| 摘要 |
<p>DOPPLER SIGNAL FREQUENCY CONVERTER A Doppler signal frequency converter for use in an apparatus used to detect and measure the velocity of movement of an object by picking up the reflections of ultrasonic waves beamed at the subject of examination. The converter is provided with one or a plurality of complex signal converters, and a complex multiplier which computes the conjugate and complex products of the complex signals. The complex signal converter converts the Doppler signals to a plurality -- for example two -- complex signals which differ in frequency. By carrying out computations based on the real and imaginary parts of the complex signals, the conjugate and complex products of the two complex signals are obtained. These conjugate and complex products are Doppler signals having a frequency which enables a wide range of velocity components to be detected, the conjugate product enabling the velocity of a distant rapidly-moving object to be measured accurately, while the complex product provides accurate measurement of the velocity of a slowmoving object.</p> |
