A Quantitative Analysis of Sea Clutter Decorrelation with Frequency Agility

A brief statement of the sea clutter problem in surface-search radar operation illustrates the need for some form of signal-to-clutter enhancement. Post-detection integration used in the simpler radars is limited by the pulse-to-pulse correlation of the clutter. Analysis of the effect of changing frequency from pulse to pulse leads to an expression for the correlation between pulses in the sequence. Knowing this correlation, the reduction in the fluctuating clutter component produced by integration can be determined. This is described by an equivalent number of independent pulses, Nc. For the particular case of sinusoidal modulation of the transmitted frequency, N6 is computed. The critical dependecne of Nc upon the modulating frequency fm is illustrated by spectrum photographs. Choice of an optimum fm is discussed. The results of computations of N4 for optimum fm are presented as a family of normalized curves. These data permit the tradeoff of the radar parameters against their quantitative effect on radar performance.