Patent ID: 6219196
Filing Date: 2001-04-17
Classification: G11B

Abstract:
A method for deriving the frequency characteristic of a control loop, comprising the steps of:deriving the frequency characteristic of the control loop including a first notch filter between a maximum frequency f.sub.max of said frequency characteristic to be derived and a frequency f.sub.3 (f.sub.max >f.sub.3), said first notch filter having a central frequency of f.sub.1 that falls between a minimum frequency f.sub.min of said frequency characteristic to be derived and said frequency f.sub.3 (f.sub.min <f.sub.3); by using the frequency characteristic of said first notch filter, calculating a first portion of said frequency characteristic of the control loop excluding said first notch filter from said frequency characteristic of said control loop including said first notch filter;deriving the frequency characteristic of said control loop including a second notch filter between said minimum frequency f.sub.min and said frequency f.sub.3, said second notch filter having a central frequency of f.sub.2 that falls between said maximum frequency f.sub.max and said frequency f.sub.3 ;by using said frequency characteristic of said second notch filter, calculating a second portion of the frequency characteristic of the control loop excluding said second notch filter from said frequency characteristic of said control loop including said second notch filter; andcombining said first and second portions of said frequency characteristic.