STWE SAR Elevation Echo Separation via Digital Beam Nulling
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Solution Overview
Problem
Spaceborne Synthetic Aperture Radar (SAR) systems face challenges in separating temporally overlapping echo signals from sub-swaths, which affects system performance due to signal overlap and requires effective echo signal separation to maintain high-resolution wide-swath imaging capabilities.
Innovation Solution
The method involves generating multiple sub-beams with specific null directions to suppress interference echoes and process aliasing echo signals using a multipath beam former, allowing for deep nulling suppression and effective extraction of target echo signals, thereby reducing pulse extension loss and improving signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If echoes of multiple sub-swaths are made to overlap in time to reduce echo window length and onboard data volume, then system design flexibility and data storage requirements are improved, but echo signal separation becomes more difficult and system performance deteriorates
Solution Approach 1:
The patent segments the overlapping echo signals from different sub-swaths into separate signal components using digital beam forming. By applying different beam forming weights to signals from different receiving antennas, the system can separate and extract echo signals from specific sub-swaths even when they overlap in time, thus resolving the contradiction between reduced data storage needs and maintained signal separation performance.
Solution Approach 2:
The patent changes the spatial parameters of signal reception by adjusting beam forming weights and null depths for different sub-swaths. By dynamically adjusting these parameters, the system can selectively enhance or suppress echoes from different sub-swaths, enabling effective signal separation despite temporal overlap and maintaining high echo separation performance while using reduced onboard storage.
2Measurement precision
If deep nulling suppression is applied to suppress interference echoes from other sub-swaths, then echo signal separation efficiency is improved, but system complexity increases due to multiple sub-beam generation and processing
Solution Approach 1:
The patent implements a universal digital beam forming processor that can handle multiple sub-swaths simultaneously using the same hardware and software platform. The system uses a unified set of receiving antennas and signal processing channels that can be configured through software to process different sub-swaths and apply appropriate beam forming weights and null depths, thereby achieving high echo separation efficiency without proportionally increasing hardware complexity.
Solution Approach 2:
The patent transitions from time-domain signal processing to spatial-domain processing by introducing a third dimension of beam forming control. Instead of simply filtering overlapping signals in time, the system adds spatial selectivity through beam forming weights and null depths associated with different antenna elements and directions, enabling effective separation of overlapping echoes while managing complexity through software-based spatial filtering.
3Measurement precision
If multiple sub-beams with nulls are generated for each target sub-swath to achieve deep nulling suppression, then signal-to-noise ratio is improved, but computational load and processing time increase
Solution Approach 1:
The patent performs preliminary calculation and storage of beam forming weights and null depth parameters for each sub-swath before actual signal processing. By pre-computing these optimization parameters based on known sub-swath geometries and expected echo characteristics, the system reduces the real-time computational burden during actual echo separation, thereby maintaining high signal-to-noise ratio while improving processing speed and productivity.
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 enhances echo signal separation efficiency, increases signal-to-noise ratio, and simplifies onboard processing, enabling real-time echo separation and Digital Beam Forming synthesis, while reducing system complexity.
Implementation Method 1
For a target sub-swath of the multiple sub-swaths, multiple sub-beams associated with the target sub-swath are generated. The multiple sub-beams point to different directions of the target sub-swath respectively
Implementation Method 2
a null of each of the multiple sub-beams is used for deep nulling suppression on echo signals of sub-swaths except the target sub-swath
Data Source
AI summary
A method and a device for separating echo signals of STWE SAR in elevation are provided. The method includes that: aliasing echo signals of multiple sub-swaths are received; for a target sub-swath of the multiple sub-swaths, multiple sub-beams associated with the target sub-swath are generated, the multiple sub-beams pointing to different directions of the target sub-swath respectively, and a null of each of the multiple sub-beams being used for deep nulling suppression on echo signals of sub-swaths except the target sub-swath; and the aliasing echo signals are processed based on the multiple sub-beams and multiple nulls corresponding to the multiple sub-beams to generate a target echo signal of the target sub-swath.