| 摘要 |
<p>PURPOSE:To positively suppress a surface-of-sea reflecting signal by respectively multiplying moment signals of plural orders, calculated from linear signals obtained through antilogarithmic conversion of difference signals, by coefficients and setting the sum thereof as a threshold value and subtracting the sum from the linear signals. CONSTITUTION:From a logarithmic conversion signal Y obtained by amplifying a radar signal X through a logarithmic amplifier 100, an moving average value signal (Y) of (N) signals Y is subtracted to produce a difference signal V from the first difference circuit 12. This signal V is subjected to antilogarithmic conversion through an antilogarithmic operation circuit 14 to obtain a linear signal Z which is, in turn, inputted to a threshold value operation part 50. In the operation part 50, moment signals from the first order to the n-th order (n is 4 in this example) of the signal Z are calculated by first, second, third and fourth order moment operation circuits 16-1 - 16-4 and multiplied by coefficients predetermined for every moment by first, second, third and fourth order moment coefficient circuits 18-1 - 18-4 and the sum of the respective moment signals subjected to coefficient multiplication is calculated as a threshold signal T by a summing circuit 20 and the signal T is subtracted from the signal Z to obtain a final output signal. By this method, a signal causing constant erroneous alarm probability can be calculated with respect to a radar signal containing a surface-of-sea reflecting signal according to Weibull distribution and the surface-of-sea reflecting signal is suppressed to make it possible to clearly display a ship image.</p> |
