Peformance evaluation of a passive microwave imaging system

A test program was conducted to evaluate the passive microwave imaging system for possible application in the NASA Earth Resources Program. In addition to test data analysis, the report gives a brief description of the radiometer, its software, and the ground support equipment. The microwave image quality is adequate for remote sensing applications studies. Instrument problems are described, and suggestions are given for possible improvements and potential applications

Antenna and radome loss measurements for MFMR and PMIS with appendix on MFMR/PMIS computer programs

The NMSU/PSL radiometer antenna calibration facility is described, and the antenna and radome loss measurements made on the passive microwave imaging system and the multifrequency microwave radiometer are summarized. Antenna/radome data reduction techniques, estimation of sky brightness temperatures, and bucket performance tests are presented along with radiometer computer programs

Radiometric Receiver for Passive Microwave Imaging System

The paper describes a new method to develop a zero-type W-band radiometric receiver. The block diagram and operating algorithm of the digital control system are presented. The main advantages of the zero method in passive radio physical investigations in comparison with classical engineering solutions are shown

Real-time and portable microwave imaging system

Microwave and millimeter wave imaging has shown tremendous utility in a wide variety of applications. These techniques are primarily based on measuring coherent electric field distribution on the target being imaged. Mechanically scanned systems are the simple and low cost solution in microwave imaging. However, these systems are typically bulky and slow. This dissertation presents a design for a 2D switched imaging array that utilizes modulated scattering techniques for spatial multiplexing of the signal. The system was designed to be compact, coherent, possessing high dynamic range, and capable of video frame rate imaging. Various aspects of the system design were optimized to achieve the design objectives. The 2D imaging system as designed and described in this dissertation utilized PIN diode loaded resonant elliptical slot antennas as array elements. The slot antennas allow for incorporating the switching into the antennas thus reducing the cost and size of the array. Furthermore, these slots are integrated in a simple low loss waveguide network. Moreover, the sensitivity and dynamic range of this system is improved by utilizing a custom designed heterodyne receiver and matched filter. This dissertation also presents an analysis on the properties of this system. The performance of the multiplexing scheme, the noise floor and the dynamic range of the receivers are investigated. Furthermore, sources of errors such as mutual coupling and array response dispersion are also investigated. Finally, utilizing this imaging system for various applications such as 2D electric field mapping, scatterer localization, and nondestructive imaging is demonstrated --Abstract, Page iii

Tissue Surface Identification for Microwave Imaging System Calibration

The methods used for biomedical imaging include X-ray, magnetic resonance imaging (MRI), ultrasound, and most recently, microwave imaging each with its own advantages and disadvantages for specific application. The frequency dependent nature of the Electromagnetic (EM) waves makes it possible for microwave imaging to achieve a tissue differentiation comparable to that obtained by X-ray and would be superior to ultra sound and MRI. This work addresses one aspect of an ongoing research effort at Rochester Institute of Technology which is a new methodology for detecting diseased tissues by a non-invasive procedure. The methodology is based on the extraction of the frequencydependent electrical properties of tissue that can differentiate between healthy and diseased states using ultra-wideband (UWB) pulses that are allowed to impinge on multiple layers of biological tissue. The reflected/scattered signal is analyzed to obtain frequency dependent permittivity and conductivity that correspond to each tissue layer. For system implementation, a planar flexible antenna array is utilized that would be wrapped like a cuff around a specific part of the human body. The present work addresses the development of a calibration procedure to locate each antenna element with respect to the shape of the body surface. An algorithm for determining the shape of the surface has been developed in this thesis. The methodology involves placing a flat N x N planar antenna array above the tissue surface. The antenna elements are excited one at a time and the rest of the elements are used to receive signals scattered from the body surface. From the transmitted and received signals, the distance, r, from each antenna to the surface can be determined and in this work it is assumed to be known. Corresponding to this distance the sphere of radius rij is drawn from the (i,j)th antenna element. Assuming that the surface is convex, this sphere will be tangent to the body surface at the point with coordinates (xij, yij, zij). Due to the fact that the antennas are placed relatively close to each other, it can be assumed that the parameters of the neighboring tangent planes are the same. Using this information together with the distances rij, r(i+1)j and r(i,j+1), the necessary equations have been set up and solved for the coordinates (xij, yij, zij). This process is repeated for N xN sample points on the surface which are then used to determine the surface by an interpolation algorithm. The algorithm is implemented in MATLAB and its accuracy has been assessed for different kinds of surfaces and different sized planar antenna array. The agreement between the estimated and the actual surfaces is very good for smooth convex surfaces. For surfaces with more curvature, the mean square error is higher. The performance of the algorithm with respect to the measurement noise has also been analyzed. After the planar antenna array has been calibrated with respect to the surface, the frequency response of the paths from the antenna to each tissue layer including the surface can be obtained. This information is then used for an accurate tissue differentiation

Wearable Microwave Imaging System for Brain Stroke Imaging

This paper presents the experimental validation of the detection capabilities of a low complexity wearable system designed for the imaging-based detection of brain stroke. The system approaches the electromagnetic inverse problem via a 3-D imaging algorithm based on the Born approximation and the Truncated Singular Value Decomposition (TSVD). For testing, flexible antennas with custom-made coupling-medium are prototyped and assessed in mimicked hemorrhagic and ischemic stroke conditions. The experiment emulates the clinical scenario using a single-tissue anthropomorphic head phantom and strokes with both 20 cm 3 and 60 cm 3 ellipsoid targets. The imaging kernel is computed via full-wave simulation of a virtual twin model. The results demonstrate the capabilities for detecting and estimating the stroke-affected area

Microwave Imaging System for In-Line Security Assessment

3The accidental foreign bodies contamination is still a major issue for food manufacturing industries. The continuous growth of automation along production lines together with the increasing attention of the customers towards food products quality, improved the industries care aiming to avoid complaints and ensure the best possible quality. As a matter of fact, several technologies are employed, but they lack in detecting certain class of contaminants, such as low-density plastics or small glass fragments that could turn into a severe threat, in particular for children. This work proposes a microwave imaging system in order to overcome these limitation in employed technologies. The design and characterization are reported in this paper; the simulations are addressed to the realization of a system prototype.partially_openopenRicci, Marco; Crocco, Lorenzo; Vipiana, FrancescaRicci, Marco; Crocco, Lorenzo; Vipiana, Francesc

Modeling and reconstruction in a 3D microwave imaging system

In this paper we discuss the design and modeling of a 3D system for microwave imaging. The antenna system consists of 32 monopoles in a cylindrical configuration. A FDTD model of the system is used in the imaging reconstruction algorithm. Here we show a comparison of the data generated from the numerical FDTD model with measured data, as well as imaging of a simple target using this system. The agreement in the model is good and the imaging of a test object is successful