Interferometric ISAR Height Measurement via Antenna Segmentation
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Solution Overview
Problem
Current synthetic aperture radar systems, particularly inverse synthetic aperture radar, face limitations in generating three-dimensional images of moving targets, especially in maritime surveillance where target movement due to wave action complicates image formation.
Innovation Solution
The implementation of an interferometric inverse synthetic aperture radar (IFISAR) system that utilizes two or more antennas to capture phase differences in radar returns, combining platform and target motion to provide a three-dimensional image by measuring height features through interferometric processing, allowing for a small airborne radar aperture to generate a three-dimensional image in a single-pass frame of data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional SAR or ISAR processing is used, then two-dimensional images can be generated, but three-dimensional imaging capability is lost
Solution Approach 1:
The patent applies interferometric processing to phase differences between signals received by multiple antennas to extract height information, effectively adding a vertical dimension to the traditional two-dimensional SAR/ISAR imaging. This transforms the imaging capability from 2D to 3D by utilizing the phase dimension of the radar signals.
Solution Approach 2:
The patent divides the phased array antenna into multiple sub-apertures, each capable of independent signal reception. This segmentation allows the system to process signals from different spatial positions separately and combine them through interferometric processing to achieve three-dimensional imaging.
2Productivity
If a small airborne radar aperture is used, then platform mobility is improved, but image formation quality deteriorates due to target movement
Solution Approach 1:
The patent performs motion compensation and interferometric processing in advance during the signal processing stage, before final image generation. This preliminary action corrects for target movement effects and establishes the three-dimensional information needed for accurate height measurement.
Solution Approach 2:
The patent creates multiple virtual views of the target by processing signals from different sub-apertures and combining them through interferometric processing. This copying approach allows the small physical aperture to effectively simulate multiple observation angles and achieve accurate three-dimensional imaging.
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
Enables the creation of accurate three-dimensional images of moving targets, enhancing maritime surveillance capabilities by providing precise height measurements and vertical characteristics using phase differences between radar returns from spaced antennas.
Implementation Method 1
A synthetic aperture radar (SAR) generates an image of a target by processing separate radar returns from a number of sequentially transmitted pulses from an antenna
Implementation Method 2
The azimuth or height information is then obtained from the phase differences of corresponding pixels in different ISAR images
Data Source
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AI summary
An interferometric inverse synthetic aperture radar (IFISAR) is described that can provide a height measurement of moving objects on a surface using a small radar aperture. The IFISAR includes a two-dimensional antenna array including a plurality of elements that are configured to receive a plurality of return signals carrying energy of a transmitted RF signal that are reflected from the target. A first antenna group and a second antenna group of the plurality of elements respectively located at opposite ends of the array are enabled, and a third antenna group of the plurality of elements located between the first antenna group and the second antenna group are disabled. A processor of the IFISAR is operatively coupled to the plurality of elements and configured to determine height characteristics of the target according to interferometric processing of the return signals received by the first antenna group and the second antenna group.