Nonlinear generation of harmonic content within High Intensity Ultrasound signals using granular chains

Harput, Sevan; McLaughlan, James R.; Freear, Steven; Gélat, Pierre; Saffari, Nader; Yang, Jie; Akanji, Omololu; Thomas, Peter J.; Hutchins, David A.

doi:10.1109/ultsym.2015.0191

Cited by 3 publications

(3 citation statements)

References 13 publications

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“…It has already been demonstrated by Hutchins et al and Yang et al that it is possible to generate wideband impulses by coupling energy to harmonics from a fundamental ultrasonic frequency of 73 kHz [8]- [10]. Donahue et al and Harput et al presented generation of ultrasound waves in water by using a granular chain with a matching layer [11], [12]. The aim of this study is to incorporate the effect of a matching layer into an existing analytical model and an experimental setup to…”

Section: Introductionmentioning

confidence: 99%

Coupling of wideband impulses generated by granular chains into liquids for biomedical applications

Harput

Freear

Gélat

et al. 2016

2016 IEEE International Ultrasonics Symposium (IUS)

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Abstract-An ultrasonic transducer technology to generate wideband impulses using a one-dimensional chain of spheres was previously presented. The Hertzian contact between the spheres causes the nonlinearity of the system to increase, which transforms high amplitude narrowband sinusoidal input into a train of wideband impulses. Generation of short duration ultrasonic pulses is desirable both in diagnostic and therapeutic ultrasound. Nevertheless, the biggest challenge in terms of adaptation to biomedical ultrasound is the coupling of the ultrasonic energy into biological tissue.An analytical model was created to address the coupling issue. Effect of the matching layer was modelled as a flexible thin plate clamped from the edges. Model was verified against hydrophone measurements. Different coupling materials, such as glass, aluminium, acrylic, silicon rubber, and vitreous carbon, was analysed with this model. Results showed that soft matching layers such as acrylic and rubber inhibit the generation of higher order harmonics. Between the hard matching materials, vitreous carbon achieved the best results due to its acoustic impedance.

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Section: Introductionmentioning

confidence: 99%

Coupling of wideband impulses generated by granular chains into liquids for biomedical applications

Harput

Freear

Gélat

et al. 2016

2016 IEEE International Ultrasonics Symposium (IUS)

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“…for values of time between 25 s and 350 s in Fig. 2), the hydrophone measurement is contaminated by electromagnetic interference [9]. Additionally, as the acoustic pressure decays, the hydrophone measurement suffers from poor signal-to-noise ratio.…”

Section: B Experimental Measurementsmentioning

confidence: 99%

The dynamic excitation of a chain of pre-stressed spheres for biomedical ultrasound applications: Contact mechanics finite element analysis and validation

Gélat

Saffari

Hutchins

et al. 2015

2015 IEEE International Ultrasonics Symposium (IUS)

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“…The developed transducer is able to transform a narrow-band sinusoidal input force into a train of wideband impulses at ultrasonic frequencies. Donahue et al [17] and Harput et al [24,25] presented the generation of ultrasound waves in water by using a granular chain with a matching layer. However, neither of these studies analyzed the energy transfer from a chain of spheres into biological tissue in detail.…”

Section: Introductionmentioning

confidence: 99%

Generation of Ultrasound Pulses in Water Using Granular Chains with a Finite Matching Layer

et al. 2017

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Wave propagation in granular chains is subject to dispersive effects as well as nonlinear effects arising from the Hertzian contact law. This enables the formation of wideband pulses, which is a desirable feature in the context of diagnostic and therapeutic ultrasound applications. However, coupling of the ultrasonic energy from a chain of spheres into biological tissue is a big challenge. In order to improve the energy transfer efficiency into biological materials, a matching layer is required. A prototype device is designed to address this by using six aluminum spheres and a vitreous carbon matching layer. The matching layer and the precompression force are selected specifically to maximize the acoustic pressure in water and its bandwidth. The designed device generates a train of wideband ultrasonic pulses from a narrow-band input with a center frequency of 73 kHz. An analytical model is created to simulate the behavior of a matching layer as a flexible thin plate clamped from the edges. This model is then verified using free-field hydrophone measurements in water, which successfully predict the increased bandwidth by generation of harmonics. The shapes of the measured and predicted waveforms are compared by calculating the normalized cross-correlation, which shows 83% similarity between both. Since the generation of harmonics is of interest in this study, the total harmonic distortion (THD) and the −6-dB bandwidth of the signals are used to analyze signal fidelity between the hydrophone measurements and the model predictions. The acoustic signals in water have a root-mean-square THD of 73%, and the model predicts a root-mean-square THD of 78%. The −6-dB bandwidths of individual pulses measured by a hydrophone and predicted with the model are 280 and 252 kHz, respectively. At these high ultrasonic frequencies, it is an experimental demonstration of resonant chains operating in water with a matching layer.

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Nonlinear generation of harmonic content within High Intensity Ultrasound signals using granular chains

Cited by 3 publications

References 13 publications

Coupling of wideband impulses generated by granular chains into liquids for biomedical applications

Coupling of wideband impulses generated by granular chains into liquids for biomedical applications

The dynamic excitation of a chain of pre-stressed spheres for biomedical ultrasound applications: Contact mechanics finite element analysis and validation

Generation of Ultrasound Pulses in Water Using Granular Chains with a Finite Matching Layer

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