Distance measuring device

Abstract

Provided is a distance measurement device capable of selecting phase difference-based distance measurement and frequency spectrum-based distance measurement in accordance with the status of a signal transmitted and received to and from a communication device. A distance measuring device includes: a first distance measuring unit that measures a distance by a first distance measuring method based on a phase difference of a signal received from a transmission device, and outputs a first distance; a second distance measurement unit that measures a distance by a second distance measurement method based on the frequency spectrum of the signal received from the transmission device, and outputs a second distance; and a selection unit that selects the first distance or the second distance on the basis of the frequency spectrum, phase linearity, and the like of the signal received from the transmission device.

Description

Technical Field

[0001] The invention relates to a distance measuring device. Background Art

[0002] Conventionally, there is a distance measuring device that measures distance based on the phase difference of signals of multiple frequencies received from a transmitting device (see, for example, Patent Document 1). In addition, there is a distance measuring device that performs Fourier transform on a signal received from a transmitting device and measures distance based on the frequency spectrum (see, for example, Patent Document 2).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-197697

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 09-152478 Summary of the invention

[0007] Technical problem that the invention will solve

[0008] However, which of the distance measurement based on the phase difference and the distance measurement based on the frequency spectrum is appropriate depends on the condition of the signal received from the transmitting device (communication device), but it has not yet been distinguished and used according to the condition.

[0009] Therefore, an object is to provide a distance measuring device capable of selecting between distance measuring based on a phase difference and distance measuring based on a frequency spectrum according to the conditions of a signal transmitted or received with a communication device.

[0010] Means for solving technical problems

[0011] A distance measuring device according to an embodiment of the present invention includes: a first distance measuring unit that performs distance measurement by a first distance measuring method based on a phase difference of a signal received from a transmitting device and outputs a first distance; a second distance measuring unit that performs distance measurement by a second distance measuring method based on a frequency spectrum of the signal received from the transmitting device and outputs a second distance; and a selection unit that selects the first distance or the second distance based on the frequency spectrum distribution of the signal received from the transmitting device.

[0012] Effects of the Invention

[0013] A distance measuring device can be provided which can select distance measuring based on phase difference and distance measuring based on frequency spectrum according to the status of signals transmitted and received with a communication device. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 1 is a diagram showing a distance measuring device 100 according to an embodiment.

[0015] Figure 2 1 is a task diagram showing the processing in the smartphone 50 and the distance measuring device 100 .

[0016] Figure 3 It is a diagram for explaining the distance measurement performed by the first distance measuring unit 132.

[0017] Figure 4 It is a diagram for explaining the distance measurement performed by the first distance measuring unit 132.

[0018] Figure 5 It is a diagram for explaining the distance measurement performed by the second distance measuring unit 133.

[0019] Figure 6 3 is a diagram showing an example of a frequency spectrum after the second distance measuring unit 133 performs FFT.

[0020] Figure 7 This is a diagram for explaining the items that the selection unit 134 checks in order to determine that the environment is a multi-path environment.

[0021] Figure 8 1 is a diagram showing a flowchart illustrating a selection process executed by the selection unit 134 .

[0022] Fig.9A 1 is a diagram showing a flowchart of a selection process according to a modification example executed by the selection unit 134 .

[0023] Fig. 9B 1 is a diagram showing a flowchart of a selection process according to a modification example executed by the selection unit 134 . DETAILED DESCRIPTION

[0024] Hereinafter, an embodiment of a distance measuring device to which the present invention is applied will be described.

[0025] <Implementation Method>

[0026] Figure 1 FIG. 1 is a diagram showing a distance measuring device 100 according to an embodiment. Figure 1 , in addition to the distance measuring device 100, a smartphone 50 is also shown. The smartphone 50 is an example of a communication device that transmits and receives signals, and the distance measuring device 100 obtains the distance from the distance measuring device 100 to the smartphone 50 based on the signal transmitted and received with the smartphone 50 (performs distance measurement).

[0027] The distance measuring device 100 includes an antenna 110, a communication unit 120, and an MMC (Micro Computer) 130. The antenna 110 is connected to the communication unit 120 and receives a signal transmitted from the smartphone 50. In addition, here, the distance measuring device 100 includes a single antenna 110, but the distance measuring device 100 may include a plurality of antennas 110.

[0028] The communication unit 120 includes an AFE (Analog Front End), an AD (Analog to Digital) converter, etc., performs signal processing such as AD conversion on the signal received by the antenna 110 from the smartphone 50 , and outputs the signal to the MMC 130 .

[0029] The MMC 130 includes a transceiver processing unit 131, a first distance measuring unit 132, a second distance measuring unit 133, a selection unit 134, and a memory 135. The MMC 130 is implemented, as an example, by a microcomputer including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and an internal bus. The transceiver processing unit 131, the first distance measuring unit 132, the second distance measuring unit 133, and the selection unit 134 represent the functions of the program executed by the MMC 130 as functional blocks. In addition, the memory 135 functionally represents the memory of the MMC 130.

[0030] The transmission and reception processing unit 131 transmits and receives signals with the smartphone 50 in order to obtain data such as phase difference and frequency component required for the first distance measuring unit 132 and the second distance measuring unit 133 to perform distance measurement.

[0031] The first distance measuring unit 132 and the second distance measuring unit 133 perform distance measurement based on the ToA (Time Of Arrival) format. The first distance measuring unit 132 performs distance measurement based on the phase difference of the signal received from the smartphone 50, and outputs a first distance. The second distance measuring unit 133 performs distance measurement based on the frequency spectrum of the signal received from the smartphone 50, and outputs a second distance. In addition, TOA is a distance measurement method also called TOF (Time Of Flight).

[0032] The selection unit 134 selects the first distance output by the first distance measuring unit 132 or the second distance output by the second distance measuring unit 133 according to the state of the radio wave received by the antenna 110. Figure 8 Narrative.

[0033] The memory 135 stores the following programs and data, namely: the programs and data required for the transceiver processing unit 131 to execute the processing for sending and receiving signals; the programs and data required for the first ranging unit 132 and the second ranging unit 133 to execute the processing for ranging; the programs and data required for the selection unit 134 to execute the processing for selecting the first distance or the second distance, etc.

[0034] Figure 21 is a task diagram showing the processing in the smartphone 50 and the distance measuring device 100. First, as (1), in order to synchronize the smartphone 50 and the distance measuring device 100, the smartphone 50 transmits a CW (Continuous Wave) for synchronization, and the distance measuring device 100 receives the CW for synchronization. In the distance measuring device 100, the transmission and reception processing unit 131 performs reception processing.

[0035] Next, as (2), the smartphone 50 and the distance measuring device 100 hop to 64 frequencies while repeating the transmission of CW and the reception of IQ data alternately. In the distance measuring device 100, the transmission and reception processing unit 131 performs the transmission and reception processing. As an example, between 2.4 and 2.48 GHz, 64 channels are randomly hopped among 160 channels at intervals of 0.5 MHz.

[0036] Next, as (3), the smartphone 50 transmits IQ data and phases corresponding to 64 frequencies to the distance measuring device 100, and the distance measuring device 100 receives the data. In the distance measuring device 100, the transmission and reception processing unit 131 performs reception processing.

[0037] Finally, as (4), the distance measuring device 100 combines the phase on the smartphone 50 side with the phase on the distance measuring device 100 side, performs distance measurement (calculates distance) in two methods, namely, the first distance measuring method and the second distance measuring method, by ToA calculation, and selects the distance calculated by the distance measuring method suitable for the situation. The processing of (4) is performed by the first distance measuring unit 132, the second distance measuring unit 133, and the selection unit 134 in the distance measuring device 100.

[0038] <Distance Measurement by the First Distance Measuring Unit 132>

[0039] Figure 3 1 is a diagram for explaining the distance measurement performed by the first distance measuring unit 132. The distance measurement performed by the first distance measuring unit 132 is particularly effective when the signal strength of the direct path is high and the signal strength of the multipath is low.

[0040] like Figure 3 (A) Figure 3 As shown in (B), the phase when the distance measuring device 100 sends CW and the smartphone 50 receives it is set to θa, and the phase when the smartphone 50 sends CW and the distance measuring device 100 receives it is set to θb. That is, the phase difference between the phase received by the smartphone 50 and the phase when the distance measuring device 100 sends CW is θa, and the phase difference between the phase received by the distance measuring device 100 and the phase when the smartphone 50 sends CW is θb. It is assumed that the phase difference θa corresponds to the time ta, and the phase difference θb corresponds to the time tb.

[0041] The distance between the distance measuring device 100 and the smartphone 50 is defined as L, and the sum of the phase θa when sent from the distance measuring device 100 and received by the smartphone 50 and the phase θb ​​when sent from the smartphone 50 and received by the distance measuring device 100 is set as the round-trip phase θsum (= (θa+θb)×n). It is assumed that the phase difference θa is equivalent to the time ta, and the phase difference θb is equivalent to the time tb. n represents the number of CW waves (wavelengths) that travel back and forth between the distance measuring device 100 and the smartphone 50.

[0042] Here, let the speed of the radio wave be C, the frequency of the radio wave be f, and the period of the radio wave be T (=1 / f). The following (1) and (2) hold.

[0043]

Formula 1

[0044] 2L=C×(ta+tb) (1)

Formula 2

[0045] (ta+tb)={(θa+θb)×n / 360}×T (2)

[0046] Since (θa+θb)×n=θsum, equation (3) can be obtained from equation (1) and equation (2).

[0047]

Formula 3

[0048]

[0049] If equation (3) is transformed and sorted using θsum, equation (4) can be obtained.

[0050]

Formula 4

[0051]

[0052] The distance measuring device 100 and the smartphone 50 communicate back and forth at frequencies f1 and f2, and the round-trip phase difference θsum1 at frequency f1 and the round-trip phase difference θsum2 at frequency f2 are calculated. If the difference between θsum1 and θsum2 is used, the relationship between equations (5A) and (5B) can be obtained.

[0053]

Formula 5

[0054]

[0055] According to equations (5A) and (5B), the distance L can be calculated as shown in equation (6).

[0056]

Formula 6

[0057]

[0058] When the distance is measured at two frequencies, the distance L is expressed as in equation (6), but a slight phase error becomes a distance error, and the robustness is low. Therefore, if the distance is measured at multiple (M) frequencies, then Figure 3 (C) The result is like this. Figure 3 The graph shown in (C) shows the frequency f on the horizontal axis and the phase θa+θb of the radio wave when it goes back and forth on the vertical axis. Here, Δθsum / Δf in equation (6) shows the slope of the straight line, so the distance L can be expressed as in the following equation (7).

[0059]

Formula 7

[0060]

[0061] Thus, the distance L is proportional to the slope. The first distance measuring unit 132 performs distance measurement based on equation (6).

[0062] The distance measurement performed by the first distance measuring unit 132 is a method of measuring the distance based on the phase difference, and the round-trip phase between the distance measuring device 100 and the smartphone 50 is obtained at each frequency. Therefore, if there is a lot of noise due to the influence of multi-path, errors are likely to occur when the phases (phase differences) in all frequencies are added. In addition, in order to obtain the slope, there is a tendency that it is easier to calculate the slope for a short distance than for a long distance.

[0063] In order to explain the calculation principle, Figure 3 The θsum of (C) is a value greater than 360°, but in reality, when the MMC130 receives radio waves, the wave number is not included, so θsum takes a value of 0° to 360°. Figure 4 shown. Figure 4 It is a diagram for explaining the distance measurement performed by the first distance measuring unit 132.

[0064] like Figure 4 As shown in (A), θsum takes values ​​of 0° to 360°, and the data is a characteristic that changes repeatedly in a sawtooth wave shape. Figure 4 The data of (A) is as follows Figure 4 The distance L is calculated by converting the linear transformation process as shown in (B). The longer the distance, the more difficult it is to calculate the transformation process. This is because Figure 4 In the data of a short distance (5m as an example) such as (C), it is easy to see that the phase is linear, and the addition process of more than 360° is easy. However, if we observe the data of 15m as an example, Figure 4 The data of (D) and the case of 60m as an example Figure 4 From the data of (E), it can be seen that as the distance increases, the slope increases, making it difficult to see the linearity of the phase and making the addition process difficult.

[0065] Therefore, the distance measurement performed by the first distance measuring unit 132 is more suitable for a short distance than a long distance, and is more suitable for a direct path environment than a multi-path environment. Hereinafter, the distance measurement performed by the first distance measuring unit 132 is referred to as a direct path distance measurement method. The direct path distance measurement method is an example of the first distance measurement method.

[0066] <Distance Measurement by the Second Distance Measuring Unit 133>

[0067] Figure 5 1 is a diagram for explaining the distance measurement performed by the second distance measuring unit 133. The distance measurement performed by the second distance measuring unit 133 can be used even when the signal strength of the multipath is high and the signal strength of the direct path is low, and can be calculated relatively easily even when the smartphone 50 is relatively far from the distance measuring device 100.

[0068] The second distance measuring unit 133 transforms the IQ data of all 64 frequency quantities using the FFT (Fast Fourier Transform) function. Thus, as an example, it is possible to obtain Figure 5 The frequency spectrum results are shown. Figure 5 In the figure, the horizontal axis is the frequency f, which is equivalent to the distance, and the vertical axis is the signal strength.

[0069] The second distance measuring unit 133 is based on Figure 5 As a result of performing FFT transformation as shown, the frequency with sufficiently high signal strength and the lowest frequency is extracted as the frequency that provides the best peak. The reason for this is that the path of the direct path signal is shorter than that of the multi-path signal, so if the FFT transformation is performed, the direct path signal will inevitably become a lower frequency than the multi-path signal. By converting the selected frequency into a distance, the distance to the smartphone 50 is calculated.

[0070] More specifically, the number of sample buffers for FFT is set to N = 256, and the frequency interval freq_step is set to 0.5MHz. In the range of 2.4 to 2.48GHz, 64 channels can be randomly hopped among 160 channels at intervals of 0.5MHz. In addition, as an example, the number of sample buffers for FFT can be set to N = 256, and the frequency interval freq_step is set to 2MHz, and 40 channels can be hopped at intervals of 2MHz. IQ data is set for 40 of the sample buffers N = 256. If FFT is performed, the obtained Figure 5 result.

[0071] Based on the FFT result, the distance L can be calculated using the following equation (8).

[0072]

Formula 8

[0073]

[0074] The frequency fb at which the best peak can be obtained is a frequency that has a sufficient magnitude and at which a spectrum can be obtained at the lowest frequency. The horizontal axis of the FFT result takes discrete values, 0, 1, 2, ..., 127 (256 / 2-1), but the frequency component of the frequency fb is determined by interpolation based on the shape of the FFT waveform, so it becomes a decimal.

[0075] The distance measurement performed by the second distance measuring unit 133 is based on the frequency components of the signal received from the smartphone 50 and includes a transformation process using an FFT function. Therefore, the calculation is relatively easy even when the distance is long.

[0076] Therefore, the distance measurement performed by the second distance measuring unit 133 can be used even when the influence of the multi-path is large and the influence of the direct path is small, and can be relatively easily calculated even when the smartphone 50 is relatively far from the distance measuring device 100. Hereinafter, the distance measurement performed by the second distance measuring unit 133 is referred to as the multi-path distance measurement method. The multi-path distance measurement method is an example of the second distance measurement method. However, when the noise caused by the multi-path is large, calculation sometimes becomes difficult.

[0077] <Selection Processing by the Selecting Unit 134>

[0078] Figure 6 is a diagram showing an example of a frequency spectrum after the second distance measuring unit 133 performs FFT. Figure 6 , which explains whether the distance calculation can be performed and whether it is multi-path processing based on the signal received from the smartphone 50. Figure 6 In the graph, the horizontal axis represents frequency, and the vertical axis represents the amplitude (height) of the frequency spectrum.

[0079] The selection unit 134 uses the threshold of the signal strength to determine whether the distance calculation can be performed. Figure 6 As shown in (1), when the signal strength is less than the threshold E, it is determined that the selection unit 134 cannot perform distance calculation, such as Figure 6 As shown in (2), (3), (4), and (5), when the signal strength is greater than or equal to the threshold value E, the selection unit 134 determines that the distance calculation can be performed.

[0080] In addition, if Figure 6 As shown in (2) and (3) of FIG. 1 , when there is a peak with sufficiently large signal strength and the signal strength is greater than the threshold value E, the selection unit 134 determines that the environment is less affected by multipath and has more direct path components. Figure 6As shown in (4) of FIG. 1 , when there are multiple peaks with signal strengths above the threshold, the selection unit 134 determines that the environment is highly influenced by multipath. Figure 6 In the case where multiple peaks overlap to form one peak as in (5) of FIG. 1 , it is also determined that the environment is strongly affected by the multipath. However, there may be a case where it is difficult to determine whether it is the direct path or the multipath, so the selection unit 134 Figure 7 As shown, determination is made based on each part of the signal.

[0081] Figure 7 FIG. 1 is a diagram for explaining the items that the selection unit 134 checks in order to determine that the environment is a multi-path environment. Figure 7 In , the horizontal axis represents frequency and the vertical axis represents the amplitude (height) of the frequency spectrum. Figure 7 In FIG. 1 , the number of peaks of the frequency spectrum is shown as 3 as an example.

[0082] The selection unit 134 is as follows Figure 7 As shown, for the highest peak, the peak height, peak width, peak area, and number of peaks are extracted and used in the following Figure 8 It is used in step S2 to determine whether it is a multi-path environment or a direct path environment. The peak height is the height from the lowest point to the highest point of the highest peak. The peak width is the amplitude in the horizontal axis direction at the level of the threshold E of the peak height. The peak area is the area of ​​the part above the threshold E in the highest peak. The number of peaks is the number of peaks above the threshold E of the peak height.

[0083] The selection unit 134 determines whether it is a multi-path environment as follows. When there is a peak with a peak height greater than the threshold value E, the selection unit 134 determines that the peak width at the peak height threshold value E of the highest peak among the one or more extracted peaks is the bandwidth direction ( Figure 7 When the peak area is above the area threshold S, or the peak height is above the peak height threshold h, it is determined to be a direct path environment rather than a multi-path environment.

[0084] When there are a plurality of peaks with a peak height greater than or equal to the threshold value E, the selection unit 134 selects the peak width at the threshold value E of the peak height greater than the bandwidth direction ( Figure 7 In the case where the threshold value D of the distance measured by the direct path distance measurement method (the first distance) or the distance measured by the multi-path distance measurement method (the second distance) is greater than the threshold value D of the distance measured by the direct path distance measurement method (the horizontal axis direction), the peak area is less than the area threshold value S, or the peak height is less than the peak height threshold value h, it is determined that the environment is a multi-path environment. In addition, as to how the selection unit 134 specifically processes to select the distance measured by the direct path distance measurement method (the first distance) or the distance measured by the multi-path distance measurement method (the second distance), the following uses Figure 8 The flowchart is described below.

[0085] Figure 8 1 is a diagram showing a flowchart illustrating the selection process executed by the selection unit 134. As a premise, it is assumed that the first distance measuring unit 132 and the second distance measuring unit 133 measure the first distance and the second distance from the distance measuring device 100 to the smartphone 50 using the above-mentioned distance measuring method.

[0086] When the process starts, the selection unit 134 determines whether the distance calculation can be performed (step S1). Figure 6 When the distance is less than the threshold value E as shown in (1), the selection unit 134 determines that the distance calculation cannot be performed (S1: No), and the process enters step S10, and is determined to be an error (a state in which the distance calculation cannot be performed) (step S10).

[0087] On the other hand, if the selection unit 134 determines in step S1 that the distance calculation can be performed (S1: YES), the flow advances to step S1A. Figure 6 When the signal strength is above the threshold value E as shown in (2), (3), (4), and (5), the selection unit 134 determines that the distance calculation can be performed (S1: YES), and proceeds to step S2 via steps S1A and S1B. Specifically, it is as follows.

[0088] The first distance measuring unit 132 performs distance measurement using the direct path distance measuring method based on equation (6) to obtain the distance L (first distance) (step S1A).

[0089] The second distance measuring unit 133 performs distance measurement using a multi-pass distance measuring method based on equation (8) to obtain a distance L (a second distance) (step S1B).

[0090] The selection unit 134 performs FFT on the signal received from the smartphone 50 and determines whether it is a multi-path environment based on the obtained frequency spectrum (step S2). The determination of whether it is a multi-path environment refers to determining whether it is a multi-path environment (S2: YES) or a direct path environment (S2: NO). For example, the frequency spectrum of the signal is used to determine whether it is a multi-path environment. Figure 6 Direct access environment as shown in (2) and (3) of Figure 6 Which of the multi-path environments shown in (4) and (5)?

[0091] In step S2, it is determined that it is a multi-path environment (S2: YES) means that when it is determined that it is equivalent to Figure 6 In the case of (4) and (5), if you use Figure 7As described above, when there are multiple peaks with a peak height greater than the threshold value E, the peak width at the threshold value E of the peak height is greater than the bandwidth direction ( Figure 7 The case where the threshold D (in the horizontal axis direction) is large, the peak area is smaller than the area threshold S, or the peak height is smaller than the peak height threshold h.

[0092] If it is determined in step S2 that the environment is multi-path (S2: YES), the selection unit 134 selects the second distance calculated by the second distance measuring unit 133 using the multi-path distance measuring method (step S3). That is, the multi-path distance measuring method is used.

[0093] If the selection unit 134 determines that the environment is not a multi-path environment (S2: NO), it is a direct path environment, so it is possible to select either the result of the direct path ranging method or the result of the multi-path ranging method. Therefore, in order to determine the selectability of the direct path ranging method, the selection unit 134 determines whether the linearity of the phase of the signal received from the smartphone 50 is greater than a predetermined level (step S4).

[0094] The linearity of the phase of the signal received from the smartphone 50 is represented by a correlation coefficient indicating the correlation between frequency and phase as an example. For the phase of the CW obtained by hopping 64 frequencies, by finding the correlation coefficient indicating the correlation between frequency and phase, it is determined whether the linearity of the phase of the signal received from the smartphone 50 is above a specified level.

[0095] The correlation coefficient representing the correlation between frequency and phase can be represented by the absolute value of Pearson's correlation coefficient as an example. When the phase in each frequency falls on a straight line, the correlation is high (the correlation coefficient is large), and when the phase in each frequency deviates, the correlation is low (the correlation coefficient is small). The correlation coefficient is represented by the slope of the straight line representing the correlation between frequency and phase.

[0096] The closer the absolute value of the correlation coefficient is to 1, the stronger the correlation is (the higher the degree of linearity), and the closer it is to 0, the weaker the correlation is (the lower the degree of linearity). When the absolute value of the correlation coefficient is close to 1, the direct path ranging method is suitable. The absolute value of the correlation coefficient of frequency and phase is close to 1, which means that the direct path ranging method can be used to measure from low frequency to high frequency, that is, from short distance to long distance. Therefore, when the absolute value of the correlation coefficient is close to 1, the direct path ranging method is suitable. In addition, the direct path ranging method is suitable for short-distance measurement. Therefore, if it is determined in step S2 that it is not a multi-path environment (S2: No (NO)), then proceed to step S4. If the determinations of steps S4, S5, S6, S7, and S9 are all yes (YES), the distance L (first distance) obtained by the distance measurement of the direct path ranging method is used. That is, if there is basically linearity and it is a short distance, the direct path ranging method is used.

[0097] In addition, when the Pearson's correlation coefficient (not the absolute value) takes a positive value, it is an abnormal state that the distance finally obtained by the direct path distance measurement method is a negative value, so the direct path distance measurement method does not need to be used.

[0098] The predetermined degree used for determination in step S4 may be set to a value close to 1, such as 0.9 to 1, for example. In step S4 , it may be determined whether a value other than an absolute value is a negative value.

[0099] When the selection unit 134 determines in step S4 that the linearity of the phase of the signal received from the smartphone 50 is less than a predetermined degree (S4: NO), the process proceeds to step S3. This is because it is not appropriate to adopt the direct path ranging method. In addition, when the Pearson's correlation coefficient (not the absolute value) takes a positive value, the selection unit 134 also allows the process to proceed to step S3. As a result, the second distance obtained by the multi-path ranging method is selected.

[0100] If the selection unit 134 determines in step S4 that the linearity of the phase of the signal received from the smartphone 50 is greater than a predetermined level (S4: YES), it determines whether the number of valid phase data in the predetermined frequency band is greater than a predetermined number (step S5). This is to confirm whether the direct path ranging method can be selected.

[0101] The prescribed frequency band is, for example, a WiFi communication band. If the signal received from the smartphone 50 is affected by, for example, WiFi radio waves, there is no received signal in the WiFi communication band alone, and the phase data is missing or the deviation is large. If these conditions occur, it is difficult to properly calculate the distance using the direct path ranging method, so the direct path ranging method may not be used.

[0102] The predetermined frequency band in the determination of step S5 may be determined in advance based on the relationship between the frequency band used for communication between the distance measuring device 100 and the smartphone 50 and the frequency band of WiFi or the like that may exist in the surroundings.

[0103] The predetermined number of valid phase data in the determination of step S5 may be determined by obtaining in advance through experiments or simulations the number required to appropriately calculate the distance using the direct path ranging method.

[0104] In step S5, if the number of valid phase data in the specified frequency band is less than the specified number (S5: NO), the selection unit 134 advances the flow to step S3. This is because it is not appropriate to adopt the direct path ranging method. As a result, the second distance obtained by the multi-path ranging method is selected.

[0105] If the selection unit 134 determines in step S5 that the number of valid phase data in the specified frequency band is greater than the specified number (S5: YES), it determines whether the second distance measured by the second distance measuring unit 133 is greater than the specified distance (step S6). As described above, the direct path distance measurement method is more suitable for short-distance distance measurement than long-distance distance measurement. Therefore, as an example, the specified distance is set to 30m for determination.

[0106] If the selection unit 134 determines that the second distance measured by the second distance measuring unit 133 is less than the predetermined distance (S6: NO), it determines whether the difference between the first distance measured by the first distance measuring unit 132 and the second distance measured by the second distance measuring unit 133 is less than a second predetermined difference (step S7).

[0107] The small difference between the first distance measured by the first distance measuring unit 132 and the second distance measured by the second distance measuring unit 133 indicates that the accuracy of the distance measurement by the first distance measuring unit 132 and the second distance measuring unit 133 is high. When the process proceeds to step S7 via steps S4 to S6, the condition that the direct path distance measurement method is more suitable than the multi-path distance measurement method is satisfied. Therefore, the difference between the first distance and the second distance determined in step S7 indicates whether the quality of the direct path is high. The small difference between the first distance and the second distance indicates that the quality of the direct path is high, and the large difference between the first distance and the second distance indicates that the quality of the direct path is low.

[0108] If the selection unit 134 determines that the difference between the first distance and the second distance is less than the second predetermined difference (S7: YES), the first distance output by the first distance measuring unit 132 is selected (step S8). That is, the first distance measured by the direct path distance measurement method is selected. This is because the difference between the first distance and the second distance is smaller than the second predetermined difference, and the quality of the direct path is higher.

[0109] If the selection unit 134 determines in step S7 that the difference between the first distance and the second distance is greater than the second predetermined difference (S7: NO), the flow advances to step S3. This is because the quality of the direct path is low. As a result, the second distance obtained by the multi-path distance measurement method is selected.

[0110] In addition, if the selection unit 134 determines in step S6 that the second distance measured by the second distance measuring unit 133 is greater than the specified distance (S6: YES), it determines whether the difference between the first distance measured by the first distance measuring unit 132 and the second distance measured by the second distance measuring unit 133 is less than the first specified difference (step S9).

[0111] If the selection unit 134 determines in step S9 that the difference between the first distance and the second distance is not less than the first predetermined difference (S9: NO), the process proceeds to step S3. This is because, although the process proceeds to step S9 via steps S4 to S6, the conditions that the direct path distance measurement method is more suitable than the multi-path distance measurement method are met, the direct path distance measurement method is not suitable because the quality of the direct path is low. As a result, the second distance obtained by the multi-path distance measurement method is selected.

[0112] Here, the first prescribed difference used in the determination of step S9 may be larger than the second prescribed difference used in the determination of step S7. In other words, the second prescribed difference used in the determination of step S7 may be smaller than the first prescribed difference used in the determination of step S9. The case of proceeding to step S9 is when it is determined in step S6 that the second distance measured by the second distance measuring unit 133 is greater than the prescribed distance (S6: YES), and the case of proceeding to step S7 is when it is determined in step S6 that the second distance measured by the second distance measuring unit 133 is less than the prescribed distance (S6: NO).

[0113] The longer the distance between the distance measuring device 100 and the smartphone 50 (the longer the distance), the smaller the proportion of the distance difference in the total distance, and the shorter the distance between the distance measuring device 100 and the smartphone 50 (the closer the distance), the larger the proportion of the distance difference in the total distance. Therefore, as an example, in order to make the determination in the close distance a stricter condition, the second prescribed difference used in the determination of step S7 is made smaller than the first prescribed difference used in the determination of step S9, and the first prescribed difference used in the determination of step S9 is made larger than the second prescribed difference used in the determination of step S7. In addition, the first prescribed difference being larger than the second prescribed difference is an example, and the first prescribed difference may also be smaller than the second prescribed difference.

[0114] If the selection unit 134 determines in step S9 that the difference between the first distance and the second distance is less than the first predetermined difference (S9: YES), the flow advances to step S8. This is because the quality of the direct path is high despite the long distance. As a result, the first distance obtained by the direct path distance measurement method is selected.

[0115] As described above, the selection unit 134 selects the first distance or the second distance based on the result of FFT processing of the IQ data transmitted and received between the smartphone 50 and the distance measuring device 100 , the linearity of the phase, and the like.

[0116] Therefore, it is possible to provide a distance measuring device 100 that can select a first distance measuring method based on a phase difference and a second distance measuring method based on a frequency component of an FFT calculation result according to the state of a signal transmitted and received with the smartphone 50 .

[0117] In addition, the selection unit 134 determines whether it is a multi-path environment based on the number of peaks, peak heights, or peak areas in the frequency spectrum after the second distance measuring unit 133 performs FFT, and selects the second distance obtained by the multi-path distance measuring method when it is determined to be a multi-path environment. Therefore, a distance measuring device 100 that appropriately selects the second distance measured by the multi-path distance measuring method in the case of a multi-path environment can be provided.

[0118] In addition, in the frequency spectrum after the second distance measuring unit 133 performs FFT, when there are multiple peaks above the threshold value of the peak height, when the peak width at the threshold value E of the peak height is larger than the threshold value in the bandwidth direction, when the peak area is smaller than the area threshold value S, or when the peak height is smaller than the threshold value h of the peak height, the selection unit 134 determines that it is a multi-path environment. Therefore, the following distance measuring device 100 can be provided: it is possible to use the threshold value E of the peak height, the area threshold value S of the peak area, and the threshold value h of the peak height to reliably determine whether it is a multi-path environment, and in the case of a multi-path environment, appropriately select the second distance measured by the multi-path distance measurement method.

[0119] In addition, even if the number of multiple peaks in the frequency spectrum after the second distance measuring unit 133 performs FFT is not more than the prescribed number, when the degree of linearity of the phase of the signal received from the smartphone 50 is less than the prescribed degree, the selection unit 134 selects the second distance obtained by the multi-path distance measurement method. When the degree of linearity is less than the prescribed degree, the absolute value of the correlation coefficient is small, and it is not suitable for the direct path distance measurement method. Therefore, the distance measuring device 100 that appropriately selects the second distance measured by the multi-path distance measurement method can be provided. Even if it is determined that it is not a multi-path environment in step S2, as long as the linearity of the frequency and the phase is less than the prescribed degree in step S4, it means that it is not suitable for the measurement of the direct path distance measurement method in a part of the frequency band from the lower frequency to the higher frequency or in the frequency band of all frequencies. Therefore, if it is determined that it is not a multi-path environment in step S2 (S2: No (NO)) and once it proceeds to step S4, if it is determined that it is a multi-path environment in any of the determinations of steps S4, S5, S6, S7, and S9, it is determined that it is a multi-path environment and the multi-path distance measurement method is adopted. If there is basically no linearity or the distance is long, a multi-channel ranging method is used.

[0120] In addition, even if the linearity of the phase of the signal received from the smartphone 50 is above a predetermined level, when the number of valid phase data in the predetermined frequency band is less than a predetermined number, the selection unit 134 selects the second distance obtained by the multi-path ranging method. For example, if there is no received signal in the communication frequency band of WiFi only and the phase data is missing or the deviation is large, it is difficult to properly calculate the distance by the direct path ranging method, and therefore, a distance measuring device 100 that selects the second distance obtained by the multi-path ranging method that is more suitable for such a situation can be provided.

[0121] In addition, even if the number of valid phase data in the prescribed frequency band is greater than the prescribed number, when the second distance measured by the second distance measuring unit 133 is greater than the prescribed distance, the selection unit 134 selects the second distance obtained by the multi-path distance measurement method. The direct path distance measurement method is more suitable for short-distance distance measurement than for long-distance distance measurement, and thus a distance measurement device 100 that can select a multi-path distance measurement method that can also cope with long-distance distance measurement can be provided.

[0122] In addition, even if the second distance measured by the second distance measuring unit is greater than the predetermined distance, when the difference between the first distance measured by the first distance measuring unit and the second distance measured by the second distance measuring unit is greater than the first predetermined difference, the selection unit 134 selects the second distance obtained by the multi-path distance measurement method. The quality of the direct path is low, and it is not appropriate to use the direct path distance measurement method. Therefore, a distance measurement device 100 that selects the multi-path distance measurement method when the quality of the direct path is low can be provided.

[0123] In addition, even if the number of valid phase data in the prescribed frequency band is greater than the prescribed number and the second distance measured by the second distance measuring unit is less than the prescribed distance, when the difference between the first distance measured by the first distance measuring unit and the second distance measured by the second distance measuring unit is greater than the second prescribed difference, the selection unit 134 selects the second distance obtained by the multi-path distance measurement method. Since the quality of the direct path is low, it is not appropriate to use the direct path distance measurement method, and therefore, a distance measurement device 100 that selects the multi-path distance measurement method when the quality of the direct path is low can be provided.

[0124] In addition, when the number of valid phase data in the prescribed frequency band is greater than or equal to a prescribed number, the second distance measured by the second distance measuring unit is less than a prescribed distance, and the difference between the first distance measured by the first distance measuring unit and the second distance measured by the second distance measuring unit is less than a second prescribed difference, the selection unit 134 selects the first distance obtained by the direct path distance measurement method. A distance measuring device 100 can be provided that selects the first distance obtained by the direct path distance measurement method when a plurality of conditions (steps S2 to S6) for selecting the direct path distance measurement method are satisfied and the quality of the direct path is high.

[0125] In addition, the first predetermined difference is larger than the second predetermined difference. The longer the distance between the distance measuring device 100 and the smartphone 50 (the longer the distance), the smaller the proportion of the distance difference in the total distance, and the shorter the distance between the distance measuring device 100 and the smartphone 50 (the closer the distance), the larger the proportion of the distance difference in the total distance. Therefore, by making the first predetermined difference larger than the second predetermined difference, the determination in the close distance can be made into a stricter condition.

[0126] <Selection Process of Modification>

[0127] Fig.9A as well as Fig. 9B 1 is a diagram showing a flowchart of a selection process according to a modification example executed by the selection unit 134 .

[0128] Fig.9A The process shown represents the Figure 8 The processing after the processing of step S5 is deleted from the flowchart shown. Fig.9A In the embodiment, if the selection unit 134 determines in step S2 that it is not a multi-path environment but a direct path environment (S2: NO), and in step S4 determines that the linearity of the phase of the signal received from the smartphone 50 is greater than a prescribed degree (S4: YES), the processing proceeds to step S6 to determine whether the second distance measured by the second distance measuring unit 133 is greater than a prescribed distance (step S6). In this way, the selection unit 134 may not pass through the direct path environment (S2: NO) when determining that it is a direct path environment. Figure 8The process proceeds from step S4 to step S6 by performing the process of step S5 shown in the figure.

[0129] in addition, Fig. 9B The process shown represents the Figure 8 The processing after the processing of step S4 is deleted from the flowchart shown. Fig. 9B If the selection unit 134 determines in step S2 that it is not a multi-path environment but a direct path environment (S2: No), the process proceeds to step S5 to determine whether the number of valid phase data in the specified frequency band is greater than the specified number (step S5). If the selection unit 134 determines that the number of valid phase data in the specified frequency band is greater than the specified number (S5: Yes), it determines whether the second distance measured by the second distance measuring unit 133 is greater than the specified distance (step S6). In this way, when the selection unit 134 determines that it is a direct path environment (S2: No), the process can be skipped. Figure 8 The process proceeds from step S2 to step S5 by performing the process of step S4 shown in the figure.

[0130] As mentioned above, the distance measuring device according to the exemplary embodiment of the present invention has been described, but the present invention is not limited to the specifically disclosed embodiment, and various modifications and changes can be made without departing from the scope of the claims.

[0131] In addition, the present international application claims priority based on Japanese patent application No. 2022-098457 filed on June 17, 2022, the entire contents of which are incorporated herein by reference.

[0132] Description of Reference Numerals

[0133] 50 Smartphone

[0134] 100 Distance measuring device

[0135] 110 Antenna

[0136] 120 Ministry of Communications

[0137] 130MMC

[0138] 131 Transceiver Processing Department

[0139] 132 First Distance Measurement Unit

[0140] 133 Second Distance Measurement Unit

[0141] 134 Selection Department

[0142] 135 Memory

Claims

1. A distance measuring device, wherein: include: A first distance measuring unit that measures distance using a first distance measuring method based on a phase difference between a signal transmitted and received by the communication device, and outputs a first distance; a second distance measuring unit that measures distance using a second distance measuring method based on a frequency spectrum of the signal transmitted and received with the communication device, and outputs a second distance; as well as The selection unit selects the first distance or the second distance based on a frequency spectrum of the signal transmitted and received with the communication device.

2. The distance measuring device according to claim 1, wherein: The selection unit, Determine whether it is a multi-path environment based on the number of peaks, peak heights, or peak areas in the frequency spectrum of the signal, When it is determined that the environment is the multi-path environment, the second distance is selected.

3. The distance measuring device according to claim 2, wherein: When there are multiple peaks with peak heights above a threshold in the frequency spectrum of the signal, when the peak width at the threshold of the peak height is larger than the threshold in the bandwidth direction, when the peak area is smaller than the area threshold, or when the peak height is smaller than the threshold of the peak height, the selection unit determines that it is a multi-path environment.

4. The distance measuring device according to claim 2, wherein: When it is determined that the multipath environment is not the multipath environment, the selection unit selects the second distance when the degree of linearity of the phase of the signal transmitted to and received from the communication device is less than a predetermined degree.

5. The distance measuring device according to claim 2, wherein: When the number of valid phase data in a predetermined frequency band is less than a predetermined number, the selection unit selects the second distance.

6. The distance measuring device according to claim 2, wherein: When it is determined that the multipath environment is not the multipath environment, the selection unit determines whether the second distance measured by the second distance measuring unit is greater than a predetermined distance when the number of valid phase data in a predetermined frequency band is greater than a predetermined number.

7. The distance measuring device according to claim 2, wherein: When it is determined that the multipath environment is not the multipath environment, the selection unit determines whether the second distance measured by the second distance measuring unit is greater than a predetermined distance when the degree of linearity of the phase of the signal transmitted to and received from the communication device is greater than a predetermined degree.

8. The distance measuring device according to claim 6 or 7, wherein: Even if the second distance measured by the second distance measuring unit is greater than a predetermined distance, the selection unit selects the second distance when the difference between the first distance measured by the first distance measuring unit and the second distance measured by the second distance measuring unit is greater than a first predetermined difference.

9. The distance measuring device according to claim 6 or 7, wherein: The selection unit selects the first distance when the second distance measured by the second distance measuring unit is greater than a predetermined distance and a difference between the first distance measured by the first distance measuring unit and the second distance measured by the second distance measuring unit is less than a first predetermined difference.

10. The distance measuring device according to claim 6 or 7, wherein: Even if the second distance measured by the second distance measuring unit is smaller than a predetermined distance, the selection unit selects the second distance when the difference between the first distance measured by the first distance measuring unit and the second distance measured by the second distance measuring unit is greater than a second predetermined difference.

11. The distance measuring device according to claim 6 or 7, wherein: The selection unit selects the first distance when the second distance measured by the second distance measuring unit is smaller than a predetermined distance and a difference between the first distance measured by the first distance measuring unit and the second distance measured by the second distance measuring unit is smaller than a second predetermined difference.

12. The distance measuring device according to claim 6 or 7, wherein: The selection unit is configured to select the second distance even if the second distance measured by the second distance measuring unit is greater than a prescribed distance, but the difference between the first distance measured by the first distance measuring unit and the second distance measured by the second distance measuring unit is greater than a first prescribed difference, or select the second distance even if the second distance measured by the second distance measuring unit is less than the prescribed distance, but the difference between the first distance measured by the first distance measuring unit and the second distance measured by the second distance measuring unit is greater than a second prescribed difference, The first prescribed difference is greater than the second prescribed difference.

13. The distance measuring device according to claim 6 or 7, wherein: The selection unit is configured to select the first distance when the second distance measured by the second distance measuring unit is greater than a prescribed distance and a difference between the first distance measured by the first distance measuring unit and the second distance measured by the second distance measuring unit is less than a first prescribed difference, or to select the first distance when the second distance measured by the second distance measuring unit is less than the prescribed distance and a difference between the first distance measured by the first distance measuring unit and the second distance measured by the second distance measuring unit is less than a second prescribed difference. The first prescribed difference is greater than the second prescribed difference.

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