Transceiver Front‐End Architectures Using Vibrating Micromechanical Signal Processors

Abstract

Transceiver architectures are proposed that best harness the tiny size, zero dc power dissipation, and ultra-high-Q of vibrating micromechanical resonator circuits. Among the more aggressive architectures proposed are one based on a micromechanical RF channel-selector and one featuring an all-MEMS RF front-end. These architectures maximize performance gains by using highly selective, low-loss micromechanical circuits on a massive scale, taking full advantage of Q versus power trade-offs. Micromechanical filters, mixerfilters, and switchable synthesizers are identified as key blocks capable of substantial power savings when used in the aforementioned architectures. As a result of this architectural exercise, more focused directions for further research and development in RF MEMS are identified.

Micromechanical Mixer-Filters (“Mixlers”)

“…Alternatively, if larger impedances are allowed, which would be the case in fully integrated systems where both transistors and micromechanics are integrated together to reduce node capacitances, smaller gaps may not even be needed, and in fact larger gaps may be preferred for dynamic range reasons [17]. The verified analytical theory presented predicts that these approaches, coupled with more conductive interconnect, should actually allow mixler devices with substantially better noise figure than demonstrated here, which might then make possible paradigm-shifting MEMS-based transceiver architectures aimed at enhancing communication robustness and lowering RF power consumption [1].…”

“…In terms of variables from Fig. 2, and assuming for now that the tuning electrodes and are given the same dc potential as the beam, this force can be expressed as (1) where and are the voltages applied to the electrode and conductive resonator beam, respectively, is the input electrode-to-resonator capacitance, which is a function of both displacement and time , and is the effective change in resonator-to-electrode capacitance per unit displacement, given by (2) shown at the bottom of the page, where is the total resonator stiffness (including both mechanical and electrical components) at location , is evaluated at , is a function describing the mode shape of the beam during resonance, is the permittivity in vacuum, and geometric variables are defined in Figs. 1(b) and 2.…”

“…In particular, the new formulation for the integrated and the use of an effective thickness contribute positively to the degree of matching seen between theory and measurement. Given that the analytical formulation of this work predicts noise figures on the order of 5 dB in properly operated mixlers, such devices have great potential for use in paradigm-shifting MEMS-based transceiver architectures aimed at enhancing communication robustness and lowering RF power consumption [1].…”

“…Recent advances in micromachining technologies that yield high-, high frequency, micromechanical (" mechanical") resonators [1]- [3] may now offer a method for combining both of these functions into a single passive, microscale device that eliminates mixer-to-filter connection losses. This paper reports on such a device, comprised of interlinked micromechanical resonators with capacitive mixer transducers, that downconverts radio frequency (RF) signals from 200 MHz down to a 37-MHz intermediate frequency (IF), then performs high-filtering, all with less than 13 dB of combined mixing conversion and filter insertion loss, and with ideally zero dc power consumption [4].…”

Modeling and characterization of three kinds of MEMS resonators fabricated with a thick polysilicon technology

“…MEMS resonators have been proposed as fundamental components for RF filters, mixers and oscillators [1]. The use of such devices as frequency references for RF communication systems is very attractive.…”