Simulation of the Active Filter Tuning Systems Based on Delay Times, Periods and Phases Comparison

In this paper is described an auto tuning methods of active RC filters. The tuning range and the tuning accuracy are analyzed. To verify the method, analog and digital part of the tuning system are cosimulated together. The simulation results shows that the time constant tuning accuracy is ±3.8% for tuning circuit based on delay times comparison, 5.5% for circuit based on period comparison and 3.9% for tuning circuit based on phase comparison by 4-bit code sequence and time-constant variation ±28%.