Engineering topics

Paladhi, P. Roy

Publications and source records attributed to Paladhi, P. Roy.

4 records

DOE OSTI2015

Design and development of an electrically-controlled beam steering mirror for microwave tomography

Microwave tomography has gained significant attention due to its reliability and unhazardous nature in the fields of NDE and medical industry. A new microwave tomography system is presented in this paper, which significantly reduces the design and operational complexities of traditional microwave imaging systems. The major component of the proposed system is a reconfigurable reflectarray antenna which is used for beam steering in order to generate projections from multiple angles. The design, modeling and fabrication of the building block of the antenna, a tunable unit cell, are discussed in this paper. The unit cell is capable of dynamically altering the phase of the reflected field which results in beam steering ability of the reflectarray antenna. A tomographically reconstructed image of a dielectric sample using this new microwave tomography system is presented in this work.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2015

Class of backpropagation techniques for limited-angle reconstruction in microwave tomography

Filtered backpropagation (FBPP) is a well-known technique used in Diffraction Tomography (DT). For accurate reconstruction using FBPP, full 360° angular coverage is necessary. However, it has been shown that using some inherent redundancies in the projection data in a tomographic setup, accurate reconstruction is still possible with 270° coverage which is called the minimal-scan angle range. This can be done by applying weighing functions (or filters) on projection data of the object to eliminate the redundancies and accurately reconstruct the image from 270° coverage. This paper demonstrates procedures to generate many general classes of these weighing filters. These are all equivalent at 270° coverage but vary in performance at lower angular coverages and in presence of noise. This paper does a comparative analysis of different filters when angular coverage is lower than minimal-scan angle of 270°. Simulation studies have been done to find optimum weight filters for sub-minimal angular coverage (<270°)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2014

A microwave tomography system using a tunable mirror for beam steering

Microwave tomography is a fast-growing technique in the fields of NDE and medical industry. This paper presents a new microwave tomography system which reduces the complexities of conventional microwave imaging systems by utilizing a reconfigurable mirror, a tunable reflectarray antenna. In order to build a tunable reflectarray with beam steering capabilities, the unit cell characteristics should dynamically alter. Modelling and experimental results of a single unit cell are presented in this work.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2014

Reconstruction algorithm for limited-angle diffraction tomography for microwave NDE

Microwave tomography is becoming a popular imaging modality in nondestructive evaluation and medicine. A commonly encountered challenge in tomography in general is that in many practical situations a full 360° angular access is not possible and with limited access, the quality of reconstructed image is compromised. This paper presents an approach for reconstruction with limited angular access in diffraction tomography. The algorithm takes advantage of redundancies in image Fourier space data obtained from diffracted field measurements and couples it to an error minimization technique using a constrained total variation (CTV) minimization. Initial results from simulated data have been presented here to validate the approach.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗