Current Research
Projects:
MEMS Parametric-Effect
Amplifiers
This
work presents the theory and measurements of a mechanical parametric
effect amplifier with a 200 kHz input signal and a 1.84 MHz output
signal. The device used is a MEMS time-varying capacitor which
is composed of an array of low-stress metallized silicon-nitride
diaphragms, and is pumped by a large signal voltage at 1.64 MHz.
This induces a large change in the capacitance, and results in
parametric amplification of an input signal at 200 KHz. The parametric
amplifier capacitance is 500 pF resulting in an output impedance
of 140 W.
A higher impedance can also be achieved with a lower capacitance.
To our knowledge, this device is the first-ever MEMS mechanical
up-converter parametric-effect amplifier developed with an up-conversion
ratio of 9:1. The measurements agree very well with theory, including
the effect the series resistance and the Q of the MEMS time-varying
capacitor. The application areas are in amplifiers which operate
at very high temperatures (200-600°C), under high particle
bombardment (nuclear applications), in non semiconductor-based
amplification, and in low-noise systems since parametric amplifiers
do not suffer from thermal, shot or 1/f noise problems.
Sponsor: DARPA Sonoelectronics Program.
This work was done in collarboration with Prof. Khuri-Yakub at
Stanford University.
- J.P. Raskin, A.R. Brown, B.T. Khuri-Yakub
and G.M. Rebeiz, "Novel parametric-effect MEMS amplifiers/transducers,"
Accepted for publication at Transducers 2000, Hilton Head,
June 2000. (File: pdf 180 K)
- J.P. Raskin, A.R. Brown, B.T. Yakub
and G.M. Rebeiz, "A novel parametric-effect MEMS amplifier,"
IEEE Trans. Micro. Electro. Mechanical Systems, Vol. 9,
pp. 528-537, Dec. 2000. (File: pdf 300 K).
Figure 1: Top view of MEMS capacitor built at Stanford. The resonant frequency is 1.64 MHz with a Q of 18.
Figure 2: Top view of MEMS capacitor built at UoM. The resonant frequency is 3.2 MHz with a Q of 25.
Figure 3: Parametric amplifier measurement set-up.
Figure 4: Measured gain of the parametric amplifiers vs. varying load resistance.