CN107918125B - Single-emitting multi-receiving terahertz aperture coding imaging device and method - Google Patents
Single-emitting multi-receiving terahertz aperture coding imaging device and method Download PDFInfo
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Abstract
The invention discloses a single-transmitting multi-receiving terahertz aperture coding imaging device and a method, wherein the method comprises the following steps: s100, transmitting a terahertz signal to a transmission type coding aperture by a transmitting unit of the single-transmitting multi-receiving array antenna; s200, under the control of a system control host, loading a lens phase modulation factor on the terahertz signal by using a transmission type coded aperture, and directionally projecting the loaded signal to a target space to scan a target; s300, when the echo signal is scattered on the surface of the target, the transmission type coding aperture loads an aperture coding random phase shifting factor on the echo signal; s400, sampling the echo signals loaded by the phases by a receiving unit of the single-transmitting multi-receiving array antenna, and returning the echo signals to a system control host to perform imaging processing to obtain target imaging. The imaging range is enlarged, and the imaging resolution and the imaging speed are further improved, so that the problem that the current radar foresight imaging technology cannot simultaneously give consideration to real-time performance, high resolution and imaging range is solved.
Description
Technical Field
The invention relates to the technical field of high-resolution radar staring imaging, in particular to a single-transmission multi-reception terahertz aperture coding imaging device and method.
Background
With the development of society, radar high-resolution imaging plays an increasingly important role in ensuring national strategic safety and promoting national economic development. The existing radar imaging systems mainly comprise a microwave radar imaging system and an optical radar imaging system. The optical sensor can image forward, has short wavelength, high resolution and high imaging speed, but has poor penetration capability to smoke, dust, fog, obstacles and the like depending on target radiation, and is easily influenced by environmental factors. The microwave radar sensor can actively detect and has strong penetration capability, but because of low microwave frequency, long wavelength and low angular resolution, and because of the limitation of an imaging principle, imaging accumulation time is required, and forward-looking high-frame-frequency and high-resolution imaging cannot be realized [1 ]. Although the Synthetic Aperture Radar (SAR) and the Inverse Synthetic Aperture Radar (ISAR) can obtain high resolution in the transverse direction through the synthetic aperture, the SAR and the ISAR both depend on relative motion of the radar and a target and cannot perform forward-looking imaging, and the real aperture array radar and the phased array radar have the defects of large number of array elements, complex structure and high construction and maintenance cost due to the fact that the array elements need to be used.
The microwave correlation imaging technology can realize high-resolution imaging under forward looking and staring conditions. The method comprises the steps of constructing array signals which are uncorrelated in time and orthogonal in space as transmitting signals, obtaining detection signals of an area where a target is located through calculation and deduction, and obtaining target information through correlation processing between the detection signals and target echo signals. However, this method requires a large-scale antenna array to be constructed at the transmitting end, and it is difficult to implement effective real-time beam pointing control.
The aperture coding imaging technology uses the microwave correlation imaging principle for reference, adopts programmable metamaterial to replace a large-scale imaging array antenna, can realize beam electric control modulation, can effectively improve the imaging speed and reduce the system scale and cost. Under the single-transmitting single-receiving antenna system, the requirements of target high-resolution imaging on sampling and coding times are improved, so that the imaging speed is reduced. In addition, the current aperture coding imaging system needs random coding at the transmitting end, thereby inhibiting the forming capability of transmitting beams and shortening the distance of an imageable target.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a single-transmission multi-reception terahertz aperture coding imaging device and a method, aiming at enlarging the imaging action distance and further improving the imaging resolution and the imaging speed, thereby solving the problem that the current radar foresight imaging technology is difficult to simultaneously consider real-time property, high resolution and imaging distance.
The technical scheme adopted by the invention is as follows: a single-emitting multi-receiving terahertz aperture coding imaging method comprises the following steps:
s100, transmitting a terahertz signal to a transmission type coding aperture by a transmitting unit of the single-transmitting multi-receiving array antenna;
s200, under the control of a system control host, loading a lens phase modulation factor on the terahertz signal by the transmission type coded aperture, and directionally projecting the terahertz signal loaded with the phase to a target space to scan a target;
s300, when the echo signal is scattered on the surface of the target, the transmission type coding aperture loads an aperture coding random phase shifting factor on the echo signal under the control of the system control host;
s400, sampling the echo signals loaded by the phases by a receiving unit of the single-transmitting multi-receiving array antenna, and returning the echo signals to a system control host to perform imaging processing to obtain target imaging.
The single-emitting multi-receiving terahertz aperture coding imaging method is characterized in that the terahertz signal is
Wherein, tnFor the terahertz signal emission time, A is the terahertz signal amplitude, fcIs the center frequency of the terahertz signal,is the frequency hopping frequency of the terahertz signal.
The single-shot multiple-receiver terahertz aperture coding imaging method comprises the following steps of:
when the terahertz signal reaches the transmission type coding aperture, the terahertz signal of the p-th array element in the vertical direction of the transmission type coding aperture is
Wherein, tTx,pFor the time between the transmitting unit and the p-th array element in the vertical direction of the transmissive coding apertureAnd P is 1,2, P.
The single-emitting multi-receiving terahertz aperture coding imaging method comprises the following specific steps of S200:
the system control host generates a corresponding phase distribution diagram according to a lens phase modulation factor in the following formula, inputs the corresponding phase distribution diagram to the transmission type coding aperture, and loads the lens phase modulation factor on the terahertz signal:
wherein,k-2 pi f as a phase modulation factor of the lenscC, c is the speed of light, ypIs the vertical coordinate of the center point of the p-th array element in the vertical direction of the transmission type coding aperture, y0Is the ordinate at the position of the phase center of the phase modulation factor of the lens over the transmissive coded aperture, and f is the focal length of the lens.
The single-emitting multi-receiving terahertz aperture coding imaging method includes that in the step S200, when a is greater than b, the focal length of the lens satisfies the requirement
Wherein, a is the horizontal distance between the single-transmitting multi-receiving array antenna and the transmission type coding aperture, b is the horizontal distance between the transmission type coding aperture and the imaging plane, and d is the horizontal distance between the imaging plane and the focusing plane;
when a is less than or equal to b, the focal length of the lens is
f＝a (5)
The single-shot multiple-receiver terahertz aperture coding imaging method includes:
when the phase-loaded terahertz signal reaches the imaging plane, the terahertz signal of the kth grid in the vertical direction of the imaging plane is
Wherein, tp,kAnd K is the time delay from the p-th array element in the vertical direction of the transmission type coding aperture to the K-th grid of the imaging plane, and K is 1, 2.
The single-shot multiple-receiver terahertz aperture coding imaging method comprises the following specific steps of:
when the echo signal is scattered on the surface of the target, the system control host generates a corresponding phase distribution diagram according to the aperture coding random phase-shifting factor in the following formula, inputs the corresponding phase distribution diagram to the transmission type coding aperture, and loads the aperture coding random phase-shifting factor on the echo signal; the aperture coding random phase shift factor is
Wherein, PlIs the upper limit of the random phase shift interval, PhAnd in the lower limit of the random phase shifting interval, random (-) means that uniformly distributed random phases positioned in the phase shifting interval are applied to the array elements in the vertical direction of the transmission type coded aperture.
The single-shot multiple-receiver terahertz aperture coding imaging method comprises the following steps of S400:
the phase-loaded echo signal is
wherein, betakScattering coefficient of the object for the kth grid of the imaging plane, tk,pIs the time delay from the k grid of the imaging plane to the p array element in the vertical direction of the transmission type coded aperture 30, SI(rk,tn-tk,p) I is the echo signal of the p-th array element in the vertical direction of the transmission type coded aperture 30;
when the phase-loaded echo signal is sent to the receiving unit, the phase-loaded echo signal on the q receiving unit of the single-transmitting multi-receiving array antenna is
Wherein, tp,qAnd Q is the time delay from the p-th array element to the Q-th receiving unit of the single-transmitting multi-receiving array antenna in the vertical direction of the transmission type coding aperture, and is 1, 2.
The single-shot multiple-receiver terahertz aperture coding imaging method comprises the following steps of S400:
the overall imaging equation is
Sr＝Sβ+w (10)
wherein w is a noise vector, β is a target scattering coefficient vector, Sr is a received echo signal vector, S is a reference signal vector,
wherein, SrqFor performing t on echo signals0，t1，···，tNSampling at a point in time, receiving echo signals at the qth receiving unit, SrqIs expressed as
Srq＝[Srq(t0),Srq(t1),...,Srq(tN-1)]T(12)
Wherein [ ·]TRepresenting a transpose;
Sqis a reference signal matrix, SqIs expressed as
A single-shot multi-receiving terahertz aperture coding imaging device comprises:
the system comprises a system control host, a single-transmitting multi-receiving array antenna and a transmission type coding aperture;
the single-emitting multi-receiving terahertz aperture coding imaging device adopts any one of the above-mentioned single-emitting multi-receiving terahertz aperture coding imaging methods to perform imaging.
The invention can realize high resolution, high frame frequency, real-time and miniaturization of the radar imaging device; compared with the current aperture coding imaging system, the method can effectively improve the imaging distance and the imaging speed. In addition, the forward-looking fast high-resolution imaging can be realized for the short-distance target and the medium-distance target, so that the method is more suitable for the radar imaging fields of security inspection, anti-terrorism, target detection and identification and the like.
Drawings
Fig. 1 is a schematic close-up imaging diagram of a single-emitting multi-receiving terahertz aperture coding imaging device of the invention.
Fig. 2 is a schematic diagram of middle-range imaging of the single-transmission multi-reception terahertz aperture coding imaging device of the invention.
Fig. 3 is a flowchart of a preferred embodiment of the single-transmit multi-receive terahertz aperture coding imaging method of the present invention.
Fig. 4 is a functional block diagram of a preferred embodiment of the single-transmit multi-receive terahertz aperture coding imaging method of the present invention.
FIG. 5 is a comparison graph of close-range target imaging results of the single-transmission multi-reception terahertz aperture coding imaging method and the single-transmission single-reception terahertz aperture coding imaging method.
FIG. 6 is a comparison graph of distance target imaging results in the single-transmission multi-reception terahertz aperture coding imaging method and the single-transmission single-reception terahertz aperture coding imaging method of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1, fig. 1 is a schematic close-up imaging diagram of a single-transmission multi-reception terahertz aperture coding imaging apparatus according to the present invention. As shown in fig. 1, the single-transmit multi-receive terahertz aperture coding imaging apparatus according to the embodiment of the present invention includes: the system comprises a system control host 10, a single-transmitting multi-receiving array antenna 20 and a transmission type coded aperture 30; the system control host 10 is connected to the single-transmit multi-receive array antenna 20 and the transmissive coded aperture 30, respectively. The single-transmitting multi-receiving array antenna 20 includes one transmitting unit 40 and Q receiving units 50, and the height in the vertical direction is g. The transmissive code aperture 30 includes P array elements in the vertical direction, and the height h in the vertical direction is generally set to be greater than the height g in the vertical direction of the single-transmit multi-receive array antenna 20. The horizontal distance between the single-transmitting multi-receiving array antenna 20 and the transmissive code aperture 30 is a, and the horizontal distance between the transmissive code aperture 30 and the target is b, that is, the horizontal distance between the transmissive code aperture 30 and the imaging plane is b. The maximum detectable target height of the single-transmitting multi-receiving terahertz aperture coding imaging device is l, the ratio of l to P represents the pitch of a single array element, the smaller the pitch is, the aperture coding and phase modulation can be performed on terahertz waves radiated by the transmitting antenna on a smaller unit scale so as to obtain better coding effect and beam forming capability, the specific value is determined by the processing technology of the transmission type coding antenna, and the pitch of the array element can reach hundreds of microns by taking the transmission type array antenna based on the metamaterial as an example. The value of a is determined by the size of the transmissive code aperture 30 and the beam width of the transmitting unit 40 of the single-transmitting multi-receiving array antenna 20, so that the transmitting beam can cover the code aperture completely and optimally. b represents the detection range of the device of the present invention, and the center points of the single-transmit multi-receive array antenna 20 and the coded aperture are on the same axis z-axis. The z-axis is parallel to the bisector of the angle of the transmit beam and perpendicular to the transmissive coded aperture 30. The position of the imaging plane beam scanning area is related to the size and the lens phase modulation factor loaded by the coded aperture, wherein the imaging plane can be divided into K grid cells according to the resolution, and the position of the default grid center and the scattering intensity represent the scattering information of the whole grid cell. For a close-range target, as shown in fig. 1, the imaging beams converge in a scanning area with a target plane size of s; for the medium-distance target, as shown in fig. 2, the terahertz wave passing through the coding aperture is a parallel beam, and the size of the area scanned on the target plane is the same as the size h of the coding aperture.
The terahertz wave beam can be spatially modulated by the transmitting unit through the coded aperture, on one hand, the wave beam pointing control can be carried out, on the other hand, the received wave can be randomly modulated, and the aperture coding imaging principle is that the stronger the random fluctuation of the signal time space is, the higher the imaging resolution is. While transmissive coded apertures 30 are used here, reflective coded apertures may also be used, but transmissive systems are smaller, more portable, and easier to control than reflective systems.
Referring to fig. 3-4, fig. 3 is a flowchart illustrating a single-transmit multi-receive terahertz aperture coding imaging method according to a preferred embodiment of the present invention. As shown in fig. 3, the single-transmission multi-reception terahertz aperture coding imaging method according to the embodiment of the present invention includes the following steps:
step S100, the transmitting unit 40 of the single-transmitting multi-receiving array antenna 20 transmits a terahertz signal to the transmissive coding aperture 30;
specifically, the terahertz signal is
Wherein, tnFor the terahertz signal emission time, A is the terahertz signal amplitude, fcIs the center frequency of the terahertz signal,is the frequency hopping frequency of the terahertz signal. Compared with microwave millimeter waves, the terahertz signal has short wavelength and high imaging resolution; compared with light waves, the light wave-absorbing imaging device is high in penetrability and can penetrate clothes and the like to perform human body security inspection imaging.
When the terahertz signal reaches the transmission type coding aperture 30, the terahertz signal of the p-th array element in the vertical direction of the transmission type coding aperture 30 is
Wherein, tTx,pIs the time delay between the transmitting unit 40 and the p-th array element in the vertical direction of the transmission type coding aperture 30; p is 1,2, P. In another preferred embodiment of the present invention, the time delay between the transmitting unit 40 and the p-th array element in the vertical direction of the transmissive coding aperture 30 is not included in the calculation of the terahertz signal of the p-th array element in the vertical direction of the transmissive coding aperture 30, so that the difficulty of calculation can be reduced.
Step S200, the transmissive coding aperture 30 loads a lens phase modulation factor to the terahertz signal under the control of the system control host 10, and directionally projects the phase-loaded terahertz signal to a target space to scan the target.
The transmission type coded aperture 30 only loads a lens phase modulation factor in a transmitting link, and effectively controls the pointing direction of a terahertz wave beam; for a close-range imaging target, the terahertz waves are converged in an effective imaging area; and (4) centering a distance imaging target, and irradiating the terahertz waves in parallel in a target imaging area.
Specifically, the system control host 10 generates a corresponding phase distribution map according to a lens phase modulation factor in the following formula, inputs the phase distribution map to the transmissive encoding aperture 30, loads the lens phase modulation factor on the terahertz signal, and directionally projects the phase-loaded terahertz signal to a target space to scan a target;
wherein,k-2 pi f as a phase modulation factor of the lensc/c，fcIs the center frequency of the terahertz signal, c is the speed of light, ypIs the ordinate of the central point of the P-th array element in the vertical direction of the transmission type coding aperture 30, P is 1,2, P, y0Is the ordinate at the phase center position of the lens phase modulation factor over the transmissive coded aperture 30, and f is the focal length of the lens.
Further, when a is larger than b, that is, when imaging at a close distance, the focal length of the lens satisfies
And the size of its single-scan imaging area can be given by:
wherein, a is the horizontal distance between the single-transmitting multi-receiving array antenna 20 and the transmission type coded aperture 30, b is the horizontal distance between the transmission type coded aperture 30 and the imaging plane, and d is the horizontal distance between the imaging plane and the focusing plane;
when a is less than or equal to b, i.e. at intermediate range imaging, the focal length of the lens is
f＝a。
Because the beam incident on the target area through the coded aperture is a parallel wave, the size of the imaging area of a single scanning is the same as the size of the aperture coding antenna, namely s-h.
Further, the maximum detectable target height of the imaging apparatus is l, and the maximum detectable heights of the short-range imaging and the middle-range imaging are the same and can be expressed by the following formula:
when the phase-loaded terahertz signal reaches the imaging plane, the terahertz signal of the kth grid in the vertical direction of the imaging plane is
Wherein, tp,kFor the time delay from the p-th array element in the vertical direction of the transmissive coding aperture 30 to the K-th grid of the imaging plane, K is 1,2, ·, K. In another preferred embodiment of the present invention, the time delay from the p-th array element in the vertical direction of the transmissive coding aperture 30 to the k-th grid of the imaging plane is not included in the calculation of the terahertz signal of the k-th grid in the vertical direction of the imaging plane, so that the difficulty of calculation can be reduced.
Step S300, when the echo signal is scattered by the target surface, the random aperture coding phase shift factor is loaded on the echo signal by the transmissive coded aperture 30 under the control of the system control host 10.
The random phase shifting factor of the aperture coding is loaded in a receiving link by utilizing the transmission type coding aperture, and the terahertz echo is subjected to random coding processing at a receiving end instead of a transmitting end, so that the incident wave energy is not dispersed, and the imaging distance of the aperture coding is effectively increased;
specifically, when the echo signal is scattered by the target surface, the system control host 10 generates a corresponding phase distribution map according to the aperture coding random phase shift factor in the following formula, and inputs the corresponding phase distribution map to the transmissive coding aperture 30, so as to load the aperture coding random phase shift factor on the echo signal.
Wherein, PlIs the upper limit of the random phase shift interval, PhRandom (-) indicates that the uniformly distributed random phase within the phase shift section is applied to the p-th array element in the vertical direction of the transmissive code aperture 30, which is the lower limit of the random phase shift section.
Step S400, the receiving unit 50 of the single-transmitting multi-receiving array antenna 20 samples the phase-loaded echo signal, and returns the sampled echo signal to the system control host 10 to perform imaging processing, so as to obtain target imaging.
In particular, the phase-loaded echo signal is
wherein, betakScattering coefficient of the object for the kth grid of the imaging plane, tk,pIs the time delay from the k grid of the imaging plane to the p array element in the vertical direction of the transmission type coded aperture 30, SI(rk,tn-tk,p) And | is the echo signal of the p-th array element in the vertical direction of the transmissive coding aperture 30.
When the phase-loaded echo signal is transmitted to the receiving unit 50, the phase-loaded echo signal at the q-th receiving unit 50 of the single-transmission multi-reception array antenna 20 is
Wherein, tp,qFor the time delay from the p-th array element in the vertical direction of the transmissive coding aperture 30 to the Q-th receiving unit 50 of the single-transmit multi-receive array antenna 20, Q is 1,2, ·, Q,the q-th receiving unit 50, the k-th grid unit, t are assigned to the reference signal matrixnArray element of time of day. The number of receiving units 50 may be 10-100.
By time sampling the echo signal N times, the received echo signal at the qth receiving unit 50 can be expressed as:
Srq＝[Srq(t0),Srq(t1),...,Srq(tN-1)]T
wherein [ ·]TRepresenting a transpose; the sampling mode is at t0，t1，···，tNThe time points are sampled discretely.
The corresponding reference signal matrix can be expressed as:
the reference signal row direction corresponds to N time samples, and the column direction corresponds to K grid units of the imaging area.
The single-transmitting multi-receiving array antenna 20 includes Q receiving units 50 in total, and superimposes echo signals of all the receiving units 50 and corresponding reference signal matrixes thereof to obtain new echo vectors and reference signal matrixes, and the expression thereof is as follows:
finally, the total imaging equation can be obtained
Sr＝Sβ+w
Wherein,wis a noise vector, is thermal noise inevitable in the actual imaging process, beta is a target scattering coefficient vector, Sr is a received echo signal vector, and S is a reference signal vector1β2‥βk‥βK]TThe imaging method can complete terahertz aperture coding imaging under a single-transmission multi-receiving system by solving an imaging equation.
Due to the combined use of the single-transmitting multi-receiving array antenna 20 and the transmission-type aperture coding antenna, the imaging effect is ensured, the sampling time is greatly reduced, the imaging speed is improved, and the real-time performance of target imaging is further improved. Due to the fact that the terahertz wave beam receiving end is randomly coded and the transmitting end controls the pointing mode, the imaging action distance and the signal to noise ratio are improved.
A single-transmission multi-reception terahertz aperture coding imaging device based on the single-transmission multi-reception terahertz aperture coding imaging method comprises a system control host 10, a single-transmission multi-reception array antenna 20 and a transmission type coding aperture 30.
Referring to fig. 3, the system control host controls the transmitting link and the receiving link through the control host;
the transmitting link comprises 1 transmitting unit of the single-transmitting multi-receiving array antenna and a transmission type coding aperture 30, wherein the transmitting unit transmits terahertz signals to the transmission type coding aperture, the terahertz signals are processed, and the processed signals are projected to a target space to perform target scanning;
the receiving link comprises a plurality of receiving units of the array antenna and a transmission type coding aperture, the system control host finishes phase loading of scattering signals of a scanning target through the transmission type coding aperture and sends the loaded signals to the receiving units of the array antenna;
and finally, the system control host acquires and images the received signals.
The single-emitting multi-receiving terahertz aperture coding imaging device adopts any one of the single-emitting multi-receiving terahertz aperture coding imaging methods for imaging, and is specifically as described above.
Referring to fig. 1 to fig. 6, for a single-transmission multi-reception-based terahertz aperture coding imaging device, the method of the present invention is compared with an aperture coding imaging method under the existing single-transmission single-reception system in a simulation manner, and the superiority of the device of the present invention is verified. The height l of the transmissive coding aperture 30 in the vertical direction is 0.50m, the width in the horizontal direction is also 0.5m, the vertical direction includes 25 rows of array elements, the horizontal direction includes 25 columns of array elements, and there are 625 array elements. The size of the single-transmit multi-receive array antenna 20 is the same as that of the transmissive code aperture 30, and only 5 receiving units 50 are respectively arranged in the vertical direction of the transmitting unit 40 and below, for a total of 10 receiving units 50. The horizontal spacing a between the single-transmit multi-receive array antenna 20 and the transmissive encoding aperture 30 is 0.25 m.
In the transmit chain, the system control host 10 modulates the factor according to the lens phaseAnd generating a corresponding phase distribution diagram, and inputting the corresponding phase distribution diagram to the transmissive encoding aperture 30 to complete phase loading. Center frequency f of terahertz wavec300.00GHz and 3 × 10 light speed c8m/s。xp、ypThe horizontal and vertical coordinates of the center point of the p-th array element in the vertical direction of the transmission type coding aperture 30. x is the number of0、y0Is the abscissa and ordinate at the phase center position of the lens phase modulation factor of the transmissive coded aperture 30.
For a short-distance imaging target, the distance b between the transmissive encoding aperture 30 and the imaging plane is set to 1m, and the size of the imaging area is set to 0.1m × 0.1m, so that the focal length f of the lens loaded by the encoding aperture at this time is 0.2041m, and the distance d between the imaging plane and the focusing plane is 0.1111m, which can be obtained from the relational expression.
For a medium-distance imaging target, the focal length f of the lens loaded by the coded aperture is 0.25 m.
In the receive chain, the system control host 10 randomly shifts the phase factor according to the aperture codeAnd generating a corresponding phase distribution diagram, and inputting the corresponding phase distribution diagram to the transmissive encoding aperture 30 to complete phase loading, wherein p is 1,2, … and 625.
Referring to fig. 5, for a close-range imaging target, the imaging area size is 0.05m × 0.05m (length × width, as shown in fig. 5 a), the grid cell size is 0.001m, and the number of grids is 2500. Taking the pistol point scattering model as an example, the ordinary single-shot single-receiver system requires 1250 time samples, and the imaging system of the present invention requires only 125 time samples (as shown in fig. 5 b). The following compares the imaging results of 1250 (as shown in fig. 5 c) and 125 (as shown in fig. 5 d) samples of the single-shot single-receive system with the present invention. It can be seen that the target can be reconstructed by sampling 125 times in the single-transmission multi-reception system, and can be reconstructed by sampling 1250 times in the single-transmission single-reception system. And the imaging result normalized mean square error under the conditions of 125 times of single-shot multiple-receiving sampling, 1250 times of single-shot single-receiving sampling and 125 times of single-shot single-receiving sampling is respectively as follows: 0.0328, 0.2675 and 0.8584, demonstrate the advantage of the device for close range imaging targets.
For a medium-range imaging target, the imaging area size is 0.5m × 0.5m (length × width, as shown in fig. 6 a), the grid cell size is 0.01m, and the number of grids is 2500. Taking an airplane point scattering model as an example, a common single-transmitting single-receiving system samples 1250 times in time. Imaging results of 125 samples of the imaging system of the present invention (as shown in fig. 6 b) and 1250 samples of the single-shot single-receive system (as shown in fig. 6 c) and 125 samples (as shown in fig. 6 d) are compared below. The target can be reconstructed by sampling 125 times in the single-transmission multi-receiving system, the target cannot be reconstructed by the single-transmission single-receiving system under the same sampling times, and the target can be reconstructed by single-transmission single-receiving under the condition of increasing the sampling times by 10 times. And the imaging result normalized mean square error under the conditions of 125 times of single-shot multiple-receiving sampling, 1250 times of single-shot single-receiving sampling and 125 times of single-shot single-receiving sampling is respectively as follows: 0.0198, 0.0374 and 0.8448. Also, the above results demonstrate the advantage of the device for mid-range imaging targets.
In summary, in the invention, the single-transmitting multi-receiving terahertz aperture coding imaging device and method transmit the terahertz signal to the transmissive coding aperture through the transmitting unit of the single-transmitting multi-receiving array antenna; the transmission type coding aperture loads a lens phase modulation factor on the terahertz signal under the control of the system control host, and directionally projects the terahertz signal with the phase loaded to a target space to scan a target; when the echo signal is scattered on the surface of the target, the transmission type coding aperture loads an aperture coding random phase shifting factor on the echo signal under the control of the system control host; and the receiving unit of the single-transmitting and multi-receiving array antenna samples the phase-loaded echo signal and returns the sampled echo signal to the system control host to perform imaging processing to obtain target imaging. The imaging range is enlarged, and the imaging resolution and the imaging speed are further improved, so that the problem that the current radar foresight imaging technology cannot simultaneously give consideration to real-time performance, high resolution and imaging range is solved.
It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.
Claims (10)
1. A single-emitting multi-receiving terahertz aperture coding imaging method is characterized by comprising the following steps:
s100, transmitting a terahertz signal to a transmission type coding aperture by a transmitting unit of the single-transmitting multi-receiving array antenna;
s200, under the control of a system control host, loading a lens phase modulation factor on the terahertz signal by the transmission type coded aperture, and directionally projecting the terahertz signal loaded with the phase to a target space to scan a target;
s300, when the echo signal is scattered on the surface of the target, the transmission type coding aperture loads an aperture coding random phase shifting factor on the echo signal under the control of the system control host;
s400, sampling the echo signals loaded by the phases by a receiving unit of the single-transmitting multi-receiving array antenna, and returning the echo signals to a system control host to perform imaging processing to obtain target imaging.
2. The single-shot multiple-receiver terahertz aperture coding imaging method as claimed in claim 1, wherein the terahertz signal is
Wherein, tnFor the terahertz signal emission time, A is the terahertz signal amplitude, fcIs the center frequency of the terahertz signal,is the frequency hopping frequency of the terahertz signal.
3. The single-transmission multiple-reception terahertz aperture coding imaging method according to claim 2, wherein the step S100 further comprises:
when the terahertz signal reaches the transmission type coding aperture, the terahertz signal of the p-th array element in the vertical direction of the transmission type coding aperture is
Wherein, tTx,pAnd P is the time delay between the transmitting unit and the P-th array element in the vertical direction of the transmission type coding aperture, and is 1,2, P and P are the number of the array elements.
4. The single-transmitter multiple-receiver terahertz aperture coding imaging method according to claim 3, wherein the step S200 specifically comprises:
the system control host generates a corresponding phase distribution diagram according to a lens phase modulation factor in the following formula, inputs the corresponding phase distribution diagram to the transmission type coding aperture, and loads the lens phase modulation factor on the terahertz signal:
wherein,k-2 pi f as a phase modulation factor of the lenscC, c is the speed of light, ypIs the vertical coordinate of the center point of the p-th array element in the vertical direction of the transmission type coding aperture, y0Is the ordinate at the position of the phase center of the phase modulation factor of the lens over the transmissive coded aperture, and f is the focal length of the lens.
5. The single-shot multiple-receiver terahertz aperture coding imaging method as claimed in claim 4, wherein in step S200, when a is greater than b, the focal length of the lens satisfies the requirement
Wherein, a is the horizontal distance between the single-transmitting multi-receiving array antenna and the transmission type coding aperture, b is the horizontal distance between the transmission type coding aperture and the imaging plane, and d is the horizontal distance between the imaging plane and the focusing plane;
when a is less than or equal to b, the focal length of the lens is
f＝a。
6. The single-shot multiple-receiver terahertz aperture coding imaging method according to claim 5, wherein the step S200 further comprises:
when the phase-loaded terahertz signal reaches the imaging plane, the terahertz signal of the kth grid in the vertical direction of the imaging plane is
Wherein, tp,kAnd K is the time delay from the p-th array element to the kth grid of the imaging plane in the vertical direction of the transmission type coding aperture, wherein K is 1,2, K is the number of the grids.
7. The single-transmitter multiple-receiver terahertz aperture coding imaging method according to claim 6, wherein the step S300 specifically is:
when the echo signal is scattered on the surface of the target, the system control host generates a corresponding phase distribution diagram according to the aperture coding random phase-shifting factor in the following formula, inputs the corresponding phase distribution diagram to the transmission type coding aperture, and loads the aperture coding random phase-shifting factor on the echo signal; the aperture coding random phase shift factor is
Wherein, PlIs the upper limit of the random phase shift interval, PhAnd in the lower limit of the random phase shifting interval, random (-) means that uniformly distributed random phases positioned in the phase shifting interval are applied to the array elements in the vertical direction of the transmission type coded aperture.
8. The single-shot multiple-receiver terahertz aperture coding imaging method of claim 7, wherein the step S400 further comprises:
the phase-loaded echo signal is
wherein, betakScattering coefficient of the object for the kth grid of the imaging plane, tk，pIs the time delay from the k grid of the imaging plane to the p array element in the vertical direction of the transmission type coding aperture, SI(rk，tn-tk，p) For transmitting the echo information of the p-th array element in the vertical direction of the coded apertureNumber;
when the phase-loaded echo signal is sent to the receiving unit, the phase-loaded echo signal on the q receiving unit of the single-transmitting multi-receiving array antenna is
Wherein, tp,qAnd Q is the time delay from the p-th array element to the Q-th receiving unit of the single-transmission multi-reception array antenna in the vertical direction of the transmission type coding aperture, and Q is 1,2, Q, and Q is the number of the receiving units.
9. The single-shot multiple-receiver terahertz aperture coding imaging method of claim 8, wherein the S400 step further comprises:
the overall imaging equation is
Sr＝Sβ+w
wherein w is a noise vector, β is a target scattering coefficient vector, Sr is a received echo signal vector, S is a reference signal vector,
wherein, SrqFor performing t on echo signals0，t1，···，tNSampling at a point in time, receiving echo signals at the qth receiving unit, SrqIs expressed as
Srq＝[Srq(t0),Srq(t1),...,Srq(tN-1)]T
Wherein [ ·]TRepresenting a transpose;
Sqis a reference signal matrix, SqIs expressed as
Wherein S isq(rK，tN-1) Representing reference signal momentsThe array corresponds to the q receiving unit, the Kth grid unit, tN-1Array element of time of day.
10. The utility model provides a terahertz aperture coding image device is received to single-shot multireception, its characterized in that includes:
the system comprises a system control host, a single-transmitting multi-receiving array antenna and a transmission type coding aperture;
the single-emitting multi-receiving terahertz aperture coding imaging device adopts the single-emitting multi-receiving terahertz aperture coding imaging method of any one of claims 1 to 9 for imaging.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105403889A (en) * | 2016-01-08 | 2016-03-16 | 中国人民解放军国防科学技术大学 | Terahertz frequency band aperture coding high-resolution near-zone staring imaging device |
| CN106772367A (en) * | 2016-11-30 | 2017-05-31 | 中国人民解放军国防科学技术大学 | Long distance staring imaging device and method in the coding high-resolution of Terahertz frequency range aperture |
| CN106950555A (en) * | 2017-05-03 | 2017-07-14 | 中国人民解放军国防科学技术大学 | A kind of Area Objects imaging method based on Terahertz aperture coded imaging system |
| CN107607944A (en) * | 2017-08-29 | 2018-01-19 | 中国人民解放军国防科技大学 | Forward-looking imaging device based on terahertz frequency band transmission type aperture coding |
-
2017
- 2017-11-15 CN CN201711127444.1A patent/CN107918125B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105403889A (en) * | 2016-01-08 | 2016-03-16 | 中国人民解放军国防科学技术大学 | Terahertz frequency band aperture coding high-resolution near-zone staring imaging device |
| CN106772367A (en) * | 2016-11-30 | 2017-05-31 | 中国人民解放军国防科学技术大学 | Long distance staring imaging device and method in the coding high-resolution of Terahertz frequency range aperture |
| CN106950555A (en) * | 2017-05-03 | 2017-07-14 | 中国人民解放军国防科学技术大学 | A kind of Area Objects imaging method based on Terahertz aperture coded imaging system |
| CN107607944A (en) * | 2017-08-29 | 2018-01-19 | 中国人民解放军国防科技大学 | Forward-looking imaging device based on terahertz frequency band transmission type aperture coding |
Non-Patent Citations (1)
| Title |
|---|
| 太赫兹孔径编码成像研究综述;邓彬 等;《红外与毫米波学报》;20170630;第36卷(第3期);302-310 * |
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