Multiple frequency annular transducer array and system

摘要: A scanning system having a variable field of imaging uses transducer array including central element and one or more annular elements concentric therewith. The is energized at first frequency for near imaging, the are lower frequencies intermediate far imaging. Electrical signals generated by in response to reflected ultrasonic waves demodulated form in-phase quadrature phase signals, electrical then summed provide an enhanced image signal.