RF-powered micromechanical clock generator

Abstract

A micromechanical circuit has been demonstrated that harnesses resonant mechanical impact switching to convert received RF energy (at -58dBm) into a local 1-kHz clock output while consuming less than 17.5nW of local battery power, which is 57 times lower than the 1μW of a typical real-time clock (RTC). The principal enabler here is a micromechanical resonant switch (“resoswitch”) that first accepts incoming ASK or FSK clock-modulated RF energy at a carrier frequency, filters it to remove unwanted interferers, provides power gain via resonant impact switching, and finally envelop detects impact impulses to demodulate and recover the clock waveform from the carrier. Since the resulting time domain waveform derives from the presumably very stable clock signal that originally modulated the RF carrier, the resulting local clock can share its accuracy. By dispensing with the need for a positive feedback sustaining amplifier, such a 1-kHz RF-powered mechanical clock generator driving an on-chip inverter gate capacitance of 5fF can potentially operate with only 5pW of battery power, which is 200,000 times lower than the typical RTC! Using an off-chip inverter with 17.5pF of effective capacitance, the current laboratory demonstration at 1-kHz consumes a still tiny 17.5nW.