Accession Number : ADA312399

Title :   Exponential Decay in Windblown Radar Ground Clutter Doppler Spectra: Multifrequency Measurements and Model.

Descriptive Note : Technical rept.,

Corporate Author : MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB

Personal Author(s) : Billingsley, J. B.

PDF Url : ADA312399

Report Date : 29 JUL 1996

Pagination or Media Count : 106

Abstract : A new empirical model for windblown radar ground clutter Doppler spectra is developed based on many clutter spectral measurements obtained with Lincoln Laboratory's L-Band Clutter Experiment (LCE) and Phase One five-frequency (i.e., VHF, UHF, L-, S-, and X-band) instrumentation radars over spectral dynamic ranges reaching 60 to 80 dB below zero-Doppler peaks. The model includes both ac and dc spectral components. Ac spectral shape is specified as exponential, with the Doppler-velocity exponential shape factor strongly dependent on wind speed but independent of radar frequency, VHF to X-band. The exponential shape is intermediate in spectral extent between the Gaussian shape of historical usage (now acknowledged as being too narrow) and power-law shapes of more recent usage (which are too wide when extrapolated to levels 60 to 80 dB down). The ratio of dc to ac spectral power in the model is determined by an empirically derived analytic expression that captures the strong dependencies of dc/ac ratio on both wind speed and radar frequency in the measurement data. Many examples of windblown clutter spectra are provided and compared with model predictions, encompassing variations in wind speed and radar frequency, as well as in other parameters such as polarization, range, cell size, grazing angle, wind direction, measurement site, and season of the year. Although the exponential model is explicitly derived to be applicable to windblown trees, examples are also provided of measured clutter spectra from scrub desert, rangeland and cropland vegetations which indicate that the model can also perform adequately for other windblown vegetation types by suitably adjusting its dc/ac term.

Descriptors :   *RADAR CLUTTER, MEASUREMENT, POLARIZATION, PREDICTIONS, SPECTROMETRY, SEASONAL VARIATIONS, WIND DIRECTION, WIND VELOCITY, VEGETATION, DESERTS, X BAND, ULTRAHIGH FREQUENCY, VERY HIGH FREQUENCY, DYNAMIC RANGE, GROUND CLUTTER, MOVING TARGET INDICATORS, L BAND, GRAZING ANGLES.

Subject Categories : Active & Passive Radar Detection & Equipment

Distribution Statement : APPROVED FOR PUBLIC RELEASE