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A quadrupole illumination scheme with specific phase distribution at the excitation elements is proposed in order to improve the noise performance of microwave imaging systems. In comparison with conventional single antenna illumination, the proposed system features simpler calibration while at the same time drastically improving the signal-to-noise ratio. An application with planar scanning is considered...
A new sensitivity analysis method is proposed to compute the S-parameter Jacobian for metallic shapes. The method is exact in the sense that it uses an analytical formulation, which is independent of the method of numerical full-wave analysis and the respective system matrix. It uses only the field solution on the surface of the metallic objects. The field solution can be provided by any valid electromagnetic...
A space mapping modeling technique utilizes recent commercially available full-wave EM adjoint sensitivity analysis. A good surrogate model is built using only one EM simulation along with an adjoint sensitivity evaluation. The technique calibrates a surrogate by matching responses and corresponding adjoint sensitivities. This surrogate is accurate over an extended region of the parameter space. We...
We propose signal processing algorithms to improve the quality of the images obtained with microwave raster scanning measurements. These algorithms include: (1) blind deconvolution and (2) microwave holography. The first algorithm removes the integration effect of the antenna aperture using complex-valued blind deconvolution. The second algorithm implements near-field microwave holographic imaging...
We review work relevant to the area covered by the transmission line matrix (TLM) method, including historical TLM developments and design parameter sensitivity analysis for time-domain simulations. We consider TLM sensitivity analysis, compare it with the finite difference approach, and demonstrate its use in accelerating design optimization. We discuss ways of using space-mapping concepts for modeling...
We propose a procedure for accelerating the space mapping optimization process. Exploiting both fine- and surrogate-model sensitivity information, a good mapping between the two model spaces is efficiently obtained. This results in a significant speed-up over direct gradient-based optimization of the original fine model and enhanced performance compared with other space mapping approaches. Our approach...
We discuss a number of practical issues in measurements with the recently proposed microwave raster scanning setup for near-field imaging of tissue. We consider the uncertainties in the measurements of phantoms emulating biological tissues. We discuss improvements in the design of sensors tailored for this application. We evaluate the performance of a tissue sensing sensor in terms of a parameter...
This paper presents an approach to estimate the characteristics of multiple narrow-opening cracks from magnetic flux leakage signals. The locations, orientations, lengths and depths of the cracks are the objective of the inversion process. This procedure provides a reliable estimation of crack parameters in two separate subsequent steps. In the first step, the Canny edge detection algorithm is used...
The design, fabrication, and characterization of an ultra-wide band antenna for near-field microwave imaging are presented. The focus is on an application in microwave breast tumor detection. The new antenna operates as a sensor with the following properties: 1) direct contact with the imaged body, 2) more than 90% of the microwave power is coupled into the tissue, 3) ultra-wide band performance,...
The contrast between the electrical properties of the components of a dielectric body enables its imaging using microwave measurements. In a typical active imaging scenario, microwave power is radiated via an antenna and the scattered power is picked by one or more antennas. The scattered signals are then analyzed to detect and identify significant scatterers (targets).
In this paper we propose a new self-adjoint technique for sensitivity analysis with MoM solutions. This technique uses discrete perturbations of the optimizable shape parameters on a predetermined MoM grid. The purpose is to aid gradient-based optimization of antenna structures.
A protocol to measure the system fidelity of a two-antenna UWB system for near-field microwave imaging is presented. It consists of identical transmission and reception antennas that are highly directive and work without coupling medium in tissue sensing applications. System fidelity is evaluated with and without phantoms inserted between the antennas. The extraction of the fidelity of one antenna...
A near-filed microwave imaging setup is investigated. The setup benefits from the high near-field directivity and good efficiency of a recently proposed ultra-wide band TEM horn antenna. The setup employs planar aperture scanning. It consists of two antennas aligned along each other's boresight and moving together to scan two parallel apertures. The imaged object lies between the two apertures. With...
A novel general formulation of the response sensitivity analysis is proposed and implemented in a computationally efficient algorithm for the detection of electrically small scatterers in a known background medium. The responses of the background medium where no scatterers are present are modeled via ultra-wideband time-domain simulation. Using these modeled responses and the measured responses of...
We review the Adjoint Variable Method (AVM) for efficient estimation of real objective function sensitivities with time-domain TLM. The original electromagnetic structure is first simulated using TLM. An adjoint TLM simulation that runs backward in time is derived and solved. The sensitivities of the objective function with respect to all designable parameters are estimated using only the original...
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