Mainly introducing the connection mode of the ultrasonic transducer array (auxiliary receiver) output port. The next chapter studies the design problem of the receiving and transmitting circuit of the disc-type piezoelectric transducer (main transducer), The circuit-assisted receiver array consists of 16 transducers, each with two external wire is acting as signal and ground.The echo signals in the range act on the auxiliary receiver array, and the adder has a signal output. In order to increase the signal-to-noise ratio of the auxiliary receiver, a band-pass filter is having a center frequency of 27.5 kHz and a quality factor of 5khz may be connected to the output of the second-stage.Then, it is added to the output signal of the band pass filter in the main receiving circuit transducer. In this way, the combined ultrasonic depth sensor can receive an echo signal of 22-29. 5 kHz, which widens the bandwidth of the air-mediated ultrasonic transducer.
The speed range assumes that the target reflection surface is facing the ultrasonic depth sensor transducer, then the doppler frequency offset f respectively represent the frequency of the echo signal and the transmitted signal; v represents the relative speed between the ultrasonic probe; c represents the ultrasonic wave in the air speed of propagation in the medium. When the target is far away from the ultrasonic probe (the distance is increased), }d is a negative value; otherwise, the target is close to the probe (the distance is reduced) and fd is a positive value. When the target is close to the probe, the combined ultrasonic probe can measure the maximum speed of the moving target. It can be seen that the combined transducer can be used to measure the moving target speed range of 50 -156km/hr. Here, the lower operating frequency is set to 23. 5 kHz, which is beneficial to expand the range and speed range of the ultrasonic transducer, but has a slight influence on the impedance matching effect.
In order to develop ultrasonic transducers with large distance, good directivity and wide-band ultrasonic depth transducer, this paper studies the design and fabrication methods of piezoelectric disc transducers and combined transducers based on radial thickness coordination mode. The contents include aspects : 1 According to the operating frequency and directivity index of the transducer, a piezoelectric disc transducer is designed. 2 Applying acoustic impedance matching and electromechanical impedance matching technology is to increase the working distance of the ultrasonic transducer; by using the sound field Fresnel zone, the unique acoustic transducer is designed, which effectively improves the ultrasonic transducer. Resistance to multipath interference. They are electromechanical equivalent circuit, voltage model and frequency response characteristics of the radial/thickness coupling vibration mode of the piezoelectric vibrator are given, and some experimental phenomena of the piezoelectric disc transducer are qualitatively analyzed and explained. In order to solve the problem of high-speed moving target detection, a new combined piezoelectric transducer structure with a piezoelectric disc transducer as the main transducer and a underwater acoustic transducer array as the auxiliary receiver was proposed.
Operating frequency range of piezoelectric disc transducer is between 22kHz - 25. 5kHz. When the operating frequency is 24. 5 kHz, the net resonance impedance is about 47552; near this frequency, the beam width of the transducer is -3 dB about 10 or so. After the parallel impedance matching of the transducer, the impedance at the resonant frequency of 23. 5 kHz is about 26452. Under the excitation of the high voltage pulse signal, the ultrasonic transducer does not produce a reverberation phenomenon.Combined transducers not only have the performance characteristics of piezoelectric disc transducers, but also have higher sensitivity and a larger range of speed measurement.