenna leads the voltage applied to said electric current antenna by 35 to 55 degrees or lags the voltage applied to said electric current antenna by 125 to 145 degrees.

14. The antenna according to claim 1, which has two pairs of the electric current antenna and the magnetic current antenna, which are arranged in mutually orthogonal directions and are fed with a 90-degree phase difference, and which functions as a circularly polarized antenna.

15. The antenna according to claim 1, further comprising a switch for switching the polarity of the terminals of the power supply part of the electric current antenna or the magnetic current antenna.

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