| 摘要 |
PURPOSE:To improve the S/N ratio by accumulating angle data outputted synchronously with a prescribed clock pulse and outputting it as phase data, converting time series data consisting of amplitude data and phase data of a reference signal to an orthogonal coordinate system and generating a reference signal. CONSTITUTION:When amplitude R of a reference signal is set, this amplitude data R are supplied to a coordinate transformer 7. Also, angle data dthetai are supplied successively to a phase accumulator 6 synchronously with a clock pulse given from a control part 8, and phase data thetan are derived. Subsequently, the derived phase data thetan are supplied to the coordinate transformer 7, polar coordinate data consisting of the amplitude data R and the phase data thetan are converted to orthogonal coordinate data (Xout, Yout) and a reference signal is generated. That is, by adjusting a size of the inputted angle data dthetai, a frequency of an output signal can be set arbitrarily. In such a way, an ultrasonic receiving signal can be corrected with high accuracy, and the S/N ratio is improved. |
