Antenna unit, antenna device, and measurement system

Abstract

An antenna unit according to one embodiment of the present technology is used for at least one of distance measurement or positioning by a wireless signal and includes a housing, an antenna part, and a fixing part. The housing has a first end and a second end facing each other. The antenna part has a ground plane disposed to face the first end in the housing and an antenna element disposed between the ground plane and the first end. The fixing part is provided on at least one of the first end or the second end and fixes the housing to a fixing target.

Description

Antenna unit, antenna device, and measurement system

[0001] The present technology relates to an antenna unit, an antenna device, and a measurement system that can be applied to distance measurement and positioning using radio signals.

[0002] Patent Literature 1 describes an imaging device equipped with an antenna for transmitting and receiving wireless communications. In this imaging device, the antenna is positioned above the metal material portion (reflector) of the light-emitting unit (strobe) when the light-emitting unit is in the retracted position. Furthermore, an antenna protector covering the antenna is positioned so that a space is created between the antenna protector and the metal material portion of the light-emitting unit when the light-emitting unit is in the light-emitting position. This positioning makes it possible to suppress degradation of wireless communication performance in the forward and upward directions.

[0003] In recent years, technologies for measuring distance and position using wireless signals have been developed. For example, distance and positioning are performed by communicating between multiple devices using wireless signals and utilizing the results of the communication. By using such technologies, it is possible to measure the position information of various devices capable of wireless communication, such as the imaging device described in Patent Literature 1.

[0004] Japanese Patent Application Laid-Open No. 2015-1731

[0005] In ranging and positioning using radio signals, if there is a bias in the antenna's directivity, ranging accuracy may decrease depending on the communication direction, resulting in a decrease in positioning accuracy. Furthermore, methods such as placing antennas taking directivity into consideration require specialized knowledge and can take time to adjust. For this reason, there is a demand for technology that can easily improve ranging and positioning performance.

[0006] In view of the above circumstances, an object of the present technology is to provide an antenna unit, an antenna device, and a measurement system that can easily improve the performance of ranging and positioning.

[0007] To achieve the above object, an antenna unit according to one embodiment of the present technology is an antenna unit used for at least one of ranging and positioning using wireless signals, and includes a housing, an antenna unit, and a fixing unit. The housing has a first end and a second end facing each other. The antenna unit has a ground plane disposed within the housing facing the first end, and an antenna element disposed between the ground plane and the first end. The fixing unit is provided on at least one of the first end or the second end, and fixes the housing to a fixed object.

[0008] In this antenna unit, an antenna element is disposed between a first end portion and a ground plane inside a housing to form an antenna section. The housing is fixed to a fixed object by fixing portions provided at the first end portion and the second end portion. This makes it possible to easily introduce an antenna section with reduced directivity bias, for example, and easily improve ranging and positioning performance.

[0009] The antenna unit may further include at least one internal element disposed between the ground plane and the second end for operating the antenna portion.

[0010] The at least one internal element may include a communication circuit that performs wireless communication using the radio signal via the antenna unit, and a power supply unit that drives the communication circuit.

[0011] The housing may have a partition plate disposed between the first end and the second end and supporting the ground plane, and in this case, the at least one internal element may be disposed between the partition plate and the second end.

[0012] The ground plane may shield the at least one internal element from the antenna element.

[0013] The housing may have a cylindrical shape centered on a predetermined axis, in which case the antenna element may be arranged along the predetermined axis, and the ground plane may be arranged so as to be perpendicular to the predetermined axis.

[0014] The housing may have a cylindrical shape centered on the predetermined axis.

[0015] The antenna element and the ground plane may be configured to have a rotationally symmetric shape about the predetermined axis.

[0016] The ground plane may be formed to surround the predetermined axis and have an opening through which a wiring that connects the antenna element and the internal element passes.

[0017] The housing may have a window formed between the first end and the ground plane so as to surround the antenna element and allow the radio signal to pass through.

[0018] The housing may have a side surface connecting the first end and the second end, in which case the first end may be configured to be detachable from the side surface.

[0019] The fixing portion may be a screw or a screw hole.

[0020] The fixed object may be an imaging device having a screw hole for fixing, and a fixing base having a screw for fixing that can be fitted into the screw hole of the imaging device. In this case, the fixing part may include a screw provided at the first end portion and fixed to the screw hole of the imaging device, and a screw hole provided at the second end portion and fixed to the screw of the fixing base.

[0021] The target to be fixed may be a ceiling. In this case, the fixing portion may include a ceiling fixing portion that is provided at the second end portion and fixed to the ceiling.

[0022] The antenna unit may be configured as an antenna for ultra-wideband wireless communication.

[0023] The antenna element may have any of the following shapes: a cone shape, a cylinder with one end protruding in a conical shape, a sphere shape, a line shape, and a flat shape.

[0024] According to one embodiment of the present technology, there is provided an antenna device used for at least one of ranging and positioning using radio signals, the antenna device including a housing, an antenna unit, at least one internal element, and a fixed unit. The housing has a first end and a second end facing each other. The antenna unit includes a ground plane disposed within the housing facing the first end, and an antenna element disposed between the ground plane and the first end. The at least one internal element is disposed between the ground plane and the second end and operates the antenna unit. The fixed unit is provided on at least one of the first end or the second end and fixes the housing to a fixed object.

[0025] According to one aspect of the present technology, there is provided a measurement system that performs at least one of ranging and positioning using radio signals, the measurement system including at least one reference antenna device, a target antenna device, and a measurement device. The at least one reference antenna device has known position coordinates. The target antenna device communicates with the at least one reference antenna device using the radio signals. The measurement device performs at least one of ranging and positioning of the target antenna device based on a result of the communication using the radio signals between the target antenna device and the at least one reference antenna device and the position coordinates of the at least one reference antenna device. At least one of the at least one reference antenna device and the target antenna device is an antenna device having a housing having a first end and a second end opposite each other, an antenna unit having a ground plane arranged inside the housing opposite the first end, an antenna element arranged between the ground plane and the first end, at least one internal element arranged between the ground plane and the second end to operate the antenna unit, and a fixing part provided at at least one of the first end or the second end to fix the housing to a fixed object.

[0026] 1 is a schematic cross-sectional view showing an example of the configuration of an antenna unit according to an embodiment of the present technology. FIG. 2 is a schematic transparent perspective view showing an example of the configuration of the antenna unit. FIG. 3 is a schematic diagram showing a circuit configuration of the antenna unit. FIG. 4 is a schematic diagram showing an example of a measurement system configured using the antenna unit. FIG. 5 is a graph showing radiation characteristics of the antenna unit. FIG. 6 is a graph showing the relationship between received signal strength and ranging error. FIG. 7 is a graph showing azimuth angle dependence of received signal strength and ranging results in the antenna unit. FIG. 8 is a schematic diagram showing radiation characteristics of a tag with biased directivity given as a comparative example. FIG. 9 is a schematic diagram showing radiation characteristics of an antenna unit configured as a tag. FIG. 10 is a schematic diagram showing a propagation path of a wireless signal between antenna units. FIG. 11 is a block diagram showing an example of the functional configuration of a communication circuit performing UWB wireless communication. FIG. 12 is a schematic diagram showing a pulse waveform used in UWB wireless communication. FIG. 13 is a schematic diagram showing a propagation path of a UWB wireless signal. FIG. 14 is a schematic diagram explaining ranging by UWB wireless communication. FIG. 15 is a schematic diagram explaining positioning by UWB wireless communication. FIG. 16 is an example of a sequence chart for performing positioning by UWB wireless communication. FIG. 17 is a schematic diagram showing an example of a measurement system. It is a schematic diagram showing another embodiment of the measurement system. It is a schematic diagram showing another embodiment of the measurement system. It is a schematic cross-sectional view showing another configuration example of the antenna unit. It is a schematic diagram showing a configuration example of the antenna element.

[0027] Hereinafter, embodiments of the present technology will be described with reference to the drawings.

[0028] [Configuration of Antenna Unit] Fig. 1 is a schematic cross-sectional view showing an example configuration of an antenna unit according to an embodiment of the present technology. Fig. 2 is a schematic transparent perspective view showing an example configuration of the antenna unit. Fig. 3 is a schematic diagram showing a circuit configuration of the antenna unit.

[0029] The antenna unit 100 is used for at least one of distance measurement and position measurement using radio signals. Specifically, the antenna unit 100 includes an antenna section 30 that transmits and receives radio signals, and configures a measurement system that performs distance measurement or position measurement together with other wireless communication devices. The measurement system will be described later with reference to FIG. 4.

[0030] 1, the antenna unit 100 according to this embodiment is used by being fixed between a camera 110 and a tripod 120 to which the camera 110 is fixed. This makes it possible to measure the position of the camera 110 to which the antenna unit 100 is fixed. In this embodiment, the camera 110 and the tripod 120 are examples of objects to which the antenna unit 100 is fixed.

[0031] Hereinafter, the side of the antenna unit 100 to which the camera 110 is fixed may be referred to as the upper side, and the side to which the tripod 120 is fixed may be referred to as the lower side. Note that the upper and lower sides of the antenna unit 100 do not limit the orientation of the antenna unit 100, and the antenna unit 100 can be used in any position.

[0032] As shown in FIGS. 1 and 2, the antenna unit 100 includes a housing 10, an antenna section 30, an internal element 40, and a fixed section 50.

[0033] The housing 10 is a container-like structural member that houses and holds each part of the antenna unit 100. In this embodiment, the housing 10 has a cylindrical shape centered on a predetermined axis (hereinafter referred to as the central axis C). The central axis C is an axis that extends along the vertical direction of the housing 10. In this embodiment, the central axis C corresponds to the predetermined axis. The housing 10 has a first end 11, a second end 12, a side portion 13, and a partition plate 14.

[0034] The first end 11 is a plate-like member that forms one end face (here, the upper end face) of the housing 10. The second end 12 is a plate-like member that forms the other end face (here, the lower end face) of the housing 10. In this manner, the housing 10 has the first end 11 and the second end 12 that face each other. An accommodation space for accommodating the antenna unit 30 and the internal element 40 is formed between the first end 11 and the second end 12.

[0035] The side surface portion 13 is a member that connects the first end portion 11 and the second end portion 12. The side surface portion 13 is configured to connect to the outer edges of the first end portion 11 and the second end portion 12 and surround the central axis C. Therefore, the side surface portion 13 forms the side surface of the housing 10 and functions as a cover that surrounds the storage space between the first end portion 11 and the second end portion 12.

[0036] The partition plate 14 is disposed between the first end 11 and the second end 12, and is a member that supports a ground plane 31 (described later). The partition plate 14 has its outer edge connected to the inner surface of the side portion 13, and is disposed so as to face each of the first end 11 and the second end 12. By providing the partition plate 14, the storage space within the housing 10 is divided into a space on the first end 11 side and a space on the second end 12 side.

[0037] In this embodiment, the housing 10 has a cylindrical shape centered on the central axis C. Specifically, the first end 11 and the second end 12 are configured as disk-shaped members that are arranged perpendicular to the central axis C. The side portion 13 is configured as a cylindrical member. The partition plate 14 is configured as a disk-shaped member that connects to the inner peripheral surface of the side portion 13. The shape of the housing 10 does not necessarily have to be cylindrical, and may be, for example, a rectangular parallelepiped or polygonal prism. A housing 10 of any shape may be used depending on the type of object to which it is attached and the use of the antenna unit 100, etc.

[0038] In this embodiment, the first end portion 11 is configured to be detachable from the side portion 13. That is, the first end portion 11 functions as a detachable cover provided on the upper side of the housing 10. The mechanism for attaching and detaching the first end portion 11 is not limited. For example, a screw mechanism that fits the first end portion 11 by rotating the side portion 13 and the first end portion 11 relatively, or a fitting mechanism such as a snap fit, may be used. Alternatively, the side portion 13 and the first end portion 11 may be fixed together by screwing or the like.

[0039] The housing 10 is typically made of a non-conductive material that allows wireless signals to pass through. Resin materials such as plastic can be used as the non-conductive material. A metal material may also be used as part of the housing 10. As will be described later, a window 15 that allows wireless signals to pass through is formed in the area surrounding the antenna unit 30. Therefore, the portion of the housing 10 that will become the window 15 is made of a non-conductive material.

[0040] The antenna unit 30 is an antenna that transmits and receives radio signals used for ranging and positioning. The antenna unit 30 has a ground plane 31 and an antenna element 32. The ground plane 31 and the antenna element 32 form a monopole antenna in the antenna unit 30. The antenna unit 30 is also connected to an internal element 40 (communication circuit 41) (described later) via antenna wiring 35 for transmitting and receiving radio signals.

[0041] The ground plane 31 is disposed inside the housing 10 facing the first end 11. More specifically, the ground plane 31 is disposed spaced apart from the first end 11 with one surface facing the underside of the first end 11. The ground plane 31 is a conductor connected to a ground potential, and is connected to a ground line 35b that constitutes the antenna wiring 35.

[0042] The ground plane 31 is typically configured as a disk-shaped conductor. For example, a substrate on which a copper film is formed, a copper metal plate, or the like is used as the ground plane 31. In this embodiment, the ground plane 31 is arranged so as to be perpendicular to the central axis C of the housing 10. Specifically, the ground plane 31 is arranged along the partition plate 14 so that the center of the disk passes through the central axis C. In the example shown in FIG. 1 , the ground plane 31 is arranged on the upper surface of the partition plate 14. This allows internal elements, etc., described below, to be directly fixed to the lower surface of the partition plate 14. Note that the ground plane 31 may also be arranged on the lower surface of the partition plate 14.

[0043] The antenna element 32 is disposed between the ground plane 31 and the first end 11. Therefore, the antenna element 32 is disposed above and facing the ground plane 31. The antenna element 32 is a conductor that is not connected to the ground potential, and is connected to a signal line 35a that constitutes the antenna wiring 35.

[0044] In this embodiment, the antenna element 32 has a conical shape. The conical antenna element 32 is disposed with its apex pointing downward (toward the ground plane 31). The conical antenna element 32 may be, for example, a conical antenna element made of a metal such as copper, or a conical element made of plastic or the like with a copper film or the like formed on the surface thereof. The interior of the antenna element 32 may be hollow. In this case, the upper screw 51 (described later) can be accommodated inside the antenna element 32, thereby making it possible to reduce the height (vertical width) of the housing 10. The interior of the antenna element 32 does not have to be hollow.

[0045] In this embodiment, the antenna element 32 is disposed along the central axis C. Specifically, the conical antenna element 32 is disposed so that its central axis coincides with the central axis C of the housing 10. The method for fixing the antenna element 32 is not limited. For example, the antenna element 32 may be fixed using a holder (not shown) made of a non-conductive material. Alternatively, the signal line 35a may be made of a rigid conductor, and the antenna element 32 may be fixed by the signal line 35a. Alternatively, a resin material such as an adhesive may be filled between the antenna element 32 and the ground plane 31.

[0046] In this way, the antenna element 32 and the ground plane 31 are configured to have a rotationally symmetric shape about the central axis C. In this embodiment, the conical antenna element 32 is arranged along the central axis C, and the disk-shaped ground plane 31 is arranged below it so that its center is perpendicular to the central axis C. This configures a monopole antenna (antenna unit 30) that is substantially omnidirectional in the azimuth direction centered on the central axis C. Here, being omnidirectional in the azimuth direction means having substantially uniform directivity in all directions centered on the central axis C.

[0047] The housing 10 also has a window 15 formed between the first end 11 and the ground plane 31 to surround the antenna element 32 and allow radio signals to pass through. Specifically, the window 15 is formed in the side surface 13 of the housing 10. For example, the portion of the side surface 13 from the ground plane 31 to the top of the antenna element 32 is configured as the window 15, and the portion that becomes the window 15 is made of a non-conductive material such as plastic so as not to block radio signals. Furthermore, the window 15 is typically formed around the entire circumference of the central axis C. This prevents the housing 10 from causing a bias in the directivity of the antenna unit 30, allowing the entire antenna unit 100 to exhibit omnidirectionality. The area in which the window 15 is formed is not limited, and the area in which the window 15 is formed may be appropriately set so that the antenna unit 100 can achieve the required radiation characteristics.

[0048] The internal element 40 is an element that is disposed between the ground plane 31 and the second end 12 and operates the antenna section 30. That is, the internal element 40 is disposed in the space below the ground plane 31 within the accommodation space of the housing 10. The antenna unit 100 is provided with at least one internal element 40.

[0049] In this embodiment, each internal element 40 is disposed between the partition plate 14 supporting the ground plane 31 and the second end 12. Providing the partition plate 14 makes it possible to dispose each internal element 40 independently of the ground plane 31, for example, facilitating the design and assembly of the antenna unit 100. The internal elements 40 provided in the antenna unit 100 include a communication circuit 41 and a battery 42.

[0050] The communication circuit 41 is a circuit that performs wireless communication using the radio signal via the antenna unit 30. The antenna unit 30 (antenna element 32 and ground plane 31) is connected to the communication circuit 41 via antenna wiring 35, and an electrical signal corresponding to the radio signal received by the antenna unit 30 is input to the communication circuit 41. The communication circuit 41 also outputs an electrical signal that generates a radio signal to the antenna unit 30 via the antenna wiring 35. The communication circuit 41 may be an element or the like in which circuits (amplifier circuit, filter, arithmetic circuit, etc.) for performing wireless communication are packaged. Alternatively, a communication module or the like in which each circuit is mounted on a substrate may be used. The functional configuration of the communication circuit 41 will be described later with reference to FIG. 11 etc.

[0051] The battery 42 is a secondary battery that supplies a predetermined amount of power and drives the communication circuit 41. The battery 42 is charged, for example, by a charging cable connected to a charging terminal (not shown) provided on the housing 10. Alternatively, the second end 12 may be configured to be detachable, and the battery 42 may be configured to be removable. In this embodiment, the battery 42 corresponds to a power supply unit. Note that the communication circuit 41 may be driven by an external power supply instead of the battery 42. In this case, a power supply circuit or the like that adjusts the power from the external power supply may be provided as the power supply unit.

[0052] The specific configuration of the internal element 40 is not limited. For example, a bandpass filter or the like that connects the antenna section 30 and the communication circuit 41 may be provided as the internal element 40. A sensor that detects the attitude of the antenna unit 100, a calculation unit that processes data from the sensor, or the like may also be provided. A light-emitting element or a speaker that indicates the operating state of the antenna unit 100 may also be provided, or a passive element such as a capacitor or a transformer may also be provided.

[0053] 3, a description will be given of the connection configuration of the antenna unit 30, the communication circuit 41, and the battery 42. In this embodiment, a coaxial cable is used as the antenna wiring 35 that connects the antenna unit 30 and the communication circuit 41. The core wire of the coaxial cable serves as the signal line 35a, and the braided wire that surrounds the core wire with an insulating material interposed therebetween serves as the ground line 35b.

[0054] As shown in FIG. 3 , an opening 33 is formed in the ground plane 31. The opening 33 is formed to surround the central axis C and is a through-hole through which the antenna wiring 35 passes, connecting the antenna element 32 and the internal element 40 (here, the communication circuit 41). In this example, a circular opening 33 is provided in the center of the ground plane 31. A signal line 35a of the antenna wiring 35 is connected to the antenna element 32 through the opening 33. A ground line 35b is connected to the ground plane 31 near the opening 33 of the ground plane 31. This makes it possible to arrange a coaxial line up to the vicinity of the opening 33, which suppresses the inflow of noise between the antenna unit 30 and the communication circuit 41 and enables the electrical signal to be transmitted properly.

[0055] Furthermore, on the communication circuit 41 side, the signal line 35a of the antenna wiring 35 is connected to a signal terminal 41a of the communication circuit 41, and the ground line 35b is connected to a ground terminal 41b of the communication circuit 41. The ground line 35b and the ground terminal 41b are connected to a ground section 45 that serves as the ground potential of the antenna unit 100. Note that a matching circuit or the like may be provided between the antenna section 30 and the communication circuit 41, if necessary, to achieve impedance matching.

[0056] The positive output terminal 42a of the battery 42 is connected to a power supply terminal 41c of the communication circuit 41, and the negative output terminal 42b is connected to a ground part 45. As a result, the communication circuit 41 is driven by the power supplied from the battery 42.

[0057] In this way, the antenna unit 100 functions as an antenna device capable of wireless communication by itself by including, in addition to the antenna section 30, the internal elements 40 (communication circuit 41 and battery 42) that operate the antenna section 30. Therefore, it can be said that the antenna unit 100 is configured as an antenna device that performs wireless communication.

[0058] Returning to FIG. 1 , internal elements 40 such as a communication circuit 41 and a battery 42 are disposed below the ground plane 31 and housed within the housing 10. With this configuration, the ground plane 31 shields at least one internal element 40 from the antenna element 32. For example, when viewed from above along the central axis C, each internal element 40 is disposed so as to fit within the range of the ground plane 31. As a result, each internal element 40 is not visible from the antenna element 32. By shielding each internal element 40 from the antenna element 32 in this way, it is possible to avoid situations such as a change in the directivity of the antenna unit 30 due to the influence of metals constituting the internal element 40 or the internal element 40 itself, or a decrease in the reception performance of the antenna unit 30 due to the influence of noise generated by these.

[0059] The fixing portion 50 is provided on at least one of the first end 11 and the second end 12, and fixes the housing 10 to a fixing object. By providing the fixing portion 50, the antenna unit 100 can be easily fixed to various fixing objects for use. As shown in Figures 1 and 2, in this embodiment, the fixing portion 50 is provided on both the first end 11 and the second end 12. Furthermore, a screw or a screw hole is used as the fixing portion 50.

[0060] As shown in FIG. 1 , in this embodiment, the objects to be fixed are a camera 110 having a screw hole 111 for fixing, and a tripod 120 having a screw 121 for fixing that can be fitted into the screw hole 111 of the camera 110. The camera 110 is an imaging device having the screw hole 111 provided on the underside of its body. The direction of the screw hole 111 is typically perpendicular to the shooting direction of the camera 110 (to the right in FIG. 1 ). The tripod 120 is a fixed base that supports a camera platform 123 (camera platform) provided at the top end of an elevator unit 122 (elevator) with three legs. The legs of the tripod 120 are not shown in FIG. 1 . The camera platform 123 is provided with a fixing screw 121 with the screw portion facing upward.

[0061] The antenna unit 100 is provided with an upper screw 51 and a lower screw hole 52 as a fixing portion 50 .

[0062] The upper screw 51 is provided on the first end 11 and fixed to the screw hole 111 of the camera 110. The upper screw 51 passes through the first end 11 and is arranged with the threaded portion facing upward. The upper screw 51 is provided, for example, to be rotatable with respect to the first end 11. In this case, the first end 11 is removed and the upper screw 51 is fitted into the screw hole of the camera 110, thereby fixing the first end 11 to the underside of the camera 110. Next, with the camera 110 fixed, the first end 11 is attached to the housing 10. The upper screw 51 may also be configured as a fixing screw fixed to the first end 11. In this case, the entire housing 10 can be rotated to fit the upper screw 51 into the screw hole of the camera 110.

[0063] The lower screw hole 52 is provided in the second end 12 and is fixed to a screw 121 of the tripod 120. The lower screw hole 52 is a screw hole formed from the second end 12 toward the upper side of the housing 10. For example, the housing 10 is fixed to the upper side of the pan head 123 by fitting a screw 121 provided in the pan head 123 of the tripod 120 into the lower screw hole 52.

[0064] In this way, the antenna unit 100 can be easily attached between the camera 110 and the tripod 120 by utilizing the fixing mechanism between the camera 110 and the tripod 120. This makes it possible to easily configure an imaging system capable of distance measurement and positioning using the antenna unit 100 without providing a special fixing jig or the like.

[0065] [Configuration of measurement system] Various wireless signals such as GNSS (Global Navigation Satellite System), cellular, Bluetooth (registered trademark), WiFi (registered trademark), and UWB (Ultra-Wide Band) can be used for positioning using wireless signals. As will be described later, in this embodiment, a case where UWB is mainly used will be described as an example. Note that the present technology can also be applied to cases where other types of wireless signals are used.

[0066] Methods of positioning using radio signals include a method of positioning from relative distance, a method of positioning from the time difference of arrival (TDOA) of radio signals, and a method of positioning from the angle of arrival (AoA) of radio signals.

[0067] The relative distance method measures positioning based on the relative distance between a communication device called an anchor, whose position coordinates are known, and a communication device called a tag, whose position is to be measured. For example, the relative distance between three anchors A, B, and C and tag P is measured, and the position of tag P is determined by finding the intersection of a circle whose center is each anchor A, B, and C and whose radius is the relative distance of tag P. The TDOA method measures the arrival time difference at anchors A, B, and C of the radio signal emitted by tag P and measures the position of tag P based on the properties of a hyperbola. Note that when using TDOA, the time at each anchor must be synchronized. The AoA method measures the angle of arrival of a radio signal from the phase difference between the radio signals (plane waves) arriving at two antennas, and by combining it with ranging, relative positioning is possible. Note that when using AoA, the configuration of the antenna and high-frequency circuit may become complex.

[0068] For positioning using radio signals, these methods are used alone or in combination. Of these, the method using relative distance does not require time synchronization of each anchor or the configuration of complex antennas or circuits, and allows for the configuration of a system with a relatively simple configuration. Below, we will mainly explain a method of positioning by measuring relative distance (ranging) using radio signals. Note that this technology can also be applied when performing positioning using TDOA or AoA.

[0069] 4 is a schematic diagram showing an example of a measurement system configured using an antenna unit. The measurement system 101 has three anchors A, B, and C, a tag P, and a measurement device Q, and is a system that measures the position of the tag P using wireless signals. In this embodiment, the tag P is fixed to a camera 110, allowing the camera 110 to be positioned.

[0070] Anchors A, B, and C are antenna devices whose position coordinates are known. Each of anchors A, B, and C is fixed to, for example, a ceiling, and their relative positions are known. The plane formed by the triangle connecting the position coordinates of anchors A, B, and C is the positioning plane in measurement system 101. The positioning plane is, for example, a horizontal plane perpendicular to the vertical direction.

[0071] The tag P is an antenna device that communicates with the anchors A, B, and C by radio signals. In this embodiment, the anchors A, B, and C correspond to at least one reference antenna device. The tag P corresponds to a target antenna device.

[0072] Here, communication by radio signals means, for example, two-way communication. In the following, it is assumed that two-way communication is possible between the tag P and each of the anchors A, B, and C. Note that one-way communication such as GNSS may also be used as the communication by radio signals. This technology can also be applied to a system that performs positioning by one-way communication.

[0073] The measurement device Q performs at least one of distance measurement and position measurement of the tag P based on the results of communication via wireless signals between the tag P and the anchors A, B, and C and the position coordinates of the anchors A, B, and C. In this embodiment, distance measurement of the tag P (measurement of relative distances da, db, and dc between the tag P and the anchors A, B, and C) is performed. The relative distances between the tag P and the anchors A, B, and C are estimated from the signal transmission time (propagation time) of wireless communication, as will be described later. Positioning of the tag P (measurement of the position coordinates of the tag P) is performed based on the distance measurement results for the tag P and the position coordinates of the anchors A, B, and C (see FIG. 15 , etc.). The measurement device Q may be configured by any of the tag P and the anchors A, B, and C, or may be configured by a server device or the like that can communicate with the tag P and the anchors A, B, and C.

[0074] In the measurement system 101, at least one of the anchors A, B, C and tag P is configured using the antenna unit 100 according to this embodiment. For example, the tag P to which the camera 110 is fixed is configured using the antenna unit 100. Of course, the anchors A, B, and C may also be configured using the antenna unit 100. Here, it is assumed that the antenna unit 100 is used as all the antenna devices (tag P and anchors A, B, and C).

[0075] The measurement system 101 also uses UWB wireless signals. Positioning using UWB wireless signals involves sending and receiving short pulses of about 2 ns, making it possible to detect signal propagation times with precision on the order of nanoseconds. This corresponds to distances on the order of centimeters. In this way, the use of UWB makes it possible to achieve highly accurate distance and positioning.

[0076] In the measurement system 101, the directivity of the antenna is extremely important in communication between anchors and tags or between anchors. This is because the quality of communication between tag P and anchors A, B, and C affects the distance measurement results. In particular, UWB is required by law to use very weak radio waves (radio signals), so depending on the antenna configuration, it may be necessary to position the device in accordance with the antenna directivity, etc., in order to ensure communication quality.

[0077] [Characteristics of the Antenna Unit] Figure 5 is a graph showing the radiation characteristics of the antenna unit. In Figure 5, a radiation pattern 36a in a plane direction (azimuth direction) perpendicular to the central axis C of the antenna unit 100 is schematically shown by a dotted line. Also, a radiation pattern 36b in a communication device given as a comparative example is schematically shown by a dashed line. The communication device given as a comparative example here is a communication unit in which a monopole antenna is mounted on a circuit board using, for example, ceramic or the like. The radiation pattern 36b shows a pattern along the ground plane of the monopole antenna.

[0078] The radiation pattern shown in Figure 5 is a radiation pattern for a frequency (e.g., 8 GHz) included in the UWB band. The radiation pattern also represents the radiation intensity [dB] of the wireless signal for each direction. Here, the X direction is defined as the direction with an azimuth angle of 0 degrees, and the Y direction is defined as the direction with an azimuth angle of 90 degrees.

[0079] First, we will explain the radiation pattern 36b of a communication device given as a comparative example. UWB communication involves transmitting and receiving ultra-wideband signals, such as 500 MHz signals, on an 8 GHz carrier wave, so antennas must also support a wide bandwidth. For this reason, there are few types of antennas that can be used for UWB, and miniaturizing antennas is not easy. Generally, monopole antennas mounted on circuit boards are used, as in the communication device given as a comparative example. However, these antennas are often small and flat with low component height. Therefore, the antenna radiation pattern is prone to bias in directionality due to the influence of the circuit board, other circuit elements, housing, etc. For example, in the example shown in Figure 5, the radiation intensity decreases near the azimuth angles of 90 degrees and 270 degrees. Therefore, it is difficult to achieve omnidirectional radiation characteristics.

[0080] In contrast, in the antenna unit 100 according to this embodiment, as described with reference to FIGS. 1 to 3 , the antenna section 30 is configured to be rotationally symmetric about the central axis C. This allows the antenna section 30 to transmit and receive radio signals at a similar level in all directions. Furthermore, for example, a window 15 that allows radio signals to pass through is provided around the entire periphery of the housing 10 in a portion surrounding the antenna section 30. This makes it possible to avoid situations in which the directivity is changed by the housing 10. Furthermore, the internal elements 40, such as the communication circuit 41 and the battery 42, are shielded by the ground plane 31 of the antenna section 30. This makes it possible to sufficiently suppress bias in directivity caused by the internal elements 40.

[0081] By configuring the antenna unit 100 in this manner, it is possible to make the radiation pattern 36a of the antenna unit 100 approximately circular. That is, it is possible to realize a radiation pattern that is substantially omnidirectional in the azimuth direction centered on the central axis C. Note that although FIG. 5 illustrates a circular radiation pattern 36a, in reality, some bias may occur depending on the azimuth angle. In this regard, the antenna unit 100 is configured to have a radiation pattern that can achieve the required positioning accuracy in all directions, for example. In other words, the azimuth radiation pattern of the antenna unit 100 may have some bias depending on the azimuth angle as long as the required positioning accuracy can be achieved.

[0082] [Received Signal Strength and Ranging Accuracy] Fig. 6 is a graph showing the relationship between received signal strength and ranging error. The horizontal axis of the graph is received signal strength (RSSI) [dB], and the vertical axis is ranging error [m]. The graph shown in Fig. 6 shows data obtained when measuring the relative distance between two antenna units 100 using UWB. Here, the relative distances were measured at 0.5 m (circular data points), 1.5 m (rectangular data points), 2.0 m (cross data points), and 4.0 m (triangular data points) without changing the relative orientation between the antenna units 100.

[0083] From the graph shown in Figure 6, it can be seen that the RSSI decreases as the relative distance increases. Furthermore, the smaller the RSSI, the greater the range error. The inventors have found that there is a correlation between RSSI and range error, and that when the RSSI is small, the ranging accuracy tends to decrease. This suggests that the ranging accuracy may decrease in directions where the antenna has low directivity.

[0084] Fig. 7 is a graph showing the azimuth angle dependence of the received signal strength and ranging results in the antenna unit 100. The thin dotted line and thick dotted line graphs in Fig. 7 are graphs showing the RSSI 37a and ranging results 38a in the antenna unit 100 having the dotted line radiation pattern 36a shown in Fig. 5. The thin dashed line and thick dashed line graphs in Fig. 7 are graphs showing the RSSI 37b and ranging results 38b in a communication device of a comparative example having the dashed line radiation pattern 36b shown in Fig. 5.

[0085] The data shown in Fig. 7 are obtained by, for example, measuring a radio signal from a fixed-position transmitting antenna while rotating the antenna unit 100 (or a communication device of the comparative example) around its central axis. The horizontal axis in Fig. 7 represents the rotation angle (orientation as seen from the antenna). The vertical axis on the left represents RSSI, and the vertical axis on the right represents the ranging results. In this example, the relative distance to the transmitting antenna is approximately 2.1 m.

[0086] For example, in the comparative example, the radiation intensity decreases at 90 degrees and 270 degrees (see FIG. 5). Therefore, as shown in FIG. 7, the RSSI 37b in the comparative example decreases around 90 degrees and 270 degrees, and as a result, the distance measurement result 38b changes significantly compared to other directions. This is because the decrease in RSSI increases the distance measurement error.

[0087] In contrast, with the antenna unit 100, which has an omnidirectional radiation pattern as shown in Figure 5, the receiving sensitivity does not decrease depending on the azimuth, so a constant RSSI 37a is obtained in all azimuths. As a result, there is no bias in the ranging error, and it is possible to obtain stable ranging results 38a in all azimuths. In this way, the antenna unit 100 has uniform directivity in the azimuth direction, making it possible to perform appropriate ranging in any azimuth.

[0088] [Directivity and Positioning of Antenna Unit 100] Fig. 8 is a schematic diagram showing the radiation characteristics of a tag with biased directivity, given as a comparative example. In the comparative example shown in Fig. 8, the directivity of tag P' attached to camera 110 is biased. Here, the radiation characteristics (radiation pattern 36) of tag P' in the horizontal plane are shown, with regions of high radiation intensity being schematically illustrated by shaded regions. The radiation characteristics of tag P' have a relatively high radiation intensity in front of camera 110, with the imaging direction of camera 110 as the center, and a relatively low radiation intensity in the rear and left / right directions.

[0089] For example, in the state shown in Fig. 8, tag P' can properly communicate with anchor A located to the left front and anchor B located to the right front. On the other hand, with anchor C located to the left rear, communication with a sufficiently high RSSI may not be possible, or communication may not even be established.

[0090] In particular, the orientation of the camera 110 equipped with the tag P' is changed arbitrarily depending on the position of the subject, etc. Therefore, if the antenna directionality is not omnidirectional, depending on the orientation of the camera 110 (the orientation of the antenna of the tag P'), there is a possibility that the communication characteristics will deteriorate, reducing the accuracy of ranging and positioning.

[0091] 9 is a schematic diagram showing the radiation characteristics of an antenna unit configured as a tag. Here, a tag P configured with an antenna unit 100 is placed in the same position and orientation as the tag P' of the comparative example shown in FIG. 8. The radiation characteristics (radiation pattern 36) of the tag P in the horizontal plane are shown with shaded areas representing regions of high radiation intensity.

[0092] As shown in FIG. 9 , the radiation characteristics of tag P configured using the omnidirectional antenna unit 100 form a substantially circular radiation pattern 36 centered on tag P. Therefore, regardless of the direction in which the camera 110 equipped with tag P is oriented, proper communication with each of anchors A, B, and C is possible. As described above, the radiation pattern 36 of the antenna unit 100 may have some bias depending on the azimuth angle. For example, referring to FIG. 6 , the difference between the maximum and minimum values ​​of the radiation pattern 36 of the antenna unit 100 is preferably 3 dB or less. This makes it possible to suppress the ranging error in each direction to approximately 0.05 m or less. Furthermore, it is more preferable that the difference between the maximum and minimum values ​​of the radiation pattern 36 be 1 dB or less. This makes it possible to suppress the ranging error in each direction to a smaller value (e.g., 0.03 m or less). This configuration makes it possible to achieve high-precision ranging in all directions.

[0093] Furthermore, because the antenna unit 100 (tag P) is placed between the camera 110 and the tripod 120, the user who places the camera 110 can install the antenna unit 100 in a position where the radiation characteristics of the radio signal are omnidirectional in the horizontal direction, without any special consideration. This makes it possible for even non-antenna experts to easily improve positioning performance. This method can be said to be a method that makes it possible to determine the relative position of the camera 110 very easily, compared to surveying methods that use, for example, a laser rangefinder.

[0094] Furthermore, by configuring the housing 10 of the antenna unit 100 in a cylindrical shape, it is possible to expect the effect of making the directivity of the antenna unit 100 uniform in the horizontal direction, that is, bringing it closer to an ideal omnidirectional state. Furthermore, by using a cylindrical housing 10, it is possible to make the user aware that a wireless signal is radiated around the cylinder.

[0095] Furthermore, the antenna unit 100 can be positioned based on the screw holes 111 of the camera 110. Furthermore, when UWB is used, positioning can be performed with an accuracy of several centimeters. Therefore, when multiple cameras 110 are arranged (see FIG. 17 , etc.), the reference positions of the cameras 110 can be aligned with high accuracy based on the positioning results of the antenna units 100 fixed to each camera 110.

[0096] Furthermore, by disposing the antenna unit 100 between the tripod 120 (platform 123) and the camera 110, it is possible to prevent the radiation characteristics from being biased by the camera 110 or the tripod 120, and to ensure the omnidirectionality of the antenna. This makes it possible to sufficiently improve the accuracy of distance measurement and positioning of the camera 110.

[0097] FIG. 10 is a schematic diagram showing the propagation path of a radio signal between antenna units 100. In FIG. 10, a radio signal propagates from the antenna unit 100a on the left to the antenna unit 100b on the right. In the antenna unit 100a, an electric field is formed between the antenna element 32 and the ground plane 31, thereby transmitting the radio signal (radio wave). Therefore, by increasing the size of the ground plane 31, it is possible to reduce the emission angle (elevation angle) of radio waves traveling in the horizontal direction, for example. In particular, it is possible to reduce the radio waves traveling downward (toward the ground) from the antenna unit 100, thereby suppressing ground reflection components.

[0098] Furthermore, by enlarging the ground plane 31 in the receiving antenna unit 100b, it becomes easier to block the components transmitted from the antenna unit 100a and reflected by the ground. This makes it possible to reduce the ground reflection components on the receiving side as well. As a result, in the antenna unit 100b, interference between the direct wave and the ground reflection components is less likely to occur, making it possible to improve the performance of ranging and positioning.

[0099] [UWB Wireless Communication] Distance measurement and positioning using UWB wireless communication will be specifically described below. A UWB wireless communication system is a system that communicates using pulses with a width of 2 ns at a carrier frequency of several GHz (e.g., around 8 GHz), and uses a wide bandwidth of, for example, about 500 MHz. Because UWB wireless communication uses pulses with very short widths, it is possible to perform highly accurate distance measurement, positioning, direction detection, and highly accurate time synchronization between communication devices. For example, as described above, the distance measurement accuracy is on the order of centimeters.

[0100] Furthermore, UWB communication circuits can be compact, similar to those used in Bluetooth (registered trademark). Because it is possible to build communication systems, a wide range of network configurations are possible, from point-to-point networks to N-to-N networks. Other applications include low-latency data transfer and RF sensing, which detects radio waves over a wide frequency band.

[0101] In this embodiment, in order to construct such a communication system, the antenna unit 30 is configured as an antenna for UWB wireless communication. For example, the antenna unit 30 described with reference to Figures 1 to 3 has a conical antenna element 32, which widens the transmittable and receive band and enables UWB wireless communication. Alternatively, the antenna unit 30 may have any configuration capable of receiving ultra-wideband wireless signals.

[0102] [Communication Circuit of Antenna Unit] Fig. 11 is a block diagram showing an example of the functional configuration of a communication circuit 41 that performs UWB wireless communication. Fig. 12 is a schematic diagram showing a pulse waveform used in UWB wireless communication.

[0103] 11 shows a schematic diagram of the configuration of the communication circuit 41, which is divided into a transmitter 60 that transmits UWB radio signals and a receiver 70 that receives UWB radio signals. For example, the tag P and anchors A, B, and C described with reference to FIG. 4 and the like function as the transmitter 60 and the receiver 70, respectively. The antenna unit 100 according to this embodiment can be used as either the transmitter 60 or the receiver 70.

[0104] The transmitter 60 includes a correlation sequence output unit 61, a transmission data output unit 62, a transmission circuit 63, and a transmission antenna 64. The correlation sequence output unit 61 outputs a predetermined correlation sequence used for wireless communication. The correlation sequence 65 is, for example, a sequence x ｋ , which is composed of three values, for example, -1, 0, and +1. The correlation sequence output unit 61 appropriately reads and outputs a correlation sequence 65 stored in a memory unit (not shown) of the communication circuit 41. The transmission data output unit 62 generates and outputs transmission data 66 including data necessary for ranging (e.g., the transmission time of the radio signal, etc.). As shown in FIG. 11 , the correlation sequence 65 and the transmission data 66 are combined with the correlation sequence 65 in front, and output as a continuous transmission signal 67 to the transmission circuit 63. The transmission circuit 63 converts the transmission signal 67 into an RF signal of a predetermined carrier frequency and outputs it to the transmission antenna 64. The transmission antenna 64 radiates the input RF signal as a UWB radio signal (UWB signal 68).

[0105] FIG. 12 shows a schematic diagram of the pulse waveform of a radio signal. The arrows in FIG. 12 represent time t. Here, pulses 69 corresponding to 0, +1, -1, and +1 are shown in order from the beginning (right side of the diagram). 0 has no pulse waveform, +1 is a waveform in which the central peak of the pulse 69 is formed on the positive side, and -1 is a waveform in which the central peak of the pulse 69 is formed on the negative side. The waveforms of +1 and -1 are waveforms in which the positive and negative sides are reversed. A transmission signal 67 is transmitted by outputting such pulses 69 at a predetermined interval.

[0106] Returning to FIG. 11 , the receiver 70 includes a receiving antenna 71, a receiving circuit 72, a correlation sequence output unit 73, a correlator 74, and an arrival time detection unit 75. The receiving antenna 71 receives a UWB radio signal (UWB signal 68) emitted from the transmitting antenna 64, converts it into an RF signal, and outputs it to the receiving circuit 72. The receiving circuit 72 converts the RF signal into a baseband signal and outputs it to the correlator 74. The correlation sequence output unit 73 appropriately reads out a correlation sequence 65, the same as that used in the transmitter 60, from a memory unit (not shown) of the receiver 70 and outputs it to the correlator 74. The correlator 74 calculates the correlation with the correlation sequence and determines whether or not a correlation has been achieved. The arrival time detection unit 75 detects the arrival time of the transmission signal 67 based on the determination result of the correlator 74.

[0107] Here, the operation of the correlator 74 will be described. First, the transmitter 60 and the receiver 70 agree on the correlation sequence 65 to be used. Here, the correlation sequence x of length k is ｋ Correlation r of ｋ The formula for calculating this is expressed as follows:

[0108] ...(1)

[0109] The correlator 74 calculates a correlation sequence x for the baseband signal output from the receiving circuit 72 as shown in equation (1). ｋ For example, the correlation r ｋ takes the value A, otherwise it is 0. This allows the correlation r ｋ becomes A, the timing can be detected as the arrival time of the transmission signal 67. The arrival time detected in this way is used to calculate the relative distance between the transmitter 60 and the receiver 70. Note that the type of correlation sequence 65 is not limited, and for example, a preamble code defined in IEEE 802.15.4z-2020 or the like can be used as appropriate.

[0110] [Positioning by UWB wireless communication] Fig. 13 is a schematic diagram showing a propagation path of a UWB wireless signal. Fig. 14 is a schematic diagram illustrating distance measurement by UWB wireless communication. Fig. 15 is a schematic diagram illustrating positioning by UWB wireless communication. Positioning by UWB wireless communication will be described below with reference to Figs. 13 to 15.

[0111] As shown in Figure 13, part of the pulse 69 emitted from the transmitting side is received as a direct wave that reaches the receiving side via a straight path. Other parts of the pulse 69 are reflected by the floor, ceiling, surrounding obstacles, etc., and propagate to the receiving side via various paths. In this way, multipaths are formed between the transmitting side and the receiving side. Of these, the earliest received first wave 69s is the direct wave that has traveled the shortest straight path. Therefore, in order to detect the arrival time of the pulse 69, the first wave 69s is estimated. The correlation sequence described above can be used, for example, to estimate the first wave 69s.

[0112] 14 is a schematic diagram showing a method for measuring the relative distance between the antenna units 100a and 100b using the arrival time. For example, the antenna unit 100a is an anchor and the antenna unit 100b is a tag, but the reverse may also be true. A pulse 69 is transmitted from the antenna unit 100a, and T prop Later, the pulse 69 is received by the antenna unit 100b. Then, the response time T reply After the time has elapsed, a pulse 69 is transmitted from the antenna unit 100b, and T prop The antenna unit 100a receives the pulse 69 after the first pulse 69 is transmitted, receives the second pulse 69 (arrival time), and receives the pulse 69. reply From the value of prop is detected. Then, the propagation time T prop is multiplied by the speed of light c to calculate the relative distance d between the antenna units 100a and 100b (d=T prop14 is the so-called SS-TWR (Single-Sided Two-Way Ranging) method. Note that the distance measurement method is not limited to this method, and other methods can also be used.

[0113] 15 is a schematic diagram showing a method for measuring (locating) the position of tag P from the relative distances between multiple anchors and tag P. Here, it is assumed that the position coordinates x1, x2, x3, and x4 of four anchors A1, A2, A3, and A4 are known. Here, x1 is set to the reference coordinate x ref The coordinates of tag P are x Tag The relative distances between the tag P and the anchors A1, A2, A3, and A4 are written as d1, d2, d3, and d4. Here, d1 is the reference distance d ref Let's say

[0114] Coordinate x of tag P Tag is expressed using the following formula: A x Tag = b (2) Furthermore, A and b in equation (2) are expressed using the following equations.

[0115] ...(3)

[0116] ...(4)

[0117] In equation (3), A is a matrix containing fixed values ​​represented by the position coordinates of each anchor. The number of columns in A changes depending on the dimension (number of coordinates). The number of rows corresponds to the number of anchors. In equation (4), the first term on the right side is a vector containing fixed values ​​represented by the position coordinates of each anchor. The second term is a relative distance calculated using the method shown in FIG. 15 or the like, and is a vector containing measured values. By calculating the matrix A and vector b and substituting them into equation (2), the coordinate x of tag P can be calculated. Tag is calculated.

[0118] Fig. 16 is an example of a sequence chart for performing positioning by UWB wireless communication. Fig. 16 illustrates an example of communication processing performed between the tag P, multiple anchors A1, A2, ..., and the positioning server S to perform positioning of the tag P. First, communication is performed between the tag P and anchor A1. Here, the method of positioning from the relative distance described above is used as the positioning method for the tag P.

[0119] First, the tag P transmits a Poll message to the anchor A1, which receives it (step 101). At this time, the tag P receives the Poll message at the transmission time T ｐｔ The anchor A1 receives the Poll message at time T ｐｒ Record the following.

[0120] The anchor A1 transmits a Response message to the tag P, and the tag P receives the Response message (step 102). At this time, the anchor A1 receives the Response message at the transmission time T ｒｔ The tag P is the time when the response message is received. ｒｒ Record the following.

[0121] The tag P sends a Final message to the anchor A1, which receives it (step 103). The tag P sends the Final message to the anchor A1. ｐｔ , T ｒｒ and a predetermined Final message transmission time T ｆｔ Anchor A1 is recorded as T ｐｔ , T ｒｒ , T ｆｔ and the time T ｆｒ Also measure the received signal strength of the Final message.

[0122] Anchor A1 is T ｐｔ , T ｐｒ , T ｒｔ , T ｒｒ , T ｆｔ , T ｆｒ Using the propagation time T prop, and calculates the distance between anchor A1 and tag P (step 104). Also, a predetermined reliability index is created from the received signal strength of the Final message. Note that the reliability index does not necessarily have to be created.

[0123] The distance measurement method used in the sequence chart shown in Fig. 17 is the so-called DS-TWR (Double-Sided Two-Way Ranging) method. This method calculates the distance from the transmission and reception times of each message by sending messages multiple times between two devices (tag and anchor). Here, the Three Messages method is applied. In this case, the following parameters are calculated: T ｒｏｕｎｄ１ =T ｒｒ -T ｐｔ T ｒｏｕｎｄ２ =T ｒｔ -T ｆｒ T ｒｅｐｌｙ１ =T ｒｔ -T ｐｒ T ｒｅｐｌｙ２ =T ｒｒ -T ｆｔ Furthermore, by substituting these parameters into the following equation, the propagation time T prop is calculated.

[0124] ...(5)

[0125] Propagation time T calculated from equation (5) prop is multiplied by the speed of light c to calculate the relative distance d between the tag P and the anchor A1 (d=T prop ・c).

[0126] The anchor A1 reports the distance measurement result and reliability information to the positioning server S using a distance message (step 105).

[0127] Similarly, distances are measured between the other anchors A2, A3, ... and the tag P, and each anchor reports the distance measurement results to the positioning server S. Here, the description of the steps for the other anchors will be omitted.

[0128] The positioning server S performs calculations for positioning based on the distance measurement results reported from the anchors A1, A2, ... (step 106). In this process, the positioning method described with reference to Fig. 16, for example, is used.

[0129] The positioning server S reports the positioning result to the anchor A1 using a Position message (107). The anchor A1 also reports the positioning result to the tag P using a Report message. Here, it is assumed that the anchor A1 first receives a Poll message from the tag P, but the positioning result may be determined by other methods. The positioning server S may also directly transmit the positioning result to the tag P.

[0130] [Measurement System Using Antenna Unit] Fig. 17 is a schematic diagram showing an embodiment of a measurement system. The measurement system 101a shown in Fig. 17 is applied to a multi-camera system using multiple cameras 110. In a multi-camera system, for example, a single subject 2 is simultaneously photographed from various angles by multiple cameras 110 (six cameras 110 in this example) arranged to surround the subject 2. This makes it possible to create a three-dimensional image of the subject 2. Such a system is used, for example, for live streaming of three-dimensional images, volumetric photography, etc.

[0131] To create a stereoscopic image or the like, it is necessary to know the relative position of each camera 110. One method for measuring the relative position of each camera 110 is to use, for example, a laser rangefinder, but measuring the distances when installing the cameras 110 is time-consuming. For example, it is necessary to measure the relative distances between three or more points every time the position of the camera 110 is moved, and it also takes time to perform tasks such as properly irradiating the laser rangefinder.

[0132] Techniques for measuring distances and positioning using wireless communication systems are expected to provide a system that can more easily realize positioning than systems that use laser ranging systems, etc. For example, by installing a wireless communication device capable of UWB wireless communication in each camera 110 of a multi-camera system, it becomes possible to measure the relative distance between each camera 110 with high accuracy. Utilizing this, the relative positions of each camera 110 can be measured easily and accurately.

[0133] However, as described with reference to Figures 6 and 7, the directivity (radiation characteristics) of the antenna of a communication device affects ranging and positioning performance. For example, if the other communication device is located in a direction where the antenna radiation strength is weak, if sufficient radiation strength is not obtained, ranging accuracy may decrease or ranging may not be possible at all. On the other hand, it is practically difficult for users who install each camera 110 to configure an imaging system while always being aware of the antenna directivity. Furthermore, it is necessary to pay attention to the antenna directivity every time the orientation or position of the camera 110 is changed, which leads to a decrease in work efficiency. It is also difficult to make users aware of the antenna directivity itself.

[0134] 17, the antenna unit 100 according to this embodiment is provided on each of a plurality of cameras 110. This constitutes a multi-camera system capable of measuring the relative positions of the cameras 110 using wireless signals.

[0135] The antenna unit 100 fixed to each camera 110 has a radiation characteristic that is approximately uniform in the horizontal direction and is substantially omnidirectional. For example, as shown in Fig. 17, a substantially circular radiation characteristic is realized in the horizontal plane with the camera 110 at the center. Therefore, no matter where the camera 110 is placed or which subject 2 it is directed toward, the measurement system 101 can perform good wireless communication. As a result, the entire system can exhibit good positioning performance.

[0136] Furthermore, even if attention is not paid to the directivity, etc., of the azimuth direction of the antenna unit 100, degradation of communication performance is unlikely to occur. Therefore, even a user who is not a wireless expert can easily assemble the measurement system 101 without degrading the performance of ranging and positioning.

[0137] 18 and 19 are schematic diagrams showing other embodiments of the measurement system.

[0138] The measurement system 101b shown in FIG. 18 is a surveying system that uses an antenna unit 100. In this example, the antenna unit 100 is attached to the tip of a pole 20. The user places the bottom end of the pole 20 at the location to be surveyed, with the antenna unit 100 facing up. For example, by placing the pole 20 at two points between which the distance is to be measured, it becomes possible to measure the distance between the two points. Furthermore, by preparing three or more poles 20 as shown in FIG. 18, it becomes possible to perform relative positioning.

[0139] For example, when surveying using a laser rangefinder, it is necessary to project a laser onto the desired location, but depending on the distance and the shape of the target, it can take a long time just to find the laser's target point. Furthermore, when performing relative positioning, this process must be repeated multiple times. Furthermore, when positioning using directional wireless communications, the antenna's directivity, i.e., the orientation of the communication device, must always be taken into consideration, which can lead to reduced work efficiency and usability.

[0140] In the measurement system 101b, the use of the antenna unit 100 simplifies the work and reduces the number of steps compared to using a laser rangefinder or the like, making it possible to easily measure distances and positioning. Furthermore, simply moving the position of the pole 20 makes it possible to accurately measure positioning and distances. When the antenna unit 100 is attached to the tip of the pole 20, the pole 20 is fixed, for example, to the second end 12 side. Furthermore, if the pole 20 is long, the pole 20 may be fixed to the first end 11 side so that the downward radiation intensity of the wireless signal is increased.

[0141] 19 is a system in which a stationary anchor A is placed and the distance to a tag P is measured around the anchor A. The stationary anchor A (antenna unit 100) is fixed to the tip of a pole 20, for example, and placed at a relatively high position (higher than a human height). Alternatively, the anchor A may be provided on the floor or the like.

[0142] The measurement system 101c is installed, for example, at a landmark indoors. This makes it possible to accurately measure the distance to tags P present around the landmark. This makes it possible to, for example, display the current location at a station or a shopping mall, or provide guidance (navigation) to a destination.

[0143] For example, if an antenna has significant directivity, ranging can only be performed in limited directions. Furthermore, when installing a communication device, the directivity of the antenna must be taken into consideration, making the installation process, including adjustments, cumbersome. In contrast, the measurement system 101c uses the omnidirectional antenna unit 100 to enable ranging in all directions from the ground position, thereby sufficiently expanding the area in which positioning is possible. Furthermore, even when installing the antenna unit 100, a good communication environment can be easily achieved without paying attention to directivity.

[0144] FIG. 20 is a schematic cross-sectional view showing another example of the configuration of an antenna unit. The antenna unit 100d shown in FIG. 20 is installed on an indoor ceiling 3. In this case, the target to which the antenna unit 100d is fixed is the ceiling 3. Generally, it is desirable for the ground plane 31 of the antenna unit 100d to be on the lower side. However, when attaching the antenna unit 100d to the ceiling 3, it is preferable for the ground plane 31 to be on the ceiling side and the antenna element 32 to be on the lower side. This increases the downward radiation intensity and prevents degradation of wireless signal transmission and reception performance. In this case, a ceiling fixing part 55 provided at the second end 12 and fixed to the ceiling 3 is used as the fixing part 50. The ceiling fixing part 55 may be a screw or a fitting mechanism that is fitted into a base or the like provided on the ceiling 3.

[0145] The antenna unit 100d shown in Fig. 20 can be used, for example, as the stationary anchor A shown in Fig. 19. It is also possible to install equipment such as a surveillance camera or a light on the ceiling 3 via the antenna unit 100d. This allows the stationary anchor A to be placed inconspicuously.

[0146] As described above, in the antenna unit 100 according to this embodiment, the antenna section 30 is configured by arranging the antenna element 32 between the first end 11 and the ground plane 31 inside the housing 10. The housing 10 is fixed to a fixed object by the fixing section 50 provided at the first end 11 or the second end 12. This makes it possible to easily introduce an antenna section 30 with reduced bias in directivity, and makes it possible to easily improve ranging and positioning performance.

[0147] Other Embodiments The present technology is not limited to the above-described embodiments, and various other embodiments can be realized.

[0148] Fig. 21 is a schematic diagram showing an example of the configuration of an antenna element. The antenna element 32a shown in Fig. 21A has a conical shape (cone type) as described with reference to Figs. 1 to 3. In the conical antenna element 32a, a curved conductor is arranged that is inclined with respect to the ground plane 31. This makes it possible to broaden the bandwidth of the antenna.

[0149] The antenna element 32b shown in Fig. 21B has a cylindrical shape with one end protruding in a conical shape. The antenna element 32b is arranged along the central axis C with the apex of the cone facing the ground plane 31. In this way, the antenna element 32b is configured as a monocone antenna that combines a conical shape and a cylindrical shape. The antenna element 32c shown in Fig. 21C has a spherical shape. The spherical antenna element 32c is arranged at a distance from the ground plane 31 so that its center passes through the central axis C.

[0150] The antenna elements 32b and 32c can also achieve a broadband, similar to the antenna element 32a. Therefore, by using the antenna elements 32a, 32b, 32c, etc., it becomes possible to efficiently transmit and receive wireless signals in a wide frequency band, such as UWB.

[0151] The antenna element 32d shown in Figure 21D is linear. This is a so-called rod antenna shape, with a linear conductor (rod) arranged along a central axis C. The antenna element 32d has a resonance mode corresponding to its length, and therefore can efficiently transmit and receive wireless signals in a frequency band corresponding to the resonance mode. For example, when using wireless signals with a relatively narrow bandwidth, such as Bluetooth (registered trademark), using the antenna element 32d can improve the efficiency of transmission and reception.

[0152] The antenna element 32e shown in Figure 21E has a planar shape. Here, a conductor with a triangular planar shape is used, but a rectangular or circular conductor may also be used. By using the planar antenna element 32e, it is possible to configure an antenna or the like that has directivity in a certain direction. For example, the antenna element 32e may be used when the direction in which the antenna unit 100 is communicating with a target is predetermined, or when there is a direction in which it is not desired to emit a wireless signal.

[0153] Although the above description has been given of a configuration in which a partition plate supporting the ground plane is provided inside the housing, it is not necessary to provide a partition plate. For example, the ground plane may be used as a structural member to partition the inside of the housing. This allows for a simpler structure of the antenna unit and a lighter weight.

[0154] Furthermore, the window surrounding the antenna unit does not need to surround the entire circumference of the antenna unit (center axis C). For example, metal materials, metal wiring, etc. required for the structure may be partially disposed around the antenna unit. Even in such a case where metal materials are partially disposed, if the amount used is small, the radiation pattern will not be significantly distorted.

[0155] Furthermore, if the radiation pattern of the antenna unit is distorted, the directivity may be clearly indicated by marking the housing so that the direction in which the radiation intensity is weak (or the direction in which the radiation intensity is strong) can be identified. This makes it possible to easily realize a system capable of good wireless communication by adjusting the orientation of the antenna unit 100, for example, based on the marking.

[0156] The antenna unit described above is configured as a communication device equipped with internal elements such as a communication circuit, a battery, etc. However, the present invention is not limited to this, and may be configured as a unit equipped with only an antenna section (antenna element and ground plane) and with an external communication device and battery.

[0157] It is also possible to combine at least two of the features of the present technology described above. That is, the various features described in each embodiment may be arbitrarily combined without distinguishing between the embodiments. Furthermore, the various effects described above are merely examples and are not intended to be limiting, and other effects may also be achieved.

[0158] In the present disclosure, the terms "same," "equal," "orthogonal," etc. are concepts that include "substantially the same," "substantially equal," "substantially orthogonal," etc. For example, they also include states that fall within a predetermined range (e.g., a range of ±10%) based on "completely the same," "completely equal," "completely orthogonal," etc.

[0159] The present technology may also have the following configurations. (1) An antenna unit used for at least one of ranging or positioning using wireless signals, comprising: a housing having a first end and a second end facing each other; an antenna unit having a ground plane disposed within the housing facing the first end and an antenna element disposed between the ground plane and the first end; and a fixing unit provided on at least one of the first end or the second end and fixing the housing to a fixed object. (2) The antenna unit according to (1), further comprising: at least one internal element disposed between the ground plane and the second end and operating the antenna unit. (3) The antenna unit according to (2), wherein the at least one internal element includes a communication circuit that performs wireless communication using the wireless signal via the antenna unit, and a power supply unit that drives the communication circuit. (4) The antenna unit according to any one of (2) or (3), wherein the housing has a partition plate disposed between the first end and the second end and supporting the ground plane, and the at least one internal element is disposed between the partition plate and the second end. (5) The antenna unit according to any one of (2) to (4), wherein the ground plane shields the at least one internal element from the antenna element. (6) The antenna unit according to any one of (2) to (5), wherein the housing has a cylindrical shape centered on a predetermined axis, the antenna element is disposed along the predetermined axis, and the ground plane is disposed so as to be perpendicular to the predetermined axis. (7) The antenna unit according to (6), wherein the housing has a cylindrical shape centered on the predetermined axis. (8) The antenna unit according to any one of (6) and (7), wherein the antenna element and the ground plane are configured to have a rotationally symmetric shape around the predetermined axis.(9) The antenna unit according to any one of (6) to (8), wherein the ground plane is formed to surround the predetermined axis and has an opening through which wiring connecting the antenna element and the internal element passes. (10) The antenna unit according to any one of (1) to (9), wherein the housing has a window formed between the first end and the ground plane to surround the antenna element and allow the radio signal to pass. (11) The antenna unit according to any one of (1) to (10), wherein the housing has a side portion connecting the first end and the second end, and the first end is configured to be detachable from the side portion. (12) The antenna unit according to any one of (1) to (11), wherein the fixing portion is a screw or a screw hole. (13) The antenna unit according to any one of (1) to (12), wherein the fixed object is an image capture device having a screw hole for fixing and a fixed base having a screw for fixing that can be fitted into the screw hole of the image capture device, and the fixing part includes a screw provided at the first end part and fixed to the screw hole of the image capture device, and a screw hole provided at the second end part and fixed to the screw of the fixing base. (14) The antenna unit according to any one of (1) to (13), wherein the fixed object is a ceiling, and the fixing part includes a ceiling fixing part provided at the second end part and fixed to the ceiling. (15) The antenna unit according to any one of (1) to (14), wherein the antenna part is configured as an antenna for ultra wideband wireless communication. (16) The antenna unit according to any one of (1) to (15), wherein the antenna element has any one of a conical shape, a cylindrical shape with one end protruding in a conical shape, a spherical shape, a linear shape, and a planar shape.(17) An antenna device used for at least one of distance measurement and positioning using radio signals, comprising: a housing having a first end and a second end opposite each other; an antenna unit having a ground plane arranged inside the housing opposite the first end and an antenna element arranged between the ground plane and the first end; at least one internal element arranged between the ground plane and the second end to operate the antenna unit; and a fixing part provided on at least one of the first end or the second end to fix the housing to a fixed object. (18) A measurement system that performs at least one of ranging and positioning using radio signals, comprising: at least one reference antenna device whose position coordinates are known; a target antenna device that communicates with the at least one reference antenna device using the radio signals; and a measurement device that performs at least one of ranging and positioning of the target antenna device based on the results of the radio signal communication between the target antenna device and the at least one reference antenna device and the position coordinates of the at least one reference antenna device, wherein at least one of the at least one reference antenna device and the target antenna device is an antenna device having: a housing having a first end and a second end that are opposite to each other; an antenna unit having a ground plane arranged within the housing facing the first end and an antenna element arranged between the ground plane and the first end; at least one internal element that is arranged between the ground plane and the second end and that operates the antenna unit; and a fixing part that is provided at at least one of the first end or the second end and that fixes the housing to a fixed object.

[0160] A, B, C, A1, A2, A3, A4... anchor P... tag 10... housing 11... first end 12... second end 30... antenna section 31... ground plane 32, 32a, 32b, 32c, 32d, 32e... antenna elements 40... internal element 50... fixed section 100, 100a, 100b, 100d... antenna unit 101, 101a, 101b, 101c... measurement system 110... camera 120... tripod

Claims

1. An antenna unit used for at least one of distance measurement and positioning using radio signals, comprising: a housing having a first end and a second end facing each other; an antenna section having a ground plane arranged inside the housing facing the first end and an antenna element arranged between the ground plane and the first end; and a fixing section provided on at least one of the first end or the second end for fixing the housing to a fixed object.

2. An antenna unit according to claim 1, further comprising at least one internal element disposed between said ground plane and said second end for operating said antenna portion.

3. An antenna unit according to claim 2, wherein said at least one internal element includes a communication circuit for performing wireless communication by means of said radio signal via said antenna section, and a power supply section for driving said communication circuit.

4. An antenna unit according to claim 2, wherein the housing has a partition plate disposed between the first end and the second end and supporting the ground plane, and the at least one internal element is disposed between the partition plate and the second end.

5. An antenna unit according to claim 2, wherein said ground plane shields said at least one internal element from said antenna element.

6. An antenna unit according to claim 2, wherein the housing is cylindrical with a predetermined axis as its center, the antenna element is arranged along the predetermined axis, and the ground plane is arranged so as to be perpendicular to the predetermined axis.

7. An antenna unit according to claim 6, wherein said housing is cylindrical and has said predetermined axis as its center.

8. An antenna unit according to claim 6, wherein the antenna element and the ground plane are configured to have a rotationally symmetric shape about the predetermined axis.

9. An antenna unit according to claim 6, wherein the ground plane is formed so as to surround the predetermined axis and has an opening through which wiring connecting the antenna element and the internal element passes.

10. An antenna unit according to claim 1, wherein the housing has a window formed between the first end and the ground plane to surround the antenna element and to allow the radio signal to pass through.

11. An antenna unit as claimed in claim 1, wherein the housing has a side portion connecting the first end and the second end, and the first end is configured to be detachable from the side portion.

12. An antenna unit according to claim 1, wherein the fixing portion is a screw or a screw hole.

13. An antenna unit as described in claim 1, wherein the object to be fixed is a photographing device having a screw hole for fixing, and a fixing base having a screw for fixing that can be fitted into the screw hole of the photographing device, and the fixing part includes a screw provided at the first end and fixed into the screw hole of the photographing device, and a screw hole provided at the second end and fixed to the screw of the fixing base.

14. An antenna unit according to claim 1, wherein the object to be fixed is a ceiling, and the fixing part includes a ceiling fixing part provided at the second end and fixed to the ceiling.

15. An antenna unit according to claim 1, wherein the antenna section is configured as an antenna for ultra-wideband wireless communication.

16. An antenna unit according to claim 1, wherein the antenna element has any one of the following shapes: a cone shape, a cylinder with one end protruding in a conical shape, a sphere shape, a line shape, or a flat shape.

17. An antenna device used for at least one of distance measurement and positioning using radio signals, comprising: a housing having a first end and a second end opposite each other; an antenna unit having a ground plane arranged inside the housing opposite the first end and an antenna element arranged between the ground plane and the first end; at least one internal element arranged between the ground plane and the second end to operate the antenna unit; and a fixing part provided on at least one of the first end or the second end to fix the housing to a fixed object.

18. A measurement system that performs at least one of ranging and positioning using radio signals, comprising: at least one reference antenna device whose position coordinates are known; a target antenna device that communicates with the at least one reference antenna device using the radio signals; and a measurement device that performs at least one of ranging and positioning of the target antenna device based on the results of the radio signal communication between the target antenna device and the at least one reference antenna device and the position coordinates of the at least one reference antenna device, wherein at least one of the at least one reference antenna device and the target antenna device is an antenna device having: a housing having a first end and a second end that are opposed to each other; an antenna unit having a ground plane arranged within the housing facing the first end and an antenna element arranged between the ground plane and the first end; at least one internal element that is arranged between the ground plane and the second end and that operates the antenna unit; and a fixing part provided on at least one of the first end or the second end and that fixes the housing to a fixed object.

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