CN108283496B - Respiration detection method in non-contact sensing mode - Google Patents
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Abstract
The application discloses a breath detection method in a non-contact sensing mode. A method for identifying a breath detection region, comprising: constructing a first Fresnel zone by taking the position of the sending equipment and the position of the receiving equipment as elliptic focuses, taking the distance between the position of the sending equipment and the position of the receiving equipment as a focal distance and according to the wavelength of a radio-frequency signal sent by the sending equipment; calculating the amplitudes of the signals when the human body enters different positions of the first Fresnel zone according to different clearances; identifying detectable and undetectable regions in the breath detection region based on the calculated magnitudes of the amplitudes of the signals at the different locations.
Description
Technical Field
The invention relates to a contactless respiration detection method, in particular to a contactless respiration detection method based on commercial wireless local area network equipment.
Background
Respiratory rate is an important vital sign that can be used not only to monitor disease and health status, but also to predict some emergency situations that require immediate clinical attention, such as sudden respiratory arrest. It has been reported that nearly 5% of the population suffers from respiratory related diseases such as Sleep Apnea Syndrome (SAS). A recent study also showed that respiratory abnormalities are a major cause of sudden infant death syndrome. In many cases, respiratory patients exhibit only short-term or random symptoms. Therefore, low cost and continuous respiratory monitoring is essential in a home environment.
Two common methods of clinical continuous respiration monitoring are thoracic impedance and carbon dioxide concentration monitoring. However, these methods are expensive in equipment and require trained care personnel to operate the monitoring equipment to prevent failure of the equipment. While in ordinary household use, a non-contact and non-invasive monitoring mode is more attractive. Therefore, some research efforts have been directed to the contactless wireless sensing of human breathing. For example, USRP 1 and UWB 2 signals are used for breath detection, but these are dedicated hardware devices that limit their application in real life. Documents [3] to [6] propose to detect respiration based on WiFi rf signals, however, these detection systems can only detect respiration at specific positions, and cannot identify the dead zone of respiration detection, and cannot explain the difference in respiration detection effect in different postures. Document [7] introduces a respiration detection method based on a fresnel zone model, and guides the respiration detection outside the first fresnel zone by using a reflection theory, however, a more complex diffraction effect occupies a dominant factor in the first fresnel zone, and the quality of the detection effect cannot be quantitatively depicted in the zone.
Cited documents:
[1]Ruth Ravichandran,Elliot Saba,Ke-Yu Chen,Mayank Goel,SidhantGupta,and Shwetak N Patel.2015.WiBreathe:Estimating respiration rate usingwireless signals in natural settings in the home.In International Conferenceon Pervasive Computing and Communications(PerCom).IEEE,St.Louis,MO,USA.
[2]Svetha Venkatesh,Christopher R Anderson,Natalia V Rivera,and RMichael Buehrer.2005.Implementation and analysis of respiration-rateestimation using impulse-based UWB.In In Military Communications Conference,MILCOM 2005.IEEE.
[3]Heba Abdelnasser,Khaled A Harras,and MoustafaYoussef.2015.Ubibreathe:Aubiquitous non-invasive wifi-based breathingestimator.In arXiv preprint arXiv:1505.02388(2015).
[4]Xuefeng Liu,Jiannong Cao,Shaojie Tang,Jiaqi Wen,and PengGuo.2016.Contactless Respiration Monitoring via WiFi Signals.MobileComputing,IEEE Transactions on(2016).
[5]Jian Liu,Yan Wang,Yingying Chen,Jie Yang,Xu Chen,and JerryCheng.2015.Tracking Vital Signs During Sleep Leveraging Off-the-shelf WiFi.InProceedings of the 16th ACM International Symposium on Mobile Ad HocNetworking and Computing.ACM,267–276.
[6]Chenshu Wu,Zheng Yang,Zimu Zhou,Xuefeng Liu,Yunhao Liu,andJiannong Cao.2015.Non-Invasive Detection of Moving and Stationary Human WithWiFi.Selected Areas in Communications,IEEE Journal on 33,11(2015),2329–2342.
[7]HaoWang,Daqing Zhang,Junyi Ma,YashaWang,YuxiangWang,DanWu,Tao Gu,and Bing Xie.2016.Human Respiration Detection with Commodity WiFi Devices:DoUser Location and Body Orientation Matter？.In Proceedings of theInternational Joint Conference on Pervasive and Ubiquitous Computing,UbiComp’16.
disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a non-contact breath detection method, which comprises the steps of detecting the breath of a human body by using a wireless radio frequency signal, calibrating the position where the breath can be detected and identifying a detection blind area according to the difference of the positions of the human body in a first Fresnel area; the breathing detection device is used for guiding the breathing detection of the human body at different positions according to the difference of breathing detection effects when the human body lies and sits.
Related concepts of the fresnel zone: after a radio frequency signal is transmitted by a transmitting device, the radio frequency signal reaches a receiving end through a plurality of paths in space, namely, the signal received by the receiving end is superposition of a plurality of signals, according to the wave interference principle, a weakened signal is generated when the lengths of two paths of the signal are different by odd times of a half wavelength (lambda/2), and an enhanced signal is generated when the lengths of two paths of the signal are different by even times of the half wavelength. When the transmitting device and the receiving device are fixed, the length of the direct path (LoS) is fixed, and the phase deflection pi caused by reflection is considered, an enhanced signal is generated when the length difference between the reflection path and the direct path is odd times of half wavelength, and a weakened signal is generated when the length difference is even times of half wavelength, and the positions of the odd times and the even times of the half wavelength are the boundaries of the fresnel zone. When the difference in length between the reflected path and the direct path is i x λ/2, | TQi|+|QiR | - | TR | ═ i λ/2, where | TQiIs Q |iDistance to transmitting device T, | QiR | is QiDistance to the receiving device R, | TR | is the distance between the transmitting and receiving devices, λ is the wavelength of the carrier, and the ellipse formed by all points satisfying this condition is the boundary of the ith fresnel zone. The ellipse defined by the boundary of the 1 st Fresnel zone is called the 1 st Fresnel zone, and so on, the ellipse ring defined by the boundary of the ith Fresnel zone and the boundary of the (i + 1) th Fresnel zone is the (i + 1) th Fresnel zone. Fig. 1 shows the equations for the fresnel zone, fresnel boundaries and concentric ellipses.
Fresnel diffraction is a phenomenon of waveform change of received signals caused by sensing that an object enters a first Fresnel area and signals reach a receiving end through diffraction on the surface of the object.
The principle of the invention is as follows: document [8] (Andreas f. molisch.2005.wireless communications.john Wiley and Sons, chicchester, UK.) records that the radio frequency signal is focused on the transceiver device, and is a fresnel zone with an elliptical hierarchical shape in space, and 70% of the signal energy in the first fresnel zone passes through the zone, and the object enters the first fresnel zone, and the diffraction phenomenon dominates, which causes significant signal fading. Different diffraction signal waveforms are formed at the receiving end through different degrees of entering the first Fresnel zone by the human body. When the user lies for breath detection, signals can only reach a receiving end from one side of a human body (unilateral diffraction effect), positions (detection blind areas) where the breath of the human body is difficult to detect are arranged near the boundary of the first Fresnel area, the positions (detection blind areas) where the breath of the human body can be detected are gradually arranged in the first Fresnel area, and the detection effect is stable. When the user sits to perform breath detection, signals can reach the receiving end from two sides of the human body (bilateral diffraction effect), alternative breath detection positions are presented in the first Fresnel region, and the detection effect is unstable. In order to detect the breathing frequency in a given human body position, the user is recommended to lie in the first Fresnel area for detection, and meanwhile, the position of the human body can just fall on the detectable position of the first Fresnel area through the height of the mobile radio frequency transceiver, so that the breathing detection can be carried out on any given human body position. The method is compatible with any signal processing method for the waveform, and can improve the detectability of poor positions after the waveform is processed, and calculate the number of wave crests/wave troughs, namely the breathing frequency of the human body.
The technical scheme provided by the invention is as follows:
a method of contactless breath detection, comprising the steps of:
A. the detection device comprises a pair of radio frequency transceiver devices, at least one antenna is arranged on the pair of radio frequency transceiver devices, one radio frequency transceiver device transmits radio frequency signals with the wavelength of lambda, and the other radio frequency transceiver device receives the transmitted radio frequency signals.
B. The radio frequency transceiver is placed at a certain distance (namely, the LoS distance is set), and under the certain LoS distance, the radio frequency transceiver is taken as an elliptic focus to obtain the position of a first Fresnel zone, wherein the radius r of the first Fresnel zone1Is shown as
The distance between two radio frequency transceiver devices is d1+ d2, the midpoint of a connection line (los) between the two radio frequency transceiver devices is o, d1 is the distance from one of the radio frequency transceiver devices to the midpoint, d2 is the distance from the other radio frequency transceiver device to the midpoint o, and h is the distance from a position of the object in the first fresnel region on the perpendicular bisector to the midpoint o, as shown in fig. 2.
B1. Quantitatively describing the degree of entering the first Fresnel area, defining a unilateral clearance, and obtaining an object which can not diffract a passing signal on one side, wherein the distance from the object to the middle vertical line of the first Fresnel area from LoS is h, and the radius of the first Fresnel area is r1. The unilateral clearance is expressed as:
if both sides of the object have diffractive effects, defining bilateral frontal clearance
And rear clearance
Wherein h isfrontAnd hbackRespectively representing the distance, r, of the leading edge and the trailing edge from the perpendicular bisector of the LoS when an object enters the first Fresnel zone1Still a fresnel zone radius, the clearance reflects where the object is located in the first fresnel zone. Wherein the front clearance and the rear clearance are relative concepts, and the front clearance and the rear clearance are used for distinguishing objects on different two sides of the first Fresnel zone. In one embodiment referred to as front clearance and in another embodiment may be referred to as rear clearance. Distance between the side of the front clearance andthe distance on the side of the back clearance has a different sign, wherein the distance on one side is positive and the distance on the other side is negative, and vice versa.
B2. The diffraction parameter may be expressed as a change in clearance
Similarly, the diffraction parameter in bilateral diffraction is
And
B3. integration of diffraction signals at the receiver
In the case of single-sided diffraction, the signal amplitude is expressed as
GainDiff＝20log|F(v)|
Integration by diffraction under bilateral diffraction
In the case of double-sided diffraction, the amplitude of the signal received at the receiver is represented without considering noise
GainDiff＝20log|F(vfront)+F(vback)|
Wherein, the integral formula obtains a complete waveform, and the corresponding position is intercepted, so that the respiratory amplitude of the corresponding position can be obtained.
C. Scenarios for lying and sitting breath detection
The receiving and sending equipment is placed at an approximate horizontal position with the chest of the human body, and the height of the receiving and sending equipment is the same. The fluctuation of the chest during the respiration process of a human body is imagined to be a cylinder-like body with periodic and tiny change in volume, the displacement of the respiration signal in the front and back abdomen-back directions is 4.2-5.2mm, the displacement of the outer side is 0.6-1.1mm due to the tiny moving distance of the respiration signal, and the change of the chest position is mapped to the phase change caused by the change of the propagation length of the diffraction signal. The respiration is a segment intercepted on the complete waveform of the first Fresnel zone, the position of the respiration represents the intercepted position, and obvious fluctuation can be generated only when interception is carried out in a monotone zone, otherwise, the fluctuation is weak, and the detection effect is poor. This rule can be observed with reference to fig. 5 and 6.
C1. Aiming at the breathing detection when a scene (1) lies, adjusting the height of the transceiver so as to enable a human body to enter different positions of a first Fresnel zone, obtaining different breathing amplitude sizes according to a single-side diffraction amplitude calculation method in the step B3, and calibrating a detectable area and an undetectable area, wherein as shown in figure 7, the position near the boundary of the first Fresnel zone is an undetectable area, most of the inside of the first Fresnel zone is a detectable area, and through the identification and judgment of waveforms, a threshold value of the detectable amplitude is defined, and if the detection effect is not good, namely the detection effect is smaller than the threshold value, the height of a motor device of a base of the transceiver can be adjusted up and down to reach the detectable position;
C2. aiming at the scene (2) of sitting respiration detection, adjusting the position of a human body seat to enable the degree of entering the first Fresnel to be different, and calibrating regions where respiration can be detected and regions where respiration is difficult to detect according to the bilateral diffraction amplitude calculation method in the step B3;
D. and calculating the respiratory frequency, namely preprocessing the original amplitude signal (including smoothing filtering and noise reduction), and extracting frequency domain information of the signal by using a Fast Fourier Transform (FFT) technology, namely the number of peaks/troughs, wherein the number of the peaks/troughs is divided by time to obtain the respiratory frequency. Those skilled in the art will understand that conventional signal processing methods, such as smoothing filtering and noise reduction, fast fourier transform, peak/trough search, etc., can be used to extract frequency domain information of CSI information, so as to obtain the number of peaks/troughs, and by counting the peaks/troughs, the respiratory frequency per unit time can be obtained.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a method for detecting respiration, which utilizes radio frequency signals to detect human respiration, can calibrate a detectable position and a detection blind area according to the respiration detection of a human body in different scenes, and can realize the human respiration detection at any given position by adjusting a radio frequency transceiving position.
The technical scheme provided by the invention can be applied to two typical scenes: firstly, when a human body lies, the receiving and sending equipment is placed to enable the human body to shield the LoS, and any person can realize breathing detection; secondly, when the human body sits, the position of the human body, which can be detected by breathing, is calibrated, and then breathing detection can be realized by adjusting the position of the receiving and sending equipment. Therefore, the technical scheme provided by the invention can solve the problem of how to realize optimal breath detection when a human body is positioned in the middle of the transceiver device and even blocks LoS. In addition, as the invention does not need to carry or wear any equipment by human body, the technical scheme provided by the invention has the advantages of noninvasiveness, convenience and low cost, and the radio frequency signal (such as WiFi) is widely existed in families, thus having outstanding benefit in the field of household breath detection.
Drawings
FIG. 1 shows equations for a Fresnel zone, Fresnel boundaries and a homofocal ellipse;
FIG. 2 is a simplified schematic diagram of an object within a Fresnel zone;
FIG. 3 is a simplified schematic illustration of the fore and aft clearances;
fig. 4 is a schematic flow chart of a method for monitoring human respiration according to an embodiment of the present invention.
FIG. 5 is a graph showing the amplitude of the received signal for both the single-sided and double-sided diffraction cases.
Fig. 6 is a schematic diagram of the extraction of the breathing amplitude.
Fig. 7 is an effect thermodynamic diagram of a lying breathing test.
Fig. 8 is a thermodynamic diagram of the effect of a breath test while sitting.
Detailed Description
The invention will be further described by way of examples, without in any way limiting the scope of the invention, with reference to the accompanying drawings.
The invention provides a non-contact respiration detection method, which is characterized in that a radio frequency signal is utilized to detect human respiration, different postures of a person to be detected in lying or sitting are realized according to the position of a wireless radio frequency signal transceiving device, the detectable position of the human respiration in a first Fresnel zone is calibrated, and the position of the device is adjusted to detect the respiration of any human body. The specific embodiment of the invention is as follows:
A. the detection device comprises a pair of transceiving equipment (the equipment can be a notebook computer, a MiniPC and any equipment supporting RF signal transceiving), at least one antenna (the antenna is a vertically excited omnidirectional antenna and is vertically placed on the ground) is arranged on the transceiving equipment, and the transmitting radio frequency signal has the wavelength of lambda.
B. The radio frequency transceiver is placed at a certain distance (namely, the LoS distance is set), the radio frequency transceiver is taken as an elliptic focus at the certain LoS distance, and the position of a first Fresnel zone and the radius r of the first Fresnel zone can be obtained according to the wavelength lambda of a transmitted radio frequency signal1Is shown as
By determining how far the object enters the first fresnel zone, B1-B3, the corresponding perceived signal can be calculated.
B1. Quantitatively characterizing the extent of entry into the first Fresnel zone, defining a unilateral clearance
If both sides of the object have diffractive effects, defining bilateral frontal clearance
And rear clearance
The clearance reflects the position of the object in the first Fresnel zoneThe position of (a). FIG. 3 is a simplified schematic illustration of the fore and aft clearances.
B2. The diffraction parameter may be expressed as a change in clearance
Similarly, the diffraction parameter in bilateral diffraction is
And
B3. integration of diffraction signals at the receiver
In the case of single-sided diffraction, the signal amplitude is expressed as
GainDiff＝20log|F(v)|
Integration by diffraction under bilateral diffraction
In the case of double-sided diffraction, the signal amplitude is expressed as
GainDiff＝20log|F(vfront)+F(vback)|
Wherein, the integral formula obtains a complete waveform, and the corresponding position is intercepted, so that the respiratory amplitude of the corresponding position can be obtained.
FIG. 5 is a graph of signal amplitude obtained from the single-sided and double-sided diffraction calculation formulas (where the left side is the single-sided diffraction case and the right side is the double-sided diffraction case).
C. Scenario for lying and sitting breath detection:
fig. 6 shows the amplitude of the extracted respiratory signal in two scenarios. Wherein the abscissa is time and the ordinate is amplitude.
C1. Aiming at the breathing detection of a scene (1) when lying, the receiving and sending set height is adjusted so that the positions of human bodies entering the first Fresnel zone are different, different breathing amplitudes are obtained, and a detectable area and an undetectable area are calibrated;
C2. for the scene (2) of sitting breath detection, the position of the human body seat is adjusted, so that the degree of entering the first fresnel is different, the area where the breath can be detected and the area where the breath is difficult to detect are calibrated, and as shown in fig. 8, the positions where the detection effect is good or bad appear alternately.
D. And (2) calculating the respiratory frequency, namely preprocessing the original amplitude signal (including smoothing filtering and noise reduction), and extracting frequency domain information of the signal by using a Fast Fourier Transform (FFT) technology, namely the number of peaks and troughs to obtain the respiratory frequency. Those skilled in the art will understand that conventional signal processing methods, such as smoothing filtering and noise reduction, fast fourier transform, peak/trough search, etc., can be used to extract frequency domain information of CSI information, so as to obtain the number of peaks/troughs, and by counting the peaks/troughs, the respiratory frequency per unit time can be obtained.
The following examples use a WiFi signal with a center frequency of 5.24GHz as the radio frequency signal, the wavelength λ of which is 5.725 cm; the MiniPC carrying the WiFi Intel 5300 network card is used as a receiving and transmitting device, and the receiving and transmitting devices are respectively provided with an omnidirectional antenna.
In this embodiment, a pair of transceiver devices is placed in a 5mx4m room, the transceiver devices are spaced by 1m, the position of the transceiver device is moved in a breathing detection scene of lying and sitting, the breathing detectability can be obtained at any fixed position, and the breathing frequency of a human body is output at a good detection position.
Taking a room of 5mx4m as an example, according to the respiration detection method provided by the invention, the following steps are executed:
A. placing the receive antenna on the RF receive device (MiniPC) vertically above ground, the location of the device being marked P1; placing the transmit antenna on the router of the RF transmitting device (TP-Link WDR5300 router) vertically above ground, the location of the device being labeled P2; setting the distance between P1 and P2 to be 1 m;
B. the radio frequency transceiver is placed at a certain distance (namely, a LoS distance is set), and under the certain LoS distance (namely, the distance between P1 and P2), the radio frequency transceiver is taken as an elliptic focus, and according to the wavelength lambda being 5.725cm, the position of a first Fresnel zone can be obtained, wherein the radius r of the first Fresnel zone is1Is shown as
By determining how far the object enters the first fresnel zone, B1-B3, the corresponding perceived signal can be calculated.
B1. Quantitatively characterizing the extent of entry into the first Fresnel zone, defining a unilateral clearance
If both sides of the object have diffractive effects, defining bilateral frontal clearance
And rear clearance
The clearance reflects where the object is located in the first fresnel zone.
B2. The diffraction parameter may be expressed as a change in clearance
Similarly, the diffraction parameter in bilateral diffraction is
And
B3. integration of diffraction signals at the receiver
In the case of single-sided diffraction, the signal amplitude is expressed as
GainDiff＝20log|F(v)|
Integration by diffraction under bilateral diffraction
In the case of double-sided diffraction, the signal amplitude is expressed as
GainDiff＝20log|F(vfront+vback)|
C. The scene is the position of any given human body (for example, the position of the human body does not change), and the position of the RF transceiver is adjusted to realize respiration detection; scenario two is the position of any given RF transceiver (e.g., the positions of the two RF transceivers do not change), demarcating the position where human breath can be detected; performing C1 or C2 for different scenes, respectively:
C1. aiming at the breathing detection when a scene is lying, the receiving and sending set height is adjusted so that the positions of human bodies entering the first Fresnel zone are different, different breathing amplitude sizes are obtained, and a detectable area and an undetectable area are calibrated;
specifically, the distance from the human body to the perpendicular bisector of the line connecting the transceiver device when the human body enters the first fresnel zone is taken as a measurement:
(a) the breathing of the human body is difficult to detect at the boundary of the first fresnel zone (u is-1 and u is-0.85), and the breathing measurement can be directly carried out when the human body enters deeper (u is-0.5) or clings to the LoS (u is 0) or even blocks the LoS.
(b) The human body can realize the same detection effect when lying on the back and lying on the front, and the effect is slightly worse than the other two postures when lying on the side because the amplitude of the chest is relatively small.
C2. And (3) aiming at the second scene, sitting breath detection, adjusting the position of the human body seat to enable the degree of entering the first Fresnel to be different, and calibrating the area in which breath can be detected and the area in which breath is difficult to detect. In this embodiment, taking the perpendicular bisector of the transceiver line as an example, the best detection region appears in (u)front-0.85), and the like; the area in which breathing is difficult to detect appears (u)front1) and the like. In the area between the two locations, the detection effect is also between the two. The skilled person will be able to set different thresholds for determining the detectable area and the undetectable area, depending on different circumstances, such as measurement accuracy, measurement speed, etc.
D. And (2) calculating the respiratory frequency, namely preprocessing the original amplitude signal, firstly performing smoothing processing, secondly preprocessing the original amplitude signal by using a Hamplel filter with the window size of 5 seconds and a moving average method with the window size of 20 seconds, and then extracting frequency domain information of the signal by using a Fast Fourier Transform (FFT) technology, namely the number of peaks/troughs to obtain the respiratory frequency. Fig. 4 is a schematic flow chart of a method for monitoring human respiration according to an embodiment of the present invention.
The invention also includes the following embodiments:
1. a method for identifying a breath detection region, comprising:
constructing a first Fresnel zone by taking the position of the sending equipment and the position of the receiving equipment as elliptic focuses, taking the distance between the position of the sending equipment and the position of the receiving equipment as a focal distance and according to the wavelength of a radio-frequency signal sent by the sending equipment;
calculating the amplitudes of the signals when the human body enters different positions of the first Fresnel zone according to different clearances;
identifying detectable and undetectable regions in the breath detection region based on the calculated magnitudes of the amplitudes of the signals at the different locations.
2. The method of embodiment 1 wherein the clearance is a distance between a human body and a line-of-sight (LOS) transmission path of the transmitting device and the receiving device.
3. The method of embodiment 2 wherein when said body is seated for breath testing, signals are diffracted through both sides of the body, said clearance comprising a front clearance and a rear clearance, wherein said front clearance and said rear clearance are on different sides of said LOS transmission path and are respectively represented by different signs.
4. The method of embodiment 3, wherein calculating amplitudes of the signals caused by respiratory motion as a human body enters different locations of a first Fresnel zone further comprises:
when a human body lies for breath detection, signals can only be diffracted from one side of the human body to reach a receiving end:
diffraction integration is carried out aiming at the clearance to obtain a complete waveform of a first Fresnel zone;
according to the breathing position of the human body, obtaining the amplitude of the signal caused by breathing motion when the human body enters different positions of the first Fresnel zone;
when a human body sits to perform breath detection, signals can be diffracted from two sides of the human body to reach a receiving end:
diffraction integration is carried out on the front clearance and the rear clearance respectively, and a complete waveform of the first Fresnel zone is obtained according to the combination of the two integration;
and obtaining the amplitude of the signal caused by the breathing motion when the human body enters different positions of the first Fresnel zone according to the breathing position of the human body.
5. The method of embodiment 3, wherein:
when a human body sits to perform respiration detection, the signals are diffracted and pass through two sides of the human body, the calculated amplitude is changed alternately, and the detectable area and the undetectable area appear alternately correspondingly;
when a human body lies for respiratory detection, the signal is diffracted and passes through one side of the human body, and the calculated amplitude is monotonously changed, wherein the amplitude is the minimum near the boundary of the first Fresnel zone and is an undetectable area; and the farther away from the first fresnel zone and the closer to the LOS transmission path, the larger the amplitude, which is a detectable region.
6. A method for breath detection, comprising:
receiving a radio frequency signal sent by sending equipment;
processing the received radio frequency signal to obtain a processed signal;
if the amplitude of the processed signal is less than the threshold value:
constructing a first Fresnel zone by taking the position of the sending equipment and the position of the receiving equipment as elliptic focuses, taking the distance between the position of the sending equipment and the position of the receiving equipment as a focal distance and according to the wavelength of a radio-frequency signal sent by the sending equipment;
calculating the amplitudes of the signals when the human body enters different positions of the first Fresnel zone according to different clearances;
identifying detectable and undetectable regions in a breath detection region from the calculated magnitudes of the amplitudes of the signals at the different locations;
adjusting the heights/positions of the transmitting device and the receiving device with respect to the detectable area and the undetectable area so that the human body is in the detectable area;
and monitoring the respiration of the human body according to the processed signals.
7. The method of embodiment 6, wherein processing a received radio frequency signal further comprises:
and carrying out smooth filtering and noise reduction on the received radio frequency signals, and extracting frequency domain information by utilizing fast Fourier transform so as to obtain the number of wave crests/wave troughs and determine the respiratory frequency.
8. The method of embodiment 6 wherein the clearance is a distance between a human body and a line-of-sight (LOS) transmission path of the transmitting device and the receiving device.
9. The method of embodiment 8 wherein when said person is seated for breath testing, signals are diffracted through both sides of the body, said clearance comprising a front clearance and a rear clearance, wherein said front clearance and said rear clearance are on different sides of said LOS transmission path and are respectively represented by different signs.
10. The method of embodiment 9, wherein calculating amplitudes of the signals caused by respiratory motion as a human body enters different locations of a first fresnel zone further comprises:
when a human body lies for breath detection, signals can only be diffracted from one side of the human body to reach a receiving end:
diffraction integration is carried out aiming at the clearance to obtain a complete waveform of a first Fresnel zone;
according to the breathing position of the human body, obtaining the amplitude of the signal caused by breathing motion when the human body enters different positions of the first Fresnel zone;
when a human body sits to perform breath detection, signals can be diffracted from two sides of the human body to reach a receiving end:
diffraction integration is carried out on the front clearance and the rear clearance respectively, and a complete waveform of the first Fresnel zone is obtained according to the combination of the two integration;
and obtaining the amplitude of the signal caused by the breathing motion when the human body enters different positions of the first Fresnel zone according to the breathing position of the human body.
11. The method of embodiment 8, wherein:
when a human body sits to perform respiration detection, the signals are diffracted and pass through two sides of the human body, the calculated amplitude is changed alternately, and the detectable area and the undetectable area appear alternately correspondingly;
when a human body lies for respiratory detection, the signal is diffracted and passes through one side of the human body, and the calculated amplitude is monotonously changed, wherein the amplitude is the minimum near the boundary of the first Fresnel zone and is the undetectable zone; and the farther away from the first fresnel zone and the closer to the LOS transmission path, the larger the amplitude, the detectable region.
12. An apparatus for identifying a breath detection zone configured to perform the method of any of embodiments 1-5.
13. An apparatus for breath detection configured to perform the method according to any of embodiments 6-11.
14. A computer-readable storage medium storing instructions configured for execution by a processor to cause a computer to perform the method of any of embodiments 1-5.
15. A computer-readable storage medium storing instructions configured for execution by a processor to cause a computer to perform the method of any of embodiments 6-11.
It is noted that the disclosed embodiments are intended to aid in further understanding of the invention, but those skilled in the art will appreciate that: various substitutions and modifications are possible without departing from the spirit and scope of the invention and appended claims. Therefore, the invention should not be limited to the embodiments disclosed, but the scope of the invention is defined by the appended claims.
Claims (8)
1. A method for identifying a breath detection region, comprising:
constructing a first Fresnel zone by taking the position of the sending equipment and the position of the receiving equipment as elliptic focuses, taking the distance between the position of the sending equipment and the position of the receiving equipment as a focal distance and according to the wavelength of a radio-frequency signal sent by the sending equipment;
calculating the amplitude of the signal caused by breathing motion when the human body enters different positions of the first Fresnel zone according to the clearance of the human body at different positions, wherein the clearance is the ratio of the distance between the human body and a sight line transmission path (LOS transmission path) of the sending device and the receiving device to the radius of the first Fresnel zone;
identifying detectable and undetectable regions in a breath detection region from the calculated magnitudes of the amplitudes of the signals at the different locations, wherein:
when a human body sits to perform respiration detection, the signals are diffracted and pass through two sides of the human body, the calculated amplitude is changed alternately, and the detectable area and the undetectable area appear alternately correspondingly;
when a human body lies for breathing detection, the signal is diffracted from one side of the human body, the calculated amplitude is changed monotonously, wherein the amplitude is the smallest near the boundary of the first Fresnel zone and is the undetectable area, and the farther the distance from the first Fresnel zone is and the closer the distance from the LOS transmission path is, the larger the amplitude is, the detectable area is.
2. The method of claim 1, wherein when said person is seated for breath testing, signals are diffracted through both sides of the body, said clearance including a front clearance and a rear clearance, wherein said front clearance and said rear clearance are on different sides of said LOS transmission path and are respectively represented by different signs.
3. The method of claim 2, wherein calculating amplitudes of the signals caused by respiratory motion as a human body enters different locations of a first fresnel zone further comprises:
when a human body lies for breath detection, signals can only be diffracted from one side of the human body to reach a receiving end:
diffraction integration is carried out aiming at the clearance to obtain a complete waveform of the first Fresnel region;
according to the breathing position of the human body, obtaining the amplitude of the signal caused by breathing motion when the human body enters different positions of the first Fresnel zone;
when a human body sits to perform breath detection, signals can be diffracted from two sides of the human body to reach a receiving end:
diffraction integration is carried out on the front clearance and the rear clearance respectively, and a complete waveform of the first Fresnel zone is obtained according to the combination of the two integration;
and obtaining the amplitude of the signal caused by the breathing motion when the human body enters different positions of the first Fresnel zone according to the breathing position of the human body.
4. A method for breath detection, comprising:
receiving a radio frequency signal sent by sending equipment;
processing the received radio frequency signal to obtain a processed signal;
if the amplitude of the processed signal is less than the threshold value:
constructing a first Fresnel zone by taking the position of the sending equipment and the position of the receiving equipment as elliptic focuses, taking the distance between the position of the sending equipment and the position of the receiving equipment as a focal distance and according to the wavelength of a radio-frequency signal sent by the sending equipment;
calculating the amplitude of the signal caused by breathing motion when the human body enters different positions of the first Fresnel zone according to the clearance of the human body at different positions, wherein the clearance is the ratio of the distance between the human body and a sight line transmission path (LOS transmission path) of the sending device and the receiving device to the radius of the first Fresnel zone;
identifying detectable and undetectable regions in a breath detection region from the calculated magnitudes of the amplitudes of the signals at the different locations, wherein:
when a human body sits to perform respiration detection, the signals are diffracted and pass through two sides of the human body, the calculated amplitude is changed alternately, and the detectable area and the undetectable area appear alternately correspondingly;
when a human body lies for breath detection, the signal is diffracted from one side of the human body, the calculated amplitude is monotonously changed, wherein the amplitude is the smallest near the boundary of the first Fresnel zone and is the undetectable area, and the farther the distance from the first Fresnel zone is and the closer the distance from the LOS transmission path is, the larger the amplitude is, the detectable area is;
adjusting the heights/positions of the transmitting device and the receiving device with respect to the detectable area and the undetectable area so that the human body is in the detectable area;
and monitoring the respiration of the human body according to the processed signals.
5. The method of claim 4, wherein processing a received radio frequency signal further comprises:
and carrying out smooth filtering and noise reduction on the received radio frequency signals, and extracting frequency domain information by utilizing fast Fourier transform so as to obtain the number of wave crests/wave troughs and determine the respiratory frequency.
6. An apparatus for identifying a breath detection region configured to perform the method of any of claims 1-3.
7. An apparatus for breath detection configured to perform the method of any one of claims 4-5.
8. A computer-readable storage medium storing instructions configured for execution by a processor, the instructions causing a computer to perform the method of any one of claims 1-3.
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