Reduction of Time Quantization Errors in a Phased Array Transducer by Fast Reading of Digital RAM

Abstract

The degradation of focused sound beam due to the quantization errors for time delay in a phased array transducer is numerically investigated. Improvement of such degradation was made by developing a delayed phase generator capable of short time quantization. This method is based on the high-speed reading of memorized data by means of parallel usage of conventional RAM. Such a system approaches a variable delay of from zero to 2.4 µsec with the quantized unit of 23.5 nsec. Experiments demonstrated excellent convergence and reduction of off-axis response in focused beam patterns.