CN108717188B - Rapid wall body compensation method suitable for MIMO through-wall radar imaging - Google Patents

Abstract

The invention discloses a rapid wall body compensation method suitable for MIMO through-wall radar imaging, which comprises the following steps: setting a radar to establish a coordinate system and appointing a pixel point; the MIMO through-wall radar performs multi-transmission multi-reception real-aperture front-view detection to obtain echo signals; searching the upper end and the lower end corresponding to the first pixel point to calculate the abscissa, calculating the propagation delay values of all the transceiving channels corresponding to the first pixel point, and finally obtaining the propagation delay values of all the transceiving channels corresponding to all the pixel points; and combining the echo signals and the propagation delay values to form a final image according to back projection imaging. The method avoids the problem of overlarge operation amount caused by iteration and traversal in the traditional wall body compensation method, has the good characteristics of good effect of correcting the position offset of the target image and large focusing imaging area, can be used for positioning, identifying and extracting the target from the finally obtained output image, and has good application prospect in the MIMO through-the-wall radar imaging application needing real-time processing.

Description

Rapid wall body compensation method suitable for MIMO through-wall radar imaging

Technical Field

The invention relates to a radar imaging detection method, in particular to a rapid wall body compensation method suitable for MIMO through-wall radar imaging.

Background

In the application of detecting the interior of a building based on a MIMO (Multiple Input Multiple output) through-wall radar, the positioning, identifying and extracting of a target through imaging is a basic detection requirement. Because the electromagnetic parameters (mainly, dielectric constant) of the building wall larger than the free space will cause the speed of the electromagnetic wave in the wall to decrease, thereby increasing the propagation delay of the electromagnetic wave between the antenna and the target, and the change of the electromagnetic wave speed is accompanied with refraction phenomenon, which will cause the actual propagation delay of the electromagnetic wave to be difficult to estimate quickly and accurately, if the wall penetration influence (i.e. assumed as the free space) is ignored in the imaging process, the target image defocuses and position shift will be caused, which causes the target positioning, identification and extraction difficulty in practical application, therefore, an effective wall compensation method is needed to correct the influence caused by the wall penetration.

The existing wall compensation method, such as the method for solving the fourth-order polynomial equation (transcendental equation) based on the Newton-Hohner iteration method and the Newton-Raphson iteration method, the shortest path method and the like, has the problem of overlarge calculated amount, is difficult to realize real-time processing, and limits the use of the method in actual detection.

Disclosure of Invention

The invention aims to solve the problems, solve the problem of overlarge operation amount caused by iteration and traversal in the traditional wall compensation method by using a method for solving and calculating the abscissa to obtain the propagation delay, realize effective wall compensation and realize real-time processing, and is suitable for MIMO through-wall radar imaging.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows: a rapid wall body compensation method suitable for MIMO through-wall radar imaging comprises the following steps:

(1) arranging an MIMO through-wall radar with a probe facing to the other side of the wall body on one side of the wall body in a manner of clinging to the wall body, wherein the total number of the MIMO through-wall radar transmitting and receiving channels is N, one side of the wall body, which is provided with the MIMO through-wall radar, is a setting surface, and the other side of the wall body is an interface;

(2) establishing a coordinate system by taking a central point of one surface of the MIMO through-wall radar, which is close to a wall body, as an original point, selecting a rectangular imaging area in the detection range of the MIMO through-wall radar, and designating pixel points in the rectangular imaging area at equal intervals according to horizontal and vertical coordinates;

(3) the MIMO through-wall radar carries out multi-transmission multi-reception real-aperture orthographic detection, a transmitting signal is an ultra-wideband pulse signal, collected multi-channel echo data is expressed as { s (N, t), N is 1,2, …, N }, wherein t is the receiving delay of an echo signal in an nth receiving and transmitting channel;

(4) searching the upper end corresponding to the first pixel point to calculate the abscissa;

(41) numbering the receiving and transmitting channels in sequence, wherein in the first receiving and transmitting channel, the central points of the transmitting antenna and the receiving antenna are respectively connected with the pixel points P (x, y), and the connecting line and the normal line of the interface form an included angle theta_{1, H, hair}、θ_{1, H, harvesting}Calculating theta based on the principle of refraction_{1, H, hair}、θ_{1, H, harvesting}Angle of refraction of

(42) Taking the central point of the transmitting antenna as an end point as a ray, wherein the angle between the ray and the normal of the setting surface is

The abscissa of the intersection point of the ray and the boundary surface is H_{1, sending out}Taking the central point of the receiving antenna as an end point as a ray, wherein the included angle between the ray and the normal of the setting surface is

The abscissa of the intersection point of the ray and the boundary surface is H_{1, harvesting}Will (H)_{1, sending out}，H_{1, harvesting}) Marking the upper end corresponding to the transceiving channel to calculate the abscissa;

(43) sequentially calculating the upper end calculation abscissa (H) corresponding to all the transceiving channels_{n, hair}、H_{n, receiving})，n＝1，2，……N；

(5) Searching a lower end corresponding to the first pixel point to calculate a horizontal coordinate;

(51) in the first transceiving channel, the orthographic projections of the central points of the transmitting antenna and the receiving antenna on the interface are respectively connected with the pixel points P (x, y) to form an included angle theta_{1, L, hair}、θ_{1, L, harvesting}Calculating theta based on the principle of refraction_1,L,_{Hair-like device}、θ_{1, L, harvesting}Angle of refraction of

(52) Taking the central point of the transmitting antenna as an end point as a ray, wherein the angle between the ray and the normal of the setting surface is

The abscissa of the intersection point of the ray and the boundary surface is L_{1, sending out}Taking the central point of the receiving antenna as an end point as a ray, wherein the included angle between the ray and the normal of the setting surface is

The abscissa of the intersection point of the ray and the boundary surface is L_{1, harvesting}Will (L)_{1, sending out}，L_{1, harvesting}) Marking the lower end corresponding to the transceiving channel to calculate a horizontal coordinate;

(53) sequentially calculating the corresponding lower end calculation abscissa (L) of all the transceiving channels_{n, hair}、L_{n, receiving})，n＝1，2，……N；

(6) Calculating propagation delay values of all receiving and transmitting channels corresponding to the first pixel point;

(61) in the first transceiving channel, H_{1, sending out}And L_{1, sending out}Weighted summation to G_{1, sending out}，H_{1, harvesting}And L_{1, harvesting}Weighted summation to G_{1, harvesting}；

(62) According to G_{1, sending out}And G_{1, harvesting}Respectively calculating propagation delay tau of transmitting antenna and receiving antenna_{1, sending out}，τ_{1, harvesting}To obtain a propagation delay value (tau)_{1, sending out}、τ_{1, harvesting})；

(63) Repeating the steps to obtain the propagation delay values (tau) of all the receiving and transmitting channels corresponding to the pixel point_{n, hair}、τ_{n, receiving})，n＝1，2，……N；

(7) Repeating the steps (4), (5) and (6), and calculating propagation delay values of all the pixels corresponding to all the transceiving channels;

(8) and for each pixel point, forming a final image according to back projection imaging according to the multi-channel echo data { s (N, t), wherein N is 1,2, …, N } and propagation delay values of all the transmitting and receiving channels corresponding to the pixel point.

Preferably, the method comprises the following steps: in the step (41), theta is calculated according to the refraction principle_{1, L, hair}、θ_{1, L, harvesting}Angle of refraction of

The method specifically comprises the following steps: calculated according to the following formula:

wherein epsilon_wIs the relative dielectric constant of the wall.

Preferably, the method comprises the following steps: in the step (61), H_{1, sending out}And L_{1, sending out}Weighted summation to G_{1, sending out}，H_{1, harvesting}And L_{1, harvesting}Weighted summation to G_{1, harvesting}The method comprises the following steps:

G_{1, sending out}＝k×H_{1, sending out}+(1-k)×L_{1, sending out}

G_{1, harvesting}＝k×H_{1, harvesting}+(1-k)×L_{1, harvesting}

Wherein

ε_wIs the relative dielectric constant of the wall.

Preferably, the method comprises the following steps: in said step (62), according to G_{1, sending out}And G_{1, harvesting}Respectively calculating propagation delay tau of transmitting antenna and receiving antenna_{1, sending out}，τ_{1, harvesting}：

Where (x, y) is the coordinate of the pixel point, d_wIs the wall thickness, x_{1, sending out}And x_{1, harvesting}The abscissa of the center point of the transmitting antenna and the center point of the receiving antenna of the 1 st transceiving channel.

Preferably, the method comprises the following steps: the step (8) is specifically as follows:

(81) for a first pixel point, calculating a pixel value of the pixel point according to backward projection imaging according to multi-channel echo data { s (N, t), wherein N is 1,2, …, N }, and propagation delay values of all receiving and transmitting channels corresponding to the pixel point;

(82) and repeating the steps, and calculating the pixel values of all the pixel points according to the backward projection imaging to obtain the final image.

Preferably, the method comprises the following steps: in step (81), the pixel value of the pixel point located at P (x, y) is calculated as:

compared with the prior art, the invention has the advantages that: the invention aims at the detection requirement of positioning, identifying and extracting a target by MIMO radar through-wall detection imaging, and provides a rapid wall compensation method suitable for MIMO through-wall radar imaging.

Drawings

FIG. 1 is a schematic diagram of MIMO through-the-wall radar detection in the present invention;

FIG. 2 is a schematic diagram of the calculation of the abscissa of the upper end of the first pixel point;

FIG. 3 is a schematic diagram of a first pixel point with a lower-end calculated abscissa;

FIG. 4 is a flow chart of the present invention; FIG. 5 is a diagram showing a simulation setup in example 2;

FIG. 5 is a simulation scenario setup diagram in example 2;

FIG. 6 is multi-channel echo data of example 2;

FIG. 7 is the final imaging results of example 2;

fig. 8 is a direct backprojection imaging contrast.

In the figure: 1. a wall body; 2. MIMO through-the-wall radar; 3. a stationary target 1; 4. a stationary target 2; 5. a stationary target 3; 6. a stationary target to be tested;

Detailed Description

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

Example 1: referring to fig. 1 to 4, a fast wall compensation method suitable for MIMO through-wall radar imaging includes the following steps:

(1) arranging an MIMO through-wall radar 2 with a probe facing to the other side of the wall body 1 on one side of the wall body 1 in a manner of being tightly attached to the wall body 1, wherein the total number of receiving and transmitting channels of the MIMO through-wall radar 2 is N, one side of the wall body 1, which is provided with the MIMO through-wall radar 2, is an arrangement surface, and the other side is an interface;

(2) establishing a coordinate system by taking a central point of one surface of the MIMO through-wall radar 2 close to the wall body 1 as an origin, selecting a rectangular imaging area in the detection range of the MIMO through-wall radar 2, and designating pixel points at equal intervals in the rectangular imaging area according to horizontal and vertical coordinates;

(3) the MIMO through-wall radar 2 performs multi-transmission multi-reception real-aperture orthographic detection, a transmitting signal is an ultra-wideband pulse signal, collected multi-channel echo data is expressed as { s (N, t), N is 1,2, …, N }, wherein t is the receiving delay of an echo signal in the nth receiving and transmitting channel;

(4) searching the upper end corresponding to the first pixel point to calculate the abscissa;

(41) numbering the receiving and transmitting channels in sequence, wherein in the first receiving and transmitting channel, the central points of the transmitting antenna and the receiving antenna are respectively connected with the pixel points P (x, y), and the connecting line and the normal line of the interface form an included angle theta_{1, H, hair}、θ_{1, H, harvesting}Calculating theta based on the principle of refraction_{1, H, hair}、θ_{1, H, harvesting}Angle of refraction of

In the step (41), theta is calculated according to the refraction principle_{1, L, hair}、θ_{1, L, harvesting}Angle of refraction of

The method specifically comprises the following steps: calculated according to the following formula:

wherein epsilon_wIs the relative dielectric constant of the wall 1;

(42) taking the central point of the transmitting antenna as an end point as a ray, wherein the angle between the ray and the normal of the setting surface is

The abscissa of the intersection point of the ray and the boundary surface is H_{1, sending out}Taking the central point of the receiving antenna as an end point as a ray, wherein the included angle between the ray and the normal of the setting surface is

The abscissa of the intersection point of the ray and the boundary surface is H_{1, harvesting}Will (H)_{1, sending out}，H_{1, harvesting}) Marking the upper end corresponding to the transceiving channel to calculate the abscissa;

(43) sequentially calculating the upper end calculation abscissa (H) corresponding to all the transceiving channels_{n, hair}、H_{n, receiving})，n＝1，2，……N；

(5) Searching a lower end corresponding to the first pixel point to calculate a horizontal coordinate;

(51) in the first transceiving channel, the orthographic projections of the central points of the transmitting antenna and the receiving antenna on the interface are respectively connected with the pixel points P (x, y) to form an included angle theta_{1, L, hair}、θ_{1, L, harvesting}Calculating theta based on the principle of refraction_1,L,_{Hair-like device}、θ_{1, L, harvesting}Angle of refraction of

(52) Using the central point of the transmitting antenna as the end point as the ray, the ray and the normal of the setting surfaceIncluded angle of

_{Hair-like device}The abscissa of the intersection point of the ray and the boundary surface is L_{1, sending out}Taking the central point of the receiving antenna as an end point as a ray, wherein the included angle between the ray and the normal of the setting surface is

The abscissa of the intersection point of the ray and the boundary surface is L_{1, harvesting}Will (L)_{1, sending out}，L_{1, harvesting}) Marking the lower end corresponding to the transceiving channel to calculate a horizontal coordinate;

(53) sequentially calculating the corresponding lower end calculation abscissa (L) of all the transceiving channels_{n, hair}、L_{n, receiving})，n＝1，2，……N；

(6) Calculating propagation delay values of all receiving and transmitting channels corresponding to the first pixel point;

(61) in the first transceiving channel, H_{1, sending out}And L_{1, sending out}Weighted summation to G_{1, sending out}，H_{1, harvesting}And L_{1, harvesting}Weighted summation to G_{1, harvesting}In the step (61), H_{1, sending out}And L_{1, sending out}Weighted summation to G_{1, sending out}，H_{1, harvesting}And L_{1, harvesting}Weighted summation to G_{1, harvesting}The details are as follows

G_{1, sending out}＝k×H_{1, sending out}+(1-k)×L_{1, sending out}

G_{1, harvesting}＝k×H_{1, harvesting}+(1-k)×L_{1, harvesting}

Wherein

ε_wIs the relative dielectric constant of the wall 1;

(62) according to G_{1, sending out}And G_{1, harvesting}Respectively calculating propagation delay tau of transmitting antenna and receiving antenna_{1, sending out}，τ_{1, harvesting}To obtain a propagation delay value (tau)_{1, sending out}、τ_{1, harvesting}) (ii) a The method specifically comprises the following steps:

where (x, y) is the coordinate of the pixel point, d_wIs the thickness, x, of the wall body 1_{1, sending out}And x_{1, harvesting}The abscissa of the center point of the transmitting antenna and the center point of the receiving antenna of the 1 st transceiving channel.

(63) Repeating the steps to obtain the propagation delay values (tau) of all the receiving and transmitting channels corresponding to the pixel point_{n, hair}、τ_{n, receiving})，n＝1，2，……N；

(7) Repeating the steps (4), (5) and (6), and calculating propagation delay values of all the pixels corresponding to all the transceiving channels;

(8) for each pixel point, according to the multi-channel echo data { s (N, t), N ═ 1,2, …, N }, and the propagation delay values of all the transceiving channels corresponding to the pixel point, a final image is formed according to back projection imaging, specifically:

(81) for a first pixel point, calculating a pixel value of the pixel point according to backward projection imaging according to multi-channel echo data { s (N, t), wherein N is 1,2, …, N }, and propagation delay values of all receiving and transmitting channels corresponding to the pixel point; the pixel value of the pixel point located at P (x, y) is calculated as:

(82) and repeating the steps, and calculating the pixel values of all the pixel points according to the backward projection imaging to obtain the final image.

Referring to fig. 1, a wall 1, a MIMO through-wall radar 2 and a stationary target 6 to be measured are provided. For better illustration of the embodiment, fig. 1 is a schematic diagram of MIMO through-wall imaging radar detection in the present invention; for convenience of display, the total number of the MIMO through-wall radar 2 transceiving channels is N, in fig. 1, the MIMO through-wall radar 2 that receives the MIMO through-wall radar 2 is transmitted 2 by 8, and includes two transmitting antennas located at two ends and a receiving antenna located in the middle, from left to right, the 1 st transmitting antenna and the 1 st receiving antenna form the 1 st transceiving channel, the 1 st transmitting antenna and the 2 nd receiving antenna form the 2 nd transceiving channel, and so on, and 16 transceiving channels are provided in total.

Similarly, the total number of the transmitting and receiving channels of the MIMO through-wall radar 2 adopting 2 transmitting and 4 receiving is 8, and so on.

Referring to fig. 2, in step (4), calculating an abscissa for finding an upper end corresponding to the first pixel point; according to the upper end calculation abscissa corresponding to all the transceiving channels obtained in the steps (41), (42) and (43), taking the first transceiving channel as an example:

(41) numbering the transceiving channels, wherein in the first transceiving channel, the transmitting antenna is T₁The receiving antenna is R₁As shown, both are connected to a pixel point P (x, y), T₁The corresponding connecting line forms an included angle theta with the normal line of the interface_1,H,_{Hair-like device}，R₁The corresponding connecting line forms an included angle theta with the normal line of the interface_{1, H, harvesting}Then calculate theta from the refraction distance calculation_1,H,_{Hair-like device}、θ_{1, H, harvesting}Angle of refraction of

(42) By T₁The central point is used as an end point to be used as a ray, and the angle between the ray and the normal of the setting surface is

So that the ray intersects the interface with the abscissa at the intersection as H_{1, sending out}For the same reason with R₁The central point is used as an end point to be used as a ray, and the angle between the ray and the normal of the setting surface is

The abscissa of the intersection point of the ray and the boundary surface is H_{1, harvesting}Will (H)_{1, sending out}，H_{1, harvesting}) Marking the upper end corresponding to the transceiving channel to calculate the abscissa;

the steps are completed, and the horizontal coordinate is calculated at the upper end of the first transceiving channel; in the same way, the upper end calculation abscissa of all the receiving and transmitting channels corresponding to the same pixel point can be obtained;

referring to fig. 3, step (5) calculates the abscissa for finding the corresponding lower end of the first pixel point; we take the first transceiving channel as an example:

(51) numbering the transceiving channels, wherein in the first transceiving channel, the transmitting antenna is T1, the receiving antenna is R1, as shown in the figure, the orthographic projection of the interface of the transmitting antenna and the receiving antenna is respectively connected with the pixel point P (x, y), and forms an included angle theta with the normal line of the interface_{1, L, hair}、θ_{1, L, harvesting}Calculating theta based on the principle of refraction_{1, L, hair}、θ_{1, L, harvesting}Angle of refraction of

(52) Taking the central point of T1 as an end point as a ray, wherein the angle between the ray and the normal of the setting surface is

The ray necessarily forms an intersection point with the interface, and the abscissa at the intersection point is L_{1, sending out}Similarly processing R1 to obtain the abscissa L at another intersection_{1, harvesting}Will (L)_{1, sending out}，L_{1, harvesting}) Marking the lower end corresponding to the transceiving channel to calculate a horizontal coordinate;

the steps are completed, and the horizontal coordinate is calculated at the lower end of the first transceiving channel; and similarly, calculating abscissas of the lower ends of all the receiving and transmitting channels corresponding to the same pixel point can be obtained.

In the invention: firstly, setting a radar, selecting a detection area, decomposing the detection area into a pixel matrix, and then detecting to obtain an echo signal; then, searching an upper end calculation abscissa and a lower end calculation abscissa corresponding to each pixel point; for better describing the scheme of the present invention, we assume that the number of transceiving channels is 16:

in the step (4), according to the steps (41) and (42), the calculation abscissa (H) of the first pixel point corresponding to the upper end of the first transceiving channel is obtained_{1, sending out}，H_{1, harvesting}) I.e. 1 set of 2 abscissa values, each of which is H_{1, sending out}，H_{1, harvesting}Then, the step (43) obtains the values corresponding to 16 groups of channels, and the total number is 16 groups, each group contains 2 values which respectively correspond to the transmitting antenna and the receiving antennaA total of 32 values for the receive antenna;

in the step (5), the calculation abscissa of the lower ends of the 16 channels corresponding to the first pixel point is obtained in the same way, 16 groups are counted, each group comprises 2 values, the 2 values correspond to the transmitting antenna and the receiving antenna respectively, and the 32 values are counted;

and (4) according to the same channel classification, weighting and summing the values of the corresponding transmitting antennas in the same channel in the steps (4) and (5), weighting and summing the values of the corresponding receiving antennas, and calculating the propagation delay by using the weighted and summed values:

for example, in the first channel, H_{1, sending out}And L_{1, sending out}Weighted summation to G_{1, sending out}，H_{1, harvesting}And L_{1, harvesting}Weighted summation to G_{1, harvesting}According to (G)_{1, sending out}、G_{1, harvesting}) Calculating to obtain a propagation delay value (tau)_{1, sending out}、τ_{1, harvesting}) (ii) a Similarly, propagation delay values of 16 channels are obtained, and 16 groups of propagation delay values are obtained, and 32 values are obtained;

in summary, a pixel point corresponds to 16 sets of propagation delay values in total;

and repeating the steps to obtain 16 groups of propagation delay values of all the pixel points.

And (5) sequentially calculating each pixel point by using a step (8), and introducing the multi-channel echo data { s (N, t), wherein N is 1,2, …, N } and 16 sets of propagation delay values of respective pairs into a back projection imaging algorithm to form a final image which can be used for positioning, identifying and extracting the target.

Example 2: referring to fig. 5 to 7, example 2 was subjected to a simulation experiment using MATLAB in order to better illustrate the present invention.

(1) Setting a simulation scene shown in fig. 5 in MATLAB, wherein the thickness of a uniform and stable building wall 1 is 35cm, the relative dielectric constant is 9, arranging an MIMO through-wall radar 2 with a probe facing the other side of the wall 1 on one side of the wall 1 in close contact with the wall 1, wherein an MIMO array in the MIMO through-wall radar 2 is composed of two transmitting antennas and eight receiving antennas, the distance between the adjacent transmitting and receiving antennas is 7.5cm, and the distance between the adjacent receiving antennas is 15 cm.

(2) The centers of the receiving and transmitting antennas are all the centers of MIMO arrays, the centers of the MIMO arrays are located at (0m,0m), three small balls are placed in a radar detection area to serve as static targets, and the positions of the static targets are (-2.7m, 1.9m), (-0.5m,7.3m) and (1.9m,4.1m), namely a static target 13, a static target 24 and a static target 35. A coordinate system is established by taking a central point of one surface of the MIMO through-wall radar 2, which is tightly attached to the wall body 1, as an original point, a rectangular imaging region (X, Y) is selected in the detection range of the MIMO through-wall radar 2, wherein X belongs to [ -4m,4m ], Y belongs to [0.35m,8m ], pixel points are designated in the rectangular imaging region at equal intervals of 0.5cm according to horizontal and vertical coordinates, and the total of 1601 × 1531 is 2451131 pixel points.

(3) The MATLAB simulation is utilized to carry out the orthographic detection, the transmitting signal is a sine signal with Gaussian pulse envelope, the center frequency is 1.5GHz, the bandwidth is 1GHz, the two transmitting antennas carry out signal transmission in sequence, for each transmission, the eight receiving antennas receive signals simultaneously, and sixteen receiving and transmitting channels are counted to obtain the multi-channel echo data shown in the figure 5.

(4) Searching the upper end corresponding to the first pixel point by adopting the method of the step (4) in the embodiment 1 to calculate the abscissa;

(5) searching the corresponding lower end of the first pixel point to calculate the abscissa by adopting the method of the step (5) in the embodiment 1;

(6) calculating propagation delay values of all the transceiving channels corresponding to the first pixel point by adopting the method of the step (6) in the embodiment 1;

(7) repeating the steps (4), (5) and (6), and calculating propagation delay values of all the pixels corresponding to all the transceiving channels;

(8) for a first pixel point, calculating a pixel value of the pixel point according to backward projection imaging according to multi-channel echo data { s (N, t), wherein N is 1,2, …, N }, and propagation delay values of all receiving and transmitting channels corresponding to the pixel point; the pixel value of the pixel point located at P (x, y) is calculated as:

and repeating the steps, and calculating the pixel values of all the pixel points according to the backward projection imaging to obtain the final image.

To illustrate the advantages of the method provided by the present invention, fig. 8 is a diagram of an image obtained by direct back projection imaging, ignoring the effect of the wall 1. It can be seen from the final image I (x, y) of fig. 7 that the method provided by the present invention has good focusing effect on the target image. As can be seen from the comparison of the two figures, the invention has good effect of correcting the position deviation of the target image and can realize effective wall body 1 compensation.

Claims (6)

1. A rapid wall body compensation method suitable for MIMO through-wall radar imaging is characterized in that: the method comprises the following steps:

(1) arranging an MIMO through-wall radar with a probe facing to the other side of the wall body on one side of the wall body in a manner of clinging to the wall body, wherein the total number of the MIMO through-wall radar transmitting and receiving channels is N, one side of the wall body, which is provided with the MIMO through-wall radar, is a setting surface, and the other side of the wall body is an interface;

(2) establishing a coordinate system by taking a central point of one surface of the MIMO through-wall radar, which is close to a wall body, as an original point, selecting a rectangular imaging area in the detection range of the MIMO through-wall radar, and designating pixel points in the rectangular imaging area at equal intervals according to horizontal and vertical coordinates;

(3) the MIMO through-wall radar carries out multi-transmission multi-reception real-aperture orthographic detection, a transmitting signal is an ultra-wideband pulse signal, collected multi-channel echo data is expressed as { s (N, t), N is 1,2, …, N }, wherein t is the receiving delay of an echo signal in an nth receiving and transmitting channel;

(4) searching the upper end corresponding to the first pixel point to calculate the abscissa;

(41) numbering the receiving and transmitting channels in sequence, wherein in the first receiving and transmitting channel, the central points of the transmitting antenna and the receiving antenna are respectively connected with the pixel points P (x, y), and the connecting line and the normal line of the interface form an included angle theta_{1, H, hair}、θ_{1, H, harvesting}Calculating theta based on the principle of refraction_{1, H, hair}、θ_{1, H, harvesting}Angle of refraction of

(42) Taking the central point of the transmitting antenna as an end point as a ray, wherein the angle between the ray and the normal of the setting surface is

The abscissa of the intersection point of the ray and the boundary surface is H_{1, sending out}Taking the central point of the receiving antenna as an end point as a ray, wherein the included angle between the ray and the normal of the setting surface is

The abscissa of the intersection point of the ray and the boundary surface is H_{1, harvesting}Will (H)_{1, sending out}，H_{1, harvesting}) Marking the upper end corresponding to the transceiving channel to calculate the abscissa;

(43) sequentially calculating the upper end calculation abscissa (H) corresponding to all the transceiving channels_{n, hair}、H_{n, receiving})，n＝1，2，……N；

(5) Searching a lower end corresponding to the first pixel point to calculate a horizontal coordinate;

(51) in the first transceiving channel, the orthographic projections of the central points of the transmitting antenna and the receiving antenna on the interface are respectively connected with the pixel points P (x, y) to form an included angle theta_{1, L, hair}、θ_{1, L, harvesting}Calculating theta based on the principle of refraction_{1, L, hair}、θ_{1, L, harvesting}Angle of refraction of

(52) Taking the central point of the transmitting antenna as an end point as a ray, wherein the angle between the ray and the normal of the setting surface is

The abscissa of the intersection point of the ray and the boundary surface is L_{1, sending out}Taking the central point of the receiving antenna as an end point as a ray, wherein the included angle between the ray and the normal of the setting surface is

The abscissa of the intersection point of the ray and the boundary surface is L_{1, harvesting}Will (L)_{1, sending out}，L_{1, harvesting}) Marking the lower end corresponding to the transceiving channel to calculate a horizontal coordinate;

(53) sequentially calculating the corresponding lower end calculation abscissa (L) of all the transceiving channels_{n, hair}、L_{n, receiving})，n＝1，2，……N；

(6) Calculating propagation delay values of all receiving and transmitting channels corresponding to the first pixel point;

(61) in the first transceiving channel, H_{1, sending out}And L_{1, sending out}Weighted summation to G_{1, sending out}，H_{1, harvesting}And L_{1, harvesting}Weighted summation to G_{1, harvesting}；

(62) According to G_{1, sending out}And G_{1, harvesting}Respectively calculating propagation delay tau of transmitting antenna and receiving antenna_{1, sending out}，τ_{1, harvesting}To obtain a propagation delay value (tau)_{1, sending out}、τ_{1, harvesting})；

(63) Repeating the steps to obtain the propagation delay values (tau) of all the receiving and transmitting channels corresponding to the pixel point_{n, hair}、τ_{n, receiving})，n＝1，2，……N；

(7) Repeating the steps (4), (5) and (6), and calculating propagation delay values of all the pixels corresponding to all the transceiving channels;

(8) and for each pixel point, forming a final image according to back projection imaging according to the multi-channel echo data { s (N, t), wherein N is 1,2, …, N } and propagation delay values of all the transmitting and receiving channels corresponding to the pixel point.

2. The method of claim 1, wherein the method comprises: in the step (41), theta is calculated according to the refraction principle_{1, L, hair}、θ_{1, L, harvesting}Angle of refraction of

The method specifically comprises the following steps: calculated according to the following formula:

wherein epsilon_wIs the relative dielectric constant of the wall.

3. The method of claim 1, wherein the method comprises: in the step (61), H_{1, sending out}And L_{1, sending out}Weighted summation to G_{1, sending out}，H_{1, harvesting}And L_{1, harvesting}Weighted summation to G_{1, harvesting}The method comprises the following steps:

G_{1, sending out}＝k×H_{1, sending out}+(1-k)×L_{1, sending out}

G_{1, harvesting}＝k×H_{1, harvesting}+(1-k)×L_{1, harvesting}

Wherein

ε_wIs the relative dielectric constant of the wall.

4. The method of claim 1, wherein the method comprises: in said step (62), according to G_{1, sending out}And G_{1, harvesting}Respectively calculating propagation delay tau of transmitting antenna and receiving antenna_{1, sending out}，τ_{1, harvesting}：

Where (x, y) is the coordinate of the pixel point, d_wIs the wall thickness, x_{1, sending out}And x_{1, harvesting}Is the abscissa, epsilon, of the center point of the transmitting antenna and the center point of the receiving antenna of the 1 st transceiving channel_wIs the relative dielectric constant of the wall.

5. The method of claim 1, wherein the method comprises: the step (8) is specifically as follows:

(81) for a first pixel point, calculating a pixel value of the pixel point according to backward projection imaging according to multi-channel echo data { s (N, t), wherein N is 1,2, …, N }, and propagation delay values of all receiving and transmitting channels corresponding to the pixel point;

(82) and repeating the steps, and calculating the pixel values of all the pixel points according to the backward projection imaging to obtain the final image.

6. The method of claim 5, wherein the method comprises: in step (81), the pixel value of the pixel point located at P (x, y) is calculated as:

Images