The Effect of Transmitter Pulse Width on Bragg Positions in Pulsed Doppler Radar
by
J. Zhang, E. Gill, and J. Walsh
Memorial University of Newfoundland, St. John's, NL Canada A1B 3X5

Abstract
Abstract Recent cross section models of the ocean surface, which describe the first order scatter process when the transmitted
signal is a pulsed sinusoid, naturally include broadened Bragg peaks in terms of sampling functions. While this is wellknown
to be the case in practice, the classical cross sections have described this phenomenon in terms of delta functions. If the
ocean surface is cast as a zeromean Gaussian random process, it is seen that Fourier transformation of the electric field
for discrete time intervals results in fluctuation of the centroid frequencies of the Bragg regions in the resulting Doppler
spectrum. Here, it is shown that a fundamental reason for this variability lies in the the fact that the contribution to
the power spectrum at each Doppler frequency point is randomly affected by that at neighboring points. The standard deviation
of the centroid frequency is determined to be a function of pulse width and operating frequency. This, of course, will provide
one of the components necessary in developing error bars for surface currents deduced from pulsed radar data. Similar work
is ongoing to extend these ideas to frequency modulated systems.
