DEVELOPMENT OF VERSATILE ARRAY SENSOR USING MULTIDIMENSIONAL SIGNAL PROCESSING

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A novel coding technique for acoustical transducer arrays was proposed. This technique utilizes the multidimensional signal processing and band-limited property of array signals. Using the technique, a encoded wave-front can be efficiently generated from the array with multiple 1-bit waveforms.Following results are obtained :1. A production process for ultrasonic array transducers constructed by laminating P (VDF-TrFE) copolymer films on patterned electrodes was developed. The 2-D array for a 3-D ultrasound imaging system was constructed. The fractional bandwidth of the array was over than 200% at center frequency of 3.5MHz.2. A signal processing LSI which converts a multiple coded wavefront to 1bit sequences is designed using VHDL language and FPGAs.3. The relation between the SN ratio and the parameters of the 2-D ΔΣ-modulation, such as sampling frequency and array intervals was clarified. A decimation technique to enlarge the interval of the elements of the arrays was proposed.4. A trial 3-D imaging system was constructed using the developed array and peripheral circuits. This system was able to reconstruct 3-D images of simple targets in water or agar functions. The performance of the system, intensities of generated wave-fronts, spatial resolutions and dynamic ranges are investigated.The spatial resolutions were coincide with the theoretical values.This system consists of 16th digital pattern generator and array of switching amplifiers. While the amplifiers are directly controlled by digital pattern signal, the view angle and the dynamic range were low. This problem should be overcome by increased number of array elements and optimal image reconstruction algorithm. Finally, the new idea to reduced the complexity of high density array has been obtained.