CN110045375B - Method and system for processing one-bit SAR echo data - Google Patents
Method and system for processing one-bit SAR echo data Download PDFInfo
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Abstract
The invention provides a method and a system for processing one-bit SAR echo data, which are characterized in that a one-bit quantized echo data sequence is obtained by carrying out one-bit quantization on received SAR echo data; according to the preset shift value, each data value in the echo data sequence after one-bit quantization is respectively subjected to convolution operation with the data value in the matched filter sequence to obtain the SAR echo data sequence after convolution operation, the calculation amount and complexity of convolution operation are reduced, the cost of an SAR system is reduced, the operation speed and efficiency of the system are improved, and the imaging quality of the SAR image after matched filtering is ensured at the same time, so that the SAR echo data sequence has better real-time performance and higher performance power consumption ratio in data processing.
Description
Technical Field
The invention relates to the technical field of signal processing, in particular to a method and a system for processing one-bit SAR echo data.
Background
SAR (Synthetic Aperture Radar) imaging has the detection capability of all-time, all-weather, long-acting distance and high resolution, plays an important role in a plurality of fields such as remote sensing mapping, area detection, geological exploration, disaster relief and the like, and is a research hotspot of scholars at home and abroad. However, as the bandwidth of the SAR signal increases, the burden of data acquisition, storage, transmission and processing is gradually increased. On one hand, the SAR system needs to perform high-precision sampling on echo data to keep complete signal characteristics, so that the data processing bit width is increased, and higher requirements are put forward on the hardware performance of the system; on the other hand, the signal sampling rate also needs to be increased accordingly to avoid aliasing of the signal spectrum, so that the data amount is increased, and the efficiency of data processing is reduced. One-bit sampling can reduce the data bit width, but in order to improve the imaging quality of one-bit data, the sampling rate needs to be improved, so that an efficient and high-precision one-bit SAR echo data processing method needs to be researched.
The one-bit SAR echo data processing methods disclosed in the prior art are respectively as follows:
in the first method, the echo signals are subjected to one-bit quantization, so that the data volume of imaging processing is greatly reduced, and the complexity of imaging processing is greatly simplified. However, in this method, one-bit quantization is to compare the echo data with 0, which may cause loss of signal amplitude information and affect imaging quality.
In the second method, a random time-varying threshold is introduced into one bit of samples, so that high-quality recovery of the absolute amplitude information of the original signal can be realized, and the integrity of the information when the one bit signal is reconstructed is ensured. However, the method is established on the premise that the original signal has the sparse characteristic, and is difficult to apply in the non-sparse scene of SAR imaging.
In the third method, a Gaussian time-varying threshold is used for carrying out one-bit quantization on the deception interference, so that an effective false target imaging result can be obtained in SAR imaging processing, but the Gaussian time-varying threshold introduces noise-like interference in the imaging result, and the imaging quality is reduced.
In the fourth method, the imaging performance is improved by a sampling rate more than four times of the bandwidth during one-bit sampling, but the problem that the imaging is influenced by accompanying higher harmonics is not solved.
Therefore, the presently disclosed SAR echo signal processing method cannot meet the requirements of high efficiency and high precision, and the prior art still needs to be improved and developed.
Disclosure of Invention
In view of the defects of the prior art, the present invention aims to provide a method and a system for processing one-bit SAR echo data, which aim to solve the defects that in the prior art, when one-bit SAR data is processed, the imaging quality cannot be guaranteed while the operation cannot be simplified, and efficient and high-precision processing of the echo data cannot be achieved.
The technical scheme of the invention is as follows:
the invention provides a method for processing one-bit SAR echo data, which comprises the following steps:
A. carrying out one-bit quantization on the received SAR echo data to obtain an echo data sequence after one-bit quantization;
B. performing convolution operation on each data value in the echo data sequence after one-bit quantization and a data value in a preset matched filter sequence according to a preset shift number to obtain an SAR echo data sequence after the convolution operation; the preset shift number is greater than 1;
and C, repeating the step A and the step B within the pulse continuous emission time to obtain the SAR echo data after matched filtering.
Optionally, step B includes:
b1, dividing the data value of the matched filter sequence into a sign bit and a data bit;
b2, performing XOR operation on data values in the first echo data sequence after one-bit quantization and the sign bit respectively every shift number, and splicing and combining the new sign bit obtained by the operation and the corresponding data bit to obtain a second echo data sequence;
and B3, performing summation operation on each element in the second echo data sequence to obtain the SAR echo data sequence after matching and filtering.
Optionally, step a further includes:
a01, transmitting a chirp signal to a detected target by utilizing SAR;
a02, the SAR receiver receives the echo signal reflected by the detected target and generates a single-frequency time-varying threshold;
and A03, carrying out one-bit quantization on the SAR echo signal by using the single-frequency time-varying threshold value to obtain a quantized echo data sequence.
Optionally, the data in the acquired data sequence contains a real part and an imaginary part; the data bits have real and imaginary parts;
the step B2 further includes:
and performing convolution operation on the real part and the imaginary part of the sampled data in the acquired data sequence and the real part and the imaginary part of the data bit respectively.
Optionally, the step a02 further includes:
a021, sampling the received echo signal at a preset sampling frequency; wherein the preset sampling frequency is greater than four times of the bandwidth of the echo signal.
Optionally, the step a02 further includes:
a022, SAR receive and generate a single frequency time varying threshold using a local oscillator or a direct digital frequency synthesizer.
Optionally, the step a03 further includes:
and A031, comparing a vector s corresponding to each element in the echo signal with a vector h represented by the single-frequency time-varying threshold, if s is less than h, storing the echo data as 0, and if s is more than or equal to h, storing the echo data as 1.
The invention also provides a processing system of the one-bit SAR echo data, which comprises the following steps: an SAR receiver;
the SAR receiver includes: the device comprises a data sequence generation module, a matched filtering module and a pulse compression data generation module;
the data sequence generating module is used for carrying out one-bit quantization on the received SAR echo data to obtain an echo data sequence after one-bit quantization;
the matched filtering module is used for performing convolution operation on each data value in the echo data sequence after one-bit quantization and a data value in a preset matched filter sequence according to a preset shift number to obtain an SAR echo data sequence after the convolution operation; the preset shift number is greater than 1;
and the pulse compression data generation module is used for repeating the step A and the step B within the pulse continuous emission time to obtain the SAR echo data after the matched filtering.
Optionally, the matched filtering module includes:
a value dividing unit for dividing the data value of the matched filter sequence into a sign bit of one bit and a data bit of a long bit width;
the XOR operation unit is used for carrying out XOR operation on data values in the first echo data sequence after one-bit quantization and the sign bit respectively every shift number, and splicing and combining the new sign bit obtained by operation and the corresponding data bit to obtain a second echo data sequence;
and the summation operation unit is used for carrying out summation operation on each element in the second echo data sequence to obtain the SAR echo data sequence after matching and filtering.
Optionally, the method further includes: the SAR receiver is arranged on the SAR platform;
and the SAR is used for repeatedly transmitting the linear frequency modulation pulse signal to the detected target according to the preset pulse transmission interval.
The invention provides a method and a system for processing one-bit SAR echo data, which are characterized in that when the echo data is subjected to matched filtering, an adopted sequence participating in convolution operation is extracted, so that the calculation amount and the complexity of the convolution operation are reduced, the cost of an SAR system is reduced, the operation speed and the efficiency of the system are improved, and the imaging quality of an SAR image after matched filtering is ensured, so that the method and the system have better real-time performance and higher performance power consumption ratio in data processing.
Drawings
FIG. 1 is a flow chart of a preferred embodiment of a method for processing one-bit SAR echo data according to the present invention;
FIG. 2 is a schematic diagram illustrating the principle of XOR operation in the method of the present invention;
FIG. 3 is a schematic diagram of a hardware implementation of 16bit by 1bit XOR operation;
FIG. 4 is a functional block diagram of a preferred embodiment of a one-bit SAR echo data processing system according to the present invention;
FIG. 5 is a diagram of a one-bit echo before convolution sampling with a matched filter;
fig. 6 shows a one-bit echo after convolution sampling with a matched filter.
Detailed Description
In order to make the objects, technical solutions and effects of the present invention clearer and clearer, the present invention is described in further detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention provides a method for processing one-bit SAR echo data, as shown in figure 1, comprising the following steps:
and step S1, carrying out one-bit quantization on the received SAR echo data to obtain an echo data sequence after one-bit quantization.
Sampling the echo data sequence after one-bit quantization, and sequentially extracting echo data from the echo data sequence after one-bit quantization according to a preset sampling interval. The preset sampling interval is a natural number greater than 1, and preferably, the preset sampling interval can be set to 4 data intervals, so that the filtering effect of the matched filter is ensured while the data volume contained in the echo data sequence is simplified.
In order to acquire a one-bit quantized echo data sequence, before this step, the method further includes the following steps:
s01, transmitting a chirp signal to a detected target by utilizing the SAR;
s02, the SAR receiver receives the echo signal reflected by the detected target and generates a single-frequency time-varying threshold;
and S03, carrying out one-bit quantization on the SAR echo signal by using the single-frequency time-varying threshold to obtain a quantized echo data sequence.
Synthetic Aperture Radar (SAR) uses an antenna to move at a constant speed along the track of a long linear array and radiate coherent signals, and performs coherent processing on echoes received at different positions, thereby obtaining an imaging Radar with higher resolution. And the SAR transmits a chirp signal to the detected target according to a preset pulse transmission interval.
And after the detected target receives the chirp signal, reflecting an echo signal, receiving the echo signal by an SAR receiver arranged on an SAR platform, and carrying out one-bit quantization on the echo signal. The SAR platform may be mounted on an airplane, a satellite or an automobile.
In order to reduce the influence of frequency spectrum aliasing, sampling the received echo signal at a preset sampling frequency; wherein the preset sampling frequency is greater than four times of the bandwidth of the echo signal.
Optionally, the step S02 further includes:
s022, SAR receives and generates a single frequency time varying threshold using a local oscillator or a direct digital frequency synthesizer.
Optionally, the step S03 further includes:
and S031, comparing the vector S corresponding to each element in the echo signal with the vector h represented by the single-frequency time-varying threshold, if S is less than h, storing the echo data as 0, and if S is more than or equal to h, storing the echo data as 1.
Specifically, the step of performing one-bit quantization on the echo signal is as follows:
1. let trThe time of day transmitting signal is s0(tr) The time from the transmission of the signal to the reception of the echo is t, and the received echo is s (t)r). At a sampling rate FsSampling the received signal to obtain an echo signal sample sequence, which can be expressed as an mx 1 vector s, i.e. [ s ]1,s2,…,sm,…,sM]Wherein M is more than or equal to 1 and less than or equal to M.
2. The SAR receiver generates the signal at the frequency f by means of a local oscillator or a Direct Digital Synthesizer (DDS)0Single frequency time varying threshold hs(tr) Likewise with FsSampling a single-frequency time-varying threshold, the threshold can be expressed as an M × 1 vector h, i.e., [ h ]1,h2,…,hm,…,hM]Wherein M is more than or equal to 1 and less than or equal to M.
3. Quantizing the echo signal by one bit, comparing the corresponding elements of the vector s and h in sequence, taking the m-th element as an example, if sm≥hmStoring the echo data as 1; if sm＜hmThe echo data is stored as 0. A one-bit quantized echo data sequence consisting of 0 and 1 can thus be obtained.
Step S2, according to a preset shift number, carrying out convolution operation on each data value in the echo data sequence after one-bit quantization and the data value in the matched filter sequence respectively to obtain an SAR echo data sequence after convolution operation; the preset shift number is greater than 1.
The echo data sequence quantized by one bit in the above step S1 is convolved with the matched filter sequence.
Specifically, the convolution operation is not a convolution sum obtained by directly multiplying the data value in the sampled sampling data sequence and the data value in the matched filter sequence and then adding the products, but an exclusive-or operation is used for replacing the multiplication operation in the original convolution operation, so that the purpose of reducing the operation amount is achieved.
The matched filter realizes two functions, namely pulse compression, namely the filter is matched with an echo, and down sampling of an output echo signal is realized.
Further, to achieve echo matching, the filter response function should be the complex conjugate of the baseband signal, which is translated to the frequency domain as:
wherein Tr is the SAR signal pulse width, and gamma is the modulation frequency. Based on the formula, the echo signal is filtered based on the rectangular window function rect [ ], and in addition, the exponential function part displays that the phase-frequency characteristic of the filter is opposite to that of the baseband signal, so that the phase of the signal after passing through the filter is ensured to be 0, and the matching effect is achieved.
On the other hand, in order to realize the down-sampling of the echo signal, the step adopts the shift operation of the calculated data value, namely, the convolution calculation is carried out once at intervals of the preset shift number, thereby reducing the operation amount. According to the Noble identity principle, the effect obtained by performing matched filtering at intervals of a plurality of points is the same as the effect obtained by performing matched filtering at first and performing extraction or interpolation. Therefore, the operation amount of convolution operation can be reduced by performing shift operation first in the step to obtain a matched filtering method.
Specifically, the convolution operation performed on the sampled sample data sequence and the matched filter sequence in step S2 includes:
and S21, dividing the data value of the matched filter sequence into a sign bit with one bit and a data bit with a long bit width.
And S22, performing XOR operation on the data values in the first echo data sequence after one-bit quantization and the sign bit respectively every shift number, and splicing and combining the new sign bit obtained by the operation and the corresponding data bit to obtain a second echo data sequence.
And S23, performing summation operation on each element in the second echo data sequence to obtain the SAR echo data sequence after matching and filtering.
As shown in fig. 2, in the above steps, first, the sign bit and the data bit of the data value in the matched filter sequence are extracted, the extracted sign bit is used as an input of the xor operation, and the first echo data sequence after one-bit quantization is used as another input. After the exclusive-or operation, we output the result as a sign bit, which is then combined with the data bits of the matched filter. The final output result of this operation is consistent with conventional multiplication operations.
As shown in fig. 3, which is a hardware diagram of the xor operation, the xor operation is implemented by a 2-input xor gate, and the sign bit of the matched filter sequence and the first echo data sequence quantized by one bit are respectively used as another input, and then the output result is combined with the data bit of the matched filter.
In the convolution operation in step S22, since the data in the acquired data sequence contains a real part and an imaginary part; the data bits have real and imaginary parts; the specific convolution operations thus include:
and performing convolution operation on the real part and the imaginary part of the sampled data in the acquired data sequence and the real part and the imaginary part of the data bit respectively.
Besides convolution operation between the real part and convolution operation between the imaginary part and the imaginary part, the method also comprises the following steps: convolution operation between the real part and convolution. Assuming that the 1-bit echo sequence is (a + Bj) and the MF matched filter sequence is (C + Dj), the convolution value between the real part and the real part in the convolution operation result is:
A+Bj*C+Dj＝A*C-B*D+A*D+B*Cj
the convolution operation also comprises a shift operation, namely before the convolution operation, after one sequence of the two sequence data is subjected to the turnover operation, when the convolution operation is carried out, according to the set shift bit, the data value of the corresponding position is sequentially extracted from the first echo data sequence quantized by one bit, and the extracted data value is added into the convolution operation, so that the operation amount is reduced.
For example: and selecting the number of the sampling shift as N, and after the convolution value of the mth data value is obtained, shifting the convolution value of the (m + N) th element by changing the traditional 1-unit shifting in the convolution shift operation into N units during shifting. After traversing the whole sequence, the obtained convolution sequence is the sampling result of the traditional convolution, and the frequency (sequence length) after down-sampling is 1/N before extraction. Among them, N is preferably 4.
And step S3, repeating the step A and the step B in the repetition interval of pulse transmission to obtain the SAR echo data after matched filtering.
And repeating the steps S1-S2 within different pulse transmission repetition intervals, and sequentially storing the one-bit SAR echo data sequence after matched filtering until the SAR imaging process is finished. Therefore, one-bit SAR echo data required by SAR imaging can be obtained, and a focused imaging result can be obtained by imaging the data by using an imaging algorithm.
The invention utilizes the characteristic of SAR echo signals quantized by one bit, replaces multiplication operation with an exclusive OR logic gate in the convolution calculation in the process of calculating SAR imaging matched filtering, adopts shift operation to extract before calculation of convolution, greatly reduces the subsequent processing complexity of one-bit SAR data, reduces the cost of an SAR system, improves the operation speed and the operation efficiency of the system, achieves better real-time performance and higher performance power consumption ratio, and is a more economic and effective realization method.
The convolution operation method in the method of the present invention will be described in more detail below.
Suppose the input signal isIQ two paths of complex signals, namely an echo data sequence x (n) after one-bit quantization, a preset matched filter sequence h (n) and a sampling frequency FsThe bandwidth is 6 times, if the frequency of the data is reduced to 1.5 times, the purpose of extraction before calculation is achieved by shifting 4 units after the sign bit exclusive or logic operation is finished each time.
Assuming that the length of x (n) is 10 and the length of h (n) is 5, the arrangement of the starting sequences is shown as follows:
in the above table, y (n) is the convolution of the one-bit quantized echo data sequence x (n) and the preset matched filter sequence h (n).
The convolution is calculated as follows:
the first step is as follows: one of the data trains is turned over, preferably, a data sequence with a short length in two columns of data is turned over, which is expressed as follows:
the second step is that: and performing exclusive-or operation on the corresponding first data element in the two data sequences, adding the exclusive-or operation results to obtain a data value 0 after performing convolution operation on the first corresponding data element, and recording the data value as: y (0), which is represented as follows:
the third step: shifting h (n), shifting 4 units, calculating convolution of the second corresponding data element after the shifting operation, and recording the data value after the convolution operation of the second corresponding element as y (1), which is expressed as follows:
and fourthly, repeating the third step, carrying out shift operation on h (n), and recording the data values after convolution operation of the three corresponding elements as y (2) after calculating the shift operation.
And fifthly, repeating the convolution, and recording the data value after the convolution operation of the fourth corresponding element as: y (4).
And repeating the operation to sequentially obtain convolution values between each data element in the x (n) sequence and each data element in the h (n) sequence, thereby obtaining the convolution of the whole echo data sequence x (n) after one bit quantization and the preset matched filter sequence h (n).
The present invention also provides a processing system for one-bit SAR echo data, as shown in fig. 4, including: an SAR receiver;
the SAR receiver includes: a data sequence generation module 100, a matched filtering module 200 and a pulse compression data generation module 300;
the data sequence generating module 100 is configured to perform one-bit quantization on the received SAR echo data to obtain a one-bit quantized echo data sequence; the function of which is as described in step S1.
The matched filtering module 200 is configured to perform convolution operation on each data value in the echo data sequence after one-bit quantization and a data value in a preset matched filter sequence according to a preset shift number, so as to obtain an SAR echo data sequence after convolution operation; the preset shift number is greater than 1; the function of which is as described in step S2.
The pulse compressed data generating module 300 is configured to obtain, within a pulse transmission time, matched filtered SAR echo data composed of multiple sets of SAR echo data sequences, where the function of the module is as described in step S3.
Further, the matched filtering module 200 includes:
a value dividing unit for dividing the data value of the matched filter sequence into a sign bit of one bit and a data bit of a long bit width;
and the convolution operation unit is used for carrying out XOR logical operation on the sampled acquisition data sequence and the coincidence bit, and splicing and combining an operation result obtained by the XOR logical operation and the data bit again to obtain a convolution operation result.
In order to acquire the echo signal reflected by the detected target, the method further comprises the following steps: a SAR on which the SAR receiver is disposed;
and the SAR is used for repeatedly transmitting the linear frequency modulation pulse signal to the detected target according to the preset pulse transmission interval.
Compared with the SAR echo signal processing method in the prior art, the method and the system have the following advantages that:
(1) in the aspect of data acquisition, one-bit quantization is carried out on echo signals.
If the data is to be quantized with 16 bits, the complexity and cost of the analog-to-digital converter (ADC) is much higher than the complexity and cost of quantizing it to 1 bit. Meanwhile, due to the lower complexity and cost of 1bit, the sampling rate of the method can be much higher than that of 16 bits, which is an advantage in data acquisition.
(2) In the convolution operation of matched filtering, exclusive-or operation is referred to instead of multiplication operation.
Echo data needs to be subjected to matched filtering in SAR imaging, a large amount of multiplication and addition operation is usually required to be carried out on the echo data, and the numerical value storage of an SAR system is carried out in a binary mode. Taking 3 × 3 as an example (4-bit acquired data × 4-bit matched filter), the binary calculation formula to be performed is 4b0011 × 4b0011 — 8b0000 — 1001. The method of the invention reduces the collected data to 1bit and only 0 or 1, so that the collected data is 1b0 multiplied by 4b0011(1bit collected data multiplied by 4bit matched filter), the specific calculation method is that the logic operation (XOR, XOR logic) is carried out on the 1bit data 0 and the highest bit (sign bit) 0 in the 4b0011, then the results are spliced, the obtained result is reduced compared with the previous bit width, the single bit data multiplication operation is carried out by utilizing the XOR, and the hardware complexity and the cost are reduced.
(3) In the convolution sampling process, a shift operation is employed.
The length of the acquired data is set to be m, the length of the matched filter is set to be l, and l is less than m. And folding one signal, and then performing multiplication and addition operation on the folded signal and the other signal to obtain a convolution signal result with the length of m + l-1, the multiplication operation amount of l (m + l-1) and the addition operation amount of (l-1) (m + l-1). If the final length is as follows before calculation by the method of pre-sampling shift
The multiplication amount is
The addition amount is
The data volume is reduced, the calculation speed is improved, the problem of data volume increase caused by high oversampling rate is avoided, and meanwhile, the quality of the matched filter is ensured.
The effect of the present invention can be further illustrated by the following simulation experiment, wherein MATLAB software is adopted for simulation during simulation.
The parameters of the simulation data are as follows: fig. 5 shows the result of SAR imaging of conventional high-precision sampling, and fig. 6 shows the result of one-bit quantization of echo data based on a single-frequency time-varying threshold and then imaging with one-bit data. Since one-bit quantization reduces data accuracy, fig. 6 has a certain amount of noise compared to fig. 5, but objects such as buildings, roads, vehicles, etc. in the scene can still be resolved.
The invention provides a method and a system for processing one-bit SAR echo data, which are characterized in that a one-bit quantized echo data sequence is obtained by carrying out one-bit quantization on received SAR echo data; according to the preset shift value, each data value in the echo data sequence after one-bit quantization is respectively subjected to convolution operation with the data value in the matched filter sequence to obtain the SAR echo data sequence after convolution operation, the calculation amount and complexity of convolution operation are reduced, the cost of an SAR system is reduced, the operation speed and efficiency of the system are improved, and the imaging quality of the SAR image after matched filtering is ensured at the same time, so that the SAR echo data sequence has better real-time performance and higher performance power consumption ratio in data processing.
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 (6)
1. A method for processing one-bit SAR echo data is characterized by comprising the following steps:
A. carrying out one-bit quantization on the received SAR echo data to obtain an echo data sequence after one-bit quantization;
B. performing convolution operation on each data value in the echo data sequence after one-bit quantization and a data value in a preset matched filter sequence according to a preset shift number to obtain an SAR echo data sequence after the convolution operation; the preset shift number is greater than 1;
c, repeating the step A and the step B within the pulse continuous emission time to obtain SAR echo data after matched filtering;
the step A further comprises the following steps:
a01, transmitting a chirp signal to a detected target by utilizing SAR;
a02, the SAR receiver receives echo data reflected by the detected target and generates a single-frequency time-varying threshold;
a03, carrying out one-bit quantization on SAR echo data by utilizing the single-frequency time-varying threshold to obtain a quantized echo data sequence;
the step B comprises the following steps:
b1, dividing the data value of the matched filter sequence into a sign bit and a data bit;
b2, performing XOR operation on data values in the first echo data sequence after one-bit quantization and the sign bit respectively every preset shift number, and splicing and combining the new sign bit obtained by the operation and the corresponding data bit to obtain a second echo data sequence;
b3, summing each element in the second echo data sequence to obtain a matched and filtered SAR echo data sequence;
the step B2 further includes: taking the extracted sign bit as an input of exclusive-or operation, and taking a first echo data sequence with one bit quantized as another input; after the exclusive-or operation, the output result is taken as a sign bit and then combined with the data bit of the matched filter;
the corresponding function of the filter is complex conjugate of a baseband signal, so that the phase of the signal is 0 after the signal passes through the filter, and the matching of the filter and an echo is realized; the matched filter carries out a convolution calculation by carrying out shift operation on the calculated data value, namely, carrying out a preset shift number interval, thereby realizing the down-sampling of the output echo data.
2. The method for processing SAR echo data according to claim 1, wherein the data in the first echo data sequence has a real part and an imaginary part; the data bits have real and imaginary parts;
the step B2 further includes:
and performing convolution operation on the real part and the imaginary part of the sampled data in the first echo data sequence and the real part and the imaginary part of the data bit respectively.
3. The method for processing SAR echo data according to claim 1, wherein the step a02 further comprises:
a021, sampling received echo data at a preset sampling frequency; wherein the preset sampling frequency is greater than four times of the bandwidth of the echo data.
4. The method for processing SAR echo data according to claim 1, wherein the step a02 further comprises:
a022, SAR receive and generate a single frequency time varying threshold using a local oscillator or a direct digital frequency synthesizer.
5. The method for processing SAR echo data according to claim 4, wherein the step a03 further comprises:
and A031, comparing a vector s corresponding to each element in the echo data with a vector h represented by the single-frequency time-varying threshold, if s is less than h, storing the echo data as 0, and if s is more than or equal to h, storing the echo data as 1.
6. A system for processing one-bit SAR echo data, comprising: an SAR receiver;
the SAR emission device is used for repeatedly emitting linear frequency modulation pulse signals to the detected target according to preset pulse emission intervals;
the SAR receiver includes: the device comprises a data sequence generation module, a matched filtering module and a pulse compression data generation module;
the data sequence generating module is used for carrying out one-bit quantization on the received SAR echo data to obtain an echo data sequence after one-bit quantization;
the matched filtering module is used for performing convolution operation on each data value in the echo data sequence after one-bit quantization and a data value in a preset matched filter sequence according to a preset shift number to obtain an SAR echo data sequence after the convolution operation; the preset shift number is greater than 1;
the pulse compression data generation module is used for obtaining SAR echo data after matched filtering within the pulse continuous emission time;
the matched filtering module includes:
a value dividing unit for dividing the data value of the matched filter sequence into a sign bit of one bit and a data bit of a long bit width;
the XOR operation unit is used for carrying out XOR operation on data values in the first echo data sequence after one-bit quantization and the sign bit respectively every preset shift number, and splicing and combining the new sign bit obtained by operation and the corresponding data bit to obtain a second echo data sequence;
the summation operation unit is used for carrying out summation operation on each element in the second echo data sequence to obtain the SAR echo data sequence after matched filtering;
the exclusive-or operation unit is further used for taking the extracted sign bit as an input of exclusive-or operation and taking the first echo data sequence after one-bit quantization as another input; after the exclusive-or operation, the output result is taken as a sign bit and then combined with the data bit of the matched filter;
the corresponding function of the filter is complex conjugate of a baseband signal, so that the phase of the signal is 0 after the signal passes through the filter, and the matching of the filter and an echo is realized; the matched filter carries out a convolution calculation by carrying out shift operation on the calculated data value, namely, carrying out a preset shift number interval, thereby realizing the down-sampling of the output echo data.
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