Frequency modulated thermal wave imaging for visualizing power density of electromagnetic waves on plane surfaces
01 Mar 2019-Research in Nondestructive Evaluation (The American Society for Nondestructive Testing)-Vol. 30, Iss: 2, pp 65-79
TL;DR: In this paper, a frequency modulated thermal wave imaging (FMTWI) was introduced for the first time for determining power distribution of electromagnetic waves on plane surfaces, which can extract multiple amplitude and phase images from a single run of experiment and can be used qualitatively to detect field leakage near electromagnetic junctions and microstrip feed lines.
Abstract: In this article, Frequency Modulated Thermal Wave Imaging (FMTWI) [1–6] is introduced for the first time for determining power distribution of electromagnetic waves on plane surfaces. The advantage with this technique is that we can extract multiple amplitude and phase images from a single run of experiment. The applied excitation signal in this technique is a frequency modulated chirp signal instead of a single frequency signal used in conventional lock-in infrared (IR) thermography [7–11].The thermal images obtained using FMTWI can be used qualitatively, e.g., to detect field leakage near electromagnetic junctions and microstrip feed lines. As a practical demonstration of this technique, an example of 2 × 2 patch antenna array at 8 GHz is considered. First, amplitude images at various modulation frequencies are obtained. Next, signal to noise ratio (SNR) values at each frequency are calculated. It is seen that SNR is lower at higher frequencies. It is observed that at higher modulation frequenci...
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TL;DR: In this article , a hybrid breast cancer detection modality consisting of microwaves as a radiation source and an infrared thermography method as a heat-imaging recorder, supported by a Convolution Neural Network (CNN), is proposed.
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References
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01 Jul 1984
5,335 citations
"Frequency modulated thermal wave im..." refers methods in this paper
...Dimensions of the individual patch antennas are calculated using the basic patch antenna design equations [18]....
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01 Jan 1966
TL;DR: In this article, two-and three-dimensional boundary value problems are studied for two-dimensional waveguides with Cylindrical Conducting Boundaries (CCLB).
Abstract: Stationary Electric Fields. Stationary Magnetic Fields. Maxwell's Equations. The Electromagnetics of Circuits. Transmission Lines. Plane-Wave Propagation and Reflection. Two- and Three-Dimensional Boundary Value Problems. Waveguides with Cylindrical Conducting Boundaries. Special Waveguide Types. Resonant Cavities. Microwave Networks. Radiation. Electromagnetic Properties of Materials. Optics. Appendices. Index.
2,852 citations
"Frequency modulated thermal wave im..." refers methods in this paper
...From this model, the reflection, transmission, and absorption coefficients are calculated using standard text book definitions [17], as follows: (A)....
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TL;DR: In this paper, the authors provided the theory and mathematical analysis in support of a recently proposed frequency modulated thermal wave imaging for nondestructive subsurface defect detection in solids.
Abstract: This letter provides the theory and mathematical analysis in support of a recently proposed frequency modulated thermal wave imaging for nondestructive subsurface defect detection in solids. The authors illustrate how the technique simultaneously combines the advantages of both conventional pulse based thermography as well as modulated lock-in thermography. A specimen is heated for launching thermal waves into the sample, not at a single frequency (lock-in) or at all frequencies (pulse), but in a desired range of frequencies. While peak power requirement is reduced, phase images obtained retain known advantages. Experimental results from a carbon fiber reinforced plastic sample are presented in support.
250 citations
TL;DR: Pulsed, lock-in and frequency modulated thermography are three alternative nondestructive evaluation techniques. as discussed by the authors compared the defect imaging performance of these techniques using: matched excitation energy; the same carbon fiber composite test piece and infrared camera system.
Abstract: Pulsed, lock-in and frequency modulated thermography are three alternative nondestructive evaluation techniques. The defect imaging performance of these techniques are compared using: matched excitation energy; the same carbon fiber composite test piece and infrared camera system. The lock-in technique suffers from “blind frequencies” at which phase images for some defects disappear. It is shown that this problem can be overcome by using frequency modulated (chirp) excitation and an image fusion algorithm is presented that enhance phase imaging of defects. The signal-to-noise ratios (SNRs) of defect images obtained by the three techniques are presented. For the shallowest defects (depths 0.25 and 0.5 mm, 6 mm diameter), the pulsed technique exhibits the highest SNRs. For deeper defects the SNRs of the three techniques are similar in magnitude under matched excitation energy condition.
144 citations
TL;DR: In this paper, it was shown that a thin film of contaminant on a microwave window may absorb up to 50% of the incident power, even if the film thickness is only a small fraction of its resistive skin depth.
Abstract: With the use of a simple model, it is shown that a thin film of contaminant on a microwave window may absorb up to 50% of the incident power, even if the film thickness is only a small fraction of its resistive skin depth. This unexpectedly large amount of absorption is conjectured to have played a significant role in window failure. The temperature rise in a thin film is estimated.
105 citations