阅读说明：本技术 一种基于毫米波雷达的动态目标的监测方法 (Dynamic target monitoring method based on millimeter wave radar ) 是由 潘成铭 李文钧 岳克强 程思一 孙洁 刘昊 于 2020-12-31 设计创作，主要内容包括：本发明公开了一种基于毫米波雷达的动态目标的监测方法,包括如下步骤：S1利用毫米波雷达发射线性调频信号,经过回波信号与发射信号混频后得到基带差拍信号；S2对得到的信号进行预处理去除寄生调幅干扰、正交混频镜像干扰等影响信号质量的问题；S3利用DFT对含有目标距离信息的差拍信号进行频率的估计,继而转化成距离的估计而实现目标的距离参数测量；S4多个毫米波雷达分布式组网实现目标的三维空间定位。本发明提供的方法能够用于动态目标的监测,通过毫米波雷达获取的原始数据经过预处理、DFT计算和分布式组网实现动态目标的监测方法可用于老人、婴幼儿、精神病患者、大面积烧伤等特殊人群进行体征动态监护。(The invention discloses a dynamic target monitoring method based on a millimeter wave radar, which comprises the following steps: s1, transmitting a linear frequency modulation signal by using a millimeter wave radar, and mixing an echo signal with the transmitted signal to obtain a baseband beat signal; s2, preprocessing the obtained signal to remove the problems of influence on signal quality such as parasitic amplitude modulation interference, quadrature mixing image interference and the like; s3, carrying out frequency estimation on the beat signal containing the target distance information by using DFT, and then converting the frequency estimation into distance estimation to realize the distance parameter measurement of the target; s4, realizing three-dimensional space positioning of the target by multiple millimeter wave radar distributed networking. The method provided by the invention can be used for monitoring the dynamic target, and the method for monitoring the dynamic target by preprocessing the original data acquired by the millimeter wave radar, DFT calculation and distributed networking can be used for dynamically monitoring the physical signs of special people such as old people, infants, mental patients, large-area burns and the like.)

1. A dynamic target monitoring method based on a millimeter wave radar is characterized by comprising the following steps:

s1: transmitting a linear frequency modulation signal f (t) by using a millimeter wave radar, and mixing an echo signal R (t) with a transmitting signal T (t) to obtain a beat signal delta S (t) of a baseband;

s2: preprocessing the obtained signal to remove parasitic amplitude modulation interference and orthogonal mixing image interference;

s3: estimating the frequency of a beat signal containing target distance information by using DFT, and then converting the frequency into the estimation of distance to realize the distance parameter measurement of the target;

s4: and realizing three-dimensional space positioning of the target by using a plurality of millimeter wave radar distributed networks.

2. The method according to claim 1, wherein in S1, the millimeter wave radar is used to transmit a chirp signal f (t), and the echo signal r (t) is mixed with a transmit signal t (t) to obtain a baseband beat signal Δ S (t), which includes:

the millimeter wave radar transmits a linear frequency modulation signal f (t);

the transmitting signal T (t) and the echo signal R (t) are mixed to obtain a beat signal delta S (t) of a baseband.

3. The method for monitoring the dynamic target based on the millimeter wave radar according to claim 1, wherein the step S2 of preprocessing the obtained signal includes:

by utilizing the characteristic that the parasitic amplitude modulation interference waveform is relatively stable, the beat signal obtained during radar space illumination can be approximate to a parasitic amplitude modulation signal;

the influence of the side lobe on the main lobe of the near spectrum peak, namely orthogonal mixing image interference, is inhibited by adopting a Habras window function with large main lobe energy and small side lobe energy.

4. The method according to claim 1, wherein in step S3, the step of performing N-point DFT on the preprocessed beat signal Δ S (t) to obtain distance information comprises:

sampling N points of a sampling rate fs on the delta S (t) to obtain a sequence delta S (N);

and performing N-point DFT on the sequence deltaS (N) to obtain the frequency at the highest spectral line so as to realize the estimation of deltaS (t) frequency, and then converting the frequency into the estimation of distance so as to realize the distance parameter measurement of the target.

5. The method according to claim 1, wherein S4, the positioning of the target is implemented by the distributed networking of millimeter wave radars, which includes:

a plurality of radars are mutually independent for ranging, and a spherical equation is established to realize three-dimensional positioning;

and calculating the least square solution of the spherical equation as the position of the target.

Technical Field

The invention relates to a dynamic target monitoring method based on a millimeter wave radar, in particular to radar signal sending, collecting and preprocessing, a plurality of millimeter wave radar distributed networking three-dimensional positioning and the like.

Background

In recent years, the number of vacant home trends and the number of the elderly living alone increases, and the demand of intelligent medical equipment capable of realizing remote real-time home monitoring increases continuously. The young generation is also becoming a chronic disease army, has the characteristics of long disease duration and large service demand, and becomes a topic which is widely concerned by the society at present by how to reasonably and effectively manage middle-aged chronic diseases.

The millimeter wave radar is a radar system with high frequency band, narrow beam and high interference resistance. In the indoor location field, different from the limitations of the technologies such as electric infrared, bluetooth, WIFI and the like in the aspects of accuracy, false alarm and environmental change (such as darkness, brightness and smog), the millimeter wave radar-based indoor personnel location and fall detection method has the advantages of strong penetration capacity, non-intrusive sensing, good privacy protection, difficulty in being influenced by environmental factors (such as weather, temperature, illumination and the like), and the like, and can work in the dark or bright day. Compare with wearable medical equipment, non-contact's millimeter wave radar has effectively avoided because of contacting the discomfort that the health caused to the people, compares the motion bracelet, and the millimeter wave radar is more abundant to the data application that detects, has stronger medical value, compares wearable medical equipment, and the flexibility of millimeter wave radar is higher, experiences the sense more comfortable convenient, and it is wider to be suitable for the crowd. The millimeter wave technology is also applied to the products for realizing vital sign detection in the market, but the products are still in the development stage, the technology is not mature enough, and the scenes are not diversified enough.

The method involves monitoring a dynamic target by using a millimeter wave radar, so that the acquired data needs to be calculated and analyzed. In order to acquire the azimuth information of the complete target, a plurality of millimeter wave radar distributed networks are needed to complete the positioning of the three-dimensional space. Because the requirement on the real-time performance of three-dimensional positioning is high, a method which is high in accuracy and strong in real-time performance is sought, the acquisition, calculation and analysis of radar data can be completed quickly, and the method provides support for the application of relevant human body positioning so that an alarm can be given in time when the old people fall down or other abnormal conditions are detected quickly in the following.

Disclosure of Invention

In order to collect millimeter wave radar data more efficiently and conveniently and provide original data for positioning of a dynamic target in real time, a monitoring method for the dynamic target based on the millimeter wave radar is needed. The method can be used for rapidly completing acquisition, preprocessing and networking positioning of the beat signals, and has the advantages of high precision, real-time monitoring, interference resistance and the like. The specific technical scheme of the invention is as follows:

a dynamic target monitoring method based on a millimeter wave radar comprises the following steps:

s1: transmitting a linear frequency modulation signal f (t) by using a millimeter wave radar, and mixing an echo signal R (t) with a transmitting signal T (t) to obtain a beat signal delta S (t) of a baseband;

s2: preprocessing the obtained signal to remove parasitic amplitude modulation interference and orthogonal mixing image interference;

s3: estimating the frequency of a beat signal containing target distance information by using DFT, and then converting the frequency into the estimation of distance to realize the distance parameter measurement of the target;

s4: and realizing three-dimensional space positioning of the target by using a plurality of millimeter wave radar distributed networks.

Further, in S1, the obtaining of the baseband beat signal Δ S (t) by using the millimeter wave radar to transmit the chirp signal f (t) and mixing the echo signal r (t) with the transmit signal t (t) includes:

the millimeter wave radar transmits a linear frequency modulation signal f (t);

the transmitting signal T (t) and the echo signal R (t) are mixed to obtain a beat signal delta S (t) of a baseband.

Further, S2, the preprocessing the obtained signal includes:

by utilizing the characteristic that the parasitic amplitude modulation interference waveform is relatively stable, the beat signal obtained during radar space illumination can be approximate to a parasitic amplitude modulation signal;

the influence of the side lobe on the main lobe of the near spectrum peak, namely orthogonal mixing image interference, is inhibited by adopting a Habras window function with large main lobe energy and small side lobe energy.

Further, in S3, the performing N-point DFT on the preprocessed beat signal Δ S (t) to obtain distance information includes:

sampling N points of a sampling rate fs on the delta S (t) to obtain a sequence delta S (N);

and performing N-point DFT on the sequence deltaS (N) to obtain the frequency at the highest spectral line so as to realize the estimation of deltaS (t) frequency, and then converting the frequency into the estimation of distance so as to realize the distance parameter measurement of the target.

Further, S4, the positioning of the target by the multiple millimeter wave radar distributed networking implementations includes:

a plurality of radars are mutually independent for ranging, and a spherical equation is established to realize three-dimensional positioning;

and calculating the least square solution of the spherical equation as the position of the target.

The dynamic target monitoring method based on the millimeter wave radar can be used for monitoring the dynamic target, and the dynamic target monitoring method can be used for dynamically monitoring the physical signs of special people such as old people, infants, mental patients, large-area burns and the like by preprocessing original data acquired by the millimeter wave radar, DFT calculation and distributed networking.

Drawings

Fig. 1 is a flowchart of a method for monitoring a dynamic target based on a millimeter wave radar according to an embodiment.

Fig. 2 is a schematic diagram of three-dimensional networking of the millimeter wave radar in the embodiment.

Detailed Description

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required in the embodiments are briefly described below.

The invention will be further explained with reference to the drawings.

The dynamic target positioning method of the millimeter wave radar provided by the embodiment of the invention is used for acquiring millimeter wave radar data in real time, calculating and processing to obtain the three-dimensional positioning of the target, and can provide support for the application of nursing homes, hospitals, families and the like. The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration and explanation only, not limitation.

Fig. 1 is a flowchart of a method for monitoring a dynamic target based on a millimeter wave radar according to an embodiment of the present application. The method comprises the steps that S1 linear frequency modulation signals are transmitted by a millimeter wave radar, and baseband beat signals are obtained after echo signals and transmission signals are mixed; s2, preprocessing the obtained signal to remove parasitic amplitude modulation interference and quadrature mixing image interference; s3, carrying out frequency estimation on the beat signal containing the target distance information by using DFT, and then converting the frequency estimation into distance estimation to realize parameter measurement of the target; s4, realizing three-dimensional space positioning of the target by multiple millimeter wave radar distributed networking.

In step S1, assume that the linear modulation of the single-frequency signal is f_T(t) phase isThen the millimeter wave radar transmits signals as follows:

the echo signal obtained after the time t1 is 2R/c is:

the baseband beat signal obtained after mixing is:

ΔS(t)＝exp{j(T(t)-R(t))}

in step S2, for the spurious amplitude modulation interference S (t), the beat signal Δ S (t) is affected and interfered, that is, a modulation signal is superimposed on the beat signal in the frequency modulation period:

ΔS^*(t)＝ΔS(t)+s(t)

at the moment, by utilizing the characteristic that parasitic amplitude modulation interference is relatively stable, a beat signal delta S corresponding to radar space illumination is obtained first¹(t), this can be approximated as a parasitic amplitude-modulated signal, Δ S¹(t) ≈ s (t), so that a target true beat signal can be found, thereby suppressing the influence of spurious amplitude modulation interference.

For quadrature mixing image interference, a window function can be used to suppress the influence of side lobes on the main lobe of the near spectral peak, and here, a third-order habs window can be selected:

where N is the number of sampling points, k is 3, a₀＝0.35875，a₁＝0.48829，a₂＝0.14128，a₃0.01168. In step S3, the requested target distance R is obtained by substituting t 1-2R/c into the preprocessed Δ S (t) and applying the sampling rate f to the result_sThen, the N-point DFT is calculated to obtain the frequency f at the highest spectral line of the signal spectrum X (k)_mWhen the DFT points are increased to realize the refinement of the frequency spectrum, namely the spectral line distance of the frequency spectrum is denser, the highest spectral line is closer to the real frequency value, so that the estimation of the frequency Delta S (t) is realized, the estimation accuracy can be improved, and the target distance R is as follows:

in step S4, the multiple millimeter wave radars measure distance independently from each other, a spherical equation can be established to achieve three-dimensional positioning, and only each millimeter wave radar needs to measure distance, no angle measurement, and no phase difference calculation, so that the calculation amount is moderate, and the positioning accuracy is high.

As shown in FIG. 2, three fixed radars are arranged at right angles to each other and have coordinates of (x)_i,y_i,z_i) I is 1,2,3, the target coordinates are (x, y, z), and the distance from the radar is R_i,

Because of the error in the actual environment, the measured value and the actual value have certain error, so the method is designed

Namely solving the least square solution of the equation set, wherein the solution is the solution which is closest to the true value under the current measurement condition, namely the coordinates of the target, and the specific process of solving the nonlinear equation set by the Newton method is as follows:

let it solve asAt a point in its vicinityHandle f_i(x, y, z) is expanded to a Taylor expansion:

ignoring remainder R_iObtaining:

this is a set of linear equations, the solution of whichAs a solution, the coefficients matrix Jacobi array

Writing into vector form:substituting the linear equation set, then:

f(x⁰)+J(x⁰)(x-x⁰)＝0

solving for its least squares solution x¹

x¹＝x⁰-J^-1(x⁰)(x⁰)

Wherein J^-1It is understood as a generalized inverse of the Jacobi array, so the value at each iteration:

x^k+1＝x^k-J^-1(x^k)(x^k)

when the iteration error is gradually reduced to be smaller than the threshold value or the set maximum iteration number is reached, a least square solution can be obtained at the moment.

And because the motion displacement of the dynamic target is very small in a very small time, the dynamic target can be regarded as a static target, so that the method can realize the dynamic target monitoring with higher precision and higher real-time performance.