Metal micromechanical filter-power amplifier utilizing a displacement-amplifying resonant switch

Abstract

Power gain up to 13.8 dB has been generated by a 23-MHz switched-mode power amplifier circuit employing an Al metal micromechanical slotted resonant switch (a.k.a., resoswitch). Here, slots in the resoswitch structure that amplify displacement along a chosen axis similar to that of [1] are key to preventing input axis impacts that plagued a previous such power amplifying resonant switch [2]. In addition, the use of a low temperature Al surface-micromachining process to fabricate the switch allows this PA to be integrated directly over advanced CMOS. This work demonstrates for the first time RF power gain via a metal micromechanical displacement-amplifying resonant switch, and in doing so inches this technology towards not only the possibility of near 100% efficient power gain when used in a Class-E configuration [3] in RF transmitters, but also realization of a channel-selecting filter-LNA function that could substantially lower receive path power consumption.

A CMOS-MEMS clamped–clamped beam displacement amplifier for resonant switch applications

“…Nevertheless, operating at frequencies of kHz to several MHz range suits well for low-data rate sensor applications that resoswitch-embedded zero-quiescent power receivers aim for [4]. In addition, while the displacement amplifiers demonstrated in [1, 2, 10] exhibits Q's higher than that in [3] and this work, they will likely suffer Q degradation once been implemented in metal material. While a higher displacement gain is always welcome, the overall output displacement magnitude decreases as the displacement gain increases (see figure 12), implying that a higher actuation voltage is needed.…”

“…Micromechanical resonant switches (aka 'resoswitches') have been demonstrated as a key component in the realization of zero-quiescent power communication receivers [3,4]. In particular, unlike conventional transistor-based receivers, resoswitch-embedded receivers could dispense with the need for standby power of the RF front-end that permits the receivers remain turned-on at all times without draining the battery while awaiting for valid interrogating signals.…”

“…Otherwise, the (high) bias voltage on the input electrodes would cause a large electrical short current that leads to device failure. To achieve displacement gain, several techniques have been demonstrated, including directional stiffness engineering slots [1,3], energy-sharing disk arrays [2], and high Q-preserving directional stiffness geometry [10]. Although exhibiting relatively high Q, some of the demonstrated displacement amplifiers require further process modification to metalize structure/contact to reducing contact resistance, with which Q is subject to degradation due to material limitation [3].…”

“…To achieve displacement gain, several techniques have been demonstrated, including directional stiffness engineering slots [1,3], energy-sharing disk arrays [2], and high Q-preserving directional stiffness geometry [10]. Although exhibiting relatively high Q, some of the demonstrated displacement amplifiers require further process modification to metalize structure/contact to reducing contact resistance, with which Q is subject to degradation due to material limitation [3]. In addition, these displacementamplifying devices rely on complex fabrication processes, to the authors' best knowledge, available yet only in university research cleanroom that would need vast investment of time and money to evolve into mass production.…”

“…In addition, the CMOS-MEMS process platform allows MEMS devices to integrate directly with CMOS circuits that eliminates the parasitic capacitance, inductance, and resistance, which would otherwise exist in interconnects, bond pads and bonding wires. With minimized parasitic components, resoswitch-based amplifiers can further extend their operating frequencies [3].…”