Volterra Frequency Response Functions Analysis of Subharmonic Oscillations from Bubble

Subharmonic images are becoming interestingly in medical ultrasound, as the improvement of contrastto-tissue ratio (CTR). However, an important part for image enhancement is processing techniques. In this study, frequency response functions (FRFs) of multiple-input-multiple-output (MIMO) Volterra systems were used to investigate potentially possible in separating subharmonic frequency for the quality of the images. The motivation for this research is that Volterra filter application in separating subharmonic component need analysis which is FRFs (e.g. linear and quadratic Volterra kernels). The theme in this study is the analysis of FRFs to investigate possible subharmonic filtering of bubble frequency. Material of an experimental subharmonic represented by Churchs model was the excitation amplitude pressure 0.6 MPa at twice of resonance frequency. Simulation results of Volterra kernel are analyzed and displayed in graphs of FRFs. In conclusion, this study demonstrated the cause of multi-frequency response of FRFs and the direction in filtering the subharmonic with Volterra filter.