KR102381262B1 - Radar system and bio-signal detection method performed thereby - Google Patents

Abstract

The present invention relates to a radar system and a bio-signal detection method performed thereby, the method comprising the steps of: (a) a radar signal processing part removing a fixed target included in a received signal, detecting a peak power distance index of a bio-target using a bio-signal, which is a moving target, and selecting a preset number of neighbor distance indices based on the detected peak power distance index; (b) performing autocorrelation on multi-chirp data corresponding to the selected neighbor distance index to detect the periodicity characteristics of the bio-signal; (c) selecting a plurality of multi-chirp data of the neighbor distance index exceeding a preset reference value from among power values on which the autocorrelation has been performed; (d) summing the multi-chirp data of the selected neighbor distance index to improve the signal-to-noise ratio of the signal, thereby detecting a Doppler frequency signal; (e) performing power correlation on the detected Doppler frequency signal; and (f) detecting a maximal peak from the result of the power correlation and calculating the BPM of the bio-signal using a frequency corresponding to the detected maximal peak. The detection rate and accuracy of a bio-signal including the respiration rate or the heart rate of a human being can be improved using the periodic characteristics of the bio-signal.

Description

RADAR SYSTEM AND BIO-SIGNAL DETECTION METHOD PERFORMED THEREBY

The present invention relates to a radar system and a biosignal detection method performed therein, and more particularly, to a radar system that transmits a radar signal around a target target and detects a biosignal using the received signal, and a biosignal detection method performed therein It relates to a signal detection method.

A radar sensor is a sensing means that transmits radio waves using microwaves and receives some reflection signals reflected from a target to measure distance, speed, and angle information.

Recently, radar sensors have been applied to vehicles to prevent collisions while driving and to support safe driving.

The present applicant disclosed a radar sensor technology in a number of patent documents 1 and 2, such as the following, and has applied for and registered a patent.

Meanwhile, a technology for detecting biosignal information using a radar sensor has recently been developed.

In general, a biosignal measuring device according to the prior art senses a respiration rate or a heart rate using a contact sensor.

However, when it is difficult to use a contact sensor, such as a burn patient or an infant, a technology for detecting a biosignal using a radar sensor is being developed.

That is, as the respiration signal and the heartbeat signal among the biosignals have periodicity, a frequency modulated continuous wave (FMCW), a continuous wave (CW), a pulse, an ultra wide band, Respiratory rate and heart rate are measured by detecting periodic signal characteristics of biological signals using a radar sensor that uses radio waves like UWB) radar.

As described above, the periodic characteristics of the biosignal detected using the radar are measured as a Doppler frequency, and the Doppler frequency components include macro Doppler due to body motion and micro Doppler due to vital movement. (Micro Doppler).

The characteristics of the micro-Doppler by the above-mentioned biological movement are mixed movements of the chest, shoulders, stomach, arms, legs, etc. during respiration.

As described above, the movement of the human body mixed with the Doppler frequency component of the biosignal sensed using the radar is a cause of generating a harmonic, that is, a harmonic frequency.

For this reason, the bio-signal detection technology using the radar sensor according to the prior art has problems in that detection probability of a bio-signal is lowered due to harmonics, and the detection accuracy of the detection result is low.

That is, the biosignal detection technology using a radar sensor according to the prior art was a method of adding a configuration for removing harmonics, but the configuration for removing harmonics is very complicated and it is difficult to remove all harmonics. In addition, when a frequency interference signal is present, there is a problem in that the detection rate is lowered due to false detection.

Republic of Korea Patent Registration No. 10-1513878 (published on April 22, 2015) Republic of Korea Patent Registration No. 10-1505044 (Announced on March 24, 2015)

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems, a radar system capable of detecting a biosignal including a human respiration rate or heart rate using periodic characteristics of a biosignal, and biosignal detection performed therein to provide a way

Another object of the present invention is to provide a radar system capable of improving a biosignal detection rate by detecting micro-Doppler characteristics due to biomotion, and a biosignal detection method performed therein.

Another object of the present invention is to improve the detection accuracy of a biosignal by using the harmonic component characteristics generated by the biomotion signal of various parts and to cancel a frequency interference signal other than harmonics together, and a radar system performed therein To provide a biosignal detection method.

In order to achieve the above object, the radar system according to the present invention includes an antenna unit for transmitting a radar signal (hereinafter referred to as a 'transmission signal') toward a detection target and receiving a received signal reflected from the detection target, the transmission A radar transmitter that generates a signal, a radar receiver that processes data of the received signal received through a reception antenna, and a signal processing that generates a control signal to generate the transmission signal and processes the received signal to detect biosignal information It is characterized in that it includes a processor for the.

In addition, in order to achieve the above object, the biosignal detection method performed in the radar system according to the present invention is (a) the radar signal processing unit removes the fixed target included in the received signal, and collects the biosignal as a moving target. Detecting the peak power distance index of the biological target using the step of selecting a preset number of neighbor distance indexes based on the detected peak power distance index, (b) for multiple chirp data corresponding to the selected neighbor distance index, respectively performing autocorrelation to detect periodic characteristics of the biosignal, (c) selecting a plurality of multi-chirp data having a neighbor distance index exceeding a preset reference value from among the power values for which the autocorrelation has been performed to have excellent periodic characteristics Selecting a biosignal, (d) detecting a Doppler frequency signal by summing the multi-chirp data of the selected neighbor distance index to improve the signal-to-noise ratio of the signal, (e) performing a power correlation on the detected Doppler frequency signal and (f) detecting a maximum peak from the result of performing the power correlation, and calculating the BPM of the biosignal using a frequency corresponding to the detected maximum peak.

As described above, according to the radar system and the biosignal detection method performed in the radar system according to the present invention, only signals having excellent periodic characteristics of the biosignal are selected and synthesized to obtain a signal-to-noise power ratio (SNR) of a Doppler signal. , SNR) to improve the detection rate of the biosignal is obtained.

And, according to the present invention, the periodicity of the living body is maximized by improving the signal-to-noise ratio of the Doppler signal, and even when various harmonic and frequency interference characteristics exist using the power correlation of the Doppler signal, the respiration and heartbeat signals are accurately detected to detect the biological signal. The effect that accuracy can be improved is obtained.

In addition, according to the present invention, since the biosignal can be accurately detected by performing power correlation on the Doppler FFT result of the biosignal and determining the size, number, and interval of the power correlation window, the detection accuracy of the biosignal is improved. It is possible to prevent false detection, and to remove arbitrary frequency interference signals.

1 is a block diagram of a radar system according to a preferred embodiment of the present invention;
2 is a view for explaining a signal processing process of the radar signal processing unit shown in FIG. 1;
3 is a graph showing the peak power distance index;
4 is a conceptual diagram of a multi-chirp data memory;
5 is a diagram showing autocorrelation characteristics for a periodic signal and an aperiodic signal;
6 is a view showing a result of summing multi-chirp data and a result of performing Doppler FFT;
7 is a diagram for explaining the concept of power correlation;
8 is a diagram illustrating a result of detecting a biosignal by performing power correlation through a test;
9 is a flowchart illustrating a biosignal detection method performed in a radar system according to a preferred embodiment of the present invention step by step.

Hereinafter, a radar system and a biosignal detection method performed therein according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a radar system according to a preferred embodiment of the present invention, and FIG. 2 is a view for explaining a signal processing process of the radar signal processing unit shown in FIG. 1 .

In this embodiment, the biosignal may be a signal for detecting respiration of a detection target, a signal for detecting a heartbeat, or a signal for detecting both respiration and heartbeat.

As shown in FIGS. 1 and 2, the radar system 10 according to a preferred embodiment of the present invention transmits a radar signal (hereinafter referred to as a 'transmission signal') toward a detection target and a reception signal reflected from the detection target. The antenna unit 11 for receiving the signal, the radar transmission unit 12 for generating the transmission signal, and the radar reception unit 13 for processing the data of the reception signal received through the reception antenna 22, and control to generate the transmission signal It may include a signal processing processor 14 for generating a signal and processing the received signal to detect biosignal information.

The radar system 10 configured in this way can be applied to various radar devices using various frequency bands, such as 24 GHz, 60 GHz, 77 GHz, and 79 GHz.

The antenna unit 11 may include one or more transmission antennas 21 for transmitting a transmission signal and one or more reception antennas 22 for receiving a reception signal.

The radar transmitter 12 outputs a transmit signal of a desired oscillation frequency according to the control signal of the signal processing processor 14, and the radar receiver 13 amplifies the received signal and processes the data of the received signal. there is.

The signal processing processor 14 includes a radar transmission control unit 41 that controls driving of the radar transmission unit 12, a radar reception control unit 42 that controls driving of the radar reception unit 13, and a communication unit that communicates with an external device. (43) and a radar signal processing unit 44 for detecting biosignal information through signal processing of the detected biosignal.

The radar transmission control unit 41 may generate a control signal to adjust the radar waveform and the transmission power (Tx Power) of the transmission signal.

The radar reception control unit 42 may generate a control signal to adjust a reception gain (Rx Gain) of the received signal and to adjust a band pad filter.

The radar reception control unit 42 may include an analog-to-digital converter (hereinafter referred to as 'ADC') for converting the received signal Rx in the form of an analog signal into a digital signal.

That is, the radar reception control unit 42 includes a plurality of ADCs corresponding to the number of reception antennas 22 , and each ADC may process a reception signal received through each reception antenna 22 by the ADC.

As shown in FIG. 2, the radar signal processing unit 44 performs windowing and range FFT on ADC data converted from a received signal into a digital signal, and removes a moving target (Moving Target Indicator, hereinafter). 'MTI') filter is applied to remove a fixed target, and a Peak Power Range Index of a biological target existing at a specific distance is detected using a radar target detector.

And the radar signal processing unit 44 selects a preset number (N) of neighbor range indexes forward and backward based on the detected peak power distance index.

3 is a graph showing a peak power distance index.

As shown in FIG. 3 , the moving target, that is, the human body movement is formed to be long in the distance direction. Accordingly, a total of eight neighboring distance indexes, for example, four, are selected based on the peak power having the maximum amplitude.

In addition, the radar signal processing unit 44 stores multi-chirp data corresponding to the selected neighbor distance index in an arbitrary memory.

4 is a conceptual diagram of a multi-chirp data memory.

As shown in FIG. 4 , the multi-chirp data includes data of the first chirp (chirp 1) to the #th chirp (chirp #) having different amplitudes and phases for the same distance index.

Therefore, the radar signal processing unit 44 performs autocorrelation on the multi-chirp data stored in an arbitrary memory, and then calculates a power sum for the autocorrelation result to detect the periodicity characteristic of the biosignal. do.

5 is a diagram illustrating autocorrelation characteristics for a periodic signal and an aperiodic signal.

5(a) and 5(b) show the results of autocorrelation of the aperiodic signal, that is, the noise signal and the aperiodic signal, respectively, and FIGS. 5(c) and (d) show the periodic signal, that is, The results of autocorrelation of the biosignal and the biosignal are respectively shown.

That is, it can be confirmed that the result of performing the autocorrelation of the aperiodic signal has no correlation because the magnitude of the normalized autocorrelation power sum value is small as shown in FIG. 5B .

On the other hand, as the biosignal has the characteristics of a periodic signal, the autocorrelation power sum value is large. Accordingly, as shown in FIG. 5(d), in the result of performing the autocorrelation of the periodic signal, it can be confirmed that the correlation exists because the magnitude of the normalized autocorrelation power sum value is large.

The radar signal processing unit 44 sorts values in which the autocorrelation power value is greater than or equal to a preset threshold level in order of magnitude, and then selects the largest value by an arbitrary number (M) to select a biological body having excellent periodic characteristics. select the signal.

Then, the radar signal processing unit 44 sums the multi-chirp data corresponding to the selected M distance indexes.

As described above, according to the present invention, the signal-to-noise ratio of the signals is improved by summing the signals having the greatest periodicity, thereby improving the detection probability of the biosignal.

The radar signal processing unit 44 detects a Doppler frequency signal for a biological signal by performing a Doppler fast Fourier transform (hereinafter, referred to as a 'Doppler FFT') on the summed multi-chirp data.

6 is a diagram illustrating a result of summing multi-chirp data and a result of performing Doppler FFT.

6 (a) shows a graph of the result of summing multiple chirp data of the selected distance index, and in FIG. there is.

In most cases, as shown in FIG. 6A , a harmonic component is included in the Doppler frequency of the biosignal.

As a result of performing Doppler FFT on the summing result of such multi-chirp data, that is, the Doppler frequency of the biosignal, as shown in FIG. 6(b), the biosignal (Fundamental) and the 2nd harmonic , 3rd harmonic, … and other frequency interfering signals.

Therefore, the radar signal processing unit 44 may determine the K-th harmonic characteristic by performing power correlation on the Doppler FFT result, and set the number, size, and interval of the power correlation window of the Doppler signal. It can be applied by changing it according to the characteristics.

For example, FIG. 7 is a diagram illustrating the concept of power correlation, and FIG. 8 is a diagram illustrating a result of detecting a biosignal by performing power correlation through a test.

7(a) shows a graph of a result of performing Doppler FFT, and FIG. 7(b) shows a result of performing power correlation.

The Doppler FFT result shown in FIG. 7A includes a biological signal (Fundamental), a second harmonic (2nd harmonic), and a frequency interference signal (interference).

So, the radar signal processing unit 44 includes a window around the A and B indices corresponding to the biosignal (Fundamental) and the 2nd harmonic in the Doppler FFT result, a slide start point and a slide end point (slide). end) can be set.

Here, the second harmonic has a frequency corresponding to twice the frequency of the biosignal.

Accordingly, the radar signal processing unit 44 sets the number, size, and interval of the power correlation window to include not only the second harmonic but also the nth harmonic corresponding to n times the biosignal according to the characteristics of the harmonics included in the Doppler signal. can be changed

With respect to the Doppler FFT result, the radar signal processing unit 44 may perform power correlation to detect a signal in which a frequency signal is most detected as a biosignal.

That is, when power correlation is performed, as the frequency of the biosignal has the largest value as shown in FIG. 7B, the present invention performs power correlation on the Doppler FFT result to have the largest frequency. Biosignals can be detected.

Figures 8 (a) and (c) illustrate Doppler FFT results obtained by an actual test, respectively, and Figure 8 (b) and (d) show the power for (a) and (c) The results of performing the correlation are illustrated.

When the frequencies of the biosignal and the second and third harmonics sequentially decrease as shown in FIG. A biosignal can be detected by finding a frequency with

And even when the frequency magnitude of the second harmonic is larger than the frequency of the biosignal as shown in FIG. 8(c), the present invention has a maximum magnitude in the power correlation result as shown in FIG. It is possible to detect a biosignal by finding a frequency.

That is, according to the present invention, the biosignal can be accurately detected by performing power correlation on the biosignal including various harmonics, and finding the frequency component having the largest magnitude in the power correlation result.

As described above, the present invention performs power correlation on the Doppler FFT result of the biosignal and determines the size, number, and interval of the power correlation window to accurately detect the biosignal, thereby improving the detection precision of the biosignal and , it can prevent false positives, and can eliminate any frequency interference signal.

Finally, the radar signal processing unit 44 measures a biosignal, that is, a respiration rate or a heart rate by using a frequency corresponding to the maximum value (Max) among the power correlation results.

In this case, the radar signal processing unit 44 may calculate the biosignal frequency [Hz] * 60 [Sec] of the measured Doppler signal to measure the respiration rate or heart rate (Beats Per Minuit, BPM).

As described above, the present invention improves the signal-to-noise ratio of the Doppler signal by selecting and synthesizing a signal with excellent periodicity of the biosignal, and removes harmonics or other frequency interference to accurately detect a biosignal including a human respiration rate or heart rate. can

Next, a biosignal detection method performed in a radar system according to a preferred embodiment of the present invention will be described in detail with reference to FIG. 9 .

9 is a flowchart illustrating a biosignal detection method performed in a radar system according to a preferred embodiment of the present invention step by step.

In step S10 of FIG. 9 , the radar transceiver 12 is a target to be detected, that is, a target to be detected through the transmit antenna 21 according to the control signal of the radar transceiver control unit 41 of the signal processing processor 14 . A signal is transmitted to the vicinity of (hereinafter referred to as a 'biological target'), and a signal reflected to a detection target is received through the reception antenna 22 .

In step S12, the ADC provided in the radar reception control unit 42 converts the analog reception signal into a digital signal.

In step S14, the radar signal processing unit 44 performs windowing and distance FFT on the ADC data, removes the fixed target by applying the MTI filter, and detects the peak power distance index of the biological target existing at a specific distance. Then, the radar signal processing unit 44 selects a preset number (N) of neighbor distance indexes back and forth on the basis of the detected peak power distance index (S16).

In this case, the radar signal processing unit 44 stores multi-chirp data corresponding to the selected neighbor distance index in an arbitrary memory.

In step S18, the radar signal processing unit 44 performs autocorrelation on the multi-chirp data stored in an arbitrary memory, and calculates a power sum for the result of the autocorrelation of the biosignal. A periodic characteristic is detected (S20).

In step S22, the radar signal processing unit 44 checks whether the autocorrelation power value exceeds a preset reference value.

If it is determined in step S22 that the autocorrelation power value is less than or equal to the reference value, the radar signal processing unit 44 proceeds to step S14 and repeats the subsequent process.

On the other hand, if the autocorrelation power value exceeds the reference value as a result of the inspection in step S22, the radar signal processing unit 44 determines the multi-chirp data with high periodicity for a specific distance index and sorts the autocorrelation power values in order of magnitude ( S24), by selecting an arbitrary number (M), biosignals having excellent periodic characteristics are selected (S26).

In step S28, the radar signal processing unit 44 improves the signal-to-noise ratio of the periodic signal by summing all of the multi-chirp data for the selected M neighbor distance indexes since they are signals with high periodicity, thereby improving the biosignal detection rate. there is.

In step S30, the radar signal processing unit 44 performs Doppler FFT on the summed multi-chirp data to detect a Doppler frequency signal for the biosignal.

Therefore, in step S32, the radar signal processing unit 44 checks whether harmonics exist in the detected Doppler frequency signal.

If harmonics exist as a result of the inspection in step S32, the radar signal processing unit 44 performs power correlation on the Doppler FFT result, and at this time, determines the K-th harmonic characteristics to determine the size and number of power correlation windows and The number is determined (S34).

On the other hand, as a result of the inspection in step S32, there is no harmonic or after performing step S34, the radar signal processing unit 44 detects a maximum peak for the Doppler FFT result (S36), and determines the frequency corresponding to the detected maximum peak. By measuring, the BPM of the biosignal is calculated (S38).

Through the above-described process, the present invention can detect a biosignal including a person's respiration rate or heart rate by using the periodic characteristics of the biosignal.

Further, according to the present invention, a biosignal detection rate can be improved by detecting a micro-Doppler characteristic excellent in periodic characteristics due to a biological movement.

In addition, according to the present invention, the detection accuracy of the biosignal can be improved by using the harmonic component characteristics generated by the biomotion signal of various parts, and the interference signal other than the harmonic can also be canceled.

Although the invention made by the present inventors has been described in detail according to the above embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.

The present invention is applied to a radar system that detects a biosignal such as a respiration rate or a heart rate by using the periodic characteristics of the biosignal, and a biosignal detection method technology performed therein.

10: Radar system
11: antenna unit 12: radar transmitter
13: radar receiver 14: processor for signal processing
21: transmit antenna 22: receive antenna
41: radar transmission control unit 42: radar reception control unit
43: communication unit 44: radar signal processing unit

Claims (9)

A biosignal detection method performed in a radar system for transmitting a radar signal toward a detection target and detecting a biological signal by receiving a signal reflected from the detection target, the method comprising:
(a) the radar signal processing unit provided in the signal processing processor of the radar system removes the fixed target included in the received signal, detects the peak power distance index of the biological target using the biological signal as the moving target, and the detected peak selecting a preset number of neighbor distance indexes based on the power distance index;
(b) performing autocorrelation on multiple chirp data corresponding to the selected neighbor distance index, respectively, to detect periodicity characteristics of the biosignal;
(c) selecting a plurality of multi-chirp data having a neighbor distance index exceeding a preset reference value from among the power values on which the autocorrelation is performed to select a biosignal;
(d) detecting the Doppler frequency signal by summing the multi-chirp data of the selected neighbor distance index to improve the signal-to-noise ratio of the signal;
(e) performing power correlation on the detected Doppler frequency signal; and
(f) detecting a maximum peak from the result of performing the power correlation, and calculating the BPM of the biosignal using a frequency corresponding to the detected maximum peak. detection method. According to claim 1, wherein (a) step
(a1) converting the analog reception signal received through the reception antenna in the reception control unit of the radar system into a digital signal using an analog-to-digital converter;
(a2) performing windowing and range FFT on the data converted by the radar signal processing unit, and then removing the fixed target through a moving target removal filter; and
(a3) detecting a peak power distance index of a biological target, and selecting a preset number of neighboring distance indexes based on the detected peak power distance index . According to claim 1, wherein the step (b)
(b1) storing multi-chirp data corresponding to the neighbor distance index selected by the radar signal processing unit;
(b2) performing autocorrelation on each stored multi-chirp data; and
(b3) calculating a power island for the autocorrelation result. The method of claim 3, wherein step (c) is
(c1) comparing the reference value with the power value on which the autocorrelation is performed in the radar signal processing unit;
(c2) sorting the autocorrelation power values exceeding the reference value by size; and
(c3) selecting a plurality of multi-chirp data of a neighbor distance index having a large value from among the sorted values. 5. The method of claim 4, wherein step (d) is
(d1) summing the multi-chirp data of the neighbor distance index selected by the radar signal processing unit; and
(d2) performing Doppler FFT on the summed multi-chirp data to detect a Doppler frequency signal for the biosignal. The method of claim 5, wherein step (e) is
(e1) checking whether harmonics exist in the Doppler frequency signal detected by the radar signal processing unit; and
(e2) when harmonics exist, performing power correlation on a result of performing the Doppler FFT. 7. The method of claim 6,
In step (e2), the radar signal processing unit determines the number, size, and interval of power correlation windows based on harmonic characteristics. 7. The method of claim 6,
In the step (f), the radar signal processing unit detects a frequency signal having a maximum peak in the result of performing the power correlation as a biosignal, and calculates the BPM of the biosignal using the detected frequency of the biosignal. A biosignal detection method performed in a radar system, comprising: In the radar system for detecting a biosignal by the biosignal detection method according to any one of claims 1 to 8,
An antenna unit that transmits a radar signal (hereinafter referred to as a 'transmission signal') toward a detection target and receives a received signal reflected from the detection target;
a radar transmitter that generates the transmission signal;
A radar receiver for processing data of the received signal received through a receiving antenna; and
and a signal processing processor for generating a control signal to generate the transmission signal and signal processing the received signal to detect biosignal information.

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