Miniature silicon micromachined ultrasonic point detectors for measurement of airborne radiated fields

Micromachining offers the ability to fabricate large numbers of miniature, near identical capacitive ultrasonic point detectors. Such point detectors have been fabricated using low-temperature silicon micromachining techniques, ranging in size from 100 μm to 5 mm square. Their sensitivity and angular response have been measured, and it is demonstrated that they can operate at frequencies in excess of 2 MHz, where attenuation in air becomes excessive, with an omni-directional response. Results from scanning the fields of air-coupled ultrasonic transducers will be presented, as will their use in arrays