Detection and positioning methods for weak human life signals

Abstract

The present invention discloses a method for detecting weak human life signals, including using an ultra-wideband radar to transmit a high-frequency and high-repetition-rate sub-pulse signal to a target area and receiving a sub-pulse echo signal; performing signal preprocessing on the sub-pulse echo signal; performing fast Fourier transform on the preprocessed signal to obtain the spectrum of the sub-pulse signal; filtering and frequency selecting the spectrum of the sub-pulse signal to obtain the target frequency; and determining the target frequency to complete the detection of weak human life signals. The present invention also discloses a positioning method including the detection method for weak human life signals. Based on repetition rate, frequency agility and corresponding signal processing schemes, the present invention improves the radar's detection and positioning capabilities for weak human life signals behind a medium while reducing the coherent accumulation time; therefore, the present invention can not only realize the detection and positioning of weak human life signals, but also has higher reliability and better accuracy.

Description

Technical Field

[0001] The invention belongs to the technical field of digital signal recognition, and in particular relates to a detection method and a positioning method for weak human life signals. Background Art

[0002] With its advantages such as strong penetration and high resolution, ultra-wideband radar has broad application value and prospects in post-disaster rescue, medical monitoring and other fields.

[0003] Under medium penetration conditions, ultra-wideband signals have frequency-selective amplitude attenuation and phase distortion during propagation (i.e., under the same medium penetration conditions, signals of different frequencies will produce different energy attenuation and phase distortion). However, the existing schemes for detecting human targets behind mediums using ultra-wideband radars and corresponding ultra-wideband signals are schemes that directly use pulse compression technology to perform ultra-wideband synthesis on multi-frequency signals; such schemes do not consider the influence of the above-mentioned frequency-selective amplitude attenuation and phase distortion, resulting in a low signal-to-noise ratio of the ultra-wideband signal synthesized by such schemes, which ultimately weakens the ability of ultra-wideband radars to detect weak life signals, and has poor reliability and accuracy. Summary of the invention

[0004] One of the purposes of the present invention is to provide a method for detecting weak human life signals with good reliability and accuracy.

[0005] A second object of the present invention is to provide a positioning method including the detection method of the weak human life signal.

[0006] The method for detecting weak human life signals provided by the present invention comprises the following steps:

[0007] S1. Use ultra-wideband radar to transmit high-frequency and high-repetition-rate sub-pulse signals to the target area and receive the corresponding sub-pulse echo signals;

[0008] S2. The sub-pulse echo signal obtained in step S1 is subjected to signal preprocessing; the signal preprocessing includes linear trend suppression and clutter suppression;

[0009] S3. The preprocessed signal obtained in step S2 is subjected to a fast Fourier transform to obtain a spectrum of the sub-pulse signal;

[0010] S4. The spectrum of the sub-pulse signal obtained in step S3 is filtered and frequency selected according to the characteristics of the human vital signs signal frequency band to obtain the target frequency;

[0011] S5. Based on the frequency band of the human vital sign signal, the target frequency obtained in step S4 is determined to complete the detection of weak human vital signs.

[0012] The step S1 specifically includes the following steps:

[0013] Ultra-wideband radar is used to transmit N sub-pulse signals with the same frequency to the target area within a pulse period of a stepped frequency signal; the transmitted sub-pulse signal is a high-frequency signal with a frequency higher than the set value;

[0014] The received sub-pulse echo signal is expressed as , which includes parameters t and , t is the time when the radar receives the signal, Time delay for human targets; Frequency for ,in is the initial frequency of the radar, is the frequency step size.

[0015] The step S2 specifically includes the following steps:

[0016] Received sub-pulse echo signal for A one-dimensional vector of , M is the length of slow time;

[0017] The following formula is used for linear trend suppression: In the formula is the sub-pulse echo signal after linear trend suppression; A is the linear trend matrix, and , the first column of A is the linear trend quantity, and the second column of A is the slow time invariant;

[0018] The background cancellation method is used to remove clutter signals, and the echo signal obtained Expressed as ;in, is the background signal.

[0019] The step S3 specifically includes the following steps:

[0020] The echo signal is calculated using the following formula: Perform a fast Fourier transform: In the formula Echo signal No. The complex amplitude of a frequency spectrum line; m is the serial number of the slow time sampling point.

[0021] The step S4 specifically comprises the following steps:

[0022] A. According to the characteristics of the frequency band of human vital signs signal, set the cutoff frequency range of the bandpass filter;

[0023] B. filtering the spectrum data obtained in step S3 using a bandpass filter according to the cutoff frequency range set in step A;

[0024] C. For the filtered spectrum data obtained in step B, the following steps are used to perform frequency selection to obtain the target frequency:

[0025] C1. Perform peak search on the filtered spectrum data obtained in step B, and obtain the frequency corresponding to the peak with the top NN energy ranking as the candidate target frequency;

[0026] C2. Select the candidate target frequency with the largest energy from the candidate target frequencies obtained in step C1 as the current candidate target frequency ;

[0027] C3. Based on the current candidate target frequency , get the candidate target fundamental frequency interval , where u is the set error value;

[0028] C4. Determine the remaining candidate target frequencies:

[0029] If the remaining candidate target frequencies are not in the candidate target fundamental frequency interval, the current candidate target frequency As the final target frequency ;

[0030] If there is only one candidate target frequency in the candidate target fundamental frequency interval, the candidate target frequency is used as the current candidate target frequency. , and delete the previous current candidate target frequency, and return to step C3 for the next round of iteration;

[0031] If there are more than one candidate target frequency in the candidate target fundamental frequency interval among the remaining candidate target frequencies, the candidate target frequency with the largest energy is selected as the current candidate target frequency. , and delete the previous current candidate target frequency and other candidate target frequencies in the candidate target fundamental frequency interval, and return to step C3 for the next round of iteration.

[0032] The step S5 specifically includes the following steps:

[0033] Based on the frequency band of the human vital sign signal, the target frequency obtained in step S4 is determined:

[0034] If the target frequency is within the set frequency band of human vital signs signal, it is determined that human vital signals are detected, and the detection of weak human vital signals is completed;

[0035] If the target frequency is not within the set human vital sign signal frequency band, the frequency of the sent sub-pulse signal is judged:

[0036] If the frequency of the transmitted sub-pulse signal does not reach the set minimum transmission frequency, return to step S1, reduce the frequency of the transmitted sub-pulse signal according to the set rule, and perform the next round of detection;

[0037] If the frequency of the transmitted sub-pulse signal has reached the set minimum transmission frequency, it is determined that no human life signal is detected.

[0038] The present invention also provides a positioning method including the detection method of the weak human life signal, comprising the following steps:

[0039] (1) Using ultra-wideband radar, it transmits a stepped frequency signal with high range resolution to the target area and receives the corresponding stepped frequency echo signal;

[0040] (2) performing signal preprocessing on the stepped frequency echo signal received in step (1); the signal preprocessing includes linear trend suppression, pulse compression, clutter suppression and medium parameter compensation;

[0041] (3) performing a fast discrete Fourier transform on the preprocessed signal obtained in step (2) to obtain a range Doppler matrix of the sub-pulse signal;

[0042] (4) In the range Doppler matrix obtained in step (3), target detection is performed on the range data corresponding to the target frequency obtained by the method for detecting weak human life signals to complete target positioning.

[0043] The step (1) specifically comprises the following steps:

[0044] An ultra-wideband radar is used to transmit NN stepped frequency sub-pulses with different frequencies to the target area within a stepped frequency signal pulse repetition period; the transmitted stepped frequency signal is a stepped frequency signal with high range resolution;

[0045] The frequency received after the medium penetrates at time t is The sub-pulse echo signal is expressed as , Include Parameters and t, Time delay for human targets; Frequency for ,in is the initial frequency of the radar, is the frequency step size.

[0046] The step (2) specifically comprises the following steps:

[0047] The following formula is used for linear trend suppression: In the formula is the sub-pulse echo signal after linear trend suppression; B is the linear trend matrix, and , the first column of B is the linear trend quantity, and the second column of B is the slow time invariant;

[0048] use The point fast discrete inverse Fourier transform is used to compress the sub-pulse echo signal after linear trend suppression; at time t, the sub-pulse echo signal after pulse compression is compressed. Stepped frequency echo data of range gates Expressed as Where n is the serial number of the step frequency signal; The frequency of the step frequency signal after linear trend suppression is The sub-pulse echo signal;

[0049] The background cancellation method is used to remove clutter signals, and the echo signal obtained Expressed as , is the background clutter signal;

[0050] The refraction angle is used to approximate the wall delay compensation algorithm to compensate for the medium parameters. The compensated delay Expressed as In the formula is the thickness of the homogeneous medium; is the relative dielectric constant of the homogeneous medium, c is the speed of light;

[0051] Finally, the first The echo signal of a range gate is expressed as .

[0052] The step (3) specifically comprises the following steps:

[0053] Echo signal It forms a two-dimensional matrix containing the range and slow-time echo channels. Matrix RTM, where is the number of fast time sampling points, used to represent the distance dimension; is the number of slow time sampling points, used to represent the slow time dimension; , M is the number of slow-time sampling points obtained by the high-repetition-rate single-frequency signal within the same sampling time as the low-repetition-rate step-frequency signal;

[0054] For the echo matrix RTM, along the slow time dimension Point fast discrete Fourier transform is performed to obtain the range Doppler matrix RDM; is the number of frequency sampling points, used to represent the frequency dimension;

[0055] In the range-Doppler matrix RDM, The distance gate, The value of the frequency spectrum Expressed as In the formula It is the sequence number of the slow time sampling point.

[0056] The step (4) specifically comprises the following steps:

[0057] In the range Doppler matrix RDM, the frequency is Distance to data Perform target detection and obtain the target distance:

[0058] For a single-sided spectrum, the target frequency line and target frequency The corresponding relationship is expressed as Where PRF is the pulse repetition frequency;

[0059] The unit average constant false alarm algorithm is used to detect the range data Range and obtain the target distance d: , is the processing function of the unit average constant false alarm algorithm;

[0060] The following rules are used for target detection:

[0061] If the ultra-wideband radar used is a single-transmit and single-receive system, the target distance d is the final positioning result;

[0062] If the ultra-wideband radar used is a multiple-transmit multiple-receive system, a positioning algorithm is used to obtain the final positioning result; the positioning algorithm includes elliptical positioning and triangular positioning.

[0063] The detection method and positioning method of weak human life signals provided by the present invention are based on repetition rate, frequency agility and corresponding signal processing schemes, which improve the radar's detection and positioning capabilities of weak human life signals behind a medium while reducing the coherent accumulation time; therefore, the present invention can not only realize the detection and positioning of weak human life signals, but also has higher reliability and better accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 The figure is a schematic diagram of the method flow of the detection method of the present invention.

[0065] Figure 2 The figure is a flow chart of the positioning method of the present invention.

[0066] Figure 3This is a schematic diagram of a one-dimensional slow-time image of a high repetition rate sub-pulse obtained by the detection method of the present invention according to an embodiment of the present invention.

[0067] Figure 4 Schematic diagram of a one-dimensional slow-time image of a stepped frequency signal obtained by a conventional detection method according to an embodiment of the present invention.

[0068] Figure 5 Schematic diagram of a high repetition rate sub-pulse spectrum obtained by the detection method of the present invention according to an embodiment of the present invention.

[0069] Figure 6 Schematic diagram of the stepped frequency signal spectrum obtained by the conventional detection method according to an embodiment of the present invention.

[0070] Figure 7 Schematic diagram of a range Doppler image of a stepped frequency signal obtained by the positioning method of the present invention according to an embodiment of the present invention.

[0071] Figure 8 Schematic diagram of a one-dimensional range image at a target frequency obtained by the positioning method of the present invention according to an embodiment of the present invention. DETAILED DESCRIPTION

[0072] like Figure 1 The method flow chart of the detection method of the present invention is shown as follows: The detection method of the weak human life signal disclosed in the present invention comprises the following steps:

[0073] S1. Using an ultra-wideband radar, transmitting a high-frequency and high-repetition-rate sub-pulse signal to a target area, and receiving a corresponding sub-pulse echo signal; specifically comprising the following steps:

[0074] Conventional stepped-frequency ultra-wideband radar transmits within one pulse repetition period. N In order to avoid the influence of frequency selective amplitude attenuation and phase distortion of ultra-wideband signals in the medium propagation process and reduce the coherent accumulation time, the present invention adopts ultra-wideband radar to transmit N sub-pulse signals with the same frequency to the target area within a complete pulse period of the stepped frequency signal in the stage of sensing weak human life signals. In addition, considering that high-frequency signals have more precise detection capabilities at close range and low-frequency signals have a longer detection distance, the transmitted sub-pulse signals are high-frequency signals with a frequency higher than the set value.

[0075] The received sub-pulse echo signal (after medium penetration) is expressed as , which includes parameters t and , t is the time when the radar receives the signal, Time delay for human targets; Frequency for ,in is the initial frequency of the radar, is the frequency step size;

[0076] S2. The sub-pulse echo signal obtained in step S1 is subjected to signal preprocessing; the signal preprocessing includes linear trend suppression and clutter suppression; specifically comprising the following steps:

[0077] Received sub-pulse echo signal for A one-dimensional vector of , M is the length of slow time;

[0078] The following formula is used for linear trend suppression: In the formula is the sub-pulse echo signal after linear trend suppression; A is the linear trend matrix, and , the first column of A is the linear trend quantity, and the second column of A is the slow time invariant;

[0079] In the medium penetration detection scenario, the target signal is submerged in the clutter due to the strong interference of the direct coupled wave and the background clutter. Therefore, in order to obtain the target signal, it is necessary to suppress the clutter of the radar echo. The background cancellation method is used to remove the clutter signal, and the echo signal obtained is Expressed as ;in, is the background signal;

[0080] S3. The preprocessed signal obtained in step S2 is subjected to a fast Fourier transform to obtain a spectrum of a sub-pulse signal; specifically comprising the following steps:

[0081] The echo signal is calculated using the following formula: Perform a fast Fourier transform: In the formula Echo signal No. The complex amplitude of the frequency spectrum line; m is the serial number of the slow time sampling point;

[0082] S4. The spectrum of the sub-pulse signal obtained in step S3 is filtered and frequency selected according to the characteristics of the frequency band of the human vital signs signal to obtain the target frequency; specifically comprising the following steps:

[0083] A. According to the characteristics of the frequency band of human vital signs signal, set the cutoff frequency range of the bandpass filter;

[0084] In specific implementation, since the human heartbeat signal is almost impossible to be detected under the low signal-to-noise ratio condition of medium penetration, only the spectrum data of the frequency range of the human breathing frequency band is concerned; generally, the frequency range of human breathing is 0.2~0.5Hz, so the cut-off frequency range of the bandpass filter can be set to 0.1~5Hz;

[0085] B. filtering the spectrum data obtained in step S3 using a bandpass filter according to the cutoff frequency range set in step A;

[0086] C. For the filtered spectrum data obtained in step B, the following steps are used to perform frequency selection to obtain the target frequency:

[0087] C1. Perform peak search on the filtered spectrum data obtained in step B, and obtain the frequency corresponding to the peak with the top NN energy ranking as the candidate target frequency;

[0088] C2. Select the candidate target frequency with the largest energy from the candidate target frequencies obtained in step C1 as the current candidate target frequency ;

[0089] C3. Based on the current candidate target frequency , get the candidate target fundamental frequency interval , where u is the set error value (preferably 0.1);

[0090] C4. Determine the remaining candidate target frequencies:

[0091] If the remaining candidate target frequencies are not in the candidate target fundamental frequency interval, the current candidate target frequency As the final target frequency ;

[0092] If there is only one candidate target frequency in the candidate target fundamental frequency interval, the candidate target frequency is used as the current candidate target frequency. , and delete the previous current candidate target frequency, and return to step C3 for the next round of iteration;

[0093] If there are more than one candidate target frequency in the candidate target fundamental frequency interval among the remaining candidate target frequencies, the candidate target frequency with the largest energy is selected as the current candidate target frequency. , and delete the previous current candidate target frequency and other candidate target frequencies in the candidate target fundamental frequency interval, and return to step C3 for the next round of iteration;

[0094] S5. Based on the human vital signs signal frequency band, the target frequency obtained in step S4 is determined to complete the detection of weak human vital signals; specifically comprising the following steps:

[0095] Based on the frequency band of the human vital sign signal, the target frequency obtained in step S4 is determined:

[0096] If the target frequency is within the set frequency band of human vital signs signal, it is determined that human vital signals are detected, and the detection of weak human vital signals is completed; the set frequency band of human vital signs signal is generally set to 0.2~0.5Hz;

[0097] If the target frequency is not within the set human vital sign signal frequency band, the frequency of the sent sub-pulse signal is judged:

[0098] If the frequency of the transmitted sub-pulse signal does not reach the set minimum transmission frequency, return to step S1, reduce the frequency of the transmitted sub-pulse signal according to the set rule, and perform the next round of detection;

[0099] If the frequency of the transmitted sub-pulse signal has reached the set minimum transmission frequency, it is determined that no human life signal is detected.

[0100] like Figure 2 The method flow chart of the positioning method of the present invention is shown as follows: the positioning method including the detection method of the weak human life signal disclosed in the present invention comprises the following steps:

[0101] (1) Using an ultra-wideband radar, a stepped frequency signal with high range resolution is transmitted to the target area, and a corresponding stepped frequency echo signal is received; the specific steps include:

[0102] An ultra-wideband radar is used to transmit NN stepped frequency sub-pulses with different frequencies to the target area within a stepped frequency signal pulse repetition period; the transmitted stepped frequency signal is a stepped frequency signal with high range resolution;

[0103] The frequency received after the medium penetrates at time t is The sub-pulse echo signal is expressed as , Include Parameters and t, Time delay for human targets; Frequency for ,in is the initial frequency of the radar, is the frequency step size;

[0104] (2) performing signal preprocessing on the stepped frequency echo signal received in step (1); the signal preprocessing includes linear trend suppression, pulse compression, clutter suppression and medium parameter compensation; specifically includes the following steps:

[0105] The following formula is used for linear trend suppression: In the formula is the sub-pulse echo signal after linear trend suppression; B is the linear trend matrix, and , the first column of B is the linear trend quantity, and the second column of B is the slow time invariant;

[0106] In order to improve the distance resolution of the echo signal and obtain the distance dimension information, it is necessary to perform pulse compression on the step-frequency pulse train after linear trend suppression; The point fast discrete inverse Fourier transform is used to compress the sub-pulse echo signal after linear trend suppression; at time t, the sub-pulse echo signal after pulse compression is compressed. Stepped frequency echo data of range gates Expressed as Where n is the serial number of the step frequency signal; The frequency of the step frequency signal after linear trend suppression is The sub-pulse echo signal;

[0107] The background cancellation method is used to remove clutter signals, and the echo signal obtained Expressed as , is the background clutter signal;

[0108] In the medium penetration detection scenario, the target position is offset due to the refraction of the electromagnetic wave by the medium. In order to correct the target position, it is necessary to compensate for the additional delay caused by the medium refraction. The refraction angle is used to approximate the wall delay compensation algorithm (the purpose is to improve the calculation efficiency) to compensate for the medium parameters. The compensated delay Expressed as In the formula is the thickness of the homogeneous medium; is the relative dielectric constant of the homogeneous medium, c is the speed of light;

[0109] Finally, the first The echo signal of a range gate is expressed as ;

[0110] (3) Performing a fast discrete Fourier transform on the preprocessed signal obtained in step (2) to obtain a range Doppler matrix of the sub-pulse signal; specifically comprising the following steps:

[0111] Echo signal It forms a two-dimensional matrix containing the range and slow-time echo channels. Matrix RTM, where is the number of fast time sampling points, used to represent the distance dimension; is the number of slow time sampling points, used to represent the slow time dimension; , M is the number of slow-time sampling points obtained by the high-repetition-rate single-frequency signal within the same sampling time as the low-repetition-rate step-frequency signal;

[0112] For the echo matrix RTM, along the slow time dimension Point fast discrete Fourier transform is performed to obtain the range Doppler matrix RDM; is the number of frequency sampling points, used to represent the frequency dimension;

[0113] In the range-Doppler matrix RDM, The distance gate, The value of the frequency spectrum Expressed as In the formula is the serial number of the slow time sampling point;

[0114] (4) In the range Doppler matrix obtained in step (3), target detection is performed on the range data corresponding to the target frequency obtained by the detection method of the weak human life signal to complete target positioning; specifically, the steps include:

[0115] In the range Doppler matrix RDM, the frequency is Distance to data Perform target detection and obtain the target distance:

[0116] For a single-sided spectrum, the target frequency line and target frequency The corresponding relationship is expressed as

[0117] Where PRF is the pulse repetition frequency;

[0118] The unit average constant false alarm algorithm is used to detect the range data Range and obtain the target distance d: , is the processing function of the unit average constant false alarm algorithm;

[0119] The following rules are used for target detection:

[0120] If the ultra-wideband radar used is a single-transmit and single-receive system, the target distance d is the final positioning result;

[0121] If the ultra-wideband radar used is a multiple-transmit multiple-receive system, a positioning algorithm is used to obtain the final positioning result; the positioning algorithm includes elliptical positioning and triangular positioning.

[0122] The method of the present invention is further described below in conjunction with an embodiment:

[0123] The radar adopts a single-transmit and single-receive frequency stepping system with a frequency range of 800M~1.7GHz, 256 frequency points, a pulse repetition frequency of 20Hz, and a high-repetition-rate sub-pulse pulse repetition frequency of Hz. The radar was placed close to a concrete wall with a thickness of about 0.3m and a relative dielectric constant of about 6. The target was 5m away from the radar, and it breathed at a constant speed with a frequency of 0.3Hz and an amplitude of 0.05m. The step frequency signal sampled 200 frames of slow time signal within a sampling time of 10s, and the 800M, 1.25GHz, and 1.7GHz high repetition rate sub-pulses each sampled The frame slow time signal, the simulation data added Gaussian noise to make its signal-to-noise ratio -30dB, the method of the present invention is compared with the traditional frequency stepping system radar, the comparison results are as follows Figure 3~Figure 8 As shown:

[0124] Figure 3 and Figure 4 These are the preprocessed one-dimensional slow-time image of the 1.7 GHz high-repetition-rate sub-pulse and the one-dimensional slow-time image of the stepped-frequency signal obtained during the weak human life signal perception stage. It can be seen that the target breathing trend has been completely submerged by the noise.

[0125] Figure 5 and Figure 6 They are the spectra of 1.7 GHz high repetition rate sub-pulse and step frequency signal in the stage of weak human life signal perception. Figure 5 It can be seen that the target frequency 0.3Hz is clearly prominent in the spectrum, while Figure 6 The target frequency is submerged in the noise, which shows that the proposed method has better and faster perception ability for weak life signals.

[0126] Figure 7 The range Doppler image of the stepped frequency signal obtained during the weak human life signal positioning stage is Figure 7 The target's location cannot be accurately determined.

[0127] However, if Figure 8 As shown in FIG. 1 , based on the target frequency of 0.3 Hz obtained in the weak human life signal perception stage, the one-dimensional range image at the target frequency of 0.3 Hz can be extracted from the range Doppler image, and then the unit average constant false alarm detection is used to obtain the target location at 5 m (e.g. Figure 8 The median coordinate is The detection results are consistent with the simulation conditions. The simulation results show that the method of the present invention has a better ability to detect weak human life signals.

Claims

1. A method for detecting weak human life signals, characterized in that The steps include: S1. Use ultra-wideband radar to transmit high-frequency and high-repetition-rate sub-pulse signals to the target area and receive the corresponding sub-pulse echo signals; S2. The sub-pulse echo signal obtained in step S1 is subjected to signal preprocessing; the signal preprocessing includes linear trend suppression and clutter suppression; S3. The preprocessed signal obtained in step S2 is subjected to a fast Fourier transform to obtain a spectrum of the sub-pulse signal; S4. The spectrum of the sub-pulse signal obtained in step S3 is filtered and frequency selected according to the characteristics of the human vital signs signal frequency band to obtain the target frequency; S5. Based on the frequency band of the human vital sign signal, the target frequency obtained in step S4 is determined to complete the detection of weak human vital signs.

2. The method for detecting weak human life signals according to claim 1, characterized in that The step S1 specifically includes the following steps: Ultra-wideband radar is used to transmit N sub-pulse signals with the same frequency to the target area within a pulse period of a stepped frequency signal; the transmitted sub-pulse signal is a high-frequency signal with a frequency higher than the set value; The received sub-pulse echo signal is expressed as , which includes parameters t and , t is the time when the radar receives the signal, Time delay for human targets; Frequency for ,in is the initial frequency of the radar, is the frequency step size.

3. The method for detecting weak human life signals according to claim 2, characterized in that The step S2 specifically includes the following steps: Received sub-pulse echo signal for A one-dimensional vector of , M is the length of slow time; The following formula is used for linear trend suppression: In the formula is the sub-pulse echo signal after linear trend suppression; A is the linear trend matrix, and , the first column of A is the linear trend quantity, and the second column of A is the slow time invariant; The background cancellation method is used to remove clutter signals, and the echo signal obtained Expressed as ;in, is the background signal.

4. The method for detecting weak human life signals according to claim 3, characterized in that The step S3 specifically includes the following steps: The echo signal is calculated using the following formula: Perform a fast Fourier transform: In the formula Echo signal No. The complex amplitude of a frequency spectrum line; m is the serial number of the slow time sampling point.

5. The method for detecting weak human life signals according to claim 4, characterized in that The step S4 specifically comprises the following steps: A. According to the characteristics of the frequency band of human vital signs signal, set the cutoff frequency range of the bandpass filter; B. filtering the spectrum data obtained in step S3 using a bandpass filter according to the cutoff frequency range set in step A; C. For the filtered spectrum data obtained in step B, the following steps are used to perform frequency selection to obtain the target frequency: C1. Perform peak search on the filtered spectrum data obtained in step B and obtain the top energy rankings. The frequency corresponding to the peak value of the bit is taken as the candidate target frequency; C2. Select the candidate target frequency with the largest energy from the candidate target frequencies obtained in step C1 as the current candidate target frequency ; C3. Based on the current candidate target frequency , get the candidate target fundamental frequency interval , where u is the set error value; C4. Determine the remaining candidate target frequencies: If the remaining candidate target frequencies are not in the candidate target fundamental frequency interval, the current candidate target frequency As the final target frequency ; If there is only one candidate target frequency in the candidate target fundamental frequency interval, the candidate target frequency is used as the current candidate target frequency. , and delete the previous current candidate target frequency, and return to step C3 for the next round of iteration; If there are more than one candidate target frequency in the candidate target fundamental frequency interval among the remaining candidate target frequencies, the candidate target frequency with the largest energy is selected as the current candidate target frequency. , and delete the previous current candidate target frequency and other candidate target frequencies in the candidate target fundamental frequency interval, and return to step C3 for the next round of iteration.

6. The method for detecting weak human life signals according to claim 5, characterized in that The step S5 specifically includes the following steps: Based on the frequency band of the human vital sign signal, the target frequency obtained in step S4 is determined: If the target frequency is within the set frequency band of human vital signs signal, it is determined that human vital signals are detected, and the detection of weak human vital signals is completed; If the target frequency is not within the set human vital sign signal frequency band, the frequency of the sent sub-pulse signal is judged: If the frequency of the transmitted sub-pulse signal does not reach the set minimum transmission frequency, return to step S1, reduce the frequency of the transmitted sub-pulse signal according to the set rule, and perform the next round of detection; If the frequency of the transmitted sub-pulse signal has reached the set minimum transmission frequency, it is determined that no human life signal is detected.

7. A positioning method comprising the method for detecting weak human life signals as claimed in any one of claims 1 to 6, characterized in that The steps include: (1) Using ultra-wideband radar, it transmits a stepped frequency signal with high range resolution to the target area and receives the corresponding stepped frequency echo signal; (2) performing signal preprocessing on the stepped frequency echo signal received in step (1); the signal preprocessing includes linear trend suppression, pulse compression, clutter suppression and medium parameter compensation; (3) performing a fast discrete Fourier transform on the preprocessed signal obtained in step (2) to obtain a range Doppler matrix of the sub-pulse signal; (4) In the range Doppler matrix obtained in step (3), target detection is performed on the range data corresponding to the target frequency obtained by the method for detecting weak human life signals to complete target positioning.

8. The positioning method according to claim 7, characterized in that The step (1) specifically comprises the following steps: An ultra-wideband radar is used to transmit NN stepped frequency sub-pulses with different frequencies to the target area within a stepped frequency signal pulse repetition period; the transmitted stepped frequency signal is a stepped frequency signal with high range resolution; The frequency received after the medium penetrates at time t is The sub-pulse echo signal is expressed as , Include Parameters and t, Time delay for human targets; Frequency for ,in is the initial frequency of the radar, is the frequency step size.

9. The positioning method according to claim 8, characterized in that The step (2) specifically comprises the following steps: The following formula is used for linear trend suppression: In the formula It is the sub-pulse echo signal after linear trend suppression; B is the linear trend matrix, and , the first column of B is the linear trend quantity, and the second column of B is the slow time invariant; use The sub-pulse echo signal after linear trend suppression is pulse compressed by fast discrete inverse Fourier transform at t. Stepped frequency echo data of range gates Expressed as Where n is the serial number of the step frequency signal; The frequency of the step frequency signal after linear trend suppression is The sub-pulse echo signal; The background cancellation method is used to remove clutter signals, and the echo signal obtained Expressed as , is the background clutter signal; The refraction angle is used to approximate the wall delay compensation algorithm to compensate for the medium parameters. The compensated delay Expressed as In the formula is the thickness of the homogeneous medium; is the relative dielectric constant of the homogeneous medium, c is the speed of light; Finally, the first The echo signal of a range gate is expressed as .

10. The positioning method according to claim 9, characterized in that The step (3) specifically comprises the following steps: Echo signal It forms a two-dimensional matrix containing the range and slow-time echo channels. Matrix RTM, where is the number of fast time sampling points, used to represent the distance dimension; is the number of slow time sampling points, used to represent the slow time dimension; , M is the number of slow-time sampling points obtained by the high-repetition-rate single-frequency signal within the same sampling time as the low-repetition-rate step-frequency signal; For the echo matrix RTM, along the slow time dimension Point fast discrete Fourier transform is performed to obtain the range Doppler matrix RDM; is the number of frequency sampling points, used to represent the frequency dimension; In the range-Doppler matrix RDM, The distance gate, The value of the frequency spectrum Expressed as In the formula is the serial number of the slow time sampling point; The step (4) specifically comprises the following steps: In the range Doppler matrix RDM, the frequency is Distance to data Perform target detection and obtain the target distance: For a single-sided spectrum, the target frequency line and target frequency The corresponding relationship is expressed as Where PRF is the pulse repetition frequency; The unit average constant false alarm algorithm is used to detect the range data Range and obtain the target distance d: , is the processing function of the unit average constant false alarm algorithm; The following rules are used for target detection: If the ultra-wideband radar used is a single-transmit and single-receive system, the target distance d is the final positioning result; If the ultra-wideband radar used is a multiple-transmit multiple-receive system, a positioning algorithm is used to obtain the final positioning result; the positioning algorithm includes elliptical positioning and triangular positioning.

Images