An ultrawideband, polarimetric radar for the study of sea scatter

An ultrawideband radar system is described which has the capability of making pulse-to-pulse polarimetric measurements of the dynamic water features responsible for radar backscatter from the sea. The fast risetime voltage step produced by a Tektronix time-domain reflectometer (TDR) is used to excite a 6-12-GHz amplifier, producing a short (15 cm) radar pulse, A pair of 2- to 18-GHz antennas and appropriate pulse-to-pulse transmit and receive switching capability allows the collection of four consecutive equivalent-time-sampled pulses, one for each combination of the linear transmit and receive antenna polarizations. A polarimetric scattering matrix is then obtained at a sequence of frequencies across the 6-12-GHz band through the Fourier transform of each of the four waveforms and the application of an ultrawideband, polarimetric calibration procedure. The effect of motion on the computed scattering matrix is discussed and quantified, as this is an important consideration for polarimetric investigations of the water features responsible for radar sea scatter, A technique is then presented which compensates for the effects of target translation during the sampling interval. Scattering measurements of several rigid targets and of small breaking waves in a wave tank are used to illustrate the unique capabilities of this system and its applicability to sea scatter studies.>