Measurement and analysis of sea clutter using an experimental X-band marine radar

This study relates mainly to the measurement and analysis of sea clutter return at radar ranges of 600, 1200 and 1800 yards. The effect of varying radar definition, wave height and windspeed upon the sea clutter's statistical and spectral properties have been investigated. The laboratory work is chiefly concerned with the development of the radar signal processing system between the R.F balanced mixer and the video plan-position-indicator display. Particular attention has been given to the design of the main I.F logarithmic-receiver with respect to the dynamic range, bandwidth requirement and noise divergence. Test equipment has been developed specifically to check the I.F/video systems performance factors like pulse fidelity, bandwidth limitations, noise interference and nonlinearities. Standard calibration tests have been conducted on the R.F/I.F and video systems as well as on the computer analysis subroutines. Sea clutter measurements were carrried out at Eastney radar station, Southsea, using an experimental x-band marine radar with vertical polarization. The scattering model proposed by Wright has been examined for small antenna depression angles. Theoretical log-Rayleigh probability density/distribution curves were calculated and compared with the experimental results, if only to indicate, though indirectly, the extent of non Rayleigh nature of sea clutter return. Statistical and spectral models of sea clutter have been compiled. It is shown that the log-receiver output variance is only constant for a given class of probability distributions. Attention is given to the effect of linear networks on bandlimited spectra of radar noise. Limitations of measurement approach, radar system R.F/I.F and video performance have been discussed.