Radar system and its signal processing method

Abstract

The present invention provides a radar system and a signal processing method thereof capable of acquiring a minute displacement component of a displacement acquisition target with high accuracy. The present invention is provided with: a first device (1) that transmits and receives radio waves and acquires displacement of a displacement acquisition target; and a second device (2) that is installed on the displacement acquisition target and is disposed within a range in which radio waves can be transmitted and received to and from the first device (1). The second device (2) has a first mode for re-radiating a received radio wave and a second mode for delaying the phase of the received radio wave and re-radiating the same. The first device (1): calculates, on the basis of first IQ information (pi) acquired in a first period in which the second device (2) operates in a first mode and second IQ information (ps) acquired in a second period in which the second device (2) operates in a second mode, a direct current component of the first IQ information (pi); and generates third IQ information (pi') obtained by removing the direct current component from the first IQ information (pi).

Description

[Technical Field]

[0001] The present invention relates to a radar system and a method for processing its signals. [Background technology]

[0002] Conventionally, configurations for acquiring biological information of the human body using radio wave sensors such as radar (RADAR: Radio Detection and Ranging) have been disclosed (for example, Patent Documents 1 and 2). Patent Document 2 discloses a configuration in which information on the distance to the surface of the living body is output by processing an I signal obtained by multiplying the electromagnetic wave signal and the reflected wave signal, and a Q signal obtained by delaying the I signal by a predetermined phase, the received intensity of the reflected wave is output from the diameter of the circle drawn by the signal point obtained by unfolding the I signal and the Q signal on a complex plane, and the amount of phase change of the reflected wave is output from the displacement angle of the range in which the signal point is displaced relative to the center of the circle. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-202921 [Patent Document 2] Japanese Patent Publication No. 2020-146235 [Overview of the project] [Problems that the invention aims to solve]

[0004] The received signal contains DC components other than signals corresponding to biological information. These DC components include, for example, reflected components from stationary objects other than the human body. If these DC components are large, it may be impossible to acquire minute displacement components (biological information, etc.), such as surface displacement of the human body, which are relatively small compared to the DC components, with high accuracy.

[0005] This disclosure has been made in view of the above, and aims to realize a radar system and a signal processing method thereof that can acquire minute displacement components of a displacement target with high accuracy. [Means for solving the problem]

[0006] A radar system in one aspect of this disclosure includes a first device that acquires the displacement of a displacement acquisition target based on received waves, and a second device installed on the displacement acquisition target and positioned within a range that enables the transmission and reception of radio waves between it and the first device, wherein the second device has a first mode of re-radiating received radio waves and a second mode of re-radiating received radio waves with a phase delay, and the first device calculates the DC component of the first information based on first information acquired during a first period when the second device is operating in the first mode, and second information acquired during a second period when the second device is operating in the second mode, and generates third information by removing the DC component from the first information.

[0007] This configuration allows for the acquisition of a third set of information by removing the DC component from the reflected wave component from stationary objects other than the object whose displacement is being acquired. This enables high-precision acquisition of minute displacement components of the object whose displacement is being acquired.

[0008] A signal processing method for a radar system according to one aspect of the present disclosure comprises: a first device for acquiring the displacement of a displacement acquisition target; and a second device installed on the displacement acquisition target and positioned within a range from the first device for transmitting and receiving radio waves, wherein the second device has a first mode for re-radiating received radio waves and a second mode for re-radiating received radio waves with a phase delay, and the first device comprises: a first step of generating first information based on radio waves received during a first period in which the second device is operating in the first mode; a second step of generating second information based on radio waves received during a second period in which the second device is operating in the second mode; a third step of calculating the DC component of the first information based on the first information and the second information; and a fourth step of generating third information by removing the DC component from the first information.

[0009] This configuration allows for the acquisition of a third set of information by removing the DC component from the reflected wave component from stationary objects other than the object whose displacement is being acquired. This enables high-precision acquisition of minute displacement components of the object whose displacement is being acquired. [Effects of the Invention]

[0010] According to this disclosure, a radar system and a signal processing method thereof can be realized that can acquire minute displacement components of a displacement target with high accuracy. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a block diagram showing a schematic configuration of a radar system according to an embodiment. [Figure 2A] Figure 2A is a block diagram showing a first specific example of a phase shifter for the second device. [Figure 2B] Figure 2B is a block diagram showing a second specific example of the phase shifter of the second device. [Figure 3A] Figure 3A is the first figure showing the relationship between the transmitted wave of the first device and the switching timing of the phase shifter in the first specific example. [Figure 3B] Figure 3B is the second figure showing the relationship between the transmitted wave of the first device and the switching timing of the phase shifter in the first specific example. [Figure 4A] Figure 4A is the first figure showing the relationship between the transmitted wave of the first device and the switching timing of the phase shifter in the second specific example. [Figure 4B] Figure 4B is the second figure showing the relationship between the transmitted wave of the first device and the switching timing of the phase shifter in the second specific example. [Figure 5] Figure 5 is a complex plane diagram showing an example of the relationship between the first IQ information and the second IQ information. [Figure 6] Figure 6 is a flowchart showing a specific example of the processing of the radar system according to the embodiment. [Figure 7] Figure 7 is a subflowchart showing an example of the IQ information generation process. [Figure 8] Figure 8 is a subflowchart showing an example of a DC component removal process. [Figure 9] Figure 9 is a subflowchart showing an example of the displacement calculation process. [Figure 10A] Figure 10A is the first conceptual diagram showing a specific example of the DC component calculation process on the complex plane. [Figure 10B] Figure 10B is the first conceptual diagram showing the coordinates of the first IQ information and the second IQ information after DC component removal on the complex plane. [Figure 11A] Figure 11A is a second conceptual diagram showing a specific example of the DC component calculation process on the complex plane. [Figure 11B] Figure 11B is a second conceptual diagram showing the coordinates of the first and second IQ information after DC component removal on the complex plane. [Figure 12] Figure 12 is a flowchart showing a modified example of the processing of the radar system according to the embodiment. [Figure 13] Figure 13 is a subflowchart showing an example of the IQ information generation process related to a modified example. [Modes for carrying out the invention]

[0012] A radar system and its signal processing method according to an embodiment will be described in detail below with reference to the drawings. However, this embodiment does not limit the present disclosure.

[0013] Figure 1 is a block diagram showing the schematic configuration of a radar system according to an embodiment. The radar system 100 according to Embodiment 1 includes a first device 1 and a second device 2.

[0014] The first device 1 is a so-called radar (RADAR: Radio Detection and Ranging) device. Examples of radar devices include FMCW (Frequency Modulated Continuous Wave) radar, Doppler radar, pulse radar, etc. In this disclosure, the first device 1 comprises a transmitting / receiving unit 11, a DC component removal unit 12, and a displacement calculation unit 13.

[0015] The second device 2 is installed on a target whose displacement is to be acquired in the radar system 100 (specifically, a human body, or a target on which the displacement of the human body surface, such as a vehicle seat or bed, is transmitted). In this disclosure, the second device 2 comprises a directional coupler 21, a phase shifter 22, and a switch control unit 23.

[0016] The second device 2 is positioned within range of the first device 1, and has a first mode for re-radiating received radio waves and a second mode for re-radiating received radio waves with a phase delay.

[0017] The radio waves received by the second device 2 are input to the directional coupler 21 as the received wave Rx1. The directional coupler 21 outputs the received wave Rx1 to the phase shifter 22. Figure 2A is a block diagram showing a first specific example of the phase shifter of the second device. Figure 2B is a block diagram showing a second specific example of the phase shifter of the second device.

[0018] The phase shifter 22 is equipped with switch circuits SW1 and SW2 that switch between a path P1 that re-radiates the received wave Rx1 as a radiated wave Tx2 and a path P2 that re-radiates the radiated wave Tx2 with a phase delay of the received wave Rx1. In the configuration shown in Figure 2B, in a path connected by an open stub of length λ / 4, the impedance to the signal of wavelength λ at the connection point of the open stub is set to infinite. The phase shift amount (phase delay amount) θ in the phase shifter 22 is given in the range of 0 < θ < 2π, where the wavelength λ of the transmission frequency of the first device 1 (frequency of the radiated wave Tx1) is one period (2π).

[0019] The switch circuits SW1 and SW2 are controlled by the switch control unit 23. Figure 3A is the first figure showing the relationship between the transmitted wave of the first device and the switching timing of the phase shifter of the first specific example.

[0020] Figure 3A illustrates the radiated wave Tx1 when the first device 1 is an FMCW radar. In this example, the first device 1 transmits a chirp signal Ch that is linearly frequency-modulated from frequency f1 to frequency f2 at a predetermined period while providing a reset period rst. If the transmission period of the chirp signal Ch is, for example, 1 ms, the chirp signal Ch is linearly frequency-modulated from frequency f1 to frequency f2 at a period of, for example, 10 μs to 50 μs.

[0021] In the configuration of the first specific example shown in Figure 2A, the switch control unit 23 controls the chirp signal Ch i+1 During the reset period rst1 after receiving the signal, the switch control signal Ssig is controlled from "L" to "H", and the chirp signal Ch i Reset period after receiving rst i+1 In this configuration, the switch control signal Ssig is controlled from "H" to "L". This controls the chirp signals Ch1, Ch2, Ch3, ..., Ch i This is re-radiated as radiation wave Tx2 (first mode), and chirp signal Ch i+1 This is re-radiated as a radiation wave Tx2 delayed by a phase shift amount θ (second mode). For example, if the "L" selection period of the switch control signal Ssig in the switch control unit 23 is 10 times the transmission period of the chirp signal Ch (switch control frequency is 100 Hz), then i = 9.

[0022] Figure 3B is the second figure showing the relationship between the transmitted wave of the first device and the switching timing of the phase shifter of the first specific example. In Figure 3B, the switching period of the switch control signal in the switch control unit 23 is set to twice the transmission period of the chirp signal Ch (switch control frequency is 500 Hz). In this case, for example, at odd periods of the chirp signal Ch, the chirp signal Ch odd This is re-emitted as radiation wave Tx2 (first mode), and the chirp signal Ch is re-emitted at even periods of the chirp signal Ch evenIt is re-radiated as a radiated wave Tx2 that is delayed by the phase shift amount θ (second mode).

[0023] FIG. 4A is a first diagram showing the relationship between the transmission wave of the first device and the switching timing of the phase shifter of the second specific example.

[0024] In the configuration of the second specific example shown in FIG. 2B, the switch control unit 23 controls the switch control signal Ssig1 from "H" to "L" and the switch control signal Ssig2 from "L" to "H" during the reset period rst1 after receiving the chirp signal Ch. i+1 Also, during the reset period rst i after receiving the chirp signal Ch i+1 it controls the switch control signal Ssig1 from "L" to "H" and the switch control signal Ssig2 from "H" to "L". As a result, the chirp signals Ch1, Ch2, Ch3, ···, Ch i are re-radiated as the radiated wave Tx2 (first mode), and the chirp signal Ch i+1 is re-radiated as a radiated wave Tx2 that is delayed by the phase shift amount θ (second mode). For example, when the "H" selection period of the switch control signal Ssig1 in the switch control unit 23 and the "L" of the switch control signal Ssig2 are 10 times the transmission period of the chirp signal Ch (switch control frequency is 100 Hz), i = 9.

[0025] FIG. 4B is a second diagram showing the relationship between the transmission wave of the first device and the switching timing of the phase shifter of the second specific example. In FIG. 4B, the switching period of the switch control signals Ssig1 and Ssig2 in the switch control unit 23 is set to be 2 times the transmission period of the chirp signal Ch (switch control frequency is 500 Hz). In this case, for example, during the odd periods of the chirp signal Ch odd is re-radiated as the radiated wave Tx2 (first mode), and during the even periods of the chirp signal Ch even is re-radiated as a radiated wave Tx2 that is delayed by the phase shift amount θ (second mode).

[0026] In Figure 2B, the switch control unit 23 outputs switch control signals Ssig1 and Ssig2 to control switch circuits SW1 and SW2 respectively, but it is also possible for the switch control unit 23 to output a switch control signal Ssig to control switch circuit SW2 and control switch circuit SW1 with a signal that is the logical inversion of the switch control signal Ssig. In this case, the control logic of the switch control signal Ssig in the switch control unit 23 will be the same as in Figure 3A or Figure 3B.

[0027] The first device 1 receives the radiated wave Tx2 from the second device 2. Here, the received wave Rx2 received by the first device 1 includes not only the radiated wave Tx2 but also reflected wave components from stationary objects other than the target whose displacement is to be acquired in the radar system 100. Reflected waves from such stationary objects include a DC component that is unrelated to the minute displacement component (AC component) in the target whose displacement is to be acquired.

[0028] In this disclosure, the DC component removal unit 12 generates third IQ information (third information) by removing the DC component from the first IQ information, based on first IQ information (first information) acquired during a first period when the second device 2 is operating in the first mode, and second IQ information (second information) acquired during a second period when the second device 2 is operating in the second mode. This provides third IQ information from which the DC component included in the reflected wave component from stationary objects other than targets targeted for displacement acquisition in the radar system 100 has been removed.

[0029] Specifically, the transmitting / receiving unit 11 generates an I signal in phase with the radiated wave Tx1 and a Q signal orthogonal to the radiated wave Tx1 based on the received wave Rx2. The I signal and the Q signal can be defined by coordinates on a complex plane defined by the real axis (Re axis) and the imaginary axis (Im axis).

[0030] Figure 5 is a complex plan view showing an example of the relationship between the first IQ information and the second IQ information. The transmitting / receiving unit 11 receives the I signal re generated in the first mode. i and Q signal im iThe coordinates of the first IQ information are defined as p on the complex plane, and the I signal res and Q signal ims acquired in the second mode are defined as the second IQ information on the complex plane. In Figure 5, the coordinates of the first IQ information are defined as p on the complex plane defined by the real axis (Re axis) and the imaginary axis (Im axis). i (re i ,im i ) and the coordinates of the second IQ information are set to ps(res,ims). Also, the first IQ information p i The coordinates of the DC component are on the PC i (rec i imc i ) and set the coordinates of the 3rd IQ information to p i '(res i ',ims i It is set as ').

[0031] In the following explanation, the coordinate p on the complex plane is used. i (re i ,im i The first IQ information defined as "first IQ information p i It is also called "second IQ information ps," and the second IQ information defined by the coordinates ps(res,ims) on the complex plane is also called "second IQ information ps." i (rec i imc i ) First IQ information p defined by i The DC component is simply called "DC component pc" i It is also called the coordinate p on the complex plane. i '(res i ',ims i The third IQ information defined in ') is called "Third IQ Information p i It is also called '.

[0032] Figure 5 shows an example where the wavelength of the transmission frequency of the first device 1 (frequency of the radiated wave Tx1) is λ, and the phase shift amount (phase delay amount) θ in the second mode is λ / 2. In this example, the first IQ information p i The DC component contained in pc i This is the first IQ information p i It can be calculated as the average value of the second IQ information ps. At this time, the DC component pc on the complex plane i coordinates pci (rec i imc i ) is shown by equation (1) below.

[0033]

number

[0034] The DC component pc shown in (1) above i The I signal component of rec i The first IQ information p i The I signal re i Subtract from the DC component pc i Q signal component imc i The first IQ information p i Q signal im i By subtracting from this, the displacement component p in the object of displacement acquisition is obtained. i ' is obtained. Displacement component p in the object of displacement acquisition. i ' is a coordinate pc on the complex plane. i '(rec i -rec i imc i -imc i The coordinates p with the origin at (=p0(0,0)) i '(re i ',im i It can be expressed as '). The coordinate p i '(re i ',im i ') is the coordinate p of the third IQ information in this disclosure. i '(re i ',im i Let's assume it's '). The coordinates of the third IQ information are p. i '(re i ',im i ') is shown by equation (2) below. In the following explanation, the coordinate p on the complex plane is i '(re i ',im i The third IQ information defined in ') is called "Third IQ Information p i It is also called '.

[0035]

number

[0036] The displacement calculation unit 13 processes the third IQ information p generated by the DC component removal unit 12. i Based on ', the displacement d to be acquired i Specifically, the displacement calculation unit 13 calculates the third IQ information p generated by the DC component removal unit 12. i Find the argument angle of ', and the phase shift φ i Calculate the displacement d of the displacement to be acquired. i When the wavelength of the transmission frequency of the first device 1 (frequency of the radiated wave Tx1) is λ, it is expressed by the following equation (3).

[0037]

number

[0038] The following describes a specific example of processing in the radar system 100 according to the embodiment. Figure 6 is a flowchart showing a specific example of processing in the radar system according to the embodiment. Here, we will describe an example in which the phase shifter 22 of the second device 2 has the configuration of the first specific example shown in Figure 2A. In addition, in the processing described below, the first device 1 does not know the operating timing of the second mode in the second device 2.

[0039] In the process shown in Figure 6, the first device 1 performs the following: IQ information generation process (step S100) which generates first IQ information and second IQ information based on the received wave Rx2; DC component removal process (step S400) which generates third IQ information by removing the DC component of the first IQ information based on the first IQ information and second IQ information obtained by the IQ information generation process; and displacement calculation process (step S500) which calculates the displacement of the target for displacement acquisition based on the third IQ information generated by the DC component removal process. Figure 7 is a subflowchart showing an example of the IQ information generation process. Figure 8 is a subflowchart showing an example of the DC component removal process. Figure 9 is a subflowchart showing an example of the displacement calculation process.

[0040] First, the first device 1 executes the IQ information generation process shown in FIG. 7. The IQ information generation process is executed by the transceiver unit 11. Note that the IQ information is generated by known filtering processes, FFT processes, etc. The present disclosure is not limited by the method of generating the IQ information.

[0041] As a prerequisite for the IQ information generation process shown in FIG. 7, the switch control unit 23 of the second device 2 sets the switch control signal Ssig to "H" during the reset period rst1 after receiving the chirp signal Ch i+1 (see FIG. 3A). As a result, the second device 2 operates in the first mode.

[0042] In the IQ information generation process shown in FIG. 7, the first device 1 first resets the number of transmissions n of the chirp signal Ch in the first mode and the number of receptions i of the received wave Rx2 until the acquisition of the second IQ information ps in the second mode (n = 0, i = 0, step S101), increments the number of transmissions n of the chirp signal Ch in the first mode (n = n + 1, step S102), and the transceiver unit 11 transmits the chirp signal Ch n (Ch1 (see FIG. 3A, etc.)) (step S103).

[0043] The transceiver unit 11 receives the radio wave including the radiated wave Tx2 from the second device 2 (step S104). Based on the received wave Rx2 received in step S104, the transceiver unit 11 generates the IQ information p n (step S105).

[0044] The first device 1 sets the IQ information p n to p n-1 (p n-1 = p n , step S106), increments the number of transmissions n of the chirp signal Ch in the first mode (n = n + 1, step S107), and the transceiver unit 11 transmits the chirp signal Ch n (step S108).

[0045] Then, the transceiver unit 11 receives the received wave Rx2 (step S109) and the IQ information pn Generate (step S110).

[0046] The transceiver unit 11 calculates the difference value Δp between the IQ information p n and the IQ information p n-1 (Δp = |p n - p n-1 |, step S111), and determines whether the difference value Δp exceeds a predetermined threshold value p th (Δp > p th , step S112). If the difference value Δp is less than or equal to the predetermined threshold value p th (Δp ≤ p th , step S112; No), the reception count i of the received wave Rx2 until the acquisition of the second IQ information ps in the second mode is incremented (i = i + 1, step S113), and the IQ information p n is set as the first IQ information p i (p i = p n ), output to the subsequent DC component removal unit 12, and the processes after step S106 are repeatedly executed.

[0047] When the difference value Δp exceeds the predetermined threshold value p th (Δp > p th , step S112; Yes), the transceiver unit 11 sets the reception count i of the current received wave Rx2 as the total number I of the first IQ information p i (I = i, step S115), and sets the IQ information p n generated in the process of the immediately preceding step S110 as the second IQ information ps (ps = p n ), and outputs it to the subsequent DC component removal unit 12.

[0048] Here, when the difference value Δp exceeds the predetermined threshold value p th (Δp > p th , step S112; Yes), the switch control unit 23 of the second device 2 controls the chirp signal Ch iThis indicates that during the reset period rsti+1 after reception, the switch control signal Ssig was controlled from "H" to "L". As a result, the second device 2 operates in second mode, and consequently, the IQ information p generated based on the received wave Rx2 is n The previous value was p n-1 This will result in significant fluctuations. In this disclosure, IQ information p n The previous value p n-1 The difference value Δp = |p n -p n-1 | is threshold p th If it is detected that the value exceeds (Δp>p th Step S112; Yes), the IQ information p generated in the processing of the immediately preceding step S110 n This is used as the second IQ information, ps (ps = p n (Step S116).

[0049] Returning to Figure 6, the first device 1 receives the first IQ information p acquired by the transmitting / receiving unit 11. i The number i is reset (i=0, step S200), then the number i is incremented (i=i+1, step S300), and the DC component removal process (step S400) is executed. The DC component removal process is performed by the DC component removal unit 12.

[0050] In the DC component removal process shown in Figure 8, the DC component removal unit 12 first processes the first IQ information p i DC component of pc i The following is calculated (step S401). Figure 10A is the first conceptual diagram showing a specific example of the DC component calculation process on the complex plane. On the complex plane, coordinate p represents the first IQ information. i (re i ,im i The line containing the coordinates ps(res,ims) representing the second IQ information can be expressed by equation (4) below, where a is the slope and b is the intercept.

[0051]

number

[0052] The slope a can be expressed by equation (5) below. In equation (5) below, re i is the first IQ information p i This shows the I signal included in im i is the first IQ information p i This shows the Q signal contained in ps. Additionally, res shows the I signal contained in the second IQ information ps, and ims shows the Q signal contained in the second IQ information ps.

[0053]

number

[0054] The coordinate p represents the first IQ information on the complex plane. i (re i ,im i The I signal component rem of the midpoint coordinate pm(rem,imm) of the coordinate ps(res,ims) which shows the second IQ information is given by equation (6) below, and the Q signal component imm is given by equation (7) below.

[0055]

number

[0056]

number

[0057] The coordinate p represents the first IQ information on the complex plane. i (re i ,im i ) (and coordinates ps(res,ims) indicating the 2nd IQ information) and coordinates pc indicating the DC component i (rec i imc i ) is the coordinate p that indicates the first IQ information. i (re i ,im i ) and the coordinates passing through the midpoint pm(rem,imm) of the coordinates ps(res,ims) representing the second IQ information, and the coordinates p representing the first IQ information i (rei ,im i It lies on a straight line perpendicular to the line containing the coordinates ps(res,ims) that represent the second IQ information. When the slope of this line is a' and the intercept is b', it can be expressed by equation (8) below.

[0058]

number

[0059] The slope a' can be expressed by equation (9) below. The intercept b can be expressed by equation (10) below.

[0060]

number

[0061]

number

[0062] DC component coordinates pc i (rec i imc i Since ) are coordinates on the line shown in equation (8) above, we obtain equation (11) below. Substituting the slope a' shown in equation (9) above and the intercept b' shown in equation (10) above into equation (11) below, we obtain the relationship shown in equation (12) below.

[0063]

number

[0064]

number

[0065] Furthermore, the coordinates on the straight line shown in equation (8) above are the coordinates of the DC component pc i (rec i imc i When this is the case, the coordinates of the DC component are pc i (reci imc i ) and coordinate p showing the first IQ information i (re i ,im i ) and the line segment L connecting the midpoint coordinates pm(rem,imm) of the coordinates ps(res,ims) which represent the second IQ information. pcpm The coordinates ps(res,ims) represent the second IQ information and the coordinates p represent the first IQ information. i (re i ,im i ) and the line segment L connecting the midpoint coordinates pm(rem,imm) of the coordinates ps(res,ims) which represent the second IQ information. pspm This can be expressed by equation (13) below, using the phase shift amount (phase delay amount) θ in the phase shifter 22 of the second device 2.

[0066]

number

[0067] Line segment L pcpm It is expressed by equation (14) below, and the line segment L pspm This is expressed by equation (15) below.

[0068]

number

[0069]

number

[0070] From equation (13) above, and from equation (15) above, the relationship shown in equation (16) below is obtained.

[0071]

number

[0072] Figure 10B is the first conceptual diagram showing the coordinates of the first IQ information and the second IQ information after DC component removal on the complex plane.

[0073] As shown in Figure 10B, the first IQ information p after the removal of the DC component i 'I signal component re i ' is the first IQ information p i The I signal re i DC component from pc i The I signal component of rec i It can be calculated by subtracting the following. Also, the first IQ information p after removing the DC component i ' Q signal component im i ' is the first IQ information p i From the Q signal, the DC component pc i Q signal component imc i It can be calculated by subtracting [a certain value].

[0074] Similarly, the I signal component res' of the second IQ information ps' after the DC component has been removed is obtained by subtracting the DC component pc from the I signal res of the second IQ information ps. i The I signal component of rec i It can be calculated by subtracting pc from the Q signal component ims' of the second IQ information ps' after the DC component has been removed. i Q signal component imc i It can be calculated by subtracting [a certain value].

[0075] The coordinates ps'(res',ims') representing the second IQ information are the same as the coordinates p representing the first IQ information. i '(re i ',im i Since the coordinates are delayed by the amount of phase shift θ in the phase shifter 22 of the second device 2 relative to '), equations (17) and (18) below are obtained.

[0076]

number

[0077]

number

[0078] Using equation (12) above, and equations (16) to (18) above, the first IQ information p i (and the DC component pc of the second IQ information ps) i The I signal component of rec i and Q signal component imc i It is possible to calculate this.

[0079] Figure 11A is a second conceptual diagram showing a specific example of the DC component calculation process on the complex plane. Figure 11B is a second conceptual diagram showing the coordinates of the first IQ information and the second IQ information after the DC component has been removed on the complex plane.

[0080] Figures 11A and 11B show the case where the phase shift amount (phase delay amount) θ in the phase shifter 22 of the second device 2 is λ / 2 (where λ is the wavelength of the transmission frequency of the first device 1 (frequency of the radiated wave Tx1)). In this case, as described above, the DC component pc i This is the first IQ information p i It can be calculated as the average of the second IQ information ps. At this time, the coordinates pc of the DC component on the complex plane i (rec i imc i ) is shown by equation (1) above.

[0081] DC component pc i After the calculation process (step S401), the DC component removal unit 12 processes the first IQ information p i The I signal re i DC component from pc i The I signal component of rec i Subtract the first IQ information p i Q signal im i DC component from pc i Q signal component imc i Subtracting this, we obtain the third IQ information p shown in equation (2) above. i The '' is generated (step S402) and output to the subsequent displacement calculation unit 13.

[0082] Returning to Figure 6, the first device 1 then performs the displacement calculation process (step S500). The displacement calculation process is performed by the displacement calculation unit 13.

[0083] In the displacement calculation process shown in Figure 9, the displacement calculation unit 13 first processes the third IQ information p generated by the DC component removal unit 12. i The angular displacement of ' is determined and the phase shift φ is calculated (step S501). Then, the displacement calculation unit 13 uses the wavelength λ of the transmission frequency of the first device 1 (frequency of the radiated wave Tx1) to calculate the displacement d of the displacement acquisition target using the above equation (3). i Calculate (Step S502).

[0084] Returning to Figure 6, the first device 1 receives the first IQ information p acquired by the transmitting / receiving unit 11. i The number i is the first IQ information p i It is determined whether the total number I has been reached (step S600). The first IQ information p obtained by the transmitting / receiving unit 11 i The number i is the first IQ information p i If the total number I has not been reached (step S600; No), the process returns to step S300, and the DC component removal process (step S400) and the displacement calculation process (step S500) are repeatedly executed. The first IQ information p acquired by the transmitting / receiving unit 11 i The number i is the first IQ information p i When the total number I is reached, the process returns to step S100 and the process shown in Figure 6 is repeatedly executed.

[0085] The process described above allows for the suppression of the influence of DC components contained in reflected wave components from stationary objects other than the human body, for example, when the target of displacement acquisition is the human body. This makes it possible to acquire minute displacement components such as respiration and pulse with high accuracy.

[0086] (modified version) Figure 12 is a flowchart showing a modified version of the processing of the radar system according to the embodiment. In the modified version shown in Figure 12, as shown in Figure 3B, an example of processing is shown when the switching period of the switch control signal in the switch control unit 23 is set to twice the transmission period of the chirp signal Ch. Note that the DC component removal processing (step S400) and the displacement calculation processing (step S500) are the same as in the embodiment described above, so their explanation will be omitted, and here we will explain the IQ information generation processing (step S100a) related to the modified version.

[0087] Figure 13 is a subflowchart showing an example of the IQ information generation process related to the modified example. As a prerequisite for the IQ information generation process related to the modified example shown in Figure 13, the switch control unit 23 of the second device 2 receives the chirp signal Ch even (See Figure 3B) Reset period after reception: rst odd In this configuration, the switch control signal Ssig is set to "H". As a result, the second device 2 operates in the first mode.

[0088] In the IQ information generation process shown in Figure 13, the transmitting / receiving unit 11 transmits the chirp signal Ch odd Transmit (step S103a), receive radio waves (received wave Rx2) including the radiated wave Tx2 from the second device 2 (step S104), and based on the received radio waves (received wave Rx2), first IQ information p i Generate (step S105a).

[0089] The switch control unit 23 of the second device 2 receives the chirp signal Ch odd (See Figure 3B) Reset period after reception: rst even In this configuration, the switch control signal Ssig is set to "L". As a result, the second device 2 operates in the second mode.

[0090] The transmitting / receiving unit 11 transmits the chirp signal Ch even The device transmits (step S108a), receives radio waves (received wave Rx2) including the radiated wave Tx2 from the second device 2 (step S109), and generates second IQ information ps based on the received radio waves (received wave Rx2) (step S110a).

[0091] Returning to Figure 12, the first device 1 receives the first IQ information p obtained by the IQ information generation process related to the modified example. i Using the second IQ information ps, a DC component removal process (step S400, see Figure 8) is performed, and the third IQ information p generated by the DC component removal process is obtained. i Using this, the displacement calculation process (step S500, see Figure 9) is executed.

[0092] The switch control unit 23 of the second device 2 receives the chirp signal Ch even (See Figure 3B) Reset period after reception: rst odd In this configuration, the switch control signal Ssig is set to "H". As a result, the second device 2 operates in the first mode. The first device 1 then repeatedly executes the process shown in Figure 13.

[0093] As described above, the radar system 100 according to the embodiment and modified example comprises a first device 1 that transmits and receives radio waves to acquire the displacement of a displacement acquisition target, and a second device 2 that is installed on the displacement acquisition target of the radar system 100 and is positioned within a range where radio waves can be transmitted and received between it and the first device 1. The second device 2 has a first mode of re-radiating received radio waves and a second mode of re-radiating received radio waves with a phase delay. The first device 1 receives first IQ information (first information) p based on the radio waves received during a first period when the second device 2 is operating in the first mode. i The first device generates the first IQ information p based on the radio waves received during the second period when the second device 2 is operating in the second mode. The first device 1 then generates the first IQ information p i And based on the second IQ information ps, the first IQ information p i DC component of pc i The DC component pc is calculated and i The first IQ information p i Third IQ information (third information) removed from p iThis generates the third IQ information (third information) p, which removes the DC component contained in the reflected wave component from stationary objects other than the target whose displacement is to be acquired in the radar system 100, and the DC component corresponding to the distance between the second device 2 and the first device 1. i ' can be obtained.

[0094] Furthermore, the first device 1 receives the first IQ information p i DC component of pc i Third IQ information (third information) with the removed p i Using ', the displacement d of the target displacement to be acquired i This calculates the minute displacement components of the target of displacement acquisition.

[0095] This disclosure may take the following configuration, as described above, or alternatively.

[0096] (1) A radar system according to one aspect of the present disclosure includes a first device that transmits and receives radio waves to acquire the displacement of a displacement acquisition target, and a second device installed on the displacement acquisition target and positioned within a range from which radio waves can be transmitted and received between the second device and the first device, wherein the second device has a first mode of re-radiating received radio waves and a second mode of re-radiating received radio waves with a phase delay, and the first device calculates the DC component of the first information based on first information acquired during a first period in which the second device is operating in the first mode, and second information acquired during a second period in which the second device is operating in the second mode, and generates third information by removing the DC component from the first information.

[0097] In this configuration, a third set of information can be obtained by removing the DC component contained in the reflected wave component from stationary objects other than the object whose displacement is being acquired.

[0098] (2) In the radar system described in (1) above, the first information and the second information are defined in terms of coordinates on the complex plane.

[0099] (3) In the radar system described in (2) above, the first device calculates the DC component using the phase delay amount of the radio waves re-radiated when the second device is operating in the second mode.

[0100] In this configuration, the DC component of the first information can be calculated based on the phase delay of the radio waves re-radiated when the second device is operating in the second mode, the first information acquired during the first period when the second device is operating in the first mode, and the second information acquired during the second period when the second device is operating in the second mode. By removing this DC component from the first information, a third piece of information can be obtained that allows for highly accurate acquisition of minute displacement components of the target of displacement acquisition.

[0101] (4) In the radar system described in (2) above, the second device re-radiates the received radio waves with the phase delayed by half a wavelength of the transmission frequency of the first device in the second mode.

[0102] In this configuration, the average value of the first and second pieces of information can be calculated as the DC component of the first piece of information.

[0103] (5) In the radar system described in (4) above, the first device calculates the average value of the first information and the second information as the DC component.

[0104] This configuration makes it easy to calculate the DC component of the first information.

[0105] (6) In the radar systems described in (1) to (5) above, the first device calculates the displacement of the object to be acquired based on the third information.

[0106] This configuration allows for the acquisition of highly accurate displacement components while suppressing the influence of DC components included in reflected wave components from stationary objects other than the target of displacement acquisition.

[0107] (7) A signal processing method for a radar system according to one aspect of the present disclosure is a signal processing method for a radar system comprising: a first device that transmits and receives radio waves to acquire the displacement of a displacement acquisition target; and a second device installed on the displacement acquisition target and positioned within a range from which radio waves can be transmitted and received between the first device and the second device, wherein the second device has a first mode of re-radiating received radio waves and a second mode of re-radiating received radio waves with a phase delay, and the first device has a first step of generating first information based on radio waves received during a first period in which the second device is operating in the first mode; a second step of generating second information based on radio waves received during a second period in which the second device is operating in the second mode; a third step of calculating the DC component of the first information based on the first information and the second information; and a fourth step of generating third information by removing the DC component from the first information.

[0108] In this configuration, a third set of information can be obtained by removing the DC component contained in the reflected wave component from stationary objects other than the object whose displacement is being acquired.

[0109] (8) In the signal processing method of the radar system described in (7) above, the first information and the second information are defined by coordinates on the complex plane.

[0110] (9) In the signal processing method for the radar system described in (8) above, the first device calculates the DC component in the third step using the phase delay amount of the radio waves re-radiated when the second device is operating in the second mode.

[0111] In this configuration, the DC component of the first information can be calculated based on the phase delay of the radio waves re-radiated when the second device is operating in the second mode, the first information acquired during the first period when the second device is operating in the first mode, and the second information acquired during the second period when the second device is operating in the second mode. By removing this DC component from the first information, a third piece of information can be obtained that allows for highly accurate acquisition of minute displacement components of the target of displacement acquisition.

[0112] (10) In the signal processing method of the radar system described in (8) above, the second device re-radiates the received radio waves with the phase delayed by half a wavelength of the transmission frequency of the first device in the second mode.

[0113] In this configuration, the average value of the first and second pieces of information can be calculated as the DC component of the first piece of information.

[0114] (11) In the signal processing method of the radar system described in (10) above, the first device calculates the average value of the first information and the second information as the DC component in the third step.

[0115] This configuration makes it easy to calculate the DC component of the first information.

[0116] (12) In the signal processing method of the radar system described in (7) to (11) above, the first device further comprises a fifth step of calculating the displacement of the displacement to be acquired based on the third information.

[0117] This configuration allows for the acquisition of highly accurate displacement components while suppressing the influence of DC components included in reflected wave components from stationary objects other than the target of displacement acquisition.

[0118] This disclosure makes it possible to realize a radar system and a signal processing method thereof that can acquire minute displacement components of a displacement target with high precision. [Explanation of Symbols]

[0119] 1 1st device 2 Second device 11 Transmitter / Receiver 12 DC component removal section 13 Displacement Calculation Unit 21 Directional coupler 22 Phase shifter 23 Switch control unit

Claims

1. A first device that transmits and receives radio waves to acquire the displacement of the object to be acquired, A second device is installed on the object to be acquired for displacement and is positioned within a range that allows it to transmit and receive radio waves with the first device, Equipped with, The second device is The first mode involves re-emitting the received radio waves, The second mode involves delaying the phase of the received radio waves and re-emitting them, It has, The first apparatus is Based on the first information acquired during the first period in which the second device is operating in the first mode, and the second information acquired during the second period in which the second device is operating in the second mode, the DC component of the first information is calculated, and a third information is generated by removing the DC component from the first information. Radar system.

2. A radar system according to claim 1, The first and second pieces of information are defined in terms of coordinates on the complex plane. Radar system.

3. A radar system according to claim 2, The first apparatus is The DC component is calculated using the phase delay amount of the radio waves re-radiated when the second device is operating in the second mode. Radar system.

4. A radar system according to claim 2, The second device is In the second mode, the phase of the received radio wave is delayed by half a wavelength of the transmission frequency of the first device and then re-radiated. Radar system.

5. A radar system according to claim 4, The first apparatus is The average value of the first information and the second information is calculated as the DC component. Radar system.

6. A radar system according to any one of claims 1 to 5, The first device calculates the displacement of the object to be acquired based on the third information. Radar system.

7. A signal processing method for a radar system comprising: a first device that transmits and receives radio waves to acquire the displacement of a target for displacement acquisition; and a second device installed on the target for displacement acquisition and positioned within a range that enables the transmission and reception of radio waves between it and the first device, The second device is The first mode involves re-emitting the received radio waves, The second mode involves delaying the phase of the received radio waves and re-emitting them, It has, The first apparatus is A first step of generating first information based on radio waves received during a first period in which the second device is operating in the first mode, A second step of generating second information based on radio waves received during a second period in which the second device is operating in the second mode, A third step of calculating the DC component of the first information based on the first and second information, A fourth step is to generate third information by removing the DC component from the first information, Having, A signal processing method for radar systems.

8. A signal processing method for a radar system according to claim 7, The first and second pieces of information are defined in terms of coordinates on the complex plane. A signal processing method for radar systems.

9. A signal processing method for a radar system according to claim 8, The first apparatus is In the third step, the DC component is calculated using the phase delay amount of the radio waves re-radiated when the second device is operating in the second mode. A signal processing method for radar systems.

10. A signal processing method for a radar system according to claim 8, The second device is In the second mode, the phase of the received radio wave is delayed by half a wavelength of the transmission frequency of the first device and then re-radiated. A signal processing method for radar systems.

11. A signal processing method for a radar system according to claim 10, The first apparatus is In the third step, the average value of the first information and the second information is calculated as the DC component. A signal processing method for radar systems.

12. A signal processing method for a radar system according to any one of claims 7 to 11, The first apparatus is The system further includes a fifth step of calculating the displacement of the target for displacement acquisition based on the third information, A signal processing method for radar systems.

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