Error compensation method and device, and storage medium

Abstract

This application provides an error compensation method, which includes: constructing a phase error model between a primary satellite and a secondary satellite using an error compensation device; determining the time deviation and frequency deviation between a first ultra-stable crystal oscillator corresponding to the secondary satellite and a second ultra-stable crystal oscillator corresponding to the primary satellite; determining the phase error between the primary satellite and the secondary satellite based on the time deviation, frequency deviation, and phase error model; and performing error compensation processing on the secondary satellite using the phase error, thereby enabling simpler, more efficient, and more accurate phase compensation of radar echo signals.

Description

Technical Field

[0001] This invention relates to the field of synthetic aperture radar technology, and in particular to an error compensation method and device, as well as a storage medium. Background Technology

[0002] Distributed Synthetic Aperture Radar (SAR) is a distributed Earth observation system that places multiple transmitters and / or receivers on different platforms. Due to its advantages such as rich formation configurations, flexible baseline adjustment capabilities, wide spatial distribution, reconstructable distributed aperture, and strong concealment, distributed SAR has always attracted special attention from researchers in the field of microwave remote sensing. However, the transmitters and receivers in a distributed SAR system use different reference clock sources. The time and frequency deviations of these different clock sources reduce the resolution and signal-to-noise ratio (SNR) of the radar image and cause position and elevation deviations in the Digital Elevation Model (DEM). Therefore, the time and frequency synchronization problem is a major factor limiting the rapid development of distributed SAR and a significant challenge in its realization.

[0003] Currently, time and frequency deviations can be calculated using the Push-To-Talk (PTT) scheme or other methods. However, in order to achieve distributed SAR time and frequency synchronization, the process of directly using time and frequency deviations to perform phase compensation on radar echo signals is extremely complex, which reduces the processing efficiency and accuracy of error compensation. Summary of the Invention

[0004] This application provides an error compensation method, device, and storage medium that can perform phase compensation on radar echo signals simply, efficiently, and accurately, thereby improving the processing efficiency and accuracy of error compensation.

[0005] The technical solution of this application embodiment is implemented as follows:

[0006] In a first aspect, embodiments of this application provide an error compensation method, the method comprising:

[0007] Construct a phase error model between the primary satellite and the secondary satellite;

[0008] The time deviation and frequency deviation between the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite are determined, and the phase error between the main satellite and the auxiliary satellite is determined based on the time deviation, the frequency deviation and the phase error model;

[0009] The auxiliary satellite is subjected to error compensation processing based on the phase error.

[0010] Secondly, embodiments of this application provide an error compensation device, which includes: a construction unit, a determination unit, and a processing unit.

[0011] The construction unit is used to construct a phase error model between the main satellite and the auxiliary satellite;

[0012] The determining unit is used to determine the time deviation and frequency deviation between the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite, and to determine the phase error between the main satellite and the auxiliary satellite based on the time deviation, the frequency deviation and the phase error model.

[0013] The processing unit is used to perform error compensation processing on the auxiliary satellite based on the phase error.

[0014] Thirdly, embodiments of this application provide an error compensation device, which includes: a processor and a memory; wherein,

[0015] The memory is used to store computer programs that can run on the processor;

[0016] The processor is configured to execute the error compensation method described above when running the computer program.

[0017] Fourthly, embodiments of this application provide a computer-readable storage medium, characterized in that the storage medium stores computer program code, which, when executed by a computer, implements the error compensation method described above.

[0018] This application provides an error compensation method, device, and storage medium. The method includes: the error compensation device constructing a phase error model between a primary satellite and a secondary satellite; determining the time deviation and frequency deviation between a first ultra-stable crystal oscillator corresponding to the secondary satellite and a second ultra-stable crystal oscillator corresponding to the primary satellite; and determining the phase error between the primary satellite and the secondary satellite based on the time deviation, frequency deviation, and phase error model; and performing error compensation processing on the secondary satellite using the phase error. Therefore, it can be seen that the error compensation device can first construct a phase error model between the main satellite and the auxiliary satellite, then determine the time and frequency deviations between the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite, and then determine the phase error between the main satellite and the auxiliary satellite based on the time deviation, frequency deviation, and phase error model. In other words, the error compensation device can construct a phase error model between the main satellite and the auxiliary satellite, then determine the phase error based on the phase error model, and then perform error compensation processing on the auxiliary satellite based on the phase error, rather than directly performing phase compensation on the radar echo signal based on the time and frequency deviations. This allows for simpler, more efficient, and more accurate phase compensation of the radar echo signal, thereby improving the processing efficiency and accuracy of error compensation. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the error compensation method proposed in the embodiments of this application;

[0020] Figure 2 This is a schematic diagram illustrating the relationship between the primary satellite and the secondary satellite as proposed in the embodiments of this application;

[0021] Figure 3 This is a schematic diagram illustrating the relationship between the primary satellite and the secondary satellite as proposed in the embodiments of this application. Figure 2 ;

[0022] Figure 4 This is a schematic diagram illustrating the interaction between the primary satellite and the secondary satellite as proposed in an embodiment of this application;

[0023] Figure 5 This is a schematic diagram of the process for obtaining a focused radar image according to an embodiment of this application;

[0024] Figure 6 This is a schematic diagram of the simulation results presented in the embodiments of this application. Figure 1 ;

[0025] Figure 7 This is a schematic diagram of the simulation results presented in the embodiments of this application. Figure 2 ;

[0026] Figure 8 This is a schematic diagram of the simulation results presented in the embodiments of this application. Figure 3 ;

[0027] Figure 9 This is a schematic diagram of the simulation results presented in the embodiments of this application. Figure 4 ;

[0028] Figure 10 This is a schematic diagram of the simulation results presented in the embodiments of this application. Figure 5 ;

[0029] Figure 11 This is a schematic diagram of the simulation results presented in the embodiments of this application. Figure 6 ;

[0030] Figure 12 This is a schematic diagram of the simulation results presented in the embodiments of this application. Figure 7 ;

[0031] Figure 13 This is a schematic diagram of the composition and structure of the error compensation device proposed in the embodiments of this application. Figure 1 ;

[0032] Figure 14 This is a schematic diagram of the composition and structure of the error compensation device proposed in the embodiments of this application. Figure 2 . Detailed Implementation

[0033] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for explaining the relevant application and not for limiting the application. Furthermore, it should be noted that, for ease of description, only the parts related to the relevant application are shown in the accompanying drawings.

[0034] Distributed Synthetic Aperture Radar (SAR) is a distributed Earth observation system that places multiple transmitters and / or receivers on different platforms. Due to its advantages such as rich formation configurations, flexible baseline adjustment capabilities, wide spatial distribution, reconstructable distributed apertures, and strong concealment, distributed SAR has received special attention from researchers in the field of microwave remote sensing for nearly 20 years. Major powers around the world have conducted spaceborne, spaceborne and airborne, and airborne distributed SAR Earth observation experiments and space missions. Among them, the TanDEM-X mission developed by the German Aerospace Center (DLR) is a well-known spaceborne bistatic SAR mission. It observes the Earth using two SAR satellites (TSX and TDX) operating in the X-band, arranged in a double-helix formation. In addition, the multiple sets of echo data from distributed SAR can be used for various applications, such as in-orbit and cross-orbit interferometry, tomographic imaging, and moving target detection.

[0035] However, distributed SAR systems use different reference clock sources for the transmitter and receiver. Due to limitations in modern industrial technology, the frequency accuracy of these clock sources is relatively low, making it difficult to meet the high-precision measurement and mapping requirements of distributed SAR. Time and frequency deviations between different clock sources reduce the resolution and signal-to-noise ratio (SNR) of radar images and cause position and elevation deviations in the digital elevation model (DEM). Therefore, time and frequency synchronization is a major factor limiting the rapid development of distributed SAR and a significant challenge in its implementation.

[0036] To achieve distributed SAR synchronization, researchers at the Microwave and Radar Institute of DLR proposed a pulse-switched phase synchronization scheme in 2005 and applied it to the TanDEM-X mission. However, due to the low stability of the clock (1E-8), this synchronization scheme periodically interrupted the normal operation of the radar system. To address this, researchers at the Aerospace Information Research Institute of the Chinese Academy of Sciences (AIRCAS) proposed a non-disruptive pulse-switched phase synchronization scheme in 2019 and applied it to the Land Detection-1 bistatic SAR mission. Because this scheme swaps pulses during idle time before or after the radar echo reception window, it does not affect the operation of the radar system. In 2017, Krieger et al. at DLR proposed a new phase synchronization scheme in the MirrorSAR concept, which can reduce the complexity of the secondary satellite SAR system. It should be noted that these phase synchronization schemes are all based on the principle of duplex communication to obtain the phase error between ultra-stable crystal oscillators (USOs). Unlike the above schemes, researchers at AIRCAS first proposed a time and frequency synchronization scheme based on the principle of simplex communication in 2021, defining it as the Push-To-Talk (PTT) scheme. It is worth mentioning that this scheme can directly obtain the time and frequency deviations (ε) between USOs. t and ε f Compared to pulse-switched phase synchronization schemes, PTT schemes have significant advantages, such as a higher synchronization frequency f. syn And it does not require a complex synchronous internal calibration network, etc. However, in order to achieve distributed SAR time and frequency synchronization, the ε obtained using the PTT scheme is... t and ε f The process of directly compensating for phase errors in radar echo signals is extremely complex.

[0037] To address the extremely complex process of phase compensation for radar echo signals, this application provides an error compensation method, device, and storage medium. The method includes: constructing a phase error model between a primary satellite and a secondary satellite using the error compensation device; determining the time and frequency deviations between a first ultra-stable crystal oscillator corresponding to the secondary satellite and a second ultra-stable crystal oscillator corresponding to the primary satellite; determining the phase error between the primary satellite and the secondary satellite based on the time deviation, frequency deviation, and phase error model; and performing error compensation processing on the secondary satellite using the phase error. Therefore, it can be seen that the error compensation device can first construct a phase error model between the main satellite and the auxiliary satellite, then determine the time and frequency deviations between the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite, and then determine the phase error between the main satellite and the auxiliary satellite based on the time deviation, frequency deviation, and phase error model. In other words, the error compensation device can construct a phase error model between the main satellite and the auxiliary satellite, then determine the phase error based on the phase error model, and then perform error compensation processing on the auxiliary satellite based on the phase error, rather than directly performing phase compensation on the radar echo signal based on the time and frequency deviations. This allows for simpler, more efficient, and more accurate phase compensation of the radar echo signal, thereby improving the processing efficiency and accuracy of error compensation.

[0038] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0039] Example 1

[0040] This application provides an error compensation method. Figure 1 This is a schematic diagram of the error compensation method proposed in the embodiments of this application, as shown below. Figure 1 As shown, the error compensation method of the error compensation device may include the following steps:

[0041] Step 101: Construct a phase error model between the primary satellite and the secondary satellite.

[0042] In the embodiments of this application, the error compensation device can construct a phase error model between the primary satellite and the secondary satellite.

[0043] It should be noted that, in the embodiments of this application, the error compensation device can be of various types, such as, but not limited to, any form of device such as a laptop computer.

[0044] It should be noted that in the embodiments of this application, a secondary satellite can refer to any satellite in a secondary satellite constellation, and this application does not specifically limit the number of secondary satellite constellations.

[0045] It should be noted that, in the embodiments of this application, Figure 2 This is a schematic diagram illustrating the relationship between the primary satellite and the secondary satellite as proposed in the embodiments of this application, such as... Figure 2 As shown, the auxiliary satellite constellation includes multiple auxiliary satellites. The error compensation device can construct a phase error model between the main satellite and any one of the auxiliary satellites in the auxiliary satellite constellation (R42, R32, R11, R21, R00).

[0046] It should be noted that, in the embodiments of this application, the phase error models between different auxiliary satellites and the main satellite in the auxiliary satellite constellation can be different phase error models.

[0047] For example, in the embodiments of this application, it is assumed that the auxiliary satellite group includes auxiliary satellite 1, auxiliary satellite 2, auxiliary satellite 3, ..., auxiliary satellite 10. For different auxiliary satellites in the auxiliary satellite group, the error compensation device can construct a corresponding phase error model, wherein the phase error model 1 corresponding to auxiliary satellite 1 can be constructed.

[0048] It should be noted that, in the embodiments of this application, when the error compensation device constructs the phase error model between the main satellite and the auxiliary satellite, it can first construct a first echo model based on the first initial phase corresponding to the first ultra-stable crystal oscillator, the second initial phase corresponding to the second ultra-stable crystal oscillator, and the propagation delay; then it can construct a second echo model based on the first initial phase, the second initial phase, the propagation delay, the carrier frequency of the auxiliary satellite, and the carrier frequency of the main satellite; and then determine the phase error model based on the first echo model and the second echo model.

[0049] It should be noted that, in the embodiments of this application, the first ultra-stable crystal oscillator may be an ultra-stable crystal oscillator corresponding to the SAR system of the auxiliary satellite.

[0050] It should be noted that, in the embodiments of this application, the first initial phase can be the initial phase corresponding to the ultra-stable crystal oscillator of the auxiliary satellite.

[0051] It should be noted that, in the embodiments of this application, the second ultra-stable crystal oscillator may be the ultra-stable crystal oscillator corresponding to the SAR system of the main satellite.

[0052] It should be noted that, in the embodiments of this application, the second initial phase can be the initial phase of the ultra-stable crystal oscillator of the master satellite.

[0053] It should be noted that, in the embodiments of this application, the error compensation device can determine the propagation delay by using the distance parameters of the main satellite and the distance parameters of the auxiliary satellite.

[0054] For example, in the embodiments of this application, it is assumed that the distances from the target area to the primary satellite and the i-th auxiliary satellite are R1 and R, respectively. iWhere the i-th auxiliary satellite refers to the i-th auxiliary satellite in the auxiliary satellite group, i≥1; then the propagation delay can be expressed by the following formula.

[0055] T d =(R1+R i ) / c (1)

[0056] Where c represents the speed of light.

[0057] It should be noted that, in the embodiments of this application, the first echo model can refer to the echo model of the echo received by the i-th auxiliary satellite when the time deviation and frequency deviation between the ultra-stable crystal oscillator corresponding to the auxiliary satellite and the ultra-stable crystal oscillator corresponding to the main satellite are both 0.

[0058] It should be noted that, in the embodiments of this application, the second echo model can refer to the echo model of the echo received by the i-th auxiliary satellite when the time deviation and frequency deviation between the ultra-stable crystal oscillator corresponding to the auxiliary satellite and the ultra-stable crystal oscillator corresponding to the main satellite are both non-zero.

[0059] Furthermore, in the embodiments of this application, when the error compensation device constructs the first echo model based on the first initial phase corresponding to the first ultra-stable crystal oscillator, the second initial phase corresponding to the second ultra-stable crystal oscillator, and the propagation delay, it can determine the first radar signal model transmitted by the main satellite based on the second initial phase; determine the third echo model based on the first radar signal model and the propagation delay; and determine the first echo model based on the first initial phase and the third echo model.

[0060] It should be noted that, in the embodiments of this application, Figure 3 This is a schematic diagram illustrating the relationship between the primary satellite and the secondary satellite as proposed in the embodiments of this application. Figure 2 ,like Figure 3 As shown, the third echo model can be the initial echo model of the echo received by the i-th auxiliary satellite in the auxiliary satellite group after the main satellite transmits a radar signal to illuminate the target area. The main satellite can also receive the scattered echo signal.

[0061] It should be noted that, in the embodiments of this application, it is assumed that the distributed SAR system includes only two satellites: a primary satellite and the i-th auxiliary satellite. Figure 4 This is a schematic diagram illustrating the interaction between the primary and secondary satellites as proposed in an embodiment of this application. Figure 4 As shown, the main satellite, whose clock is a super-stable crystal oscillator (USO1), transmits radar signals to illuminate the target area through the first radar signal model. Then, the auxiliary satellite receives the initial echo signal through the receiver, and obtains the first echo model through the mixer and low-pass filter. The first radar signal model can be represented by the following formula.

[0062]

[0063] Where C represents the signal amplitude, f1 represents the carrier frequency, and t r K represents the distance to a fast time. r Indicates the distance-directed frequency modulation. This indicates the initial phase of USO1.

[0064] Furthermore, in the embodiments of this application, the error compensation device can determine the third echo model, i.e., the initial echo model of the echo received by the i-th auxiliary satellite, based on the first radar signal model and the propagation delay. The third echo model can be expressed by the following formula.

[0065]

[0066] Where β represents transmission loss and C represents signal amplitude.

[0067] Furthermore, in the embodiments of this application, when the error compensation device determines the first echo model based on the first initial phase and the third echo model, it can determine the first reference mixing signal model based on the first initial phase and the third echo model; then, the first reference mixing signal model is input into the mixer and the low-pass filter to determine the first echo model.

[0068] It should be noted that, in the embodiments of this application, assuming that the time deviation and frequency deviation between the ultra-stable crystal oscillator corresponding to the i-th auxiliary satellite and the ultra-stable crystal oscillator corresponding to the main satellite are both 0, the first reference mixing signal model generated by the auxiliary satellite can be represented by the following formula.

[0069]

[0070] Where D represents the signal amplitude, This indicates the initial phase of the ultra-stable crystal oscillator corresponding to the auxiliary satellite.

[0071] Furthermore, in the embodiments of this application, such as Figure 4 As shown, after obtaining the first reference mixing signal model generated by the auxiliary satellite, the error compensation device can input the first reference mixing signal model into the mixer and low-pass filter to determine the first echo model. The first echo model can be expressed by the following formula.

[0072]

[0073] in,

[0074] It should be noted that, in the embodiments of this application, the error compensation device can not only construct a first echo model, but also construct a second echo model, which can be constructed based on the first initial phase, the second initial phase, the propagation delay, the carrier frequency of the auxiliary satellite, and the carrier frequency of the main satellite.

[0075] Furthermore, in the embodiments of this application, when the error compensation device constructs the second echo model based on the first initial phase, the second initial phase, the propagation delay, the carrier frequency of the auxiliary satellite, and the carrier frequency of the main satellite, it can determine the fourth echo model based on the first radar signal model, the carrier frequency of the main satellite, the propagation delay, and the second initial phase; and then it can determine the second echo model based on the fourth echo model.

[0076] It should be noted that, in the embodiments of this application, the fourth echo model can be the initial echo model of the echo received by the i-th auxiliary satellite when the time deviation and frequency deviation between the ultra-stable crystal oscillator corresponding to the i-th auxiliary satellite and the ultra-stable crystal oscillator corresponding to the main satellite are both non-zero.

[0077] It should be noted that, in the embodiments of this application, the error compensation device can determine the fourth echo model, i.e. the initial echo model of the echo received by the i-th auxiliary satellite, based on the first radar signal model, the carrier frequency of the main satellite, the propagation delay, and the second initial phase. The fourth echo model can be expressed by the following formula.

[0078]

[0079] Where f1 can represent the carrier frequency of the main satellite, ε t This represents the time deviation, and f1 can be expressed by the following formula.

[0080] f1 = f i +ε f (7)

[0081] Among them, f i Let ε represent the carrier frequency of the i-th auxiliary satellite. f This indicates frequency deviation.

[0082] Furthermore, in the embodiments of this application, when the error compensation device determines the second echo model based on the fourth echo model, it can determine the second reference mixing signal model based on the fourth echo model, the first initial phase, and the carrier frequency of the auxiliary satellite; then the second reference mixing signal model can be input into the mixer and the low-pass filter to determine the second echo model.

[0083] It should be noted that, in the embodiments of this application, the error compensation device can determine the second reference mixing signal model based on the fourth echo model, the first initial phase, and the carrier frequency of the auxiliary satellite. The second reference mixing signal model can be expressed by the following formula.

[0084]

[0085] Furthermore, in the embodiments of this application, after determining the second reference mixing signal model, the error compensation device can input the second reference mixing signal model into the mixer and low-pass filter to determine the second echo model, which can be expressed by the following formula.

[0086]

[0087] in,

[0088] It should be noted that, in the embodiments of this application, after the error compensation device constructs the first echo model and the second echo model, it can determine the phase error model based on the first echo model and the second echo model.

[0089] Furthermore, in the embodiments of this application, when the error compensation device determines the phase error model based on the first echo model and the second echo model, it can first determine the first phase error model based on the first echo model and the second echo model; then it can determine the phase error model based on the first phase error model and the second phase error model.

[0090] It should be noted that, in the embodiments of this application, the error compensation device can obtain the first phase error model by subtracting the first echo model from the second echo model, that is, the first phase error model can be obtained by subtracting the above formula (5) from the above formula (9). Assuming... The first phase error model can then be expressed by the following formula.

[0091]

[0092] in, Considering only ε f The resulting phase error along the range direction.

[0093] Furthermore, in embodiments of this application, the second echo model can be ε f The resulting phase error along the azimuth direction can be expressed by the second echo model using the following formula.

[0094]

[0095] Furthermore, in the embodiments of this application, the error compensation device can determine the phase error model based on the first phase error model and the second phase error model, that is, the first phase error model and the second phase error model can be added together to obtain the phase error model, which can be expressed by the following formula.

[0096]

[0097] Where, 2π·ε f ·t a Represents ε f The resulting phase error along the azimuth direction, 2π·ε f ·t r Represents ε f The resulting phase error along the range direction, 2πε f ε t ε f and ε t The resulting phase error, Represents ε t The resulting phase error.

[0098] In other words, in the embodiments of this application, the error compensation device can determine the first echo model and the second echo model, and then determine the phase error model based on the first echo model and the second echo model. This makes it easier for the subsequent error compensation device to obtain the phase error between the main satellite and the auxiliary satellite based on the phase error model, and thus perform error compensation processing on the auxiliary satellite through the phase error.

[0099] Step 102: Determine the time deviation and frequency deviation between the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite, and determine the phase error between the main satellite and the auxiliary satellite based on the time deviation, frequency deviation and phase error model.

[0100] In the embodiments of this application, after constructing a phase error model between the main satellite and the auxiliary satellite, the error compensation device can determine the time deviation and frequency deviation between the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite, and determine the phase error between the main satellite and the auxiliary satellite based on the time deviation, frequency deviation and phase error model.

[0101] It should be noted that, in the embodiments of this application, when the error compensation device determines the time deviation and frequency deviation between the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite, it can also determine the time deviation and frequency deviation between the first ultra-stable crystal oscillator corresponding to the synthetic aperture radar (SAR) system of the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the SAR system of the main satellite.

[0102] It should be noted that, in the embodiments of this application, the error compensation device can use the second ultra-stable crystal oscillator corresponding to the main satellite as a reference, thereby obtaining the time deviation and frequency deviation between the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite.

[0103] It should be noted that, in the embodiments of this application, when the error compensation device determines the time deviation and frequency deviation between the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite, it can determine them through the Push-To-Talk (PTT) scheme or other schemes. This application does not specifically limit the method of determining the time deviation and frequency deviation.

[0104] Furthermore, in the embodiments of this application, when the error compensation device determines the phase error between the primary satellite and the secondary satellite based on the time deviation, frequency deviation, and phase error model, it can reduce the propagation delay (T) d ), distance to fast time (t) r ), range-directed modulation frequency (K r ), time deviation (ε) t ), frequency deviation (ε) f The input is fed into the phase error model to determine the phase error between the primary satellite and the secondary satellite.

[0105] Step 103: Perform error compensation processing on the auxiliary satellite based on phase error.

[0106] In the embodiments of this application, after determining the time deviation and frequency deviation between the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite, and determining the phase error between the main satellite and the auxiliary satellite based on the time deviation, frequency deviation and phase error model, the error compensation device can perform error compensation processing on the auxiliary satellite through the phase error.

[0107] Furthermore, in the embodiments of this application, when the error compensation device performs error compensation processing on the auxiliary satellite through phase error, it can compensate for the phase error included in the radar echo signal received by the auxiliary satellite through phase error, thereby obtaining the compensated echo signal.

[0108] It should be noted that, in the embodiments of this application, after the error compensation device obtains the compensated echo signal, it can determine the focused radar image based on the compensated echo signal.

[0109] Furthermore, in the embodiments of this application, Figure 5 This is a schematic diagram of the process for obtaining a focused radar image according to an embodiment of this application, as shown below. Figure 5As shown, when the error compensation device determines the focused radar image based on the compensated echo signal, it can first perform range and azimuth Fast Fourier Transform (FFT) transformations on the compensated radar echo data to obtain two-dimensional frequency domain echo data S(f r ,f η ), then S(f r ,f η ) and transfer function H R (f r, f η ,R cen Multiplying these values ​​together achieves range compression, range migration correction (RCMC), and second range compression (SRC), with the transfer function shown in the following formula.

[0110]

[0111] Where k is the wave number, R cen f is the reference center two-way slant range, f1 is the radar carrier frequency, f r f is the range-frequency axis. η Let K be the azimuth frequency axis, λ be the wavelength, and K be the frequency axis. r Here, v represents the distance-directed frequency modulation, and v represents the equivalent platform speed.

[0112] Furthermore, in the embodiments of this application, the error compensation device performs a range-direction inverse fast Fourier transform (IFFT) on the range-compressed echo data to obtain range-Doppler domain echo data S. d (t,f η ), and based on δR f (t,f η ,R cen The error of R0 on S d (t,f η Sinc interpolation is performed to achieve residual RCM compensation, δR f (t,f η ,R cen ,R0) is shown in the following formula.

[0113]

[0114] Wherein, R0 represents the target two-way slant distance.

[0115] Furthermore, in embodiments of this application, the error compensation device can compare the residual RCM-compensated radar echo data with the transfer function H. A (t,f η Multiplying the data achieves azimuth pulse compression, and performing an azimuth IFFT transform on the data yields a focused radar image. The transfer function H... A (t,f η As shown in the following formula.

[0116]

[0117] Where t represents the distance to the fast time.

[0118] It should be noted that, in the embodiments of this application, the error compensation device can perform imaging simulation based on radar system parameters and the process of steps 101 to 103. Peak sidelobe ratio (PSLR), integrated sidelobe level ratio (ISLR), and image position offset can be used as the main indicators for evaluating imaging performance. The radar system parameters are shown in Table 1 below.

[0119] Table 1

[0120]

[0121]

[0122] Furthermore, in the embodiments of this application, the error compensation device can evaluate the impact of the constant time deviation between the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite on the distributed SAR imaging results through simulation. Here, the time deviation ε between the two ultra-stable crystal oscillators is... t We can assume it to be 20ns. Figure 6 This is a schematic diagram of the simulation results presented in the embodiments of this application. Figure 1 ,like Figure 6 As shown, the point on the left represents the gradient curve of the ideal point target when the time deviation is zero, and its performance indicators are shown in Table 2 below.

[0123] Table 2

[0124]

[0125] It should be noted that, in the embodiments of this application, as... Figure 6 As shown, the point on the right represents the point target gradient curve when the time deviation is 20 ns, and its performance indicators are shown in Table 3 below.

[0126] Table 3

[0127]

[0128] It should be noted that, in the embodiments of this application, compared to a point target with zero time deviation, a 20 ns time deviation causes the point target to shift by 3.0467 m along the range direction. In an ideal situation, the time deviation ε... t At 20ns, the image will shift to the right by Δr = ε. t c / 2 = 3m, which is consistent with the simulation results.

[0129] Furthermore, in the embodiments of this application, the error compensation device can evaluate the impact of the linear time deviation between the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite on the distributed SAR imaging results through simulation. The time deviation between the two ultra-stable crystal oscillators can be expressed by the following formula.

[0130] ε t =ρ·(t) a +t r (16)

[0131] It should be noted that, in the embodiments of this application, Figure 7 This is a schematic diagram of the simulation results presented in the embodiments of this application. Figure 2 ,like Figure 7 As shown, the upper point represents the gradient curve of the point target when the time deviation is zero. The lower point represents the gradient curve of the point target when ρ = 1E-10, and its performance indicators are shown in Table 4 below.

[0132] Table 4

[0133]

[0134] It should be noted that, in the embodiments of this application, compared to an ideal point target with zero time deviation, a linear time deviation of ρ = 1E-10 causes the point target to shift by -22.025m along the azimuth direction. Ideally, ρ = 1E-10 causes the image to shift downwards by Δa = 21.74m, which is consistent with the simulation results. Furthermore, the point target exhibits defocusing along the azimuth direction, mainly because ρ affects the azimuth modulation frequency; Δa can be calculated using the following formula.

[0135]

[0136] It should be noted that, in the embodiments of this application, Figure 8 This is a schematic diagram of the simulation results presented in the embodiments of this application. Figure 3 ,like Figure 8 As shown, the upper point represents the gradient curve of the point target when the time deviation is zero. The lower point represents the gradient curve of the point target when ρ = 5E-11, and its performance indicators can be represented by Table 5 below.

[0137] Table 5

[0138]

[0139] It should be noted that in the embodiments of this application, compared with the point target with zero time deviation, the linear time deviation of ρ = 5E-11 causes the point target to shift by -10.9406m along the azimuth direction. In an ideal case, ρ = 5E-11 causes the image to shift downward by Δa = 10.87m, which is consistent with the simulation results. Δa can be calculated by the above formula (17).

[0140] Furthermore, in the embodiments of this application, the phase error that causes the azimuth position offset can be expressed by the following formula.

[0141]

[0142] Among them, K a Indicates the azimuth modulation frequency, and f a This indicates the azimuth frequency axis.

[0143] It should be noted that, in the embodiments of this application, in the distance Doppler domain, the following can be used: It compensates for the phase error of the radar echo signal, thereby offsetting the positional shift of the point target along the azimuth direction.

[0144] Furthermore, in the embodiments of this application, Figure 9 This is a schematic diagram of the simulation results presented in the embodiments of this application. Figure 4 ,like Figure 9 As shown, the ideal point target and its use The point targets after compensating for the phase error of the radar echo signal are almost identical. Compared with the ideal point target, the position deviation of the compensated point target is 0, and its performance indicators are shown in Table 6 below.

[0145] Table 6

[0146]

[0147] Furthermore, in the embodiments of this application, the error compensation device can evaluate the impact of the constant frequency deviation between the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite on the distributed SAR imaging results through simulation. The frequency deviation ε between the two ultra-stable crystal oscillators... f We can assume it to be 0.1Hz. Figure 10 This is a schematic diagram of the simulation results presented in the embodiments of this application. Figure 5 ,like Figure 10 As shown, the black dots pointed to by the arrows represent ideal point targets, while the gray dots represent point targets with frequency deviations. Compared to ideal point targets, εf =0.1Hz causes the point target to shift by -1.4395m along the azimuth direction, and its performance indicators can be represented by Table 7 below.

[0148] Table 7

[0149]

[0150] It should be noted that, in the embodiments of this application, under ideal conditions, ε f =0.1Hz causes the image to shift downward by Δa = 1.3979m and to the right by Δr = 1.2E-5m, which is consistent with the simulation results. Δa can be calculated by the following formula (19), and Δr can be calculated by the following formula (20).

[0151]

[0152]

[0153] It should be noted that, in the embodiments of this application, according to the system parameters, the position deviation of -1.4395m is less than the azimuth resolution of the radar system (approximately 4.9m). Therefore, in the design of a distributed SAR system, the constant frequency deviation has a small impact on the image position offset and can be ignored. However, the phase error caused by the frequency deviation will seriously affect the accuracy of interferometric altimetry and deformation measurement.

[0154] Furthermore, in the embodiments of this application, the error compensation device can evaluate the impact of constant time deviation, linear time deviation, and constant frequency deviation between the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite on the distributed SAR imaging results through simulation. Here, the frequency deviation ε between the two ultra-stable crystal oscillators is... f We can assume it to be 0.1Hz, and the time deviation ε t It can be expressed by the following formula.

[0155] ε t =20ns + 5E-11·(t) a +t r ) (twenty one)

[0156] It should be noted that, in the embodiments of this application, Figure 11 This is a schematic diagram of the simulation results presented in the embodiments of this application. Figure 6 ,like Figure 11 As shown, based on the time and frequency deviations described above, the imaging simulation shows that the right-side point target, which includes the time and frequency deviations, is offset by -12.3801m along the azimuth direction and 3.0467m along the range direction. Its performance indicators are shown in Table 8 below.

[0157] Table 8

[0158]

[0159] Furthermore, in the embodiments of this application, the error compensation device compensates for the radar echo signal based on the phase error determined by the phase error model. Figure 12 This is a schematic diagram of the simulation results presented in the embodiments of this application. Figure 7 ,like Figure 12 As shown, the ideal point target is almost identical to the point target after phase error compensation, and its performance indicators can be shown in Table 9 below.

[0160] Table 9

[0161]

[0162] It should be noted that, in the embodiments of this application, the positional offset of the point target in both the range and azimuth directions is zero after the error compensation device compensates for the phase error. In addition, Figure 12 The PSLR and ISLR of the point targets are almost identical to those of the ideal point targets.

[0163] It should be noted that, according to simulation results, constant time error causes image to shift along the range direction, linear time error causes image to shift along the azimuth direction and image to become out of focus, and constant frequency deviation causes image to shift along the azimuth direction and affects the accuracy of interferometric altimetry and deformation measurement. After the error compensation device performs error compensation processing on the auxiliary satellite using the phase error determined by the phase error model, the position shift of the point target in both the range and azimuth directions is zero. That is, the phase error determined by the phase error model can perform error compensation processing on the auxiliary satellite, thereby obtaining accurate echo data.

[0164] In summary, the error compensation device can determine the phase error model based on the first and second echo models. Then, based on the time deviation, frequency deviation, and phase error model, it can determine the phase error between the primary and secondary satellites. This phase error can then be used to compensate for the secondary satellite's error, thereby obtaining echo data that meets performance requirements. Furthermore, the error compensation device can also determine the focused radar image based on the compensated echo signal. Simulation experiments have verified that using the phase error determined by the phase error model to compensate for the secondary satellite's error can yield accurate echo data.

[0165] This application provides an error compensation method. The error compensation device constructs a phase error model between a primary satellite and a secondary satellite; determines the time and frequency deviations between the first ultra-stable crystal oscillator corresponding to the secondary satellite and the second ultra-stable crystal oscillator corresponding to the primary satellite; and determines the phase error between the primary and secondary satellites based on the time deviation, frequency deviation, and phase error model. Error compensation is then performed on the secondary satellite using this phase error. Therefore, the error compensation device first constructs a phase error model between the primary and secondary satellites, then determines the time and frequency deviations between the first ultra-stable crystal oscillator corresponding to the secondary satellite and the second ultra-stable crystal oscillator corresponding to the primary satellite, and then determines the phase error between the primary and secondary satellites based on these deviations. In other words, the error compensation device can construct a phase error model between the primary and secondary satellites, determine the phase error based on the model, and then perform error compensation on the secondary satellite based on this phase error, rather than directly compensating for the phase of the radar echo signal based on the time and frequency deviations. This allows for simpler, more efficient, and more accurate phase compensation of the radar echo signal, thereby improving the processing efficiency and accuracy of error compensation.

[0166] Example 2

[0167] Based on the above embodiments, another embodiment of this application provides an error compensation method. This application relates to a distributed SAR time and frequency synchronization error compensation method, which mainly includes the following three parts: (1) determining an accurate model of the phase error caused by the time and frequency deviation between ultra-stable crystal oscillators (USOs); (2) obtaining ε based on the PTT synchronization scheme. t and ε f And the phase error of the accurate model estimation in Part 1 (3) Use The phase error of the radar echo signal received by the auxiliary satellite is compensated. Finally, simulations verify that the error compensation method proposed in this application can accurately compensate for the phase error, thereby realizing high-precision measurement and mapping tasks of distributed SAR.

[0168] It should be noted that, in the embodiments of this application, when determining the accurate model of the phase error caused by the time and frequency deviation between the ultra-stable crystal oscillators (USOs) of the auxiliary satellite and the primary satellite, the error compensation device may assume that the time deviation of the USOs of the auxiliary satellite consists of constant, linear, and random errors. Due to the non-cumulative nature of random errors, the time deviation can be expressed by the following formula.

[0169] ε t =Δt c +ρ·(t a +t r ) (twenty two)

[0170] Among them, Δt c ρ is the constant time error, t is the rate of change of the linear time error. r It is the distance in the vertical direction of the flight path, and t a It is the azimuth time along the direction of the flight track.

[0171] Furthermore, in the embodiments of this application, it is assumed that the frequency deviation of the auxiliary satellite's USOs varies with time, and it can be expressed as the following formula.

[0172] ε f =∈(t) a ,t r ) (twenty three)

[0173] It should be noted that, in the embodiments of this application, for time and frequency deviations ε t and ε f The phase error contained in the radar echo signal received by the auxiliary satellite relative to the primary satellite transmitting the signal. It can be calculated using the above formula (12).

[0174] Furthermore, in the embodiments of this application, the phase error caused by time and frequency deviation... It can be calculated using the above formula, and then used... This is to compensate for the phase error of the radar echo signal received by the auxiliary satellite.

[0175] It should be noted that, in the embodiments of this application, distributed SAR is a distributed Earth observation system that places multiple transmitters and / or multiple receivers on different platforms. For example... Figure 3 As shown, the main satellite transmits radar signals to illuminate the designated target area, and multiple SAR satellites simultaneously receive the scattered echo signals.

[0176] Furthermore, in the embodiments of this application, the derivation of the phase error model can be divided into the following three steps: (1) determining the echo model with zero time and frequency error (first echo model); (2) determining the echo model with non-zero time and frequency error (second echo model); (3) determining the phase error model based on the echo model with zero time and frequency error (first echo model) and the echo model with non-zero time and frequency error (second echo model).

[0177] It should be noted that, in the embodiments of this application, the error compensation device can first determine the echo model with zero time and frequency errors, such as... Figure 4As shown, assuming the distributed SAR system consists of only two satellites, the primary satellite with clock USO1 transmits a radar signal to illuminate the target area, and this signal (the first radar signal model) can be represented by the above formula (2). Assuming the distances from the target to the primary satellite and the i-th auxiliary satellite are R1 and R2 respectively. i Then the propagation delay can be expressed as T. d T d The transmission loss is β, which can be obtained using the above formula (1). At this time, the clock is USO. i The echo signal received by the i-th auxiliary satellite (third echo model) can be represented by the above formula (3). If the time and frequency deviation between the USOs of the auxiliary satellite and the main satellite are both 0, then the reference mixing signal generated by the i-th auxiliary satellite (first reference mixing signal model) can be represented by the above formula (4). After passing through the mixer and low-pass filter, the echo received by the auxiliary satellite (first echo model) can be represented by the above formula (5).

[0178] Furthermore, in the embodiments of this application, the error compensation device can determine the echo model where the time and frequency errors are not zero. For a distributed SAR system where both time and frequency deviations are not zero, the main satellite with clock USO1 transmits a radar signal to illuminate the target area, and this signal can be described by the above formula (2). It is assumed that the time deviation between the main satellite and the i-th auxiliary satellite is ε. t The carrier frequency of the i-th auxiliary satellite is f. i Then, the echo signal received by the i-th auxiliary satellite (fourth echo model) can be represented by the above formula (6), and the reference mixing signal generated by the i-th auxiliary satellite (second reference mixing signal model) can be represented by the above formula (8). Then, the echo signal after the mixer and low-pass filter (second echo model) can be represented by the above formula (9).

[0179] Furthermore, in the embodiments of this application, after constructing the first echo model and the second echo model, the error compensation device can determine the phase error model based on the first echo model and the second echo model.

[0180] Furthermore, in the embodiments of this application, when the error compensation device determines the phase error model based on the first echo model and the second echo model, it can first determine the first phase error model based on the first echo model and the second echo model; then it can determine the phase error model based on the first phase error model and the second phase error model.

[0181] It should be noted that, in the embodiments of this application, the error compensation device can obtain the first phase error model by subtracting the first echo model from the second echo model, that is, the first phase error model can be obtained by subtracting the above formula (5) from the above formula (9). Assuming... The first phase error model can then be represented by the above formula (10).

[0182] Furthermore, in embodiments of this application, the second echo model can be ε f The resulting phase error along the azimuth direction can be represented by the second echo model using the above formula (11). The error compensation device can determine the phase error model based on the first phase error model and the second phase error model. That is, the first phase error model and the second phase error model can be added together to obtain the phase error model. The phase error model can be represented by the above formula (12).

[0183] In other words, in the embodiments of this application, the error compensation device can determine the first echo model and the second echo model, and then determine the phase error model based on the first echo model and the second echo model. This makes it easier for the subsequent error compensation device to obtain the phase error between the main satellite and the auxiliary satellite based on the phase error model, and thus perform error compensation processing on the auxiliary satellite through the phase error.

[0184] Furthermore, in the embodiments of this application, the error compensation device can perform bistatic radar imaging based on the imaging algorithm of equivalent single-base SAR. This imaging algorithm mainly includes three steps: (1) First, the compensated radar echo data can be transformed by Fast Fourier Transform (FFT) in the range and azimuth directions to obtain two-dimensional frequency domain echo data S(f r ,f η ), then S(f r ,f η ) and transfer function H R (f r, f η ,R cen (1) Multiplying the range data to achieve range compression, range migration correction (RCMC) and second range compression (SRC), the transfer function can be expressed by the above formula (13); (2) The error compensation device performs range-direction inverse fast Fourier transform (IFFT) on the range-compressed echo data to obtain the range-Doppler domain echo data S. d (t,f η ), and based on δR f (t,f η ,R cen The error of R0 on S d (t,f ηSinc interpolation is performed to achieve residual RCM compensation, δR f (t,f η ,R cen R0) is as shown in the above formula (14); (3) The error compensation device can compare the radar echo data after residual RCM compensation with the transfer function H A (t,f η Multiplying the data achieves azimuth pulse compression, and performing an azimuth IFFT transform on the data yields a focused radar image. The transfer function H... A (t,f η As shown in formula (15) above.

[0185] It should be noted that, in the embodiments of this application, the error compensation device can perform imaging simulation based on radar system parameters and the process of steps 101 to 103. Peak sidelobe ratio (PSLR), integrated sidelobe level ratio (ISLR), and image position offset can be used as the main indicators for evaluating imaging performance. The radar system parameters are shown in Table 1 above.

[0186] It should be noted that, in the embodiments of this application, the error compensation device can determine the impact of constant time deviation. First, the impact of the constant time deviation of USOs (the first ultra-stable crystal oscillator corresponding to the auxiliary satellite) on the distributed SAR imaging results is evaluated through simulation. Here, the time deviation ε between the two USOs (the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite) is... t We can assume it to be 20ns, such as Figure 6 As shown in Table 2, the left-hand point represents the gradient curve of an ideal point target with zero time deviation, and its performance indicators are shown in Table 3. The right-hand point represents the gradient curve of a point target with a time deviation of 20 ns, and its performance indicators are shown in Table 3. Compared to a point target with zero time deviation, a 20 ns time deviation causes the point target to shift by 3.0467 m along the distance direction. In the ideal case, the time deviation ε... t At 20ns, the image will shift to the right by Δr = ε. t c / 2 = 3m, which is consistent with the simulation results.

[0187] Furthermore, in the embodiments of this application, the error compensation device can determine the impact of linear time deviation. The error compensation device can evaluate the impact of the linear time deviation of USOs on the distributed SAR imaging results through simulation. Here, the time deviation between two USOs can be expressed by the above formula (16), as follows: Figure 7As shown, the upper point represents the gradient curve of the point target when the time deviation is zero. The lower point represents the gradient curve of the point target when ρ = 1E-10. Its performance indicators are shown in Table 4 above. Compared with the ideal point target with zero time deviation, the linear time deviation of ρ = 1E-10 causes the point target to shift by -22.025m along the azimuth direction. In the ideal case, ρ = 1E-10 causes the image to shift downward by Δa = 21.74m, which is consistent with the simulation results. In addition, the point target exhibits defocusing along the azimuth direction, which is mainly because ρ affects the azimuth modulation frequency. Δa can be calculated by the above formula (17), as follows: Figure 8 As shown, the upper point represents the gradient curve of the point target when the time deviation is zero. The lower point represents the gradient curve of the point target when ρ = 5E-11. Its performance index can be represented by Table 5 above. Compared with the point target with zero time deviation, the linear time deviation of ρ = 5E-11 causes the point target to shift by -10.9406m along the azimuth direction. In an ideal case, ρ = 5E-11 causes the image to shift downward by Δa = 10.87m, which is consistent with the simulation results. Δa can be calculated by the above formula (17).

[0188] Furthermore, in the embodiments of this application, the phase error that causes the azimuth position offset can be represented by the above formula (18).

[0189] It should be noted that, in the embodiments of this application, in the distance Doppler domain, the following can be used: To compensate for the phase error of the radar echo signal, and thus to offset the positional shift of the point target along the azimuth direction, such as... Figure 9 As shown, the ideal point target and its use The point targets after compensating for the phase error of the radar echo signal are almost identical. Compared with the ideal point target, the position deviation of the compensated point target is 0, and its performance indicators are shown in Table 6 above.

[0190] Furthermore, in embodiments of this application, the error compensation device can determine the impact of constant frequency deviation and evaluate the impact of the constant frequency deviation of USOs on distributed SAR imaging results through simulation. Here, the frequency deviation ε between two USOs... f We can assume it to be 0.1Hz, such as Figure 10 As shown, the black dots pointed to by the arrows represent ideal point targets, while the gray dots represent point targets with frequency deviations. Compared to ideal point targets, ε f A Hz frequency of 0.1 Hz causes the point target to shift by -1.4395 m along the azimuth direction, and its performance indicators can be represented by Table 7 above. Ideally, ε... fA Hz of 0.1 Hz will cause the image to shift downward by Δa = 1.3979 m and to the right by Δr = 1.2E-5 m, which is consistent with the simulation results. Δa can be calculated using the above formula (19), and Δr can be calculated using the above formula (20).

[0191] It should be noted that, in the embodiments of this application, according to the system parameters, the position deviation of -1.4395m is less than the azimuth resolution of the radar system (approximately 4.9m). Therefore, in the design of a distributed SAR system, the constant frequency deviation has a small impact on the image position offset and can be ignored. However, the phase error caused by the frequency deviation will seriously affect the accuracy of interferometric altimetry and deformation measurement.

[0192] Furthermore, in embodiments of this application, the error compensation device can determine the compensation for time and frequency deviations, and evaluate the impact of constant time deviation, linear time deviation, and constant frequency deviation of USOs on distributed SAR imaging results through simulation. Here, the frequency deviation ε between two USOs... f We can assume it to be 0.1Hz, and the time deviation ε t It can be expressed by the above formula (21), such as Figure 11 As shown, based on the time and frequency deviations described above, the imaging simulation shows that, compared with the ideal point target, the right-side point target, which includes time and frequency deviations, is offset by -12.3801m along the azimuth direction and 3.0467m along the range direction. Its performance indicators are shown in Table 8 above.

[0193] Furthermore, in the embodiments of this application, the error compensation device compensates the radar echo signal according to the phase error determined by the phase error model, such as... Figure 12 As shown in Table 9 above, the ideal point target and the point target after phase error compensation are almost identical. Their performance indicators are also shown in Table 9. After the phase error is compensated by the error compensation device, the point target's positional offset in both the range and azimuth directions is zero. Furthermore, Figure 12 The PSLR and ISLR of the point targets are almost identical to those of the ideal point targets.

[0194] It should be noted that, according to simulation results, constant time error causes image to shift along the range direction, linear time error causes image to shift along the azimuth direction and image to become out of focus, and constant frequency deviation causes image to shift along the azimuth direction and affects the accuracy of interferometric altimetry and deformation measurement. After the error compensation device performs error compensation processing on the auxiliary satellite using the phase error determined by the phase error model, the position shift of the point target in both the range and azimuth directions is zero. That is, the phase error determined by the phase error model can perform error compensation processing on the auxiliary satellite, thereby obtaining accurate echo data.

[0195] In summary, the error compensation device can determine the phase error model based on the first and second echo models. Then, based on the time deviation, frequency deviation, and phase error model, it can determine the phase error between the primary and secondary satellites. This phase error can then be used to compensate for the secondary satellite's error, thereby obtaining echo data that meets performance requirements. Furthermore, the error compensation device can also determine the focused radar image based on the compensated echo signal. Simulation experiments have verified that using the phase error determined by the phase error model to compensate for the secondary satellite's error can yield accurate echo data.

[0196] This application provides an error compensation method. The error compensation device constructs a phase error model between a primary satellite and a secondary satellite; determines the time and frequency deviations between the first ultra-stable crystal oscillator corresponding to the secondary satellite and the second ultra-stable crystal oscillator corresponding to the primary satellite; and determines the phase error between the primary and secondary satellites based on the time deviation, frequency deviation, and phase error model. Error compensation is then performed on the secondary satellite using this phase error. Therefore, the error compensation device first constructs a phase error model between the primary and secondary satellites, then determines the time and frequency deviations between the first ultra-stable crystal oscillator corresponding to the secondary satellite and the second ultra-stable crystal oscillator corresponding to the primary satellite, and then determines the phase error between the primary and secondary satellites based on these deviations. In other words, the error compensation device can construct a phase error model between the primary and secondary satellites, determine the phase error based on the model, and then perform error compensation on the secondary satellite based on this phase error, rather than directly compensating for the phase of the radar echo signal based on the time and frequency deviations. This allows for simpler, more efficient, and more accurate phase compensation of the radar echo signal, thereby improving the processing efficiency and accuracy of error compensation.

[0197] Example 3

[0198] Based on the above embodiments, this application provides an error compensation device. Figure 13 Schematic diagram of the composition structure of the error compensation device Figure 1 ,like Figure 13 As shown, the error compensation device 10 includes: a construction unit 11, a determination unit 12, and a processing unit 13.

[0199] The construction unit 11 is used to construct a phase error model between the main satellite and the auxiliary satellite;

[0200] The determining unit 12 is used to determine the time deviation and frequency deviation between the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite, and to determine the phase error between the main satellite and the auxiliary satellite based on the time deviation, the frequency deviation and the phase error model.

[0201] The processing unit 13 is used to perform error compensation processing on the auxiliary satellite based on the phase error.

[0202] In the embodiments of this application, further, Figure 14 Schematic diagram of the composition structure of the error compensation device Figure 2 ,like Figure 14 As shown, the error compensation device 10 proposed in this application embodiment may further include a processor 14, a memory 15 storing instructions executable by the processor 14, and further, the error compensation device 10 may further include a communication interface 16 and a bus 17 for connecting the processor 14, the memory 15 and the communication interface 16.

[0203] In the embodiments of this application, the processor 14 can be at least one of the following: Application-Specific Integrated Circuit (ASIC), Digital Signal Processor (DSP), Digital Signal Processing Device (DSPD), Programmable Logic Device (PLD), Field-Programmable Gate Array (FPGA), Central Processing Unit (CPU), Controller, Microcontroller, and Microprocessor. It is understood that for different devices, the electronic device used to implement the above-mentioned processor function can also be other types, and this application embodiment does not specifically limit this. The error compensation device 10 may further include a memory 15, which can be connected to the processor 14. The memory 15 is used to store executable program code, which includes computer operation instructions. The memory 15 may include high-speed RAM memory and may also include non-volatile memory, such as at least two disk drives.

[0204] In embodiments of this application, bus 17 is used to connect communication interface 16, processor 14, and memory 15, as well as the mutual communication between these devices.

[0205] In embodiments of this application, memory 15 is used to store instructions and data.

[0206] Furthermore, in the embodiments of this application, the processor 14 is used to construct a phase error model between the primary satellite and the secondary satellite; determine the time deviation and frequency deviation between the first ultra-stable crystal oscillator corresponding to the secondary satellite and the second ultra-stable crystal oscillator corresponding to the primary satellite; and determine the phase error between the primary satellite and the secondary satellite based on the time deviation, the frequency deviation, and the phase error model; and perform error compensation processing on the secondary satellite using the phase error.

[0207] In practical applications, the aforementioned memory 15 can be volatile memory, such as random-access memory (RAM); or non-volatile memory, such as read-only memory (ROM), flash memory, hard disk drive (HDD), or solid-state drive (SSD); or a combination of the above types of memory, and provide instructions and data to the processor 14.

[0208] This application provides an error compensation device that can construct a phase error model between a primary satellite and a secondary satellite; determine the time and frequency deviations between the first ultra-stable crystal oscillator corresponding to the secondary satellite and the second ultra-stable crystal oscillator corresponding to the primary satellite; and determine the phase error between the primary and secondary satellites based on the time deviation, frequency deviation, and phase error model; and perform error compensation processing on the secondary satellite using the phase error. Therefore, the error compensation device first constructs a phase error model between the primary and secondary satellites, then determines the time and frequency deviations between the first ultra-stable crystal oscillator corresponding to the secondary satellite and the second ultra-stable crystal oscillator corresponding to the primary satellite, and then determines the phase error between the primary and secondary satellites based on the time deviation, frequency deviation, and phase error model. In other words, the error compensation device can construct a phase error model between the primary and secondary satellites, determine the phase error based on the phase error model, and then perform error compensation processing on the secondary satellite based on this phase error, rather than directly performing phase compensation on the radar echo signal based on the time and frequency deviations. This allows for simpler, more efficient, and more accurate phase compensation of the radar echo signal, thereby improving the processing efficiency and accuracy of error compensation.

[0209] This application provides a computer-readable storage medium storing a program thereon, which, when executed by a processor, implements the error compensation method described above.

[0210] Specifically, the program instructions corresponding to an error compensation method in this embodiment can be stored on storage media such as optical discs, hard disks, and USB flash drives. When the program instructions corresponding to an error compensation method in the storage media are read or executed by an electronic device, the following steps are included:

[0211] Construct a phase error model between the primary satellite and the secondary satellite;

[0212] The time deviation and frequency deviation between the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite are determined, and the phase error between the main satellite and the auxiliary satellite is determined based on the time deviation, the frequency deviation and the phase error model;

[0213] The auxiliary satellite is subjected to error compensation processing based on the phase error.

[0214] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of hardware embodiments, software embodiments, or embodiments combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage and optical storage) containing computer-usable program code.

[0215] This application is described with reference to schematic and / or block diagrams of implementations of methods, apparatus (systems), and computer program products according to embodiments of this application. It should be understood that each block of the schematic and / or block diagrams can be implemented by computer program instructions, and combinations of blocks in the schematic and / or block diagrams can be implemented. These computer program instructions can 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 a machine for implementing the schematic and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0216] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in the implementation flow diagram. Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0217] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0218] The above description is merely a preferred embodiment of this application and is not intended to limit the scope of protection of this application.

Claims

1. An error compensation method, characterized in that, The method includes: Construct a phase error model between the primary satellite and the secondary satellite; The time deviation and frequency deviation between the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite are determined, and the phase error between the main satellite and the auxiliary satellite is determined based on the time deviation, the frequency deviation and the phase error model. The auxiliary satellite is subjected to error compensation processing based on the phase error. The construction of the phase error model between the primary satellite and the secondary satellite includes: The first echo model is constructed based on the first initial phase corresponding to the first ultra-stable crystal oscillator, the second initial phase corresponding to the second ultra-stable crystal oscillator, and the propagation delay. A second echo model is constructed based on the first initial phase, the second initial phase, the propagation delay, the carrier frequency of the auxiliary satellite, and the carrier frequency of the primary satellite. The phase error model is determined based on the first echo model and the second echo model.

2. The method according to claim 1, characterized in that, The method further includes: The propagation delay is determined by the distance parameters of the primary satellite and the secondary satellite.

3. The method according to claim 1, characterized in that, Determining the phase error model based on the first echo model and the second echo model includes: The first phase error model is determined based on the first echo model and the second echo model; The phase error model is determined based on the first phase error model and the second phase error model.

4. The method according to claim 1, characterized in that, The construction of the first echo model based on the first initial phase corresponding to the first ultrastable crystal oscillator, the second initial phase corresponding to the second ultrastable crystal oscillator, and the propagation delay includes: The model of the first radar signal transmitted by the main satellite is determined based on the second initial phase; The third echo model is determined based on the first radar signal model and the propagation delay. The first echo model is determined based on the first initial phase and the third echo model.

5. The method according to claim 4, characterized in that, Determining the first echo model based on the first initial phase and the third echo model includes: The first reference mixing signal model is determined based on the first initial phase and the third echo model. The first reference mixing signal model is input into the mixer and low-pass filter to determine the first echo model.

6. The method according to claim 4, characterized in that, The step of constructing the second echo model based on the first initial phase, the second initial phase, the propagation delay, the carrier frequency of the auxiliary satellite, and the carrier frequency of the primary satellite includes: The fourth echo model is determined based on the first radar signal model, the carrier frequency of the main satellite, the propagation delay, and the second initial phase. The second echo model is determined based on the fourth echo model.

7. The method according to claim 6, characterized in that, Determining the second echo model based on the fourth echo model includes: The second reference mixing signal model is determined based on the fourth echo model, the first initial phase, and the carrier frequency of the auxiliary satellite; The second reference mixing signal model is input into the mixer and low-pass filter to determine the second echo model.

8. The method according to claim 2, characterized in that, Determining the phase error between the primary satellite and the secondary satellite based on the time deviation, the frequency deviation, and the phase error model includes: The propagation delay, range fast time, range azimuth frequency, time deviation, and frequency deviation are input into the phase error model to determine the phase error between the primary satellite and the secondary satellite.

9. The method according to claim 1, characterized in that, The step of performing error compensation processing on the auxiliary satellite based on the phase error includes: The phase error is compensated for by the phase error of the radar echo signal received by the auxiliary satellite, and the compensated echo signal is obtained.

10. The method according to claim 9, characterized in that, After obtaining the compensated echo signal, the method further includes: The focused radar image is determined based on the compensated echo signal.

11. The method according to claim 1, characterized in that, The determination of the time and frequency deviations between the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite includes: The time deviation and frequency deviation between the first ultra-stable crystal oscillator corresponding to the synthetic aperture radar (SAR) system of the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the SAR system of the main satellite are determined.

12. An error compensation device, characterized in that, The error compensation device includes: a construction unit and a determination unit. Processing unit The construction unit is used to construct a phase error model between the main satellite and the auxiliary satellite; The determining unit is used to determine the time deviation and frequency deviation between the first ultra-stable crystal oscillator corresponding to the auxiliary satellite and the second ultra-stable crystal oscillator corresponding to the main satellite, and to determine the phase error between the main satellite and the auxiliary satellite based on the time deviation, the frequency deviation and the phase error model. The processing unit is used to perform error compensation processing on the auxiliary satellite based on the phase error; wherein, the construction of the phase error model between the primary satellite and the auxiliary satellite includes: constructing a first echo model based on the first initial phase corresponding to the first ultra-stable crystal oscillator, the second initial phase corresponding to the second ultra-stable crystal oscillator, and the propagation delay; constructing a second echo model based on the first initial phase, the second initial phase, the propagation delay, the carrier frequency of the auxiliary satellite, and the carrier frequency of the primary satellite; and determining the phase error model based on the first echo model and the second echo model.

13. An error compensation device, characterized in that, The error compensation device includes: a processor and a memory; wherein... The memory is used to store computer programs that can run on the processor; The processor is configured to perform the method as described in any one of claims 1-11 when running the computer program.

14. A computer-readable storage medium, characterized in that, The storage medium stores computer program code, which, when executed by a computer, performs the method described in any one of claims 1-11.

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