Operation detection device and method

Abstract

An operation detection device according to the present disclosure detects an operation of an operation body including at least one static operation. The operation detection device includes: a Lissajous waveform acquisition unit that extracts an in-phase component and an orthogonal-phase component by orthogonal demodulation from reflected radio waves reflected by the operation body, and acquires a Lissajous waveform based on the extracted in-phase component and the orthogonal phase component; and an offset correction unit that, on the basis of coordinates in an IQ orthogonal coordinate system of the plurality of points forming the Lissajous waveform, acquires a first estimated distance in an I-axis direction between the center of the Lissajous waveform and the origin of the IQ orthogonal coordinate system and a second estimated distance in a Q-axis direction between the center of the Lissajous waveform and the origin of the IQ orthogonal coordinate system, and, on the basis of the acquired first and second estimated distances, corrects offset of the Lissajous waveform.

Description

Motion detection device and method

[0001] The present disclosure relates to a motion detection device and method for detecting the motion of a moving object.

[0002] A conventional position detection device detects the position of a swing arm included in a hard disk drive based on a two-phase output signal output from an encoder in response to changes in the position of the swing arm (see, for example, Patent Document 1). This position detection device includes an analog-to-digital conversion unit, a correction unit, and a digital calculation unit. The analog-to-digital conversion unit digitally converts the two-phase output signal from the encoder and outputs a digital signal. The correction unit calculates the center position of the Lissajous waveform using at least three points on the Lissajous waveform generated based on the digital signal, and corrects the offset of the digital signal (deviation of the center position from the origin position) based on the calculated center position and the center position (origin position) of an ideal Lissajous waveform without any offset. The digital calculation unit calculates the position of the swing arm, which is the object to be measured, using the signal corrected by the correction unit.

[0003] Also, a conventional object displacement detection signal processing device is known that is mounted on a vehicle and monitors the movement of vehicle occupants, surrounding people, cars, objects, etc. (See, for example, Patent Document 2). This object displacement detection signal processing device includes one or more antennas, a transmission / reception circuit, and a displacement calculation unit. The transmission / reception circuit transmits a transmission wave from the one or more antennas to an object to be detected and receives a reflected wave from the object from the antenna. The displacement calculation unit divides the reflected wave into two signals and creates a Lissajous locus by plotting the two signals on a Cartesian coordinate system. The displacement calculation unit then rotates and arranges multiple Lissajous loci in a predetermined quadrant of the Cartesian coordinate system, plots the multiple Lissajous loci on a time axis, and calculates a phase change based on parameters obtained by the rotation and plotting the multiple Lissajous loci on a time axis, and converts the phase change into a displacement.

[0004] JP 2009-162673 A JP 2015-190952 A

[0005] The position detection device described in Patent Document 1 acquires a Lissajous waveform based on two-phase output signals from an encoder. Therefore, the Lissajous waveform approximates a smooth circle, and the deviation of the center of the Lissajous waveform from the origin of a Cartesian coordinate system is relatively small. In contrast, reflected waves from a moving object, such as a person or a vehicle, are superimposed on reflected waves from moving parts (non-stationary parts) of the moving object, such as limbs or doors, with components reflected from substantially stationary parts of the moving object, such as Doppler components. Therefore, the Lissajous waveform obtained based on the reflected waves from the moving object is complex, and the offset is so large that the origin of the Cartesian coordinate system often does not fall within the Lissajous waveform. Therefore, even when detecting the movement of a moving object using the technology described in Patent Document 1, it is virtually impossible to move the center of the Lissajous waveform closer to the origin of the Cartesian coordinate system (offset), making it difficult to accurately detect the movement of the moving object due to the offset. Furthermore, the object displacement detection signal processing device described in Patent Document 2 monitors the movement of a moving object such as a person or a vehicle, but Patent Document 2 neither discloses nor suggests a method for offsetting the center of a complex Lissajous waveform to the origin of a Cartesian coordinate system. Meanwhile, in order to reduce the influence of reflected waves from non-moving parts of the moving object, it is conceivable to subject the reflected waves to high-pass filtering. However, if the movement of the moving object includes a stationary movement, the stationary movement of the moving object will not be included in the Lissajous waveform based on the high-pass filtered signal, making it impossible to detect the movement of the moving object, including the stationary movement.

[0006] Therefore, a main object of the present disclosure is to enable accurate detection of the movement of a moving object including at least one stationary movement.

[0007] The motion detection device disclosed herein is a motion detection device that detects the motion of a moving body including at least one stationary motion, and includes: a radio wave transmitting unit that transmits radio waves in a predetermined frequency band toward the moving body; a radio wave receiving unit that receives reflected radio waves reflected by the moving body; a Lissajous waveform acquiring unit that extracts in-phase and quadrature-phase components from the reflected radio waves by quadrature demodulation and acquires a Lissajous waveform based on the extracted in-phase and quadrature-phase components; an offset correction unit that acquires a first estimated distance in the I-axis direction between the center of the Lissajous waveform and the origin of the IQ orthogonal coordinate system based on coordinates in an IQ orthogonal coordinate system of a plurality of points that form the Lissajous waveform, and a second estimated distance in the Q-axis direction between the center of the Lissajous waveform and the origin of the IQ orthogonal coordinate system, and corrects the offset of the Lissajous waveform based on the acquired first and second estimated distances; and a motion information acquiring unit that acquires information indicative of the motion based on the Lissajous waveform corrected by the offset correction unit.

[0008] The motion detection device disclosed herein detects the motion of a moving object, including at least one stationary motion, and includes a radio wave transmitter, a radio wave receiver, a Lissajous waveform acquirer, an offset correction unit, and a motion information acquirer. The radio wave transmitter transmits radio waves in a predetermined frequency band toward the moving object, and the radio wave receiver receives the radio waves reflected by the moving object. The Lissajous waveform acquirer extracts in-phase and quadrature-phase components from the reflected radio waves by quadrature demodulation and acquires a Lissajous waveform based on the extracted in-phase and quadrature-phase components. The offset correction unit acquires a first estimated distance in the I-axis direction between the center of the Lissajous waveform and the origin of the IQ orthogonal coordinate system and a second estimated distance in the Q-axis direction between the center of the Lissajous waveform and the origin of the IQ orthogonal coordinate system based on the coordinates of multiple points forming the Lissajous waveform in an IQ orthogonal coordinate system, and corrects the Lissajous waveform offset based on the acquired first and second estimated distances. The motion information acquirer acquires information indicating the motion of the moving object based on the Lissajous waveform whose offset has been corrected by the offset correction unit. As a result, even if the Lissajous waveform becomes complex due to the superposition of components reflected from substantially non-moving portions (stationary portions) of the moving body on the reflected waves from the moving portions (non-stationary portions) of the moving body, and the origin of the IQ Cartesian coordinate system is no longer included within the range of the Lissajous waveform, it is possible to move the center of the Lissajous waveform based on the reflected radio waves from the moving portions of the moving body closer to the origin of the IQ Cartesian coordinate system.As a result, by acquiring information indicating the motion of the moving body based on the Lissajous waveform offset based on the first and second estimated distances, it is possible to accurately detect the motion of the moving body, including at least one stationary motion.

[0009] The motion detection method disclosed herein is a motion detection method for acquiring the motion of a moving body including at least one stationary motion, which includes transmitting radio waves in a predetermined frequency band toward the moving body, receiving reflected radio waves reflected by the moving body, extracting an in-phase signal and a quadrature-phase signal from the reflected radio waves by quadrature demodulation, acquiring a Lissajous waveform based on the extracted in-phase signal and quadrature-phase signal, and acquiring a first estimated distance in the I-axis direction between the center of the Lissajous waveform and the origin of the IQ orthogonal coordinate system and a second estimated distance in the Q-axis direction between the center of the Lissajous waveform and the origin of the IQ orthogonal coordinate system based on the coordinates in an IQ orthogonal coordinate system of multiple points forming the Lissajous waveform, correcting an offset of the Lissajous waveform based on the first and second estimated distances, and acquiring information indicating the motion based on the corrected Lissajous waveform.

[0010] According to this method, by obtaining information indicating the movement of the moving body based on a Lissajous waveform offset based on the first and second estimated distances, it becomes possible to accurately detect the movement of the moving body, including at least one stationary movement.

[0011] Fig. 1 is an explanatory diagram showing an application example of a motion detection device of the present disclosure; Fig. 2 is a control block diagram showing a motion detection device of the present disclosure; Fig. 3 is a diagram showing a Lissajous waveform acquired by a Lissajous waveform acquisition unit of a motion detection device of the present disclosure; Fig. 4 is a flowchart for explaining processing executed by a motion detection device of the present disclosure; Fig. 5 is a diagram for explaining offset correction processing of a Lissajous waveform by a motion detection device of the present disclosure; Fig. 6 is a diagram for explaining other offset correction processing of a Lissajous waveform by a motion detection device of the present disclosure.

[0012] Next, embodiments of the present disclosure will be described with reference to the drawings.

[0013] FIG. 1 is an explanatory diagram showing an application example of a motion detection device 1 of the present disclosure. As shown in FIG. 1 , the motion detection device 1 is used as a kick sensor mounted on a vehicle V. That is, the motion detection device 1 as a kick sensor detects the approach of a user U to the vehicle V and detects a kicking motion (see the solid and dotted lines in FIG. 1 ) in which the user U approaches the rear bumper Br (a predetermined location) of the vehicle V, stops, and then moves the foot away from the rear bumper Br. That is, the motion detection device 1 detects motions including at least one stationary motion by the user U as a moving object. Then, in the vehicle V, when the motion detection device 1 detects the kicking motion of the user U, a door opening / closing device (not shown) opens the back door (power back door) of the vehicle V.

[0014] 2, the motion detection device 1 includes a transmitting antenna (radio wave transmitting section) 2, a receiving antenna (radio wave receiving section) 3, an analog front end (hereinafter referred to as "AFE") 4, a digital front end (hereinafter referred to as "DFE") 5, and a determination control device 6. The transmitting antenna 2 transmits radio waves in a predetermined frequency band toward a user U as a moving object, and the receiving antenna 3 receives the radio waves reflected off the user U.

[0015] In this embodiment, the radio waves transmitted from the transmitting antenna 2 are included in the frequency band of the ultra wide band wireless communication standard and have a frequency permitted for use in the area in which the vehicle V is used. Note that the motion detection device 1 may include a transmitting / receiving antenna in which the transmitting antenna and the receiving antenna are integrated, instead of the transmitting antenna 2 and the receiving antenna 3 which are separate from each other, or may include multiple transmitting antennas 2 and multiple receiving antennas 3.

[0016] As shown in FIG. 2 , the AFE 4 includes a transmission circuit 40 and a reception circuit 41. The transmission circuit 40 converts the time-series signal pattern indicated in the digital signal from the DFE 5 into the signal pattern of the radio wave transmitted from the transmission antenna 2 (in this embodiment, a Gaussian-modulated sinusoidal RF pulse). The reception circuit 41 extracts an in-phase component (I component) and a quadrature-phase component (Q component) from the reflected radio wave received by the reception antenna 3 by quadrature demodulation, and performs low-pass filtering on the extracted in-phase component and quadrature-phase component to remove the frequency component of the transmitted radio wave, thereby outputting a digital signal for obtaining a Lissajous waveform based on both. In other words, the reception circuit 41 functions as a Lissajous waveform acquisition unit that acquires a Lissajous waveform based on the reflected radio wave from the user U.

[0017] As shown in FIG. 2 , the DFE 5 includes a signal pattern generation unit 50, an offset correction unit 51, and a motion information acquisition unit 55. The signal pattern generation unit 50 outputs a digital signal indicating the above-mentioned time-series signal pattern. The offset correction unit 51 corrects the offset of the Lissajous waveform obtained from the digital signal from the AFE 4. The motion information acquisition unit 55 acquires information necessary to detect the motion of the user U from the Lissajous waveform whose offset has been corrected by the offset correction unit 51.

[0018] The determination control device 6 includes a microcomputer having a CPU, ROM, ROM, etc., none of which are shown. The determination control device 6 determines whether the user U has approached the rear bumper Br of the vehicle V based on information transmitted from the motion information acquisition unit 55 of the DFE 5, and also performs pattern recognition processing based on the information from the motion information acquisition unit 555 to determine whether the motion of the user U is the kick motion described above. When the determination control device 6 determines that the motion of the user U is a kick motion, it instructs the control device (not shown) of the door opening and closing device to open the back door of the vehicle V.

[0019] Here, the transmitted radio wave (transmitted wave) RFout transmitted from the transmitting antenna 2 can be expressed as in the following equation (1). Furthermore, the reflected radio wave (received wave) RFin received by the receiving antenna 3 can be expressed as in the following equation (2). In equations (1) and (2), "A" is a predetermined constant, "k" is a Gaussian function, "ω" is the frequency of the transmitted radio wave, and "t0" is the time when the transmitted radio wave was transmitted. In equation (2), "P" is a predetermined constant, "ω'" is the frequency shift due to the Doppler effect, and "t1" is the time when the reflected radio wave was transmitted. Furthermore, by converting equation (2) to a complex representation using Euler's formula, the following equation (3) is obtained. Then, by mixing a quadrature signal into equation (3) as shown in the following equations (4) and (5) and removing the double frequency, the in-phase component I can be expressed as in the following equation (6), and the quadrature-phase component Q can be expressed as in the following equation (7).

[0020]

[0021] The above equations (6) and (7) are theoretical equations for the in-phase and quadrature-phase components obtained from the radio waves received by the receiving antenna 3. Plotting these in-phase and quadrature-phase components on an IQ orthogonal coordinate system yields a Lissajous waveform that approximates a circle whose center roughly coincides with the origin O of the IQ orthogonal coordinate system. However, the radio waves reflected from the user U (person) as a moving object are superimposed on the reflected waves from moving parts (non-stationary parts) such as the feet, as well as components reflected from substantially stationary parts of the user U (stationary parts), Doppler components, and the like. Therefore, the Lissajous waveform obtained based on the reflected waves from the moving object often has a complex waveform, as shown in FIG. 3 , with a large offset, so that the origin O of the IQ orthogonal coordinate system is not included within the range of the Lissajous waveform. Even if the information necessary to detect the user U's movements is obtained from the Lissajous waveform shown in FIG. 3 , it becomes difficult to accurately detect the user U's kicking movements. Note that stationary movements included in the movements of the user U appear on the Lissajous waveform as stationary points shown in FIG. 3 .

[0022] Based on this, in the DFE 5 of the motion detection device 1, a series of processes as shown in Fig. 4 are executed by the offset correction unit 51 and the motion information acquisition unit 55. As shown in Fig. 4, the offset correction unit 51 of the DFE 5 acquires coordinates (in, qn) in an IQ orthogonal coordinate system of multiple points rs(0), rs(1), ..., rs(n), ..., rs(N) that form the Lissajous waveform for one cycle of the reflected radio wave from the digital signal transmitted by the receiving circuit 41 of the AFE 4, as shown in Fig. 5 (step S100). In this embodiment, the number N of points rs(n) that form the Lissajous waveform acquired in step S100 is, for example, 100 to 1000.

[0023] Next, based on the coordinates (in, qn) of the multiple points rs(i) acquired in step S100, the offset correction unit 51 acquires a first estimated distance di in the I-axis direction between the center of the Lissajous waveform and the origin O of the IQ orthogonal coordinate system, and a second estimated distance dq in the Q-axis direction between the center of the Lissajous waveform and the origin O of the IQ orthogonal coordinate system (step S110). In step S110, the offset correction unit 51 calculates the average value (= (i0 + i1 + , ... , +iN) / N) of the I-axis coordinate in in the IQ orthogonal coordinate system of the multiple points rs(i) as the first estimated distance di. In addition, the offset correction unit 51 calculates the average value (= (q0 + q1 + , ... , +qN) / N) of the Q-axis coordinate qn in the IQ orthogonal coordinate system of the multiple points rs(i) as the second estimated distance dq.

[0024] After acquiring the first and second estimated distances di and dq, the offset correction unit 51 offsets (moves) the Lissajous waveform in the I-axis direction of the IQ orthogonal coordinate system by the first estimated distance di, and offsets it in the Q-axis direction by the second estimated distance dq (step S120). In step S120, the offset correction unit 51 subtracts the first estimated distance di from the I-axis coordinate in of the multiple points rs(0), ..., rs(i), ..., rs(N), and subtracts the second estimated distance dq from the Q-axis coordinate qn of the multiple points rs(0), ..., rs(i), ..., rs(N). As a result, the coordinates (in, qn) of the multiple points rs(0), ..., rs(i), ..., rs(N) are corrected based on the first and second estimated distances di, dq, and the Lissajous waveform obtained from the corrected coordinates (in, qn) includes at least the origin O of the IQ Cartesian coordinate system inside, and is offset so that its center is close to the origin O. In other words, the processing of steps S110-S120 regards the Lissajous waveform based on the reflected radio waves from the moving part (non-stationary part) of the user U (moving body) as being offset by a vector based on the reflected radio waves and Doppler components from the non-moving part of the user U (moving body), and corrects the offset of the Lissajous waveform based on the vector.

[0025] The coordinates (in, qn) of the multiple points rs(0), ..., rs(i), ..., rs(N) corrected by the offset correction unit 51 are transmitted to the operation information acquisition unit 55. The operation information acquisition unit 55 calculates the intensity of the reflected radio wave (=√(I 2 +Q 2 ), the distance to the user U (moving object), and the speed of the moving object (moving part) are acquired (step S130). This temporarily ends the processing of the DFE 5 for one cycle of the reflected radio wave. The information acquired by the motion information acquisition unit 55 is then transmitted to the determination control device 6, which then executes a determination control process based on the information from the motion information acquisition unit 55.

[0026] As described above, the motion detection device 1 detects the motion of a moving object including at least one stationary motion, and includes a transmitting antenna 2 as a radio wave transmitting unit, a receiving antenna 3 as a radio wave receiving unit, a receiving circuit 41 as a Lissajous waveform acquiring unit, an offset correction unit 51, and a motion information acquiring unit 55. The transmitting antenna 2 transmits radio waves in a frequency band (predetermined frequency band) of an ultra-wideband wireless communication standard toward a user U as a moving object, and the receiving antenna 3 receives the radio waves reflected off the user U. The receiving circuit 41 extracts in-phase and quadrature-phase components from the reflected radio waves by quadrature demodulation, and outputs a digital signal for obtaining a Lissajous waveform based on the extracted in-phase and quadrature-phase components. The offset correction unit 51 acquires a first estimated distance di in the I-axis direction between the center of the Lissajous waveform and the origin O of the IQ Cartesian coordinate system and a second estimated distance dq in the Q-axis direction between the center of the Lissajous waveform and the origin O of the IQ Cartesian coordinate system based on the coordinates (in, qn) of multiple points rs(0), ..., rs(i), ..., rs(N) forming the Lissajous waveform (step S110). Furthermore, the offset correction unit 51 corrects the offset of the Lissajous waveform based on the acquired first and second estimated distances di and dq (step S120). Then, the motion information acquisition unit 55 acquires information indicating the motion of the user U based on the Lissajous waveform whose offset has been corrected by the offset correction unit 51 (step S130).

[0027] As a result, even if the Lissajous waveform becomes complex due to components reflected from substantially stationary parts (stationary parts) of the user U being superimposed on waves reflected from moving parts (non-stationary parts) such as the feet of the user U (moving body), and the origin O of the IQ Cartesian coordinate system is no longer included within the range of the Lissajous waveform, it is possible to move the center of the Lissajous waveform based on the reflected radio waves from the moving parts of the user U closer to the origin O of the IQ Cartesian coordinate system. As a result, by acquiring information indicating the motion of the user U (strength, distance, speed, etc.) based on the Lissajous waveform offset based on the first and second estimated distances di and dq, it becomes possible to accurately detect the kicking motion of the user U, including at least one stationary motion.

[0028] In the motion detection device 1, the offset correction unit 51 obtains the average value of the I-axis coordinate in of the multiple points rs(0), ..., rs(i), ..., rs(N) forming the Lissajous waveform in the IQ orthogonal coordinate system as the first estimated distance di, and obtains the average value of the Q-axis coordinate qn of the multiple points rs(0), ..., rs(i), ..., rs(N) in the IQ orthogonal coordinate system as the second estimated distance dq (step S110). Furthermore, the offset correction unit 51 offsets the Lissajous waveform in the I-axis direction by the first estimated distance di and in the Q-axis direction by the second estimated distance dq (step S120). In this way, by using the coordinates (in, qn) in the IQ orthogonal coordinate system of the numerous points rs(0), ..., rs(i), ..., rs(N) that form the Lissajous waveform, it is possible to obtain the first and second estimated distances di, dq more accurately, thereby further improving the detection accuracy of the kicking motion of user U, which includes at least one stationary motion.

[0029] However, in step S110 of Fig. 4, the first and second estimated distances di and dq may be acquired using a procedure such as that shown in Fig. 6. That is, in step S110, the offset correction unit 51 of the DFE 5 may acquire, as the first estimated distance di, the average value (= (Imax + Imin) / 2) of the maximum value Imax and the minimum value Imin in the I-axis direction of the IQ orthogonal coordinate system of the Lissajous waveform, and may acquire, as the second estimated distance dq, the average value (= (Qmax + Qmin) / 2) of the maximum value Qmax and the minimum value Qmin in the Q-axis direction of the IQ orthogonal coordinate system of the Lissajous waveform. This makes it possible to ensure good accuracy in detecting the kicking motion of the user U, including at least one stationary motion, while reducing the load of acquiring the first and second estimated distances di and dq.

[0030] Furthermore, in the motion detection device 1, the transmitting antenna 2 as a radio wave transmitter transmits radio waves in the frequency band of the ultra-wideband wireless communication standard toward the user U as a moving object. This makes it possible to improve the accuracy of detecting the kicking motion of the user U, including at least one stationary motion, while suppressing an increase in the cost of the entire device compared to, for example, a case in which a transmitting antenna and a receiving antenna that transmit or receive radio waves in a high-frequency band are used. However, the transmitting antenna 2 and the receiving antenna 3 may transmit or receive radio waves of a frequency that is not included in the frequency band of the ultra-wideband wireless communication standard.

[0031] Furthermore, the motion detection device 1 detects the approach of the user U to the vehicle V, and also detects a kicking motion in which the user U approaches the rear bumper Br of the vehicle V, stops it temporarily, and then moves their foot away from the rear bumper Br. In other words, the motion detection device 1 is extremely suitable as a kick sensor mounted on the vehicle V. However, the motion detection device 1 may be used for purposes other than a kick sensor, and may also be used in a place other than the vehicle V.

[0032] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present disclosure. Furthermore, the above-described embodiment is merely a specific form of the invention described in the Summary of the Invention, and does not limit the elements of the invention described in the Summary of the Invention.

[0033] The invention of the present disclosure can be used in the motion detection device manufacturing industry, etc.

Claims

1. A motion detection device that detects the motion of a moving object including at least one stationary motion, comprising: a radio wave transmitting unit that transmits radio waves in a predetermined frequency band toward the moving object; a radio wave receiving unit that receives reflected radio waves reflected by the moving object; a Lissajous waveform acquiring unit that extracts in-phase and quadrature-phase components from the reflected radio waves by quadrature demodulation, and acquires a Lissajous waveform based on the extracted in-phase and quadrature-phase components; an offset correction unit that acquires a first estimated distance in the I-axis direction between the center of the Lissajous waveform and the origin of the IQ orthogonal coordinate system, based on the coordinates in an IQ orthogonal coordinate system of a plurality of points that form the Lissajous waveform, and a second estimated distance in the Q-axis direction between the center of the Lissajous waveform and the origin of the IQ orthogonal coordinate system, and corrects the offset of the Lissajous waveform based on the acquired first and second estimated distances; and a motion information acquiring unit that acquires information indicative of the motion based on the Lissajous waveform corrected by the offset correction unit.

2. A motion detection device according to claim 1, wherein the offset correction unit obtains the average value of the I-axis coordinates in the IQ orthogonal coordinate system of the multiple points forming the Lissajous waveform as the first estimated distance, and obtains the average value of the Q-axis coordinates in the IQ orthogonal coordinate system of the multiple points forming the Lissajous waveform as the second estimated distance, and offsets the Lissajous waveform in the I-axis direction by the first estimated distance, and offsets it in the Q-axis direction by the second estimated distance.

3. A motion detection device according to claim 1, wherein the offset correction unit obtains the average value of the maximum and minimum values ​​of the Lissajous waveform in the I-axis direction of the IQ orthogonal coordinate system as the first estimated distance, and obtains the average value of the maximum and minimum values ​​of the Lissajous waveform in the Q-axis direction of the IQ orthogonal coordinate system as the second estimated distance, and offsets the Lissajous waveform in the I-axis direction by the first estimated distance, and offsets it in the Q-axis direction by the second estimated distance.

4. A motion detection device according to any one of claims 1 to 3, wherein the predetermined frequency band is a frequency band of an ultra-wideband wireless communication standard.

5. A motion detection device as claimed in any one of claims 1 to 3, which is mounted on a vehicle and detects a user's approach to the vehicle, as well as a kicking motion in which the user approaches a predetermined location on the vehicle, stops the foot temporarily, and then moves the foot away from the predetermined location.

6. A motion detection method for acquiring the motion of a moving body including at least one stationary motion, comprising: transmitting radio waves in a predetermined frequency band toward the moving body; receiving reflected radio waves reflected by the moving body; extracting an in-phase signal and a quadrature-phase signal from the reflected radio waves by quadrature demodulation, and acquiring a Lissajous waveform based on the extracted in-phase signal and quadrature-phase signal; acquiring a first estimated distance in the I-axis direction between the center of the Lissajous waveform and the origin of the IQ orthogonal coordinate system, based on the coordinates in an IQ orthogonal coordinate system of a plurality of points forming the Lissajous waveform, and a second estimated distance in the Q-axis direction between the center of the Lissajous waveform and the origin of the IQ orthogonal coordinate system; correcting an offset of the Lissajous waveform based on the first and second estimated distances; and acquiring information indicating the motion based on the corrected Lissajous waveform.

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