Design of the Self-Tracking Filter Based on Frequency to Voltage Conversion

In order to make cutoff frequency of filter that can be changed automatically with the time-varying signal, this chapter presents a new self-tracking filter structure which is based on frequency to voltage conversion. Input signal is converted into voltage signal through the F/V circuit. The output voltage of F/V is used to control cutoff frequency of the filter which is constituted of analog multiplier MLT04, current feedback amplifier AD844, a few resistors and capacitors. The design principle is introduced in detail, the design formulas are derived, and the circuit of self-tracking one-order low-pass and high-pass filter are given. When the input signal’s frequency is in the range of 10–100 kHz, the simulated and measured results show the effectiveness of this new method. The cutoff frequency of the filter can be adjusted automatically by the voltage which is proportional to frequency of input signal. So it realizes the frequency self-tracking.