DEVELOPMENT OF SIGNAL PROCESSING ULTRASONIC ARRAY-SENSOR

点击翻译按钮获取中文摘要

We have developed a ultrasonic array-sensor, encoding sperture (EA), which multiplex spatially distributed information of wavefront. We can control the signal processing function by changing transmitted waveforms.Following results are obtained :1. We have constructed the data acquisition system. A-2ch EA transducer was constructed by using P (VDF-TrFE) copolymer films according to an M-sequence. The array was constructed with a transmitter on the same film, then the positioning problem of the transducers are reducod. The electrostatic sealed significantly reduced the noise, and no averaging was needed.2. A new imaging operator was developed by SVD of the transfer matrix in the frequency domain. The calibration data is obtained using actual output waveforms corresponding to a target scanned along lines. A point target can be imaged with reasonable quality by the operator. The proposed technique provided images with high quality by a small number of data acquisitions and by a small scanning range of the transducer. The relative level of averaged artifacts is reduced by -7dB.3. A new selective focusing method is proposed for echolocation system. Transducers are constructed to a liner array coded with a binary sequence. The array converts a wavefront to a serial signal. Selective focusing is realized by transmitting a time-reversal waveforms. This enables us to control a focusing pattern with serial transmitting singal. The technique was applied to the adaptive focusing which select the object of maximum target strength. The unneeded signal level was reduced to-4dB by two iteration, this level, however, was increased with iteration number over two.