A method of wideband signal amplitude and phase correction combined with error compensation

Abstract

This invention discloses a broadband signal amplitude and phase correction method with joint error compensation. It utilizes reference channel technology to compensate for waveform nonlinearity caused by hardware circuitry, employs a joint error compensation method to estimate and compensate for amplitude and phase errors during broadband synthesis, and finally performs distortion correction through a frequency domain correction algorithm. This achieves amplitude and phase correction processing of broadband signals, improves imaging resolution, reduces amplitude and phase distortion, and obtains clearer and more accurate target images.

Description

Technical Field

[0001] This invention relates to the field of aerospace technology, and in particular to a broadband signal amplitude and phase correction method with combined error compensation. Background Technology

[0002] To meet the application requirements of high-resolution imaging, traditional optical radar cannot operate normally in complex environments such as strong backlighting, which limits its functionality. In contrast, microwave imaging radar has all-weather, all-day operation, and can acquire target images regardless of lighting conditions. Acquiring high-resolution images of targets, especially space targets, requires high-precision amplitude and phase compensation of the radar echo to improve imaging resolution, reduce amplitude and phase distortion, and obtain clearer and more accurate target images.

[0003] Therefore, it is necessary to propose a broadband signal amplitude and phase correction method with joint error compensation. Summary of the Invention

[0004] This invention provides a broadband signal amplitude and phase correction method with joint error compensation to perform high-precision amplitude and phase compensation on radar echoes, improve imaging resolution, reduce amplitude distortion and phase distortion, and obtain clearer and more accurate target images.

[0005] To achieve the above objectives, the present invention provides a broadband signal amplitude and phase correction method with joint error compensation, comprising:

[0006] The reference channel technique is used to estimate and compensate for the phase error caused by the non-ideal circuitry in the radar waveform generation system based on the sharpening function.

[0007] Based on the actual radar echo signal model received by each sub-band, a compensation function is designed to compensate for the linear phase error introduced by multi-channel transmission.

[0008] The echo signal after linear phase error compensation is subjected to range pulse compression processing, and the range spectrum is obtained by superimposing along the azimuth. The spectrum is then subjected to error fitting extraction based on the filtering function, and a spectrum amplitude error compensation function is constructed.

[0009] The higher-order phase error of the signal is extracted by the internal calibration loop, and the higher-order phase error compensation is performed on the signal after range pulse compression.

[0010] Perform an inverse Fourier transform on the signal, rearrange and splice each step frequency sub-band in order of carrier frequency, and move each sub-band signal to its respective center frequency point.

[0011] In the frequency domain, the frequency domain distortion coefficients are obtained through the baseband linear frequency modulated signal, and the correction coefficients are obtained by inverting the signal to correct the distortion.

[0012] Optionally, the use of reference channel technology to estimate and compensate for phase errors caused by non-ideals in the radar waveform generation system based on a sharpening function includes:

[0013] The target channel signal model and the reference channel signal model after heterodyning in the time domain are calculated, and the error phase ratio is obtained by taking the logarithm of their phases:

[0014]

[0015] Where, τ tar For the target delay, τ tar_lo For the target local oscillator delay, τ ref For reference delay, τ ref_lo For reference local oscillator delay;

[0016] The phase ratio of each error is estimated based on the sharpening function, and the phase error of the target channel is compensated using information from the reference channel.

[0017] Optionally, the step of designing a compensation function based on the actual radar echo signal model received by each sub-band to compensate for the linear phase error introduced by multi-channel transmission includes:

[0018] In frequency domain broadband synthesis, based on the calculated actual radar echo model received by each sub-band, the linear phase error introduced by multi-channel transmission is obtained, and a compensation function is constructed to compensate for the low-order linear phase error.

[0019] Optionally, the step of extracting the error from the spectrum based on the filtering function and constructing the spectrum amplitude error compensation function includes:

[0020] Error fitting and extraction are performed on the non-flat distance spectrum using a wavelet filtering function, resulting in the filtered error curve A. w (f r A spectrum amplitude error compensation function was constructed:

[0021]

[0022] in, The mean of the filtered error curve is calculated using H. w (f r ;k), by compensating the range frequency domain signal, an approximately flat range spectrum characteristic is obtained.

[0023] Optionally, the step of extracting the higher-order phase error of the signal through the internal calibration loop and compensating for the higher-order phase error of the signal after range pulse compression includes:

[0024] The calibration signal is used to record radar system link information that closely approximates the actual echo signal, forming an internal calibration loop. Higher-order phase errors of the signal are extracted from this loop to construct internal calibration compensation terms.

[0025] H high (k)=exp(jφ high (k))

[0026] Where, φ high (k) represents the higher-order phase error of the signal, and the higher-order phase error of the sub-band signal is compensated by the internal calibration compensation term.

[0027] Optionally, the step of obtaining frequency domain distortion coefficients from a baseband linear frequency modulated signal in the frequency domain and then using an inversion method to obtain correction coefficients for distortion correction includes:

[0028] The distortion function is multiplied by the baseband linear frequency modulated signal and then transformed to the frequency domain using a Fourier transform.

[0029] Calculate the spectral derivative of the baseband linear frequency modulated signal to deduce the spectrum of the distortion coefficient;

[0030] The distortion correction coefficients are obtained by inverting the values ​​and then corrected in the frequency domain.

[0031] Optionally, after obtaining the frequency domain distortion coefficients from the baseband linear frequency modulated signal in the frequency domain and obtaining the correction coefficients by inversion for distortion correction, the method further includes:

[0032] After correction, an inverse Fourier transform is performed to obtain the distortion-corrected echo signal;

[0033] The corrected signal is then subjected to pulse compression processing to obtain the final imaging result.

[0034] Optionally, shifting each sub-band signal to its respective center frequency includes:

[0035] Perform a Fourier transform on the signal to distribute the multi-subband signals within their respective frequency ranges.

[0036] On the other hand, the present invention provides an electronic device including a processor and a memory, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, it implements the above-described broadband signal amplitude and phase correction method with joint error compensation.

[0037] On the other hand, the present invention provides a readable storage medium storing a computer program, which, when executed by a processor, implements the above-described broadband signal amplitude and phase correction method with joint error compensation.

[0038] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0039] 1. The present invention provides a broadband signal amplitude and phase correction method with combined error compensation, which realizes high-precision compensation of the amplitude and phase of broadband signals.

[0040] 2. The broadband signal amplitude and phase correction method of the present invention uses reference channel technology to compensate for phase errors caused by circuit non-ideality, thereby improving the accuracy of image interpretation and subsequent analysis.

[0041] 3. The broadband signal amplitude and phase correction method of the present invention estimates and compensates for the amplitude and phase errors introduced by the system in the frequency domain based on the joint error compensation method, thereby realizing multi-subband coherent synthesis.

[0042] 4. This invention can correct distortion through a frequency domain correction algorithm, overcoming the effects of time delay and the sensitivity of traditional distortion algorithms to the position of the target scattering point relative to the receiving window.

[0043] 5. The frequency domain correction algorithm designed in this invention has simple implementation steps and is relatively easy to apply to radar systems.

[0044] This invention provides a broadband signal amplitude and phase correction method with combined error compensation, which has the advantages of simple compensation algorithm, obvious error compensation and imaging effect. Attached Figure Description

[0045] Figure 1 This is a framework diagram of a broadband signal amplitude and phase correction method with joint error compensation according to an embodiment of the present invention;

[0046] Figure 2 Output waveform diagram for heterodyne experiment;

[0047] Figure 3 This is a phase diagram of nonlinear error;

[0048] Figure 4 The images show the effects before and after phase error compensation.

[0049] Figure 5 The graphs show the amplitude of the spectrum before and after distance-spectral compensation within the sub-band.

[0050] Figure 6 This is a schematic diagram of a frequency shift distortion correction algorithm;

[0051] Figure 7 This is a one-dimensional distance image of the simulation data before and after distortion correction. Detailed Implementation

[0052] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates the broadband signal amplitude and phase correction method with joint error compensation proposed in this invention. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, used only to facilitate and clearly illustrate the embodiments of this invention. Please refer to the drawings to make the objectives, features, and advantages of this invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation conditions of this invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.

[0053] Please see Figure 1 , Figure 1 This is a framework diagram of a broadband signal amplitude and phase correction method with joint error compensation according to an embodiment of the present invention. This embodiment provides a broadband signal amplitude and phase correction method with joint error compensation. Due to the non-ideal nature of the circuits in each stage of the radar waveform generation system, the generated signal is not an ideal linear frequency modulated signal, and each sub-band signal inevitably has certain errors introduced during transmission and reception. This method achieves high-precision amplitude and phase correction compensation technology through a joint error compensation method of frequency nonlinear compensation algorithm, amplitude compensation and phase compensation of each sub-band, and distortion correction algorithm based on the frequency domain.

[0054] This embodiment provides a broadband signal amplitude and phase correction method with joint error compensation, including:

[0055] The reference channel technique is used to estimate and compensate for the phase error caused by the non-ideal circuitry in the radar waveform generation system based on the sharpening function.

[0056] Based on the actual radar echo signal model received by each sub-band, a compensation function is designed to compensate for the linear phase error introduced by multi-channel transmission.

[0057] The echo signal after linear error compensation is subjected to range pulse compression processing, and the range spectrum is obtained by superimposing along the azimuth. The spectrum is then subjected to error fitting extraction based on the filtering function, and a spectrum amplitude error compensation function is constructed.

[0058] The higher-order phase error of the signal is extracted by the internal calibration loop, and the higher-order phase error compensation is performed on the signal after range pulse compression.

[0059] Perform an inverse Fourier transform on the signal, rearrange and splice each step frequency sub-band in order of carrier frequency, and move each sub-band signal to its respective center frequency point.

[0060] In the frequency domain, the frequency domain distortion coefficients are obtained through the baseband linear frequency modulated signal, and the correction coefficients are obtained by inverting the signal to correct the distortion.

[0061] Specifically, firstly, by calculating the target channel signal model and the reference channel signal model after heterodyning in the time domain, the error phase ratio can be obtained by taking the logarithm of their phases:

[0062]

[0063] Where, τ tar For the target delay, τ tar_lo For the target local oscillator delay, τ ref For reference delay, τ ref_lo The local oscillator delay is used as a reference. Then, the phase ratio of each error is estimated based on the sharpening function, thereby using information from the reference channel to compensate for the phase error of the target channel. Figure 2 The waveform diagram of the heterodyne experiment output shows that the signal displayed by the oscilloscope is not a standard sine wave signal. The signal has varying density, indicating that the transmitted signal has a higher phase. Even after de-frequency modulation, the signal still has a higher phase. De-frequency modulation alone cannot complete pulse compression. Figure 3 The image shows the phase diagram of the nonlinear error. By estimating p using the sharpening function curve for compensation, the effect diagrams before and after phase error compensation can be obtained, as shown below. Figure 4 As shown, the upper wide pulse is the result without error compensation, while the lower narrow pulse is the result after error compensation, thus verifying the effectiveness of the method.

[0064] In broadband frequency domain synthesis, based on the calculated actual radar echo models received by each sub-band, the linear phase error introduced by multi-channel transmission can be obtained. A corresponding compensation function is then constructed to compensate for the low-order linear phase error. After compensation, a Fourier transform is performed on the signal to obtain the frequency domain signal after range pulse compression.

[0065] Due to the influence of hardware circuitry, the amplitude within the subband is not flat. Without prior correction, this will increase the sidelobes of the pulse compression signal. By superimposing the range-frequency domain signals along the azimuth, the range-frequency distribution is statistically obtained. Figure 5 As shown in the image on the left, the distance spectrum is not flat. Next, a wavelet filter function is used to extract the error by fitting the non-flat spectrum, resulting in the filtered error curve A. w (f r Finally, the spectral amplitude error compensation function H was constructed. w (f r ;k) as follows

[0066]

[0067] in, The mean of the filtered error curve is calculated using H. w (f r ;k). Compensation is applied to the range-frequency domain signal to obtain an approximately flat range-frequency spectrum characteristic, such as Figure 5 As shown in the image on the right.

[0068] Considering the nonlinear effects of radar links on ultra-wideband radar signals, an internal calibration loop system is designed during radar system design. The calibration signal records radar system link information that closely approximates the actual echo signal, forming the internal calibration loop. Higher-order phase errors of the signal can be extracted from this loop to construct the internal calibration compensation term H. high (k) is as follows

[0069] H high (k)=exp(jφ high (k))

[0070] Where, φ high (k) represents the higher-order phase error of the signal. The higher-order phase error of the sub-band signal can be compensated by using the internal calibration compensation term.

[0071] After completing the fine estimation and compensation of amplitude and phase errors within the sub-bands, a relatively ideal sub-band amplitude and phase characteristic can be obtained. Next, frequency shifting processing is performed, which involves rearranging and splicing each step-frequency sub-band sequentially according to its carrier frequency. First, zeros are padded at both ends of each sub-band signal to obtain the distance-spectral amplitude of k sub-bands; then, each sub-band signal is shifted to its respective center frequency, thus distributing the multi-sub-band signals within their corresponding spectral ranges.

[0072] The broadband signal amplitude and phase correction method with joint error compensation provided in this embodiment includes frequency domain distortion correction. A schematic diagram of the frequency domain distortion correction algorithm is shown below. Figure 6 As shown, the time-domain delay is equivalent to the time-delay-related frequency exponent in the frequency domain, as determined by the time-frequency domain transformation relationship. Therefore, distortion correction performed in the frequency domain can avoid the impact of time delay on correction performance. First, the distortion function is multiplied by the baseband linear frequency modulated (LFM) signal and transformed to the frequency domain using a Fourier transform. Then, the spectrum of the distortion coefficients is calculated by determining the spectral derivative of the baseband LFM signal. The distortion correction coefficients are obtained by inverting the values ​​and corrected in the frequency domain. After correction, an inverse Fourier transform is performed to obtain the distortion-corrected echo signal. The corrected signal is then subjected to pulse compression processing to obtain the final imaging result. Simulation experiments yield the results. Figure 7 The simulation data of one-dimensional range images before and after distortion correction shows that distortion raises the range sidelobes of the one-dimensional range image of the echo. After correction by this method, the focusing effect of the one-dimensional range image is improved.

[0073] This method is primarily geared towards practical engineering applications. It uses only one reference channel and a sharpening function to compensate for errors caused by non-ideal circuits. Furthermore, this method obtains high-order phase compensation solely through an internal calibration loop, making it computationally simple and easier to implement in engineering applications. In addition, this method proposes a frequency-domain distortion correction algorithm. Based on the properties of time-frequency domain conversion, the time-domain delay is equivalent to a fixed phase term in the frequency domain. Therefore, if correction is performed in the frequency domain, the impact of the time delay can be ignored, avoiding the influence of the time delay on the correction performance and overcoming the sensitivity of traditional distortion correction algorithms to the relative position of the target scattering point to the receiving window.

[0074] This embodiment also provides an electronic device, including a processor and a memory. The memory stores a computer program, which, when executed by the processor, implements the broadband signal amplitude and phase correction method with joint error compensation described in this embodiment.

[0075] This embodiment also provides a readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the broadband signal amplitude and phase correction method with joint error compensation described in this embodiment.

[0076] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0077] It should be noted that the apparatus and methods disclosed in the embodiments herein can also be implemented in other ways. The apparatus embodiments described above are merely illustrative; for example, the flowcharts and block diagrams in the accompanying drawings show the architecture, functionality, and operation of possible implementations of apparatus, methods, and computer program products according to various embodiments herein. In this regard, each block in a flowchart or block diagram may represent a module, program, or part of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram and / or flowchart, and combinations of blocks in block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system to perform the specified function or action, or can be implemented using a combination of dedicated hardware and computer instructions.

[0078] In addition, the functional modules in the various embodiments of this article can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0079] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A broadband signal amplitude and phase correction method with joint error compensation, characterized in that, include: The reference channel technique is used to estimate and compensate for the phase error caused by the non-ideal circuitry in the radar waveform generation system based on the sharpening function. Based on the actual radar echo signal model received by each sub-band, a compensation function is designed to compensate for the linear phase error introduced by multi-channel transmission. The echo signal after linear error compensation is subjected to range pulse compression processing, and the range spectrum is obtained by superimposing along the azimuth. The spectrum is then subjected to error fitting extraction based on the filtering function, and a spectrum amplitude error compensation function is constructed. The higher-order phase error of the signal is extracted by the internal calibration loop, and the higher-order phase error compensation is performed on the signal after range pulse compression. Perform an inverse Fourier transform on the signal, rearrange and splice each step frequency sub-band in order of carrier frequency, and move each sub-band signal to its respective center frequency point. In the frequency domain, the frequency domain distortion coefficients are obtained through the baseband linear frequency modulated signal, and the correction coefficients are obtained by inverting the signal to correct the distortion.

2. The broadband signal amplitude and phase correction method with joint error compensation as described in claim 1, characterized in that, The aforementioned reference channel technology, based on sharpening function estimation, compensates for phase errors caused by non-ideals in the radar waveform generation system circuitry, including: The target channel signal model and the reference channel signal model after heterodyning in the time domain are calculated, and the error phase ratio is obtained by taking the logarithm of their phases: Where, τ tar For the target delay, τ tar_lo For the target local oscillator delay, τ ref For reference delay, τ ref_lo For reference local oscillator delay; The phase ratio of each error is estimated based on the sharpening function, and the phase error of the target channel is compensated using information from the reference channel.

3. The broadband signal amplitude and phase correction method with joint error compensation as described in claim 1, characterized in that, The step involves designing a compensation function based on the actual radar echo signal model received by each sub-band to compensate for the linear phase error introduced by multi-channel transmission, including: In frequency domain broadband synthesis, based on the calculated actual radar echo model received by each sub-band, the linear phase error introduced by multi-channel transmission is obtained, and a compensation function is constructed to compensate for the low-order linear phase error.

4. The broadband signal amplitude and phase correction method with joint error compensation as described in claim 1, characterized in that, The step of extracting errors from the spectrum based on the filtering function and constructing a spectrum amplitude error compensation function includes: Error fitting and extraction are performed on the non-flat distance spectrum using a wavelet filtering function, resulting in the filtered error curve A. w (f r A spectrum amplitude error compensation function was constructed: in, The mean of the filtered error curve is calculated using H. w (f r ;k), by compensating the range frequency domain signal, an approximately flat range spectrum characteristic is obtained.

5. The broadband signal amplitude and phase correction method with joint error compensation as described in claim 1, characterized in that, The step of extracting higher-order phase errors from the signal through the internal calibration loop and compensating for higher-order phase errors in the range pulse compressed signal includes: The calibration signal is used to record radar system link information that closely approximates the actual echo signal, forming an internal calibration loop. Higher-order phase errors of the signal are extracted from this loop to construct internal calibration compensation terms. H high (k)=exp(jφ high (k)) Where, φ high (k) represents the higher-order phase error of the signal, and the higher-order phase error of the sub-band signal is compensated by the internal calibration compensation term.

6. The broadband signal amplitude and phase correction method with joint error compensation as described in claim 1, characterized in that, The process of obtaining frequency domain distortion coefficients from a baseband linear frequency modulated signal in the frequency domain and then using an inversion method to obtain correction coefficients for distortion correction includes: The distortion function is multiplied by the baseband linear frequency modulated signal and then transformed to the frequency domain using a Fourier transform. Calculate the spectral derivative of the baseband linear frequency modulated signal to deduce the spectrum of the distortion coefficient; The distortion correction coefficients are obtained by inverting the values ​​and then corrected in the frequency domain.

7. The broadband signal amplitude and phase correction method with joint error compensation as described in claim 6, characterized in that, The process of obtaining frequency domain distortion coefficients from a baseband linear frequency modulated signal in the frequency domain, and then obtaining correction coefficients by inversion for distortion correction, further includes: After correction, an inverse Fourier transform is performed to obtain the distortion-corrected echo signal; The corrected signal is then subjected to pulse compression processing to obtain the final imaging result.

8. The broadband signal amplitude and phase correction method with joint error compensation as described in claim 1, characterized in that, The process of shifting each sub-band signal to its respective center frequency includes: Perform a Fourier transform on the signal to distribute the multi-subband signals within their respective frequency ranges.

9. An electronic device, characterized in that, It includes a processor and a memory, wherein the memory stores a computer program, which, when executed by the processor, implements the method of any one of claims 1 to 8.

10. A readable storage medium, characterized in that, The readable storage medium stores a computer program, which, when executed by a processor, implements the method of any one of claims 1 to 8.

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