The MEMS pulsed digital oscillator (PDO) below the Nyquist limit

This paper describes new theoretical and experimental results showing that the pulsed digital oscillator, a set of sigma–delta-based oscillator structures for MEMS recently introduced by the authors, can maintain a good oscillation behaviour even for sampling frequencies below the Nyquist limit. Specifically, the theory is extended to the undersampling region and the complete set of ‘perfect’ frequencies (sampling frequencies at which the oscillation frequency is the natural frequency of the resonator) is analyzed. Therefore, an extension of the use of this kind of oscillators to high frequency applications becomes straightforward.