WALL CHARACTERIZATION AND AUTOFOCUSING TECHNIQUES FOR TWI SYSTEM

Abstract

Investigation of the objects behind an opaque wall is very promising field for a rescue and security applications nowadays. The quality of through the wall radar image depends upon knowledge of the wall parameters. Ambiguities in parameters smear and blur the image and shift the targets from its true location. In this research first calculation of complex dielectric constant of low loss material has been done by means of real equations requiring only one dimensional root search techniques, in which data has been taken from both side of the wall. But it is not suitable in real time applications as other side come in danger zone. So a new method has been -developed, which require measurement from one side of the wall for this purpose the magnitude and the time position of reflections from inner and outer surfaces of the wall are extracted from the data. The effect of wall parameters on image has been shown by developing 2D- beam forming image. The wall causes wave refractions and change in propagation speed, this effect alters the time between transmitter to target, and target to receiver. Coherently combining all the signals at a same position can enhance image quality, but the calculated wall parameters are not exact so auto-focusing techniques based on higher order statics is presented which correct errors under ambiguities. All the techniques have been developed on real data and data has been taken in real time environments by interfacing the VNA to the laptop