<title>Ultrawidebandwidth measurements of foliage transmission properties at UHF - Measurements system and results</title>

Abstract

A bistatic radar system has been built by the Environmental Research Institute of Michigan (ERIM), sponsored by the Air Force's Wright Laboratory, Avionics Directorate under contract F33615-90-C-1506, to measure the transmission properties of foliage. The system is polarimetric and operates coherently over the band from 300-1300 MHz. Also, the system can scan foliage in angle to determine spatial variations in the transmission properties of foliage. The variation in foliage transmission over the frequency band is important because imaging radars typically operate coherently over a bandwidth. Similarly, the angular variation in foliage transmission is important because imaging radars synthesize an aperture over angle. Variation in the foliage transmission properties over the bandwidth and scan geometry (or angular variation) can degrade the ability of the radar to focus a foliage obscured object. The ERIM Wideband System is ground-based with one antenna attached to a carriage which can move ten meters horizontally along a rigid track and the other antenna attached to a fixed tripod. The moving antenna and carriage can be elevated 15 m using a scissor lift and at this height can operate above most of the foliage canopy. The ground based system can measure the one-way foliage transmission properties in a geometry which is similar to a typical airborne imaging radar. Measurements of the angular and frequency correlation of foliage transmission will be presented along with a discussion of their impact on foliage penetrating radars.