外文翻译--数字技术在超声波传感器中的应用.doc

中英文翻译 英语原文 Application of Digital Techniques in Ultrasonic Sensor 1. INTRODUCTION It is necessary for a number of applications to perform distance measurements. Ultrasonic sensors are a state-of=the art choice to effectively solve this problem in different engineering fields, such as medical imaging, robot navigation, flow velocity, fluid level measurement and so on. Although different kinds of measuring systems and sensors have been used for the specific applications respectively, there are problems related to echo detection in every case: attenuation and beam spreading, presence of noise and interference, sensitivity to temperature and humidity, poor resolution. In many applications, the time elapsed between the stimulus ultrasonic wave and its echo is taken as the basis of the measurement, that is , the main operating principle is the estimation of the time of flight (ToF), the transmitting ultrasonic transducer transmits an ultrasonic pulse, the pulse propagates through the transmission medium (air, water, etc) and is echoed by a suitable reflector. The echo pulse is received by the receiving transducer, which may be the same transmitting transducer. So the distance from the transmitter to the reflector can be estimated indirectly by the formula: (1) where v is the propagation velocity of the ultrasonic wave in the medium. Another principle is the phase shift method. Here, the transmitter generates a continuous wave, who is reflected by an object, and whose echo is detected by a separate receiver. By computing the phase shift between the transmitted and the received continuous wave, the distance is evaluated to within a wavelength. Pulse-echo and continuous wave techniques are widely known as the represents of the two measuring principles. Continuous wave technique is more accurate, but more expensive due to complex hardware used to measure the phase and due to the difficulty in determining the number of integer wavelengths. A