1997 Fiscal Year Final Research Report Summary
CODING FOR ARRAY SIGNAL USING MULTIDIMENSIONAL OVERSAMPLING TECHNIQUES
| Project/Area Number |
08650476
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
計測・制御工学
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| Research Institution | YAMAGATA UNIVERSITY |
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Principal Investigator |
TAMURA Yasutaka Yamagata University, Graduate School of Engineering, Associate Professor, 工学研究科, 助教授 (40171904)
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| Co-Investigator(Kenkyū-buntansha) |
AKATSUKA Takao Yamagata University, Faculty of Engineering, Professor, 工学部, 教授 (80091875)
KOYAMA Kiyohito Yamagata University, Faculty of Engineering, Professor, 工学部, 教授 (60007218)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Multidimensional signal Processing / Array signal processinng / 2-D DELTASIGMA-modulation / Wavefront generation / Piezoelectric polymer film |
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| Research Abstract |
We have proposed a new digital to analog conversion technique for acoustical transducer array. This technique utilizes the multidimensional band-limited property of array signals. Using the technique, a large dynamic-range wavefront is converted to multiple 1-bit waveforms which are oversampled temporally and spatially.
Following results are obtained :
1.We have proposed an oversampling technique using two dimensional DELTASIGMA-modulation for 1-D or 2-D transducer arrays. The stability of 2-D first-order DELTASIGMA-modulation os confirmed. We have clarified the relation between the SN ratio and the parameters of the 2-D DELTASIGMA-modulation, such as sampling frequency and array intervals. The SN ratio increases 9dB for doubling the spatial or temporal sampling frequency.
We have developed coding methods for matrix array, circular array and annular array.
2.We have constructed a trial DA conversion system for acoustical transducer array. This system consists of 64ch digital pattern generator and array of switching amplifiers. The amplifiers are directly controlled by digital pattern signal. The output range is 2 Vpp to 100Vpp. The switching frequency range is lKHz to 10MHz.
3.An ultrasonic array transducer was constructed by laminating P (VDF-TrFE) copolymer films with pattern electrode on a printed circuit board. The airborne dynamic-speaker array was also constructed.
4.A focused acoustical beam was generated by the proposed system. The maximum error of the directivity was 0.3%, and the SN ratio of observed waveform at the focal point was 80dB (over-sampling ratio is 16 for space, 16 for time). The spherical wave was also generated using the annular array.
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