CN111929677A - Multi-human body vital sign ultra-wideband radar monitor based on eye-shaped differential antenna - Google Patents
Multi-human body vital sign ultra-wideband radar monitor based on eye-shaped differential antenna Download PDFInfo
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- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
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Abstract
The invention discloses an eye-shaped differential antenna-based multi-human body vital sign ultra-wideband radar monitor, which comprises an XETHRU X4 ultra-wideband radar chip, an ultra-wideband differential transmitting antenna, an ultra-wideband differential receiving antenna and a microprocessor with a QSPI interface, wherein the XETHRU X4 ultra-wideband radar chip is positioned on the front surface of a multilayer PCB, and the ultra-wideband differential transmitting antenna and the ultra-wideband differential receiving antenna are printed on the plane of the same multilayer PCB and are respectively positioned on the left side and the right side of the XETHRU X4 ultra-wideband radar chip. The invention has the advantages of high detection sensitivity, strong anti-interference performance and capability of distinguishing multi-target human body vital signs.
Description
Technical Field
The invention relates to the technical field of human body vital sign monitoring, in particular to an eye-shaped differential antenna-based multi-human body vital sign ultra-wideband radar monitoring instrument.
Background
Human body vital sign detecting instruments are generally classified into contact detecting instruments and non-contact detecting instruments. The contact detection instrument generally adopts devices such as electrodes and pressure sensors to be in physical contact with the skin of a human body to realize vital sign detection. Non-contact detecting instruments generally adopt devices such as infrared thermal detectors, biological radars and the like to detect human vital signs within a certain range from a human body. The non-contact detection instrument does not need to be in physical contact with a human body, is convenient to use, and has wide application prospects in the fields of health monitoring, personnel search and rescue and the like.
The non-contact detection instrument is a human body vital sign detection instrument based on a radar technology, and two systems are generally adopted, wherein one system is a frequency modulation continuous wave radar system; one is the ultra-wideband pulse radar regime. The frequency modulation continuous wave system is simple in equipment and low in cost, although vital signs such as human breath and heart rate can be detected, the distance and the body movement characteristics of a person are difficult to detect, and particularly in a complex scene where multiple persons exist, the vital signs of different persons are difficult to distinguish. In addition, because the isolation difficulty of the transmitting signal and the receiving signal of the frequency modulation continuous wave radar is high, when the leaked transmitting signal exists in the receiving channel, a weak vital sign signal of a human body is submerged in phase noise of the leaked transmitting signal, and the detection sensitivity is difficult to improve.
The human body life detector based on the ultra-wideband pulse system transmits ultra-wideband pulses with extremely narrow widths, has extremely high distance resolution and extremely small distance measurement dead zone. The ultra-wideband pulse human body life detector utilizes an ultra-wideband receiver to receive echo signals reflected by a target, detects the weak vibration of human body movement, respiration and heartbeat, and realizes the detection of human body vital signs by detecting Doppler frequency shift information generated by the weak vibration of the human body. The ultra-wideband human body life detector has certain penetrating power, and meanwhile, as the transmitting signal and the receiving signal work in a time-sharing mode, the defect that the transmitting signal is leaked to a receiving channel does not exist, and the detection sensitivity is improved. In addition, the time delay of the echo signal relative to the transmitting signal can be utilized, and the distance information of the human body can be determined while the vital signs of the human body are detected.
At present, when an ultra-wideband radar human body vital sign detecting instrument is designed, because a receiving antenna and a transmitting antenna need to work in a wider bandwidth range, and meanwhile, in order to reduce the thickness of the section of the antenna, an ultra-wideband planar printed antenna is usually adopted as the receiving antenna and the transmitting antenna. The ultra-wideband planar printed antenna usually uses a single feeding port for feeding, and transmits and receives electromagnetic wave signals on two sides of a plane where the antenna is located.
The novel ultra-wideband radar chip generally adopts differential signals to realize the feed of transmitting signals and receiving signals, when the ultra-wideband antenna of a single feed port is connected with the ultra-wideband radar chip with the differential feed port, a balun is required to be adopted to carry out the conversion of single-ended signals and differential signals, the use of the balun can bring the cost increase and the loss of signal power, meanwhile, the single-port feed antenna does not have the capacity of inhibiting common-mode noise, and the integrated design and the sensitivity improvement of a system are not facilitated.
In order to ensure the working bandwidth, the energy radiation mode of the ultra-wideband planar printed antenna is that energy radiation is arranged on both sides of the plane where the antenna is located, and the common equipment is arranged on the wall, the mattress and other scenes which only need to be radiated on one side, and when a signal is transmitted, half of energy is wasted due to radiation on both sides; during receiving, the back beam also receives useless interference and noise signals, and the improvement of the detection sensitivity of the system is not facilitated.
In order to reduce the equipment cost, the ultra-wideband human vital sign detecting instrument generally adopts a group of receiving and transmitting antennas and an ultra-wideband radar chip, so that the angle of a target is difficult to distinguish when the target is detected, which is a great difficulty brought by simultaneous detection and resolution of vital signs of multiple persons in a complex scene.
Disclosure of Invention
The invention aims to solve the problems and designs a multi-human body vital sign ultra-wideband radar monitoring instrument based on an eye-shaped differential antenna.
The technical scheme of the invention is that the multi-human body vital sign ultra-wideband radar monitoring instrument based on the eye-shaped differential antenna comprises an XETHRU X4 ultra-wideband radar chip, an ultra-wideband differential transmitting antenna, an ultra-wideband differential receiving antenna and a microprocessor with a QSPI interface, wherein the XETHRU X4 ultra-wideband radar chip is positioned on the front surface of a multilayer PCB (printed Circuit Board), and the ultra-wideband differential transmitting antenna and the ultra-wideband differential receiving antenna are printed on the same plane of the multilayer PCB and are respectively positioned on the left side and the right side of the XETHRU X4 ultra-wideband radar chip;
the ultra-wideband differential transmitting antenna is connected to a transmitting signal feed pin of an XETHRU X4 ultra-wideband radar chip through a differential microstrip line with ground plane impedance of 50 ohms and differential impedance of 100 ohms;
the ultra-wideband differential receiving antenna is connected to a receiving signal feed pin of an XETHRU X4 ultra-wideband radar chip through a differential microstrip line with ground plane impedance of 50 ohms and differential impedance of 100 ohms;
the microprocessor chip with the QSPI interface is connected with an XETHRU X4 ultra-wideband radar chip through the QSPI interface and is used for communication between the microprocessor and the ultra-wideband radar chip;
the ultra-wideband differential receiving antenna and the ultra-wideband differential receiving antenna adopt the same structure of an eye-shaped differential ultra-wideband antenna with a reflector.
The eye-shaped differential ultra-wideband antenna with the reflector adopts FR4 as a substrate and is realized by a common layer of a ground plane, a dielectric layer, a radiation patch layer, a dielectric layer and a reflector plate.
The shape of the plane is rectangular, and an elliptical resonant cavity is formed in the plane relative to a central line; the radiation patch A is an elliptical radiation patch, and electromagnetic wave energy is mainly radiated from a gap between the radiation patch and the ground plane elliptical resonant cavity;
the radiation patch A is provided with an elliptical impedance matching tuning cavity A and an impedance matching branch A and is used for realizing impedance matching of broadband signals in a working frequency range; the radiating patch B is the same as the radiating patch A in shape and is symmetrical relative to the center line of the ground plane.
The horizontal material is a metal copper foil, and the thickness of the horizontal material is 35 um; the first dielectric layer is made of FR4 glass fiber medium and has the thickness of 0.1163 mm; the radiation patch layer is made of a metal copper foil, and the thickness of the radiation patch layer is 35 um; the second dielectric layer is made of FR4 glass fiber medium and has the thickness of 0.9605 mm; the reflecting plate is made of metal copper and has the thickness of 1 mm; an air medium is arranged between the reflecting plate and the second medium layer, and the distance between the reflecting plate and the second medium layer is 9 mm.
The line width of the differential microstrip line is 0.1792mm, and the line spacing is 0.4 mm.
The microprocessor chip with the QSPI interface controls the XETHRU X4 ultra-wideband radar chip to transmit an ultra-wideband pulse signal through the QSPI interface, and reads echo data received by the XETHRU X4 ultra-wideband radar chip.
The algorithm processing process after the microprocessor chip with the QSPI interface reads the echo data is as follows:
(1) reading raw radar echo data
Reading the 1 st frame of radar echo data in the 1 st radar repeating cycle, wherein the number of range resolution units is N, and the echo data of the nth range resolution unit is represented as s0(0, N), N ═ 0,1,2, ·, N-1; continuously reading M frames of radar echo data from the 1 st radar repeating cycle, wherein the echo data of the nth range resolution unit of the mth frame is expressed as s0(M, N), M-0, 1,2, 1, N, M-1, N-0, 1,2, N-1, forming a raw echo data matrix s0(m,n)]M×N
In the formed original echo data matrix, the row direction is fast time data, the sampling interval is delta t, the size of a corresponding distance resolution unit is delta R-c delta t/2, and c is the light speed; the column direction is slow time data, and the sampling interval is T, namely the repeat period of the radar;
(2) for the original echo data matrix [ s ]0(m,n)]M×NPerforming DC component removal processing
Averaging all elements of the original echo data matrix, expressed as
Subtracting s from each element of the original echo data matrix0avObtaining the echo data matrix [ s (m, n) after removing the direct current component]M×N，
The influence of fixed target clutter can be weakened by removing the direct current component;
(3) cumulative short-time Fourier transform of echo data matrix by column
Selecting a window function h (L), wherein L is 0,1,2, L-1 is a hamming window, the length of the window function is L, and performing short-time Fourier transform on the nth line data of the echo data matrix to obtain the nth line data of the echo data matrix
Wherein q is 0,1,2, and M-1 represents the position of the window function when the window function is moved with a step size of 1;
sequentially accumulating the data subjected to short-time Fourier transform on the nth line of data of the echo data matrix according to the value of q to obtain an accumulated short-time Fourier transform result of the nth line of data of the echo data matrix
For the nth column, n is a definite value, which is a vector of length M, k represents the doppler frequency; sequentially processing N lines of data of the echo data matrix to obtain a range-Doppler matrix of radar echoes
(4) Target detection and parameter extraction
The range-Doppler matrix of the radar echo is a complex matrix with an amplitude matrix of
Target detection using amplitude matrix for the (k) thT,nT) When the unit is detected, the detection threshold is taken
Where α is a constant, typically taken as 0.5; the detection process is that each unit of the amplitude matrix is compared with the detection threshold of the unit, and if the detection threshold is exceeded, the target exists at the distinguishing unit;
if it is (k)T,nT) If the target 1 exists in the unit, calculating the distance parameter of the extracted target as R1＝nTc Δ t/2, target Doppler shift parameter of
In general, if the distance unit nTA plurality of corresponding Doppler resolution units are arranged for detecting a single human target, the number of the corresponding Doppler resolution units is respectively corresponding to the respiratory frequency and the heartbeat frequency of the human target at the distance unit, the respiratory frequency of a normal human body is concentrated between 0.2Hz and 0.75Hz, and the heartbeat frequency is between 1Hz and 2.5 Hz; according to different detected Doppler frequency shift values of the human body target, the respiratory frequency and the heartbeat frequency of the same human body target can be distinguished;
after calculating and extracting the target parameters, the state of the target adopts the target state variables
zp＝(Rp,fp,respiration,fp,heartrate) Wherein p represents the target number;
(5) detection resolution, tracking and abnormal condition early warning of multiple human body target vital signs
For a certain time u, after detection and parameter calculation extraction, a characteristic parameter set of a plurality of targets can be obtained and expressed as
Zu＝{z1,z2,...zp,...zP}
Because the non-contact human body vital sign ultra-wideband monitor has no angle information, the target cannot be distinguished through the angle information; when a plurality of targets appear in a scene, if the targets appear at different distances, the different targets can be distinguished through distance information; however, when a plurality of targets are located at the same distance in different angular directions, the resolution is difficult; because the position of the human body cannot be mutated, a Kalman filtering tracking algorithm is adopted for multi-target tracking, target tracks are established by using the historical state information of the targets, and multi-target tracking and distinguishing are realized by using the characteristic that different targets have different motion tracks.
The specific process for realizing multi-target tracking and distinguishing is as follows:
1) starting of a target track: after a target state variable is detected and obtained, if a target track does not exist in the current system or does not belong to the existing target track in the current system, a target track is newly established, and the target state variable is used as the starting point of the target track;
2) and target state association: after a target state variable is detected and obtained, comparing the state variable with a Kalman filtering one-step advanced prediction value obtained by the last updating of the existing target track, if the geometric distance between the target state variable and the filtering value is less than a correlation threshold, considering that the target state variable belongs to a new measurement value of the current existing target track, and updating the current existing target track by using the target state variable;
3) updating the target track: after the target state association is completed, calculating a Kalman filtering gain matrix and a prediction covariance matrix according to a Kalman filtering algorithm formula, updating the current target track by using an associated target state variable according to a state updating formula of the Kalman filtering algorithm;
4) and (3) terminating the target track: when the existing certain item target track has no available target state variable for continuous 9 times to update the state, the target track is considered to be terminated; the disappearance of the target is usually caused by the fact that the human body moves beyond the detection range of the sensor, the object blocks or the human body vital sign is suddenly abnormal, belongs to an abnormal event, and triggers the monitoring and early warning message.
Advantageous effects
The multi-human body vital sign ultra-wideband radar monitor manufactured by the technical scheme of the invention based on the eye-shaped differential antenna has the advantages that,
(1) the differential reflection coefficient-10 dB bandwidth of the eye-type ultra-wideband differential antenna is 5.2GHz-12GHz, and the radiation and the reception of microwave signals with the working bandwidth of the XETHRU X4 ultra-wideband radar chip are realized. Because the feed form of the eye-type ultra-wideband differential antenna is differential feed, the use of a balun is avoided, the transmission loss and the cost are reduced, and the detection sensitivity of the system is improved.
Because the differential signal has the capacity of resisting common-mode noise, when the eye-type ultra-wideband differential antenna is used for transmitting and receiving, the performance of resisting common-mode noise interference of the system is improved.
The eye-type ultra-wideband differential antenna adopts the reflecting plate to realize unilateral radiation and reception, compared with the reflecting plate which is not adopted, the gain of the antenna is increased by 3dB, the utilization rate of transmitted signal energy is improved, and the detection sensitivity of the system is improved; meanwhile, the clutter signal intensity received by the back beam is greatly weakened, and the clutter interference resistance of the system is improved.
(2) The multi-person vital sign detection and separation processing algorithm based on distance information and micro Doppler characteristics utilizes accumulated short-time Fourier transform to extract respiratory frequency and heartbeat frequency of different distance units, three-dimensional target state variables of distance, respiratory frequency and heartbeat frequency are constructed, a human body target track is formed, multi-target distinguishing, tracking and abnormal processing are further achieved through a Kalman filtering algorithm, simultaneous monitoring of multi-person targets is achieved, and the defect that a traditional monitor cannot distinguish the multiple targets is overcome.
Drawings
FIG. 1 is a schematic block diagram of a multi-human body vital sign ultra-wideband radar monitor based on an eye-shaped differential antenna according to the present invention;
fig. 2 is a schematic diagram of a stacked structure of an eye-shaped ultra-wideband differential antenna according to the present invention;
figure 3 is a bottom perspective view of an eye-shaped ultra-wideband differential antenna according to the present invention;
figure 4 is a schematic diagram of the dimensions of an eye-shaped ultra-wideband differential antenna according to the present invention;
FIG. 5 is a schematic diagram of a raw echo data matrix according to the present invention;
FIG. 6 is a schematic diagram of the cumulative short-time Fourier transform of the present invention;
FIG. 7 is a schematic diagram of object detection and parameter extraction according to the present invention;
figure 8 is a graph of the differential reflection coefficient of an eye-shaped ultra-wideband differential antenna according to the present invention;
fig. 9 is a graph comparing the gain (F ═ 8GHz) of the eye-shaped ultra-wideband differential antenna of the present invention;
figure 10 is a graph of gain versus frequency for an eye-shaped ultra-wideband differential antenna in accordance with the present invention;
fig. 11 is a gain comparison graph of an eye-shaped ultra-wideband differential antenna with and without a reflector according to the present invention (F ═ 8 GHz);
FIG. 12 is a schematic block diagram of a circuit of the multi-human body vital sign ultra-wideband radar monitor based on the eye-shaped differential antenna according to the present invention;
FIG. 13 is a front view of a multi-layered PCB (physical product) according to the present invention;
FIG. 14 is a rear view of a multi-layered PCB (physical product) according to the present invention;
FIG. 15 is a waveform diagram of respiration detected by the multi-human body vital sign ultra-wideband radar monitoring instrument based on the eye-shaped differential antenna;
in the figure, 1, a ground plane; 2. a first dielectric layer; 3. a radiation patch layer; 4. a second dielectric layer; 5. a reflective plate.
Detailed Description
The invention is described in detail with reference to the accompanying drawings, and the technical scheme of the invention mainly solves the technical problems that the single-port feed planar antenna and the differential feed ultra-wideband radar chip of the existing ultra-wideband human vital sign monitoring equipment are difficult to integrate, the interference and noise signal inhibiting capability is weak, and the defects of multi-person vital signs are difficult to detect and distinguish;
the invention provides a novel non-contact ultra-wideband radar monitor for human vital signs. The monitor can inhibit common-mode noise and interference signals while reducing cost and improving integration level, improves detection sensitivity of equipment, and realizes simultaneous detection and resolution of vital signs of multiple persons in a complex scene.
As shown in fig. 1 to 15, the technical solution adopted by the present invention to solve the technical problem is:
the non-contact human body vital sign ultra-wideband monitor comprises an XETHRU X4 ultra-wideband radar chip, an ultra-wideband differential transmitting antenna, an ultra-wideband differential receiving antenna and a microprocessor with a QSPI interface, wherein a data processing algorithm adopts a multi-person vital sign detection and separation processing algorithm based on distance information and micro Doppler characteristics.
The connection relationship among all parts is as follows: the XETHRU X4 ultra-wideband radar chip is positioned on the front surface of the multilayer PCB, and the ultra-wideband differential transmitting antenna and the ultra-wideband differential receiving antenna are printed on the plane of the same multilayer PCB and are respectively positioned on the left side and the right side of the XETHRU X4 ultra-wideband radar chip;
the ultra-wideband differential transmitting antenna is connected to a transmitting signal feed pin of an XETHRU X4 ultra-wideband radar chip through a differential microstrip line with ground plane impedance of 50 ohms and differential impedance of 100 ohms;
the ultra-wideband differential receiving antenna is connected to a receiving signal feed pin of an XETHRU X4 ultra-wideband radar chip through a differential microstrip line with ground plane impedance of 50 ohms and differential impedance of 100 ohms;
the microprocessor chip with the QSPI interface is connected with the XETHRU X4 ultra-wideband radar chip through the QSPI interface and is used for communication between the microprocessor and the ultra-wideband radar chip.
The ultra-wideband differential receiving antenna and the ultra-wideband differential receiving antenna adopt the same structure of an eye-shaped differential ultra-wideband antenna with a reflector, and the implementation mode is as follows:
(1) laminated structure
The eye-shaped differential ultra-wideband antenna with the reflector is realized by adopting FR4 as a substrate and is realized by 5 layers including a ground plane, a first dielectric layer, a radiation patch layer, a second dielectric layer and a reflector plate.
The horizontal material is a metal copper foil, and the thickness is 35 um; the first dielectric layer is made of FR4 glass fiber medium and has the thickness of 0.1163 mm; the radiation patch layer is made of metal copper foil, and the thickness of the radiation patch layer is 35 um; the second dielectric layer is made of FR4 glass fiber medium and has the thickness of 0.9605 mm; the reflecting plate is made of metal copper and has the thickness of 1 mm; an air medium is arranged between the reflecting plate and the second medium layer, and the distance between the reflecting plate and the second medium layer is 9 mm.
(2) Component assembly and function
The ground plane is rectangular, and an elliptical resonant cavity is arranged in the ground plane relative to the center line. The radiation patch A is an elliptical radiation patch, and electromagnetic wave energy is mainly radiated from a gap between the radiation patch and the ground plane elliptical resonant cavity.
The radiation patch A is provided with an elliptical impedance matching tuning cavity A and an impedance matching branch A and is used for realizing impedance matching of broadband signals in the working frequency range. The radiating patch B is the same shape as the radiating patch a and is symmetrical with respect to the ground plane midline.
And the feed differential microstrip line is used for realizing feed connection between the ultra-wideband radar chip and the antenna. The line width of the differential microstrip line is 0.1792mm, and the line spacing is 0.4 mm.
(3) Size of parts
The detailed dimensions of the components are shown in figure 4.
The microprocessor chip with the QSPI interface controls the XETHRU X4 ultra-wideband radar chip to emit ultra-wideband pulse signals through the QSPI interface, reads echo data received by the XETHRU X4 ultra-wideband radar chip, adopts a multi-person vital sign detection and separation processing algorithm based on distance information and micro Doppler characteristics, and the algorithm processing process is as follows:
(1) reading raw radar echo data
Reading the 1 st frame of radar echo data in the 1 st radar repeating cycle, wherein the number of range resolution units is N, and the echo data of the nth range resolution unit is represented as s0(0, N), N ═ 0,1,2. Continuously reading M frames of radar echo data from the 1 st radar repeating cycle, wherein the echo data of the nth range resolution unit of the mth frame is expressed as s0(M, N), M-0, 1,2, 1, N, M-1, N-0, 1,2, N-1, forming a raw echo data matrix s0(m,n)]M×N
In the formed original echo data matrix, the row direction is fast time data, the sampling interval is delta t, the size of a corresponding distance resolution unit is delta R-c delta t/2, and c is the light speed; the column direction is slow time data and the sampling interval is T, i.e. the repetition period of the radar.
(2) For the original echo data matrix [ s ]0(m,n)]M×NPerforming DC component removal processing
Averaging all elements of the original echo data matrix, expressed as
Subtracting s from each element of the original echo data matrix0avObtaining the echo data matrix [ s (m, n) after removing the direct current component]M×N，
The dc component removal process can attenuate the effects of stationary target clutter.
(3) Cumulative short-time Fourier transform of echo data matrix by column
Selecting a window function h (L), wherein L is 0,1,2, L-1 is a hamming window, the length of the window function is L, and performing short-time Fourier transform on the nth line data of the echo data matrix to obtain the nth line data of the echo data matrix
Where q is 0,1,2, and M-1 denotes the position of the window function when the window function is moved by a step size of 1.
Sequentially accumulating the data subjected to short-time Fourier transform on the nth line of data of the echo data matrix according to the value of q to obtain an accumulated short-time Fourier transform result of the nth line of data of the echo data matrix
For the nth column, n is a deterministic value, which is a vector of length M, and k represents the Doppler frequency. Sequentially processing N lines of data of the echo data matrix to obtain a range-Doppler matrix of radar echoes
(4) Target detection and parameter extraction
The range-Doppler matrix of the radar echo is a complex matrix with an amplitude matrix of
Target detection using amplitude matrix for the (k) thT,nT) When the unit is detected, the detection threshold is taken
Where α is a constant, typically taken to be 0.5. The detection process is that each unit of the amplitude matrix is compared with the detection threshold of the unit, and if the detection threshold is exceeded, the target exists at the distinguishing unit.
If it is (k)T,nT) If the target 1 exists in the unit, calculating the distance parameter of the extracted target as R1＝nTc Δ t/2, target Doppler shift parameter of
In general, if the distance unit nTThe corresponding Doppler resolution units can be multiple and respectively correspond to the respiratory frequency and the heartbeat frequency of the human target at the distance unit, the respiratory frequency of the normal human body is concentrated between 0.2Hz and 0.75Hz, and the heartbeat frequency is between 1Hz and 2.5 Hz. According to different Doppler frequency shift values of detected human body targets, the breathing frequency of the same human body target can be distinguishedRate and heartbeat frequency.
After calculating and extracting the target parameter, the state of the target adopts a target state variable zp＝(Rp,fp,respiration,fp,heartrate) Wherein p represents the object number.
(5) Detection resolution, tracking and abnormal condition early warning of multiple human body target vital signs
For a certain time u, after detection and parameter calculation extraction, a characteristic parameter set of a plurality of targets can be obtained and expressed as
Zu＝{z1,z2,...zp,...zP}
Because the non-contact human vital sign ultra-wideband monitor does not have angle information, the target cannot be distinguished through the angle information. When a plurality of targets appear in a scene, if the targets appear at different distances, the different targets can be distinguished through distance information; however, when multiple targets are located at the same distance in different angular directions, resolution is difficult. Because the position of the human body cannot be mutated, a Kalman filtering tracking algorithm is adopted for multi-target tracking, target tracks are established by using the historical state information of the targets, and multi-target tracking and distinguishing are realized by using the characteristic that different targets have different motion tracks. The specific process is as follows:
1) starting of a target track: after the target state variable is detected and obtained, if the target track does not exist in the current system or does not belong to the existing target track in the current system, a target track is newly established, and the target state variable is used as the starting point of the target track.
2) And target state association: and after the target state variable is detected and obtained, comparing the state variable with a Kalman filtering one-step advanced prediction value obtained by the last updating of the existing target track, if the geometric distance between the target state variable and the filtering value is less than a correlation threshold, considering that the target state variable belongs to a new measurement value of the current existing target track, and updating the current existing target track by using the target state variable.
3) Updating the target track: and after the target state association is completed, calculating a Kalman filtering gain matrix and a prediction covariance matrix according to a Kalman filtering algorithm formula, updating the current target track by using an associated target state variable according to a state updating formula of the Kalman filtering algorithm.
4) And (3) terminating the target track: when the current existing target track of a certain item has no available target state variable for continuous 9 times to update the state, the target track is considered to be terminated. The disappearance of the target is usually caused by the fact that the human body moves beyond the detection range of the sensor, the object blocks or the human body vital sign is suddenly abnormal, belongs to an abnormal event, and triggers the monitoring and early warning message.
The technical solutions described above only represent the preferred technical solutions of the present invention, and some possible modifications to some parts of the technical solutions by those skilled in the art all represent the principles of the present invention, and fall within the protection scope of the present invention.
Claims (7)
1. A multi-human body vital sign ultra-wideband radar monitor based on an eye-shaped differential antenna is characterized by comprising an XETHRU X4 ultra-wideband radar chip, an ultra-wideband differential transmitting antenna, an ultra-wideband differential receiving antenna and a microprocessor with a QSPI interface, wherein the XETHRU X4 ultra-wideband radar chip is positioned on the front of a multilayer PCB (printed Circuit Board), and the ultra-wideband differential transmitting antenna and the ultra-wideband differential receiving antenna are printed on the plane of the same multilayer PCB and are respectively positioned on the left side and the right side of the XETHRU X4 ultra-wideband radar chip;
the ultra-wideband differential transmitting antenna is connected to a transmitting signal feed pin of an XETHRU X4 ultra-wideband radar chip through a differential microstrip line with ground plane impedance of 50 ohms and differential impedance of 100 ohms;
the ultra-wideband differential receiving antenna is connected to a receiving signal feed pin of an XETHRU X4 ultra-wideband radar chip through a differential microstrip line with ground plane impedance of 50 ohms and differential impedance of 100 ohms;
the microprocessor chip with the QSPI interface is connected with an XETHRU X4 ultra-wideband radar chip through the QSPI interface and is used for communication between the microprocessor and the ultra-wideband radar chip;
the ultra-wideband differential receiving antenna and the ultra-wideband differential receiving antenna adopt the same structure of an eye-shaped differential ultra-wideband antenna with a reflector.
2. The multi-human-body vital sign ultra-wideband radar monitor based on the eye-shaped differential antenna as claimed in claim 1, wherein the eye-shaped differential ultra-wideband antenna with the reflector is implemented by using FR4 as a substrate, and comprises a ground plane, a dielectric layer, a radiation patch layer, a dielectric layer and a reflector plate.
The shape of the plane is rectangular, and an elliptical resonant cavity is formed in the plane relative to a central line; the radiation patch A is an elliptical radiation patch, and electromagnetic wave energy is mainly radiated from a gap between the radiation patch and the ground plane elliptical resonant cavity;
the radiation patch A is provided with an elliptical impedance matching tuning cavity A and an impedance matching branch A and is used for realizing impedance matching of broadband signals in a working frequency range; the radiating patch B is the same as the radiating patch A in shape and is symmetrical relative to the center line of the ground plane.
3. The ultra-wideband radar monitor for vital signs of multiple persons based on an eye-shaped differential antenna as claimed in claim 1, wherein the planar material is a metal copper foil with a thickness of 35 um; the first dielectric layer is made of FR4 glass fiber medium and has the thickness of 0.1163 mm; the radiation patch layer is made of a metal copper foil, and the thickness of the radiation patch layer is 35 um; the second dielectric layer is made of FR4 glass fiber medium and has the thickness of 0.9605 mm; the reflecting plate is made of metal copper and has the thickness of 1 mm; an air medium is arranged between the reflecting plate and the second medium layer, and the distance between the reflecting plate and the second medium layer is 9 mm.
4. The ultra-wideband radar monitor for vital signs of multiple persons based on an eye-shaped differential antenna as claimed in claim 1, wherein the line width of the differential microstrip line is 0.1792mm and the line spacing is 0.4 mm.
5. The multi-person vital sign ultra-wideband radar monitor based on the eye-shaped differential antenna as claimed in claim 1, wherein the microprocessor chip with the QSPI interface controls the XETHRU X4 ultra-wideband radar chip to transmit the ultra-wideband pulse signal through the QSPI interface, and reads the echo data received by the XETHRU X4 ultra-wideband radar chip.
6. The multi-human-body vital sign ultra-wideband radar monitor based on the eye-shaped differential antenna according to claim 5, wherein the algorithm processing procedure after the microprocessor chip with the QSPI interface reads the echo data is as follows:
(1) reading raw radar echo data
Reading the 1 st frame of radar echo data in the 1 st radar repeating cycle, wherein the number of range resolution units is N, and the echo data of the nth range resolution unit is represented as s0(0, N), N ═ 0,1,2, ·, N-1; continuously reading M frames of radar echo data from the 1 st radar repeating cycle, wherein the echo data of the nth range resolution unit of the mth frame is expressed as s0(M, N), M-0, 1,2, 1, N, M-1, N-0, 1,2, N-1, forming a raw echo data matrix s0(m,n)]M×N
In the formed original echo data matrix, the row direction is fast time data, the sampling interval is delta t, the size of a corresponding distance resolution unit is delta R-c delta t/2, and c is the light speed; the column direction is slow time data, and the sampling interval is T, namely the repeat period of the radar;
(2) for the original echo data matrix [ s ]0(m,n)]M×NPerforming DC component removal processing, and averaging all elements of the original echo data matrix, wherein the average value is expressed as
Subtracting s from each element of the original echo data matrix0avTo obtainEcho data matrix after DC component [ s (m, n)]M×N，
The influence of fixed target clutter can be weakened by removing the direct current component;
(3) cumulative short-time Fourier transform of echo data matrix by column
Selecting a window function h (L), wherein L is 0,1,2, L-1 is a hamming window, the length of the window function is L, and performing short-time Fourier transform on the nth line data of the echo data matrix to obtain the nth line data of the echo data matrix
Wherein q is 0,1,2, and M-1 represents the position of the window function when the window function is moved with a step size of 1;
sequentially accumulating the data subjected to short-time Fourier transform on the nth line of data of the echo data matrix according to the value of q to obtain an accumulated short-time Fourier transform result of the nth line of data of the echo data matrix
For the nth column, n is a definite value, which is a vector of length M, k represents the doppler frequency; sequentially processing N lines of data of the echo data matrix to obtain a range-Doppler matrix of radar echoes
(4) Target detection and parameter extraction
The range-Doppler matrix of the radar echo is a complex matrix with an amplitude matrix of
Target detection using amplitude matrix for the (k) thT,nT) When the unit is detected, the detection threshold is taken
Where α is a constant, typically taken as 0.5; the detection process is that each unit of the amplitude matrix is compared with the detection threshold of the unit, and if the detection threshold is exceeded, the target exists at the distinguishing unit;
if it is (k)T,nT) If the target 1 exists in the unit, calculating the distance parameter of the extracted target as R1＝nTc Δ t/2, target Doppler shift parameter of
In general, if the distance unit nTA plurality of corresponding Doppler resolution units are arranged for detecting a single human target, the number of the corresponding Doppler resolution units is respectively corresponding to the respiratory frequency and the heartbeat frequency of the human target at the distance unit, the respiratory frequency of a normal human body is concentrated between 0.2Hz and 0.75Hz, and the heartbeat frequency is between 1Hz and 2.5 Hz; according to different detected Doppler frequency shift values of the human body target, the respiratory frequency and the heartbeat frequency of the same human body target can be distinguished;
after calculating and extracting the target parameters, the state of the target adopts the target state variables
zp＝(Rp,fp,respiration,fp,heartrate) Wherein p represents the target number;
(5) detection resolution, tracking and abnormal condition early warning of multiple human body target vital signs
For a certain time u, after detection and parameter calculation extraction, a characteristic parameter set of a plurality of targets can be obtained and expressed as
Zu＝{z1,z2,...zp,...zP}
Because the non-contact human body vital sign ultra-wideband monitor has no angle information, the target cannot be distinguished through the angle information; when a plurality of targets appear in a scene, if the targets appear at different distances, the different targets can be distinguished through distance information; however, when a plurality of targets are located at the same distance in different angular directions, the resolution is difficult; because the position of the human body cannot be mutated, a Kalman filtering tracking algorithm is adopted for multi-target tracking, target tracks are established by using the historical state information of the targets, and multi-target tracking and distinguishing are realized by using the characteristic that different targets have different motion tracks.
7. The ultra-wideband radar monitor for vital signs of multiple persons based on the eye-shaped differential antenna as claimed in claim 6, wherein the specific process for realizing multi-target tracking and distinguishing is as follows:
1) starting of a target track: after a target state variable is detected and obtained, if a target track does not exist in the current system or does not belong to the existing target track in the current system, a target track is newly established, and the target state variable is used as the starting point of the target track;
2) and target state association: after a target state variable is detected and obtained, comparing the state variable with a Kalman filtering one-step advanced prediction value obtained by the last updating of the existing target track, if the geometric distance between the target state variable and the filtering value is less than a correlation threshold, considering that the target state variable belongs to a new measurement value of the current existing target track, and updating the current existing target track by using the target state variable;
3) updating the target track: after the target state association is completed, calculating a Kalman filtering gain matrix and a prediction covariance matrix according to a Kalman filtering algorithm formula, updating the current target track by using an associated target state variable according to a state updating formula of the Kalman filtering algorithm;
4) and (3) terminating the target track: when the existing certain item target track has no available target state variable for continuous 9 times to update the state, the target track is considered to be terminated; the disappearance of the target is usually caused by the fact that the human body moves beyond the detection range of the sensor, the object blocks or the human body vital sign is suddenly abnormal, belongs to an abnormal event, and triggers the monitoring and early warning message.
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| CN113729655B (en) * | 2021-09-26 | 2024-03-08 | 重庆邮电大学 | Method for separating UWB radar sensor receiving signals |
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