Radio wave measurement device, radio wave measurement system, and radio wave measurement method

Abstract

To provide a radio wave measurement device, radio wave measurement system, and radio wave measurement method capable of measuring the arrival direction and the received power of radio waves (incoming waves).SOLUTION: A radio wave measurement device comprises: a directional antenna 11 that receives radio waves arriving from an oriented direction; and a control device 13 that controls the orientation direction of the directional antenna 11 and outputs the frequency spectrum of the radio wave received by the directional antenna 11. The control device 13 performs: a first scan that receives the radio waves while changing the orientation direction of the directional antenna 11 according to a first predetermined setting; and a second scan that receives the radio waves while changing the orientation direction of the directional antenna 11 according to a second setting in which higher measurement accuracy than the first setting can be obtained for a measurement range specified on the basis of the reception result of the first scan.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a radio wave measuring device, a radio wave measuring system, and a radio wave measuring method. [Background technology]

[0002] In a wireless communication environment in which wireless communication is performed, it is necessary to reduce interference between radio waves and the occurrence of dead zones where radio waves cannot reach. Patent Document 1 describes a radio wave probe that receives radio waves and transmits information representing a wireless environment, the radio wave probe including a radio wave sensor that detects radio waves, a state sensor that detects a stationary state and a moving state of the radio wave probe, a communication means, and a control means that generates primary information including the received signal strength of the radio waves detected by the radio wave sensor and transmits the primary information via the communication means, and the control means transmits sensor data including identification information of the radio wave probe and the moving state and stationary state detected by the state sensor via the communication means when the state detected by the state sensor changes.

[0003] Patent document 2 describes a position estimation device that estimates the position of a radio station transmitting radio waves based on reception information of radio waves measured by multiple radio wave sensors, and the position estimation device includes a radio wave sensor placement information memory unit that stores radio wave sensor placement information indicating the placement of each of the radio wave sensors that are candidates for selection, and a radio wave sensor data acquisition unit that selects a radio wave sensor to acquire data from among the candidate radio wave sensors based on a predicted position of the predicted position of the destination to which the radio station will move, and acquires reception information of radio waves measured by the radio wave sensor that is the selected target for data acquisition. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-191593 A [Patent Document 2] JP 2022-143019 A Summary of the Invention [Problem to be solved by the invention]

[0005] In radio wave propagation path control, the location of a radio wave source that transmits radio waves used for communication (hereinafter referred to as "desired waves") and the location of a radio wave source that transmits radio waves not used for communication and that may cause interference (hereinafter referred to as "unwanted waves") are identified. This requires measuring the direction of arrival of radio waves arriving at a specific location (hereinafter referred to as "arriving waves") and the received power of the arriving waves.

[0006] An object of the present invention is to provide a radio wave measuring device, a radio wave measuring system, and a radio wave measuring method for measuring the direction of arrival and received power of radio waves. [Means for solving the problem]

[0007] To achieve the above-mentioned object, the present invention provides a radio wave measuring device comprising a directional antenna that receives radio waves arriving from a direction in which the directional antenna is pointed, and a control device that controls the direction in which the directional antenna is pointed and outputs the frequency spectrum of the radio waves received by the directional antenna, wherein the control device performs a first scan in which the direction in which the directional antenna is pointed is changed according to a predetermined first setting to receive radio waves, and a second scan in which the direction in which the directional antenna is pointed is changed according to a second setting that provides higher measurement accuracy than the first setting for a measurement range identified based on the reception results from the first scan. More specifically, the control device may be configured to control the directional antenna to change its direction at a predetermined first speed in the first scan, and when a radio wave whose reception power is greater than a predetermined threshold is received in the first scan, to limit the measurement range in the second scan to a certain range that includes the direction from which the radio wave comes, and to control the directional antenna to change its direction at a second speed slower than the first speed. In addition, the radio waves to be measured may be radio waves used for transmitting a burst signal output at regular time intervals, and the control device may be configured to perform a first scan at a first speed that does not miss the radio waves used for transmitting the burst signal, based on the beam width of the directional antenna and the time interval of the burst signal. The control device may also be configured to perform a first scan by setting the beam width of the directional antenna to a predetermined first beam width, and to perform a second scan by setting the beam width of the directional antenna to a second beam width narrower than the first beam width. The directional antenna may also be configured as a phased array antenna, which is configured by arranging a plurality of antenna elements and is capable of changing the beam width depending on the number of antenna elements used. Also, a configuration may be adopted in which a stand to which a directional antenna can be detachably attached is provided, and a directional antenna having a different beam width for the first scan and the second scan can be attached. From another perspective, a radio wave measurement system to which the present invention can be applied comprises the above-mentioned radio wave measuring device, a spectrum analyzer that analyzes the frequency spectrum of the radio waves received by the directional antenna of the radio wave measuring device to generate spectral data, and a data processing device that identifies the direction of arrival of the radio waves at the measurement point where the radio wave measuring device is installed from the spectral data obtained from the spectrum analyzer. Furthermore, from another perspective, a radio wave measurement method to which the present invention is applied is a radio wave measurement method that measures a first frequency spectrum based on radio waves received at a measurement point while changing the direction of the directional antenna at a predetermined first speed, and when radio waves having a received power greater than a predetermined threshold are detected in spectral data obtained by analyzing the first frequency spectrum, limits a range for changing the direction of the directional antenna to a certain range that includes the arrival direction of the radio waves, measures a second frequency spectrum based on the received radio waves while changing the direction of the directional antenna at a second speed slower than the first speed, and identifies the arrival direction of the radio waves at the measurement point from the spectral data obtained by analyzing the second frequency spectrum. Furthermore, from another perspective, the radio wave measurement method to which the present invention is applied is a radio wave measurement method which measures a first frequency spectrum based on radio waves received at a measurement point while changing the pointing direction of the directional antenna, with the beam width of the directional antenna set to a predetermined first beam width, measures a second frequency spectrum based on the radio waves received while changing the pointing direction of the directional antenna, with the beam width of the directional antenna set to a second beam width narrower than the first beam width, and identifies the arrival direction of the radio waves at the measurement point from spectral data obtained by analyzing the second frequency spectrum. Effect of the Invention

[0008] According to the present invention, it is possible to provide a radio wave measuring device, a radio wave measuring system, and a radio wave measuring method for measuring the direction of arrival and the received power of a radio wave (arrival wave). [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an example of the configuration of a radio wave measurement system to which the present embodiment is applied. [Diagram 2] FIG. 2 is a diagram illustrating an example of a hardware configuration of a computer that realizes a control device and a data processing device. [Diagram 3] FIG. 1 is a diagram illustrating an example of the appearance of a radio wave measurement system. [Figure 4] 4A and 4B are diagrams showing examples of the measurement ranges of the first scan and the second scan when the scanning speeds are set to different values, where FIG. 4A shows the measurement range of the first scan, and FIG. 4B shows the measurement range of the second scan. [Diagram 5] FIG. 2 is a diagram illustrating an example of a beacon signal transmitted from an access point. [Figure 6] 6A and 6B are diagrams showing examples of the measurement ranges of the first scan and the second scan with different beam width settings, where FIG. 6(A) is a diagram showing the measurement range of the first scan, and FIG. 6(B) is a diagram showing the measurement range of the second scan. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Consider the case where the direction from which radio waves arrive (arrival direction) is measured in a local network (wireless LAN) constructed using wireless communication. An environment in which a wireless LAN is constructed is called a wireless LAN environment. In a wireless LAN environment, there are access points (hereinafter referred to as "APs") that serve as radio wave sources, and devices (hereinafter referred to as "terminal devices") that receive radio waves from the APs and transmit radio waves to the APs. Note that the technology described in this embodiment can also be applied to environments other than a wireless LAN environment where a network is constructed using wireless communication.

[0011] Radio waves transmitted and received between the AP and the terminal device are desired waves in this wireless LAN environment. Some desired waves do not arrive directly from the AP, but arrive at the terminal device after being reflected by walls, ceilings, floors, windows, etc. Furthermore, even in a wireless LAN environment where transmission and reception of desired waves between the AP and the terminal is desired, there are areas where the radio waves are blocked by obstacles such as walls that prevent the passage of radio waves (hereinafter referred to as "dead zones"). Furthermore, in the wireless LAN environment, there are other APs that serve as radio wave sources, and there are radio waves that arrive at the wireless LAN environment from radio wave sources other than the wireless LAN environment. Radio waves from other APs and radio waves from radio wave sources other than the wireless LAN environment are unwanted waves rather than desired waves in this wireless LAN environment. If unwanted waves exist, it may be difficult for the terminal device to receive the desired waves, or the desired waves and unwanted waves may interfere with each other, hindering the reception quality of the desired waves.

[0012] In such a wireless LAN environment, in order to simultaneously address dead zones where radio waves do not reach and suppress interference, it is necessary to control the radio wave propagation path. More specifically, in a wireless LAN environment, it is essential to identify the location of the radio wave source of the desired wave and the location of the radio wave source of the unwanted wave, make it easier for the terminal device to receive the desired wave, or transmit the desired wave to the terminal device while avoiding the unwanted wave. This requires measuring the direction of arrival and the received power of the radio wave and estimating the location of the radio wave source.

[0013] <Configuration of radio wave measuring device> 1 is a diagram showing an example of the configuration of a radio wave measurement system 1 to which this embodiment is applied. The radio wave measurement system 1 includes a radio wave measurement device 10, a spectrum analyzer 20, and a data processing device 30. The radio wave measurement device 10 is installed at a point where an incoming wave is measured (a measurement point). The spectrum analyzer 20 and the data processing device 30 may be installed at the measurement point, or may be installed at a location other than the measurement point.

[0014] The radio wave measuring device 10 includes a directional antenna 11, a base 12, and a control device 13. The directional antenna 11 is an antenna having directionality capable of receiving radio waves in a specific frequency band. The direction in which the directional antenna 11 points is called the direction of direction. For example, an array antenna in which a plurality of antenna elements are arranged on a plane may be used as the directional antenna 11. For example, a patch antenna may be used as the antenna element. Note that the directional antenna 11 is not limited to an array antenna as long as it has directionality. The base 12 supports the directional antenna 11 so that the direction in which the directional antenna points (direction of direction of direction) can be changed. The control device 13 controls the base 12 to control the direction of direction of the directional antenna 11 supported by the base 12.

[0015] The spectrum analyzer 20 is connected to the directional antenna 11 and acquires the frequency spectrum of the radio waves received by the directional antenna 11. There are two types of spectrum analyzers: a sweep type that observes the signal magnitude while sweeping the frequency, and a real-time type that obtains the frequency spectrum directly from a time series signal by performing FFT (Fast Fourier Transform) on a time series signal cut out in a short time window. The spectrum analyzer 20 used in this embodiment is assumed to be a real-time type spectrum analyzer (real-time spectrum analyzer). Therefore, the spectrum analyzer 20 continuously analyzes the relationship between the frequency of the radio waves and the received power. Hereinafter, this relationship between the frequency of the radio waves and the received power will be referred to as the spectrum data of the received power.

[0016] The data processing device 30 acquires information about the direction of direction of the directional antenna 11 and the spectrum data obtained by the spectrum analyzer 20. Then, the data processing device 30 identifies the direction of arrival of the radio wave at the measurement point where the radio wave measuring device 10 is installed based on the direction of direction of the directional antenna 11 and the spectrum data. Here, the direction of arrival may be expressed as an azimuth angle (hereinafter referred to as "arrival angle"). A spectrogram is a graph in which the measurement time of the spectrum data is converted into the arrival angle indicating the direction of arrival of the arriving wave, that is, a graph in which the received power intensity is displayed on two axes of frequency and arrival angle. A spectrum analyzer is also called a spectrum analyzer.

[0017] <Hardware configuration of the control device 13 and the data processing device 30> FIG. 2 is a diagram showing an example of a hardware configuration of a computer that realizes the control device 13 and the data processing device 30. The control device 13 and the data processing device 30 are realized by, for example, a computer 100 as shown in FIG. 2. The computer 100 shown in FIG. 2 includes one or more processors 101, which are calculation means, and a storage device 102. The processor 101 realizes each function of the control device 13 or the data processing device 30 by reading and executing a program stored in the storage device 102. For example, a central processing unit (CPU), a micro processing unit (MPU), a graphics processing unit (GPU), a digital signal processor (DSP), or the like is used as the processor 101. For example, a random access memory (RAM) or a read only memory (ROM) as a main storage device, as well as a magnetic disk device, a solid state drive (SSD), a flash memory, or the like as an auxiliary storage device is used as the storage device 102.

[0018] The computer shown in FIG. 2 also includes an input device 103, an output device 104, and an interface 105. For example, a keyboard or a mouse is used as the input device 103. A user can operate the input device 103 to input various instructions such as setting the directional direction of the directional antenna 11. For the output device 104, a display device such as a display or a printer is used. The output of the output device 104 presents various information such as control information for the directional antenna 11 and results of data processing to the user. The interface 105 is used to connect to an external device and exchange data. The stand 12 of the radio wave measuring device 10 is connected to the interface 105. The directional antenna 11 is connected to the interface 105 via the stand 12. The spectrum analyzer 20 is also connected to the interface 105.

[0019] 2, the computer 100 as the control device 13 accepts instructions and control information such as setting the direction of the directional antenna 11 input by a user's operation on the input device 103. The computer 100 as the control device 13 then outputs a signal to control the stand 12 via the interface 105, and performs operations such as controlling the direction of the directional antenna 11 according to the settings. The computer 100 as the control device 13 also receives the frequency spectrum of the radio waves received by the directional antenna 11 via the interface 105, and transmits it to the spectrum analyzer 20.

[0020] 2, the computer 100 as the data processing device 30 accepts instructions and parameters related to data processing input by a user's operation on the input device 103. The computer 100 as the data processing device 30 also receives spectrum data from the spectrum analyzer 20 via the interface 105. The computer 100 as the data processing device 30 processes the spectrum data received from the spectrum analyzer 20 and identifies the direction of arrival of the radio wave at the measurement point where the radio wave measuring device 10 is installed. More specifically, when the received power at the frequency of the desired wave is greater than a predetermined threshold based on the spectrum data, the data processing device 30 determines the direction of arrival of the radio wave (desired wave) as the direction of arrival.

[0021] 2 is merely an example of a hardware configuration of a computer that realizes the control device 13 and the data processing device 30, and may have other configurations. Also, one computer 100 may be configured to function as both the control device 13 and the data processing device 30.

[0022] Fig. 3 is a diagram showing an example of the appearance of the radio wave measurement system 1. The radio wave measurement system 1 shown in Fig. 3 includes a dolly 40 in addition to the radio wave measurement device 10, spectrum analyzer 20, and data processing device 30 shown in Fig. 1. The control device 13 and the data processing device 30 are configured by a single computer.

[0023] The dolly 40 includes two-stage mounting plates 41 and 42 each having a rectangular planar shape, four support columns 43, and four wheels 44. Here, the dolly 40 is assumed to be placed on a horizontal floor surface. Note that the wheels 44 located on the back side of the paper surface are omitted. Each of the four support columns 43 is provided at the four corners of the mounting plates 41 and 42 to support the mounting plates 41 and 42. Each of the four wheels 44 is provided at the four corners of the lower mounting plate 42. This allows the dolly 40 to move on the floor surface, making it easy to change the measurement point. Note that the dolly 40 may be configured so that its movement is controlled by the control device 13, the data processing device 30, etc., or may be configured so that it is moved by human power. The radio wave measuring device 10 is mounted on the upper mounting plate 41 of the dolly 40. The spectrum analyzer 20 and the power supply device 50 are mounted on the lower mounting plate 42.

[0024] The radio wave measuring device 10 includes a directional antenna 11, a stand 12, and a control device 13. The directional antenna 11 is, for example, a planar microstrip antenna that receives right-handed circularly polarized waves in the sub-6 GHz band of 2.4 GHz and 5 GHz.

[0025] The stand 12 includes a support unit 121 and a drive unit 122. The directional antenna 11 is fixed to the support unit 121 and supports the directional antenna 11. Since it is unknown from which direction the radio waves will arrive at the measurement point, it is required to measure the arriving waves by directing the directional direction of the directional antenna 11 around the measurement point. Therefore, the support unit 121 is configured to change the directional direction of the directional antenna 11. For example, the support unit 121 has an axis 121A, and the direction of the directional antenna 11 can be changed by rotating the support unit 121 around the axis 121A. Here, the direction of the directional antenna 11 is the directional direction projected onto a plane perpendicular to the axis 121A. Therefore, if the directional direction is within a plane perpendicular to the axis 121A, the directional direction of the directional antenna 11 and the direction of the directional antenna 11 match.

[0026] Here, axis 121A is provided vertically, and the direction of directional antenna 11 can be changed in a horizontal plane by rotating support 121. Support 121 is configured to rotate in a horizontal plane around axis 121A (illustrated as rotation in a horizontal plane in FIG. 3). In this way, the direction of direction of directional antenna 11 can be easily changed. When it is unknown from which direction radio waves arrive, the direction of arrival can be easily and accurately identified by measuring the arriving waves at multiple stages with different measurement accuracy. Details of the operation when measuring the arriving waves will be described later.

[0027] Furthermore, the support part 121 is configured to be able to move the directional antenna 11 in a direction along the axis 121A. For example, if the axis is vertical, the height of the directional antenna 11 from the floor surface or the like can be changed (illustrated as up and down in FIG. 3). For example, by installing the directional antenna 11 in accordance with the height at which a terminal device that receives radio waves from a radio wave source is used, it is possible to measure the incoming waves in an environment similar to that at which the terminal device is used.

[0028] Furthermore, the support 121 is configured so that the angle between the axis 121A and the directional direction of the directional antenna 11 can be changed. For example, if the axis 121A is vertical, the directional direction of the directional antenna 11 can be set to the horizontal direction, a direction below the horizontal direction (a direction to be tilted down), and a direction above the horizontal direction (a direction to be looked up). As an example, if the directional direction relative to the axis 121A is horizontal, which is set to 0°, the directional direction can be set in the range of -30° (depression angle) to 90° (elevation angle). In this case, the directional direction of the directional antenna 11 can be set to a diagonally downward direction, a diagonally upward direction, or even a direction directly upward by swinging the directional direction in a direction perpendicular to the horizontal direction. In this way, when the wireless LAN environment is provided in a room of a building, it is possible to measure the incoming waves from the upper floors in addition to the incoming waves from the diagonally downward direction and the diagonally upward direction of the room.

[0029] The driving unit 122 is connected to the control device 13 and drives the support unit 121 according to an instruction from the control device 13. For example, the driving unit 122 rotates the support unit 121 around the axis 121A. The rotation speed is, for example, 3 rpm (20 seconds / revolution) to 10 rpm (6 seconds / revolution). The driving unit 122 may be configured to move the directional antenna 11 in a direction along the axis 121A of the support unit 121 according to an instruction from the control device 13. The driving unit 122 may also be configured to set an angle between the axis 121A and the directional direction of the directional antenna 11 according to an instruction from the control device 13. Note that the directional antenna 11 may be moved in a direction along the axis 121A of the support unit 121, or the angle between the axis 121A and the directional direction of the directional antenna 11 may be set manually. The driving unit 122 is configured to include a motor or the like as a driving source, and the operation such as rotation is controlled by a control signal from the control device 13. The power supply unit 50 is a power source for the drive unit 122 .

[0030] As described above, in the radio wave measurement system 1, the direction of arrival of the radio waves is measured while continuously changing the direction of the directional antenna 11 in the radio wave measurement device 10, and the direction of arrival of the radio waves is identified. Here, the spectrum analyzer 20 is a real-time spectrum analyzer that has a wide frequency band (broadband) and can continuously acquire signals. The radio wave measurement system 1 measures the arriving waves by measuring the frequency spectrum of the radio waves with the spectrum analyzer 20 while continuously changing the direction of the directional antenna 11. The spectrum analyzer 20 has an output unit 21 which is a display that displays the frequency spectrum and the like.

[0031] When the spectrum analyzer 20 is a real-time spectrum analyzer, a signal is acquired for each time window. Therefore, the interval between the directional directions from which the frequency spectrum is obtained changes depending on the rotation speed of the shaft 121A of the support unit 121 in the pedestal 12. The interval between the directional directions is the interval between the directional angles when the directional direction of the directional antenna 11 is displayed as an angle. Therefore, when the time window is a constant time, the interval between the directional angles between the obtained frequency spectra changes depending on the rotation speed of the support unit 121. Specifically, when the rotation speed is increased, the time required for measurement is shortened, but the interval between the directional angles is widened, and the measurement accuracy of the specified arrival angle is reduced. On the other hand, when the rotation speed is decreased, the time required for measurement is lengthened, but the interval between the directional angles is narrowed, and the measurement accuracy of the specified arrival angle is increased. Here, a large interval between the directional angles is called low resolution, and a small interval between the directional angles is called high resolution.

[0032] 3, the radio wave measurement system 1 is configured such that the radio wave measurement device 10, the spectrum analyzer 20, and the data processing device 30 are mounted on a dolly 40 and integrated together. In contrast, the spectrum analyzer 20 and the data processing device 30 may be installed in a location separate from the radio wave measurement device 10 and connected by cable or wirelessly.

[0033] <Method of measuring arriving waves> The radio wave measurement system 1 measures the incoming wave by multi-stage measurement with different measurement accuracy. As described above, the radio wave measurement device 10 receives radio waves while continuously changing the direction of the directional antenna 11 by operating the support part 121 of the stand 12 under the control of the control device 13. Then, the frequency spectrum of the radio wave received by the directional antenna 11 is sent from the control device 13 to the spectrum analyzer 20, where it is analyzed. The analysis result by the spectrum analyzer 20 is sent to the data processing device 30 as spectrum data. The data processing device 30 specifies the direction of arrival of the incoming wave based on the acquired spectrum data and the information on the direction of the directional antenna 11. Here, the control device 13 of the radio wave measurement device 10 performs an operation of changing the direction of the directional antenna 11 multiple times with settings that change the measurement accuracy of the incoming wave. This realizes multi-stage measurement with different measurement accuracy. Hereinafter, the operation of changing the direction of the directional antenna 11 under the control of the control device 13 is called "scanning".

[0034] As a specific example, a case where two stages of measurement with different measurement accuracy are performed will be described. The control device 13 performs a first scan with low measurement accuracy and a second scan with high measurement accuracy. The first scan is a scan to receive radio waves while changing the direction of the directional antenna 11 according to a first setting. The second scan is a scan to receive radio waves while changing the direction of the directional antenna 11 according to a second setting that provides higher measurement accuracy than the first setting.

[0035] <Example of settings based on scanning speed> As mentioned above, the spectrum analyzer 20, which is a real-time spectrum analyzer, acquires a signal for each time window, and therefore the distance between the directional angles of the obtained frequency spectra changes depending on the rotation speed of the support part 121 during scanning. Therefore, it is possible to make the rotation speed of the support part 121 during scanning different in the first and second settings used in the first and second scans. Specifically, in the first scan, the rotation speed of the support part 121 is set to a first speed as the first setting. In the second scan, a rotation speed slower than the first speed is set to a second speed as the second setting. This makes it possible to achieve higher measurement accuracy in the second scan than in the first scan.

[0036] In the above example, since the second speed in the second scan is slower than the first speed in the first scan, the second scan takes a longer time to rotate the support part 121 by the same angle. Therefore, it is conceivable that the first scan is performed on a wide measurement range in the first setting, and the second scan is performed on a narrow measurement range specified based on the radio wave reception result in the first scan in the second setting. Specifically, in the second scan, the measurement range is limited to a certain range including the arrival direction of the incoming wave specified in the first scan, for example.

[0037] The measurement range in the second scan may be specified, for example, based on the beam width of the directional antenna 11. The beam width is the angle between the direction in which the reception sensitivity of the directional antenna 11 to the incoming wave is maximum and the direction in which the sensitivity is 3 dB lower. The beam width is also called the 3 dB beam width, half-power beamwidth, half-value width, half-value angle, etc.

[0038] Specifically, for example, the measurement range in the second scan may be a range that is determined by an angle equivalent to twice the beam width of the directional antenna 11, centered on the direction of arrival determined in the first scan. When the direction of arrival is determined in the first scan, the radio wave source of the arriving wave as seen by the radio wave measuring device 10 is present within the range of the beam width that includes the determined direction of arrival. Therefore, by performing the second scan in the measurement range limited as described above, the direction of arrival can be determined with higher measurement accuracy.

[0039] FIG. 4 is a diagram showing an example of the measurement range of the first scan and the second scan with different scanning speed settings, FIG. 4(A) is a diagram showing the measurement range of the first scan, and FIG. 4(B) is a diagram showing the measurement range of the second scan. In FIG. 4(A) and (B), the circle S surrounding the radio wave measuring device 10 indicates the range in which the directional antenna 11 can be directed by the horizontal rotation of the support part 121 (see FIG. 3), and the measurement ranges in the first scan and the second scan are shown by solid lines. That is, in the first scan shown in FIG. 4(A), the measurement range is 360° around the radio wave measuring device 10, and in the second scan shown in FIG. 4(B), only the part shown by the solid line in the circle S is the measurement range. Here, as an example, the beam width of the directional antenna 11 is 15°. Therefore, the measurement range in the second scan is a range of 30° (=15°×2) centered on the arrival direction identified in the first scan. Therefore, in the first scan, beam B circles around the radio wave measuring device 10, and in the second scan, beam B moves within a range of 30° shown by the solid line in Figure 4(B) (see the arrows in Figures 4(A) and (B)).

[0040] Here, consider the case where the radio waves emitted from the radio wave source 60 are used to transmit a burst signal. A burst signal is a signal that is output at regular time intervals. In the IEEE802.11 frame used in wireless LANs, a beacon signal (burst signal) is transmitted every 100 msec (milliseconds) from an access point (AP), which is the radio wave source 60. The radio wave measurement system 1 detects the radio waves of this beacon signal as an arriving wave and identifies the direction of arrival.

[0041] FIG. 5 is a diagram showing an example of a beacon signal transmitted from an AP. In the example shown in FIG. 5, the AP (radio wave source 60) transmits a radio wave of 0.4 milliseconds as a beacon signal every 100 milliseconds. Therefore, in the first scan shown in FIG. 4(A), the rotation speed of the support part 121 needs to be set to a speed at which the beacon signal is not overlooked (lost). As an example, the rotation speed of the support part 121 in the first scan is 10 rpm. In this case, since it is 6 seconds / 360°, the rotation angle every 100 milliseconds is 6°. Therefore, when the beam width is 15°, the beacon signal is not overlooked. Note that the angle covered by the beam B of the directional antenna 11 due to the rotation of the support part 121 during 100 milliseconds is 21° (=6°+15°). That is, if an incoming wave of a beacon signal is detected in the first scan, the incoming direction is identified within a range of 21°.

[0042] On the other hand, in the second scan shown in FIG. 4(B), if the measurement range is a range of 30° centered on the arrival direction identified in the first scan, the range of 21° covered by the beam B of the directional antenna 11 during the above 100 milliseconds is included in the measurement range of the second scan. As an example, the rotation speed of the support part 121 in the second scan is 3 rpm. In this case, since it is 20 seconds / 360°, the rotation angle per 100 milliseconds is 1.8°. In this case, the angle covered by the beam B of the directional antenna 11 due to the rotation of the support part 121 during 100 milliseconds is 16.8° (=1.8°+15°). That is, if the arrival wave of the beacon signal is detected in the second scan, the arrival direction is identified in a range of 16.8°, which is more accurate than the first scan. It is noted that the time required to cover the measurement range of 30° in the second scan is about 180 milliseconds. Therefore, the time required to perform the first and second scans and identify the arrival direction is approximately 6.2 seconds.

[0043] Here, consider a case where the direction of arrival is measured with the same measurement accuracy in a single scan. In this case, the arrival wave is measured while rotating the support part 121 at the rotation speed (3 rpm) in the second scan described above. Then, it takes 20 seconds for the directional direction of the directional antenna 11 to complete one revolution, which is a long time compared to the measurement by the multi-stage scan described above. Furthermore, if the time required for scanning increases, the amount of measurement data obtained by the scan also increases. Therefore, by performing the multi-stage scan described above, it is possible to shorten the time required for measurement and reduce the amount of data compared to the case where measurement is performed in a single scan.

[0044] <Example of beam width settings> The beam width of the directional antenna 11 corresponds to the range (angle) covered by the beam. Therefore, when the rotation speed of the support part 121 is the same, the wider the beam width, the wider the range covered by the beam in a certain time. Therefore, for example, when the signal interval of a burst signal is long, the wider the beam width, the less likely the signal will be overlooked during scanning. Therefore, it is considered to make the beam width of the directional antenna 11 different in the first and second settings used in the first and second scans. Specifically, in the first scan, the beam width of the directional antenna 11 is set as the first beam width as the first setting. In the second scan, the beam width narrower than the first beam width is set as the second beam width as the second setting.

[0045] FIG. 6 shows an example of the measurement range of the first scan and the second scan with different beam width settings, where FIG. 6(A) shows the measurement range of the first scan, and FIG. 6(B) shows the measurement range of the second scan. As an example, consider a case where the first beam width is 30° and the second beam width is 15°. In the example shown in FIG. 6(A) and (B), the rotation speed of the support part 121 in the first scan and the second scan is the same, and in this example, it is 10 rpm. Also, the radio wave emitted from the radio wave source 60 is a burst signal transmitted every 300 milliseconds.

[0046] In addition, in the first scan shown in Fig. 6(A), the measurement range is 360° around the radio wave measuring device 10, and in the second scan shown in Fig. 6(B), the measurement range is only a part of the circle S indicated by a solid line. Specifically, the measurement range in the second scan is a 60° range centered on the arrival direction identified in the first scan. Therefore, in the first scan, beam B goes around the radio wave measuring device 10, and in the second scan, beam B moves in the 60° range indicated by the solid line in Fig. 6(B) (see the arrows in Figs. 6(A) and (B)).

[0047] In the first scan shown in FIG. 6(A), the rotation speed of the support part 121 is 10 rpm, which is 6 seconds / 360°, and the rotation angle for every 300 milliseconds, which is the signal interval of the burst signal, is 18°. Therefore, if the beam width is 30°, the beacon signal will not be overlooked. Note that the angle covered by the beam B of the directional antenna 11 due to the rotation of the support part 121 in 300 milliseconds is 48° (=18°+30°). In other words, if an incoming wave of a beacon signal is detected in the first scan, the direction of arrival is identified within a range of 48°.

[0048] On the other hand, in the second scan shown in FIG. 6(B), if the measurement range is a 60° range centered on the arrival direction identified in the first scan, the 48° range covered by the beam B of the directional antenna 11 during the above 300 milliseconds is included in the measurement range of the second scan. The rotation speed of the support part 121 in the second scan is 10 rpm, the same as in the first scan, and the rotation angle every 300 milliseconds is 18°. In this case, the angle covered by the beam B of the directional antenna 11 due to the rotation of the support part 121 during 300 milliseconds is 33° (=18°+15°). In other words, if the arrival wave of the beacon signal is detected in the second scan, the arrival direction is identified within a range of 33°, which is more accurate than the first scan.

[0049] Here, consider a case where the arrival direction is measured by one scan with the second beam width (15°). In this case, the rotation angle for every 300 milliseconds, which is the signal interval of the burst signal, is 18°, and the beam width is 15°, so the beam width is narrower. For this reason, there is a possibility that the arrival wave (burst signal) from the radio wave source 60 will be overlooked. In contrast, when performing multi-stage scanning as described with reference to Figs. 6(A) and (B), the second scan is performed on a limited range including the arrival direction identified in the first scan, so even if the arrival wave is overlooked in the second scan, it is only necessary to repeat the second scan only in the limited range. In the above description, the rotation speed of the support part 121 in the first scan and the second scan is the same (10 rpm), but in order to reliably detect the arrival wave without overlooking it in the second scan, the rotation speed of the support part 121 may be slower.

[0050] As described with reference to Figs. 6(A) and (B), when performing multi-stage scanning by changing the beam width of the directional antenna 11, for example, a directional antenna 11 capable of changing the beam width is used in the radio wave measuring device 10. A phased array antenna may be used as the directional antenna 11 capable of changing the beam width. The phased array antenna is configured by arranging a plurality of antenna elements. The phased array antenna can exhibit strong directivity by adjusting the phase of the current of each antenna element. The directivity of the phased array antenna also depends on the number of arranged antenna elements. Therefore, in the example described with reference to Figs. 6(A) and (B), it is possible to change the number of antenna elements used in the first scan and the second scan. That is, the directivity of the phased array antenna is weakened by using some antenna elements in the first scan, and the directivity of the phased array antenna is strengthened by using more antenna elements than in the first scan in the second scan. This makes it possible to widen the beam width in the first scan and narrow the beam width in the second scan.

[0051] Also, instead of using a directional antenna 11 with a changeable beam width, a configuration may be adopted in which directional antennas 11 with different beam widths are attached to the radio wave measuring device 10. In this case, for example, the stand 12 (see FIG. 3) and the directional antenna 11 are configured to be detachable, and the directional antenna 11 with a wide beam width is attached for scanning in the first scan, and the directional antenna 11 with a narrow beam width is attached for scanning in the second scan. This makes it possible to widen the beam width in the first scan and narrow the beam width in the second scan.

[0052] Although the embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the above-mentioned embodiments. For example, in the above-mentioned embodiments, the radio wave to be measured is a burst signal, but the present invention is not limited to this, and the radio wave measurement system 1 of the present embodiment may be used to measure radio waves that are constantly transmitted or radio waves that are irregularly transmitted. In the above-mentioned embodiments, a configuration in which two-stage scanning (first scanning and second scanning) is performed is described, but the present invention is not limited to this, and a configuration in which three or more stages of scanning are performed may be used. In the above-mentioned embodiments, examples of 30° and 60° are shown as the measurement range of the second scanning, but the measurement range of the second scanning may be set according to the beam width used in the first scanning and the form of the radio wave transmitted from the radio wave source, and is not limited to the examples shown in the above-mentioned embodiments. In addition, various modifications and alternative configurations that do not deviate from the scope of the technical idea of ​​the present invention are included in the present invention. [Explanation of symbols]

[0053] 1...radio wave measuring system, 10...radio wave measuring device, 11...directional antenna, 12...mount, 13...control device, 20...spectrum analyzer, 30...data processing device, 60...radio wave source, B...beam

Claims

1. a directional antenna for receiving radio waves coming from a direction in which the antenna is pointed; a control device that controls the direction of the directional antenna and outputs a frequency spectrum of the radio wave received by the directional antenna; The control device includes: a first scan for receiving radio waves while changing a direction of the directional antenna in accordance with a first setting determined in advance; a second scan for receiving radio waves while changing the direction of the directional antenna according to a second setting that provides a higher measurement accuracy than the first setting for a measurement range specified based on a reception result of the first scan; A radio wave measuring device comprising:

2. The control device includes: In the first scan, a control is performed so as to change a direction of the directional antenna at a predetermined first speed; 2. The radio wave measuring device according to claim 1, characterized in that, when a radio wave having a received power greater than a predetermined threshold is received in the first scan, the measurement range in the second scan is limited to a certain range that includes the direction of arrival of the radio wave, and the direction of the directional antenna is changed at a second speed slower than the first speed.

3. The radio waves to be measured are used to transmit burst signals that are output at regular time intervals. The radio wave measuring device according to claim 2, characterized in that the control device performs the first scan at a speed that does not miss the radio waves used to transmit the burst signal, based on the beam width of the directional antenna and the time interval of the burst signal.

4. The control device includes: performing the first scan with a beam width of the directional antenna set to a predetermined first beam width; 2. The radio wave measuring device according to claim 1, wherein the second scanning is performed with a beam width of the directional antenna set to a second beam width narrower than the first beam width.

5. 5. The radio wave measuring device according to claim 4, wherein the directional antenna is a phased array antenna configured by arranging a plurality of antenna elements and capable of changing a beam width according to the number of antenna elements used.

6. 5. The radio wave measuring device according to claim 4, further comprising a stand to which the directional antenna can be detached, and a directional antenna having a beam width different between the first scanning and the second scanning is attached.

7. A radio wave measuring device according to any one of claims 1 to 6, a spectrum analyzer that analyzes a frequency spectrum of the radio wave received by the directional antenna of the radio wave measuring device to generate spectrum data; a data processing device that identifies the direction of arrival of radio waves at a measurement point where the radio wave measuring device is installed, based on the spectrum data acquired from the spectrum analyzer; A radio wave measurement system comprising:

8. At a measurement point, a first frequency spectrum is measured based on the received radio waves while changing the direction of the directional antenna at a predetermined first speed; when a radio wave having a received power greater than a predetermined threshold is detected in spectrum data obtained by analyzing the first frequency spectrum, a range in which a direction of the directional antenna is changed is limited to a certain range including the direction of arrival of the radio wave, and a second frequency spectrum is measured based on the received radio wave while changing the direction of the directional antenna at a second speed slower than the first speed; identifying an arrival direction of the radio wave at the measurement point from spectrum data obtained by analyzing the second frequency spectrum; Radio wave measurement method.

9. At a measurement point, a first frequency spectrum is measured based on the received radio waves while changing a direction of the directional antenna with a beam width of the directional antenna set to a predetermined first beam width; setting a beam width of the directional antenna to a second beam width narrower than the first beam width, and measuring a second frequency spectrum based on the received radio wave while changing the direction of the directional antenna; identifying an arrival direction of the radio wave at the measurement point from spectrum data obtained by analyzing the second frequency spectrum; Radio wave measurement method.

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