CN113126094A - Synthetic aperture radar three-dimensional imaging device and method based on spiral two-dimensional scanning - Google Patents
Synthetic aperture radar three-dimensional imaging device and method based on spiral two-dimensional scanning Download PDFInfo
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Abstract
The invention belongs to the technical field of synthetic aperture radar microwave imaging, and particularly relates to a synthetic aperture radar three-dimensional imaging device based on spiral two-dimensional scanning, which comprises: the mechanical scanning structure is used for simultaneously driving the signal transmitter and the antenna to perform spiral ascending motion rotating at a constant speed; the signal emitter is used for emitting different linear frequency modulation stepping signals to different areas of a target scene to be detected according to a preset sampling interval, and sampling the target scene to be detected; the antenna is used for receiving different echo signals reflected from different areas of a target scene to be detected and inputting the echo signals to the echo receiver; the echo receiver is used for inputting the received different echo signals to the analog-to-digital converter; the analog-to-digital converter is used for performing analog-to-digital conversion on each echo signal to obtain a plurality of digital signals, and inputting the digital signals to the data processor; and the data processor is used for imaging the plurality of digital signals to obtain a three-dimensional image of the target scene to be detected.
Description
Technical Field
The invention belongs to the technical field of synthetic aperture radar microwave imaging, and particularly relates to a synthetic aperture radar three-dimensional imaging device and method based on spiral two-dimensional scanning.
Background
Synthetic Aperture laser Radar (SAL) is an application form of Synthetic Aperture Radar (SAR) in a laser band, and may also be called as laser SAR, and obtains a longitudinal high resolution by transmitting a broadband laser signal, and obtains an azimuth high resolution by a Synthetic Aperture (virtual Aperture) formed by azimuth motion, thereby forming an azimuth-distance two-dimensional image.
Because the synthetic aperture laser radar has a short wavelength, the synthetic aperture laser radar can obtain an image with 0.1m azimuth resolution by forming a very small angle (about four thousandths of a degree, 0.07mrad) by azimuth motion between the radar and the target, so that the synthetic aperture laser radar can carry out high-resolution imaging observation on a long-distance target at a high data rate in principle. The laser signal coherence is improved, and the technology of the synthetic aperture laser radar is possible to realize, and the application directions of the synthetic aperture laser radar include airborne/satellite-borne synthetic aperture laser radar imaging to the ground and ground-based synthetic aperture laser radar imaging to a space target. The aperture is additionally arranged in the third dimension of the synthetic aperture laser radar except the azimuth direction and the distance direction, such as the cross-track direction, and an array is formed, so that the cross-track resolution of the synthetic aperture laser radar can be improved, the azimuth direction-distance direction-cross-track direction three-dimensional imaging is realized, and the method has application value for topographic mapping and target identification. The aperture is added in the cross-track direction to form an array, and the method can also be used as a real aperture imaging mode based on the optical synthetic aperture.
In the existing imaging method, a one-dimensional sparse antenna array performs zigzag scanning in the horizontal and vertical directions to obtain echo signals of a plurality of planar sub-arrays, performs target imaging by combining recorded antenna coordinate position information, and finally splices images of the plurality of planar sub-arrays to obtain a final imaging result. However, in the existing imaging method, the array needs to use more antenna elements to scan the target scene, and the problems of high hardware cost and difficult control of the system volume exist.
In addition, in other existing imaging methods, a target echo is obtained in a polar coordinate format, convolution and integration are respectively completed in an angle domain and a frequency domain to obtain a two-dimensional imaging result of the target, and the height-direction resolution is obtained by overlapping scattering information on different height surfaces. However, this imaging method suffers from defocusing of objects at the edge of the scene.
The existing imaging method mainly aims at the imaging methods of a tomography SAR, an array SAR and a circumference SAR, the tomography has higher requirement on the stability of a base line in the scanning process, an antenna needs to be kept stable in the scene scanning process, the tomography SAR does not have foresight imaging capability, and the array SAR needs to meet the conditions of a large-size linear array and a sampling rate, so that the problems of high cost and large operation amount of an imaging system are caused; in the circular SAR mode, only the center of a scene can be scanned, and wide-area imaging cannot be performed.
Disclosure of Invention
In order to solve the defects in the prior art, the invention provides a three-dimensional imaging method based on a spiral two-dimensional scanning synthetic aperture radar, which aims at the problems of limited imaging area and high hardware cost of a multi-array SAR in the existing three-dimensional imaging mode and can realize three-dimensional imaging of an observation area.
The invention provides a synthetic aperture radar three-dimensional imaging device based on spiral two-dimensional scanning, which comprises a signal transmitter, a mechanical scanning mechanism, an antenna, an echo receiver, an analog-to-digital converter and a data processor, wherein the signal transmitter, the mechanical scanning mechanism, the antenna, the echo receiver, the analog-to-digital converter and the data processor are arranged on a synthetic aperture radar;
the mechanical scanning mechanism is respectively electrically connected with the signal transmitter, the antenna and the echo receiver; the echo receiver is electrically connected with the analog-to-digital converter; the analog-to-digital converter is electrically connected with the data processor;
the mechanical scanning structure is used for simultaneously driving the signal transmitter and the antenna to perform spiral ascending motion rotating at a constant speed;
the signal emitter is used for emitting different linear frequency modulation stepping signals to different areas of a target scene to be detected according to a preset sampling interval, and sampling the target scene to be detected;
the antenna is used for receiving different echo signals reflected from different areas of a target scene to be detected and inputting the echo signals to the echo receiver;
the echo receiver is used for inputting received different echo signals to the analog-to-digital converter;
the analog-to-digital converter is used for performing analog-to-digital conversion on each echo signal to obtain a plurality of digital signals, and inputting the digital signals to the data processor;
and the data processor is used for imaging the plurality of digital signals to obtain a three-dimensional image of the target scene to be detected, and finishing three-dimensional imaging.
As an improvement of the above technical solution, the mechanical scanning mechanism includes: a driver and a turntable; an antenna is suspended on the rotary table; the driver is arranged on the turntable and drives the turntable to rotate, so that the antenna is carried to do uniform spiral ascending motion, and irradiation to a target scene to be measured is completed.
As an improvement of the above technical solution, the data processor includes: the device comprises a phase compensation module, a signal synthesis module and a three-dimensional imaging module;
the phase compensation module is used for carrying out frequency domain transformation on each digital signal along the distance direction-the azimuth direction and then carrying out period and compensation function H one by one1Multiplying to realize the azimuth offset compensation of each digital signal;
wherein,
H1(fr,fa,z)＝exp[j×2×π×fa(nz-1)×Δτcr]
wherein H1(fr,faZ) compensating the azimuth offset of the digital signal; f. ofaIs a directional frequency domain; n iszThe number of sampling points in the height direction; f. ofrIs the distance to the frequency domain; z is the height coordinate of the sampling position; j is an imaginary unit; delta taucrTaking the remainder of the time lapse of one rotation of the antenna to the position sampling interval;
after the digital signals are subjected to wave beam domain transformation along the distance direction-height direction, the wave beam domain transformation is carried out one by onePerforming an orientation and compensation function H2Multiplying to realize the altitude direction offset compensation of the digital signal, obtaining the digital signal subjected to azimuth direction offset and altitude direction offset compensation, and taking the digital signal as a three-dimensional digital signal;
wherein,
wherein, KzIs a height direction wave number domain; v is the rising speed of the antenna module in the height direction;
the number of sampling points in the azimuth direction; kwIs a range direction wave number domain;
the signal synthesis module is used for carrying out frequency shift on the offset-compensated signal
Carrying out frequency spectrum shifting in a frequency domain, carrying out coherent addition on the frequency spectrums of the echo signals of each sub-band to obtain a synthesized frequency spectrum broadband signal, and combining the synthesized frequency spectrum broadband signal with a reference function H (f)r) Multiplying, and performing distance compression to obtain a compressed echo signal;
wherein, Δ f is the frequency step length of the step frequency modulation continuous wave; n is the subband signal ordinal number; n is the total number of the transmitted sub-band signals;
wherein, BnIs the sub-band bandwidth; gamma is the frequency modulation slope of the transmitting signal;
the three-dimensional imaging module is used for matching a function H according to3And uniformly compressing the compressed echo signals to obtain compressed signals:
wherein H3(Kw,Kφ,Kz) Is a compressed signal;
wherein,
wherein, KwIs a range direction wave number domain; kφIs an azimuth wave number domain; r isaIs the antenna rotation radius; beta is the product of the target position to be measured and the rotation radius of the antenna; z is a radical ofcThe central position of the synthetic aperture in the height direction; r iscA reference coordinate that is a reference position; kw maxIs the maximum value of the range direction wave number domain; kw minIs the minimum value of the distance direction wave number domain;
wherein the matching function is based on the selected reference position (r)c0,0) determination;
and transforming the compressed signal to a wave number domain, then performing interpolation in the wave number domain by using a wave number domain imaging algorithm and a sinc function, focusing the targets at the reference distance and the non-reference distance to obtain a three-dimensional image of the target scene to be measured, and finishing three-dimensional imaging.
The invention also provides a three-dimensional imaging method of the synthetic aperture radar based on spiral two-dimensional scanning, which comprises the following steps:
the mechanical scanning structure simultaneously drives the signal transmitter and the antenna to perform spiral ascending motion rotating at a constant speed;
the signal emitter emits different linear frequency modulation stepping signals to different areas of a target scene to be detected according to a preset sampling interval, and the target scene to be detected is sampled;
the antenna receives different echo signals reflected from different areas of a target scene to be detected and inputs the echo signals to an echo receiver;
the echo receiver inputs the received different echo signals to an analog-to-digital converter;
the analog-to-digital converter performs analog-to-digital conversion on each echo signal to obtain a plurality of digital signals, and the digital signals are input to the data processor;
and the data processor performs imaging processing on the plurality of digital signals to obtain a three-dimensional image of the target scene to be detected, so as to complete three-dimensional imaging.
As one improvement of the above technical solution, the data processor performs imaging processing on the plurality of digital signals to obtain a three-dimensional image of a target scene to be measured, and completes three-dimensional imaging; the specific process comprises the following steps:
the phase compensation module performs frequency domain transformation on each digital signal along the distance direction-azimuth direction, and then performs period and compensation function H one by one1Multiplying to realize the azimuth offset compensation of each digital signal;
wherein,
H1(fr,fa,z)＝exp[j×2×π×fa(nz-1)×Δτcr]
wherein H1(fr,faZ) compensating the azimuth offset of the digital signal; f. ofaIs a directional frequency domain; n iszThe number of sampling points in the height direction; f. ofrIs the distance to the frequency domain; z is the height coordinate of the sampling position; j is an imaginary unit; delta taucrTaking the remainder of the time lapse of one rotation of the antenna to the position sampling interval;
after the digital signals are subjected to wave beam domain transformation along the distance direction-height direction, the azimuth and compensation functions H are carried out one by one2Multiplying to realize the altitude direction offset compensation of the digital signal, obtaining the digital signal subjected to azimuth direction offset and altitude direction offset compensation, and taking the digital signal as a three-dimensional digital signal;
wherein,
wherein, KzIs a height direction wave number domain; v is the rising speed of the antenna module in the height direction;
the number of sampling points in the azimuth direction; kwIs a range direction wave number domain;
the signal synthesis module performs frequency shift on the offset-compensated signal
Carrying out frequency spectrum shifting in a frequency domain, carrying out coherent addition on the frequency spectrums of the echo signals of each sub-band to obtain a synthesized frequency spectrum broadband signal, and combining the synthesized frequency spectrum broadband signal with a reference function H (f)r) Multiplying, and performing distance compression to obtain a compressed echo signal;
wherein, Δ f is the frequency step length of the step frequency modulation continuous wave; n is the subband signal ordinal number; n is the total number of the transmitted sub-band signals;
wherein, BnIs the sub-band bandwidth; gamma is the frequency modulation slope of the transmitting signal;
the three-dimensional imaging module is according to the matching function H3And uniformly compressing the compressed echo signals to obtain compressed signals:
wherein H3(Kw,Kφ,Kz) Is a compressed signal;
wherein,
wherein, KwIs a range direction wave number domain; kφIs an azimuth wave number domain; r isaIs the antenna rotation radius; beta is the product of the target position to be measured and the rotation radius of the antenna; z is a radical ofcIs the central position of the synthetic aperture in the height direction；rcA reference coordinate that is a reference position; kw maxIs the maximum value of the range direction wave number domain; kw minIs the minimum value of the distance direction wave number domain;
wherein the matching function is based on the selected reference position (r)c0,0) determination;
and transforming the compressed signal to a wave number domain, then performing interpolation in the wave number domain by using a wave number domain imaging algorithm and a sinc function, focusing the targets at the reference distance and the non-reference distance to obtain a three-dimensional image of the target scene to be measured, and finishing three-dimensional imaging.
Compared with the prior art, the invention has the beneficial effects that:
1. the method adopts a spiral ascending scanning mode, and realizes wide-area imaging of an imaging area in a short time;
2. the method of the invention adopts the step frequency modulation continuous wave signal as the transmitting signal, improves the imaging precision and reduces the hardware requirement on the analog-digital conversion module;
3. the method of the invention adopts a targeted imaging algorithm to perform accurate imaging processing aiming at the actual motion track of the signal emitter.
Drawings
Fig. 1 is a schematic structural diagram of a spiral-based two-dimensional scanning synthetic aperture radar three-dimensional imaging device of the invention.
Detailed Description
The invention will now be further described with reference to the accompanying drawings.
The invention provides a three-dimensional imaging device for a synthetic aperture radar based on spiral two-dimensional scanning.A mechanical scanning mechanism drives a signal transmitter to do spiral ascending motion rotating at a constant speed and simultaneously drives an antenna to do spiral ascending motion rotating; in the ascending process, the signal emitter emits a linear frequency modulation stepping signal to perform spiral ascending scanning on a target scene to be detected at specified pulse repetition intervals, analog-to-digital conversion is performed on a plurality of acquired analog signals respectively to obtain a plurality of digital signals, and the digital signals are input to the data processor to perform imaging processing to obtain a three-dimensional imaging result of the target scene to be detected. Compared with the traditional synthetic aperture radar three-dimensional imaging method, the method has the advantages that an annular imaging area is formed in the area irradiated by the radar beam after the complete circular track flight observation, the upward scanning speed of the azimuth is improved within the same observation time, and a larger imaging area and a faster imaging speed are obtained.
As shown in fig. 1, the imaging device is an ultra-wideband three-dimensional radar imaging device based on spiral two-dimensional scanning, and comprises a signal transmitter, a mechanical scanning mechanism, an antenna, an echo receiver, an analog-to-digital converter and a data processor, wherein the signal transmitter, the mechanical scanning mechanism, the antenna, the echo receiver, the analog-to-digital converter and the data processor are arranged on a synthetic aperture radar;
the mechanical scanning mechanism is respectively electrically connected with the signal transmitter, the antenna and the echo receiver; the echo receiver is electrically connected with the analog-to-digital converter; the analog-to-digital converter is electrically connected with the data processor;
the mechanical scanning structure is used for simultaneously driving the signal transmitter and the antenna to perform spiral ascending motion rotating at a constant speed;
specifically, the mechanical scanning mechanism includes: a driver and a turntable; an antenna is suspended on the rotary table; the driver is arranged on the turntable and drives the turntable to rotate, so that the antenna is carried to do uniform spiral ascending motion, and irradiation to a target scene to be measured is completed.
The signal emitter is used for emitting different linear frequency modulation stepping signals to different areas of a target scene to be detected according to a preset sampling interval, and sampling the target scene to be detected;
the linear frequency modulation stepping signal is an electromagnetic wave signal which is a stepping frequency modulation signal, the frequency stepping number is 6, and the frequency is 3GHz-9 GHz.
The signal transmitter can be realized by updating a tuning voltage corresponding to a frequency division ratio by a frequency division phase discriminator according to a fixed step amount, then performing loop filtering, and driving a voltage-controlled oscillator by the filtered output to generate a step frequency modulation continuous wave.
The antenna is used for receiving different echo signals reflected from different areas of a target scene to be detected and inputting the echo signals to the echo receiver;
the echo receiver is used for inputting received different echo signals to the analog-to-digital converter;
the analog-to-digital converter is used for performing analog-to-digital conversion on each echo signal to obtain a plurality of digital signals, and inputting the digital signals to the data processor;
wherein the obtained plurality of digital signals are stored in the form of two-dimensional digital signals.
And the data processor is used for imaging the plurality of digital signals to obtain a three-dimensional image of the target scene to be detected, and finishing three-dimensional imaging.
Specifically, the data processor includes: the device comprises a phase compensation module, a signal synthesis module and a three-dimensional imaging module;
the phase compensation module is used for carrying out frequency domain transformation on each digital signal along the distance direction-the azimuth direction and then carrying out period and compensation function H one by one1Multiplying to realize the azimuth offset compensation of each digital signal;
wherein,
wherein H1(fr,fa,z)＝exp[j×2×π×fa(nz-1)×Δτcr]
Wherein H1(fr,faZ) compensating the azimuth offset of the digital signal; f. ofaIs a directional frequency domain; n iszThe number of sampling points in the height direction; f. ofrIs the distance to the frequency domain; z is the height coordinate of the sampling position; j is an imaginary unit; delta taucrTaking the remainder of the time lapse of one rotation of the antenna to the position sampling interval;
after the same digital signals are subjected to beam domain transformation along the distance direction-height direction, the azimuth and compensation functions H are carried out one by one2Multiplying to realize the altitude direction offset compensation of the digital signal, obtaining the digital signal subjected to azimuth direction offset and altitude direction offset compensation, and taking the digital signal as a three-dimensional digital signal;
wherein,
wherein, KzIs a height direction wave number domain; v is the rising speed of the antenna module in the height direction;
the number of sampling points in the azimuth direction; kwIs a range direction wave number domain;
the signal synthesis module is used for carrying out frequency shift on the offset-compensated signal
Carrying out frequency spectrum shifting in a frequency domain, carrying out coherent addition on the frequency spectrums of the echo signals of each sub-band to obtain a synthesized frequency spectrum broadband signal, and combining the synthesized frequency spectrum broadband signal with a reference function H (f)r) Multiplying, and performing distance compression to obtain a compressed echo signal;
wherein, Δ f is the frequency step length of the step frequency modulation continuous wave; n is the subband signal ordinal number; n is the total number of the transmitted sub-band signals;
wherein, BnIs the sub-band bandwidth; gamma is the frequency modulation slope of the transmitting signal;
the three-dimensional imaging module is used for matching a function H according to3And uniformly compressing the compressed echo signals to obtain compressed signals:
wherein H3(Kw,Kφ,Kz) Is a compressed signal;
wherein,
wherein, KwIs a range direction wave number domain; kφIs an azimuth wave number domain; r isaIs the antenna rotation radius; beta is the product of the target position to be measured and the rotation radius of the antenna; z is a radical ofcThe central position of the synthetic aperture in the height direction; r iscA reference coordinate that is a reference position; kw maxIs the maximum value of the range direction wave number domain; kw minIs the minimum value of the distance direction wave number domain;
wherein the matching function is based on the selected reference position (r)c0,0) determination;
and transforming the compressed signal to a wave number domain, then performing interpolation in the wave number domain by using a wave number domain imaging algorithm and a sinc function, focusing the targets at the reference distance and the non-reference distance to obtain a three-dimensional image of the target scene to be measured, and finishing three-dimensional imaging.
The antenna rotates and ascends at the same time under the driving of the mechanical scanning mechanism, namely the spiral ascending motion rotating at a constant speed, the signal transmitter transmits stepping frequency modulation continuous wave signals to a target scene to be detected to the outside in the spiral rotating and ascending process of the mechanical scanning mechanism, the reflected echo signals are received by the signal receiver after being reflected by the target scene to be detected, and analog-to-digital conversion is carried out on the echo signals respectively to obtain a plurality of digital signals.
The invention also provides a synthetic aperture radar three-dimensional imaging method based on spiral two-dimensional scanning, the method adopts a stepping continuous frequency modulation signal, the size requirement on the system is reduced, meanwhile, the antenna module does spiral ascending movement under the carrying of the mechanical scanning module, and the rapid wide area imaging of the scene can be completed in the movement process.
The signal transmitter generates electromagnetic wave signals, the mechanical scanning module carries the antenna module to rotate at a constant speed and simultaneously perform ascending movement at a constant speed, and the echo receiving module receives echo signals reflected from an observation target; the analog-to-digital conversion module converts the reflected signals into digital signals, and the data processing module performs imaging processing on the echo data to obtain a three-dimensional complex image of the observation target.
The method comprises the following steps:
the mechanical scanning structure simultaneously drives the signal transmitter and the antenna to perform spiral ascending motion rotating at a constant speed;
the signal emitter emits different linear frequency modulation stepping signals to different areas of a target scene to be detected according to a preset sampling interval, and the target scene to be detected is sampled;
the antenna receives different echo signals reflected from different areas of a target scene to be detected and inputs the echo signals to an echo receiver;
the echo receiver inputs the received different echo signals to an analog-to-digital converter;
the analog-to-digital converter performs analog-to-digital conversion on each echo signal to obtain a plurality of digital signals, and the digital signals are input to the data processor;
and the data processor performs imaging processing on the plurality of digital signals to obtain a three-dimensional image of the target scene to be detected, so as to complete three-dimensional imaging.
Specifically, the echo data azimuth offset and the echo data altitude offset in the step 1) are compensated, and the purpose is to correct the position offset caused by the falling line rotation rising by using two compensation functions.
After each digital signal is subjected to frequency domain transformation along the distance direction-the azimuth direction, the period and the compensation function H are carried out one by one1Multiplying to realize the azimuth offset compensation of each digital signal;
wherein,
H1(fr,fa,z)＝exp[j×2×π×fa(nz-1)×Δτcr]
wherein H1(fr,faZ) compensating the azimuth offset of the digital signal; f. ofaIs a directional frequency domain; n iszThe number of sampling points in the height direction; f. ofrIs the distance to the frequency domain; z is the height coordinate of the sampling position; j is an imaginary unit; delta taucrTaking the remainder of the time lapse of one rotation of the antenna to the position sampling interval;
after the same digital signals are subjected to beam domain transformation along the distance direction-height direction, the azimuth and compensation functions H are carried out one by one2Multiplying to realize the altitude direction offset compensation of the digital signal, obtaining the digital signal subjected to azimuth direction offset and altitude direction offset compensation, and taking the digital signal as a three-dimensional digital signal;
wherein,
wherein, KzIs a height direction wave number domain; v is the rising speed of the antenna module in the height direction;
the number of sampling points in the azimuth direction; kwIs a range direction wave number domain;
repeating the above process for each digital signal to obtain a plurality of three-dimensional digital signals;
and 2) synthesizing the sub-pulse echo signals into broadband signals.
For offset compensated signal by frequency shift amount
Carrying out frequency spectrum shifting in a frequency domain, carrying out coherent addition on the frequency spectrums of the echo signals of all sub-bands to obtain synthesized frequency spectrum broadband signals, multiplying the synthesized frequency spectrum broadband signals by a reference function, and carrying out distance compression to obtain compressed echo signals;
wherein, Δ f is the frequency step length of the step frequency modulation continuous wave; n is the subband signal ordinal number; n is the total number of the transmitted sub-band signals;
wherein, BnIs the sub-band bandwidth; gamma is the frequency modulation slope of the transmitting signal;
step 3) according to the matching function H3And uniformly compressing the compressed echo signals to obtain compressed signals:
wherein H3(Kw,Kφ,Kz) Is a compressed signal;
wherein,
wherein, KwIs a range direction wave number domain; kφIs an azimuth wave number domain; r isaIs the antenna rotation radius; beta is the product of the target position to be measured and the rotation radius of the antenna; z is a radical ofcThe central position of the synthetic aperture in the height direction; r iscA reference coordinate that is a reference position; kw maxIs the maximum value of the range direction wave number domain; kw minIs the minimum value of the distance direction wave number domain;
wherein the matching function is based on the selected reference position (r)c0,0) determination;
and transforming the compressed signal to a wave number domain, then performing interpolation in the wave number domain by using a wave number domain imaging algorithm and a sinc function, focusing the targets at the reference distance and the non-reference distance to obtain a three-dimensional image of the target scene to be measured, and finishing three-dimensional imaging.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (5)
1. A synthetic aperture radar three-dimensional imaging device based on spiral two-dimensional scanning is characterized by comprising a signal transmitter, a mechanical scanning mechanism, an antenna, an echo receiver, an analog-to-digital converter and a data processor, wherein the signal transmitter, the mechanical scanning mechanism, the antenna, the echo receiver, the analog-to-digital converter and the data processor are arranged on a synthetic aperture radar;
the mechanical scanning mechanism is respectively electrically connected with the signal transmitter, the antenna and the echo receiver; the echo receiver is electrically connected with the analog-to-digital converter; the analog-to-digital converter is electrically connected with the data processor;
the mechanical scanning structure is used for simultaneously driving the signal transmitter and the antenna to perform spiral ascending motion rotating at a constant speed;
the signal emitter is used for emitting different linear frequency modulation stepping signals to different areas of a target scene to be detected according to a preset sampling interval, and sampling the target scene to be detected;
the antenna is used for receiving different echo signals reflected from different areas of a target scene to be detected and inputting the echo signals to the echo receiver;
the echo receiver is used for inputting received different echo signals to the analog-to-digital converter;
the analog-to-digital converter is used for performing analog-to-digital conversion on each echo signal to obtain a plurality of digital signals, and inputting the digital signals to the data processor;
and the data processor is used for imaging the plurality of digital signals to obtain a three-dimensional image of the target scene to be detected, and finishing three-dimensional imaging.
2. The spiral two-dimensional scanning synthetic aperture radar based three-dimensional imaging device according to claim 1, wherein said mechanical scanning mechanism comprises: a driver and a turntable; an antenna is suspended on the rotary table; the driver is arranged on the turntable and drives the turntable to rotate, so that the antenna is carried to do uniform spiral ascending motion, and irradiation to a target scene to be measured is completed.
3. The spiral two-dimensional scanning synthetic aperture radar based three-dimensional imaging device according to claim 1, wherein said data processor comprises: the device comprises a phase compensation module, a signal synthesis module and a three-dimensional imaging module;
the phase compensation module is used for carrying out frequency domain variation on each digital signal along the distance direction-the azimuth directionAfter the conversion, the period and the compensation function H are carried out one by one1Multiplying to realize the azimuth offset compensation of each digital signal;
wherein,
H1(fr,fa,z)＝exp[j×2×π×fa(nz-1)×Δτcr]
wherein H1(fr,faZ) compensating the azimuth offset of the digital signal; f. ofaIs a directional frequency domain; n iszThe number of sampling points in the height direction; f. ofrIs the distance to the frequency domain; z is the height coordinate of the sampling position; j is an imaginary unit; delta taucrTaking the remainder of the time lapse of one rotation of the antenna to the position sampling interval;
after the digital signals are subjected to wave beam domain transformation along the distance direction-height direction, the azimuth and compensation functions H are carried out one by one2Multiplying to realize the altitude direction offset compensation of the digital signal, obtaining the digital signal subjected to azimuth direction offset and altitude direction offset compensation, and taking the digital signal as a three-dimensional digital signal;
wherein,
wherein, KzIs a height direction wave number domain; v is the rising speed of the antenna module in the height direction;
the number of sampling points in the azimuth direction; kwIs a range direction wave number domain;
the signal synthesis module is used for carrying out frequency shift on the offset-compensated signal
Carrying out frequency spectrum shifting in a frequency domain, carrying out coherent addition on the frequency spectrums of the echo signals of each sub-band to obtain a synthesized frequency spectrum broadband signal, and combining the synthesized frequency spectrum broadband signal with a reference function H (f)r) Multiplying, and performing distance compression to obtain a compressed echo signal;
wherein, Δ f is the frequency step length of the step frequency modulation continuous wave; n is the subband signal ordinal number; n is the total number of the transmitted sub-band signals;
wherein, BnIs the sub-band bandwidth; gamma is the frequency modulation slope of the transmitting signal;
the three-dimensional imaging module is used for matching a function H according to3And uniformly compressing the compressed echo signals to obtain compressed signals:
wherein H3(Kw,Kφ,Kz) Is a compressed signal;
wherein,
wherein, KwIs a range direction wave number domain; kφIs an azimuth wave number domain; r isaIs the antenna rotation radius; beta is the product of the target position to be measured and the rotation radius of the antenna; z is a radical ofcThe central position of the synthetic aperture in the height direction; r iscA reference coordinate that is a reference position; kwmaxIs the maximum value of the range direction wave number domain; kwminIs the minimum value of the distance direction wave number domain;
wherein the matching function is based on the selected reference position (r)c0,0) determination;
and transforming the compressed signal to a wave number domain, then performing interpolation in the wave number domain by using a wave number domain imaging algorithm and a sinc function, focusing the targets at the reference distance and the non-reference distance to obtain a three-dimensional image of the target scene to be measured, and finishing three-dimensional imaging.
4. A three-dimensional imaging method based on a spiral two-dimensional scanning synthetic aperture radar comprises the following steps:
the mechanical scanning structure simultaneously drives the signal transmitter and the antenna to perform spiral ascending motion rotating at a constant speed;
the signal emitter emits different linear frequency modulation stepping signals to different areas of a target scene to be detected according to a preset sampling interval, and the target scene to be detected is sampled;
the antenna receives different echo signals reflected from different areas of a target scene to be detected and inputs the echo signals to an echo receiver;
the echo receiver inputs the received different echo signals to an analog-to-digital converter;
the analog-to-digital converter performs analog-to-digital conversion on each echo signal to obtain a plurality of digital signals, and the digital signals are input to the data processor;
and the data processor performs imaging processing on the plurality of digital signals to obtain a three-dimensional image of the target scene to be detected, so as to complete three-dimensional imaging.
5. The method for three-dimensional imaging of synthetic aperture radar based on spiral two-dimensional scanning according to claim 4, wherein the data processor performs imaging processing on a plurality of digital signals to obtain a three-dimensional image of a target scene to be measured, and three-dimensional imaging is completed; the specific process comprises the following steps:
the phase compensation module performs frequency domain transformation on each digital signal along the distance direction-azimuth direction, and then performs period and compensation function H one by one1Multiplying to realize the azimuth offset compensation of each digital signal;
wherein,
H1(fr,fa,z)＝exp[j×2×π×fa(nz-1)×Δτcr]
wherein H1(fr,faZ) compensating the azimuth offset of the digital signal; f. ofaIs a squareTo the frequency domain; n iszThe number of sampling points in the height direction; f. ofrIs the distance to the frequency domain; z is the height coordinate of the sampling position; j is an imaginary unit; delta taucrTaking the remainder of the time lapse of one rotation of the antenna to the position sampling interval;
after the digital signals are subjected to wave beam domain transformation along the distance direction-height direction, the azimuth and compensation functions H are carried out one by one2Multiplying to realize the altitude direction offset compensation of the digital signal, obtaining the digital signal subjected to azimuth direction offset and altitude direction offset compensation, and taking the digital signal as a three-dimensional digital signal;
wherein,
wherein, KzIs a height direction wave number domain; v is the rising speed of the antenna module in the height direction;
the number of sampling points in the azimuth direction; kwIs a range direction wave number domain;
the signal synthesis module performs frequency shift on the offset-compensated signal
Carrying out frequency spectrum shifting in a frequency domain, carrying out coherent addition on the frequency spectrums of the echo signals of each sub-band to obtain a synthesized frequency spectrum broadband signal, and combining the synthesized frequency spectrum broadband signal with a reference function H (f)r) Multiplying, and performing distance compression to obtain a compressed echo signal;
wherein, Δ f is the frequency step length of the step frequency modulation continuous wave; n is the subband signal ordinal number; n is the total number of the transmitted sub-band signals;
wherein, BnIs the sub-band bandwidth; gamma is the frequency modulation slope of the transmitting signal;
the three-dimensional imaging module is according to the matching function H3And uniformly compressing the compressed echo signals to obtain compressed signals:
wherein H3(Kw,Kφ,Kz) Is a compressed signal;
wherein,
wherein, KwIs a range direction wave number domain; kφIs an azimuth wave number domain; r isaIs the antenna rotation radius; beta is the product of the target position to be measured and the rotation radius of the antenna; z is a radical ofcThe central position of the synthetic aperture in the height direction; r iscA reference coordinate that is a reference position; kwmaxIs the maximum value of the range direction wave number domain; kwminIs the minimum value of the distance direction wave number domain;
wherein the matching function is based on the selected reference position (r)c0,0) determination;
and transforming the compressed signal to a wave number domain, then performing interpolation in the wave number domain by using a wave number domain imaging algorithm and a sinc function, focusing the targets at the reference distance and the non-reference distance to obtain a three-dimensional image of the target scene to be measured, and finishing three-dimensional imaging.
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