Radially-Polarized Probe for Orientation-Independent Microwave Imaging
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Solution Overview
Problem
Microwave and millimeter wave imaging technologies face challenges in detecting targets like cracks and sharp edges independently of their orientation due to the sensitivity of existing probes to polarized targets, which requires complex calibration and is unsuitable for non-flat surfaces, especially in far-field imaging.
Innovation Solution
A radially-polarized probe is used for microwave and millimeter wave imaging, transmitting a signal with a polarization orientation independent of the target's orientation, allowing detection using a single-channel measurement system and maintaining constant intensity in the target image regardless of orientation, suitable for both far-field and near-field modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a linearly-polarized probe is used for imaging, then the probe can provide high sensitivity to targets with specific orientations, but the detection capability deteriorates when target orientation is unknown or varies
Solution Approach 1:
The patent employs a radially-polarized probe that dynamically changes its polarization orientation as it scans across the sample. The probe's polarization direction rotates to remain orthogonal to the scan direction, allowing it to maintain optimal detection sensitivity for targets of any fixed orientation on the sample surface.
Solution Approach 2:
The invention changes the polarization parameter of the electromagnetic field from fixed linear polarization to radial polarization. This parameter change enables the field to adapt its orientation relative to targets, providing detection capability independent of target orientation while maintaining high sensitivity.
2Adaptability or versatility
If a dual-polarized probe is used to detect arbitrarily oriented targets, then orientation independence is achieved, but the system complexity and calibration requirements increase significantly
Solution Approach 1:
Instead of using a static dual-polarized probe that requires two independent measurement channels, the invention uses a single radially-polarized probe whose polarization dynamically adapts during scanning. This dynamic approach achieves orientation independence with a simpler single-channel measurement system.
Solution Approach 2:
The radially-polarized probe performs the function of both horizontal and vertical linearly-polarized probes simultaneously by rotating its polarization orientation during the scan, eliminating the need for separate measurement channels and complex calibration procedures.
3Measurement precision
If near-field imaging is performed with a linearly-polarized probe, then high sensitivity to small targets is achieved, but the system becomes very sensitive to variations in standoff distance
Solution Approach 1:
The invention changes the polarization parameter from linear to radial, which fundamentally alters the interaction with targets. The radially-polarized field maintains high sensitivity to small targets while reducing sensitivity to standoff distance variations because the polarization orientation adapts to maintain orthogonality with the scan direction regardless of distance.
4Adaptability or versatility
If far-field imaging is performed with spreading radiated waves, then imaging of non-flat areas becomes feasible, but SAR focusing algorithms become necessary to maintain image resolution
Solution Approach 1:
By changing from linear to radial polarization, the patent modifies the electromagnetic field characteristics to maintain consistent intensity in the target image regardless of target orientation. This parameter change works synergistically with far-field imaging to provide orientation-independent detection without requiring complex post-processing algorithms.
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
The radially-polarized probe enables detection of arbitrarily oriented targets with consistent image intensity, improving detection accuracy and applicability to non-flat surfaces without the need for complex calibration, using frequencies ranging from 18 to 26.5 GHz.
Implementation Method 1
The probe transmits the imaging signal having a radially-polarized pattern with an orientation independent of an orientation of a target in the sample
Implementation Method 2
receive any scattered signal resulting from any targets in the imaging area
Data Source
AI summary
A microwave and millimeter wave imaging system. In either a far-field or a near-field detection mode, a radially-polarized probe transmits an imaging signal along a predetermined scan path to detect a target in a sample. The imaging signal's orientation is independent of the target's orientation and changes at each target as the probe transmits the signal during scanning. A measurement system receives scattered waves reflected from the sample via a single channel and images the sample and the target based on the reflected waves independent of the orientation of the target.