PURPOSE: To prevent abnormal operations by extending the maximum allowable amplitude permitted inside a recursive digital filter and providing an amplitude limiting circuit at the output end of the filter.
CONSTITUTION: In case that digital output signal y(n) to satisfy the expression is obtained for digital input signal x(n), x(n-k) and y(n-k) are delayed into y(n-k-1) and y(n-k-1) by delaying shift registers 6 and 7 and delaying shift registers 8' and 9' respectively, and coefficients ak and bk are multiplied from coefficient multipliers 1∼5 in respect to x(n-k) and y(n-k), and they are added by adder 10. The amplitude in the addition output obtained in this manner is detected by 11; and when the detected amplitude exceeds y'(nT) which is allowable for y(n) obtained from output end OUT, the amplitude is limited by amplitude limiting circuit 12.
OONISHI MAKOTO
KUWABARA HIROSHI
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