SAR Phase Error Correction via Differential Processing
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Solution Overview
Problem
Bistatic and multistatic SAR systems face challenges in synchronizing time and phase references due to the use of different oscillators, leading to phase noise and inaccurate data calibration, which affects interferometric and tomographic applications.
Innovation Solution
A method that estimates and corrects residual clock phase errors in non-synchronous SAR data by processing differential phase data between channels, allowing for synchronization without additional hardware and improving phase synchronization accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different oscillators are used in transmitter and receiver for bistatic/multistatic SAR systems, then system flexibility and scalability are improved, but phase synchronization accuracy deteriorates due to clock phase errors
Solution Approach 1:
The patent introduces an intermediary processing step that uses differential phase data from multiple channels as a mediator to estimate and correct clock phase errors. The differential phase data serves as an intermediate measurement that bridges the transmitter and receiver oscillators, allowing synchronization without direct hardware connection.
Solution Approach 2:
The patent implements a feedback mechanism where the estimated clock phase errors are fed back to correct the SAR data. The correction process uses the differential phase information to generate corrective adjustments that are applied to synchronize the time and phase references between transmitter and receiver.
2Measurement precision
If additional synchronization hardware is added to bistatic/multistatic SAR systems, then phase synchronization accuracy is improved, but device complexity increases
Solution Approach 1:
The patent enables the SAR system to self-correct its synchronization errors by using its own existing multi-channel data. The differential phase data from the multiple receive channels is processed to estimate and correct the clock phase errors without requiring external synchronization hardware or additional equipment.
Solution Approach 2:
The patent replaces the mechanical/hardware-based synchronization approach with a signal-processing-based approach. Instead of using additional oscillators, phase-locked loops, or hardware synchronization circuits, the invention uses mathematical processing of the SAR signal data itself to achieve synchronization.
3Ease of operation
If clock phase errors are not corrected in non-synchronous SAR data, then data acquisition simplicity is maintained, but interferometric and tomographic application quality deteriorates
Solution Approach 1:
The patent performs preliminary correction of clock phase errors during the data processing stage before the actual SAR image formation and interferometric analysis. By estimating and correcting the phase errors in advance using the differential phase data from multiple channels, the system ensures high-quality results in subsequent applications without adding complexity to the data acquisition process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables accurate time and phase correction in bistatic and multistatic SAR systems, reducing phase noise and enhancing the quality of SAR images, particularly in applications like digital elevation modeling and interferometry.
Implementation Method 1
Due to the well-known Doppler effect, phase modulation occurs during the recording of the radar echo
Implementation Method 2
Due to the well-known Doppler effect, phase modulation occurs during the recording of the radar echo
Data Source
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Figure 2
Figure 3~4
AI summary
The invention describes a method for estimating and correcting the time and phase references of non-synchronous SAR data. The non-synchronous SAR data are acquired and provided by a bistatic or multistatic multi-channel radar system with N channels. In the method according to the invention, a residual clock phase error (δf̂ij[na]) present within the SAR data is estimated and corrected based on an evaluation, in particular an exclusive evaluation, of information from the SAR data. The method according to the invention is characterized in that, for estimating the residual clock phase error (δf̂ij[na]), differential phase data between one or more pairs of channels (CHi, CHj) of the multi-channel radar system are processed, which are sampled at different times in a receiver (60) of the multi-channel radar system.Furthermore, a correction of the time and phase references of the received SAR data is performed by processing the estimated residual clock phase error (δf̂ij[na]).