Target Resolution of a Doppler Radar with Statistically Variable PRF

ABSTRACT

Intentional jamming by the enemy has forced the radar system designer to incorporate sophisticated methods in system design for diluting their effectiveness. One of these methods consists of varying the inter pulse spacing in accordance with some statistical code. The present paper deals with the performance of a Doppler radar with respect to target resolution when the pulse repetition period is varied in accordance with the Random and Gaussian distributions.

The paper first deals with the calculations of variance which is a measure of the dispersion of the values of the ambiguity function. It is expressed as a function of the integration period and the total swing of the pulse spacing about the normal PRF. Numerical calculations carried out for integration periods corresponding to 100, 250 and 500 pulses for total swings of 0·5, 0·75 and 1·0 times the inter pulse period, indicate that the variance rises sharply from zero in the vicinity of negligible Doppler separation to half its limiting value. For higher values of Doppler separation the variance oscillates about a value corresponding to half the number of integrated pulses. The paper then deals with the calculations of the limiting values of the ambiguity diagram about the mean for 99·87 per cent probability. Computations indicate that for both distributions, the first two sidelobes have negligible fluctuations about the mean value. Thus the employment of Random or Gaussian distribution for positioning does not essentially degrade the target resolution of the radar.