CN105629231A - Method and system for splicing SAR sub-aperture - Google Patents

Abstract

A sub-aperture splicing method for SAR, comprising: extracting sub-aperture azimuth direction spectrum shift data from sub-aperture imaging data information; using a circular shift algorithm to split the sub-aperture azimuth direction spectrum shift data to obtain sub-aperture azimuth direction order Data; using the non-first sub-aperture extraction method to extract the effective data information of the next sub-aperture for obtaining the next sub-aperture imaging data information; extracting the next sub-aperture azimuth direction spectrum shift data in the next sub-aperture imaging data information; using The circular shift algorithm splits the azimuth shift data of the next sub-aperture to obtain the azimuth sequence data of the next sub-aperture for splicing with the sub-aperture. The invention can effectively reduce the calculation amount of imaging processing and improve the data processing speed.

Description

A SAR sub-aperture splicing method and system

technical field

The invention relates to the field of SAR imaging, in particular to a SAR sub-aperture splicing method and system.

Background technique

The spaceborne sliding spotlight mode is a new mode of SAR satellites at present. By changing the irradiation direction of the azimuth beam, the length of the synthetic aperture of the target point is increased, and the resolution of the azimuth direction is improved, up to 0.5m. In order to ensure a certain observation bandwidth, like the strip mode, the azimuth sampling frequency of the sliding beamforming mode cannot be increased arbitrarily; on the other hand, due to the increase of the synthetic aperture length, the azimuth bandwidth of the sliding beamforming mode far exceeds the sampling frequency frequency. The processing methods for sliding beamforming mode data are mainly divided into the following two types in terms of ideas:

1. Two-step imaging processing algorithm. This algorithm was first used to process data in spotlight mode. The first step is to perform deskewing operation through azimuth derotation processing to avoid aliasing spectrum aliasing. The second step uses traditional focusing imaging algorithm Perform focus processing.

2. Sub-aperture processing algorithm. In order to alleviate the undersampling of azimuth signals, the idea of sub-aperture processing is to first divide the azimuth data into blocks to alleviate the aliasing of the azimuth spectrum. After focusing processing, the sub-aperture splicing is completed.

Among the above two algorithms, the two-step processing algorithm was originally proposed for the beamforming mode processing algorithm, so it has certain limitations when processing sliding beamforming mode data;

The sub-aperture processing algorithm needs to divide the original data into blocks, which is suitable for parallel high-speed computing systems. The sub-aperture processing in the prior art is to complete the splicing of sub-apertures in the time domain, and all of them are in the process of imaging algorithm processing. Aperture splicing, this method increases the calculation amount of imaging processing, which is not conducive to the improvement of imaging speed.

Therefore, how to break through the limitations of the two-step method, and reduce the amount of imaging processing data on the basis of dividing the sub-apertures to complete the sub-aperture splicing in the azimuth direction becomes the key problem to be solved in the present invention.

Contents of the invention

The invention provides a SAR sub-aperture splicing method and system. The method is used to perform fast imaging and display on the data of the spaceborne SAR sliding spotlight mode, and the sub-apertures are spliced after the imaging algorithm processing process, effectively reducing the cost of imaging processing. The amount of calculation is reduced, and the quick view processing speed is improved. A SAR sub-aperture splicing method of the present invention comprises,

extracting the sub-aperture azimuth direction spectrum shift data from the imaging data information of the sub-aperture;

Use the circular shift algorithm to split the sub-aperture azimuth spectrum shift data to obtain sub-aperture azimuth sequence data;

Using a non-first sub-aperture extraction method to extract effective data information of the next sub-aperture for obtaining imaging data information of the next sub-aperture;

Extracting the next sub-aperture azimuth spectrum shift data from the next sub-aperture imaging data information;

A circular shift algorithm is used to split the azimuth spectrum shift data of the next sub-aperture to obtain the azimuth sequence data of the next sub-aperture for splicing with the sub-aperture.

According to the above method of the present invention, the use of a circular shift algorithm to split the current sub-aperture azimuth direction spectrum shift data includes:

Calculate the number of circular shifts according to the spectrum range and pulse repetition frequency of the sub-aperture azimuth shift data;

After the start frequency and stop frequency of the original fixed bandwidth are shifted according to the number of circular shifts obtained, the start frequency and stop frequency of the new fixed bandwidth are obtained correspondingly;

According to the preset conditions and the obtained start frequency and stop frequency of the newly-built fixed bandwidth, the sub-aperture azimuth spectrum order data is obtained within the range of the frequency range whose starting point is zero and the ending point is the pulse repetition frequency.

According to above-mentioned method of the present invention, also comprise:

The sub-aperture minimum frequency is obtained from the current sub-aperture azimuth shift data, and the number of circular shifts is obtained by rounding the quotient of the sub-aperture minimum frequency and the pulse repetition frequency.

According to the above method of the present invention, the acquisition of the start frequency and stop frequency of the newly-built fixed bandwidth includes:

The sum of the product obtained by multiplying the number of circular shifts by the pulse repetition frequency and the initial frequency of the original fixed bandwidth is added to obtain the initial frequency of the new fixed bandwidth after the circular shift;

The sum of the product obtained by multiplying the number of circular shifts by the pulse repetition frequency and the stop frequency of the original fixed bandwidth is obtained to obtain the stop frequency of the new fixed bandwidth after the circular shift.

According to the above method of the present invention, the preset conditions include:

The new bandwidth starting point after the circular shift is greater than zero, and,

The sum of the product obtained by multiplying the number of circular shifts by one and the pulse repetition frequency and the initial frequency of the original fixed bandwidth is less than the pulse repetition frequency.

According to the above method of the present invention, the non-first sub-aperture extraction method is used to extract the effective data information of the next sub-aperture, including:

According to the time-frequency relationship of the sub-aperture, the time-frequency characteristics of the effective end target point of the sub-aperture are obtained;

According to the time-frequency relationship of the sub-aperture, the time-frequency characteristics of the instantaneous lowest frequency of the entire scene are obtained;

Acquiring the position of the next sub-aperture in the echo of the entire scene according to the time-frequency characteristic of the effective end target point of the sub-aperture and the time-frequency characteristic of the instantaneous lowest frequency of the entire scene;

According to the position of the next sub-aperture in the echo of the whole scene, effective data information of the next sub-aperture is extracted from the echo data of the whole scene.

According to the above method of the present invention, the position of the next sub-aperture in the echo of the entire scene is obtained according to the time-frequency characteristics of the effective end target point of the sub-aperture and the time-frequency characteristics of the instantaneous lowest frequency of the entire scene, including :

Acquiring the next sub-aperture end time point according to the time-frequency characteristic of the effective end target point of the sub-aperture and the time-frequency characteristic of the instantaneous lowest frequency of the whole scene;

Acquiring the start time point of the next sub-aperture according to the end time point of the next sub-aperture and the time length of the sub-aperture;

According to the start time point of the next sub-aperture and the end time point of the next sub-aperture, the position of the next sub-aperture in the echo of the whole scene is acquired.

According to another aspect of the present invention, there is also provided a SAR sub-aperture splicing system, including:

Shift data unit: it is used to extract the sub-aperture azimuth direction spectrum shift data from the imaging data information of the sub-aperture;

Sequential data unit: it uses a circular shift algorithm to split the sub-aperture azimuth spectrum shift data to obtain sub-aperture azimuth sequential data;

The next imaging data unit: it uses the non-first sub-aperture extraction method to extract the effective data information of the next sub-aperture, and is used to obtain the imaging data information of the next sub-aperture;

The next shift data unit: it is used to extract the next sub-aperture azimuth spectrum shift data in the next sub-aperture imaging data information;

Next sequential data unit: it uses a circular shift algorithm to split the next sub-aperture azimuth spectrum shift data to obtain the next sub-aperture azimuth sequential data sequence for splicing with the sub-aperture.

The beneficial effect of the present invention compared with prior art is:

The method of the present invention obtains the imaging data information of the sub-aperture after the imaging algorithm processing process, and then extracts the sub-aperture azimuth direction spectrum shift data from the sub-aperture imaging data information; bit data to obtain sub-aperture azimuth sequence data; use the non-first sub-aperture extraction method to extract the effective data information of the next sub-aperture, which is used to obtain the next sub-aperture imaging data information; extract the next sub-aperture imaging data information from the next sub-aperture imaging data information The azimuth spectrum shift data of the aperture; use the circular shift algorithm to split the azimuth spectrum shift data of the next sub-aperture, and obtain the azimuth sequence data of the next sub-aperture for splicing with the sub-aperture. This method breaks through the limitations of the two-step method, and reduces the amount of imaging processing data on the basis of dividing the sub-apertures to complete the azimuth direction sub-aperture splicing, effectively reducing the calculation amount of imaging processing, and improving the fast-view processing speed.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For Those of ordinary skill in the art can also obtain other drawings based on these drawings without any creative effort.

Fig. 1 is the processing flowchart of a kind of SAR sub-aperture mosaic method that embodiment 1 provides;

Fig. 2 is the processing flowchart of a kind of SAR sub-aperture mosaic method that embodiment 2 provides;

Fig. 3 is the flow chart of using ECS (ExtendedChirpScaling) combined with SPECAN imaging algorithm imaging in Embodiment 2 of the present invention;

Fig. 4 is the geometric relationship between the star and the earth provided by Embodiment 2 of the present invention;

5 is a schematic diagram of a non-first sub-aperture extraction method provided in Embodiment 2 of the present invention;

FIG. 6 is a system block diagram of a SAR sub-aperture stitching system provided by the third embodiment.

detailed description

The implementation of the present invention will be described in detail below in conjunction with the accompanying drawings and examples, so as to fully understand and implement the process of how to apply technical means to solve technical problems and achieve technical effects in the present invention. It should be noted that, as long as there is no conflict, each embodiment and each feature in each embodiment of the present invention can be combined with each other, and the formed technical solutions are all within the protection scope of the present invention.

first embodiment

The processing flowchart of a SAR sub-aperture splicing method provided by Embodiment 1 of the present invention is shown in FIG. 1 , including the following processing steps:

Step S110, extracting sub-aperture azimuth spectrum shift data from sub-aperture imaging data information;

Step S120, using a circular shift algorithm to split the sub-aperture azimuth spectrum shift data to obtain sub-aperture azimuth sequence data;

Step S130, using the non-first sub-aperture extraction method to extract the effective data information of the next sub-aperture for obtaining the imaging data information of the next sub-aperture;

Step S140, extracting the next sub-aperture azimuth spectrum shift data from the next sub-aperture imaging data information;

Step S150, using a circular shift algorithm to split the azimuth shift data of the next sub-aperture to obtain the azimuth sequence data of the next sub-aperture for splicing with the sub-aperture.

second embodiment

The processing flowchart of a SAR sub-aperture splicing method provided by Embodiment 2 of the present invention is shown in FIG. 2 , including the following processing steps:

Step S210, using a preset imaging algorithm to process the effective information of the echo data of the current sub-aperture, and obtain the imaging data information of the current sub-aperture;

In this embodiment, the ECS algorithm and the SPECAN algorithm are used as the preset imaging algorithm to process the effective information of the current sub-aperture echo data, as shown in Figure 3, including the following steps:

Step A, calculating the Doppler parameters of the current sub-aperture according to the effective information of the first sub-aperture echo data extracted from the echo data of the whole scene;

Step B, extracting azimuth sampling data from the effective information of the current sub-aperture echo data, performing azimuth short-point discrete Fourier transform processing on the azimuth sampling data, and then performing ChirpScaling factor multiplication processing;

Step C, extract the range sampling data from the effective information of the current sub-aperture echo data, and sequentially perform discrete Fourier transform, range compression, secondary range compression, range migration correction, and range inverse Fourier transform on the range sampling data and residual factor compensation processing;

Step D, perform azimuth focusing processing on the data in the azimuth that has been multiplied by the ChirpScaling factor, and then perform inverse Fourier transform on the sampling data of the short points in the azimuth, and combine the Doppler parameters of the current sub-aperture to focus on the short points in the azimuth The sampling data is subjected to deskewing processing, and Fourier transform is performed on the azimuth short-point sampling data after the deskewing processing to obtain a sub-aperture reduced resolution image composed of azimuth spectrum shift data and range sampling data in the time domain.

Step S220, extracting sub-aperture azimuth spectrum shift data from sub-aperture imaging data information;

Step S230, using a circular shift algorithm to split the sub-aperture azimuth spectrum shift data to obtain sub-aperture azimuth sequence data;

In this embodiment, the circular shift algorithm is used to split the current sub-aperture azimuth spectrum shift data:

Calculate the number of circular shifts according to the spectrum range and pulse repetition frequency of the sub-aperture azimuth shift data;

Specifically, the sub-aperture minimum frequency is obtained in the current sub-aperture azimuth shift data, and the quotient of the sub-aperture minimum frequency and the pulse repetition frequency is rounded to obtain the number of circular shifts;

After the start frequency and stop frequency of the original fixed bandwidth are shifted according to the number of circular shifts obtained, the start frequency and stop frequency of the new fixed bandwidth are obtained correspondingly;

According to the preset conditions and the obtained start frequency and stop frequency of the newly-built fixed bandwidth, the sub-aperture azimuth spectrum order data is obtained within the range of the frequency range whose starting point is zero and the ending point is the pulse repetition frequency.

The acquisition of the start frequency and stop frequency of the new fixed bandwidth includes:

The sum of the product obtained by multiplying the number of circular shifts by the pulse repetition frequency and the initial frequency of the original fixed bandwidth is added to obtain the initial frequency of the new fixed bandwidth after the circular shift;

The sum of the product obtained by multiplying the number of circular shifts by the pulse repetition frequency and the stop frequency of the original fixed bandwidth is obtained to obtain the stop frequency of the new fixed bandwidth after the circular shift.

The preset conditions set include:

The new bandwidth starting point after the circular shift is greater than zero, and,

The sum of the product obtained by multiplying the number of circular shifts by one and the pulse repetition frequency and the starting frequency of the original fixed bandwidth is less than the pulse repetition frequency.

According to the preset conditions and the obtained start frequency and stop frequency of the newly-built fixed bandwidth, the sub-aperture azimuth direction spectrum order data is obtained within the frequency range where the start point is zero and the end point is the pulse repetition frequency, including:

Carry out interval division on the interval segment from the zero start frequency to the pulse repetition frequency, and obtain the D1 interval segment, the D2 interval segment and the D3 interval segment;

The D1 interval segment: the zero start frequency is used as the starting point of the D1 interval segment, and the end point of the new fixed bandwidth frequency interval after the circular shift is used as the end point of the D1 interval segment;

The D2 section: take the end point of the newly-built fixed bandwidth frequency interval after the circular shift as the starting point of the D2 section, and add the product obtained by multiplying the pulse repetition frequency by the number of circular shifts plus one to the original fixed bandwidth starting frequency. The sum of is the end point of the D2 interval;

The D3 interval segment: the sum obtained by multiplying the pulse repetition frequency by the number of circular shifts plus one and the original fixed bandwidth start frequency is the starting point of the D3 interval segment, and the pulse repetition frequency is the end point of the D3 interval segment;

The sub-aperture azimuth spectrum sequence data exists in the D1 interval segment and the D3 interval segment.

Specific examples are as follows,

iPRFAmguty is the number of circular shifts. Specifically, the lowest frequency of the sub-aperture is obtained from the current sub-aperture azimuth shift data, and the quotient of the lowest sub-aperture frequency and the pulse repetition frequency is rounded to obtain the number of circular shifts.

PRF (pulserecurrencefrequency) is the pulse repetition frequency;

After the original preset fixed bandwidth frequency interval [f _{a_start, sub#n} , f _{a_end, sub#n} ] is shifted according to the obtained circular shift times iPRFAmguty, it will be circularly shifted to the new fixed bandwidth frequency interval [f _{a_start, sub#n} +iPRFAmguty*prf, f _{a_end, sub#n} +iPRFAmguty*prf], and the following conditions are met:

f _{a_start, sub#n} +iPRFAmguty*prf<0

f _{a_start, sub#n} +(iPRFAmguty+1)*prf<prf

Divide the intervals from the zero start frequency to the pulse repetition frequency to obtain the D1 interval, D2 interval and D3 interval;

D1 interval segment: take the zero start frequency as the starting point of the D1 interval segment, and take the new bandwidth end point after the circular shift as the end point of the D1 interval segment,

That is: [0, f _{a_end, sub#n} +iPRFAmguty*prf];

D2 interval segment: the new bandwidth end point after the circular shift is taken as the starting point of the D2 interval segment, and the sum obtained by adding the product of the number of circular shifts and the pulse repetition frequency to the original fixed bandwidth starting frequency is the D2 interval segment end,

That is:

[f _{a_end, sub#n} + iPRFAmguty*prf, f _{a_start, sub#n} + (iPRFAmguty+1)*prf];

D3 interval segment: The sum obtained by adding the number of circular shifts plus one to the pulse repetition frequency and the original fixed bandwidth start frequency is the starting point of the D3 interval segment, and the pulse repetition frequency is the end point of the D3 interval segment.

That is: [f _{a_start, sub#n} + (iPRFAmguty+1)*prf, prf];

Obtaining the current sub-aperture azimuth spectrum sequence data exists in the D1 interval segment and the D3 interval segment; [0, f _{a_end, sub#n} + iPRFAmguty*prf]∪[f _{a_start, sub#n} +(iPRFAmguty+1)*prf, prf];

Step S240, using a non-first sub-aperture extraction method to extract valid data information of the next sub-aperture for obtaining imaging data information of the next sub-aperture;

The non-first sub-aperture extraction method is suitable for extracting the non-first sub-aperture in the echo of the whole scene, and it is used on the basis that the first sub-aperture has been determined.

Step S2401, according to the time-frequency relationship of the sub-aperture, obtain the time-frequency characteristics of the effective end target point of the sub-aperture;

In the sub-aperture time-frequency relationship in this embodiment, a certain time point in the time domain corresponds to two target points in the frequency domain, which are the start target point of the time point and the end target point of the time point respectively.

The effective end target point in this embodiment is the end target point at the start time of the sub-aperture.

In this implementation, a straight line passing through the end target point at the start time of the sub-aperture and taking the modulation frequency of the entire scene as the slope is used as the time-frequency characteristic line of the end target point at the start time of the sub-aperture to represent the effective end target of the sub-aperture The time-frequency characteristics of the point;

According to the time-frequency coordinates of the end target point at the start time of the sub-aperture and the modulation frequency of the whole scene, the time-frequency characteristic line of the end target point at the start time of the sub-aperture is obtained, representing the time-frequency characteristic of the effective end target point of the sub-aperture;

The time-frequency coordinates of the effective end target point at the start time of the sub-aperture are: the abscissa is the start time of the sub-aperture, and the highest frequency at the start time of the sub-aperture is the ordinate.

As shown in accompanying drawing 5, the effectively ending target point B of the sub-aperture start moment, the coordinates are (t _{a_start, sub#n} , f _{a_start_max, sub#n} ) The dotted line passing through the target point B is the end of the sub-aperture start moment The time-frequency characteristic line of the target point, and has the modulation frequency f _r , then the time-frequency characteristic line of the end target point at the beginning of the sub-aperture:

f _a -f _{a_start_max, sub#n} = f _r ×(t _a -t _{a_start, sub#n} )

in $f_{a\_\mathrm{start}\_\max ,\mathrm{sub}\#\mathrm{no}}=-\frac{2\&times;V_{\mathrm{vel}}}{\mathrm{\&lambda;}}\&times;\sin (\arctan \left(\frac{t_{a\_\mathrm{start},\mathrm{sub}\#\mathrm{no}}\&times;V_{\mathrm{vel}}}{R_{\mathrm{rot}}}\right)-\frac{{\mathrm{\&theta;}}_a}{2})$

V _vel is the radar equivalent velocity at the reference slant distance, λ is the radar carrier wavelength at the test slant distance, θ _a is the azimuth beam width, t _{a_start, sub#n} is the sub-aperture start time point.

In this embodiment, the modulation frequency is f _r . Those skilled in the art should understand that the modulation frequency f _r can be obtained through the effective information contained in the echo data of the entire scene, which is common knowledge in the field.

In addition, in addition to the end target point at the start time of the sub-aperture, other points existing on the time-frequency characteristic line of the end target point at the start time can be used to obtain the effective time-frequency characteristics of the end target point at the start time of the sub-aperture line, which will not be repeated here.

Step S2402, according to the time-frequency relationship of the sub-aperture, obtain the time-frequency characteristics of the instantaneous lowest frequency of the whole scene;

In this embodiment, the time-frequency characteristic line of the instantaneous minimum frequency of the entire scene is used to represent the time-frequency characteristic of the instantaneous minimum frequency of the entire scene;

The initial target point at the initial moment of the sub-aperture is located on the time-frequency characteristic line of the instantaneous lowest frequency of the entire scene, according to the time-frequency coordinates of the initial target point at the initial moment of the sub-aperture and the change of the Doppler center of the entire scene center rate, obtain the time-frequency characteristic line of the instantaneous minimum frequency of the entire scene, and represent the time-frequency characteristic of the instantaneous minimum frequency of the entire scene;

The time-frequency coordinates of the initial target point at the initial moment of the sub-aperture are as follows: the initial moment of the sub-aperture is taken as the abscissa, and the lowest frequency at the initial moment of the sub-aperture is taken as the ordinate.

As shown in Figure 5, the initial target point A at the beginning of the sub-aperture, the coordinates are (t _{a_start, sub#n} , f _{a_start_min, sub#n} ) The solid line passing through the target point A is the instantaneous minimum frequency of the entire scene On the time-frequency characteristic line, and the rate of change of the Doppler center of the entire scene center is K _rot , the time-frequency characteristic line of the instantaneous minimum frequency of the entire scene is:

f _a -f _{a_start_min, sub#n} =K _rot ×(t _a -t _{a_start, sub#n} )

in, $f_{a\_\mathrm{start}\_\max ,\mathrm{sub}\#\mathrm{no}}=-\frac{2\&times;V_{\mathrm{vel}}}{\mathrm{\&lambda;}}\&times;\sin (\arctan \left(\frac{t_{a\_\mathrm{start},\mathrm{sub}\#\mathrm{no}}\&times;V_{\mathrm{vel}}}{R_{\mathrm{rot}}}\right)-\frac{{\mathrm{\&theta;}}_a}{2})$

V _vel is the radar equivalent velocity at the reference slant distance, λ is the radar carrier wavelength at the test slant distance, θ _a is the azimuth beam width, t _{a_start, sub#n} is the sub-aperture start time point.

In this embodiment, the rate of change of the Doppler center of the entire scene center is K _rot , those skilled in the art should be able to understand that the rate of change of the Doppler center of the entire scene center K _rot can pass through the echoes of the entire scene Access to effective information contained in the data.

Step S2403, according to the time-frequency characteristics of the effective end target point of the sub-aperture and the time-frequency characteristics of the instantaneous lowest frequency of the whole scene, obtain the position of the next sub-aperture in the echo of the whole scene;

Obtain the next sub-aperture end time position according to the time-frequency characteristics of the effective end target point of the sub-aperture and the time-frequency characteristics of the instantaneous lowest frequency of the entire scene;

The intersection of the time-frequency characteristic line of the end target point at the beginning of the sub-aperture and the time-frequency characteristic line of the instantaneous lowest frequency of the entire scene is the next sub-aperture end time point, and the equations are established:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; start</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; sub</span>}<span\; class="notranslate">\; \#</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; start</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; sub</span>}<span\; class="notranslate">\; \#</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; start</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; sub</span>}<span\; class="notranslate">\; \#</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; rot</span>}}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; start</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; sub</span>}<span\; class="notranslate">\; \#</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span>\end{array}\right\}$

Solve the above equation:

${\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; start</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; sub</span>}<span\; class="notranslate">\; \#</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; start</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; sub</span>}<span\; class="notranslate">\; \#</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; rot</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; start</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; sub</span>}<span\; class="notranslate">\; \#</span>\mathrm{<span\; class="notranslate">\; no</span>}}}{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; rot</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}$

t _a is the end time point of the next sub-aperture sub-aperture.

Acquiring the start time point of the next sub-aperture according to the end time point of the next sub-aperture and the time length of the sub-aperture;

Calculate the time range of the next sub-aperture [t _{a_start, sub#n+1} , t _{a_end, sub#n+1} ], where,

t _{a_end, sub#n+1} = t _a

t _{a_start, sub#n+1} = t _{a_end, sub#n+1} -T _sub

T _sub is the sub-aperture time length, and those skilled in the art should understand that the sub-aperture time length T _sub can be obtained from the effective information contained in the echo data of the entire scene, which is common knowledge in the art.

According to the start time point t _{a_start of the next sub-aperture, sub#n+1} and the end time point t _{a_end, sub#n+1} of the next sub-aperture, obtain the echo of the next sub-aperture in the whole scene Location.

Step S2404, according to the position of the next sub-aperture in the echo of the entire scene, extract valid data information of the next sub-aperture from the echo data of the entire scene.

Step S250, extracting the next sub-aperture azimuth spectrum shift data from the next sub-aperture imaging data information;

Step S260, using a circular shift algorithm to split the azimuth spectrum shift data of the next sub-aperture to obtain the azimuth sequence data of the next sub-aperture for splicing with the sub-aperture.

Those skilled in the art should be able to understand the effective information of the above-mentioned current sub-aperture echo data, including ephemeris parameters, SAR (Synthetic Aperture Radar) characteristic parameters and orthogonal sampling data of the current sub-aperture.

The effective information contained in the echo data of the whole scene includes ephemeris parameters, SAR (Synthetic Aperture Radar) characteristic parameters and orthogonal sampling data of the whole scene.

The ephemeris parameters include on-board time, satellite position and velocity, satellite attitude (pitch angle, roll angle, yaw angle) and so on.

SAR (Synthetic Aperture Radar) characteristic parameters include wavelength, range bandwidth, range sampling frequency, pulse width, pulse repetition frequency, range beam center viewing angle, range beam width, azimuth deployment width, azimuth start/end scan Angle, beam width in azimuth, initial sampling time, number of sampling points in range, etc.

third embodiment

The present invention also provides a system of a SAR sub-aperture splicing system. FIG. 6 is a system block diagram of a SAR sub-aperture splicing system. The embodiment will be described below with reference to the accompanying drawing 6. This system mainly includes mobile Bit data unit 61, sequential data unit 62, next imaging data unit 63, next shift data unit 64 and next sequential data unit 65, wherein,

Shift data sheet 61: it is used to extract sub-aperture azimuth spectrum shift data from sub-aperture imaging data information;

Sequential data unit 62: it uses a circular shift algorithm to split the sub-aperture azimuth spectrum shift data, and is used to obtain sub-aperture azimuth sequential data;

The next imaging data unit 63: it uses a non-first sub-aperture extraction method to extract the effective data information of the next sub-aperture for obtaining the imaging data information of the next sub-aperture;

The next shift data unit 64: it is used to extract the next sub-aperture azimuth direction spectrum shift data in the next sub-aperture imaging data information;

Next sequential data unit 65: it uses a circular shift algorithm to split the azimuth spectrum shift data of the next sub-aperture to obtain the next sub-aperture azimuth sequential data sequence for splicing with the sub-aperture.

Those skilled in the art can understand that the accompanying drawing is only a schematic diagram of an embodiment, and the modules or processes in the accompanying drawing are not necessarily necessary for implementing the present invention.

It can be seen from the above description of the implementation manners that those skilled in the art can clearly understand that the present invention can be implemented by means of software plus a necessary general hardware platform. Based on this understanding, the essence of the technical solution of the present invention or the part that contributes to the prior art can be embodied in the form of software products, and the computer software products can be stored in storage media, such as ROM/RAM, disk , CD, etc., including several instructions to make a computer device (which may be a personal computer, server, or network device, etc.) execute the methods described in various embodiments or some parts of the embodiments of the present invention.

Each embodiment in this specification is described in a progressive manner, the same and similar parts of each embodiment can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device or system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and for relevant parts, refer to part of the description of the method embodiments. The device and system embodiments described above are only illustrative, and the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, It can be located in one place, or it can be distributed to multiple network elements. Part or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. It can be understood and implemented by those skilled in the art without creative effort.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present invention can easily think of changes or Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (8)

1. A sub-aperture splicing method of SAR, characterized in that, comprising, extracting the sub-aperture azimuth direction spectrum shift data from the imaging data information of the sub-aperture; Use the circular shift algorithm to split the sub-aperture azimuth spectrum shift data to obtain sub-aperture azimuth sequence data; Using a non-first sub-aperture extraction method to extract effective data information of the next sub-aperture for obtaining imaging data information of the next sub-aperture; Extracting the next sub-aperture azimuth spectrum shift data from the next sub-aperture imaging data information; A circular shift algorithm is used to split the azimuth spectrum shift data of the next sub-aperture to obtain the azimuth sequence data of the next sub-aperture for splicing with the sub-aperture. 2. the sub-aperture splicing method of a kind of SAR as claimed in claim 1, is characterized in that, described employing circular shift algorithm to split current sub-aperture azimuth direction spectrum shift data, comprising: Calculate the number of circular shifts according to the spectrum range and pulse repetition frequency of the sub-aperture azimuth shift data; After the start frequency and stop frequency of the original fixed bandwidth are shifted according to the number of circular shifts obtained, the start frequency and stop frequency of the new fixed bandwidth are obtained correspondingly; According to the preset conditions and the obtained start frequency and stop frequency of the newly-built fixed bandwidth, the sub-aperture azimuth spectrum order data is obtained within the frequency range with the start point being zero and the end point being the pulse repetition frequency. 3. the sub-aperture splicing method of a kind of SAR as claimed in claim 2, is characterized in that, also comprises: The sub-aperture minimum frequency is obtained from the current sub-aperture azimuth shift data, and the number of circular shifts is obtained by rounding the quotient of the sub-aperture minimum frequency and the pulse repetition frequency. 4. the sub-aperture splicing method of a kind of SAR as claimed in claim 2, is characterized in that, described acquisition starts frequency and stop frequency of newly-built fixed bandwidth, comprises: The sum of the product obtained by multiplying the number of circular shifts by the pulse repetition frequency and the initial frequency of the original fixed bandwidth is added to obtain the initial frequency of the new fixed bandwidth after the circular shift; The sum of the product obtained by multiplying the number of circular shifts by the pulse repetition frequency and the stop frequency of the original fixed bandwidth is obtained to obtain the stop frequency of the new fixed bandwidth after the circular shift. 5. the sub-aperture splicing method of a kind of SAR as claimed in claim 2 is characterized in that, described preset condition comprises: The new bandwidth starting point after the circular shift is greater than zero, and, The sum of the product obtained by multiplying the number of circular shifts by one and the pulse repetition frequency and the initial frequency of the original fixed bandwidth is less than the pulse repetition frequency. 6. the sub-aperture splicing method of a kind of SAR as claimed in claim 1, is characterized in that, described adopting non-first sub-aperture extracting method to extract next sub-aperture effective data information, comprises: According to the time-frequency relationship of the sub-aperture, the time-frequency characteristics of the effective end target point of the sub-aperture are obtained; According to the time-frequency relationship of the sub-aperture, the time-frequency characteristics of the instantaneous lowest frequency of the entire scene are obtained; Acquiring the position of the next sub-aperture in the echo of the entire scene according to the time-frequency characteristic of the effective end target point of the sub-aperture and the time-frequency characteristic of the instantaneous lowest frequency of the entire scene; According to the position of the next sub-aperture in the echo of the whole scene, effective data information of the next sub-aperture is extracted from the echo data of the whole scene. 7. The sub-aperture splicing method of a kind of SAR as claimed in claim 6, is characterized in that, described according to the time-frequency characteristic of effectively ending target point of described sub-aperture and the time-frequency characteristic of the instantaneous lowest frequency of described whole scene, Get the position of the next sub-aperture in the echo of the whole scene, including: Acquiring the next sub-aperture end time point according to the time-frequency characteristic of the effective end target point of the sub-aperture and the time-frequency characteristic of the instantaneous lowest frequency of the whole scene; Acquiring the start time point of the next sub-aperture according to the end time point of the next sub-aperture and the time length of the sub-aperture; According to the start time point of the next sub-aperture and the end time point of the next sub-aperture, the position of the next sub-aperture in the echo of the whole scene is obtained. 8. A sub-aperture splicing system for SAR, characterized in that it comprises: Shift data unit: it is used to extract the sub-aperture azimuth direction spectrum shift data from the imaging data information of the sub-aperture; Sequential data unit: it uses a circular shift algorithm to split the sub-aperture azimuth spectrum shift data to obtain sub-aperture azimuth sequential data; The next imaging data unit: it uses the non-first sub-aperture extraction method to extract the effective data information of the next sub-aperture, and is used to obtain the imaging data information of the next sub-aperture; The next shift data unit: it is used to extract the next sub-aperture azimuth spectrum shift data in the next sub-aperture imaging data information; Next sequential data unit: it uses a circular shift algorithm to split the next sub-aperture azimuth spectrum shift data to obtain the next sub-aperture azimuth sequential data sequence for splicing with the sub-aperture.