An ultrasound source based on a micro-machined electromechanical resonator

Micro-machined membranes can be excited by heating resistors to emit ultrasound. Such resonant structures have high quality factor and can be modeled electrically by a two-port resonant circuit. Using a Wheatstone bridge to sense the membrane buckling due ultrasound vibration, an electro-mechanical oscillator can be constructed by providing high gain at the resonant frequency between the Wheatstone bridge and the heating resistor of the membrane. An integrated circuit is presented here which implements the ultrasound source in a BiCMOS technology. Applications of such ultrasound sources include self-calibrated barrier detection and ranging systems