Pub Date : 2014-10-23DOI: 10.1109/ULTSYM.2014.0387
T. Ishii, Seiya Mochizuki, Tsuyoshi Shimizu
A bolt-clamped Langevin transducer with segmented electrodes is designed and fabricated. This transducer can excite not only longitudinal vibration mode but also bending vibration modes. Therefore the ultrasonic motor using these two multi-mode Langevin transducers can excite necessary vibration modes for multi-degree of freedom motions. The diameter and the length of the transducer fabricated in this research is 15 mm and 25.4 mm, respectively. The structure, driving principle and application of the transducer are discussed.
{"title":"Multi-mode Langevin Transducers for π-shaped ultrasonic motor with multi-degree of freedom.","authors":"T. Ishii, Seiya Mochizuki, Tsuyoshi Shimizu","doi":"10.1109/ULTSYM.2014.0387","DOIUrl":"https://doi.org/10.1109/ULTSYM.2014.0387","url":null,"abstract":"A bolt-clamped Langevin transducer with segmented electrodes is designed and fabricated. This transducer can excite not only longitudinal vibration mode but also bending vibration modes. Therefore the ultrasonic motor using these two multi-mode Langevin transducers can excite necessary vibration modes for multi-degree of freedom motions. The diameter and the length of the transducer fabricated in this research is 15 mm and 25.4 mm, respectively. The structure, driving principle and application of the transducer are discussed.","PeriodicalId":153901,"journal":{"name":"2014 IEEE International Ultrasonics Symposium","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130369167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-23DOI: 10.1109/ULTSYM.2014.0252
G. Waag, Petter Norli, L. Hoff
Air-coupled ultrasound (ACU) is an attractive option in non-destructive testing when the target of inspection is affected by the coupling liquid, or when the target is too big to be immersed in the coupling liquid. The challenge with ACU is the huge impedance mismatch between the air and the target. In pulse-echo measurements this mismatch causes a huge difference in level between the first reflection, from the air-target interface, and the tail, from multiple reflections inside the target. This can cause the first reflection to mask the tail signal. An analytical model for pulse-echo and through-transmission measurements has been developed by using the angular spectrum method. This model was verified against measurements in a water tank in a through-transmission setup. The model was then used to model echoes from a steel plate in air. These studies show that moving the receiving transducer laterally away from the acoustic axis of the transmitter will reduce the level of the first reflection more than the level of the tail of the signal. Hence, to avoid masking the signals from the interior of the plate by the strong reflection from the air-steel interface, the receiving transducer should be placed off the acoustic axis of the transmitter. Displacing the receiver from the transmitter acoustical axis represents a new challenge, as dispersion in the plate could potentially make the measured spectra difficult to interpret. Our studies show that the dispersion does not interefere with the resonance frequencies, as the spectral peaks are insensitive to the start of the time window the spectra are calculated from. This makes the computation of the thickness robust and simple, as the half wave resonance frequencies can be used.
{"title":"Feasibility of pulse-echo thickness measurements in air with a laterally displaced receiver","authors":"G. Waag, Petter Norli, L. Hoff","doi":"10.1109/ULTSYM.2014.0252","DOIUrl":"https://doi.org/10.1109/ULTSYM.2014.0252","url":null,"abstract":"Air-coupled ultrasound (ACU) is an attractive option in non-destructive testing when the target of inspection is affected by the coupling liquid, or when the target is too big to be immersed in the coupling liquid. The challenge with ACU is the huge impedance mismatch between the air and the target. In pulse-echo measurements this mismatch causes a huge difference in level between the first reflection, from the air-target interface, and the tail, from multiple reflections inside the target. This can cause the first reflection to mask the tail signal. An analytical model for pulse-echo and through-transmission measurements has been developed by using the angular spectrum method. This model was verified against measurements in a water tank in a through-transmission setup. The model was then used to model echoes from a steel plate in air. These studies show that moving the receiving transducer laterally away from the acoustic axis of the transmitter will reduce the level of the first reflection more than the level of the tail of the signal. Hence, to avoid masking the signals from the interior of the plate by the strong reflection from the air-steel interface, the receiving transducer should be placed off the acoustic axis of the transmitter. Displacing the receiver from the transmitter acoustical axis represents a new challenge, as dispersion in the plate could potentially make the measured spectra difficult to interpret. Our studies show that the dispersion does not interefere with the resonance frequencies, as the spectral peaks are insensitive to the start of the time window the spectra are calculated from. This makes the computation of the thickness robust and simple, as the half wave resonance frequencies can be used.","PeriodicalId":153901,"journal":{"name":"2014 IEEE International Ultrasonics Symposium","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123929900","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-23DOI: 10.1109/ULTSYM.2014.0336
C. M. Grunsteidl, I. Veres, T. Berer, P. Burgholzer
We use a spatial light modulator to shape the excitation laser spot of a laser-ultrasound system. With periodic excitation patterns we are able to excite ultrasound waves of a particular, single wavelength. In combination with temporal intensity modulation of the excitation laser, only waves of specific wavelength and frequency are generated. We experimentally validated this principle and applied the method to scan the two-dimensional dispersion relation of surface acoustic waves on coated samples. Results obtained with different periodic patterns were compared. We also used the setup to produce laser spots of different size to study the excitability of Lamb modes.
{"title":"Application of SLM generated patterns for laser-ultrasound","authors":"C. M. Grunsteidl, I. Veres, T. Berer, P. Burgholzer","doi":"10.1109/ULTSYM.2014.0336","DOIUrl":"https://doi.org/10.1109/ULTSYM.2014.0336","url":null,"abstract":"We use a spatial light modulator to shape the excitation laser spot of a laser-ultrasound system. With periodic excitation patterns we are able to excite ultrasound waves of a particular, single wavelength. In combination with temporal intensity modulation of the excitation laser, only waves of specific wavelength and frequency are generated. We experimentally validated this principle and applied the method to scan the two-dimensional dispersion relation of surface acoustic waves on coated samples. Results obtained with different periodic patterns were compared. We also used the setup to produce laser spots of different size to study the excitability of Lamb modes.","PeriodicalId":153901,"journal":{"name":"2014 IEEE International Ultrasonics Symposium","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123719372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-23DOI: 10.1109/ULTSYM.2014.0193
M. Mayer, W. Ruile, John Johnson, J. Kiwitt, Romeo San Jose, E. Schmidhammer, I. Bleyl, K. Wagner, A. Mayer, E. Mayer
Recently a P-matrix and COM formalism was presented, which predicts third order intermodulation (IMD3) and triple beat with good accuracy and needs only a single nonlinearity constant. This formalism describes frequency dependence correctly. In this work the dependence of this nonlinearity constant on metalization ratio is investigated for aluminum metalization on LiTaO3 (YXl)/42°. By comparison to test devices the nonlinearity constant is shown to be largely independent of metalization ratio. The nonlinear effect, however, strongly depends on metalization ratio, which is well described by the model. The linearity of a duplexer is optimized by reduction of metalization ratio and redesign of Tx branch topology.
{"title":"Application of a rigorous nonlinear P-matrix method to the simulation of third order intermodulation in test devices and duplexers","authors":"M. Mayer, W. Ruile, John Johnson, J. Kiwitt, Romeo San Jose, E. Schmidhammer, I. Bleyl, K. Wagner, A. Mayer, E. Mayer","doi":"10.1109/ULTSYM.2014.0193","DOIUrl":"https://doi.org/10.1109/ULTSYM.2014.0193","url":null,"abstract":"Recently a P-matrix and COM formalism was presented, which predicts third order intermodulation (IMD3) and triple beat with good accuracy and needs only a single nonlinearity constant. This formalism describes frequency dependence correctly. In this work the dependence of this nonlinearity constant on metalization ratio is investigated for aluminum metalization on LiTaO3 (YXl)/42°. By comparison to test devices the nonlinearity constant is shown to be largely independent of metalization ratio. The nonlinear effect, however, strongly depends on metalization ratio, which is well described by the model. The linearity of a duplexer is optimized by reduction of metalization ratio and redesign of Tx branch topology.","PeriodicalId":153901,"journal":{"name":"2014 IEEE International Ultrasonics Symposium","volume":"53 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114117079","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-23DOI: 10.1109/ULTSYM.2014.0595
Xiao Wang, M. S. Salamat, T. Varghese, R. Dempsey
Most atherosclerotic plaques are heterogeneous, making it difficult to classify them in the clinic as calcified or lipidic plaques. We propose a novel approach to characterize localized plaque regions with different tissue types. We will compare and correlate calcified, fibrous and lipid regions within heterogeneous plaque using a one-to-one registration with histology and quantitative ultrasound imaging (QUS). Atherosclerotic plaque excised during a carotid endarterectomy procedure was imaged ex vivo using a VisualSonics Vevo 770 ultrasound system. Attenuation coefficient images were obtained from three-dimensional (3D) radiofrequency data collected and rendered into a 3D volume. Fixed plaque tissue was then longitudinally sectioned with thickness of 5 μm, and sections separated by 100 μm were utilized. Two-dimensional histopathology images were digitized using a PathScan Enabler IV, registered and reconstructed into a 3D volume using Matlab. Different regions such as the lumen, calcified, lipid and fibrous regions were segmented by a pathologist and digitally color-coded into the 3D histology volumes. Similar tissue types from the 3D histology volume were then compared to the estimated 3D attenuation coefficient obtained using quantitative ultrasound methods. Our results indicate that calcified, lipid and fibrous regions in the two volumes demonstrate good correlation. Calcified regions delineated on the histology volume correspond to high attenuation coefficient regions (2.45 dB/cm/MHz) in the 3D attenuation coefficient volume, while lipid regions tend to have lower attenuation coefficient values (1.50 dB/cm/MHz). Fibrous regions in histology, correlate to the lowest attenuation coefficient value (0.83 dB/cm/MHz). Our work demonstrates a direct correlation between histology and ultrasound quantitative imaging characterization of plaque. Using 3D histology volumes, different tissue composition within the plaque can be better identified and characterized.
{"title":"Carotid plaque characterization with histology and quantitative ultrasound","authors":"Xiao Wang, M. S. Salamat, T. Varghese, R. Dempsey","doi":"10.1109/ULTSYM.2014.0595","DOIUrl":"https://doi.org/10.1109/ULTSYM.2014.0595","url":null,"abstract":"Most atherosclerotic plaques are heterogeneous, making it difficult to classify them in the clinic as calcified or lipidic plaques. We propose a novel approach to characterize localized plaque regions with different tissue types. We will compare and correlate calcified, fibrous and lipid regions within heterogeneous plaque using a one-to-one registration with histology and quantitative ultrasound imaging (QUS). Atherosclerotic plaque excised during a carotid endarterectomy procedure was imaged ex vivo using a VisualSonics Vevo 770 ultrasound system. Attenuation coefficient images were obtained from three-dimensional (3D) radiofrequency data collected and rendered into a 3D volume. Fixed plaque tissue was then longitudinally sectioned with thickness of 5 μm, and sections separated by 100 μm were utilized. Two-dimensional histopathology images were digitized using a PathScan Enabler IV, registered and reconstructed into a 3D volume using Matlab. Different regions such as the lumen, calcified, lipid and fibrous regions were segmented by a pathologist and digitally color-coded into the 3D histology volumes. Similar tissue types from the 3D histology volume were then compared to the estimated 3D attenuation coefficient obtained using quantitative ultrasound methods. Our results indicate that calcified, lipid and fibrous regions in the two volumes demonstrate good correlation. Calcified regions delineated on the histology volume correspond to high attenuation coefficient regions (2.45 dB/cm/MHz) in the 3D attenuation coefficient volume, while lipid regions tend to have lower attenuation coefficient values (1.50 dB/cm/MHz). Fibrous regions in histology, correlate to the lowest attenuation coefficient value (0.83 dB/cm/MHz). Our work demonstrates a direct correlation between histology and ultrasound quantitative imaging characterization of plaque. Using 3D histology volumes, different tissue composition within the plaque can be better identified and characterized.","PeriodicalId":153901,"journal":{"name":"2014 IEEE International Ultrasonics Symposium","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121523474","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-23DOI: 10.1109/ULTSYM.2014.0066
B. Sinha, E. Simsek
A new technique uses time-lapse borehole sonic data acquired in a vertical borehole parallel to the X3-axis to estimate changes in formation stresses caused by reservoir depletion or injection. A pre-production baseline survey acquires sonic data in an open or cased hole along with estimates of reservoir pressure, overburden and minimum horizontal stresses. After years of depletion or injection, a monitor survey acquires sonic data in an observation well. Both sonic datasets are processed to obtain the borehole Stoneley and cross-dipole dispersions. An inversion algorithm inverts the measured Stoneley dispersion to estimate the far-field shear modulus C66 in the borehole cross-sectional plane. The shear moduli C44 and C55 in the two orthogonal borehole axial planes are obtained directly from the low-frequency asymptotes of the two cross-line flexural dispersions. Differences in the three shear moduli from the baseline survey yield the maximum horizontal stress magnitude and an acoustoelastic coefficient using the estimated pore pressure, overburden and minimum horizontal stresses. The three far-field shear moduli in the three orthogonal planes are also obtained from the subsequent monitor survey. This algorithm uses the acoustoelastic coefficient from the baseline survey and the three shear moduli after depletion or injection to estimate changes in the maximum and minimum horizontal stress magnitudes caused by reservoir pressure changes.
{"title":"Estimation of depletion or injection induced changes in reservoir stresses using time-lapse sonic data","authors":"B. Sinha, E. Simsek","doi":"10.1109/ULTSYM.2014.0066","DOIUrl":"https://doi.org/10.1109/ULTSYM.2014.0066","url":null,"abstract":"A new technique uses time-lapse borehole sonic data acquired in a vertical borehole parallel to the X3-axis to estimate changes in formation stresses caused by reservoir depletion or injection. A pre-production baseline survey acquires sonic data in an open or cased hole along with estimates of reservoir pressure, overburden and minimum horizontal stresses. After years of depletion or injection, a monitor survey acquires sonic data in an observation well. Both sonic datasets are processed to obtain the borehole Stoneley and cross-dipole dispersions. An inversion algorithm inverts the measured Stoneley dispersion to estimate the far-field shear modulus C66 in the borehole cross-sectional plane. The shear moduli C44 and C55 in the two orthogonal borehole axial planes are obtained directly from the low-frequency asymptotes of the two cross-line flexural dispersions. Differences in the three shear moduli from the baseline survey yield the maximum horizontal stress magnitude and an acoustoelastic coefficient using the estimated pore pressure, overburden and minimum horizontal stresses. The three far-field shear moduli in the three orthogonal planes are also obtained from the subsequent monitor survey. This algorithm uses the acoustoelastic coefficient from the baseline survey and the three shear moduli after depletion or injection to estimate changes in the maximum and minimum horizontal stress magnitudes caused by reservoir pressure changes.","PeriodicalId":153901,"journal":{"name":"2014 IEEE International Ultrasonics Symposium","volume":"98 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126382240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-23DOI: 10.1109/ULTSYM.2014.0373
J. Kondoh, T. Nozawa
If an online and real-time measurement system is realized using a shear horizontal surface acoustic wave (SH-SAW), the SH-SAW sensor can be used in many fields. As detection principle of the SH-SAW is relative measurement, the SH-SAW sensor needs reference liquid. When the SH-SAW sensor is installed into a flow tube, it is difficult to measure reference liquid. In this paper, we discuss methanol concentration measurement method of a direct methanol fuel cell using the SH-SAW sensor.
{"title":"Online real-time monitoring method of methanol concentration for direct methanol fuel cell using shear horizontal surface acoustic wave","authors":"J. Kondoh, T. Nozawa","doi":"10.1109/ULTSYM.2014.0373","DOIUrl":"https://doi.org/10.1109/ULTSYM.2014.0373","url":null,"abstract":"If an online and real-time measurement system is realized using a shear horizontal surface acoustic wave (SH-SAW), the SH-SAW sensor can be used in many fields. As detection principle of the SH-SAW is relative measurement, the SH-SAW sensor needs reference liquid. When the SH-SAW sensor is installed into a flow tube, it is difficult to measure reference liquid. In this paper, we discuss methanol concentration measurement method of a direct methanol fuel cell using the SH-SAW sensor.","PeriodicalId":153901,"journal":{"name":"2014 IEEE International Ultrasonics Symposium","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125725938","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-23DOI: 10.1109/ULTSYM.2014.0341
Shiwei Wu, Keji Yang
The synthetic aperture focusing technique (SAFT) has been widely used for detection and sizing of material discontinuities (flaws) in ultrasonic nondestructive testing (NDT) because of its significant improvements in lateral resolution. But the efforts of researching on SAFT for irregularly multilayered objects that are inhomogeneous in both the vertical and lateral directions are relatively insufficient. In this paper, a new non-recursive synthetic aperture imaging algorithm, called modified direct Fourier migration (M-DFM), is proposed to deal with such irregularly multilayered situations. The derivation of the algorithm was inspired by reformulating Stolt f-k migration as a nonstationary filter, which could be extended to generally multilayered cases by the root-mean-square velocity. The experiment shows that the proposed algorithm is well suited for restoring images of regularly multilayered objects with almost the same accuracy as phase shift migration (PSM) which has recently succeeded in planar layered structures. And the performance of the proposed algorithm is also evaluated using immersion test data from a steel block with a convex interface and a side drilled hole, in this way investigating the method's capability of improving the lateral resolution of flaws detection in irregularly multilayered media. Furthermore, the proposed algorithm provides a non-recursive means to recover the images by performing a single 2-D inverse Fourier transform on the filtered spectrums rather than by recursive wave field extrapolation needed for PSM.
{"title":"Non-recursive synthetic aperture imaging for multilayered media with irregular boundary","authors":"Shiwei Wu, Keji Yang","doi":"10.1109/ULTSYM.2014.0341","DOIUrl":"https://doi.org/10.1109/ULTSYM.2014.0341","url":null,"abstract":"The synthetic aperture focusing technique (SAFT) has been widely used for detection and sizing of material discontinuities (flaws) in ultrasonic nondestructive testing (NDT) because of its significant improvements in lateral resolution. But the efforts of researching on SAFT for irregularly multilayered objects that are inhomogeneous in both the vertical and lateral directions are relatively insufficient. In this paper, a new non-recursive synthetic aperture imaging algorithm, called modified direct Fourier migration (M-DFM), is proposed to deal with such irregularly multilayered situations. The derivation of the algorithm was inspired by reformulating Stolt f-k migration as a nonstationary filter, which could be extended to generally multilayered cases by the root-mean-square velocity. The experiment shows that the proposed algorithm is well suited for restoring images of regularly multilayered objects with almost the same accuracy as phase shift migration (PSM) which has recently succeeded in planar layered structures. And the performance of the proposed algorithm is also evaluated using immersion test data from a steel block with a convex interface and a side drilled hole, in this way investigating the method's capability of improving the lateral resolution of flaws detection in irregularly multilayered media. Furthermore, the proposed algorithm provides a non-recursive means to recover the images by performing a single 2-D inverse Fourier transform on the filtered spectrums rather than by recursive wave field extrapolation needed for PSM.","PeriodicalId":153901,"journal":{"name":"2014 IEEE International Ultrasonics Symposium","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127951753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-23DOI: 10.1109/ULTSYM.2014.0648
A. Lei, Søren Elmin Diederichsen, M. F. la Cour, M. Stuart, T. Christiansen, J. Jensen, E. Thomsen
This work presents a dimensional scaling study using numerical simulations, where gap height and plate thickness of a CMUT cell is varied, while the lateral plate dimension is adjusted to maintain a constant transmit immersion center frequency of 5 MHz. Two cell configurations have been simulated, one with a single square cell and one with an infinite array of square cells. It is shown how the radiation impedance from neighboring cells has a significant impact on the design process. For transmit optimization, both plate dimensions and gap height should be increased. For receive mode, the gap height should be increased while the effect of plate dimensions is ambiguous depending on if the array design is closest to a single cell or infinite array of cells. The findings of the simulations are verified by acoustical measurements on two CMUT arrays with different plate dimensions.
{"title":"Dimensional scaling for optimized CMUT operations","authors":"A. Lei, Søren Elmin Diederichsen, M. F. la Cour, M. Stuart, T. Christiansen, J. Jensen, E. Thomsen","doi":"10.1109/ULTSYM.2014.0648","DOIUrl":"https://doi.org/10.1109/ULTSYM.2014.0648","url":null,"abstract":"This work presents a dimensional scaling study using numerical simulations, where gap height and plate thickness of a CMUT cell is varied, while the lateral plate dimension is adjusted to maintain a constant transmit immersion center frequency of 5 MHz. Two cell configurations have been simulated, one with a single square cell and one with an infinite array of square cells. It is shown how the radiation impedance from neighboring cells has a significant impact on the design process. For transmit optimization, both plate dimensions and gap height should be increased. For receive mode, the gap height should be increased while the effect of plate dimensions is ambiguous depending on if the array design is closest to a single cell or infinite array of cells. The findings of the simulations are verified by acoustical measurements on two CMUT arrays with different plate dimensions.","PeriodicalId":153901,"journal":{"name":"2014 IEEE International Ultrasonics Symposium","volume":"110 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115782015","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-23DOI: 10.1109/ULTSYM.2014.0192
R. Nakagawa, Haruki Kyoya, H. Shimizu, T. Kihara
Linearity performances are getting one of the most important characteristics of surface acoustic wave (SAW) duplexers because nonlinear signals generated in RF front-end of cellar phone handsets deteriorate the receiver sensitivities significantly. In this paper, the generation mechanisms of the 2nd order nonlinear signals of SAW resonators/duplexers on a 42°Y-X LiTaO3 substrate and an effective suppression method for them are discussed. The crystalline asymmetry properties of substrates are focused on as the one possibility of the occurrence factor of the 2nd order nonlinear signals. Additionally, based on this hypothesis, an interdigital transducer (IDT) design which realizes the cancellation of the crystalline asymmetry effect is proposed to improve the linearity. As the result, the 2nd order harmonics level of the one-port SAWresonators and the 2nd order intermodulation distortion (IMD2) levels of the SAW duplexers have been improved up to about 25dBm and 20dBm, respectively.
{"title":"Effective suppression method for 2nd nonlinear signals of SAW devices","authors":"R. Nakagawa, Haruki Kyoya, H. Shimizu, T. Kihara","doi":"10.1109/ULTSYM.2014.0192","DOIUrl":"https://doi.org/10.1109/ULTSYM.2014.0192","url":null,"abstract":"Linearity performances are getting one of the most important characteristics of surface acoustic wave (SAW) duplexers because nonlinear signals generated in RF front-end of cellar phone handsets deteriorate the receiver sensitivities significantly. In this paper, the generation mechanisms of the 2nd order nonlinear signals of SAW resonators/duplexers on a 42°Y-X LiTaO3 substrate and an effective suppression method for them are discussed. The crystalline asymmetry properties of substrates are focused on as the one possibility of the occurrence factor of the 2nd order nonlinear signals. Additionally, based on this hypothesis, an interdigital transducer (IDT) design which realizes the cancellation of the crystalline asymmetry effect is proposed to improve the linearity. As the result, the 2nd order harmonics level of the one-port SAWresonators and the 2nd order intermodulation distortion (IMD2) levels of the SAW duplexers have been improved up to about 25dBm and 20dBm, respectively.","PeriodicalId":153901,"journal":{"name":"2014 IEEE International Ultrasonics Symposium","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132500487","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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