On the performance of electronically tunable fractional-order oscillator using grounded resonator concept

Recent works target the design of fractional-order oscillators. However, some features of such circuits are not frequently considered in the design despite their importance in practice. This work provides an analysis of the fractional-order oscillator design procedure with a simple but still beneficial electronic tuning feature. The presented design allows us to keep a stable and non-standard phase shift between produced harmonic signals while tuning the oscillation frequency of the oscillator. Grounded fractional-order elements and modern commercially available active elements are implemented in the designed topology. Time domain results as well as spectral analysis are obtained from experimental measurements. Moreover, several values of non-standard phase shifts are tested. The experimental verification targets the low-frequency bandwidth from several hundreds Hz up to several kHz because of possible application areas in these bands (audio) and due to a very low-impedance character of the used RC constant phase elements as approximants of fractional-order capacitors.