Antenna device, wireless communication direction detection system, and direction detection method

Abstract

This antenna device comprises a first antenna, a second antenna different from the first antenna, a first selection unit that selects either the first antenna or the second antenna, and an impedance adjustment circuit that has an impedance for re-radiating a radio wave and can be connected to either the first antenna or the second antenna.

Description

Antenna device, wireless communication direction detection system, and direction detection method

[0001] The present technology relates to a technical field of an antenna device having a plurality of antennas that perform wireless communication with other devices, a wireless communication direction detection system, and a direction detection method.

[0002] In recent years, indoor positioning technology has been attracting attention, and methods of measuring distances for positioning using wireless signals such as Bluetooth Low Energy (BLE: Bluetooth is a registered trademark) and Ultra Wide Band (UWB) have been studied and standardization is progressing. One positioning method, for example, is a method of installing anchor devices (base stations) on walls or ceilings and calculating direction information and distance information of a mobile terminal device relative to each anchor device to identify its position (see, for example, Patent Document 1 listed below).

[0003] One method for detecting the direction of a mobile terminal device relative to a base station involves detecting the phase difference between signals received or transmitted by multiple antennas, and then detecting the angle of arrival (Angle of Arrival: AoA) or angle of departure (Angle of Departure: AoD) of the radio waves based on the phase difference.

[0004] Japanese Patent Application Laid-Open No. 2021-100169

[0005] When multiple antennas are used, interference may occur due to re-radiation of radio waves from the non-excited antenna, resulting in a deterioration of radio wave quality. In such cases, connecting a 50 ohm termination resistor to the non-excited antenna can suppress re-radiation of radio waves from the non-excited antenna.

[0006] However, re-radiation of radio waves can occur not only from the antenna on the non-excited side, but also from scatterers located near the antenna.

[0007] The present technology has been made in view of the above circumstances, and aims to suppress degradation of radio wave quality caused by re-radiation of radio waves from scatterers located near the antenna.

[0008] The antenna device according to the present technology includes a first antenna, a second antenna different from the first antenna, a first selection unit that selects either the first antenna or the second antenna, and an impedance adjustment circuit that has an impedance that re-radiates radio waves and is connectable to either the first antenna or the second antenna. As in this configuration, by connecting the impedance adjustment circuit that re-radiates radio waves to the antenna on the non-excitation side, it is possible to re-radiate radio waves from the antenna on the non-excitation side.

[0009] 1 is a block diagram showing an example of a configuration of a positioning system according to an embodiment of the present technology. FIG. 1 is an explanatory diagram of a calculation method for a radio wave arrival angle. FIG. 2 is a functional block diagram of a control unit of an antenna device. FIG. 3 is a diagram showing the relationship between a phase difference and an arrival angle. FIG. 4 is a block diagram showing an example of a configuration of an antenna device according to a first embodiment. FIG. 5 is a block diagram showing an example of a configuration of an antenna device according to a second embodiment. FIG. 6 is a functional block diagram of a control unit of the antenna device. FIG. 7 is a flowchart showing a processing procedure for calibration of the antenna device. FIG. 8 is a flowchart showing angle measurement processing during operation. FIG. 9 is a block diagram showing an example of a configuration of an antenna device according to a first modified example of the second embodiment. FIG. 10 is a block diagram showing an example of a configuration of an antenna device according to a second modified example of the second embodiment. FIG. 11 is a block diagram showing an example of a configuration of an antenna device according to a third modified example of the second embodiment. FIG. 12 is a block diagram showing an example of a configuration of an antenna device according to a fourth modified example of the second embodiment. FIG. 13 is a block diagram showing an example of a configuration of an antenna device according to a fifth modified example of the second embodiment. FIG. 14 is a block diagram showing an example of a configuration of an antenna device according to a third embodiment. FIG. 15 is a block diagram showing an example of a configuration of an antenna device according to a first modified example of the third embodiment. FIG. 16 is a block diagram showing an example of a configuration of an antenna device according to a second modified example of the third embodiment. FIG. 17 is a block diagram showing an example of a configuration of an antenna device according to a third modified example of the third embodiment. Fig. 10 is a block diagram showing an example of the configuration of an antenna device according to another modified example Fig. 11 is a block diagram showing a positioning system including an information processing device in addition to an antenna device and a mobile terminal device.

[0010] Hereinafter, with reference to the accompanying drawings, embodiments according to the present technology will be described in the following order: <1. Configuration example of a positioning system> <2. Relationship between phase difference and angle of arrival> <3. Configuration of an antenna device> <4. Second embodiment> <4-1. Modification of the second embodiment> <5. Third embodiment> <5-1. Modification of the third embodiment> <6. Other modifications> <7. Summary> <8. This technology>

[0011] 1. Configuration Example of Positioning System An example of the configuration of a positioning system S according to the present embodiment is shown in Fig. 1. The positioning system S includes an antenna device 1 of the present technology and a mobile terminal device 2.

[0012] For example, a plurality of antenna devices 1 are provided, and each of them obtains angle information Dang and distance information Ddis by wirelessly communicating with the mobile terminal device 2. At least one of the antenna devices 1 performs positioning of the mobile terminal device 2 using the angle information Dang and distance information Ddis for the mobile terminal device 2 obtained by each antenna device 1. In other words, the antenna device 1 functions as the anchor device (base station) described above.

[0013] Here, the calculation of the angle information Dang indicating the position (direction) of the mobile terminal device 2 relative to the antenna device 1 will be described.

[0014] The angle information Dang is information indicating the direction in which the mobile terminal device 2 is positioned relative to the antenna device 1 .

[0015] The antenna device 1 includes a plurality of antennas, for example, a first antenna Ant1 and a second antenna Ant2.

[0016] The mobile terminal device 2 also includes a terminal antenna AntT.

[0017] 2 , the angle of arrival Ang1, which is the angle between the front direction (i.e., the up-down direction in the figure), which is a direction perpendicular to the direction in which the first antenna Ant1 and the second antenna Ant2 are aligned, and the direction in which the radio waves arrive, can be expressed by the following equation [1]. Note that the constant Gap in equation [1] is the gap Gap that indicates the distance between the first antenna Ant1 and the second antenna Ant2. Furthermore, the constant Ds in equation [1] is the distance difference Ds that indicates the difference between the distance between the terminal antenna AntT of the mobile terminal device 2 and the first antenna Ant1 and the distance between the terminal antenna AntT of the mobile terminal device 2 and the second antenna Ant2.

[0018] Ang1=arcsin(Ds / Gap)...Formula [1]

[0019] The distance difference Ds can be expressed by the following equation [2]. Note that the constant c in equation [2] is the speed of light c. The constant w in equation [2] is the angular frequency w of the carrier wave. Furthermore, the variable Phs is the phase difference Phs between the signals received by the first antenna Ant1 and the second antenna Ant2.

[0020] Ds=(c・Phs / w)...Formula [2]

[0021] That is, as can be seen from equations [1] and [2], the angle of arrival Ang1 can be obtained by calculating the phase difference Phs.

[0022] The phase difference Phs is the difference between the signal phase Pha obtained by receiving the measurement signal transmitted from the terminal antenna AntT at the first antenna Ant1 and the signal phase Phb obtained by receiving the measurement signal transmitted from the terminal antenna AntT at the second antenna Ant2.

[0023] The signal phase Pha is calculated using the following equation [3], where the I-channel and Q-channel signals obtained by receiving a measurement signal that has been subjected to a predetermined modulation via the first antenna Ant1 are “Ia” and “Qa”, respectively.

[0024] Pha=arctan(Qa / Ia)...Formula [3]

[0025] Similarly, the signal phase Phb is calculated using the following equation [4], where "Ib" and "Qb" are the I-channel and Q-channel signals obtained by receiving a measurement signal that has been modulated in a predetermined manner via the second antenna Ant2.

[0026] Phb=arctan(Qb / Ib)...Formula [4]

[0027] The distance information Ddis between the antenna device 1 and the mobile terminal device 2, specifically the distance between the antennas of both devices, may be calculated using, for example, a phase-based method.

[0028] In the phase-based method, wireless communication is performed while changing the frequency between the antenna device 1 and the mobile terminal device 2. Specifically, a signal phase Ph12 obtained by transmitting a measurement signal from the antenna device 1 to the mobile terminal device 2 in a certain frequency band and a signal phase Ph21 obtained by transmitting a measurement signal from the mobile terminal device 2 to the antenna device 1 are used to calculate a signal phase Ph0 of the signal propagation path for that frequency band.

[0029] The signal phase Ph0 is obtained for each frequency band using the signal phase Ph12 and the signal phase Ph21 for each frequency band. The phase characteristics of the signal propagation path with respect to frequency obtained in this manner indicate that the greater the slope of the signal phase Ph0 with respect to frequency, the greater the distance between the antenna device 1 and the mobile terminal device 2, and the smaller the slope, the closer the distance between the antenna device 1 and the mobile terminal device 2.

[0030] Therefore, distance information Ddis between the antenna device 1 and the mobile terminal device 2 can be obtained based on the gradient of the phase characteristic with respect to the frequency of the signal propagation path.

[0031] There are other possible methods for calculating the distance information Ddis. For example, the distance information Ddis may be calculated by providing either the antenna device 1 or the mobile terminal device 2 with a distance measurement sensor such as a Time of Flight (ToF) sensor or a radar sensor, or a distance measurement sensor that measures distance through UWB communication.

[0032] Next, measurement (angle measurement) of the arrival angle Ang1 using the phase-based method will be described. For example, a signal phase Ph0 is calculated by performing round-trip communication in a certain frequency band between a pair of a first antenna Ant1 in the antenna device 1 and a terminal antenna AntT in the mobile terminal device 2. Similarly, a signal phase Ph0 is calculated by performing round-trip communication in the same frequency band between a pair of a second antenna Ant2 and a terminal antenna AntT.

[0033] Then, the arrival angle Ang1 can be calculated by regarding the difference between the signal phase Ph0 for the pair of the first antenna Ant1 and the terminal antenna AntT and the signal phase Ph0 for the pair of the second antenna Ant2 and the terminal antenna AntT as the above-mentioned phase difference Phs.

[0034] The antenna device 1 is configured as a computer device including a microcomputer having, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The CPU serving as a control unit 3 of the antenna device 1 executes a predetermined program to function as an angle calculation unit F1, a distance calculation unit F2, and a selection instruction unit F3 as shown in FIG. 3 .

[0035] The angle calculation unit F1 calculates the arrival angle Ang1 of the radio wave using the above-mentioned method, and the distance calculation unit F2 calculates distance information Ddis between the antenna device 1 and the mobile terminal device 2 (e.g., the distance between the antennas of both devices) using the above-mentioned method.

[0036] The selection instruction unit F3 selects one circuit when there are multiple circuits connectable to the first antenna Ant1 or the second antenna Ant2. Specific examples of multiple circuits connectable to antennas will be described later. The selection instruction by the selection instruction unit F3 is given to, for example, a switch element.

[0037] 2. Relationship Between Phase Difference and Arrival Angle The phase difference Phs described above is used to calculate the arrival angle Ang1, and ideally has the relationship shown by the solid line in Fig. 4. The relationship shown by the solid line in Fig. 4 is the phase characteristic of the arrival angle Ang1.

[0038] However, if metal is used on the walls, ceiling, or floor near the antenna device 1, or in the housing of the antenna device 1, that is, if a scatterer 100 is present near the first antenna Ant1 or the second antenna Ant2, the phase characteristics of the arrival angle Ang1 will differ from the ideal state due to re-radiation of radio waves from the scatterer 100 (see, for example, the dashed line in Figure 4).

[0039] If the phase characteristics of the arrival angle Ang1 differ from the ideal state, the accuracy of the calculated arrival angle Ang1 decreases.

[0040] The antenna device 1 has a structure for solving this problem, which will be specifically described below.

[0041] 3. Configuration of Antenna Device An example configuration of the antenna device 1 according to the first embodiment will be described with reference to Fig. 5. The antenna device 1 includes a patch antenna serving as a first antenna Ant1 and a patch antenna serving as a second antenna Ant2.

[0042] The antenna device 1 is configured to include a circuit board CB that is different from the board on which the first antenna Ant1 and the second antenna Ant2 are mounted. Note that the first antenna Ant1 and the second antenna Ant2 may be mounted on the circuit board CB.

[0043] The circuit board CB includes a first selection unit 5 that selects an antenna on the excitation side, an RFIC (Radio Frequency Integrated Circuit) 6 connected to the first selection unit 5, and a digital IC 7 connected to the RFIC 6.

[0044] The circuit board CB also includes a connection selection section 8 connected between each antenna and the first selection section 5 , and a transmission line stub 9 connected to the connection selection section 8 .

[0045] Here, the connection selection unit 8 connected between the first antenna Ant1 and the first selection unit 5 is referred to as a connection selection unit 8A, and the transmission line stub 9 connected to the connection selection unit 8A is referred to as a transmission line stub 9A.

[0046] Similarly, the connection selection unit 8 connected between the second antenna Ant2 and the first selection unit 5 is referred to as a connection selection unit 8B, and the transmission line stub 9 connected to the connection selection unit 8B is referred to as a transmission line stub 9B.

[0047] The RFIC 6 is configured to include, for example, a BPF (Band Pass Filter) and a mixer that function as a transmitter in wireless communication, an LNA (Low Noise Amplifier), a mixer, a BPF, and a VGA (Variable Gain Amplifier) ​​that function as a receiver, a frequency synthesizer that supplies frequencies used during transmission and reception, and an RF (Radio Frequency) switch that switches whether the transmitter or receiver is connected to an antenna.

[0048] The mixer in the transmitter mixes a signal in a specific frequency band supplied from the BPF with a local oscillation frequency supplied from a frequency synthesizer, thereby converting the signal into a transmission frequency for wireless communication.

[0049] The LNA, which functions as a receiver, amplifies the RF signal received from the antenna on the excitation side, and the mixer in the receiver mixes the signal supplied from the LNA with a local oscillation frequency supplied from a frequency synthesizer to obtain I-channel and Q-channel signals.

[0050] The BPF and VGA serving as the receiving section are provided for the I channel and the Q channel, respectively, and the VGA functions as an analog variable gain amplifier that adjusts the gain for a signal in a specific frequency band supplied from the BPF.

[0051] The RFIC 6 mainly processes analog signals, while the digital IC 7 processes digital signals. Therefore, a DAC (Digital to Analog Converter) or an ADC (Analog to Digital Converter) is provided in either the RFIC 6 or the digital IC 7.

[0052] The digital IC 7 is configured to include, for example, a microcomputer having a CPU, ROM, RAM, etc., and functions as the above-mentioned control unit 3. That is, the digital IC 7 calculates the phase characteristics with respect to the frequency of the above-mentioned signal propagation path, thereby calculating the distance information Ddis and the angle information Dang.

[0053] The digital IC 7 also performs modulation processing on the data to be transmitted using a modulator, and supplies the resulting signal to the RFIC 6. Furthermore, the digital IC 7 performs processing to demodulate the received data based on the data of the I-channel and Q-channel signals, using the digital signal supplied from the RFIC 6 or a digital signal obtained by converting an analog signal supplied from the RFIC 6.

[0054] The first selector 5 is configured as a switch for switching between the first antenna Ant1 and the second antenna Ant2 as antennas to be used for communication. That is, the first selector 5 functions as a selector for selecting the antenna on the excitation side from the first antenna Ant1 and the second antenna Ant2. The first selector 5 is, for example, an SPDT (Single Pole Double Throw) switch.

[0055] The connection selection unit 8 is a switch that switches whether or not to connect the transmission line stub 9 to each antenna. Specifically, the connection selection unit 8 connects the transmission line stub 9 to the antenna on the non-excitation side (the second antenna Ant2 in FIG. 5 ). Also, the connection selection unit 8 disconnects the transmission line stub 9 from the antenna on the excitation side (the first antenna Ant1 in FIG. 5 ).

[0056] The connection selection unit 8 is, for example, an SPST (Single Pole Single Throw) switch.

[0057] As shown in FIG. 5, radio waves 200A arrive at the antenna device 1 from the terminal antenna AntT.

[0058] If a scatterer 100 is present near the first antenna Ant1 or the second antenna Ant2, the scatterer 100 that receives the radio wave 200A re-radiates a radio wave 200B.

[0059] When the transmission line stub 9 is connected to the antenna on the non-excited side via the connection selection unit 8, radio waves 200C shown by the dashed line are re-radiated from the antenna on the non-excited side (the second antenna Ant2 in FIG. 5), as shown by the dashed line in FIG.

[0060] By adjusting the radio wave 200C so that the radio wave 200B and the radio wave 200C cancel each other out, it is possible to suppress deterioration of the communication state between the excitation side antenna and the terminal antenna AntT, and improve the angle measurement accuracy and distance measurement accuracy.

[0061] The transmission line stub 9 connected to the antenna on the non-excited side can be considered as an adjustment circuit that adjusts impedance. That is, the transmission line stub 9 is a circuit that adjusts impedance so that re-radiation occurs from the antenna on the non-excited side. The impedance adjustment circuit can also be considered as a phase adjustment circuit that adjusts the phase of the radio wave 200C re-radiated from the antenna on the non-excited side. Therefore, the impedance of the impedance adjustment circuit is set to a value less than 50 ohms or greater than 50 ohms.

[0062] The transmission line stub 9 may be an open stub 91 or a short stub 92. The transmission line stub 9 is formed as, for example, a microstrip line.

[0063] 4. Second Embodiment The antenna device 1 in the first embodiment is configured to include a connection selection unit 8 that selects whether or not to connect an impedance adjustment circuit to the antenna on the non-excited side. The antenna device 1 in the second embodiment has a configuration that allows selection of an impedance adjustment circuit to be connected to the antenna on the non-excited side from among a plurality of impedance adjustment circuits.

[0064] 6 shows an example of the antenna device 1. The antenna device 1 includes a second selection unit 10 for selecting from a plurality of impedance adjustment circuits, and two types of transmission line stubs 9 as the plurality of impedance adjustment circuits, specifically, an open stub 91 and a short stub 92.

[0065] The second selector 10 on the side of the first antenna Ant1 is referred to as a second selector 10A, and the second selector 10 on the side of the second antenna Ant2 is referred to as a second selector 10B.

[0066] The open stub 91 and short stub 92 connected to the first antenna Ant1 are respectively referred to as an open stub 91A and a short stub 92A. Similarly, the open stub 91 and short stub 92 connected to the second antenna Ant2 are respectively referred to as an open stub 91B and a short stub 92B.

[0067] In the following description, for similar configurations, the symbol indicating the configuration on the first antenna Ant1 side will have an "A" suffix, and the symbol indicating the configuration on the second antenna Ant2 side will have a "B" suffix.

[0068] The second selection unit 10 is, for example, an SPDT switch. The second selection unit 10 selects an impedance adjustment circuit to be connected to the antenna on the non-excited side from an open stub 91 or a short stub 92 depending on the connection state.

[0069] The open stub 91 and the short stub 92 have different impedances, and therefore the phase of the radio wave 200C re-radiated from the antenna on the non-excited side is different. Therefore, in the antenna device 1, it is preferable to select an impedance adjustment circuit for effectively canceling the radio wave 200B re-radiated from the scatterer 100 and connect it to the antenna on the non-excited side.

[0070] The control unit 3 of the antenna device 1 has a calibration function F4 for selecting one of a plurality of impedance adjustment circuits (see FIG. 7).

[0071] An example of the processing executed by the control unit 3 to realize the calibration function F4 is shown in Fig. 8. Note that the blocks indicated by dashed lines in the figure are processing (procedures) executed by a party other than the control unit 3, including, for example, processing that is performed manually.

[0072] First, in step S10, an operator who performs calibration installs the antenna device 1 on a wall, ceiling, floor, or the like of a target space.

[0073] Next, in step S11, the worker installs the mobile terminal device 2 in a predetermined position. At this time, since the positional relationship between the antenna device 1 and the mobile terminal device 2 is known, the ideal value (correct value) of the phase difference Phs between the signals received by the first antenna Ant1 and the second antenna Ant2 is automatically determined.

[0074] With the antenna device 1 and the mobile terminal device 2 installed in the target space, the control unit 3 selects one impedance adjustment circuit in step S101. For example, in the example shown in Fig. 6, either the open stub 91 or the short stub 92 is selected as the impedance adjustment circuit. The selected impedance adjustment circuit is connected to the antenna on the non-excited side in the subsequent wireless communication.

[0075] In step S102, the control unit 3 performs wireless communication with the mobile terminal device 2 and calculates the phase difference Phs.

[0076] In step S103, the control unit 3 compares the ideal value of the phase difference Phs with the actually measured value and calculates the difference.

[0077] In step S104, the control unit 3 determines whether or not the processes in steps S101 to S103 have been executed for all impedance adjustment circuits. That is, in the example shown in Fig. 6, it determines whether or not the ideal value and the actually measured value of the phase difference Phs have been compared for both the open stub 91 and the short stub 92.

[0078] If there is an untested impedance adjustment circuit, the control unit 3 determines No in step S104 and selects an untested impedance adjustment circuit in step S101.

[0079] On the other hand, if there is no untested impedance adjustment circuit, the control unit 3 judges Yes in step S104 and proceeds to step S105, selects the impedance adjustment circuit whose phase difference Phs is closest to the ideal value, and ends the calibration process.

[0080] 8 was performed with the mobile terminal device 2 placed in a predetermined position, the series of processes shown in Fig. 8 may be performed multiple times while changing the position of the mobile terminal device 2, and the impedance adjustment circuit whose phase difference Phs is closest to the ideal value may be selected regardless of the position of the mobile terminal device 2. In this case, the impedance adjustment circuit whose phase difference Phs has the smallest worst value of the difference from the ideal value may be selected in step S105, or the impedance adjustment circuit whose phase difference Phs has the smallest average value of the difference from the ideal value may be selected in step S105.

[0081] For example, when the position (direction) of the mobile terminal device 2 relative to the antenna device 1 is limited, such as when a user carrying the mobile terminal device 2 enters a room only through the entrance or when the user walks down a passage from one direction, calibration is performed in one direction using the method shown in Fig. 8. This makes it possible to reduce the processing load of the calibration and shorten the calculation time.

[0082] On the other hand, when the position and direction of the mobile terminal device 2 relative to the antenna device 1 are in a wide range, omnidirectional calibration is performed by performing a series of processes shown in Fig. 8 while changing the position of the mobile terminal device 2. This makes it possible to measure angles with high accuracy regardless of the position of the mobile terminal device 2.

[0083] Next, an example of processing executed by the control unit 3 to measure the angle of the direction in which the mobile terminal device 2 is located when the mobile terminal device 2 actually enters the angle measurement range is shown in Fig. 9. Note that the example shown in Fig. 9 is an example in which the direction in which the mobile terminal device 2 is located is limited, or the initial position of the mobile terminal device 2 when it enters the angle measurement range is limited.

[0084] 9 , the control unit 3 determines whether or not the mobile terminal device 2 is located within the wireless communication range of the antenna device 1. This determination process may be performed by detecting the radio waves 200A emitted by the mobile terminal device 2, or may be performed using the presence or absence of a reply (such as an ACK response) to the transmission from the antenna device 1.

[0085] If it is determined that the mobile terminal device 2 is not present within the wireless communication range, the control unit 3 determines No in step S201 and repeats the process of step S201.

[0086] On the other hand, if it is determined that the mobile terminal device 2 is present within the wireless communication range, the control unit 3 determines Yes in step S201, proceeds to step S202, and selects an impedance adjustment circuit with high angle measurement accuracy in the predetermined direction, i.e., an impedance adjustment circuit that can accurately determine the initial position of the mobile terminal device 2 within the wireless communication range.

[0087] In step S203, the control unit 3 performs wireless communication with the mobile terminal device 2 to calculate angle information Dang, that is, the angle of arrival Ang1.

[0088] In step S204, the control unit 3 determines whether the calculated angle information Dang is outside the high-accuracy range. For example, if the antenna device 1 can detect with high accuracy the mobile terminal device 2 whose arrival angle Ang1 is between −60 degrees and 60 degrees, the control unit 3 determines No in step S204 if the arrival angle Ang1 is between −60 degrees and 60 degrees, and determines Yes in step S204 if the arrival angle Ang1 is outside the range.

[0089] If the determination in step S204 is No, the control unit 3 returns to step S203 again and calculates the latest arrival angle Ang1.

[0090] On the other hand, if the determination in step S204 is Yes, the control unit 3 proceeds to step S205, where it selects an impedance adjustment circuit that can measure the arrival angle Ang1 with high accuracy outside the range of −60 degrees to 60 degrees. At this time, different impedance adjustment circuits may be selected when the arrival angle Ang1 is outside the −60 degree side and when it is outside the 60 degree side.

[0091] After selecting a new impedance adjustment circuit in step S205, the control unit 3 calculates the latest arrival angle Ang1 in step S203.

[0092] In this way, the control unit 3 can measure the angle according to the position (direction) of the mobile terminal device 2 relative to the antenna device 1 by executing the series of processes shown in FIG.

[0093] <4-1. Modification of the Second Embodiment> Next, a modification of the second embodiment will be described.

[0094] 10 shows a first modified example of the antenna device 1. The antenna device 1 according to the first modified example shares part of the impedance adjustment circuit, and more specifically, it is possible to select whether or not to ground the termination via a third selection unit 11 at the stage subsequent to the transmission line stub 9.

[0095] Specifically, a transmission line stub 9 is connected to the connection selection unit 8, and a third selection unit 11 is further connected to the transmission line stub 9. This makes it possible to select whether the transmission line stub 9 is provided as an open stub 91 or a short stub 92.

[0096] In the example shown in FIG. 10, an SPDT switch is used as the third selection unit 11, but the present invention is not limited to this and an SPST switch may also be used.

[0097] According to the configuration of the first modified example, some of the circuit configuration is shared rather than providing both an open stub 91 and a short stub 92, so the mounting area on the board can be reduced and the circuit board CB can be made smaller.

[0098] 11 shows a second modified example of the antenna device 1. The antenna device 1 according to the second modified example includes a variable-length transmission line stub 12 as an impedance adjustment circuit.

[0099] The variable-length transmission line stub 12 is configured such that transmission lines 13 and switches 14 are alternately connected. In the example shown in Fig. 11, two switches 14 are inserted between three transmission lines 13. The switches 14 are, for example, SPST switches.

[0100] By switching the ON / OFF states of the two switches 14, the length of the wiring as the variable-length transmission line stub 12 connected to the connection selection unit 8 can be changed, and the phase of the radio wave 200C can be changed.

[0101] Variable-length transmission-line stubs 12 (transmission-line stubs 9) with different lengths according to the state of switch 14 can be regarded as different impedance adjustment circuits. Therefore, by sequentially selecting variable-length transmission-line stubs 12 with different lengths each time the process of step S101 in Fig. 8 is executed, in other words, by changing the state of switch 14, it is possible to identify the length of variable-length transmission-line stub 12 that allows for highly accurate angle measurement.

[0102] 12 shows a third modified example of the antenna device 1. The antenna device 1 according to the third modified example is provided with an RF cable 15 instead of the transmission line stub 9 formed as a microstrip line.

[0103] Unlike the microstrip line pre-mounted on the circuit board CB, the RF cable 15 can be added or changed later. That is, after the antenna device 1 is installed, the RF cable 15 can be cut to a length that optimizes the phase of the radio wave 200C, thereby making it possible to suitably suppress the radio wave 200B.

[0104] 13 shows a fourth modified example of the antenna device 1. In the antenna device 1 according to the fourth modified example, a capacitor 16 is connected to the connection selection section 8 instead of the transmission line stub 9.

[0105] Even when the capacitor 16 is used as an impedance adjustment circuit, the phase of the radio wave 200C can be changed, so that the radio wave 200B can be suppressed.

[0106] The same effect can be obtained by using a coil 17 or a resistor 18 other than 50 ohms as an impedance adjustment circuit instead of the capacitor 16.

[0107] 14 shows a fifth modified example of the antenna device 1. In the antenna device 1 according to the fifth modified example, a second selection unit 10, which is an SP4T switch, is connected to the connection selection unit 8, and a transmission line stub 9, a capacitor 16, a coil 17, and a resistor 18 are connected to the respective outputs of the second selection unit 10.

[0108] That is, in the antenna device 1 according to this modification, one of four options can be selected as the impedance adjustment circuit, which allows the phase of the radio wave 200C to be varied in a variety of ways, thereby effectively suppressing the radio wave 200B, the phase of which varies depending on the installation location of the antenna device 1.

[0109] The impedance adjustment circuit may include a plurality of types of capacitors 16, coils 17, and resistors 18. For example, the impedance adjustment circuit may be configured to be able to select one from a plurality of types of resistors 18 having different resistance values.

[0110] Furthermore, it is not necessary to provide all four types of impedance adjustment circuits shown in FIG. 14 ; for example, a configuration in which only the capacitor 16 and the coil 17 are selectable, or a configuration in which only the coil 17 and the resistor 18 are selectable, may be used.

[0111] 5. Third Embodiment The antenna device 1 according to the third embodiment has a configuration in which, in addition to the impedance adjustment circuit connected to the antenna on the non-excited side, a 50 ohm termination circuit 19 for preventing re-radiation of the radio wave 200C can be selected. An example is shown in FIG. 15 .

[0112] A transmission line stub 9 is connected to the connection selection unit 8 , and a third selection unit 11 is further connected to the transmission line stub 9 .

[0113] The third selection unit 11 is, for example, an SPDT switch, one output of which is open and the other output of which is connected to a 50 ohm termination circuit 19. Note that an SPST switch may also be used as the third selection unit 11.

[0114] In this way, by making the 50 ohm termination circuit 19 selectable, when there is no scatterer 100 near the first antenna Ant1 and the second antenna Ant2 and there is no re-radiation of the radio waves 200B, the radio waves 200C radiated from the antenna on the non-excitation side can be reduced, thereby improving the angle measurement accuracy and ranging accuracy.

[0115] <5-1. Modification of the Third Embodiment> Next, a modification of the third embodiment will be described.

[0116] Fig. 16 shows a first modified example of the antenna device 1. The antenna device 1 according to the first modified example has a configuration in which a second selection unit 10 configured as an SPDT switch is disposed between the connection selection unit 8 and the transmission line stub 9 in the configuration shown in Fig. 5, and the transmission line stub 9 is connected to one output of the second selection unit 10 and a 50 ohm termination circuit 19 is connected to the other output.

[0117] This makes it possible to select whether or not to re-radiate the radio wave 200C from the antenna on the non-excitation side, or to select the strength of the radio wave 200C.

[0118] Fig. 17 shows a second modified example of the antenna device 1. The antenna device 1 according to the second modified example has a configuration in which a 50 ohm termination circuit 19 can be selected as the circuit connected to the antenna on the non-excited side in the configuration shown in Fig. 11.

[0119] Specifically, the antenna device 1 has a configuration in which a second selection section 10 is placed between the connection selection section 8 and the variable-length transmission line stub 12, the variable-length transmission line stub 12 is connected to one output of the second selection section 10, and a 50 ohm termination circuit 19 is connected to the other output.

[0120] 18 shows a third modified example of the antenna device 1. The antenna device 1 according to the third modified example has a configuration in which a 50 ohm termination circuit 19 can be selected as the circuit connected to the antenna on the non-excited side in the configuration shown in FIG.

[0121] Specifically, the antenna device 1 has a configuration in which a second selection unit 10 is placed between the connection selection unit 8 and the RF cable 15, the RF cable 15 is connected to one output of the second selection unit 10, and a 50 ohm termination circuit 19 is connected to the other output.

[0122] 19 shows a fourth modified example of the antenna device 1. The antenna device 1 according to the fourth modified example has a configuration in which a 50 ohm termination circuit 19 can be selected as the circuit to be connected to the antenna on the non-excited side in the configuration shown in FIG.

[0123] Specifically, the antenna device 1 has a configuration in which a second selection unit 10 is placed between the connection selection unit 8 and the capacitor 16, the capacitor 16 is connected to one output of the second selection unit 10, and a 50 ohm termination circuit 19 is connected to the other output.

[0124] It is also possible to adopt a configuration in which the capacitor 16 in the configuration shown in FIG. 19 is replaced with a coil 17 or a resistor 18, or a configuration in which the second selection unit 10 is replaced with an SPnT switch and a 50 ohm termination circuit 19 is connected to each output together with the capacitor 16, the coil 17, the resistor 18, and the transmission line stub 9.

[0125] Regardless of whether the antenna device 1 has the configuration shown in the third embodiment or its modified example, as described above, if the scatterer 100 is not present in the vicinity of the antenna, it is possible to suppress the re-emission of the radio waves 200C by connecting the 50 ohm termination circuit 19 to the antenna on the non-excited side, thereby improving the angle measurement accuracy and ranging accuracy.

[0126] 6. Other Modifications In the above-described examples, a circuit that can be connected to the first antenna Ant1 and a circuit that can be connected to the second antenna Ant2 are provided separately. However, since each circuit is connected to only the non-excited antenna of the first antenna Ant1 or the second antenna Ant2, each circuit may be shared.

[0127] A specific description will be given with reference to Fig. 20. Fig. 20 is a modification of the first embodiment shown in Fig. 5. As shown in the figure, the configuration shown in Fig. 20 eliminates the connection selection unit 8B and transmission line stub 9B in Fig. 5, and provides a connection selection unit 8 in place of the connection selection unit 8A.

[0128] Furthermore, while the connection selection unit 8A is an SPST switch, the connection selection unit 8 shown in Fig. 20 is an SPDT switch. The connection selection unit 8 configured as an SPDT switch has a transmission line stub 9 connected to the switch contact, one of the two outputs of which is connected to the first antenna Ant1 and the other output of which is connected to the second antenna Ant2.

[0129] That is, the connection selection unit 8, which is an SPDT switch, has the function of selecting the connection destination of the impedance adjustment circuit from the first antenna Ant1 and the second antenna Ant2.

[0130] Furthermore, since the circuits that were previously provided for each antenna can be consolidated into one, it is possible to reduce the cost of the mounted components, the mounting area, and the size of the circuit board CB.

[0131] Similar substitutions can be adopted in the above-described embodiments and modifications.

[0132] The positioning system S described above includes only the antenna device 1 and the mobile terminal device 2, but is not limited to this and may include the antenna device 1, the mobile terminal device 2, and the information processing device 20 (see FIG. 21).

[0133] The information processing device 20, for example, performs part of the functions of the angle calculation unit F1 and the distance calculation unit F2 among the angle calculation unit F1, the distance calculation unit F2, and the calibration function F4 included in the antenna device 1 described above.

[0134] Specifically, the information processing device 20 receives information on the phase difference Phs from each antenna device 1 and performs a process of calculating the angle and the distance. The information processing device 20 may also perform a process of specifying the two-dimensional or three-dimensional position of the mobile terminal device 2 using the angle information Dang and the distance information Ddis for the multiple antenna devices 1.

[0135] The information processing device 20 may be a server device.

[0136] In the above-described examples, a configuration has been shown in which the radio waves 200B re-radiated from the scatterer 100 is suppressed when the antenna device 1 receives the radio waves 200A. However, the present invention is not limited to this, and a similar configuration can be used for the purpose of improving the communication quality when transmitting radio waves from the antenna device 1.

[0137] For example, when radio waves are transmitted from the first antenna Ant1 of the antenna device 1 to the mobile terminal device 2, the transmitted radio waves may be re-radiated by the scatterer 100, resulting in the effects of multipath. In such a case, the effects of multipath can be reduced by re-radiating radio waves from the second antenna Ant2, which is the non-excitation antenna, so as to cancel out the radio waves re-radiated from the scatterer 100.

[0138] The first antenna Ant1 and the second antenna Ant2 are patch antennas. A patch antenna has directivity in one direction in the thickness direction, making it difficult to receive radio waves from the opposite direction in the thickness direction and reducing the influence of multipath. Therefore, the patch antenna can be suitably used as the first antenna Ant1 and the second antenna Ant2.

[0139] However, other antennas, such as a monopole antenna, may be used as the first antenna Ant1 and the second antenna Ant2. In this case, various antennas can be treated equivalently to patch antennas by providing a reflector or the like near the antenna that blocks radio waves from a specific direction.

[0140] 7. Summary As described in the various embodiments and modifications above, the antenna device 1 includes a first antenna Ant1, a second antenna Ant2 different from the first antenna Ant1, a first selector 5 that selects either the first antenna Ant1 or the second antenna Ant2, and an impedance adjustment circuit that has an impedance that re-radiates radio waves and is connectable to either the first antenna Ant1 or the second antenna Ant2. If the antenna device 1 itself or an object around the antenna device 1 becomes a scatterer 100, the radio wave quality may deteriorate due to re-radiation of radio waves 200B from the scatterer 100. As in the present configuration, by connecting an impedance adjustment circuit that has an impedance that re-radiates radio waves to either the first antenna Ant1 or the second antenna Ant2, it becomes possible to re-radiate radio waves 200C from the antenna on the non-excited side, for example. That is, by setting the impedance adjustment circuit so that the re-radiation from the scatterer 100 and the re-radiation from the antenna cancel each other out, it is possible to suppress degradation of radio wave quality in wireless communication.

[0141] As explained with reference to Fig. 5 etc., it is desirable that the impedance of the impedance adjustment circuit in the antenna device 1 is less than 50 ohms or greater than 50 ohms, which makes it possible to suitably re-radiate from the antenna radio waves 200C that cancel out the radio waves 200B re-radiated from the scatterer 100.

[0142] 5 and the like, the first selection unit 5 in the antenna device 1 may select one of the first antenna Ant1 and the second antenna Ant2 as the excitation side antenna in wireless communication, and the impedance adjustment circuit may be connectable to the non-excitation side antenna of the first antenna Ant1 and the second antenna Ant2 that was not selected by the first selection unit 5. This makes it possible to re-radiate the radio wave 200C for canceling out the radio wave 200B from the non-excitation side antenna, thereby suppressing a decrease in communication quality of wireless communication using the excitation side antenna.

[0143] As described with reference to Figures 16 to 19, the antenna device 1 includes a second selection unit 10 disposed between the non-excited antenna and the impedance adjustment circuit, and a circuit (50 ohm termination circuit 19) having a 50 ohm termination resistor and connectable to the non-excited antenna. The second selection unit 10 may select either the circuit (50 ohm termination circuit 19) having the 50 ohm termination resistor or the circuit connected from the impedance adjustment circuit to the non-excited antenna. This allows the non-excited antenna to be connected to the 50 ohm termination circuit 19 when a scatterer 100 is not present around the antenna or when re-radiation of radio waves 200B from the scatterer 100 is small. This suppresses re-radiation from the non-excited antenna and prevents degradation of radio wave quality. Note that the impedance adjustment circuit in the antenna device 1 may be a transmission line stub 9. This allows a simple structure to be realized for re-radiating radio waves 200C from the non-excited antenna to cancel re-radiation of radio waves 200B from the scatterer 100.

[0144] 5 and the like, the transmission line stub 9 in the antenna device 1 may be formed as a microstrip line. By forming the microstrip line in advance on the circuit board CB, it is possible to reduce manufacturing costs.

[0145] As described with reference to Fig. 12, Fig. 18, etc., the transmission line stub 9 in the antenna device 1 may be formed as an RF cable 15. This makes it possible to retrofit the transmission line stub 9 as the RF cable 15. This makes it easy to change the length of the RF cable 15, and it becomes possible to change the re-radiation characteristics of the radio wave 200C from the antenna on the non-excitation side. This makes it possible to suitably cancel the re-radiation of the radio wave 200B from the scatterer 100.

[0146] As described with reference to Figures 11 and 17, the transmission line stub 9 in the antenna device 1 may be configured to be switchable in length. That is, the antenna device 1 may include a variable-length transmission line stub 12 as an impedance adjustment circuit. The transmission line stub 9 (variable-length transmission line stub 12) with switchable length is realized, for example, by configuring a plurality of transmission lines 13 to be connectable with a switch. This makes it possible to change the re-radiation characteristics from the antenna on the non-excited side, making it possible to match them to the re-radiation characteristics from the scatterer 100, and making it possible to suitably cancel re-radiation from the scatterer 100.

[0147] As described with reference to Fig. 6 and other figures, the antenna device 1 may be provided with an open stub 91 and a short stub 92 as the transmission line stubs 9, and may be provided with a second selector 10 that selects the circuit to be connected to the non-excited antenna from the open stub 91 or the short stub 92. This makes it possible to change the re-radiation characteristics from the non-excited antenna. Therefore, it is possible to change the characteristics of the radio waves 200C re-radiated from the non-excited antenna to match the re-radiation characteristics from the scatterer 100, and it is possible to suitably cancel the re-radiation from the scatterer 100.

[0148] As described with reference to FIG. 10 and other figures, the antenna device 1 may include a third selection unit 11 that selects whether to ground the transmission line stub 9. The second selection unit 10 and the third selection unit 11 may be used together. Specifically, the second selection unit 10 may be a switch that selects between the transmission line stub 9 and the 50-ohm termination circuit 19, and the third selection unit 11 may be a switch that selects whether the transmission line stub 9 is an open stub 91 or a short stub 92 when the transmission line stub 9 is selected. This makes it possible to change the characteristics of the radio wave 200C re-radiated from the antenna on the non-excited side to match the re-radiation characteristics from the scatterer 100. Furthermore, most of the transmission line stub 9 can be shared between the open stub 91 and the short stub 92. This allows for cost reduction compared to providing both the transmission line stub 9 as the open stub 91 and the transmission line stub 9 as the short stub 92, and also allows for a reduction in the mounting area on the circuit board CB, thereby enabling the antenna device 1 to be more compact.

[0149] 13, 19, etc., the impedance adjustment circuit in the antenna device 1 may be a circuit including any one of a capacitor element (capacitor 16), a coil element (coil 17), and a resistor element (resistor 18) having a resistance value other than 50 ohms. In this way, even when a capacitor element, a coil element, a resistor element, etc. are used, it is possible to re-radiate the radio wave 200C from the antenna on the non-excitation side, and to suitably cancel out the re-radiation of the radio wave 200B from the scatterer 100.

[0150] As described with reference to Figure 14 etc., the antenna device 1 includes a second selection unit 10 arranged between the non-excited antenna and the impedance adjustment circuit, and the impedance adjustment circuit includes a circuit using a transmission line stub 9, a circuit using a capacitor element (capacitor 16), a circuit using a coil element (coil 17), and a circuit using a resistor element (resistor 18) with a resistance value other than 50 ohms. The second selection unit 10 may select a circuit to be connected to the non-excited antenna from the circuit using the transmission line stub 9, the circuit using a capacitor element, the circuit using a coil element, and the circuit using a resistor. This makes it possible to adaptively change the re-radiation characteristics from the non-excited antenna. Therefore, it is possible to change the characteristics of the radio wave 200C re-radiated from the non-excited antenna to match the re-radiation characteristics from the scatterer 100, and it is possible to effectively cancel the re-radiation from the scatterer 100.

[0151] As described with reference to FIG. 19 and other figures, the antenna device 1 includes, as impedance adjustment circuits, a circuit using a transmission line stub 9, a circuit using a capacitor element (capacitor 16), a circuit using a coil element (coil 17), and a circuit using a resistor element (resistor 18) with a resistance value other than 50 ohms. The second selection unit 10 may select a circuit to be connected to the non-excited antenna from the circuit having a 50 ohm termination resistor (50 ohm termination circuit 19), the circuit using the transmission line stub 9, the circuit using a capacitor element, the circuit using a coil element, and the circuit using a resistor. This makes it possible to adaptively change the re-radiation characteristics from the non-excited antenna or to suppress re-radiation from the non-excited antenna in the first place. Therefore, it is possible to change the characteristics of the radio wave 200C re-radiated from the non-excited antenna to match the re-radiation characteristics from the scatterer 100, or to suppress re-radiation of the radio wave 200C from the non-excited antenna when the re-radiation of the radio wave 200B from the scatterer 100 is small.

[0152] As described with reference to Fig. 5 and other figures, the first antenna Ant1 and the second antenna Ant2 in the antenna device 1 may both be patch antennas. This allows the first antenna Ant1 and the second antenna Ant2 to have directivity in the forward direction (one direction) and reduce radio wave radiation in the backward direction (opposite direction). This reduces the influence of multipath (unwanted waves) from the rear, allowing efficient wireless communication with another device (portable terminal device 2) located in front, and improving the accuracy of distance measurement results.

[0153] 2 and the like, the first antenna Ant1 and the second antenna Ant2 in the antenna device 1 may perform wireless communication for direction detection between devices (between the antenna device 1 and the mobile terminal device 2). By intentionally re-radiating radio waves 200C from the non-excited antenna in order to cancel out re-radiation of radio waves 200B from the scatterer 100, wireless communication for calculating distance information Ddis and angle information Dang (angle of arrival Ang1) with respect to another device (mobile terminal device 2) can be preferably performed, and the accuracy of the calculation results can be improved.

[0154] As described with reference to each diagram such as Fig. 5 , the antenna device 1 may be provided with a first impedance adjustment circuit (such as a transmission line stub 9A) connectable to the first antenna Ant1 and a second impedance adjustment circuit (such as a transmission line stub 9B) connectable to the second antenna Ant2 as impedance adjustment circuits. That is, an impedance adjustment circuit is provided for each of the first antenna Ant1 and the second antenna Ant2. Even with this configuration, it is possible to re-radiate the radio wave 200C from the antenna on the non-excited side, and to cancel out the radio wave 200B re-radiated from the scatterer 100.

[0155] The positioning system S as a wireless communication direction detection system includes a first antenna Ant1 provided in a first device (antenna device 1), a second antenna Ant2 provided in the first device (antenna device 1) and different from the first antenna Ant1, a first selection unit 5 that selects either the first antenna Ant1 or the second antenna Ant2, an impedance adjustment circuit that has an impedance that re-radiates radio waves and is connectable to either the first antenna Ant1 or the second antenna Ant2, a third antenna (terminal antenna AntT) provided in a second device (portable terminal device 2) different from the first device (antenna device 1), and a direction detection unit (angle calculation unit F1) that detects the direction of the second device (portable terminal device 2) relative to the first device (antenna device 1) based on wireless communication between the first antenna Ant1 and the third antenna (terminal antenna AntT) and wireless communication between the second antenna Ant2 and the third antenna (terminal antenna AntT). That is, when the radio wave arrival angle is calculated by performing wireless communication using the antennas provided in the first device and the second device, it is possible to re-radiate the radio wave 200C from the antenna on the non-excitation side in order to reduce the influence of re-radiation of the radio wave 200B by the scatterer 100 on the first device side. Therefore, it is possible to improve the calculation accuracy of the radio wave arrival angle, and it is possible to obtain angle information Dang (direction) and distance information Ddis of the second device relative to the first device with higher accuracy.

[0156] 8 and the like, the positioning system S as a wireless communication direction detection system may be provided with a plurality of types of impedance adjustment circuits, and may include a second selection unit 10 that is arranged between the non-excitation-side antenna and the impedance adjustment circuit and that sequentially selects from the plurality of types of impedance adjustment circuits as a circuit to be connected to the non-excitation-side antenna, and a selection instruction unit F3 that issues a selection instruction to the second selection unit 10 based on the detection result of the direction detection unit (angle calculation unit F1) for each selection of the impedance adjustment circuit by the second selection unit 10. In this way, when a plurality of types of circuits are provided as the impedance adjustment circuits, it is possible to select an impedance adjustment circuit that can obtain the arrival angle Ang1 of the radio wave 200A and the distance information Ddis with higher accuracy.

[0157] 14, 19, etc., the multiple types of impedance adjustment circuits in the positioning system S as a wireless communication direction detection system may be configured with any of a circuit using a transmission line stub 9, a circuit using a capacitor element (capacitor 16), a circuit using a coil element (coil 17), and a circuit using a resistor element (resistor 18) with a resistance value other than 50 ohms. This allows simple circuits to be used as impedance adjustment circuits.

[0158] 14, 19, etc., the second selection unit 10 in the positioning system S as a wireless communication direction detection system may select a circuit connected to the non-excited antenna from among a circuit configured with a 50 ohm termination resistor (50 ohm termination circuit 19) and multiple types of impedance adjustment circuits. This makes it possible to select the 50 ohm termination circuit 19 as a configuration that suppresses re-radiation of the radio wave 200C from the non-excited antenna when the re-radiation of the radio wave 200B from the scatterer 100 is small.

[0159] The direction detection method in wireless communication of the present technology detects the direction of a second device relative to the first device by wireless communication between a first device (antenna device 1) having a first antenna Ant1, a second antenna Ant2 different from the first antenna Ant1, a first selection unit 5 that selects either the first antenna Ant1 or the second antenna Ant2, and an impedance adjustment circuit that has an impedance that re-radiates radio waves and can be connected to either the first antenna Ant1 or the second antenna Ant2, and a second device (portable terminal device 2) having a third antenna (terminal antenna AntT).

[0160] Such a direction detection method can also provide the various functions and effects described above.

[0161] The effects described in this specification are merely examples and are not limiting, and other effects may also be obtained. Furthermore, the examples described above can be combined in any way as long as the combination is not impossible.

[0162] <8. The Present Technology> The present technology can also adopt the following configurations. (1) An antenna device comprising: a first antenna; a second antenna different from the first antenna; a first selection unit that selects either the first antenna or the second antenna; and an impedance adjustment circuit that has an impedance that re-radiates radio waves and is connectable to either the first antenna or the second antenna. (2) The antenna device described in (1) above, in which the impedance of the impedance adjustment circuit is less than 50 ohms or greater than 50 ohms. (3) The antenna device described in any of (1) to (2) above, in which the first selection unit selects one of the first antenna and the second antenna that is an excitation side in wireless communication, and the impedance adjustment circuit is connectable to one of the first antenna and the second antenna that is not selected by the first selection unit. (4) The antenna device according to (3) above, comprising: a second selection unit arranged between the non-excited antenna and the impedance adjustment circuit; and a circuit having a 50 ohm termination resistor and connectable to the non-excited antenna, wherein the second selection unit selects the circuit having the 50 ohm termination resistor and the circuit connected from the impedance adjustment circuit to the non-excited antenna. (5) The antenna device according to any of (3) to (4), wherein the impedance adjustment circuit is a transmission line stub. (6) The antenna device according to (5), wherein the transmission line stub is formed as an RF cable. (7) The antenna device according to any of (5) to (6), wherein the transmission line stub is switchable in length. (8) The antenna device according to any of (5) to (7), wherein an open stub and a short stub are provided as the transmission line stub, and comprising: a second selection unit that selects the circuit connected to the non-excited antenna from the open stub and the short stub. (9) The antenna device according to any one of (5) to (7), further comprising a third selection unit that selects whether or not the transmission line stub is grounded.(10) The antenna device according to any one of (1) to (9), wherein the impedance adjustment circuit is a circuit including any one of a capacitor element, a coil element, and a resistor element having a resistance value other than 50 ohms. (11) The antenna device according to any one of (3) to (10), further comprising a second selection unit arranged between the non-excited antenna and the impedance adjustment circuit, wherein the impedance adjustment circuit includes a circuit using a transmission line stub, a circuit using a capacitor element, a circuit using a coil element, and a circuit using a resistor element having a resistance value other than 50 ohms, and the second selection unit selects a circuit to be connected to the non-excited antenna from the circuit using the transmission line stub, the circuit using the capacitor element, the circuit using the coil element, and the circuit using the resistor element. (12) The antenna device according to (4) above, wherein the impedance adjustment circuits include a circuit using a transmission line stub, a circuit using a capacitor element, a circuit using a coil element, and a circuit using a resistor element with a resistance value other than 50 ohms, and the second selection unit selects a circuit to be connected to the antenna on the non-excited side from the circuit having the 50 ohm termination resistor, the circuit using the transmission line stub, the circuit using the capacitor element, the circuit using the coil element, and the circuit using the resistor element. (13) The antenna device according to any of (1) to (12) above, wherein the first antenna and the second antenna are both patch antennas. (14) The antenna device according to any of (1) to (13) above, wherein the first antenna and the second antenna perform wireless communication for direction detection between the devices. (15) The antenna device according to any of (1) to (14) above, wherein the impedance adjustment circuits include a first impedance adjustment circuit connectable to the first antenna and a second impedance adjustment circuit connectable to the second antenna.(16) A wireless communication direction detecting system comprising: a first antenna provided in a first device, a second antenna provided in the first device and different from the first antenna, a first selection unit that selects either the first antenna or the second antenna, an impedance adjustment circuit having an impedance that re-radiates radio waves and connectable to either the first antenna or the second antenna, a third antenna provided in a second device different from the first device, and a direction detection unit that detects the direction of the second device relative to the first device based on wireless communication between the first antenna and the third antenna and wireless communication between the second antenna and the third antenna. (17) The wireless communication direction detecting system according to (15), comprising: a second selection unit that is disposed between an antenna on a non-excitation side and the impedance adjustment circuit and that sequentially selects one of the plurality of types of impedance adjustment circuit as a circuit to be connected to the antenna on the non-excitation side, and a selection instruction unit that issues a selection instruction to the second selection unit based on a detection result of the direction detection unit for each selection of the impedance adjustment circuit by the second selection unit. (18) The wireless communication direction detecting system according to (16), wherein the plurality of types of impedance adjustment circuits are configured with any of a circuit using a transmission line stub, a circuit using a capacitor element, a circuit using a coil element, and a circuit using a resistor element having a resistance value other than 50 ohms. (19) The wireless communication direction detecting system according to any of (16) to (17), wherein the second selection unit selects a circuit connected to the antenna on the non-excited side from a circuit configured with a 50 ohm termination resistor and the plurality of types of impedance adjustment circuits. (20) A direction detecting method comprising: a first device having a first antenna, a second antenna different from the first antenna, a first selection unit that selects either the first antenna or the second antenna, and an impedance adjustment circuit that has an impedance that re-radiates radio waves and is connectable to either the first antenna or the second antenna; and a second device having a third antenna, wherein the direction of the second device relative to the first device is detected by wireless communication between the first device and the second device.

[0163] REFERENCE SIGNS LIST 1 Antenna device 5 First selection unit 9 Transmission line stub 9A Transmission line stub 9B Transmission line stub 10 Second selection unit 10A Second selection unit 10B Second selection unit 11 Third selection unit 15 RF cable 16 Capacitor (capacitor element) 17 Coil (coil element) 19 50 ohm termination circuit (circuit configured with a 50 ohm termination resistor) 18 Resistor (resistance element) 91 Open stub 91A Open stub 91B Open stub 92 Short stub 92A Short stub 92B Short stub Ant1 First antenna Ant2 Second antenna F1 Angle calculation unit (direction detection unit) F3 Selection instruction unit S Positioning system (wireless communication direction detection system)

Claims

1. An antenna device comprising: a first antenna; a second antenna different from the first antenna; a first selection unit that selects either the first antenna or the second antenna; and an impedance adjustment circuit that has an impedance that re-radiates radio waves and can be connected to either the first antenna or the second antenna.

2. The antenna device according to claim 1, wherein the impedance of the impedance adjustment circuit is less than 50 ohms or greater than 50 ohms.

3. The antenna device according to claim 1, wherein the first selection unit selects one of the first antenna and the second antenna which is an excited antenna in wireless communication, and the impedance adjustment circuit is connectable to one of the first antenna and the second antenna which is a non-excited antenna not selected by the first selection unit.

4. The antenna device according to claim 3, further comprising: a second selection unit arranged between the non-excited antenna and the impedance adjustment circuit; and a circuit having a 50 ohm termination resistor and connectable to the non-excited antenna, wherein the second selection unit selects between the circuit having the 50 ohm termination resistor and a circuit connected from the impedance adjustment circuit to the non-excited antenna.

5. The antenna device according to claim 3, wherein the impedance adjustment circuit is a transmission line stub.

6. The antenna device according to claim 5, wherein the transmission line stub is formed as an RF cable.

7. The antenna device according to claim 5, wherein the transmission line stub is capable of changing its length.

8. The antenna device according to claim 5, further comprising an open stub and a short stub as the transmission line stub, and a second selection section which selects the circuit to be connected to the non-excited antenna from the open stub and the short stub.

9. The antenna device according to claim 5, further comprising a third selection section which selects whether or not the transmission line stub is grounded.

10. The antenna device according to claim 1, wherein the impedance adjustment circuit is a circuit comprising any one of a capacitor element, a coil element, and a resistor element having a resistance value other than 50 ohms.

11. An antenna device as described in claim 3, further comprising a second selection unit arranged between the non-excited antenna and the impedance adjustment circuit, the impedance adjustment circuit including a circuit using a transmission line stub, a circuit using a capacitor element, a circuit using a coil element, and a circuit using a resistive element with a resistance value other than 50 ohms, and the second selection unit selects a circuit to be connected to the non-excited antenna from the circuit using the transmission line stub, the circuit using the capacitor element, the circuit using the coil element, and the circuit using the resistive element.

12. The antenna device according to claim 4, wherein the impedance adjustment circuits include a circuit using a transmission line stub, a circuit using a capacitor element, a circuit using a coil element, and a circuit using a resistive element with a resistance value other than 50 ohms, and the second selection unit selects a circuit to be connected to the non-excited antenna from the circuit having the 50 ohm termination resistor, the circuit using the transmission line stub, the circuit using the capacitor element, the circuit using the coil element, and the circuit using the resistive element.

13. The antenna device according to claim 1, wherein the first antenna and the second antenna are both patch antennas.

14. The antenna device according to claim 1, wherein the first antenna and the second antenna perform wireless communication for direction detection between the devices.

15. The antenna device according to claim 1, wherein the impedance adjustment circuits include a first impedance adjustment circuit connectable to the first antenna and a second impedance adjustment circuit connectable to the second antenna.

16. A wireless communication direction detection system comprising: a first antenna provided in a first device; a second antenna provided in the first device and different from the first antenna; a first selection unit that selects either the first antenna or the second antenna; an impedance adjustment circuit having an impedance that re-radiates radio waves and connectable to either the first antenna or the second antenna; a third antenna provided in a second device different from the first device; and a direction detection unit that detects the direction of the second device relative to the first device based on wireless communication between the first antenna and the third antenna and wireless communication between the second antenna and the third antenna.

17. The wireless communication direction detection system according to claim 16, further comprising: a second selection unit that is disposed between a non-excited antenna and the impedance adjustment circuit and that sequentially selects one of the plurality of types of impedance adjustment circuit as a circuit to be connected to the non-excited antenna; and a selection instruction unit that issues a selection instruction to the second selection unit based on a detection result of the direction detection unit each time the second selection unit selects one of the impedance adjustment circuits.

18. The wireless communication direction detection system according to claim 17, wherein the plurality of types of impedance adjustment circuits are configured with any of a circuit using a transmission line stub, a circuit using a capacitor element, a circuit using a coil element, and a circuit using a resistor element having a resistance value other than 50 ohms.

19. The wireless communication direction detection system according to claim 17, wherein the second selection unit selects a circuit to be connected to the non-excited antenna from among a circuit configured with a 50 ohm termination resistor and the plurality of types of impedance adjustment circuits.

20. A direction detection method for detecting a direction of a second device relative to a first device by wireless communication between the first device and a second device having a third antenna, the first device having a first antenna, a second antenna different from the first antenna, a first selection unit that selects either the first antenna or the second antenna, and an impedance adjustment circuit that has an impedance that re-radiates radio waves and can be connected to either the first antenna or the second antenna, and the second device having a third antenna.

Images