Phase Confocal Near-Field Microwave Imaging in Dispersive Media
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Solution Overview
Problem
Conventional RADAR-based microwave imaging methods assume uniform wave propagation speed across all frequency components in ultra-wideband signals, leading to inaccurate flight time estimation and degraded image quality, especially in dispersive media like human tissue or soil.
Innovation Solution
The phase confocal method processes signals in the frequency domain, calculating phase delays instead of time delays to compensate for phase shifts at each frequency, allowing for accurate image reconstruction using phase and amplitude information, and enabling full utilization of the ultra-wideband spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional RADAR-based methods calculate time delay assuming uniform wave propagation speed across all frequency components, then the processing is simple and fast, but the flight time estimation becomes inaccurate and image quality degrades in dispersive media
Solution Approach 1:
The patent segments the ultra-wideband signal into multiple frequency components and processes each frequency component separately in the frequency domain. This allows calculation of phase delay specific to each frequency, accounting for dispersive medium effects, rather than treating all frequencies uniformly as in conventional time-domain methods.
Solution Approach 2:
The patent substitutes time-domain mechanical signal processing with frequency-domain phase analysis. Instead of calculating time delays based on assumed uniform propagation speed, the method uses phase delay calculations at each frequency component, which naturally accounts for frequency-dependent propagation characteristics in dispersive media.
2Ease of manufacture
If conventional methods treat all frequency components as traveling together with the same speed, then the calculation is simplified, but the approximation leads to inaccurate flight time estimation
Solution Approach 1:
The patent divides the broadband signal into multiple frequency components and processes each frequency component individually in the frequency domain. This segmentation allows accurate calculation of phase delay for each frequency, recognizing that different frequencies travel at different speeds in dispersive media, thereby improving flight time estimation accuracy.
Solution Approach 2:
The patent changes the processing parameter from time delay (assumed uniform across frequencies) to phase delay (frequency-specific). By working in the frequency domain and calculating phase delay at each frequency component, the method adapts to the frequency-dependent propagation characteristics of dispersive media, improving accuracy without excessive complexity.
3Measurement precision
If phase confocal method processes each frequency individually in the frequency domain, then accurate delay estimation is achieved, but the processing complexity increases
Solution Approach 1:
The patent replaces complex time-domain signal processing with frequency-domain phase analysis. By using the relationship between phase and frequency, the method achieves accurate delay estimation through phase delay calculations, which are mathematically equivalent to time delay but better suited for dispersive media and can be implemented efficiently using standard frequency domain techniques.
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 provides high-resolution imaging by accurately estimating the contribution of multiple frequency components, improving image quality and localization accuracy in dispersive media without requiring complex antenna gain pattern compensation or additional calibration steps.
Implementation Method 1
the present inventive concepts calculate a phase delay (or a phase shift) in the frequency-space domain
Implementation Method 2
measuring an electromagnetic scattered field
Implementation Method 3
components of different frequencies in the UWB signal spectrum will take different paths across the air-medium interface and propagate at different speeds in the medium
Data Source
AI summary
An efficient RADAR imaging method that is able to detect an object within an interested area. This method uses electromagnetic waves transmitted by one or many transmitters to illuminate the interested area, and then estimates the phase shift of the scattered wave of an object according to the path that the electromagnetic wave propagated. By reversing the phase of the obtained scattered signal to the transmitters' position, an image is constructed for the entire interested area according to the correlation of signals in all channels. The present method works in the frequency domain. It produces a microwave image by using the phase and magnitude of the obtained signal, or using the phase information only. Other unique features include the way it synthesizes the signals obtained in multiple channels and at multiple frequencies. Its overwhelming high efficiency makes rapid microwave imaging and real-time imaging possible.