CN113567939B - Predistortion compensation method, module and receiving and transmitting system of synthetic aperture radar system - Google Patents
Predistortion compensation method, module and receiving and transmitting system of synthetic aperture radar system Download PDFInfo
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Abstract
The invention discloses a predistortion compensation method, a module and a system of a synthetic aperture radar system, wherein the method comprises the following steps: storing and extracting effective signal data in closed-loop data, and opening up a storage space by taking the pulse number as a row to store the effective signal data; decomposing the amplitude of the effective signal data pulse by taking the solution of the Legendre function as an orthogonal basis to obtain the amplitude and the amplitude error of each order; decomposing the phases of the effective signal data pulses by taking the solution of the Legendre function as an orthogonal basis to obtain phases and phase errors of each order; integrating the amplitude error and the phase error to obtain a system amplitude-phase function; when judging that the front and back data rates of the system are matched, inverting the amplitude-phase function to obtain a predistortion compensation function; and the radar signal source reads the predistortion compensation function to generate a radar signal. The method can realize the extraction and compensation of errors with different orders, reduces the complexity of hardware realization, and is suitable for engineering realization.
Description
Technical Field
The invention belongs to the field of radars, and particularly relates to a predistortion compensation method, a predistortion compensation module and a predistortion receiving and transmitting system of a synthetic aperture radar system.
Background
The Synthetic Aperture (SAR) radar is a two-dimensional microwave imaging radar, and an apparatus for actively transmitting and receiving electromagnetic waves can be carried on different carriers such as satellites, planes, trains, automobiles and the like to realize earth observation, and has the advantages of all-weather, strong penetrating capacity and the like. The method has irreplaceable advantages in military aspects such as disaster detection, environment monitoring, resource exploration, mapping, target identification and tracking, the range-wise resolution of the SAR radar depends on the bandwidth of radar signals, the azimuth-wise resolution depends on synthetic aperture time, and therefore, the premise of high resolution for the SAR radar is that the linearity of transmitted Linear Frequency Modulation (LFM) electromagnetic signals is not distorted. In practical radar systems, the frequency converter, the mixer, the fixed emission and the like are indispensable components, and the devices internally contain transistors, and the characteristics of the transistors are nonlinear, so that signal distortion is necessarily caused. The LFM signals sent by the SAR radar are all broadband signals, and the signals are inevitably distorted by the nonlinear devices to generate spectrum regeneration, so that the suppression degree of side lobes is reduced in the imaging process, the occurrence of the side lobes can cause image distortion of complex targets and the reduction of the dynamic range of broadband target identification, and the target identification and high-precision imaging cannot be satisfied.
In 2006, yang Wenjun, xu Yong, etc. in the extraction method of distortion compensation signals of broadband radar system published by modern radars, it is pointed out that when the range sidelobe requirement of the system is not higher than-30 dB, the in-band phase frequency fluctuation of the system must be smaller than 3.6 ° and the amplitude fluctuation is smaller than 0.5dB.2021, sun Jili, zhang Pingdeng in the on-board SAR LFM signal in-orbit phase predistortion compensation method published by the university of halbing industry, indicated that in SAR radar systems requiring moving object identification and high precision imaging, in-band phase distortion of LFM signals is typically required to be within 5 °. Therefore, the whole receiving-transmitting loop is required to perform error analysis and model generation on the distortion of the transmitted LFM broadband signal, and the error analysis and model generation are used for performing predistortion so as to compensate the influence of nonlinear devices and other components in the system on the signal, thereby increasing the sidelobe suppression degree of the LFM signal in the pulse compression process and improving the imaging precision.
Fig. 1 is a schematic diagram of a structural part of a SAR radar transceiver in the prior art, and as shown in fig. 1, a receiving and transmitting system includes: control system 101, radar signal source 103, digital-to-analog conversion (DAC) 104, mixer 105, filter 106, power amplifier 107, circulator 108, local oscillator 1010, low noise amplifier 1011, mixer 1012, filter 1013, analog-to-digital conversion (ADC) 1015, data storage unit 1015, and the like.
Wherein the signal transmitting section includes: control system 101, radar signal source 103, digital-to-analog conversion (DAC) 104, mixer 105, filter 106, power amplifier 107, circulator 108, and local oscillator 1010. The working flow of the transmitting part is that the control system 101 controls the radar signal source 103 to transmit the digital LFM signal according to the configuration parameters such as the required signal bandwidth, time width and the like, the digital-to-analog conversion (DAC) 104 converts the digital LFM signal into an analog signal, the local oscillator 1010 is needed to up-convert the intermediate frequency analog signal to the radio frequency through the mixer 105 due to the lower frequency of the signal, the band-pass filter 106 is used to suppress the out-of-band spurious, and the power of the transmitted signal is amplified through the power amplifier 107 and then transmitted through the antenna by the circulator 108. The receiving section includes: circulator 108, local oscillator 1010, low noise amplifier 1011, mixer 1012, filter 1013, analog-to-digital conversion (ADC) 1014. The receive part of the operation is that the antenna amplifies the received signal by low noise amplifier 1011 after passing through circulator 108, then down-converts the rf analog signal to an intermediate frequency by local oscillator 1010 and mixer 1012, since there are multiple harmonics of the output signal after passing through mixer 1012, and thus filter 1012 is required to filter the signal, and then the analog signal is converted into digital signal by analog-to-digital converter (ADC) 1014 for data storage 1015. According to analysis, the whole transceiving flow channel generates amplitude and phase distortion on the LFM signal, so that the main lobe width, the integral side lobe ratio (LSLR), the Peak Side Lobe Ratio (PSLR) and the like of the pulse compression of the LFM signal are affected, and further the imaging contrast is reduced.
For the above problems, there are three methods currently available, the first is a method of analyzing the nonlinear characteristics of the transmitter to obtain a predistortion compensation function, the second is a method of time domain estimation, and the third is a method of performing analysis calculation using a scaling loop (i.e., fig. 2). A predistortion processing method, a predistortion processing device and a predistortion processing system (CN 108449294A) are provided, and the main technical scheme is that a saturation peak power threshold of an input signal of a predistortion module is obtained according to a saturation peak power and a peak growth factor of an output signal to obtain a predistortion coefficient. The technical scheme adopted in the predistortion correction method, the predistortion correction device and the transmitter, namely the base station (CN 102893399A), is that the distorted time domain signal is subjected to band limiting processing, so that the predistortion signal is obtained after the time domain signal in the multi-order bandwidth and the coefficient in the digital predistortion model are calculated. However, the above method has a disadvantage in that only nonlinear effects of the transmitting system are considered, and effects caused by the receiving system are ignored. For the time domain estimation method, in 2001, zhu Guofu, dong Zhen, etc., in "phase error correction of ultra wideband radar System by phase gradient method" published by national defense university of science and technology, a phase gradient method (PG) was proposed, which is based on a parameter-free self-focusing technique: the phase gradient self-focusing (PGA) is improved, and is a time domain estimation method, the estimation of the phase error is obtained by integrating the derivative of the phase error, but the method has the defects of strong dependence on ground objects, accurate extraction of errors can be realized only by echoes of strong scattering points like corner reflectors, experiments are usually carried out in a microwave darkroom for accurately extracting the phase error of the system, the phase error of the system cannot be measured in different environments in real time, and the algorithm has the other defect of being incapable of estimating and correcting the system amplitude error carried by echo signals. In 2005, in electronic and informatics report "extraction and correction of amplitude and phase errors of synthetic aperture radar system based on internal calibration signals", three calibration loops based on three paths are provided, which are respectively: a method for measuring and analyzing phase and amplitude characteristics of portions of a radar transceiver system with reference to a calibration loop, a transmit calibration loop, and a receive calibration loop. The principle of the calibration loop analysis method is also simple, and assuming that the frequency domain expression of the signal transmitted by the radar signal source 103 is S (f) and the transfer function of the system is H (f), it is known that the frequency domain expression R (f) =s (f) H (f) of the signal received through the whole closed loop data storage unit 1015, since R (f) and S (f) are known, the transfer function of the system can be obtainedThus an error correction function, i.e. a predistortion compensation function, is obtained. In 2020, deng Xiang, haes, and the like, the remote sensing technology and the method and implementation of applying the intra-AGILEDARN radar calibration method adopt a two-way intra-calibration loop method to obtain amplitude and phase error functions of different channels in the multi-channel radar system. The scaling loop analysis method is not influenced by the characteristics of ground objects, the amplitude and phase characteristics of different parts of the radar receiving and transmitting system can be analyzed and solved, but the design of a scaling loop is additionally added, the amplitude and phase errors are solved by the scaling loop analysis method in a frequency domain, the solving method of a transfer function is quite large, and the influence of the whole system on the amplitude and phase of a radar transmitting signal can be calculated in real time.
However, in the calibration loop analysis method, a scaler is needed, and when the scaler itself introduces errors, the system cannot avoid, so that calibration errors are caused, the errors introduced by the calibration loop cannot be eliminated, and the calibration loop method is only suitable for radars with high transmitting power.
Disclosure of Invention
In order to solve the above problems in the prior art, the present invention provides a predistortion compensation method, module and transceiver system of a synthetic aperture radar system. The technical problems to be solved by the invention are realized by the following technical scheme:
a predistortion compensation method of a synthetic aperture radar system, comprising:
Storing and extracting effective signal data in closed-loop data, and opening up a storage space by taking the pulse number as a row to store the effective signal data;
decomposing the amplitude of the effective signal data pulse by taking the solution of the Legendre function as an orthogonal basis to obtain the amplitude and the amplitude error of each order;
Decomposing the phases of the effective signal data pulses by taking the solution of the Legendre function as an orthogonal basis to obtain phases and phase errors of each order;
integrating the amplitude error and the phase error to obtain a system amplitude-phase function;
When the front and back data rates of the system are not matched and the transmitting rate is larger than the receiving rate, performing interpolation filtering processing on the system amplitude-phase function to obtain a new amplitude-phase function; or when the front and back data rates of the system are not matched and the transmitting rate is smaller than the receiving rate, extracting and filtering the system amplitude-phase function to obtain a new amplitude-phase function; or when the front and back data rates of the system are matched, inverting the amplitude-phase function to obtain a predistortion compensation function;
And the radar signal source reads the predistortion compensation function to generate a radar signal.
In one embodiment, the effective signal data pulse amplitude is:
Wherein:
n represents the order.
In one embodiment, the effective signal data pulse phase is:
Wherein:
n represents the order.
In one embodiment, the system amplitude-phase function is:
H0(x)＝A0(x)exp0(φ(x))。
The invention also provides a predistortion compensation module of the synthetic aperture radar system, comprising:
the data storage unit is used for storing and extracting effective signal data in the closed-loop data, and opening up a storage space by taking the pulse number as a row to store the effective signal data;
The data analysis unit is used for decomposing the amplitude of the effective signal data pulse by taking the solution of the Legendre function as an orthogonal basis to obtain the amplitude and the amplitude error of each order; decomposing the phases of the effective signal data pulses by taking the solution of the Legendre function as an orthogonal basis to obtain phases and phase errors of each order; integrating the amplitude error and the phase error to obtain a system amplitude-phase function;
The data predistortion unit is used for carrying out interpolation filtering processing on the system amplitude-phase function to obtain a new amplitude-phase function when the front data rate and the back data rate of the system are not matched and the transmitting rate is larger than the receiving rate; or when the front and back data rates of the system are not matched and the transmitting rate is smaller than the receiving rate, extracting and filtering the system amplitude-phase function to obtain a new amplitude-phase function; or when the front and back data rates of the system are matched, inverting the amplitude-phase function to obtain a predistortion compensation function;
And the radar signal source is used for reading the predistortion compensation function to generate a radar signal.
And the control system is used for controlling the working modes of the data storage unit, the data analysis unit, the data predistortion unit and the radar signal source.
In one embodiment, the effective signal data pulse amplitude is:
Wherein:
n represents the order.
In one embodiment, the effective signal data pulse phase is:
Wherein:
n represents the order.
In one embodiment, the system amplitude-phase function is:
H0(x)＝A0(x)exp0(φ(x))。
the invention also provides a synthetic aperture radar receiving and transmitting system, which comprises a signal transmitting end and a signal receiving end, wherein the signal transmitting end comprises a digital-to-analog converter, a transmitting end mixer, a transmitting end filter, a power amplifier and a circulator which are sequentially connected; the signal receiving end comprises a low noise amplifier, a receiving end mixer, a receiving end filter and an analog-to-digital converter which are connected in sequence; the local oscillator is connected with the transmitting end mixer and the receiving end mixer; the system also comprises a predistortion compensation module of the synthetic aperture radar system, wherein the radar signal source is connected with the digital-to-analog converter, and the data storage unit is connected with the analog-to-digital converter.
The invention has the beneficial effects that:
1. The method adopts the Legend function solution to decompose the signal into the orthogonal basis to obtain the amplitude and phase distortion of each order, and compared with a time domain method, the method can solve the amplitude distortion without being interfered and limited by the characteristics of the ground object;
2. Because the nonlinear distortion components of the Rodrigues (Rodrigues-Luo Juge) formula are completely orthogonal, the correlation is zero, the solution of the amplitude and phase errors of different orders of the system can be realized, and the amplitude and phase errors of different orders can be selected for compensation according to actual needs;
3. For the radar with smaller transmitting power, the technical scheme of the invention does not need to design an extra scaling loop, greatly reduces the complexity of hardware implementation and is suitable for engineering implementation.
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Drawings
FIG. 1 is a schematic diagram of a structural part of a SAR radar transceiver device in the prior art;
FIG. 2 is a schematic diagram of a SAR radar transceiver device in a calibration loop in the prior art
FIG. 3 is a schematic flow chart of a predistortion compensation method for a synthetic aperture radar system according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a predistortion compensation module of a synthetic aperture radar system according to an embodiment of the present invention;
fig. 5 is a schematic diagram of a synthetic aperture radar transceiver system according to an embodiment of the present invention;
FIG. 6 is a flow chart of predistortion operation in one embodiment provided by an embodiment of the present invention;
FIG. 7 illustrates the magnitude error of each order of the uncompensated system;
FIG. 8 illustrates the various stages of the phase error of the system without compensation;
FIG. 9 is a graph of the amplitude error of each stage of the system after compensation;
FIG. 10 shows the phase error of each stage of the system after compensation;
FIG. 11 is an uncompensated system signal eye diagram;
fig. 12 is a compensated system signal eye diagram.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but embodiments of the present invention are not limited thereto.
Example 1
Referring to fig. 3, fig. 3 is a flowchart of a predistortion compensation method of a synthetic aperture radar system according to an embodiment of the present invention, including:
S111, storing and extracting effective signal data in closed-loop data, and opening up a storage space by taking the pulse number as a row to store the effective signal data;
Specifically, the radar signal source 103 firstly sends out closed-loop data through the whole loop, so that the data in the closed-loop data packet contains delay, and meanwhile, because the signal sent by the radar signal source 103 is inserted with parameters such as signal time width, bandwidth, working mode, sampling rate and the like, all the data need to be processed, invalid parts are removed, and the current signal time width, bandwidth, PRF and sampling rate are read according to the data format for the input parameters of the subsequent predistortion part. For extraction of effective signal data, the characteristics of the signal need to be considered, and for the transmitted LFM signal, effective information can be extracted from the received data through phase solving. For valid signal data segments, a statistical analysis is subsequently required, so that the data are stored for rows according to the number of pulses.
S112, decomposing the amplitude of the effective signal data pulse by taking the Legendre function solution as an orthogonal basis to obtain amplitude and amplitude errors of each order;
it will be appreciated that the solution to the Legendre function, namely the Rodrigues-Luo Juge equation, is used as the orthonormal basis after extraction of the valid signal data segment. After decomposing the amplitude of the signal, the amplitude of the signal a (x) can be expressed as:
Wherein:
Where n=i represents the i-th order, so that the amplitude and the amplitude error of each order can be obtained.
S113, decomposing the phases of the effective signal data pulses by taking the Legendre function solution as a quadrature basis to obtain phases and phase errors of each order;
Specifically, after the effective signal data segment is extracted, the solution of the Legendre function, namely the Rodrigues-Luo Juge formula, is used as an orthogonal basis. After decomposing the signal, the phase of the signal, φ (x), can be expressed as:
Wherein:
Where n=i represents the i-th order, whereby the phase and phase error of each order can be obtained.
The invention decomposes the signal by adopting the solution of the Legendre function as the quadrature basis to obtain the amplitude and phase distortion of each order, compared with a time domain method, the amplitude distortion can be solved, meanwhile, the interference and the limitation of the ground feature characteristics are avoided, and as the non-linear distortion components of the Rodrigues (Rodrigues-Luo Juge) formula are completely orthogonal, the correlation is zero, the solution of the amplitude and phase errors of different orders of the system can be realized, and the amplitude and phase errors of different orders can be selected for compensation according to actual needs.
S114, integrating the amplitude error and the phase error to obtain a system amplitude-phase function;
It will be appreciated that once the amplitude transfer function and the phase transfer function of the system are obtained, they need to be integrated to obtain the amplitude phase function H 0(x)＝A0(x)exp0 (x) of the system.
S115, when the front and back data rates of the system are not matched and the transmitting rate is larger than the receiving rate, performing interpolation filtering processing on the system amplitude-phase function to obtain a new amplitude-phase function; or when the front and back data rates of the system are not matched and the transmitting rate is smaller than the receiving rate, extracting and filtering the system amplitude-phase function to obtain a new amplitude-phase function; or when the front and back data rates of the system are matched, inverting the amplitude-phase function to obtain a predistortion compensation function;
It will be appreciated that when the transmission data rate is greater, the resulting system amplitude-phase function needs to be interpolated to increase the data rate of the system so that it matches the data rate of the radar signal source, but the frequency domain of the system amplitude-phase function changes due to interpolation, so that the interpolated data needs to be filtered to obtain a new system transfer function H (x) =a (x) exp (Φ (x)).
When the transmission data rate is smaller, the obtained system amplitude-phase function needs to be extracted, the data rate of the system is reduced, so that the system is matched with the data rate of the radar signal source, but the frequency domain of the system amplitude-phase function changes due to extraction, and therefore, the extracted data needs to be subjected to filter processing, and a new system transfer function H (x) =A (x) exp (phi (x)) is obtained.
The system's amplitude-phase function is inverted by H -1 (x) =exp (-phi (x))/a (x).
S116, the radar signal source reads the predistortion compensation function to generate a radar signal.
Specifically, when the frequency domain expression of the signal transmitted by the radar signal source 103 is S (x), and the transfer function of the system is H (x), it is known that the signal received by the whole closed loop data storage unit 1015 is R (x) =s (x) H (x), and when the signal is output to the radar signal source S 1(x)＝S(x)H-1 (x), the signal received by the whole closed loop data storage unit 1015 is R (x) =s 1(x)H(x)＝S(x)H(x)-1 H (x) =s (x), so that the amplitude-phase error of the system is eliminated.
Example two
The present invention also provides a predistortion compensation module of a synthetic aperture radar system, please refer to fig. 4, comprising:
the data storage unit is used for storing and extracting effective signal data in the closed-loop data, and opening up a storage space by taking the pulse number as a row to store the effective signal data;
The data analysis unit is used for decomposing the amplitude of the effective signal data pulse by taking the solution of the Legendre function as an orthogonal basis to obtain the amplitude and the amplitude error of each order; decomposing the phases of the effective signal data pulses by taking the solution of the Legendre function as an orthogonal basis to obtain phases and phase errors of each order; integrating the amplitude error and the phase error to obtain a system amplitude-phase function;
The data predistortion unit is used for carrying out interpolation filtering processing on the system amplitude-phase function to obtain a new amplitude-phase function when the front data rate and the back data rate of the system are not matched and the transmitting rate is larger than the receiving rate; or when the front and back data rates of the system are not matched and the transmitting rate is smaller than the receiving rate, extracting and filtering the system amplitude-phase function to obtain a new amplitude-phase function; or when the front and back data rates of the system are matched, inverting the amplitude-phase function to obtain a predistortion compensation function;
And the radar signal source is used for reading the predistortion compensation function to generate a radar signal.
And the control system is used for controlling the working modes of the data storage unit, the data analysis unit, the data predistortion unit and the radar signal source.
In one embodiment, the effective signal data pulse amplitude is:
Wherein:
n represents the order.
In one embodiment, the effective signal data pulse phase is:
Wherein:
n represents the order.
In one embodiment, the system amplitude-phase function is:
H0(x)＝A0(x)exp0(φ(x))。
The invention also provides a synthetic aperture radar receiving and transmitting system, referring to fig. 5, comprising a signal transmitting end and a signal receiving end, wherein the signal transmitting end comprises a digital-to-analog converter, a transmitting end mixer, a transmitting end filter, a power amplifier and a circulator which are sequentially connected; the signal receiving end comprises a low noise amplifier, a receiving end mixer, a receiving end filter and an analog-to-digital converter which are connected in sequence; the local oscillator is connected with the transmitting end mixer and the receiving end mixer; the system also comprises a predistortion compensation module of the synthetic aperture radar system, wherein the radar signal source is connected with the digital-to-analog converter, and the data storage unit is connected with the analog-to-digital converter.
Example III
This embodiment shows the flow of predistortion operation in one specific example, see figure 6,
S111, storing and extracting effective signal data in closed-loop data, and opening up a storage space by taking the pulse number as a row to store the effective signal data;
S112, decomposing the amplitude of the effective signal data pulse by taking the Legendre function solution as an orthogonal basis to obtain amplitude and amplitude errors of each order;
S113, decomposing the phases of the effective signal data pulses by taking the Legendre function solution as a quadrature basis to obtain phases and phase errors of each order;
s114, integrating the amplitude error and the phase error to obtain a system amplitude-phase function;
s117, judging whether the front and back data rates of the system are matched, if not, executing S118, and if so, executing S121;
s118, judging whether the transmitting rate is larger than the receiving rate, if not, executing S119, and if so, executing S120;
S120, performing interpolation filtering processing on the amplitude-phase function of the system to obtain a new amplitude-phase function;
s121, inverting the amplitude-phase function of the system to obtain a predistortion compensation function and storing the predistortion compensation function;
S122, the radar signal source reads the predistortion compensation function to generate a radar signal.
When implemented in this particular example, the sampling window of the system is 40us wide, the signal bandwidth is 600MHz, and the signal time width is 30us. When the predistortion processing is not performed, the uncompensated amplitude error is 1.8dB as shown in fig. 7, and the uncompensated phase error is 28 ° as shown in fig. 8. The implementation is performed according to the steps described above, referring to fig. 9, after the compensation algorithm of the present invention, referring to fig. 10, the amplitude error is reduced to 0.41dB after the compensation of the present invention, and the phase error is 1.8 °. The signal after predistortion is more convergent as can be seen from the front-to-back comparison of the signal eye diagrams of fig. 11 and 12. Therefore, the digital predistortion device and the compensation algorithm of the invention can well compensate amplitude and phase distortion caused by nonlinear devices in a system.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Further, one skilled in the art can engage and combine the different embodiments or examples described in this specification.
Although the application is described herein in connection with various embodiments, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed application, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (devices) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The foregoing is a further detailed description of the invention in connection with the preferred embodiments, and it is not intended that the invention be limited to the specific embodiments described. It will be apparent to those skilled in the art that several simple deductions or substitutions may be made without departing from the spirit of the invention, and these should be considered to be within the scope of the invention.
Claims (9)
1. A method of predistortion compensation for a synthetic aperture radar system, comprising:
Storing and extracting effective signal data in closed-loop data, and opening up a storage space by taking the pulse number as a row to store the effective signal data;
decomposing the amplitude of the effective signal data pulse by taking the solution of the Legendre function as an orthogonal basis to obtain the amplitude and the amplitude error of each order;
Decomposing the phases of the effective signal data pulses by taking the solution of the Legendre function as an orthogonal basis to obtain phases and phase errors of each order;
integrating the amplitude error and the phase error to obtain a system amplitude-phase function;
When the front and back data rates of the system are not matched and the transmitting rate is larger than the receiving rate, performing interpolation filtering processing on the system amplitude-phase function to obtain a new amplitude-phase function; when the front and back data rates of the system are not matched and the transmitting rate is smaller than the receiving rate, extracting and filtering the system amplitude-phase function to obtain a new amplitude-phase function; when judging that the front and back data rates of the system are matched, inverting the amplitude-phase function to obtain a predistortion compensation function;
And the radar signal source reads the predistortion compensation function to generate a radar signal.
2. The method of predistortion compensation for a synthetic aperture radar system of claim 1, wherein said effective signal data pulse amplitude is:
Wherein:
n represents the order.
3. The method of predistortion compensation for a synthetic aperture radar system of claim 1, wherein said effective signal data pulse phase is:
Wherein:
n represents the order.
4. The method of predistortion compensation for a synthetic aperture radar system of claim 1, wherein said system amplitude-phase function is:
H0(x)＝A0(x)exp0(φ(x))。
5. A predistortion compensation module for a synthetic aperture radar system, comprising:
the data storage unit is used for storing and extracting effective signal data in the closed-loop data, and opening up a storage space by taking the pulse number as a row to store the effective signal data;
The data analysis unit is used for decomposing the amplitude of the effective signal data pulse by taking the solution of the Legendre function as an orthogonal basis to obtain the amplitude and the amplitude error of each order; decomposing the phases of the effective signal data pulses by taking the solution of the Legendre function as an orthogonal basis to obtain phases and phase errors of each order; integrating the amplitude error and the phase error to obtain a system amplitude-phase function;
The data predistortion unit is used for carrying out interpolation filtering processing on the system amplitude-phase function to obtain a new amplitude-phase function when the front data rate and the back data rate of the system are not matched and the transmitting rate is larger than the receiving rate; when the front and back data rates of the system are not matched and the transmitting rate is smaller than the receiving rate, extracting and filtering the system amplitude-phase function to obtain a new amplitude-phase function; when judging that the front and back data rates of the system are matched, inverting the amplitude-phase function to obtain a predistortion compensation function;
the radar signal source is used for reading the predistortion compensation function to generate a radar signal;
And the control system is used for controlling the working modes of the data storage unit, the data analysis unit, the data predistortion unit and the radar signal source.
6. The predistortion compensation module of a synthetic aperture radar system of claim 5, wherein said effective signal data pulse amplitude is:
Wherein:
n represents the order.
7. The predistortion compensation module of a synthetic aperture radar system of claim 5, wherein said effective signal data pulse phase is:
Wherein:
n represents the order.
8. The predistortion compensation module of a synthetic aperture radar system of claim 5, wherein said system amplitude-phase function is:
H0(x)＝A0(x)exp0(φ(x))。
9. The synthetic aperture radar receiving and transmitting system comprises a signal transmitting end and a signal receiving end, wherein the signal transmitting end comprises a digital-to-analog converter, a transmitting end mixer, a transmitting end filter, a power amplifier and a circulator which are sequentially connected; the signal receiving end comprises a low noise amplifier, a receiving end mixer, a receiving end filter and an analog-to-digital converter which are connected in sequence; the local oscillator is connected with the transmitting end mixer and the receiving end mixer; it is characterized in that the method comprises the steps of,
A predistortion compensation module for a synthetic aperture radar system as set out in any of claims 5 to 8, wherein said radar signal source is coupled to said digital to analog converter and said data storage unit is coupled to said analog to digital converter.
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