阅读说明：本技术 一种毫米波稀疏阵列远程监视成像方法及系统 (Millimeter wave sparse array remote monitoring imaging method and system ) 是由 孟祥新 郭柳柳 余开 张军 于 2019-09-30 设计创作，主要内容包括：本发明公开了一种毫米波稀疏阵列远程监视成像方法及系统,属于毫米波三维全息成像技术领域,包括以下步骤：S1：获得回波信号；S2：插值操作；S3：快速傅里叶变换；S4：选择距离平面；S5：频域匹配滤波；S6：快速傅里叶逆变换；S7：时域匹配滤波；S8：相干累加；S9：得到三维复数图像。本发明采用毫米波稀疏阵列全电子扫描成像体制,相比于传统的光机扫描远场成像系统,存在电磁波闪烁效应小、图像信噪比高和成像视场范围大的特点；同时所采用的信号处理成像方法较传统的时域类成像方法消耗的硬件资源少、存储空间少的优点,算法流程简单易懂,算法主体仅包含快速傅里叶变换、匹配滤波、相干累加的主体流程,计算效率高于传统的时域类算法。(The invention discloses a millimeter wave sparse array remote monitoring imaging method and a millimeter wave sparse array remote monitoring imaging system, which belong to the technical field of millimeter wave three-dimensional holographic imaging and comprise the following steps: s1: obtaining an echo signal; s2: performing interpolation operation; s3: fast Fourier transform; s4: selecting a distance plane; s5: performing frequency domain matched filtering; s6: performing fast Fourier inverse transformation; s7: time domain matched filtering; s8: coherent accumulation; s9: obtaining a three-dimensional complex image. The invention adopts a millimeter wave sparse array full-electronic scanning imaging system, and has the characteristics of small electromagnetic wave flicker effect, high image signal-to-noise ratio and large imaging field range compared with the traditional optical machine scanning far-field imaging system; meanwhile, compared with the traditional time domain type imaging method, the adopted signal processing imaging method has the advantages of less hardware resources and less storage space, the algorithm flow is simple and easy to understand, the algorithm main body only comprises the main body flows of fast Fourier transform, matched filtering and coherent accumulation, and the calculation efficiency is higher than that of the traditional time domain type algorithm.)

1. A millimeter wave sparse array remote monitoring imaging method is characterized by comprising the following steps:

s1: obtaining echo signals

Establishing a millimeter wave two-dimensional sparse array with a transmitting array element spacing of delta x_TThe spacing of receiving array elements is Deltay_RThe corresponding antenna units are activated by the transmitting array elements and the receiving array elements through the antenna switches, and the obtained echo signal is S (x) in the whole scanning process_T,y_T,x_R,y_RK) in which x_TFor the transmit array x dimension, y_TFor the y dimension of the transmit array, x_RTo receive the x-dimension, y, of the array_RFor the receive array y dimension, k is the frequency scan dimension;

s2: interpolation operation

For the obtained echo signal S (x)_T,y_T,x_R,y_RX of k)_TDimension and y_RCarrying out interpolation operation on the dimensionality to obtain an interpolated signal S_Interp(x_T,y_T,x_R,y_R,k)；

S3: fast Fourier transform

For signal S_Interp(x_T,y_T,x_R,y_RX of k)_TDimension and y_RPerforming fast Fourier transform on the dimension to obtain x of the signal_TDimension and y_RDimension-converting to frequency domain space to obtain signal of

S4: selecting a distance plane

Dividing position coordinates in a distance dimension, and setting an imaging position of the distance dimension as z_qWherein z is_q∈[z_min,z_max]Q-1, a single distance position index z is selected_q(ii) a Simultaneously indexing transmit array y_TDimension, receive array x_RDimension and frequency sweep dimension k, index values y_{T_m}、x_{R_n}And k_pWherein M is 0,1,2.. M-1, N is 0,1,2.. N-1, p is 0,1,2.. N_f-1, the resulting signal being

S5: frequency domain matched filtering

Calculating x_TDimension and y_RFrequency domain matched filter of dimension

S6: inverse fast Fourier transform

For the signal

S7: time domain matched filtering

Calculating y_TDimension and x_RTime domain matched filter H of dimension₂(y_{T_m},x_{R_n},x_T,y_R) And with the signalMultiplying by corresponding dimensionality to realize time domain matched filtering processing to obtain signals

S8: coherent accumulation

Changing the index values of m, n and p until all y is traversed_TDimension, x_RDimension and k dimension to obtain a signal

S9: obtaining three-dimensional complex images

Changing z_qTo obtain two-dimensional complex images at different positions, and repeating the steps S4-S8 until all distance positions z are traversed_qTo obtain the final three-dimensional complexAnd (3) counting the images sigma (x, y, z), transmitting the three-dimensional complex images sigma (x, y, z) to a high-performance server for target detection, target identification and image processing, and then sending to a display terminal for image display.

2. The millimeter wave sparse array remote monitoring imaging method of claim 1, wherein: in the step S1, the signal transmitted by the millimeter wave sparse array is a frequency modulated continuous wave signal or a stepped continuous wave signal, the frequency range of the signal is 12 to 18GHz, and the transmission array element interval Δ x_T0.015m, receiving array element spacing Δ y_R＝0.015m。

3. The millimeter wave sparse array remote monitoring imaging method of claim 1, wherein: in step S2, the echo signal S (x)_T,y_T,x_R,y_RX of k)_TDimension and y_RAfter dimension interpolation operation, echo signal x_TDimension and y_RThe spatial sampling interval of the dimensions becomes respectively Δ x_T[ delta ] 2 and [ delta ] y_R/2。

4. The millimeter wave sparse array remote monitoring imaging method of claim 1, wherein: in the step S2, the interpolation operation is performed by a method selected from any one of linear interpolation, spline interpolation, cubic interpolation, and SINC interpolation.

5. The millimeter wave sparse array remote monitoring imaging method of claim 1, wherein: in the step S4, the distance dimension dividing focal plane may be set to z_q∈[5m,8m]，Δz＝z_q-z_q-1The location interval of the focal planes.

6. The millimeter wave sparse array remote monitoring imaging method of claim 5, wherein: the formula for setting Δ z is

7. The millimeter wave sparse array remote monitoring imaging method of claim 1, wherein: in the step S5, the frequency domain matched filter

8. The millimeter wave sparse array remote monitoring imaging method of claim 1, wherein: in the step S7, a time-domain matched filterWherein

9. A millimeter wave sparse array remote monitoring imaging system is characterized in that human body security check real-time imaging work is carried out by the remote monitoring imaging method according to any one of claims 1-8, and the millimeter wave sparse array remote monitoring imaging system comprises the following steps:

the echo signal acquisition module is used for acquiring echo signals through the millimeter wave two-dimensional sparse array;

interpolation operation module for x of echo signal of pair_TDimension and y_RCarrying out interpolation operation on the dimensionality to obtain an interpolated signal;

fast Fourier transform module for x of interpolated signal_TDimension and y_RPerforming fast Fourier transform on the dimension to obtain x of the signal_TDimension and y_RDimension transformation to a frequency domain space;

a distance plane selection module for dividing position coordinates in the distance dimension and setting the imaging position of the distance dimension as z_qSimultaneously indexing the transmit array y_TDimension, receive array x_RDimension and frequency scanning dimension k to obtain signals

A frequency domain matched filtering module for calculating x_TDimension and y_RFrequency domain matched filter of dimension

An inverse fast Fourier transform module for aligning the signals

A time domain matched filter module for calculating y_TDimension and x_RTime domain matched filter H of dimension₂(y_{T_m},x_{R_n},x_T,y_R) And with the signal

A coherent accumulation module for changing the index values of m, n and p until all y is traversed_TDimension, x_RDimension and k dimension to obtain a signal

Three-dimensional complex image module for changing z_qTo obtain two-dimensional complex images at different positions until all distance positions z are traversed_qObtaining a final three-dimensional complex image sigma (x, y, z);

the central processing module is used for sending instructions to other modules to complete related steps;

the echo signal acquisition module, the interpolation operation module, the fast Fourier transform module, the distance plane selection module, the frequency domain matched filtering module, the fast Fourier inverse transform module, the time domain matched filtering module, the coherent accumulation module and the three-dimensional complex image module are all electrically connected with the central processing module.

Technical Field

The invention relates to the technical field of millimeter wave three-dimensional holographic imaging, in particular to a millimeter wave sparse array remote monitoring imaging method and system.

Background

In recent years, millimeter wave three-dimensional holographic imaging technology is more and more widely applied to the field of personal safety inspection, the workload of safety inspection personnel is greatly reduced, and the millimeter wave three-dimensional holographic imaging technology can be applied to customs, airports, courts and large-scale safety protection activity sites, and is a safe, civilized and efficient new safety inspection mode. However, the existing millimeter wave technology-based human body security check instrument needs to be stood in the security check instrument in a fixed posture by a security check person and needs to stay for a short time for scanning and imaging, and meanwhile, the millimeter wave human body security check instrument works under a near-field condition, the imaging distance of the millimeter wave human body security check instrument is generally very short, so that the existing millimeter wave human body security check instrument cannot really meet new requirements of efficient, quick and non-perception human body security check.

The imaging speed of the passive terahertz human body security check instrument which is proposed and reported by the current domestic and foreign research institutions can reach real time, and the experience feeling of high efficiency, high speed and no sense is achieved, but the image formed by the passive human body security check instrument is a two-dimensional intensity image, the contained information amount cannot be compared with the three-dimensional image of the active millimeter wave human body security check instrument, and most passive terahertz human body security check instruments passively receive terahertz waves radiated by human bodies through power detectors, background stray signals in the scene range of the working environment are also received indiscriminately, so that the requirements of the passive terahertz human body security check instrument on the natural conditions of the working environment such as temperature, humidity and illumination are harsh, the open security check environment cannot be achieved, and even if the passive terahertz human body security check instrument is used in the open security check environment, the imaging effect is not ideal.

For the above analysis, in the field of human body security inspection imaging, an active real-time imaging system is urgently needed to be proposed and implemented to meet the real efficient, fast and imperceptible security inspection requirement. The traditional sparse array imaging method is generally realized based on a time domain correlation algorithm and a back projection algorithm, the algorithm is derived under a time domain condition, the calculation process is complex, the calculation efficiency is low, and the requirements on hardware resources and storage resources for real-time signal processing are high, so that the millimeter wave sparse array remote monitoring imaging method is provided.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: how to effectively improve the calculation efficiency of the sparse array imaging method and make the calculation process simpler, thereby reducing the requirements on hardware resources and storage resources of real-time signal processing, and providing a millimeter wave sparse array remote monitoring imaging method. The imaging method can meet the requirement of real-time imaging by adopting an imaging mode of a millimeter wave sparse array, is based on a fast Fourier transform technology, has simpler calculation process and higher calculation efficiency compared with the traditional time domain algorithm, and is particularly suitable for the field of real-time imaging of human body security inspection because the millimeter wave sparse array adopts a full electronic switch array and has no any mechanical scanning structure.

The invention solves the technical problems through the following technical scheme, and the invention comprises the following steps:

s1: obtaining echo signals

Establishing a millimeter wave two-dimensional sparse array with a transmitting array element spacing of delta x_TThe spacing of receiving array elements is Deltay_RThe corresponding antenna units are activated by the transmitting array elements and the receiving array elements through the antenna switches, and the obtained echo signal is S (x) in the whole scanning process_T,y_T,x_R,y_RK) in which x_TFor the transmit array x dimension, y_TFor the y dimension of the transmit array, x_RTo receive the x-dimension, y, of the array_RFor the receive array y dimension, k is the frequency scan dimension;

s2: interpolation operation

For the obtained echo signal S (x)_T,y_T,x_R,y_RX of k)_TDimension and y_RCarrying out interpolation operation on the dimensionality to obtain an interpolated signal S_Interp(x_T,y_T,x_R,y_R,k)；

S3: fast Fourier transform

For signal S_Interp(x_T,y_T,x_R,y_R,k) X of_TDimension and y_RPerforming fast Fourier transform on the dimension to obtain x of the signal_TDimension and y_RDimension-converting to frequency domain space to obtain signal of

S4: selecting a distance plane

Dividing position coordinates in a distance dimension, and setting an imaging position of the distance dimension as z_qWherein z is_q∈[z_min,z_max]Q-1, a single distance position index z is selected_q(ii) a Simultaneously indexing transmit array y_TDimension, receive array x_RDimension and frequency sweep dimension k, index values y_{T_m}、x_{R_n}And k_pWherein M is 0,1,2.. M-1, N is 0,1,2.. N-1, p is 0,1,2.. N_f-1, the resulting signal being

S5: frequency domain matched filtering

Calculating x_TDimension and y_RFrequency domain matched filter of dimension

And signal

Multiplying corresponding dimensionality to perform frequency domain matching filtering processing to obtain a signal

S6: inverse fast Fourier transform

For the signal

Is/are as followsDimension and

performing fast Fourier transform on the dimension to transform the dimension into a time domain space to obtain a signal

S7: time domain matched filtering

Calculating y_TDimension and x_RTime domain matched filter H of dimension₂(y_{T_m},x_{R_n},x_T,y_R) And with the signal

Multiplying by corresponding dimensionality to realize time domain matched filtering processing to obtain signals

S8: coherent accumulation

Changing the index values of m, n and p until all y is traversed_TDimension, x_RDimension and k dimension to obtain a signal

For the signal

Y of (A) to (B)_TDimension, x_RCoherent accumulation calculation is carried out on the dimensionality and the k dimensionality to obtain a distance position z_qTwo-dimensional complex image of (a)

S9: obtaining three-dimensional complex images

Changing z_qTo obtain two-dimensional complex images at different positions, and repeating the steps S4-S8 until all distance positions z are traversed_qObtaining a final three-dimensional complex image sigma (x, y, z), transmitting the three-dimensional complex image sigma (x, y, z) to a high-performance server for target detection, target identification and image processingAnd then sent to the display end for image display.

Further, in step S1, the signal transmitted by the millimeter wave sparse array is a frequency modulated continuous wave signal or a stepped continuous wave signal, the frequency range of the signal is 12 to 18GHz, and the transmission array element interval Δ x_T0.015m, receiving array element spacing Δ y_R＝0.015m。

Further, in the step S2, the echo signal S (x)_T,y_T,x_R,y_RX of k)_TDimension and y_RAfter dimension interpolation operation, echo signal x_TDimension and y_RThe spatial sampling interval of the dimensions becomes respectively Δ x_T[ delta ] 2 and [ delta ] y_R/2。

Further, in the step S4, the distance dimension dividing focal plane may be set to z_q∈[5m,8m]，Δz＝z_q-z_q-1The location interval of the focal planes.

Further, the formula for setting Δ z is

Where c is the speed of light in free space and B ═ f_max-f_minIs the bandwidth of the millimeter wave radio frequency signal, where f_minRepresenting the minimum value of the frequency of the radio frequency signal, at 12GHz, f_maxRepresenting the maximum frequency of the radio frequency signal, at 18 GHz.

Further, in the step S5, the frequency domain matched filter

Where k 2 pi f/c is the spatial frequency wavenumber,kx_Txfor emitting spatial wave number of x dimension of array, the value range is kx_Tx∈[-π/(0.5×Δx_T),π/(0.5×Δx_T)]，ky_RxFor receiving the space wave number of the y dimension of the array, the value range is ky_Rx∈[-π/(0.5×Δy_R),π/(0.5×Δy_R)]。

Further, in the step S7, a time-domain matched filterWherein

z₀The distance position where the millimeter wave sparse array is located is usually set to 0.

Further, in the step S2, the interpolation operation is performed by a method selected from any one of linear interpolation, spline interpolation, cubic interpolation, and SINC interpolation. Compared with the traditional time domain imaging method, the imaging method has the advantages of less hardware resources and less storage space, the algorithm flow is simple and easy to understand, the algorithm main body only comprises the main body flows of fast Fourier transform, matched filtering and coherent accumulation, the calculation efficiency is higher than that of the traditional time domain algorithm, and the imaging method is worthy of being popularized and used.

The invention also provides a millimeter wave sparse array remote monitoring imaging system, which comprises:

the echo signal acquisition module is used for acquiring echo signals through the millimeter wave two-dimensional sparse array;

interpolation operation module for x of echo signal of pair_TDimension and y_RCarrying out interpolation operation on the dimensionality to obtain an interpolated signal;

fast Fourier transform module for x of interpolated signal_TDimension and y_RPerforming fast Fourier transform on the dimension to obtain x of the signal_TDimension and y_RDimension transformation to a frequency domain space;

a distance plane selection module for dividing position coordinates in the distance dimension and setting the imaging position of the distance dimension as z_qSimultaneously indexing the transmit array y_TDimension, receive array x_RDimension and frequency scanning dimension k to obtain signals

A frequency domain matched filtering module for calculating x_TDimension andy_Rfrequency domain matched filter of dimensionAnd signal

Multiplying corresponding dimensionality to carry out frequency domain matching filtering processing to obtain signals

An inverse fast Fourier transform module for aligning the signals

Is/are as followsDimension and

performing fast Fourier inverse transformation on the dimension, and transforming the dimension to a time domain space to obtain a signal

A time domain matched filter module for calculating y_TDimension and x_RTime domain matched filter H of dimension₂(y_{T_m},x_{R_n},x_T,y_R) And with the signal

Multiplying by corresponding dimensionality to realize time domain matched filtering processing to obtain signals

A coherent accumulation module for changing the index values of m, n and p until all y is traversed_TDimension, x_RDimension and k dimension to obtain a signal

For the signal

Y of (A) to (B)_TDimension, x_RCoherent accumulation calculation is carried out on the dimensionality and the k dimensionality to obtain a distance position z_qTwo-dimensional complex image of (a)

Three-dimensional complex image module for changing z_qTo obtain two-dimensional complex images at different positions until all distance positions z are traversed_qObtaining a final three-dimensional complex image sigma (x, y, z);

the central processing module is used for sending instructions to other modules to complete related steps;

the echo signal acquisition module, the interpolation operation module, the fast Fourier transform module, the distance plane selection module, the frequency domain matched filtering module, the fast Fourier inverse transform module, the time domain matched filtering module, the coherent accumulation module and the three-dimensional complex image module are all electrically connected with the central processing module. The system has the imaging characteristics of far field imaging, adopts a millimeter wave sparse array full electronic scanning imaging system, and has the characteristics of small electromagnetic wave flicker effect, high image signal-to-noise ratio and large imaging field range compared with the traditional optical machine scanning far field imaging system.

Compared with the prior art, the invention has the following advantages: the millimeter wave sparse array remote monitoring imaging method and system are suitable for remote human body security inspection imaging work, the imaging range is set to be more than or equal to five meters, the imaging characteristic is far field imaging, and a millimeter wave sparse array full electronic scanning imaging system is adopted, so that compared with a traditional optical machine scanning far field imaging system, the millimeter wave sparse array remote monitoring imaging method and system have the characteristics of small electromagnetic wave flicker effect, high image signal-to-noise ratio and large imaging field range; meanwhile, compared with the traditional time domain type imaging method, the adopted signal processing imaging method has the advantages of less hardware resources and less storage space, the algorithm flow is simple and easy to understand, the algorithm main body only comprises the main body flows of fast Fourier transform, matched filtering and coherent accumulation, the calculation efficiency is higher than that of the traditional time domain type algorithm, and the method is worthy of popularization and application.

Drawings

Fig. 1 is a schematic diagram of the distribution of sparse array elements of a millimeter wave sparse array remote monitoring imaging system in the second embodiment of the present invention;

FIG. 2 is a flowchart illustrating an embodiment of an imaging method according to a second embodiment of the present invention;

fig. 3 is an imaging result diagram of the millimeter wave sparse array remote monitoring imaging method in the second embodiment of the present invention.

Detailed Description

The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.