Distance measurement device and distance measurement method

Abstract

[Problem] To achieve appropriate distance measurement. [Solution] This distance measurement device comprises a transmission unit, a reception unit, a determination circuit, a signal generation circuit, and a measurement circuit. The transmission unit transmits a first signal that is a chirp signal to the outside. The reception unit receives a second signal from the outside. The determination circuit determines whether the second signal is related to a reflected wave of the first signal on the basis of the result of comparison of the first signal and the second signal. When it is determined that the second signal is not related to a reflected wave of the first signal, the signal generation circuit changes the characteristics of the first signal outputted from the transmission unit and outputs the changed first signal. When it is determined that the second signal is related to a reflected wave of the first signal reflected in a single path, the measurement circuit estimates and outputs the position of an external object according to a beat frequency in the first signal and the second signal.

Description

Distance measuring device and distance measuring method

[0001] The present disclosure relates to a distance measuring device and a distance measuring method.

[0002] Frequency Modulated Continuous Wave (FMCW) radar is a radar that modulates the frequency of a continuous wave to determine distance from the beat frequency of the transmitted wave and the reflected wave. This FMCW radar is installed on moving objects such as automobiles and is used to detect obstacles, etc.

[0003] The transmission waves used in this FMCW radar are chirp signals whose frequency is controlled to gradually increase or decrease. When multiple FMCW radar devices are present and there is a possibility that the FMCW devices may receive the transmission waves of other devices due to passing each other, it is difficult to determine whether the received signal is a signal that was reflected by an object or a signal that was directly transmitted from another FMCW device. As a result, there is a problem in that accurate ranging cannot be achieved.

[0004] Japanese Patent Publication No. 2020-190573

[0005] Therefore, one of the non-limiting problems that the embodiments of the present disclosure aim to solve is to realize appropriate ranging. The problem that the embodiments of the present disclosure aim to solve can also be, as some further non-limiting examples, a problem corresponding to the effects described in the embodiments. In other words, a problem that corresponds to at least one of the effects described in the description of the embodiments of the present disclosure can be the problem that the present disclosure aims to solve.

[0006] According to one embodiment, a distance measuring device includes a transmitter, a receiver, a determination circuit, a signal generation circuit, and a measurement circuit. The transmitter transmits a first signal, which is a chirp signal, to the outside. The receiver receives a second signal from the outside. The determination circuit determines whether the second signal is a signal related to a reflected wave of the first signal based on a comparison result between the first signal and the second signal. If the signal generation circuit determines that the second signal is not a signal related to a reflected wave of the first signal, it changes the characteristics of the first signal output from the transmitter and outputs the first signal. If the measurement circuit determines that the second signal is a signal related to a reflected wave of the first signal reflected in a single path, it estimates the position of an external object from the beat frequency between the first signal and the second signal and outputs the estimated position.

[0007] The determination circuit may determine that the second signal is a signal related to a reflected wave of the first signal reflected externally in a single path, a signal related to a reflected wave of the first signal reflected externally in multiple paths, or a signal transmitted from a transmission source different from that of the first signal.

[0008] The determination circuit may determine that the second signal is a signal transmitted from a different transmission source than the first signal when the second signal has a different frequency modulation than the first signal.

[0009] The determination circuit may determine that the second signal is a signal transmitted from a different transmission source than the first signal when the second signal has a frequency in a different frequency band than the first signal.

[0010] The determination circuit may determine that the second signal is a signal transmitted from a different transmission source than the first signal when the second signal has a different period from the period of the first signal.

[0011] The determination circuit may determine that the second signal is a signal transmitted from a different transmission source than the first signal when the second signal has a frequency modulation gradient different from a frequency modulation gradient in the first signal.

[0012] The determination circuit may set a threshold value for a parameter of frequency modulation of the first signal, and if the deviation of the second signal from the parameter is equal to or less than the threshold value, determine that the first signal is a signal related to a reflected wave reflected from outside.

[0013] The determination circuit may determine that the first signal is a signal related to a reflected wave reflected by multipath outside when the second signal is not received within a predetermined time after the first signal is transmitted and has the same frequency modulation as the first signal.

[0014] The signal generating circuit may change an initial value of the frequency of the first signal when it is determined that the second signal is not a signal related to a reflected wave of the first signal.

[0015] The signal generating circuit may add or subtract a random number to or from the initial value of the frequency.

[0016] The signal generating circuit may set an initial value of the frequency of the first signal so that at least a portion of the frequency band is different from the frequency band of the second signal.

[0017] The signal generating circuit may set an initial value of the frequency of the first signal so that, for a predetermined time after the receiving unit receives the second signal, the frequency band of at least a portion of the first signal has a frequency different from that of the frequency band of the second signal.

[0018] The signal generating circuit may set the period of the first signal to be different from the period of the second signal.

[0019] The signal generating circuit may change the characteristics of the first signal if it is determined that the second signal is not a signal related to a reflection of the first signal, even during generation of the first signal.

[0020] According to one embodiment of a ranging method, in a ranging device comprising: a transmitting unit that transmits a first signal, which is a chirp signal, to the outside; and a receiving unit that receives a second signal from the outside, a determination circuit compares the first signal with the second signal to determine whether the second signal is a signal related to a reflected wave of the first signal; a signal generating circuit, when determining that the second signal is not a signal related to a reflected wave of the first signal, changes the characteristics of the first signal output from the transmitting unit and outputs it; and a measurement circuit, when determining that the second signal is a signal related to a reflected wave of the first signal reflected in a single path, estimates and outputs the position of an external object from the beat frequency between the first signal and the second signal.

[0021] At least a part of the above method may be performed by a program executed by a processing circuit.

[0022] 1 is a diagram schematically illustrating an overview of a distance measuring device according to an embodiment. A diagram schematically illustrating signals used for distance measuring according to an embodiment. A diagram showing the frequency characteristics of a chirp signal according to an embodiment. A diagram showing an example of transmitted and received signals according to an embodiment. A diagram showing the frequency characteristics of transmitted and received chirp signals according to an embodiment. A diagram showing an example of the frequency-intensity characteristics of a synthesized signal according to an embodiment. A block diagram showing an example of a distance measuring device according to an embodiment. A flowchart showing processing of a distance measuring device according to an embodiment. A flowchart showing determination processing according to an embodiment. A diagram schematically illustrating an example of signal parameter change according to an embodiment. A diagram schematically illustrating an example of signal parameter change according to an embodiment. A block diagram showing an example of the general configuration of a vehicle control system. An explanatory diagram showing an example of the installation positions of an outside vehicle information detection unit and an imaging unit.

[0023] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The drawings are used for explanation purposes, and the shape, size, and size ratio of each component in an actual device do not necessarily have to be the same as those shown in the drawings. Furthermore, since the drawings are simplified, components necessary for implementation other than those shown in the drawings are also assumed to be appropriately provided.

[0024] 1. Range Finder Using FMCW Figure 1 is a diagram showing a schematic overview of a range finder according to an embodiment. The range finder 1 includes a transmitter 10, a receiver 12, and a measurement circuit 14.

[0025] The transmitter 10 transmits the set signal (first signal) to the outside. The transmitter 10 forms and emits a signal based on parameters set inside the distance measuring device 1, for example. The signal may be formed by light, which may include infrared light, radio waves, sound waves, or the like.

[0026] In the present disclosure, the signal may be a chirp signal (frequency-modulated continuous wave) that generates a swell by interfering with a transmitted wave and a received wave (reflected wave), and may be, for example, a linear chirp signal whose frequency increases over time, a linear chirp signal whose frequency decreases over time, or some other chirp signal.

[0027] The receiving unit 12 receives a signal (second signal) from the outside. In particular, the receiving unit 12 receives a signal related to a reflected wave that is generated when a signal such as light emitted by the transmitting unit 10 is reflected by an external object.

[0028] The measurement circuit 14 generates an undulation by combining the first signal transmitted by the transmitter 10 and the second signal received by the receiver 12 to cause interference. The measurement circuit 14 detects the period of the interference wave as a beat frequency, and based on this beat frequency, detects the phase difference between the first signal and the second signal.

[0029] FIG. 2 is a diagram schematically illustrating a signal used in ranging according to an embodiment. FIG. 2 is a diagram illustrating an example of a non-limiting first signal used in the present disclosure. The first signal may be a signal whose frequency increases over time. Of course, as described above, the first signal is not limited to this signal, and may be a signal whose frequency decreases over time, or another chirp signal. Note that the chirp signal is not limited to the curve shown in the drawing, and as an example, it may be a curve whose frequency monotonically increases in a broad sense. Of course, as described above, other signals may also be used.

[0030] The distance measuring device 1 outputs a chirp signal from the transmitter 10 and receives the reflected chirp signal at the receiver 12. The measurement circuit 14 obtains a beat frequency from the composite wave of the transmitted signal from the transmitter 10 and the received signal from the receiver 12, thereby estimating the distance to the object that reflected the signal.

[0031] Figure 3 shows the signal characteristics of the example in Figure 2 in terms of the relationship between frequency and time. The chirp signal in Figure 2 is shown as the line segment Slope in Figure 3, for example. The frequency at the start point of this line segment is the initial value fc of the chirp signal. The time width of this line segment indicates the period Tc of the chirp signal, and the frequency width indicates the bandwidth of the chirp signal.

[0032] For example, in the case of linear frequency modulation, the chirp signal can be expressed by an initial frequency value fc, a bandwidth B, and a period Tc. A first signal spanning this period Tc is repeatedly transmitted from the transmitting unit 10. For example, the frequency f from a certain time t0 to t0 + Tc can be expressed as follows:

[0033] 4 is a diagram showing an example of a first signal transmitted by the distance measuring device 1 and a second signal received by the distance measuring device 1. In this diagram, the second signal is the first signal that has been reflected by an object outside in a single pass. Single pass refers to a state in which the first signal returns after one external reflection, while multi-pass refers to a state in which the first signal returns after multiple external reflections.

[0034] The solid line indicates the first signal, and the dashed line indicates the second signal. The distance measuring device 1 causes interference by superimposing the first signal it transmits and the second signal received as a reflected wave. The closer the reflected object, the smaller the time difference between the first signal and the second signal arriving at the measuring circuit 14; the farther the reflected object, the larger the time difference. When using a chirp signal that changes linearly, the difference in frequency between the first signal and the second signal becomes smaller as the time difference becomes smaller, and becomes larger as the time difference becomes larger.

[0035] Figure 5 shows the frequency-time characteristics of these signals. As in Figure 4, the solid line represents the first signal and the dashed line represents the second signal. The frequency difference Δf between the first and second signals at the same time is represented by the difference in the vertical axis of the frequency characteristics showing each signal, as shown in this figure.

[0036] The frequency difference Δf decreases as the time difference of the second signal as a reflected wave relative to the first signal decreases, i.e., as the dashed line segment moves toward the solid line segment in the negative time direction.Similarly, the frequency difference Δf increases as the phase difference of the second signal as a reflected wave relative to the first signal increases, i.e., as the dashed line segment moves toward the positive time direction in the opposite direction to the solid line segment.

[0037] For example, if the timing when the measurement circuit 14 detects the start of the period of the first signal is t1 and the timing when the measurement circuit 14 detects the start of the period of the second signal is t2, the frequency difference Δf between the first signal and the second signal can be expressed as follows:

[0038] As a result, the measurement circuit 14 can estimate the distance to the object that reflected the first signal by detecting the beat frequency in the interference wave, which indicates the difference in frequency between the first and second signals. To detect the beat frequency, the measurement circuit 14 combines the first and second signals and performs a Fourier transform (e.g., applies an FFT (Fast Fourier Transform)) on this combined wave.

[0039] Figure 6 shows the intensity-frequency characteristics of the composite wave of the first and second signals. This graph can be obtained by Fourier transforming the composite wave of the first and second signals. When the composite wave is Fourier transformed, a graph appears with a peak at the beat frequency (= frequency difference Δf) due to its undulation characteristics. The measurement circuit 14 obtains the beat frequency from this Fourier transformed graph and estimates the distance to the object using the following equation.

[0040] Here, c represents the speed of light. Although the Doppler effect is not taken into consideration in the above, it is of course possible to perform more accurate distance measurement in the distance measurement of this disclosure by performing a general process of correcting the Doppler shift.

[0041] Next, a description will be given of a method for determining whether the second signal is a reflected wave of the first signal, and a method for improving distance measurement accuracy when the second signal is not a reflected wave of the first signal.

[0042] 7 is a diagram showing a non-limiting example of a distance measuring device according to an embodiment. The distance measuring device 1 includes a transmitter 10, a receiver 12, a measurement circuit 14, a determination circuit 16, a signal generation circuit 18, and a storage device 20. The distance measuring device 1 measures the distance to an object using the distance measuring method described above, and if the second signal is not a reflected wave of the first signal, changes the parameters of the first signal transmitted from the transmitter 10 to clarify the difference with the signal oscillated in an external device, thereby improving distance measurement accuracy.

[0043] The transmitter 10 generates a first signal, which is a chirp signal, and outputs it to the outside. In addition to the above embodiment, in this embodiment, the transmitter 10 generates the first signal based on parameters set in the signal generation circuit 18. As another example, the transmitter 10 can output the signal generated in the signal generation circuit 18.

[0044] The receiving unit 12 receives a signal from the outside, for example, a signal related to a wave reflected from outside of the first signal outputted to the outside by the transmitting unit 10 .

[0045] The determination circuit 16 is a circuit that compares the first signal with the second signal and determines, based on the comparison result, whether the second signal is the first signal that has been reflected externally. Alternatively, the determination circuit 16 may be a circuit that determines whether the second signal is the first signal that has been reflected externally only once, that is, whether the second signal is a single-path first signal or a multi-path first signal.

[0046] In other words, based on the comparison result between the first signal and the second signal, the determination circuit 16 determines whether the second signal is a signal that has been reflected from an external object in a single path, a signal that has been reflected in multiple paths, or a signal that is different from the first signal.

[0047] The signal generation circuit 18 is a circuit that controls parameters related to the first signal based on the determination result of the determination circuit 16. For example, when the determination circuit 16 determines that the second signal is not an external reflected wave of the first signal (whether single-path or multi-path) but a signal transmitted from another device, the signal generation circuit 18 changes the parameters of the first signal from the current parameters and generates a first signal having characteristics different from those of the external signal.

[0048] The storage device 20 is a circuit that stores data and the like required for processing in the distance measuring device 1. The storage device 20 may store, for example, information related to a first signal currently or previously transmitted by the transmitting unit 10, or information related to a second signal previously received by the receiving unit 12. Furthermore, if at least one of the operations of the distance measuring device 1 is software-based information processing that is specifically realized using hardware resources, the storage device 20 may store executable files, programs, or the like related to this software.

[0049] When the determination circuit 16 determines that the second signal is the first signal, which is a single-path reflection, the measurement circuit 14 estimates and outputs the distance to the object from which the first signal is reflected, using the comparison result obtained by combining the first and second signals, etc. The measurement circuit 14 estimates the distance using equation (3) or an equation that takes into account the Doppler effect, etc.

[0050] 3. Flow of Distance Measuring Process FIG. 8 is a flowchart showing the process of the distance measuring device 1 according to an embodiment.

[0051] The transmitter 10 transmits a first signal, which is a chirp signal (S100). Note that this first signal may be a signal controlled by predetermined initial parameters.

[0052] The receiving unit 12 receives a second signal, which is a signal from the outside (S102).

[0053] The determination circuit 16 compares the first signal transmitted by the transmitter 10 with the second signal received by the receiver 12, and makes a determination about these two signals based on the comparison result (S104). The determination circuit 16 detects that the second signal has a different frequency modulation from the first signal, for example, by the process shown below, and determines that the second signal is a signal transmitted from a different slimming source from the first signal.

[0054] 9 is a flowchart showing the signal comparison and judgment process. The judgment circuit 16 compares signals according to the process of this flowchart to judge whether they are reflected waves and / or whether they are on a single-path route.

[0055] The determination circuit 16 determines whether the second signal is a reflected wave of the first signal based on the determination results for multiple parameters, and a threshold value may be set for each of these determinations to reduce the influence of the Doppler effect, noise, etc.

[0056] The decision circuit 16 acquires information on the time t1 when the first signal is transmitted from the transmitter 10 and the time t2 when the receiver 12 receives the second signal (S200).

[0057] The determination circuit 16 determines whether the time difference t2 - t1 is equal to or less than a time threshold value (S202). If this time difference is greater than the threshold value (S202: NO), the determination circuit 16 determines that the second signal is not a signal related to a reflected wave of the first signal (S218).

[0058] If t2 is earlier than t1, the determination circuit 16 may not perform ranging using the second signal in the first place, and may therefore exclude the second signal from the rangefinding target. As another example, in this case, the second signal may not be included in the ranging target, and the operation may immediately proceed to change the parameters of a new first signal.

[0059] In addition, a threshold value is set that can also handle the case where the first signal is reflected as the second signal due to multipath.

[0060] The determination circuit 16 may use, for example, multiple thresholds in the determination of S202. The multiple thresholds may be a threshold within the range of a single path and a threshold acceptable for a multipath. If the arrival time is outside the range of a single path but within the range of a multipath, the determination circuit 16 may perform the following determination without determining whether or not it is a reflected wave in the determination of S202.

[0061] That is, if the second signal is not received within a predetermined time after the first signal is transmitted and has frequency modulation that can be considered identical to that of the first signal, the determination circuit 16 can also determine that the first signal is a signal related to a reflected wave that has been reflected by multipath outside.

[0062] If S202: YES, the determination circuit 16 acquires the period Tc2 of the second signal (S204). The determination circuit 16 may acquire the period Tc1 of the first signal based on the signal input from the transmitter 10, or may acquire the period Tc1 based on information on the period used by the signal generation circuit 18 to generate the first signal.

[0063] The determination circuit 16 calculates the difference |Tc2 - Tc2| between the period Tc1 of the first signal and the period Tc2 of the second signal, and determines whether this difference is equal to or smaller than a period threshold value (S206). If this period difference is greater than the threshold value (S206: NO), the determination circuit 16 determines that the second signal is not a signal related to a reflected wave of the first signal (S218).

[0064] If S206: YES, the determination circuit 16 acquires the initial frequency fc2 of the second signal (S208). The determination circuit 16 may acquire the initial frequency fc1 of the first signal based on the signal input from the transmitting unit 10, or may acquire the initial frequency fc1 based on information about the initial frequency used by the signal generating circuit 18 to generate the first signal.

[0065] The determination circuit 16 calculates the difference |fc2 - fc1| between the initial frequency fc1 of the first signal and the initial frequency fc2 of the second signal, and determines whether this difference is equal to or smaller than an initial frequency threshold (S210). If this difference in initial frequency is greater than the threshold (S210: NO), the determination circuit 16 determines that the second signal is not a signal related to a reflected wave of the first signal (S218).

[0066] If the answer is YES in S210, the determination circuit 16 acquires the slope (gradient) s2 of the frequency change of the second signal (the slope of the line segment in FIG. 5, etc.) (S212). The determination circuit 16 may, for example, acquire the difference (bandwidth) B2 between the initial frequency and the final frequency of the received second signal, and calculate the slope s2 (= B2 / Tc2) from this bandwidth B2 and the period Tc2 acquired in S204. The determination circuit 16 similarly acquires the slope s1 of the frequency change of the first signal. The determination circuit 16 may acquire parameters necessary to calculate the slope s1 of the first signal based on the signal input from the transmitter 10, or may acquire them based on information used by the signal generation circuit 18 to generate the first signal.

[0067] The determination circuit 16 calculates the ratio s2 / s1 of the slope s1 of the frequency change of the first signal to the slope s2 of the frequency change of the second signal, and determines whether this ratio is within a range indicated by a slope threshold (S214). If this slope ratio is outside the range indicated by the threshold (S214: NO), the determination circuit 16 determines that the second signal is not a signal related to a reflected wave of the first signal (S218). Furthermore, without being limited to this, the determination circuit 16 may use a statistic other than the ratio to detect whether the range of the slope of the second signal is within a predetermined range from the range of the slope of the first signal, and determine whether or not it is a reflected wave.

[0068] If the final determination in S214 is YES, the determination circuit 16 determines that the second signal is a reflected wave of the first signal (S216).

[0069] Furthermore, acquisition of other information is not excluded. For example, the determination circuit 16 may acquire information on the final frequency in a cycle as a frequency characteristic, or, if the chirp signal is a signal that increases and decreases linearly, information on the minimum and maximum frequencies. As a result, the determination circuit 16 can acquire and compare information on the frequency bandwidth and frequency band. As an example, the determination circuit 16 can determine that the first signal and the second signal are not signals related to reflected waves if their frequency bands partially overlap but do not overlap beyond a threshold range.

[0070] 9 shows an example of a processing flow, and the processing flow is not limited to this. For example, the determination circuit 16 can omit some of the determination steps shown in FIG. 9. That is, the determination circuit 16 may determine whether the second signal is a reflected wave of the first signal by arbitrarily combining the determination processes shown in the flowchart. Furthermore, the determination circuit 16 does not need to make the determination in the order shown in the flowchart, and can arbitrarily change the order of the determination as long as no contradictions occur.

[0071] The determination circuit 16 may also be composed of multiple circuits, each of which may perform a corresponding determination. In this way, the determination circuit 16 can realize any determination process by appropriately combining any circuit configuration. This combination can be appropriately selected depending on the processing time, circuit configuration, execution environment, etc.

[0072] The thresholds used in each determination may be determined based on the relative speed difference between the object and the target. The determination circuit 16 may set thresholds that take into account the influence of the Doppler effect on the transmitted signal and the reflected signal when the relative speed difference is a predetermined speed, for example, when the object approaches at a speed of 100 km / h. These thresholds may be set in advance. As another example, when the ranging device 1 is mounted on a moving object, these thresholds may change depending on the speed of the moving object.

[0073] However, the threshold value is not limited to this, and can be set appropriately based on the usage environment, etc.

[0074] <3-2. Signal Parameter Change Processing> Returning to FIG. 8 , the distance measuring device 1 branches its processing based on the result of the determination by the determination circuit 16 of whether or not the second signal is a reflected wave of the first signal (S106). If the second signal is determined to be a reflected wave of the first signal (S106: YES), the measurement circuit 14 generates a composite wave of the first and second signals, compares the first and second signals, and measures the distance to the object from which the first signal was reflected based on the beat frequency (S108). The measurement circuit 14 can output the measurement results as desired. Alternatively, the signal generation circuit 18 can control the generation of the current first signal (S112), and the distance measuring device 1 may continue measuring the distance using the same first signal.

[0075] If it is determined that the second signal is not a reflected wave of the first signal (S106: NO), the signal generation circuit 18 changes the parameters of the first signal to make it a different signal (S110). For example, the signal generation circuit 18 can change the first signal so that the modulation state of the first signal is different from that of the received second signal. The signal generation circuit 18 may perform the following processing by obtaining parameters related to the frequency characteristics of the second signal from the determination circuit 16.

[0076] <3-2(1). Process for Changing Initial Frequency Values> Fig. 10 is a diagram schematically illustrating an example of a change in signal parameters according to an embodiment. The dashed line indicates the state of the first signal before the change, and the solid line indicates the state of the first signal after the change. This also applies to the following diagrams. Note that although the frequency characteristic bands do not overlap in the diagram, there may be some overlapping ranges.

[0077] The signal generating circuit 18 can change the initial frequency (initial value of the frequency) from fc to fc'. By changing the initial frequency, it is possible to use a chirp signal in a frequency band different from that of the second signal.

[0078] The signal generation circuit 18 can set fc' by, for example, adding or subtracting a random value to fc or multiplying fc by a random value, and change the new first signal to a chirp signal in a different frequency band from the current first signal.

[0079] The signal generating circuit 18 can also change the initial frequency to change the frequency band of the first signal so that at least a portion of the frequency band is different from the frequency band of the received second signal.

[0080] By controlling in this way, the first signal can be controlled so that signals transmitted from other devices do not interfere with the first signal and cause swells.

[0081] In either case, changing the initial frequency may change the measurement performance, especially the resolution. Therefore, the signal generating circuit 18 can determine a random number within a threshold value that does not cause a significant change in the measurement performance, and change the initial value as described above.

[0082] When the measurement circuit 14 receives information about the initial frequency fc' from the signal generation circuit 18, it measures the distance based on the following equation: Δf' denotes the beat frequency after changing the initial frequency.

[0083] 3-2(2). Signal Period Change Processing> FIG. 11 is a diagram illustrating an example of changing a signal parameter according to an embodiment. The signal generation circuit 18 may change the time at which the signal is emitted, i.e., the signal period. By changing the signal period Tc to Tc', the signal generation circuit 18 can use a chirp signal with a signal period different from that of the second signal.

[0084] When changing the period, the signal generating circuit 18 can change the period using a random number, just as in the case of the initial frequency. Note that changing the frequency gradient over time is essentially a similar process.

[0085] By controlling in this manner, even if interference occurs between the first signal and a signal transmitted from another device, the probability of the first signal having a predetermined beat frequency over a period is reduced, taking into account the influence of the Doppler effect, unlike a reflected wave.

[0086] In this case, there is also a possibility that measurement performance such as resolution may change, but the signal generating circuit 18 can determine random numbers within a range that does not significantly affect these.

[0087] When the measurement circuit 14 acquires the information on the period Tc' from the signal generation circuit 18, it measures the distance based on the following equation.

[0088] 3-2(3). Bandwidth Modification Process: FIG. 12 is a diagram illustrating an example of a signal parameter modification according to an embodiment. The signal generation circuit 18 may modify the signal bandwidth, i.e., the difference between the minimum and maximum frequencies. By modifying the signal bandwidth B to B', the signal generation circuit 18 can use a chirp signal with a different bandwidth from the second signal.

[0089] When changing the bandwidth, the signal generating circuit 18 can change the bandwidth using a random number, just as in the case of the initial frequency. As in the case above, there is a possibility that the measurement performance will change, but the signal generating circuit 18 can change the bandwidth within a range where the impact of this change is small.

[0090] By controlling in this manner, even if interference occurs between the first signal and a signal transmitted from another device, the probability of the first signal having a predetermined beat frequency over a period is reduced, taking into account the influence of the Doppler effect, unlike a reflected wave.

[0091] The signal generating circuit 18 can use a combination of at least two of the above-mentioned initial frequency changes, period changes, and bandwidth changes. However, since simultaneous changes in period and bandwidth may result in frequency characteristics with the same slope, care should be taken to avoid changes at the same magnification.

[0092] 8, the signal generating circuit 18 generates a first signal using the unchanged parameters (S108) or the changed parameters (S110) and transmits the first signal from the transmitting unit 10 to the outside (S100). By repeating this process, the distance measuring device 1 can continue measuring distances using a first signal that does not interfere with other devices.

[0093] The distance measuring device 1 may perform general processing not described above while continuing distance measurement. For example, the distance measuring device 1 may further perform object position detection based on the distance measurement result, or may check continuity between frames. The distance measuring device 1 may also detect object movement.

[0094] <3-3. Other Processing> The determination circuit 16 or the signal generation circuit 18 may store, for a predetermined time, the value of a parameter indicating the frequency characteristic of the second signal in the storage device 20. The signal generation circuit 18 can refer to the parameter stored in the storage device 20 and perform control so as not to generate a first signal equivalent to a signal based on this parameter.

[0095] For example, when a second signal that is not a reflected wave of the first signal is received, the signal generating circuit 18 can control the frequency band of at least the first signal so that the frequency band of at least a part of the first signal is different from the frequency band of the second signal for a predetermined period of time.

[0096] Furthermore, the signal generating circuit 18 can switch to transmitting a first signal with the above-described characteristics even before the transmission of the first signal is completed, i.e., even during the transmission cycle of the first signal. This process may be performed when it is determined that the signal is not a reflected wave in any of the determinations shown in FIG. 9. By operating in this manner, it is possible to quickly suppress interference between the first signal and signals transmitted from other devices, and the distance measuring device 1 can, for example, suppress erroneous detection of an object.

[0097] Even if the signal generating circuit 18 determines that the second signal is not a reflected wave, it does not need to change the parameters of the first signal if it determines that the second signal has parameters that are sufficiently different from those of the first signal based on frequency, period, etc., i.e., that the combination of the first and second signals does not generate a swell that is sufficiently observable. This is because the distance measuring device 1 can currently sufficiently separate the first signal from the second signal transmitted from another device.

[0098] That is, the parameters of the first signal transmitted from the transmitter 10 can be changed even during transmission by the transmitter 10 or reception by the receiver 12, and conversely, there is no need to interrupt the operations of the transmitter 10 and the receiver 12 even during determination by the determination circuit 16. The same applies to the signal generation circuit 18.

[0099] 4. Summary As described above, according to the present embodiment, it is possible to efficiently suppress interference between the transmitted first signal and signals transmitted from other devices by changing the characteristics of the first signal. As a result, it is possible to suppress interference between devices, achieve more accurate distance measurement, and further realize operations such as object detection.

[0100] Each component of the distance measuring device 1 may be formed including a semiconductor circuit. The transmitter 10 and receiver 12 may be formed on the same substrate, or on different substrates. Also, at least a part of each component of the distance measuring device 1 may be formed on stacked semiconductor substrates. The position of each component on the stacked substrates is arbitrary.

[0101] 5. Application Examples The technology according to the present disclosure can be applied to various products. For example, the technology according to the present disclosure may be implemented as a device mounted on any type of mobile object, such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, personal mobility, an airplane, a drone, a ship, a robot, construction machinery, or agricultural machinery (tractor). Furthermore, these mobile objects may be controlled by a manned driver or may be unmanned.

[0102] 13 is a block diagram showing a schematic configuration example of a vehicle control system 7000, which is an example of a mobile object control system to which the technology according to the present disclosure can be applied. The vehicle control system 7000 includes multiple electronic control units connected via a communication network 7010. In the example shown in FIG. 13, the vehicle control system 7000 includes a drive system control unit 7100, a body system control unit 7200, a battery control unit 7300, an outside-vehicle information detection unit 7400, an inside-vehicle information detection unit 7500, and an integrated control unit 7600. The communication network 7010 connecting these multiple control units may be an in-vehicle communication network conforming to any standard, such as a Controller Area Network (CAN), a Local Interconnect Network (LIN), a Local Area Network (LAN), or FlexRay (registered trademark).

[0103] Each control unit includes a microcomputer that performs arithmetic processing according to various programs, a memory unit that stores the programs executed by the microcomputer or parameters used in various calculations, and a drive circuit that drives various controlled devices. Each control unit includes a network I / F for communicating with other control units via a communication network 7010, and a communication I / F for communicating with devices or sensors inside and outside the vehicle via wired or wireless communication. Figure 13 illustrates the functional configuration of the integrated control unit 7600, including a microcomputer 7610, a general-purpose communication I / F 7620, a dedicated communication I / F 7630, a positioning unit 7640, a beacon receiving unit 7650, an in-vehicle device I / F 7660, an audio / video output unit 7670, an in-vehicle network I / F 7680, and a memory unit 7690. Similarly, the other control units also include a microcomputer, a communication I / F, a memory unit, and the like.

[0104] The drivetrain control unit 7100 controls the operation of devices related to the drivetrain of the vehicle according to various programs. For example, the drivetrain control unit 7100 functions as a control device for a driving force generating device for generating driving force for the vehicle, such as an internal combustion engine or a drive motor, a driving force transmission mechanism for transmitting driving force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, and a braking device for generating braking force for the vehicle. The drivetrain control unit 7100 may also function as a control device for an ABS (Antilock Brake System) or ESC (Electronic Stability Control), etc.

[0105] A vehicle state detection unit 7110 is connected to the drivetrain control unit 7100. The vehicle state detection unit 7110 includes at least one of a gyro sensor that detects the angular velocity of the axial rotational motion of the vehicle body, an acceleration sensor that detects the acceleration of the vehicle, or a sensor that detects the amount of operation of the accelerator pedal, the amount of operation of the brake pedal, the steering angle of the steering wheel, the engine rotation speed, the wheel rotation speed, etc. The drivetrain control unit 7100 performs arithmetic processing using signals input from the vehicle state detection unit 7110, and controls the internal combustion engine, the drive motor, the electric power steering device, the brake device, etc.

[0106] The body system control unit 7200 controls the operation of various devices equipped in the vehicle body according to various programs. For example, the body system control unit 7200 functions as a control device for a keyless entry system, a smart key system, a power window device, or various lamps such as head lamps, backup lamps, brake lamps, turn signals, and fog lamps. In this case, radio waves transmitted from a portable device that serves as a key or signals from various switches can be input to the body system control unit 7200. The body system control unit 7200 receives these radio waves or signals and controls the vehicle's door lock device, power window device, lamps, etc.

[0107] The battery control unit 7300 controls the secondary battery 7310, which is the power supply source for the drive motor, in accordance with various programs. For example, information such as battery temperature, battery output voltage, or remaining battery capacity is input to the battery control unit 7300 from a battery device equipped with the secondary battery 7310. The battery control unit 7300 performs arithmetic processing using these signals, and controls the temperature regulation of the secondary battery 7310 or a cooling device or the like equipped in the battery device.

[0108] The outside vehicle information detection unit 7400 detects information outside the vehicle equipped with the vehicle control system 7000. For example, at least one of an imaging unit 7410 and an outside vehicle information detection unit 7420 is connected to the outside vehicle information detection unit 7400. The imaging unit 7410 includes at least one of a ToF (Time Of Flight) camera, a stereo camera, a monocular camera, an infrared camera, and other cameras. The outside vehicle information detection unit 7420 includes at least one of an environmental sensor for detecting the current weather or climate, or a surrounding information detection sensor for detecting other vehicles, obstacles, pedestrians, etc. around the vehicle equipped with the vehicle control system 7000.

[0109] The environmental sensor may be, for example, at least one of a raindrop sensor that detects rain, a fog sensor that detects fog, a sunshine sensor that detects the level of sunshine, and a snow sensor that detects snowfall. The surrounding information detection sensor may be at least one of an ultrasonic sensor, a radar device, and a LIDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging) device. The imaging unit 7410 and the outside vehicle information detection unit 7420 may each be provided as an independent sensor or device, or may be provided as a device in which multiple sensors or devices are integrated.

[0110] 14 shows an example of the installation positions of the imaging unit 7410 and the vehicle exterior information detection unit 7420. The imaging units 7910, 7912, 7914, 7916, and 7918 are installed, for example, at least one of the front nose, side mirrors, rear bumper, back door, and the upper part of the windshield inside the vehicle cabin of the vehicle 7900. The imaging unit 7910 installed on the front nose and the imaging unit 7918 installed on the upper part of the windshield inside the vehicle cabin mainly acquire images of the front of the vehicle 7900. The imaging units 7912 and 7914 installed on the side mirrors mainly acquire images of the sides of the vehicle 7900. The imaging unit 7916 installed on the rear bumper or back door mainly acquires images of the rear of the vehicle 7900. The imaging unit 7918 provided on the top of the windshield inside the vehicle is primarily used to detect preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, lane marks, etc.

[0111] 14 shows an example of the imaging ranges of the imaging units 7910, 7912, 7914, and 7916. Imaging range a indicates the imaging range of the imaging unit 7910 provided on the front nose, imaging ranges b and c indicate the imaging ranges of the imaging units 7912 and 7914 provided on the side mirrors, respectively, and imaging range d indicates the imaging range of the imaging unit 7916 provided on the rear bumper or back door. For example, by overlaying the image data captured by the imaging units 7910, 7912, 7914, and 7916, a bird's-eye view image of the vehicle 7900 viewed from above can be obtained.

[0112] The outside vehicle information detection units 7920, 7922, 7924, 7926, 7928, 7930 provided on the front, rear, sides, corners, and above the windshield inside the vehicle cabin of the vehicle 7900 may be, for example, ultrasonic sensors or radar devices. The outside vehicle information detection units 7920, 7926, 7930 provided on the front nose, rear bumper, back door, and above the windshield inside the vehicle cabin of the vehicle 7900 may be, for example, LIDAR devices. These outside vehicle information detection units 7920 to 7930 are mainly used to detect preceding vehicles, pedestrians, obstacles, etc.

[0113] Returning to FIG. 13 , the explanation continues. The outside-vehicle information detection unit 7400 causes the imaging unit 7410 to capture an image outside the vehicle and receives image data of the captured image. The outside-vehicle information detection unit 7400 also receives detection information from the connected outside-vehicle information detection unit 7420. If the outside-vehicle information detection unit 7420 is an ultrasonic sensor, a radar device, or a LIDAR device, the outside-vehicle information detection unit 7400 emits ultrasonic waves or electromagnetic waves and receives information on the received reflected waves. The outside-vehicle information detection unit 7400 may perform object detection processing or distance detection processing for people, vehicles, obstacles, signs, or text on the road surface, etc., based on the received information. The outside-vehicle information detection unit 7400 may also perform environment recognition processing to recognize rainfall, fog, road conditions, etc., based on the received information. The outside-vehicle information detection unit 7400 may also calculate the distance to an object outside the vehicle based on the received information.

[0114] The outside vehicle information detection unit 7400 may also perform image recognition processing or distance detection processing to recognize people, vehicles, obstacles, signs, characters on the road, etc. based on the received image data. The outside vehicle information detection unit 7400 may perform processing such as distortion correction or alignment on the received image data, and may also generate an overhead image or a panoramic image by combining image data captured by different imaging units 7410. The outside vehicle information detection unit 7400 may also perform viewpoint conversion processing using image data captured by different imaging units 7410.

[0115] The interior information detection unit 7500 detects information inside the vehicle. The interior information detection unit 7500 is connected to, for example, a driver state detection unit 7510 that detects the state of the driver. The driver state detection unit 7510 may include a camera that captures an image of the driver, a biosensor that detects the driver's biometric information, or a microphone that collects sound inside the vehicle. The biosensor may be provided, for example, on the seat or steering wheel, and detect biometric information of a passenger sitting in the seat or the driver gripping the steering wheel. The interior information detection unit 7500 may calculate the driver's level of fatigue or concentration, or may determine whether the driver is dozing, based on the detection information input from the driver state detection unit 7510. The interior information detection unit 7500 may perform processing such as noise canceling on the collected audio signal.

[0116] The integrated control unit 7600 controls the overall operation of the vehicle control system 7000 in accordance with various programs. An input unit 7800 is connected to the integrated control unit 7600. The input unit 7800 is realized by a device that can be operated by a passenger, such as a touch panel, a button, a microphone, a switch, or a lever. Data obtained by voice recognition of voice input through a microphone may be input to the integrated control unit 7600. The input unit 7800 may be, for example, a remote control device using infrared or other radio waves, or an externally connected device such as a mobile phone or PDA (Personal Digital Assistant) that is compatible with the operation of the vehicle control system 7000. The input unit 7800 may be, for example, a camera, in which case the passenger can input information using gestures. Alternatively, data obtained by detecting the movement of a wearable device worn by the passenger may be input. Furthermore, the input unit 7800 may include, for example, an input control circuit that generates an input signal based on information input by a passenger or the like using the input unit 7800 and outputs the signal to the integrated control unit 7600. The passenger or the like operates the input unit 7800 to input various data to the vehicle control system 7000 and to instruct processing operations.

[0117] The storage unit 7690 may include a ROM (Read Only Memory) that stores various programs executed by the microcomputer, and a RAM (Random Access Memory) that stores various parameters, calculation results, sensor values, etc. The storage unit 7690 may also be realized by a magnetic storage device such as an HDD (Hard Disc Drive), a semiconductor storage device, an optical storage device, a magneto-optical storage device, or the like.

[0118] The general-purpose communication I / F 7620 is a general-purpose communication I / F that mediates communication with various devices present in the external environment 7750. The general-purpose communication I / F 7620 may implement a cellular communication protocol such as GSM (Global System of Mobile communications), WiMAX (registered trademark), LTE (Long Term Evolution), or LTE-Advanced (LTE-A), or other wireless communication protocols such as wireless LAN (also known as Wi-Fi (registered trademark)) or Bluetooth (registered trademark). The general-purpose communication I / F 7620 may connect to devices (e.g., application servers or control servers) present on an external network (e.g., the Internet, a cloud network, or an operator-specific network) via, for example, a base station or an access point. The general-purpose communication I / F 7620 may also connect to a terminal located near the vehicle (e.g., a terminal of a driver, pedestrian, or store, or an MTC (Machine Type Communication) terminal) using, for example, P2P (Peer To Peer) technology.

[0119] The dedicated communication I / F 7630 is a communication I / F that supports a communication protocol designed for use in vehicles. The dedicated communication I / F 7630 may implement a standard protocol such as WAVE (Wireless Access in Vehicle Environment), which is a combination of a lower layer IEEE802.11p and an upper layer IEEE13609, a dedicated short range communications (DSRC), or a cellular communication protocol. The dedicated communication I / F 7630 typically performs V2X communication, which is a concept including one or more of vehicle-to-vehicle communication, vehicle-to-infrastructure communication, vehicle-to-home communication, and vehicle-to-pedestrian communication.

[0120] The positioning unit 7640 performs positioning by receiving, for example, GNSS signals from GNSS (Global Navigation Satellite System) satellites (for example, GPS signals from GPS (Global Positioning System) satellites) and generates position information including the latitude, longitude, and altitude of the vehicle. Note that the positioning unit 7640 may identify the current position by exchanging signals with a wireless access point, or may obtain position information from a terminal such as a mobile phone, PHS, or smartphone that has a positioning function.

[0121] The beacon receiving unit 7650 receives, for example, radio waves or electromagnetic waves transmitted from radio stations or the like installed on the road, and acquires information such as the current location, congestion, road closures, required travel time, etc. The function of the beacon receiving unit 7650 may be included in the dedicated communication I / F 7630 described above.

[0122] The in-vehicle device I / F 7660 is a communication interface that mediates connections between the microcomputer 7610 and various in-vehicle devices 7760 present in the vehicle. The in-vehicle device I / F 7660 may establish wireless connections using wireless communication protocols such as wireless LAN, Bluetooth (registered trademark), NFC (Near Field Communication), or WUSB (Wireless USB). The in-vehicle device I / F 7660 may also establish a wired connection such as USB (Universal Serial Bus), HDMI (High-Definition Multimedia Interface), or MHL (Mobile High-Definition Link) via a connection terminal (and a cable, if necessary) not shown. The in-vehicle device 7760 may include, for example, at least one of a mobile device or a wearable device owned by a passenger, or an information device carried into or attached to a vehicle. The in-vehicle device 7760 may also include a navigation device that searches for a route to an arbitrary destination. The in-vehicle device I / F 7660 exchanges control signals or data signals with these in-vehicle devices 7760.

[0123] The in-vehicle network I / F 7680 is an interface that mediates communication between the microcomputer 7610 and the communication network 7010. The in-vehicle network I / F 7680 transmits and receives signals in accordance with a predetermined protocol supported by the communication network 7010.

[0124] The microcomputer 7610 of the integrated control unit 7600 controls the vehicle control system 7000 in accordance with various programs based on information acquired via at least one of the general-purpose communication I / F 7620, the dedicated communication I / F 7630, the positioning unit 7640, the beacon receiving unit 7650, the in-vehicle device I / F 7660, and the in-vehicle network I / F 7680. For example, the microcomputer 7610 may calculate control target values ​​for the driving force generating device, the steering mechanism, or the braking device based on acquired information inside and outside the vehicle, and output control commands to the drivetrain control unit 7100. For example, the microcomputer 7610 may perform cooperative control aimed at realizing functions of an Advanced Driver Assistance System (ADAS), including vehicle collision avoidance or impact mitigation, following driving based on the following distance, vehicle speed maintenance driving, vehicle collision warning, vehicle lane departure warning, etc. In addition, the microcomputer 7610 may perform cooperative control for the purpose of autonomous driving, which allows the vehicle to travel autonomously without relying on driver operation, by controlling a driving force generating device, steering mechanism, braking device, etc. based on information acquired about the vehicle's surroundings.

[0125] The microcomputer 7610 may generate three-dimensional distance information between the vehicle and objects such as surrounding structures and people, and create local map information including information about the vicinity of the vehicle's current location, based on information acquired via at least one of the general-purpose communication I / F 7620, the dedicated communication I / F 7630, the positioning unit 7640, the beacon receiving unit 7650, the in-vehicle device I / F 7660, and the in-vehicle network I / F 7680. The microcomputer 7610 may also predict dangers, such as a vehicle collision, the approach of a pedestrian, or entry into a closed road, based on the acquired information, and generate a warning signal. The warning signal may be, for example, a signal for generating a warning sound or turning on a warning lamp.

[0126] The audio / video output unit 7670 transmits at least one of audio and image output signals to an output device capable of visually or audibly notifying the vehicle occupants or the outside of the vehicle of information. In the example of FIG. 13 , an audio speaker 7710, a display unit 7720, and an instrument panel 7730 are illustrated as output devices. The display unit 7720 may include, for example, at least one of an on-board display and a head-up display. The display unit 7720 may have an AR (Augmented Reality) display function. The output device may be other devices besides these, such as headphones, a wearable device such as an eyeglass-type display worn by the occupant, a projector, or a lamp. When the output device is a display device, the display device visually displays results obtained by various processes performed by the microcomputer 7610 or information received from other control units in various formats, such as text, images, tables, and graphs. Furthermore, when the output device is an audio output device, the audio output device converts an audio signal consisting of reproduced voice data or acoustic data into an analog signal and outputs it audibly.

[0127] In the example shown in FIG. 13 , at least two control units connected via the communication network 7010 may be integrated into a single control unit. Alternatively, each control unit may be composed of multiple control units. Furthermore, the vehicle control system 7000 may include another control unit not shown. In addition, in the above description, some or all of the functions performed by one control unit may be performed by another control unit. In other words, as long as information is transmitted and received via the communication network 7010, predetermined arithmetic processing may be performed by one of the control units. Similarly, a sensor or device connected to one control unit may be connected to another control unit, and multiple control units may transmit and receive detection information to each other via the communication network 7010.

[0128] A computer program for realizing each function of the distance measuring device 1 according to this embodiment described with reference to FIGS. 1 to 12 can be implemented in any control unit or the like. A computer-readable recording medium storing such a computer program can also be provided. Examples of the recording medium include a magnetic disk, an optical disk, a magneto-optical disk, and a flash memory. The computer program may also be distributed, for example, via a network without using a recording medium.

[0129] In the vehicle control system 7000 described above, at least some of the functions of the distance measuring device 1 according to this embodiment described using Figures 1 to 12 can be applied to the external vehicle information detection unit 7400, the integrated control unit 7600, or other configurations of the application example shown in Figure 13.

[0130] The above-described embodiment may be modified as follows.

[0131] (1) A distance measuring device comprising: a transmitting unit that transmits a first signal, which is a chirp signal, to the outside; a receiving unit that receives a second signal from the outside; a determining circuit that determines whether the second signal is a signal related to a reflected wave of the first signal based on a comparison result between the first signal and the second signal; a signal generating circuit that, when it is determined that the second signal is not a signal related to a reflected wave of the first signal, changes the characteristics of the first signal output from the transmitting unit and outputs the changed signal; and a measuring circuit that, when it is determined that the second signal is a signal related to a reflected wave of the first signal reflected in a single path, estimates and outputs the position of an external object from the beat frequency between the first signal and the second signal.

[0132] (2) The distance measuring device described in (1), wherein the determination circuit determines that the second signal is a signal related to a reflected wave of the first signal reflected externally in a single path, a signal related to a reflected wave of the first signal reflected externally in multiple paths, or a signal transmitted from a transmission source different from that of the first signal.

[0133] (3) The distance measuring device described in (2), wherein the determination circuit determines that the second signal is a signal transmitted from a different transmission source than the first signal when the second signal has a different frequency modulation than the first signal.

[0134] (4) The distance measuring device described in (3), wherein the determination circuit determines that the second signal is a signal transmitted from a different transmission source than the first signal when the second signal has a frequency in a different frequency band than the first signal.

[0135] (5) A distance measuring device according to (3) or (4), wherein the determination circuit determines that the second signal is a signal transmitted from a different transmission source than the first signal when the second signal has a period different from the period of the first signal.

[0136] (6) A ranging device according to any one of (3) to (5), wherein the determination circuit determines that the second signal is a signal transmitted from a different transmission source than the first signal when the second signal has a frequency modulation gradient different from the frequency modulation gradient in the first signal.

[0137] (7) A distance measuring device according to any one of (3) to (6), wherein the judgment circuit determines that the second signal is a signal relating to a reflected wave reflected from outside, if the deviation of the second signal from the parameter is equal to or less than the threshold value, by setting a threshold value for the parameter of the frequency modulation of the first signal.

[0138] (8) A distance measuring device described in any one of (2) to (7), wherein the determination circuit determines that the first signal is a signal related to a reflected wave reflected by multipath outside when the second signal is not received within a predetermined time after the first signal is transmitted and has the same frequency modulation as the first signal.

[0139] (9) A distance measuring device according to any one of (1) to (8), wherein the signal generating circuit changes the initial value of the frequency of the first signal when it is determined that the second signal is not a signal related to a reflected wave of the first signal.

[0140] (10) The distance measuring device according to (9), wherein the signal generating circuit adds or subtracts a random number to or from the initial value of the frequency.

[0141] (11) The distance measuring device according to (9) or (10), wherein the signal generating circuit sets an initial value of the frequency of the first signal so that at least a part of the frequency band is a different frequency band from the frequency band of the second signal.

[0142] (12) The ranging device described in (11), wherein the signal generating circuit sets an initial value of the frequency of the first signal so that at least a portion of the frequency band of the first signal has a frequency different from that of the frequency band of the second signal for a predetermined time after the receiving unit receives the second signal.

[0143] (13) The distance measuring device according to any one of (1) to (12), wherein the signal generating circuit sets the period of the first signal to be different from the period of the second signal.

[0144] (14) A distance measuring device according to any one of (1) to (13), wherein the signal generating circuit changes the characteristics of the first signal if it is determined that the second signal is not a signal related to a reflection of the first signal, even during generation of the first signal.

[0145] (15) A distance measuring method comprising: a transmitting unit that transmits a first signal, which is a chirp signal, to the outside; and a receiving unit that receives a second signal from the outside; a determining circuit that compares the first signal with the second signal and determines whether the second signal is a signal related to a reflected wave of the first signal; a signal generating circuit that, when determining that the second signal is not a signal related to a reflected wave of the first signal, changes the characteristics of the first signal output from the transmitting unit and outputs the first signal; and a measuring circuit that, when determining that the second signal is a signal related to a reflected wave of the first signal reflected in a single path, estimates and outputs the position of an external object from the beat frequency between the first signal and the second signal.

[0146] (16) A program that causes a processing circuit to execute at least a part of the method of (15).

[0147] The aspects of the present disclosure are not limited to the above-described embodiments and include various conceivable modifications, and the effects of the present disclosure are not limited to the above-described contents. The components in each embodiment may be appropriately combined and applied. In other words, various additions, modifications, and partial deletions are possible within the scope of the conceptual idea and intent of the present disclosure, which is derived from the content defined in the claims and their equivalents.

[0148] 1: distance measuring device, 10: transmitter, 12: receiver, 14: measurement circuit, 16: determination circuit, 18: signal generation circuit, 20: memory circuit

Claims

1. A distance measuring device comprising: a transmitting unit which transmits a first signal which is a chirp signal to the outside; a receiving unit which receives a second signal from the outside; a determining circuit which determines whether the second signal is a signal related to a reflected wave of the first signal based on a comparison result between the first signal and the second signal; a signal generating circuit which, if it is determined that the second signal is not a signal related to a reflected wave of the first signal, changes the characteristics of the first signal output from the transmitting unit and outputs the changed signal; and a measuring circuit which, if it is determined that the second signal is a signal related to a reflected wave reflected in a single path of the first signal, estimates and outputs the position of an external object from the beat frequency between the first signal and the second signal.

2. The distance measuring device of claim 1, wherein the determination circuit determines that the second signal is a signal related to a reflected wave of the first signal reflected externally in a single path, a signal related to a reflected wave of the first signal reflected externally in multiple paths, or a signal transmitted from a transmission source different from that of the first signal.

3. The distance measuring device according to claim 2, wherein the determination circuit determines that the second signal is a signal transmitted from a different transmission source than the first signal when the second signal has a different frequency modulation than the first signal.

4. The distance measuring device according to claim 3, wherein the determination circuit determines that the second signal is a signal transmitted from a different transmission source than the first signal when the second signal has a frequency in a different frequency band than the first signal.

5. The distance measuring device according to claim 3, wherein the determination circuit determines that the second signal is a signal transmitted from a transmission source different from that of the first signal when the second signal has a period different from that of the first signal.

6. The distance measuring device of claim 3, wherein the determination circuit determines that the second signal is a signal transmitted from a different transmission source than the first signal when the second signal has a frequency modulation gradient different from the frequency modulation gradient in the first signal.

7. The distance measuring device of claim 3, wherein the judgment circuit sets a threshold value for a parameter of frequency modulation of the first signal, and if the deviation of the second signal from the parameter is equal to or less than the threshold value, judges that the first signal is a signal related to a wave reflected from outside.

8. The distance measuring device of claim 2, wherein the determination circuit determines that the first signal is a signal related to a reflected wave reflected by multiple paths outside when the second signal is not received within a predetermined time after the first signal is transmitted and has the same frequency modulation as the first signal.

9. The distance measuring device according to claim 1, wherein the signal generating circuit changes an initial value of the frequency of the first signal when it is determined that the second signal is not a signal related to a reflected wave of the first signal.

10. The distance measuring device according to claim 9, wherein the signal generating circuit adds or subtracts a random number to the initial value of the frequency.

11. The distance measuring device according to claim 9, wherein the signal generating circuit sets an initial value of the frequency of the first signal so that at least a portion of the frequency band is a different frequency band from the frequency band of the second signal.

12. The ranging device of claim 11, wherein the signal generating circuit sets an initial value of the frequency of the first signal so that the frequency band of at least a portion of the first signal has a different frequency from the frequency band of the second signal for a predetermined time after the receiving unit receives the second signal.

13. The distance measuring device according to claim 1, wherein the signal generating circuit sets the period of the first signal to be different from the period of the second signal.

14. The distance measuring device according to claim 1, wherein the signal generating circuit changes a characteristic of the first signal when it is determined that the second signal is not a signal related to a reflection of the first signal, even during generation of the first signal.

15. A distance measuring method comprising: a transmitting unit that transmits a first signal, which is a chirp signal, to the outside; and a receiving unit that receives a second signal from the outside; a determination circuit that compares the first signal with the second signal and determines whether the second signal is a signal related to a reflected wave of the first signal; a signal generating circuit that, when it determines that the second signal is not a signal related to a reflected wave of the first signal, changes the characteristics of the first signal output from the transmitting unit and outputs the first signal; and a measurement circuit that, when it determines that the second signal is a signal related to a reflected wave of the first signal reflected in a single path, estimates and outputs the position of an external object from the beat frequency between the first signal and the second signal.

Images