Publications

This paper reports post-CMOS compatible aluminum nitride dual mode resonator filters that realize 4th order band-pass filters in a single resonator device. Dual mode filters at 106 MHz operating in their fundamental mode are reported with insertion losses as low as 5.5 dB when terminated with 150 Ω. A notching technique is demonstrated for varying the 3 dB bandwidth of these filters from 0.15 to 0.7%, overcoming a significant limitation of previous work. Dual mode filters operating at their 5th and 10th overtones are reported scaling the operating frequencies of this class of device to 0.55 and 1.1 GHz.

This work presents a new type of MEMS resonator based on launching an acoustic wave around a ring. Its maximum frequency is set by electrode spacing and can therefore provide a means for developing resonators with center frequencies in the GHz. In addition since the center frequency is dependent on the average radius it is not subject to lithographic process variations in ring width. We have demonstrated several Ring Waveguide (RWG) Resonators with center frequencies at 484 MHz and 1 GHz. In addition we have demonstrated a 4th order filter based on a RWG design.

A MEMS bulk wave acoustic bandgap has been designed and experimentally verified. The acoustic bandgaps are realized by including tungsten (W) scatterers in a SiO2 matrix. Wide frequency ranges where acoustic waves are forbidden to exist are formed due to the large density and acoustic impedance mismatch between W and SiO2. The acoustic bandgap structures are fabricated in a 7-mask process that features integrated aluminum nitride piezoelectric couplers. Acoustic bandgaps in a square lattice have been measured at 33 and 67 MHz with up to 35 dB of acoustic rejection and bandwidths exceeding 35% of the midgap. ©2007 IEEE.

While existing work in neural interfaces is largely geared toward the restoration of lost function in amputees or victims of neurological injuries, similar technology may also facilitate augmentation of healthy subjects. One example is the potential to learn a new, unnatural sense through a neural interface. The use of neural interfaces in healthy subjects would require an even greater level of safety and convenience than in disabled subjects, including reliable, robust bidirectional implants with highly-portable components outside the skin. We present our progress to date in the development of a bidirectional neural interface system intended for completely untethered use. The system consists of a wireless stimulating and recording peripheral nerve implant powered by a rechargeable battery, and a wearable package that communicates wirelessly both with the implant and with a computer or a network of independent sensor nodes. Once validated, such a system could permit the exploration of increasingly realistic use of neural interfaces both for restoration and for augmentation. © 2007 IEEE.

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A 256-site microsystem comprises 4 neural recording arrays with integrated amplification and multiplexing circuitry and an implantable spike detection ASIC. The spike detector compresses the amount of neural data by 92%, increasing the total number of channels recorded wirelessly from 25 to 312. The implantable circuitry consumes 5.4mW at 3V. ©2005 IEEE.

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The goal of this LDRD project was to evaluate the possibilities of utilizing Stochastic resonance in micromechanical sensor systems as a means for increasing signal to noise for physical sensors. A careful study of this field reveals that in the case of a single sensing element, stochastic resonance offers no real advantage. We have, however, identified a system that can utilize very similar concepts to stochastic resonance in order to achieve an arrayed sensor system that could be superior to existing technologies in the field of inertial sensors, and could offer a very low power technique for achieving navigation grade inertial measurement units.