Tuning of a filter circuit is accomplished by determining a real RC time constant value for the filter circuit, then comparing the real RC vale to a predetermined RC value. If the real RC value does not match the predetermined RC value, the real RC value is varied (e.g. using a number of capacitors in...http://www.google.com/patents/US6677814?utm_source=gb-gplus-sharePatent US6677814 - Method and apparatus for filter tuning
