skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • Fourier-Space Image Reconstruction Using Microwave Measurements: The Path Toward Real-Time Microwave and Millimeter-Wave Imaging
Title: Fourier-Space Image Reconstruction Using Microwave Measurements: The Path Toward Real-Time Microwave and Millimeter-Wave Imaging
The use of electromagnetic waves at microwave and millimeter-wave (mm-wave) frequencies in imaging has been growing rapidly in the last two decades with applications in security screening, biomedical imaging, nondestructive testing, and the inspection of goods and packages. The nonionizing nature of the radiation renders microwave and mm-wave imaging (MMI) safe for humans and, thus, attractive, especially for frequent imaging of living tissue and humans. At the same time, the radiation penetrates many materials, which are optically opaque: e.g., fog and foliage, soil and living tissue, brick and drywall, wood, fabrics, and plastics. Importantly, modern MMI systems offer compact and relatively low-cost hardware due to advancements in high-frequency microelectronics.  more » « less
Award ID(s):
1920098
PAR ID:
10531977
Author(s) / Creator(s):
;
Publisher / Repository:
IEEE Microwave Magazine
Date Published:
Journal Name:
IEEE Microwave Magazine
Volume:
25
Issue:
8
ISSN:
1527-3342
Page Range / eLocation ID:
36 to 56
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; (, Sensors)
    This paper presents the design, simulation and experimental validation of a gradient-index (GRIN) metasurface lens operating at 8 GHz for microwave imaging applications. The unit cell of the metasurface consists of an electric-LC (ELC) resonator. The effective refractive index of the metasurface is controlled by varying the capacitive gap at the center of the unit cell. This allows the design of a gradient index surface. A one-dimensional gradient index lens is designed and tested at first to describe the operational principle of such lenses. The design methodology is extended to a 2D gradient index lens for its potential application as a microwave imaging device. The metasurface lenses are designed and analyzed using full-wave finite element (FEM) solver. The proposed 2D lens has an aperture of size 119 mm (3.17λ) × 119 mm (3.17λ) and thickness of only 0.6 mm (0.016λ). Horn antenna is used as source of plane waves incident on the lens to evaluate the focusing performance. Field distributions of the theoretical designs and fabricated lenses are analyzed and are shown to be in good agreement. A microwave nondestructive evaluation (NDE) experiment is performed with the 2D prototype lens to image a machined groove in a Teflon sample placed at the focal plane of the lens. 
    more » « less
  2. ; ; (, Sensors)
    A compact and planar imaging system was developed using a flexible polymer substrate that can distinguish subcutaneous tissue abnormalities, such as breast tumors, based on electromagnetic-wave interactions in materials where permittivity variations affect wave reflection. The sensing element is a tuned loop resonator operating in the industrial, scientific, and medical (ISM) band at 2.423 GHz, providing a localized high-intensity electric field that penetrates into tissues with sufficient spatial and spectral resolutions. The resonant frequency shifts and magnitudes of the reflection coefficients indicate the boundaries of abnormal tissues under the skin due to their high contrasts to normal tissues. The sensor was tuned to the desired resonant frequency with a reflection coefficient of −68.8 dB for a radius of 5.7 mm, with a tuning pad. Quality factors of 173.1 and 34.4 were achieved in simulations and measurements in phantoms. An image-processing method was introduced to fuse raster-scanned 9 × 9 images of resonant frequencies and reflection coefficients for image-contrast enhancement. The results showed a clear indication of the tumor’s location at a depth of 15 mm and the capability to identify two tumors both at the depth of 10 mm. The sensing element can be expanded to a four-element phased array for deeper field penetration. Field analysis showed the depths of −20 dB attenuation were improved from 19 to 42 mm, giving wider coverage in tissues at resonance. Results showed that a quality factor of 152.5 was achieved and a tumor could be identified at a depth of up to 50 mm. In this work, simulations and measurements were conducted to validate the concept, showing great potential for subcutaneous imaging in medical applications in a noninvasive, efficient, and lower-cost way. 
    more » « less
  3. ; ; (, Annual Review of Materials Research)
    Understanding the nanoscale electrodynamic properties of a material at microwave frequencies is of great interest for materials science, condensed matter physics, device engineering, and biology. With specialized probes, sensitive detection electronics, and improved scanning platforms, microwave microscopy has become an important tool for cutting-edge materials research in the past decade. In this article, we review the basic components and data interpretation of microwave imaging and its broad range of applications. In addition to the general-purpose mapping of permittivity and conductivity, microwave microscopy is now exploited to perform quantitative measurements on semiconductor devices, photosensitive materials, ferroelectric domains and domain walls, and acoustic-wave systems. Implementation of the technique in low-temperature and high-magnetic-field chambers has also led to major discoveries in quantum materials with strong correlation and topological order. We conclude the review with an outlook of the ultimate resolution, operation frequency, and future industrial and academic applications of near-field microwave microscopy. Expected final online publication date for the Annual Review of Materials Research, Volume 50 is July 1, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates. 
    more » « less
  4. ; ; ; ; (, Nature Communications)
    Abstract Imaging the activity of neurons that are widely distributed across brain regions deep in scattering tissue at high speed remains challenging. Here, we introduce an open-source system with Dual Independent Enhanced Scan Engines for Large field-of-view Two-Photon imaging (Diesel2p). Combining optical design, adaptive optics, and temporal multiplexing, the system offers subcellular resolution over a large field-of-view of ~25 mm 2 , encompassing distances up to 7 mm, with independent scan engines. We demonstrate the flexibility and various use cases of this system for calcium imaging of neurons in the living brain. 
    more » « less
  5. ; ; (, 2022 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting (AP-S/URSI))
    Microwave radiometry is an emerging technology for noninvasive measurement of internal body temperature. This technique relies on the use of a near-field antenna placed on the skin that receives black body radiation from the tissues under it. Even for a well-matched antenna, mismatch is introduced from variations in the tissue layer properties and/or imperfect characterization of the dielectrics used for antenna assembly. This work demonstrates a design of a receiving antenna element for a human head-specific tissue stack, and a tuning procedure to improve impedance match. Measurements of a fabricated antenna against the forehead indicate that inaccurate characterization of the materials used for antenna assembly more significantly contribute to antenna mismatch than variations in the tissue properties of the forehead. Therefore, proper modeling of assembly materials, in addition to reasonably accurate tissue stack modeling, is crucial for near-field antenna design. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email