Rosenberg, Klein & Lee
Frequency tuning loop for active RC filters
A tuning loop which can tune the cut-off frequency of an active RC filter is disclosed. The cut-off frequency is determined by equivalent resistance and equivalent capacitance in an active RC filter, therefore, the tuning loop changes the equivalent resistance to tune the cut-off frequency. The time constant of the circuit is compared to see if it is equal to the applied preset time cycle after the equivalent resistance value is changed. The cut-off frequency of the filter is tuned to a preset value when the time constant in the circuit is equal to the applied preset time cycle, or the equivalent should be changed until the time constant equal to the applied preset time cycle. A precise result can be obtained after being tuned by tuning loop due to the each component of the tuning loop are operated in an environment which is equivalent to the active RC filter.
Industrial Technology Research Institute
H
H03H
inventional
Chih-Hong Hung-I
Lou Chen