An experimental single-sideband acoustical re-injection test method for Doppler systems

An experimental acoustical re-injection system based on a wideband single-sideband generator has been developed. This has been used to present a clinical Doppler system with a simulated Doppler shift, as would be obtained from a unidirectional moving reflector. Development of this approach should permit independent electronic testing of forward and reverse channels, including mean and peak frequency calculations and measurement of channel separation. Sideband suppression of 28 dB minimum has been obtained for a range of ultrasound frequencies from 2.5 MHz to 10 MHz and audio frequency shifts up to 10 kHz.