Split-Swath SAR Feed Layout for Contiguous Wide-Swath Imaging
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Solution Overview
Problem
Conventional synthetic aperture radar systems face challenges in achieving large range swaths due to limitations in radar reception time windows and the use of expensive phased array antennas, particularly for smaller antennas that struggle to form narrow beams to suppress ambiguous radar returns.
Innovation Solution
The multi-channel split swath (MCSS) SAR system employs a satellite platform with a parabolic reflector and separate antenna feeds that form multiple beams using frequency-separated chirp pulses, alternating between horizontal and vertical polarizations, to illuminate and receive returns from multiple subswaths in a time-multiplexed manner, utilizing different pulse repetition frequencies for each set of antenna feeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a conventional single feed scan mode radar system is used, then the system structure is simple, but the range swath length is limited by the radar reception time window
Solution Approach 1:
The invention divides the single antenna feed into multiple feeds (first set and second set), each capable of forming separate beams. This segmentation allows simultaneous illumination of multiple subswaths, extending the total range swath length beyond what a single feed could achieve while maintaining manageable system complexity through modular feed design
2Area of stationary object
If phased array antennas are used to electronically steer RF beams, then the SAR coverage area increases, but the manufacturing cost and complexity increase significantly
Solution Approach 1:
The invention uses multiple simple feed elements that replicate the basic feed structure, each forming a beam in a different direction. This approach achieves electronic beam steering functionality through geometric arrangement rather than complex phased array electronics, significantly reducing manufacturing cost while maintaining expanded coverage area
Solution Approach 2:
The invention replaces expensive phased array antenna elements with simpler, more economical feed structures. These simplified feeds achieve the necessary beam forming capability through geometric positioning and basic RF components, making the system more cost-effective while maintaining the ability to cover large SAR areas
3Area of moving object
If a smaller antenna is used, then the system size is reduced, but the antenna cannot form narrow enough beams to suppress radar returns from ambiguous ranges
Solution Approach 1:
The invention segments the illumination function across multiple feeds, each responsible for a specific subswath. This allows a smaller antenna to achieve effective narrow beam coverage for each subswath by dedicating individual feeds to specific angular sectors, maintaining range resolution precision while keeping the overall antenna aperture compact
4Area of stationary object
If multiple antenna feeds are used to illuminate multiple subswaths, then the swath coverage is extended, but the system complexity increases
Solution Approach 1:
The invention segments the total swath into multiple subswaths, each illuminated by a dedicated feed or group of feeds. This segmentation allows the system to manage complexity by dividing the coverage area into manageable sectors, where each feed handles a specific portion, making the overall system more tractable while achieving extended swath coverage
Solution Approach 2:
The invention employs time-multiplexed operation where different sets of feeds are activated in alternating time periods. This periodic activation pattern allows the system to illuminate multiple subswaths sequentially with different feed configurations, achieving extended swath coverage while managing system complexity through time-division multiplexing rather than requiring all feeds to operate simultaneously
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 allows for extended swath coverage by filling in gaps between subswaths, enabling efficient and cost-effective imaging of large areas without the need for expensive phased array antennas, while maintaining high resolution and reducing ambiguity.
Implementation Method 1
a parabolic reflector and separate antenna feeds that form multiple beams using frequency-separated chirp pulses
Implementation Method 2
synthetic aperture radar (SAR) is highly effective for remote sensing using active microwave transmissions
Implementation Method 3
alternating between horizontal and vertical polarizations
Implementation Method 4
receive returns/reflections of the concurrent radar pulses from the swath
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A synthetic aperture radar (SAR) generates concurrent first radar pulses in first frequency channels. The SAR transmits, and receives returns of, the concurrent first radar pulses by first antenna feeds that form first beams in the first frequency channels and that are directed to respective first subswaths of a swath on the Earth separated by subswath gaps. The SAR generates concurrent second radar pulses in second frequency channels. The SAR transmits, and receives returns of, the concurrent second radar pulses by second antenna feeds configured to form second beams in the second frequency channels and that are directed to respective second subswaths of the swath on the Earth and that coincide with the subswath gaps. The SAR processes the returns of the first radar pulses from the first subswaths and the returns of the second radar pulses from the second subswaths to form a SAR image contiguous across the swath.