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. Author manuscript; available in PMC: 2015 Oct 1.
Published in final edited form as: IEEE Trans Ultrason Ferroelectr Freq Control. 2014 Oct;61(10):1698–1708. doi: 10.1109/TUFFC.2014.006502

Fig. 2.

Fig. 2

(a) An example of a nonlinearly distorted HIFU waveform. Frequency spectrum of a signal detected by the PCD transducer in polyacrylamide gel phantom before (b) and after (c) filtering. A combination of a band-pass filter (2.3 - 8.8MHz) and a notch shaped comb filter with a notch bandwidth of 100 kHz was applied to PCD signals in the frequency domain to suppress backscattered harmonics of the HIFU pulse and the ultraharmonics generated by stably oscillating bubbles.