Bistatic high frequency radar ocean surface cross section for an antenna on a floating platform
Land-based high frequency surface wave radar (HFSWR) is an established sensor for 
ocean remote sensing. Placing an HFSWR on a floating platform has the advantage of 
mobility. However, antenna motion will distort the Doppler spectrum, which is used to 
extract ocean information and to detect the signatures of targets. In this thesis, significant 
effort has been expended on establishing radar cross section (RCS) models for a fixed 
receiver and a transmitter on a floating platform, analyzing the effect of the antenna 
motion, and developing a motion compensation method to eliminate the effect of the 
platform motion. 
The first- and second-order monostatic RCSs of the ocean surface for the case of a 
pulsed dipole source on a floating platform have been previously derived in the literature, 
with the assumption that the platform motion is a single-frequency sinusoid. Following 
that work, the research in this thesis is extended to the bistatic case. The effect of platform 
motion on simulated Doppler spectra is considered for a variety of sea states. It is shown 
that the resulting motion-induced peaks are symmetrically distributed in the Doppler 
spectrum. 
Following this work, the corresponding bistatic RCS models for a frequency modulated 
continuous waveform (FMCW) source are derived. Results show that the sidelobe 
level for an FMCW source is reduced with increasing extent of range bin. 
To mimic real world scenarios, platform motion is next modelled as a combination of 
two cosine functions, based on existing research of realistic horizontal motions of moored 
floating platforms. RCSs incorporating a dual-frequency platform motion model are then 
developed. These can be extended to a general form incorporating a multi-frequency 
platform motion. It is found that the platform motion can be viewed as a modulator of the 
radar frequencies, with the modulation indices related to the amplitudes of the platform 
motion. 
Finally, to mitigate the effect of platform motion on the Doppler spectra, a motion 
compensation method is proposed. This motion compensation method can be achieved 
by a deconvolution process. Calculations involving a RCS model, incorporating external 
noise, for an antenna on a floating platform are conducted in order to simulate field data 
and to examine this motion compensation method. The external noise is characterized as 
a white Gaussian zero-mean process. By using this newly-developed RCS model with 
external noise, motion compensation results under different sea states and signal-to-noise 
ratios (SNRs) are examined. The outcomes indicate that an iterative Tikhonov regularized 
deconvolution technique is superior to other compensation methods implemented in this 
study.