A New Approach to High-Sensitivity, Wide-Bandwidth Sensing and Imaging

University Of Arizona, Tucson AZ

Investigators

Abstract

This project is concerned with electromagnetic sensing and imaging applications that require relatively high power levels over wide bandwidths. In such cases, there may be interference between the wideband signal source and other licensed users of the electromagnetic spectrum. Such interference is prohibited by FCC regulations. We propose using reserved Industrial, Scientific, and Medical (ISM) frequency bands for the measurements. At the ISM frequencies, unlimited power can be used if necessary. In order to synthesize a wideband response from narrow-band measurements at the ISM frequencies, we will investigate methods for using the observed response at a few closely spaced frequencies and then predicting the full wideband response. A conventional time-domain response can then be calculated, or an interpretation in the frequency domain can be carried out. A critical feature of the proposed approach is that very accurate data must be obtained at the measured frequencies. In the past, inaccuracies in the data have led to limited success with this approach in practical problems. Using a newly developed calibration method, we expect to be able to obtain the high accuracies that will be required. This proposed approach, we believe, has tremendous potential in many fields. For example, ground penetrating radar (GPR) and non-destructive evaluation (NDE) techniques often require wideband, high-power electromagnetic fields in order to image covered objects. Other potential applications include medical imaging. Although a source of EM fields in a medical application will probably not interfere with licensed radio stations, there is a growing risk that the proliferation of such wideband devices may cause interference with each other. There are significant advantages in having each of the imaging devices in a crowded environment operate in a reserved, narrow frequency band, rather than over wide bands that risk interference with each other.