A fully-integrated self-calibrating transmitter/receiver IC for an ultrasound presence detector microsystem

There are a variety of applications in industrial automation where ultrasound can be used to detect the presence of (count) transparent or light sensitive objects (or liquid), such as ampoules or photographic films. Dusty or smoking surroundings are also places where ultrasound is used for presence detection instead of light. In applications where detection must take place in a small enclosure, such as counting drops of medicine in a drip, a miniaturized sensor is desirable. In such applications a fully-integrated ultrasound microsystem in a IC-compatible technology has an advantage in both size and cost. This fully-integrated IC, is configurable either as a transmitter or as a receiver, to bind two micromachined ultrasound membranes into a general purpose barrier-detecting microsystem. Miniaturized microsystems today are usually designed to take full advantage of the rapid progress of both the integrated sensor and integrated circuit technologies. A trend in such systems is to integrate sensors, in this case the ultrasound transducer, using the same technology as the integrated circuits. The advantage of realizing sensors and circuits on the same chip is to tap the strong manufacturing base of the IC technologies perfected in low-cost mass production. The ultrasound transducer with which this circuit forms a microsystem is a silicon membrane that can be micromachined out of a BiCMOS technology using one simple post-processing step. The complete system is in 3 /spl mu/m BiCMOS and has a maximum range of 10 cm.