Abstract

We have developed a technique to measure the back scatter from particles using millimeter wavelengths. The system consists of two major components, the microwave source/receiving setup and the scattering chamber (lined with microwave absorbing material) [Fig. 1]. Millimeter wavelengths are used and thus size parameters near one are natural targets for the system. A waveguide horn antenna is utilized as both the source and the receiver. Ambient radiation, due to chamber reflections and antenna mismatch, is a major source of error in the system and is minimized by way of a cancellation bridge. The bridge adds to the received radiation a signal of equal amplitude and of opposite phase to the ambient leaving only the desired back scatter component. Although confined to the small (25 cm radius) vessel we have been able to perform far field measurements with good results.

© 1996 Optical Society of America