Radar system and received signal processing method

Abstract

To provide a radar device and a received signal processing method that can improve the detection accuracy of objects such as living organisms while suppressing the complexity of the configuration.SOLUTION: A receiving unit of a radar device includes: a leakage path component detection unit that extracts a detected component appearing at a specific distance in a received signal as a leakage path component of a signal from a transmitting unit to the receiving unit; a leakage path representative value acquisition unit that acquires a representative value of the leakage path component based on a time-series signal of the extracted leakage path component within a predetermined period; and a correction unit that uses the time-series signal of the leakage path component and the representative value of the leakage path to correct the time-series signal of the detected component appearing at an object detection distance in the received signal.SELECTED DRAWING: Figure 2

Description

Technical Field

[0005]

[0001] The present invention relates to a radar device capable of detecting the presence of a living body such as a human, and a method for processing a received signal.

Background Art

[0002] Conventionally, radar devices that capture minute changes in radio wave propagation associated with unique body movements (e.g., body movements due to breathing) of a living body and detect the presence or absence of the living body have been widely proposed (see, for example, Patent Document 1).

[0003] This type of radar device transmits a transmission signal obtained by up-converting a pulse signal, and receives, as a received signal, a signal reflected by the detection target. An amplitude change indicating the presence of the detection target appears in the received signal. In particular, when the detection target is a living organism, characteristic amplitude changes such as breathing appear in the received signal. Therefore, the radar device analyzes such amplitude changes by signal processing to detect the presence of a living body.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in this type of radar device, when the temperature of an amplifier or a local oscillator constituting the radar device changes, the gain of the amplifier and the phase of the local oscillator change. In the radar device, when such gain changes or phase changes occur while detecting a living body, even though the detected object is an inanimate object, it may be recognized that the detected object is slightly moving as if it were a living body, and thus there is a risk of determining that it is a living body.

[0006] This problem is particularly noticeable immediately after startup, when the temperature of various parts within the radar system changes rapidly and the characteristics of those parts change relatively significantly. One possible solution to this problem is to detect the temperature of each part (circuit) within the radar system in real time and add a correction to the received signal based on the temperature of each part.

[0007] However, adopting this method requires performing different temperature compensation for each part (circuit) with different temperature characteristics, leading to increased complexity of the configuration.

[0008] The present invention has been made in consideration of the above points, and provides a radar device and a received signal processing method that can improve the detection accuracy of objects such as living organisms while suppressing the complexity of the configuration. [Means for solving the problem]

[0009] One aspect of the radar device of the present invention is A transmitting unit that transmits a wave from a transmitting antenna, A receiving unit that detects an object based on a received signal including reflected waves received by a receiving antenna, A radar system having, The receiving unit is A leakage path component detection unit extracts a detection component that appears at a specific distance in the received signal as a leakage path component of the signal from the transmitting unit to the receiving unit, The aforementioned leakage path component A leakage path representative value acquisition unit obtains a representative value of the leakage path component based on the time-series signal of the leakage path component extracted by the detection unit within a predetermined period, The time-series signal of the leakage path component extracted by the leakage path component detection unit and the leakage path obtained by the leakage path representative value acquisition unit component The representative value of, The ratio of the two is calculated as the fluctuation ratio, and the reciprocal of the fluctuation ratio is A correction unit that uses the above to correct the time-series signal of the detection component appearing in the object detection distance in the received signal, It has.

[0010] One aspect of the received signal processing method of the present invention is: A method for processing a received signal performed in a radar system having a transmitting unit that transmits a wave from a transmitting antenna and a receiving unit that detects an object based on a received signal including a reflected wave received by a receiving antenna, The steps include: extracting a detection component that appears at a specific distance in the received signal as a signal leakage path component from the transmitting unit to the receiving unit; A step of obtaining a representative value of the leak path component based on the time-series signal of the extracted leak path component within a predetermined period, The time-series signal of the leakage path component and the leakage path component The representative value of, The ratio of the two is calculated as the fluctuation ratio, and the reciprocal of the fluctuation ratio is The steps include correcting the time-series signal of the detection component appearing in the object detection distance in the received signal using the above method, Includes. [Effects of the Invention]

[0011] According to the present invention, a radar device and a received signal processing method can be realized that can improve the detection accuracy of objects such as living organisms while suppressing the complexity of the configuration. [Brief explanation of the drawing]

[0012] [Figure 1] Block diagram showing the overall configuration of the radar device according to the embodiment. [Figure 2] Block diagram showing the configuration of the received signal processing unit. [Figure 3] This figure shows the time-series signal that appears at the object detection distance R. [Figure 4] This diagram shows the time-series signals appearing at the object detection distance R and the time-series signals appearing at a specific distance R0. [Figure 5] Flowchart for explaining the operation of the embodiment [Figure 6] This figure shows the results of frequency analysis of received signals I and Q acquired when a radar device was installed inside an unmanned vehicle. Figure 6A shows the analysis results of the complex received signal before correction by the correction unit, and Figure 6B shows the analysis results of the complex received signal after correction by the correction unit. [Figure 7]It is a diagram showing the result of frequency analysis of received signals I and Q obtained when a radar device is installed in someone's vehicle. FIG. 7A is a diagram showing the analysis result of the complex received signal before correction by the correction unit, and FIG. 7B is a diagram showing the analysis result of the complex received signal after correction by the correction unit

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0014] FIG. 1 is a block diagram showing the overall configuration of a radar device 100 according to this embodiment for detecting a living body by a pulse radar method. The radar device 100 has a transmission unit 110 and a reception unit 120.

[0015] The transmission unit 110 inputs the pulse signal generated by the pulse signal generator 111 to the multiplier 112. The multiplier 110 up-converts the pulse signal using the carrier frequency signal output from the local oscillator 113. The up-converted pulse signal is amplified by a power amplifier (PA) 114 and then transmitted as an electromagnetic wave (transmission wave) from the transmission antenna 115.

[0016] The reception unit 120 obtains a reception signal by receiving an electromagnetic wave with the reception antenna 121. The electromagnetic wave includes a reflected wave obtained by reflecting the transmission wave from a detection target (living body). The reception signal output from the reception antenna 121 is input to multipliers 123 and 125 via a low-noise amplifier (LNA) 122.

[0017] Also, a carrier frequency signal from the local oscillator 113 is input to the multiplier 123, and a carrier frequency signal phase-shifted by a π / 2 shifter 124 is input to the multiplier 125. As a result, the reception signal is down-converted by a so-called quadrature down-shifter, and the I component of the reception signal is output from the multiplier 123, and the Q component of the reception signal is output from the multiplier 125.

[0018] The I and Q components of the received signal are input to the received signal processing unit 130 via a low-pass filter (LPF), respectively.

[0019] The received signal processing unit 130 detects a component that appears at a position corresponding to the distance where the reflecting object is located, based on the received signal, and determines whether or not the reflecting object is a living organism based on the temporal variation of the said component.

[0020] Figure 2 is a block diagram showing the configuration of the received signal processing unit 130.

[0021] The received signal is converted from analog to digital by the analog-to-digital converter (A / D) 131 and then stored in the storage unit 132. The stored received signal is extracted as a time-series signal by the leakage path component detection unit 133 and the correction unit 135.

[0022] The leakage path component detection unit 133 extracts the detected component appearing at a specific distance in the received signal as the leakage path component of the signal from the transmitter 110 to the receiver 120. Here, the leakage path component refers to components other than those based on reflected waves from an object (i.e., components other than the reflection path). The leakage path component is, for example, the component that leaks from the transmission line of the transmitter 110 to the transmission line of the receiver 120 in Figure 1. In Figure 1, a virtual coupler L0 is illustrated to simulate leakage in an easy-to-understand manner. Therefore, in reality, it is not necessary to provide a coupler L0. However, if the leakage path component is small, a coupler L0 may be provided. Also, the leakage path component may include, for example, the direct wave transmitted from the transmitting antenna 115 to the receiving antenna 121.

[0023] Leakage route component The leakage path components extracted by the detection unit 133 are output to the leakage path representative value acquisition unit 134 and the correction unit 135. The leakage path representative value acquisition unit 134 outputs the leakage path componentBased on the time-series signals of the leak path components extracted by the detection unit 133 over a predetermined period, a representative value of the leak path component is obtained. The leak path representative value acquisition unit 134 obtains a representative value of the leak path component, for example, by calculating the average value of the time-series signals of the leak path components over a predetermined period. This representative value is output to the correction unit 135.

[0024] The correction unit 135 corrects the time-series signal of the detection component appearing at the object detection distance in the received signal (received IQ signal) using the time-series signal of the leakage path component extracted by the leakage path component detection unit 133 and the representative value of the leakage path obtained by the leakage path representative value acquisition unit 134. Here, the time-series signal of the detection signal appearing at a specific distance is based on the leakage path component, and the time-series signal of the detection signal appearing at the object detection distance is based on the component of the reflected wave from the detected object. The time-series signal of the detection signal appearing at the object detection distance obtained by the correction processing by the correction unit 135 is output to the determination unit 136.

[0025] The determination unit 136 determines the presence or absence of living organisms based on the time-series signal of the detection component appearing in the object detection distance, which has been corrected by the correction unit 135. Specifically, the determination unit 136 determines that living organisms are present if the time-series signal output from the correction unit 135 contains amplitude fluctuations specific to living organisms (for example, fluctuations caused by respiration), and determines that living organisms are not present if the time-series signal output from the correction unit 135 does not contain amplitude fluctuations specific to living organisms.

[0026] Figure 3 shows the time-series signal that appears at the object detection distance R. If the detected object is a living organism and there are no changes in circuit characteristics due to temperature changes, etc., the time-series signal that appears at the object detection distance R will be the amplitude of the reflected pulse superimposed with amplitude fluctuations specific to living organisms caused by respiratory movements, etc.

[0027] Figure 4 shows the time-series signals appearing at the object detection distance R and at a specific distance R0. The time-series signal appearing at the specific distance R0 fluctuates in amplitude depending only on the characteristic variations of each component of the radar device 100; in other words, its amplitude fluctuates due to the leakage path. On the other hand, the time-series signal appearing at the object detection distance R, if the detected object is inanimate, will consist of the amplitude due to the reflection of pulses from the detected object plus the characteristic variations of each component of the radar device 100. If the detected object is a living organism, the time-series signal appearing at the object detection distance R will also have amplitude fluctuations specific to living organisms added to it.

[0028] As can be seen from Figure 4, the specific distance R0 is smaller than the object detection distance R. This is because the leakage path is shorter than the reflection path. In other words, the specific distance R0 can be said to be the smallest distance among the multiple object detection distances R. The specific distance R0 is a fixed distance determined by the arrangement of the circuit and antenna. In other words, the radar device 100 can recognize that the time-series signal appearing at the fixed specific distance R0 is a time-series signal caused by the leakage path by performing transmission and reception several times.

[0029] Next, the operation of the radar device 100 in this embodiment will be explained using Figure 5.

[0030] In step S1, the radar device 100 begins transmitting and receiving pulse waves. Specifically, the radar device 100 transmits periodic pulse waves using the transmitting unit 110 and receives pulse waves reflected from the detected object using the receiving unit 120.

[0031] In the following step S2, the receiving unit 120 performs reception processing. Specifically, each time a pulse wave is transmitted, the receiving unit 120 generates received signals I(r,n) and Q(r,n), and stores these I(r,n) and Q(r,n) in the storage unit 132 as a complex received signal x(r,n) as shown by the following equation.

number

[0032] In the following step S3, the radar device 100 determines whether the number of pulse wave transmissions n has reached N, and repeats steps S2-S3-S2 until it reaches N. As a result, the memory unit 132 stores a short-term time-series signal equivalent to N pulses.

[0033] In the subsequent step S4, the leakage path component detection unit 133 extracts a time-series signal x(R0,n) that appears at a specific distance R0 from the received signals x(r,n) for N transmitted pulses as the time-series signal of the leakage path.

[0034] In the subsequent step S5, the leakage path representative value acquisition unit 134 calculates a representative value of the time-series signal of the leakage path. In this embodiment, the average value Xmean(R0) is calculated as the representative value as shown in the following equation.

number

[0035] In the subsequent step S6, the correction unit 135 calculates the ratio of the time-series signal of the leakage path component to a representative value (in this embodiment, the average value) of the time-series signal of the leakage path as the time-series fdirf(n) of the time-series fluctuation ratio of the radar device 100. Specifically, the correction unit 135 calculates the time-series fdirf(n) using the following formula.

number

[0036] In the subsequent step S7, the correction unit 135 corrects the time series of the received signal x(r,n) for each distance using the reciprocal of the time series of the fluctuation ratio obtained by equation (3), thereby calculating a corrected received signal y(r,n) that suppresses the influence of the time-dependent characteristic fluctuations of the radar device 100. The correction unit 135 calculates the corrected received signal y(r,n) by the following equation.

number

[0037] In the subsequent step S8, the determination unit 136 analyzes the corrected received signal y(r,n) and determines whether or not a living organism is present within the detection range. Specifically, the determination unit 136 determines that a living organism is present if the corrected received signal y(r,n) contains amplitude fluctuations characteristic of living organisms.

[0038] As described above, the radar device 100 of this embodiment includes: a leakage path component detection unit 133 that extracts a detection component appearing at a specific distance R0 in the received signal as a leakage path component of the signal from the transmitting unit 110 to the receiving unit 120; a leakage path representative value acquisition unit 134 that obtains a representative value of the leakage path component based on the time-series signal of the leakage path component within a predetermined period; a correction unit 135 that corrects the time-series signal of the detection component appearing at the object detection distance in the received signal using the time-series signal of the leakage path component and the representative value of the leakage path; and a determination unit 136 that determines the presence or absence of a living organism based on the corrected time-series signal of the detection component appearing at the object detection distance.

[0039] This makes it possible to detect the temperature of each part (circuit) within the radar device 100 in real time and suppress the effects of temporal characteristic fluctuations due to the temperature of the radar device 100 without adding corrections based on the temperature of each part to the received signal. As a result, a radar device 100 can be realized that can improve the accuracy of detecting living organisms while keeping the complexity of the configuration low.

[0040] Here, the transmitted wave that travels through the leakage path to the receiving side has virtually no propagation delay time, so as explained using Figure 4, the distance R0 at which the amplitude of the received signal originating from the leakage path appears is almost zero. Furthermore, since the amplitude originating from the leakage path does not pass through antennas 115 and 121, it is not affected by the outside world and can be said to depend only on the characteristic fluctuations of each part. In this embodiment, focusing on this point, we tracked the fluctuation of the amplitude originating from the leakage path in the time direction to estimate the ratio of the characteristic fluctuations over time due to temperature, etc.

[0041] Figure 6 shows the results of frequency analysis (FFT) of received signals I and Q acquired when the radar device 100 was installed inside an unmanned vehicle. Figure 6A shows the analysis results of the complex received signal x(r,n) before correction by the correction unit 135, and Figure 6B shows the analysis results of the complex received signal x(r,n) after correction by the correction unit 135. More specifically, Figure 6 shows the frequency components included in the amplitude changes of the received signals I and Q in heat map format.

[0042] Figure 7 shows the results of frequency analysis (FFT) of received signals I and Q acquired when the radar device 100 is installed inside a manned vehicle. Figure 7A shows the analysis results of the complex received signal x(r,n) before correction by the correction unit 135, and Figure 7B shows the analysis results of the complex received signal x(r,n) after correction by the correction unit 135. More specifically, Figure 7 shows the frequency components included in the amplitude changes of the received signals I and Q in heat map format.

[0043] In the examples in Figures 6 and 7, the specific distance R0 is approximately 5 cm, where the relatively large frequency component at the left edge of the figure exists.

[0044] As can be seen by comparing Figure 6A and Figure 6B, the influence of temporal characteristic changes due to temperature, etc., is suppressed in Figure 6B. As a result, the accuracy of object detection is improved.

[0045] Furthermore, as can be seen by comparing Figure 7A and Figure 7B, the influence of temporal characteristic fluctuations due to temperature, etc., is suppressed in Figure 7B, so the fluctuation components due to living organisms are clearly visible. This improves the accuracy of detecting living organisms. Specifically, as shown in Figure 7A, the frequency components that appeared in the 100cm to 150cm range before correction processing are suppressed by the correction processing, as can be seen in Figure 7B, and it can be confirmed that the components from 200cm onwards, where people are present, are emphasized and remain.

[0046] As described above, the radar device 100 of this embodiment can be used to detect living organisms such as people with high accuracy. The radar device 100 is used, for example, as a biodetection device to detect whether or not a person is present inside a vehicle. In this case, the transmitting antenna 115 and the receiving antenna 121 are arranged, for example, on the ceiling of the vehicle's interior.

[0047] The embodiments described above are merely examples of how the present invention can be implemented, and the technical scope of the present invention should not be interpreted as being limited by them. In other words, the present invention can be implemented in various forms without departing from its gist or its main features.

[0048] In the above embodiment, we described a case where the average value Xmean of the received signals for each distance is calculated. However, the average value Xmean of the received signals for each distance may also be derived using a low-pass filter. This reduces the computational load and enables real-time correction processing.

[0049] In addition to the embodiments described above, the receiving signal processing unit 130 may also use the temperature detected by a temperature sensor (not shown). Here, since the average value of the leakage signal used in the correction processing of the correction unit 135 is only a representative value for a relatively short period, if the characteristics of the radar device 100 fluctuate over a long period due to temperature, the effects of such long-term fluctuations will not be corrected. Taking this into consideration, in addition to performing correction processing for short-term fluctuations by the correction processing described in the embodiments described above, it is preferable to perform correction to compensate for long-term gain changes of the transmitting unit 110 and the receiving unit 120 based on the circuit temperature measured by a temperature sensor (not shown).

[0050] Here, since short-term characteristic fluctuations are primarily caused by temperature fluctuations, it might seem that a correction based solely on temperature measurement would be sufficient to compensate for short-term characteristic fluctuations as well. However, in reality, correcting for short-term characteristic fluctuations based solely on temperature requires measuring the individual temperature differences of each circuit, thus necessitating the use of numerous temperature sensors. Furthermore, it becomes necessary to use temperature sensors with good time response that can measure short-term temperature changes. This results in increased complexity of the configuration.

[0051] Taking this into consideration, if a correction process for short-term fluctuations is performed using the correction process described in the above embodiment, and a correction is also performed to compensate for long-term gain changes of the transmitter 110 and receiver 120 based on the circuit temperature measured by a temperature sensor (not shown), it becomes possible to correct both short-term and long-term fluctuations while suppressing the complexity of the configuration. Note that the long-term temperature compensation of the transmitter 110 and receiver 120 is a well-known process that has been widely used, so its explanation is omitted here.

[0052] In the embodiments described above, the present invention was applied to a pulse-type radar device 100, but it can also be applied to FM-CW type or PN code phase modulation type (spread spectrum type) radar devices.

[0053] In the above-described embodiment, the case was described in which the received signal processing unit 130 of the radar device 100 has a determination unit 136 that determines the presence or absence of a living organism based on the time-series signal of the detection component appearing in the object detection distance corrected by the correction unit 135. However, the radar device 100 does not have to have a determination unit 136. If it has a determination unit 136, the radar device 100 can function as a living organism detection device, and if it does not have a determination unit 136, the radar device 100 can function as an object detection device. [Industrial applicability]

[0054] The present invention is suitable, for example, as a device for detecting objects such as living organisms. [Explanation of Symbols]

[0055] 100 Radar equipment 110 Transmitter 120 Receiver 130 Received signal processing unit 132 Storage section 133 Leakage Path Component Detection Unit 134 Leakage Path Representative Value Acquisition Unit 135 Correction section 136 Judgment section

Claims

1. A transmitting unit that transmits a wave from a transmitting antenna, A receiving unit that detects an object based on a received signal including reflected waves received by a receiving antenna, A radar system having, The receiving unit is A leakage path component detection unit extracts a detection component that appears at a specific distance in the received signal as a leakage path component of the signal from the transmitting unit to the receiving unit, A representative value acquisition unit obtains a representative value of the leakage path component based on the time-series signal of the leakage path component extracted by the leakage path component detection unit within a predetermined period, A correction unit calculates the ratio of the time-series signal of the leakage path component extracted by the leakage path component detection unit and the representative value of the leakage path component obtained by the leakage path representative value acquisition unit as a fluctuation ratio, and corrects the time-series signal of the detected component appearing in the object detection distance in the received signal using the reciprocal of the fluctuation ratio. Having, Radar equipment.

2. The aforementioned specific distance is the smallest distance among multiple object detection distances. The radar device according to claim 1.

3. The leakage path representative value acquisition unit obtains a representative value of the leakage path component by calculating the average value of the time-series signals of the leakage path component within a predetermined period. The radar device according to claim 1.

4. The leakage path representative value acquisition unit obtains a representative value of the leakage path component by smoothing the time-series signal of the leakage path component within a predetermined period using a low-pass filter. The radar device according to claim 1.

5. In addition to performing short-term corrections on the time-series signal within the predetermined period using the leakage path component detection unit, the leakage path representative value acquisition unit, and the correction unit, Based on the circuit temperature measured by the temperature sensor, a correction is performed to compensate for the long-term gain change of the transmitting and receiving units. A radar device according to any one of claims 1 to 4.

6. The receiving unit further includes a determination unit that determines the presence or absence of a living organism based on the time-series signal of the detection component appearing in the object detection distance corrected by the correction unit. A radar device according to any one of claims 1 to 5.

7. A method for processing a received signal performed in a radar device having a transmitting unit that transmits a wave from a transmitting antenna and a receiving unit that detects an object based on a received signal including a reflected wave received by a receiving antenna, The steps include: extracting a detection component that appears at a specific distance in the received signal as a signal leakage path component from the transmitting unit to the receiving unit; A step of obtaining a representative value of the leak path component based on the time-series signal of the extracted leak path component within a predetermined period, The steps include: calculating the ratio of the time-series signal of the leakage path component to the representative value of the leakage path component as the variation ratio, and correcting the time-series signal of the detection component appearing in the object detection distance in the received signal using the reciprocal of the variation ratio; A method for processing received signals, including the processing of received signals.

8. The further step includes determining the presence or absence of a living organism based on the time-series signal of the detection component appearing in the corrected object detection distance. The method for processing a received signal according to claim 7.

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