Output bandwidth enhancement of a pulsed ultrasound system using a flat envelope and compensated frequency-modulated input signal: Theory and experimental applications

摘要

A pre-filtering technique was used with an ultrasound transmit-receive system to increase the output signal bandwidth beyond that obtained with either conventional pulsing or linear frequency modulated (LFM) input signals. A compensated frequency modulated (CFM) excitation signal, with flat envelope and non-uniformly time-spaced amounts of spectral energy density, was applied to the system input. Two experiments were conducted to demonstrate practical applications of the proposed technique. Initially, in comparison to the bandwidth of the output signal generated by a LFM excitation, the system output signal bandwidth tripled with a pair of transducers. In a second experiment, the attenuation coefficient of a viscous fluid was measured and compared with the theoretical (assessed) value. Measured values for the attenuation coefficient were within +/- 0.03 relative of the theoretical values. The CFM input signal was shown to have enough energy to produce a larger -6 dB bandwidth (three times more) compared to LFM signals. (C) 2015 Elsevier Ltd. All rights reserved.