In the process of piezoelectric ceramics, if pressure is applied to the piezoelectric crystal piezoelectric transducer, this will directly generate a potential difference, otherwise, when a voltage is applied, mechanical stress will be generated (called the inverse piezoelectric effect). If the pres

The vibration of the object can generate fluctuations.The mechanical wave with a frequency between 16 Hz and 20 kHz can cause human hearing. The mechanical wave in this band is called sound wave. Ultrasonic frequencies below 20 kHz are called infrasound waves, and flat frequencies above 20 kHz are c

Ultrasound refers to mechanical waves with a frequency higher than 20 kHz. In order to use ultrasonic waves as a detecting means, it is necessary to generate ultrasonic waves and receiving ultrasonic waves. The device that performs this function is an ultrasonic sensor, which is customarily called a

The ultrasonic ranging system developed has a range of more than 32 meters, a beamwidth of less than 100, and a bandwidth of about 4 kHz (22-25. 5 kHz). If a combined ultrasonic transducer structure is used, the bandwidth can be extended to 8 kHz. A large-range ultrasonic ranging system composed of

In order to improve the anti-interference ability and measurement accuracy of the ultrasonic ranging system, an appropriately selected PN can be used.The code replaces the single pulse signal as the encoded information. The noise signal is uncorrelated with the encoded information can be filtered by

The ultrasonic receiver is composed of an ultrasonic transducer and a receiving circuit. In order to achieve a wide range of ultrasonic ranging, it is required not only that the ultrasonic receiving circuit can amplify the weak signal reflected from the distant target, but also that the strong signa

A multi-probe ultrasonic range finder for detecting traffic flow conditions, which not only provides information for traffic flow survey statistics and intersection traffic signal automatic control systems, but also applies to various automatic monitoring related to motor vehicle passing and arrival

The phase estimation method of time delay estimation is a practical method to improve the accuracy of ultrasonic delay estimation. Based on the fact that for a simple harmonic, the fourier transform (DFT) can be used to calculate its fourier coefficient corresponding to the resonant frequency, and t

As the medium for transmitting information, ultrasonic is more and more important in various fields such as flaw detection, ranging, and speed measurement due to its direct and reflective properties and its characteristics that are not easily affected by external factors such as light and electromag

Ultrasonic ranging transducer at low SNR and low sampling rates based on cross-correlation function. The specific method is as follows the ultrasonic signal sent by the transmitter is used as a reference signal, and the output of the receiver is immediately sampled at the end of each transmission of

The ultrasonic distance measuring transducer with double crystal oscillator is a bimorph ceramic that is bonded together and has opposite polarization directions.The working principle of the sheet is to apply an alternating electric field of opposite polarity to the upper and lower ceramic sheets in

A device for transmitting and receiving ultrasonic waves, which is called an ultrasonic transducer or ultrasonic probe; an ultrasonic transducer and transceiver circuit constitutes an ultrasonic sensor. In order to develop a large-range ultrasonic sensor, it is necessary to understand the physical p

At present, foreign big car companies have invested a lot of resources to develop advanced anti-collision and safety warning systems for advanced cars with GPS, but the excessive cost limits its application in ordinary cars. To this end, greatly reducing the cost of the car's active anti-collision a

The UAV ranging transducer system described in this paper applies to the principle of ultrasonic distance measurement, and uses the measurement ultrasonic wave to transmit pulses.The time difference between the wave and the received pulse wave has the relative position is calculated by the speed at