Respiration rate and heart rate measuring method based on millimeter wave radar amplitude phase information fusion

Abstract

The invention provides a respiration rate and heart rate measuring method based on millimeter-wave radar amplitude and phase information fusion, and relates to the technical field of millimeter-wave radar signal processing.The method comprises the steps that amplitude information data and phase information data of millimeter-wave radar human body echo signals are obtained; preprocessing the phase information data and the amplitude information data to respectively obtain normalized phase information data and normalized amplitude information data; performing cancellation processing on the normalized phase information data and the normalized amplitude information data to obtain heartbeat signals; performing weighted summation on the normalized phase information data and the normalized amplitude information data to obtain a respiratory signal; and filtering the heartbeat signal and the respiration signal, and analyzing the time interval of adjacent maximum value points to respectively obtain a real-time heart rate and a real-time respiration rate so as to complete the measurement of the respiration rate and the heart rate. According to the invention, the problems of insufficient accuracy, stability and anti-interference capability of heart rate and respiratory rate measurement are solved.

Description

TECHNICAL FIELD

[0001] The present specification relates to the technical field of millimeter wave radar signal processing, in particular to a respiration rate and heart rate measurement method based on millimeter wave radar amplitude and phase information fusion. BACKGROUND

[0002] Human heart rate and respiration rate are one of the most basic and important vital signs, which are widely used in medical monitoring, health assessment, sleep monitoring, smart home, disaster rescue and other fields. At present, the measurement methods of heart rate and respiration rate mainly include two categories: contact type and non-contact type.

[0003] The contact type measurement method mainly includes electrocardiogram (ECG), photoplethysmography (PPG) and respiratory belt, etc. These methods usually require the sensor to be directly attached to the surface of the human body skin, and the heart rate and respiration rate information is obtained by measuring the electrical signal or pressure change. For example, ECG collects the heart electrical activity signal through electrodes, which can accurately measure the heart rate, but requires electrodes to be pasted on the human body at specific parts, which is inconvenient to use, and long-term wearing may cause skin discomfort. PPG measures blood volume changes through optical sensors, which is commonly used in wearable devices, but is easily disturbed by environmental light, skin color and motion artifacts. The respiratory belt detects the respiration rate by measuring the pressure change caused by the expansion and contraction of the chest and abdomen, but it is not comfortable to wear and may affect the natural breathing state. Although the contact type measurement method has high accuracy, its inherent limitations (such as wearing discomfort, inconvenience to use, and susceptibility to motion interference) limit its application in certain scenarios, especially in scenarios that require long-term and unobtrusive monitoring.

[0004] The existing human vital sign measurement method based on millimeter wave radar only uses the phase information of millimeter wave radar echo for measurement. After phase unwrapping and differential processing, the heart beat and respiration information are extracted through frequency domain filtering. Although the phase is sensitive to small movements, the phase unwrapping and noise interference problems are more prominent, and the signal processing algorithm requires higher. In addition, the chest wall movement caused by heart beat is significantly weaker than the movement caused by respiration, and the amplitude of the two movements differs by two orders of magnitude. The heart beat feature contained in the phase is easily covered by the respiration feature, resulting in failure to extract the heart beat signal. SUMMARY

[0005] In view of the above problems in the prior art, the respiration rate and heart rate measurement method based on millimeter wave radar amplitude and phase information fusion provided by the present application solves the problems of insufficient accuracy, stability and anti-interference ability of heart rate and respiration rate measurement.

[0006] In order to achieve the above-mentioned purpose of the application, the technical scheme adopted by the present application is as follows: a respiration rate and heart rate measurement method based on millimeter wave radar amplitude and phase information fusion, comprising: S1: obtaining amplitude information data and phase information data of the human body echo signal of the millimeter wave radar; S2: preprocessing the phase information data and the amplitude information data to obtain normalized phase information data and normalized amplitude information data respectively; S3: canceling the normalized phase information data and the normalized amplitude information data to obtain a heartbeat signal; S4: weighted sum of the normalized phase information data and the normalized amplitude information data to obtain a respiration signal; S5: filtering the heartbeat signal and the respiration signal, and analyzing the time interval of adjacent maximum value points to obtain real-time heart rate and real-time respiration rate respectively, and completing the measurement of respiration rate and heart rate.

[0007] Further, the S1 comprises: Performing maximum value search on the millimeter wave radar echo signal after completing the distance dimension pulse compression processing, extracting the amplitude information and the phase information at the peak value as the amplitude information data and the phase information data respectively.

[0008] Further, the expression of the amplitude information data and the phase information data is: ; Wherein, represents the human body echo baseband signal, represents the serial number of the peak value data, represents the amplitude of the n th peak value data, that is, the amplitude information data, represents the natural constant in exponential form, represents the imaginary unit, represents the phase of the n th peak value data, that is, the phase information data.

[0009] Further, the S2 comprises: Performing unwrapping processing on the phase information data to obtain unwrapped phase information data; Using the radar echo signal model, transforming the amplitude information data so that the amplitude change characteristic is linearly proportional to the respiration and heartbeat change to obtain changed amplitude information data; Performing mean removal processing on the unwrapped phase information data and the changed amplitude information data to obtain mean-removed phase information data and mean-removed amplitude information data respectively; Setting a band-pass filter with a typical human respiration rate and heart rate as a reference, filtering the mean-removed phase information data and the mean-removed amplitude information data to obtain filtered phase information data and filtered amplitude information data respectively; The filtered phase information data and the filtered amplitude information data are normalized respectively to obtain normalized phase information data and normalized amplitude information data.

[0010] Further, the expression of the phase information data of the unwrapping processing is: ; wherein, represents the phase information data of the unwrapping processing, represents the serial number of the peak data, represents the phase of the first peak data. n

[0011] Further, the expression of the changed amplitude information data is: ; ; ; ; ; ; wherein, represents the changed amplitude information data, represents the serial number of the peak data, represents a proportionality coefficient, represents the distance between the millimeter wave radar and the human body in the resting state, represents the distance change caused by breathing, represents the noise contained in the transformed amplitude, represents the amplitude signal data, represents the distance between the millimeter wave radar and the human body, represents the phase information data of the unwrapping processing, represents a proportionality coefficient, represents the noise contained in the phase, represents the distance change caused by heartbeat.

[0012] Further, the expression of the normalized phase information data is: ; wherein, represents the normalized phase information data, represents the serial number of the peak data, represents the distance change caused by breathing, represents the noise contained in the amplitude data after the normalization processing; The expression of the normalized amplitude information data is:​ ; wherein, represents normalized amplitude information data, represents distance change caused by heart beat, represents noise contained in phase data after normalization.

[0013] Further, the expression of the heart beat signal is: ; wherein, represents heart beat signal, represents serial number of peak value data, represents normalized amplitude information data, represents normalized phase information data, represents distance change caused by heart beat, represents noise contained in phase data after normalization, represents noise contained in amplitude data after normalization; The expression of the respiration signal is: ; ; wherein, represents respiration signal, represents weighting coefficient of amplitude data, represents weighting coefficient of phase data, represents distance change caused by respiration.

[0014] Further, the expression of the real-time heart rate is: ; wherein, represents real-time heart rate, represents time point at which the first maximum value point of human heart beat signal is located in heart beat data; i The expression of the real-time respiration rate is: ; wherein, represents real-time respiration rate, represents time point at which the first maximum value point of human respiration signal is located in respiration data. i

[0015] ​​The present application has the beneficial effects that the present application provides a respiration rate and heart rate measurement method based on millimeter wave radar amplitude and phase information fusion, pre-processes amplitude information data and phase information data to obtain normalized phase information data and normalized amplitude information data, cancels the normalized phase information data and the normalized amplitude information data to obtain a heartbeat signal, and performs weighted summation on the normalized phase information data and the normalized amplitude information data to obtain a breathing signal, and analyzes to obtain real-time heart rate and real-time respiration rate. By comprehensively utilizing the amplitude and phase information of the millimeter wave radar echo, the complementary advantages of the two are fully utilized, the influence of the respiration harmonic on the heartbeat information measurement is effectively reduced, and the precision, stability and anti-interference ability of the heart rate and respiration rate measurement are improved. BRIEF DESCRIPTION OF DRAWINGS

[0016] The present application will be further illustrated in the form of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting, and in these embodiments, the same numbers represent the same structures, wherein: Figure 1 is an exemplary flow chart of a respiration rate and heart rate measurement method based on millimeter wave radar amplitude and phase information fusion according to some embodiments of the present application; Figure 2 is an exemplary schematic diagram of amplitude information data of a human body echo signal according to some embodiments of the present application; Figure 3 is an exemplary schematic diagram of phase information data of a human body echo signal according to some embodiments of the present application; Figure 4 is an exemplary schematic diagram of phase data after unwrapping processing according to some embodiments of the present application; Figure 5 is an exemplary schematic diagram of transformed amplitude data according to some embodiments of the present application; Figure 6 is an exemplary schematic diagram of normalized amplitude data and phase data after normalization processing according to some embodiments of the present application; Figure 7 is an exemplary schematic diagram of a filtered heartbeat signal according to some embodiments of the present application; Figure 8 is an exemplary schematic diagram of a filtered breathing signal according to some embodiments of the present application. DETAILED DESCRIPTION

[0017] The specific embodiments of the present application are described below to enable those skilled in the art to understand the present application, but it should be clear that the present application is not limited to the scope of the specific embodiments, and for those skilled in the art, any changes that are obvious within the spirit and scope of the present application defined and determined by the appended claims are included in the protection of the present application.

[0018] Embodiments Figure 1 is an exemplary flowchart of a respiration rate and heart rate measurement method based on millimeter wave radar amplitude and phase information fusion according to some embodiments of the present specification. As shown in Figure 1 , the flow includes the following steps. In some embodiments, the flow can be executed by a processor.

[0019] S1: Obtain amplitude information data and phase information data of the millimeter wave radar human body echo signal.

[0020] The amplitude information data is the amplitude of the peak data in the human body echo baseband signal.

[0021] The phase information data is the phase of the peak data in the human body echo baseband signal.

[0022] In some embodiments, the processor can perform maximum value search on the millimeter wave radar echo signal after the distance dimension pulse compression processing is completed, extract the amplitude information and phase information at the peak as the amplitude information data and phase information data, respectively.

[0023] As shown in Figure 2 is the amplitude information of the extracted human body echo signal, and as shown in Figure 3 is the phase information of the extracted human body echo signal, the data duration is about 60 seconds, and the sampling time interval is 0.11 seconds.

[0024] In some embodiments, the expression of the amplitude information data and the phase information data can be: ; Wherein, represents the human body echo baseband signal, represents the serial number of the peak data, represents the amplitude of the n th peak data, i.e. the amplitude information data, represents the natural constant in exponential form, represents the imaginary unit, represents the phase of the n th peak data, i.e. the phase information data.

[0025] S2: preprocessing the phase information data and the amplitude information data to obtain normalized phase information data and normalized amplitude information data respectively.

[0026] In some embodiments, the processor can perform an unwrapping process on the phase information data to obtain unwrapped phase information data. The amplitude information data is transformed using a radar echo signal model, so that the amplitude change characteristic is linearly proportional to the respiratory and heartbeat change, to obtain changed amplitude information data. The unwrapped phase information data and the changed amplitude information data are subjected to mean removal processing to obtain mean-removed phase information data and mean-removed amplitude information data respectively. A band-pass filter is set with reference to a typical human respiratory rate and heart rate, and the mean-removed phase information data and the mean-removed amplitude information data are filtered to obtain filtered phase information data and filtered amplitude information data respectively. The filtered phase information data and the filtered amplitude information data are subjected to normalization processing to obtain normalized phase information data and normalized amplitude information data respectively.

[0027] In some embodiments, the unwrapped phase information data can be as shown in formula (1). Figure 4

[0028] In some embodiments, the expression of the unwrapped phase information data can be: ; wherein, represents the unwrapped phase information data, represents the serial number of the peak data, represents the phase of the i-th peak data. n

[0029] The sensitivity of the millimeter wave radar echo phase to distance change is much higher than the sensitivity of the amplitude to distance change, and the distance change caused by respiration is two orders of magnitude higher than the distance change caused by heartbeat. Therefore, the heartbeat information contained in the amplitude data is basically covered by noise, and the change characteristic is only related to the distance change caused by respiration.

[0030] In some embodiments, the changed amplitude information data can be as shown in formula (2). Figure 5

[0031] In some embodiments, the expression of the changed amplitude information data can be: ; ; ; ​​​ ; ; ; wherein, represents the changed amplitude information data, represents the sequence number of the peak data, represents the proportionality coefficient, represents the distance between the human body in the resting state and the millimeter wave radar, represents the distance change caused by breathing, represents the noise contained in the transformed amplitude, represents the amplitude signal data, represents the distance between the millimeter wave radar and the human body, represents the unwrapping processed phase information data, represents the proportionality coefficient, represents the noise contained in the phase, represents the distance change caused by heartbeat.

[0032] In some embodiments, the mean value of the noise is usually 0, and the de-meaning processing of the transformed amplitude data and the unwrapped phase data can eliminate the constant term in the data and the influence on the subsequent processing.

[0033] In some embodiments, the breathing frequency range of the human body is usually in the range of 0.1-0.5Hz, and the heartbeat frequency range is usually in the range of 0.8-2Hz. By setting the passband of the bandpass filter to be 0.1-2Hz, the amplitude data and the phase data after de-meaning processing are filtered, which can enhance the vital sign signals contained in the amplitude data and the phase data, and reduce the influence of out-of-band noise on the subsequent vital sign signal measurement.

[0034] In some embodiments, the normalization processing of the amplitude data and the phase data can eliminate the influence of the proportionality coefficient and , so that the change range of the amplitude data is consistent with the change range of the phase data, as shown in Figure 6 , wherein the red solid line is the normalized amplitude data, and the blue dashed line is the normalized phase data.

[0035] In some embodiments, the expression of the normalized phase information data can be: ; wherein, represents the normalized phase information data, represents the sequence number of the peak data, represents the distance change caused by respiration, represents the noise contained in the normalized phase data.

[0036] In some embodiments, the expression of the normalized amplitude information data can be: ; wherein, represents the normalized amplitude information data, represents the distance change caused by heartbeat, represents the noise contained in the normalized phase data.

[0037] S3: performing cancellation processing on the normalized phase information data and the normalized amplitude information data to obtain a heartbeat signal.

[0038] The heartbeat signal is a signal reflecting the heartbeat condition.

[0039] In some embodiments, the expression of the heartbeat signal can be: ; wherein, represents the heartbeat signal, represents the serial number of the peak data, represents the normalized amplitude information data, represents the normalized phase information data, represents the distance change caused by heartbeat, represents the noise contained in the normalized phase data, represents the noise contained in the normalized amplitude data.

[0040] S4: performing weighted summation on the normalized phase information data and the normalized amplitude information data to obtain a respiration signal.

[0041] The respiration signal is a signal reflecting the respiration condition.

[0042] In some embodiments, the processor performs weighted summation on the normalized phase information data and the normalized amplitude information data with and respectively representing the weighting coefficients of the amplitude data and the phase data, to obtain the respiration signal.

[0043] In some embodiments, the expression of the respiration signal can be: ; ; wherein, represents the respiration signal, represents the weighting coefficient of the amplitude data, represents the weighting coefficient of the phase data, This indicates the change in distance caused by respiration.

[0044] S5: Filter the heartbeat and respiratory signals, analyze the time interval between adjacent maximum points, and obtain the real-time heart rate and real-time respiratory rate respectively, thus completing the measurement of respiratory rate and heart rate.

[0045] Real-time heart rate is information that reflects the current heart rate.

[0046] In some embodiments, the human heart rate typically falls within the range of 0.8-2 Hz. Setting the passband of the bandpass filter to 0.8-2 Hz is suitable for the heart rate signal. Filtering can further reduce the impact of residual respiratory signals after cancellation on the heartbeat signal. The filtered heartbeat signal is as follows: Figure 7 As shown. The first signal representing the human heartbeat i The moment when a maximum point occurs in the heartbeat data, such as Figure 7 The blue circle in the middle shows the calculated real-time heart rate of the human body.

[0047] In some embodiments, the expression for real-time heart rate can be: ; in, Indicates real-time heart rate. The first signal representing the human heartbeat i The moment when the maximum point is located in the heartbeat data.

[0048] Real-time respiratory rate is information that reflects the current rate of breathing.

[0049] In some embodiments, the human respiratory rate typically falls within the range of 0.1-0.5 Hz. Setting the passband of the bandpass filter to 0.1-0.5 Hz is used for the respiratory signal. Filtering can further reduce the impact of out-of-band noise on the respiratory signal. The filtered respiratory signal is as follows: Figure 8 As shown. Indicates the first human respiratory signal i The time at which a maximum point occurs in the respiratory data, such as Figure 8 The blue circle in the middle shows the calculated real-time respiratory rate of the human body.

[0050] In some embodiments, the expression for real-time respiratory rate can be: ; in, Indicates real-time respiratory rate. Indicates the first human respiratory signal i The time at which a maximum point occurs in the respiratory data.

[0051] In some embodiments of the present specification, a respiratory rate and heart rate measurement method based on millimeter wave radar amplitude and phase information fusion is provided. The amplitude information data and the phase information data are preprocessed to obtain normalized phase information data and normalized amplitude information data. The normalized phase information data and the normalized amplitude information data are processed to obtain a heartbeat signal. The normalized phase information data and the normalized amplitude information data are weighted and summed to obtain a breathing signal. Real-time heart rate and real-time respiratory rate are obtained by analysis. By comprehensively utilizing the amplitude and phase information of the millimeter wave radar echo, the complementary advantages of the two are fully utilized, the influence of the respiratory harmonic wave on the heartbeat information measurement is effectively reduced, and the accuracy, stability and anti-interference ability of the heart rate and respiratory rate measurement are improved.

Claims

1. A method for measuring respiratory rate and heart rate based on millimeter-wave radar amplitude and phase information fusion, characterized in that, include: S1: Acquire amplitude and phase information data of millimeter-wave radar human body echo signal; S2: Preprocess the phase information data and amplitude information data to obtain normalized phase information data and normalized amplitude information data, respectively; S3: Perform cancellation processing on the normalized phase information data and the normalized amplitude information data to obtain the heartbeat signal; S4: Weighted summation of normalized phase information data and normalized amplitude information data to obtain the respiratory signal; S5: Filter the heartbeat and respiratory signals, analyze the time interval between adjacent maximum points, and obtain the real-time heart rate and real-time respiratory rate respectively, thus completing the measurement of respiratory rate and heart rate.

2. The method for measuring human respiratory rate and heart rate based on millimeter-wave radar amplitude and phase information fusion according to claim 1, characterized in that, S1 includes: The maximum value search is performed on the millimeter-wave radar echo signal after the range-dimensional pulse compression processing is completed, and the amplitude information and phase information at the peak are extracted and used as amplitude information data and phase information data, respectively.

3. The method for measuring human respiratory rate and heart rate based on millimeter-wave radar amplitude and phase information fusion according to claim 1, characterized in that, The expressions for the amplitude information data and the phase information data are: ； in, Indicates the baseband signal of the human body echo. Indicates the sequence number of the peak data. Indicates the first n The amplitude of each peak data point, i.e., amplitude information data. Representing the natural constant in exponential form, Represents the imaginary unit. Indicates the first n The phase of each peak data point, i.e., phase information data.

4. The method for measuring human respiratory rate and heart rate based on millimeter-wave radar amplitude and phase information fusion according to claim 1, characterized in that, S2 includes: The phase information data is unwound to obtain unwound phase information data. Using a radar echo signal model, the amplitude information data is transformed so that the amplitude change characteristics are linearly proportional to the changes in respiration and heart rate, thus obtaining the transformed amplitude information data. The phase information data after unwinding and the amplitude information data after change are subjected to mean-removal processing to obtain mean-removed phase information data and mean-removed amplitude information data, respectively. Using typical human respiratory rate and heart rate as references, a bandpass filter is set, and the mean-removed phase information data and mean-removed amplitude information data are filtered respectively to obtain filtered phase information data and filtered amplitude information data. The filtered phase information data and the filtered amplitude information data are normalized respectively to obtain normalized phase information data and normalized amplitude information data.

5. The method for measuring human respiratory rate and heart rate based on millimeter-wave radar amplitude and phase information fusion according to claim 4, characterized in that, The expression for the phase information data obtained from the unwinding process is: ； in, This represents the phase information data from the unwinding process. Indicates the sequence number of the peak data. Indicates the first n The phase of each peak data point.

6. The method for measuring human respiratory rate and heart rate based on millimeter-wave radar amplitude and phase information fusion according to claim 4, characterized in that, The expression for the changed amplitude information data is: ； ； ； ； ； ； in, This represents the changed magnitude information data. Indicates the sequence number of the peak data. This represents the proportionality coefficient. This indicates the distance between a human body at rest and the millimeter-wave radar. This indicates the change in distance caused by respiration. This indicates the noise contained in the transformed amplitude. Indicates amplitude signal data, This indicates the distance between the millimeter-wave radar and the human body. This represents the phase information data from the unwinding process. This represents the proportionality coefficient. This indicates the noise contained in the phase. This indicates the change in distance caused by the heartbeat.

7. The method for measuring human respiratory rate and heart rate based on millimeter-wave radar amplitude and phase information fusion according to claim 4, characterized in that, The expression for the normalized phase information data is: ； in, This represents normalized phase information data. Indicates the sequence number of the peak data. This indicates the change in distance caused by respiration. This indicates the noise contained in the amplitude data after normalization. The expression for the normalized amplitude information data is: ； in, This represents normalized amplitude information data. This indicates the change in distance caused by heartbeats. This indicates the noise contained in the phase data after normalization.

8. The method for measuring human respiratory rate and heart rate based on millimeter-wave radar amplitude and phase information fusion according to claim 1, characterized in that, The expression for the heartbeat signal is: ； in, Indicates heartbeat signal, Indicates the sequence number of the peak data. This represents normalized amplitude information data. This represents normalized phase information data. This indicates the change in distance caused by heartbeats. This indicates the noise included in the phase data after normalization. This indicates the noise contained in the amplitude data after normalization. The expression for the respiratory signal is: ； ； in, Indicates a breathing signal. This represents the weighting coefficients for the amplitude data. Represents the weighting coefficients of the phase data. This indicates the change in distance caused by respiration.

9. The method for measuring human respiratory rate and heart rate based on millimeter-wave radar amplitude and phase information fusion according to claim 1, characterized in that, The expression for the real-time heart rate is: ； in, Indicates real-time heart rate. The first signal representing the human heartbeat i The moment when the maximum point is located in the heartbeat data; The expression for real-time respiratory rate is: ； in, Indicates real-time respiratory rate. Indicates the first human respiratory signal i The time at which a maximum point occurs in the respiratory data.

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