JPS57556A - Digital amplitude detecting circuit - Google Patents

Abstract

PURPOSE:To make operation time short, take the degree of multiplexing large, hence make hardware quantity small by using only the circuits for the purpose of comparing the absolute values of sampling values and multiplication of constants without using any 1/2 square circuit. CONSTITUTION:The signal Xi inputted to an input terminal 31 is inputted to an absolute value circuit 36, and the resultant absolute value ¦Xi¦ is inputted to an approximate root sum circuit 38 and a delay circuit 37. In the circuit 37, ¦Xi-n¦ is obtained, wherein the frequency (f) of the input signal is f=fT/(4n) and has the relation ¦Xi<2>+Xi-n¦<2>=(amplitude of Xi)<2>. The ¦Xi¦ of an input 381 and the ¦Xi-n¦ of an input 382 are compared and the smaller of these is multiplied by gamma=cotpi/8, and these are further compared, and whether the point of which the coordinates are ¦Xi¦, ¦Xi-n¦ is the part of an arc AB or the part of BC is judged and it is approximated by the straight line alphaX+betaY corresponding to this, whereby the approximate value of the anplitude of Xi is obtained. In this way, the error by approximating a 1/4 circle by four straight lines is <=+ or -1%.