Mechanical domain non-degenerate parametric resonance in torsional mode micro electro mechanical oscillator

We present experimental results of operation of a single oscillator with time varying stiffness as an auto-parametric resonator in both degenerate and non-degenerate mode. The stiffness corresponding to the first two natural modes of this oscillator is designed to be time dependant and under such a condition the "sum type" parametric resonance is observed. This two mode non-degenerate version of parametric resonance offers some advantages over the degenerate version. The driving frequency and the response frequency are totally decoupled (they are related by integer or fractional harmonics in the case of degenerate amplification). The drive frequency, which is the sum of the first two natural mode frequencies, can be designed to be as far away as needed from the first natural frequency at which the signal gets amplified.