WO2023163212A1

WO2023163212A1 - Radar device and received signal processing method

Info

Publication number: WO2023163212A1
Application number: PCT/JP2023/007313
Authority: WO
Inventors: 祐吾林
Original assignee: ミネベアミツミ株式会社; 祐吾林
Priority date: 2022-02-28
Filing date: 2023-02-28
Publication date: 2023-08-31
Also published as: JP2023125321A

Abstract

Provided are a radar device and a received signal processing method with which it is possible to improve the accuracy of detection of an object such as an organism, while minimizing increases in configuration complexity. This radar device (100) comprises a transmission unit (110) and a reception unit (120). The reception unit (120) comprises: a leak path component detection unit (133) that extracts, as a leak path component in a signal from the transmission unit to the reception unit, a detection component appearing at a specific distance in a received signal; a leak path representative value acquisition unit (134) that acquires a representative value of the leak path component on the basis of time-series signals of the extracted leak path component during a prescribed period; and a correction unit (135) that uses the time-series signals of the leak path component and the representative value of the leak path to correct time-series signals of a detection component appearing at an object detection distance in the received signal.

Description

Radar device and received signal processing method

The present invention relates to a radar device and a received signal processing method that can detect the presence of a living body such as a person.

Conventionally, there have been widely proposed radar devices that detect the presence or absence of living organisms by capturing weak changes in radio wave propagation associated with body movements unique to living organisms (for example, body movements due to breathing) (see, for example, Patent Document 1). .

This type of radar device transmits a transmission signal obtained by up-converting a pulse signal, and receives the signal reflected by the detection target as a reception signal. Amplitude changes appear in the received signal that indicate the presence of the object to be detected. In particular, when the object to be detected is a living organism, amplitude changes characteristic of living organisms, such as respiration, appear in the received signal. Presence is detected.

JP 2020-024185 A

By the way, in this type of radar device, when the temperature of the amplifier and local oscillator that make up the radar device changes, the gain of the amplifier and the phase of the local oscillator change. In a radar system, when such a gain change or phase change occurs while a living body is being detected, the detected object looks as if it were a living organism, even though the object being detected is inanimate. There was a risk of judging that the object was a living thing because the object would be recognized as slightly moving.

This problem is likely to manifest itself remarkably immediately after startup, when the temperature of each part of the radar device changes suddenly and the characteristics of each part of the radar device change relatively greatly. One possible method of solving this problem is to detect the temperature of each section (circuit) in the radar apparatus in real time and add correction to the received signal based on the temperature of each section.

However, if such a method is adopted, it is necessary to perform different temperature corrections for each part (circuit) having different temperature characteristics, resulting in a complicated configuration.

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 an object such as a living body while suppressing complication of the configuration.

One aspect of the radar device of the present invention is
a transmitter that transmits a transmission wave from a transmission antenna;
a receiving unit that detects an object based on a received signal including a reflected wave received by a receiving antenna;
A radar device having
The receiving unit
a leaky path component detector that extracts a detected component appearing at a specific distance in the received signal as a leaky path component of the signal from the transmitter to the receiver;
a leakage path representative value obtaining unit for obtaining a representative value of the leakage path component based on the time-series signal within a predetermined period of the leakage path component extracted by the leakage path detection unit;
detecting an object in the received signal using 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 obtained by the leakage path representative value acquisition unit; a correction unit that corrects the time-series signal of the detection component that appears in the distance;
have

One aspect of the received signal processing method of the present invention is
A received signal processing method performed by the receiving unit in a radar device having a transmitting unit that transmits a transmission wave from a transmitting antenna and a receiving unit that detects an object based on a received signal including a reflected wave received by the receiving antenna There is
a step of extracting a detected component appearing at a specific distance in the received signal as a leakage path component of the signal from the transmitter to the receiver;
obtaining a representative value of the leaky path component based on the extracted time-series signal of the leaky path component within a predetermined period;
correcting the time-series signal of the detection component appearing in 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;
including.

According to the present invention, it is possible to realize a radar device and a received signal processing method that can improve the detection accuracy of an object such as a living body while suppressing complication of the configuration.

FIG. 1 is a block diagram showing the overall configuration of a radar device according to an embodiment. FIG. 2 is a block diagram showing the configuration of the received signal processing section. FIG. 3 is a diagram showing how time-series signals appear at the object detection distance R. FIG. FIG. 4 is a diagram showing a time-series signal appearing at the object detection distance R and a time-series signal appearing at the specific distance R0. FIG. 5 is a flowchart for explaining the operation of the embodiment. 6A and 6B are diagrams showing the results of frequency analysis of the received signals I and Q obtained when the radar device is installed in an unmanned vehicle. FIG. 6A is the analysis result of the complex received signal before correction by the correction unit. , and FIG. 6B is a diagram showing an analysis result of the complex received signal corrected by the correcting unit. 7A and 7B are diagrams showing the results of frequency analysis of received signals I and Q obtained when the radar device is installed in a manned vehicle, and FIG. 7A is the analysis result of the complex received signal before correction by the corrector. , and FIG. 7B is a diagram showing an analysis result of the complex received signal corrected by the correcting unit.

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

FIG. 1 is a block diagram showing the overall configuration of a radar device 100 of this embodiment that detects a living body by the pulse radar system. The radar device 100 has a transmitter 110 and a receiver 120 .

The transmission unit 110 inputs the pulse signal generated by the pulse signal generator 111 to the multiplier 112 . Multiplier 110 up-converts the pulse signal using the carrier frequency signal output from 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 a transmission antenna 115 .

The receiving unit 120 obtains a received signal by receiving electromagnetic waves with the receiving antenna 121 . Electromagnetic waves include reflected waves of transmitted waves reflected by a detection target (living body). A received signal output from a receiving antenna 121 is input to

multipliers

123 and 125 via a low noise amplifier (LNA) 122 .

A carrier frequency signal from the local oscillator 113 is input to the multiplier 123 , and a carrier frequency signal phase-shifted by the π/2 shifter 124 is input to the multiplier 125 . As a result, the received signal is down-converted by a so-called quadrature downshifter, multiplier 123 outputs the I component of the received signal, and multiplier 125 outputs the Q component of the received signal.

The I component and Q component of the received signal are each input to the received signal processing section 130 via a low-pass filter (LPF).

The received signal processing unit 130 detects a component appearing at a position corresponding to the distance of the reflected object based on the received signal, and determines whether the reflected object is a living body based on the variation of the component in the time direction. judge.

FIG. 2 is a block diagram showing the configuration of the reception signal processing section 130. As shown in FIG. Received signal processing section 130 has analog-to-digital conversion section (A/D) 131 , storage section 132 , leakage path component detection section 133 , leakage path representative value acquisition section 134 , correction section 135 and determination section 136 . The storage unit 132 is composed of a memory device. The leakage path component detection unit 133, the leakage path representative value acquisition unit 134, the correction unit 135, and the determination unit 136 are configured by an arithmetic processing device such as a CPU (Central Processing Unit). The arithmetic processing unit is read from an auxiliary storage device (not shown), which is a non-volatile memory such as a flash memory or a hard disk, and stored in a main storage device (not shown), such as a RAM (Random Access Memory). , the functions described later in the leakage path component detection unit 133, the leakage path representative value acquisition unit 134, the correction unit 135, and the determination unit 136 are realized.

The received signal is stored in the storage section 132 after being analog-to-digital converted by the analog-to-digital conversion section (A/D) 131 . The stored received signal is extracted as a time-series signal by leakage path component detection section 133 and correction section 135 .

The leaky path component detector 133 extracts a detected component appearing at a specific distance in the received signal as a leaky path component of the signal from the transmitter 110 to the receiver 120 . Here, the leaky path component means a component other than the component based on the reflected wave from the object (that is, other than the reflected path). A leakage path component is a component that leaks from the line of the transmitter 110 in FIG. 1 to the line of the receiver 120, for example. FIG. 1 illustrates a virtual coupler L0 to easily simulate leakage. Therefore, the coupler L0 may not actually be provided. However, in the case of a configuration with a small leakage path component, the coupler L0 may be provided. Leaky path components may also include direct waves propagating from transmit antenna 115 to receive antenna 121, for example.

The leakage path component extracted by the leakage path detection unit 133 is output to the leakage path representative value acquisition unit 134 and the correction unit 135 . The leakage path representative value acquisition unit 134 acquires a representative value of the leakage path component based on the time-series signal within a predetermined period of the leakage path component extracted by the leakage path detection unit 133 . The leakage path representative value obtaining unit 134 obtains the representative value of the leakage path component by, for example, calculating the average value of the time-series signal within a predetermined period of the leakage path component. This representative value is output to the correction unit 135 .

The correction unit 135 uses 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 to obtain the received signal (reception The time-series signal of the detection component appearing in the object detection distance in the IQ signal) is corrected. Here, the time-series signal of the detection signal appearing at the 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 reflected wave component from the detection object. A time-series signal of the detection signal appearing in the object detection distance obtained by the correction processing by the correction unit 135 is output to the determination unit 136 .

The determination unit 136 determines the presence or absence of a living body based on the time-series signal of the detection component appearing in the object detection distance corrected by the correction unit 135 . Specifically, the determining unit 136 determines that a living thing exists when the time-series signal output from the correcting unit 135 includes an amplitude variation peculiar to a living thing (for example, a variation caused by respiration). If the time-series signal output from 135 does not have amplitude fluctuations peculiar to organisms, it is determined that organisms do not exist.

FIG. 3 is a diagram showing how time-series signals appear at the object detection distance R. If the object to be detected is a living body and there is no fluctuation in the circuit characteristics due to temperature changes, etc., the time-series signal appearing in the object detection distance R will include amplitude fluctuations peculiar to living organisms due to respiratory movements, etc., in addition to the amplitude of the reflected pulse. are superimposed.

FIG. 4 is a diagram showing the state of the time-series signal appearing at the object detection distance R and the time-series signal appearing at the specific distance R0. The amplitude of the time-series signal appearing at the specific distance R0 varies depending only on the characteristic variation of each part constituting the radar device 100. In other words, the amplitude varies due to the leakage path. . On the other hand, if the detected object is an inanimate object, the time-series signal appearing at the object detection distance R is the amplitude due to the reflection of the pulse from the detected object plus the characteristic fluctuations of the parts constituting the radar device 100. becomes. If the object to be detected is a living organism, the time-series signal appearing at the object detection distance R will further include amplitude fluctuations specific to the living organism.

As can be seen from FIG. 4, the specific distance R0 is smaller than the object detection distance R. This is because the leaky path is shorter than the reflected path. In other words, it can be said that the specific distance R0 is the smallest distance among the plurality of object detection distances R. The specified distance R0 is a fixed distance determined by the layout 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 the time-series signal caused by the leakage path by performing transmission and reception several times.

Next, the operation of the radar device 100 of this embodiment will be described using FIG.

The radar device 100 starts transmitting and receiving pulse waves in step S1. Specifically, in the radar device 100, the transmission section 110 transmits periodic pulse waves, and the reception section 120 receives pulse waves reflected from the detected object.

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

However, the argument r in equation (1) indicates the distance from the radar device 100, and the argument n indicates the n-th pulse wave.

In the following step S3, the radar device 100 determines whether or not the pulse wave transmission count n has reached N, and repeats steps S2-S3-S2 until it reaches N. As a result, the storage unit 132 stores N pulses of short-term time-series signals.

In the following step S4, the leaky path component detector 133 detects the time-series signal x(R0,n) appearing at the specific distance R0 from the received signals x(r,n) for N transmission pulses as the leaky path time. Extract as a series signal.

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

In subsequent step S6, the correcting unit 135 calculates the ratio of the time-series signal of the leak path component to the representative value (average value in the case of the present embodiment) of the time-series signal of the leak path, based on the temporal fluctuation of the radar device 100. It is calculated as the time series fdirf(n) of the ratio. Specifically, the correction unit 135 calculates the time series fdirf(n) using the following equation.

In subsequent step S7, the correction unit 135 corrects the time series for each distance of the received signal x(r, n) using the reciprocal of the time series of the fluctuation ratio obtained by the equation (3), so that the radar device A corrected received signal y(r, n) that suppresses the influence of characteristic variation over time of 100 is calculated. The corrector 135 calculates the corrected received signal y(r,n) using the following equation.

In subsequent step S8, the determination unit 136 analyzes the corrected received signal y(r, n) and determines whether or not a living body exists within the detection range. Specifically, the determination unit 136 determines that a living body exists if the corrected received signal y(r, n) includes an amplitude variation peculiar to a living body.

As described above, the radar device 100 of the present embodiment performs leaky path component detection for extracting the detection component appearing at the specific distance R0 in the received signal as the leaky path component of the signal from the transmitter 110 to the receiver 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 time series signal of the leakage path component; and a correction unit 135 that corrects the time-series signal of the detection component appearing in the object detection distance in the received signal using . and a determination unit 136 for determining.

As a result, the temperature of each part (circuit) in the radar device 100 is detected in real time, and the influence of the characteristic fluctuation over time due to the temperature of the radar device 100 or the like can be reduced without applying correction to the received signal based on the temperature of each part. As a result, it is possible to realize the radar device 100 that can improve the living body detection accuracy while suppressing the complication of the configuration.

Here, since the transmission wave that propagates through the leaky path and reaches the receiving side has substantially no delay time for propagation, as described with reference to FIG. R0 is nearly zero. In addition, since the amplitude derived from the leakage path does not pass through the

antennas

115 and 121, it is not affected by the external world, so it can be said that it depends only on characteristic fluctuations of each part. Focusing on this point, the present embodiment estimates the ratio of temporal characteristic fluctuations due to temperature or the like by following the amplitude fluctuations originating from the leakage path in the time direction.

FIG. 6 is a diagram showing the results of frequency analysis (FFT) of received signals I and Q obtained when the radar device 100 is installed in an unmanned vehicle. FIG. FIG. 6B shows the analysis result of the complex received signal x(r, n) after correction by the correction unit 135. FIG. More specifically, FIG. 6 shows the frequency components contained in the amplitude changes of the received signals I and Q in the form of a heat map.

FIG. 7 is a diagram showing the result of frequency analysis (FFT) of received signals I and Q obtained when the radar device 100 is installed in a manned vehicle. FIG. FIG. 7B shows the analysis result of the complex received signal x(r, n) after correction by the corrector 135. FIG. More specifically, FIG. 7 shows the frequency components contained in the amplitude variations of the received signals I and Q in the form of a heat map.

　In the examples of FIGS. 6 and 7, the specific distance R0 is a distance of about 5 cm where a relatively large frequency component exists at the left end of the figure.

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

Also, as can be seen by comparing FIG. 7A and FIG. 7B, in FIG. 7B, since the influence of temporal characteristic fluctuation due to temperature or the like is suppressed, the fluctuation component due to the living body clearly appears. This improves the detection accuracy of the living body. Specifically, as shown in FIG. 7A, the frequency components appearing at 100 cm to 150 cm before the correction process are suppressed by the correction process as shown in FIG. 7B. It can be confirmed that the subsequent components are left in an emphasized form.

In this way, by using the radar device 100 of the present embodiment, living things such as humans can be detected with high accuracy. The radar device 100 is used, for example, as a living body detection device that detects whether or not a person is present in the vehicle. In this case, the transmitting antenna 115 and the receiving antenna 121 are arranged, for example, on the ceiling of the passenger compartment of the vehicle.

The above-described embodiment merely shows an example of implementation of the present invention, and the technical scope of the present invention should not be construed to be limited by these. That is, the present invention can be embodied in various forms without departing from its spirit or essential characteristics.

In the above embodiment, the case of calculating the average value Xmean of the received signal for each distance was described, but the average value Xmean of the received signal for each distance may be derived using a low-pass filter. By doing so, in addition to lightening the arithmetic processing, real-time correction processing can be realized.

In addition to the above embodiments, the received signal processing unit 130 may use the temperature detected by a temperature sensor (not shown). Here, since the average value of the leakage signal used in the correction process of the correction unit 135 is only a representative value for a relatively short period of time, if the characteristics of the radar device 100 fluctuate over a long period of time due to temperature, the long-term There will be no correction for the effects of volatility. In consideration of this, in addition to performing correction processing for short-term fluctuations by the correction processing described in the above embodiments, the transmission unit 110 and the reception unit 110 and the reception unit 110 are corrected based on the circuit temperature measured by a temperature sensor (not shown). Corrections are preferably made to compensate for long-term gain changes in section 120 .

Here, short-term characteristic fluctuations are also mainly caused by temperature fluctuations, so simply thinking, it seems that short-term characteristic fluctuations can also be corrected by performing correction based only on temperature measurement. However, in reality, in order to compensate for short-term characteristic fluctuations based only on temperature, it is necessary to measure the individual temperature differences of each circuit, so it is necessary to prepare a large number of temperature sensors. There is Furthermore, it is necessary to use a temperature sensor with good time response that can measure temperature changes in a short period of time. As a result, the configuration becomes complicated.

In consideration of this, correction processing for short-term fluctuations is performed by the correction processing described in the above embodiments, and the temperature of the transmission unit 110 and the reception unit 120 is corrected based on the circuit temperature measured by a temperature sensor (not shown). By performing correction that compensates for long-term gain changes, short-term fluctuations and long-term fluctuations can be corrected while suppressing complication of the configuration. Note that the long-term temperature compensation of the transmitter 110 and the receiver 120 is a well-known process that has been widely performed in the past, and therefore will not be described here.

In the above embodiment, the case where the present invention is applied to the pulse-type radar device 100 has been described, but it can also be applied to radar devices of the FM-CW method and the PN code phase modulation method (spread spectrum method).

In the above-described embodiment, the reception signal processing unit 130 of the radar device 100 has the determination unit 136 that determines the presence or absence of a living body based on the time-series signal of the detection component that appears in the object detection distance corrected by the correction unit 135. Although the case has been described, the radar device 100 does not have to have the determination unit 136 . If the determination unit 136 is included, the radar device 100 can function as a living body detection device, and if the determination unit 136 is not included, the radar device 100 can function as an object detection device.

This application claims priority based on Japanese Patent Application No. 2022-029342 filed on February 28, 2022. All contents described in these application specifications and drawings are incorporated herein by reference.

The present invention is suitable as a device for detecting objects such as living things.

100 radar device 110 transmitter 120 receiver 130 received signal processor 132 storage 133 leak path component detector 134 leak path representative value acquirer 135 corrector 136 determiner

Claims

a transmitter that transmits a transmission wave from a transmission antenna;
a receiving unit that detects an object based on a received signal including a reflected wave received by a receiving antenna;
A radar device having
The receiving unit
a leaky path component detector that extracts a detected component appearing at a specific distance in the received signal as a leaky path component of the signal from the transmitter to the receiver;
a leakage path representative value obtaining unit for obtaining a representative value of the leakage path component based on the time-series signal within a predetermined period of the leakage path component extracted by the leakage path detection unit;
detecting an object in the received signal using 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 obtained by the leakage path representative value acquisition unit; a correction unit that corrects the time-series signal of the detection component that appears in the distance;
having
radar equipment.
The specific distance is the smallest distance among a plurality of object detection distances,
Radar device according to claim 1 .
The leakage representative value obtaining unit obtains a representative value of the leakage path component by calculating an average value of time-series signals within a predetermined period of the leakage path component,
Radar device according to claim 1
The leakage representative value acquisition unit acquires a representative value of the leakage path component by smoothing a time-series signal of the leakage path component within a predetermined period with a low-pass filter.
Radar device according to claim 1
In addition to performing short-term correction on the time-series signal within the predetermined period by the leakage path component detection unit, the leakage path representative value acquisition unit, and the correction unit,
Correction to compensate for long-term gain changes of the transmitter and the receiver based on the circuit temperature measured by the temperature sensor;
Radar device according to any one of claims 1 to 4.
The receiving unit further includes a determination unit that determines the presence or absence of a living body based on the time-series signal of the detection component appearing in the object detection distance corrected by the correction unit.
Radar device according to any one of claims 1 to 5.
A received signal processing method performed by the receiving unit in a radar device having a transmitting unit that transmits a transmission wave from a transmitting antenna and a receiving unit that detects an object based on a received signal including a reflected wave received by the receiving antenna There is
a step of extracting a detected component appearing at a specific distance in the received signal as a leakage path component of the signal from the transmitter to the receiver;
obtaining a representative value of the leaky path component based on the extracted time-series signal of the leaky path component within a predetermined period;
correcting the time-series signal of the detection component appearing in 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;
A received signal processing method, comprising:
determining the presence or absence of a living body based on the time-series signal of the detection component appearing in the corrected object detection distance;
8. The received signal processing method according to claim 7.