1,234,704. Radar. BURROUGHS CORP. 8 Oct., 1969 [15 Oct., 1968], No. 49397/69. Heading H4D. In a radar system for generating signals representing weather outline contours, logarithmic video echo signals are subject to swept gain, a root-mean-square estimate of the level of weather clutter is formed and if poor estimates are made consistently a system parameter is adjusted to better them. The output of swept gain unit 11 is fed to a delay line with taps spaced by one range cell and connected to a summing amplifier 17 to give an estimate of the mean value for the present range sweep. This estimate is modified by a unit 19 (see below) and the modified estimate is encoded and sampled each ¢ nautical mile by a unit 23 which converts the analogue signal input to digital form and holds the most significant four bits. Unit 25 subtracts from the encoded estimate the stored estimate in memory 27; the difference is weighted and added to the estimate from the previous sweep, the resultant being stored in the memory until the same range cell on the following sweep receives a new estimate. The weighting is determined by a unit 29.
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