Cornell researchers have developed a microelectromechanical (MEMS) oscillator with continuous control of the output phase and frequency.  The device takes advantage of a phenomenon known as frequency entrainment, wherein the resonant frequency of the mechanical oscillator is detuned, and a reference signal is left fixed at the natural frequency of the mechanical resonator.  The instantaneous frequency of oscillation will be fixed to the reference frequency; however, the phase of the mechanical oscillations will be controlled by detuning the resonator's natural frequency of resonance.  Accordingly, the mechanical oscillations take on the stability and the frequency of the reference signal, while the output phase of the mechanical oscillations can be easily controlled through the amount of thermal dissipation into the structure.

Such a device would be useful for systems of acoustic or radio frequency emitters which require a fixed frequency and have need for individual control of the output phase of each emitter.  In one such example, the thermal dissipation is continuously varied to encode information in phase or frequency on the carrier frequency defined by the injection lock MEMS oscillator.  Another such example is phased array radar where an array of emitters broadcast a single tone however phase differences between the emitters determine the constructive or destructive interference pattern of the array.

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Potential Applications

• RF oscillators

Advantages

• Compact size and RF operation range
• Simple and precise output phase control

File Number: 3694