| Ultrasonic wave is the important carrier of the signal transmission, because it has strong directivity, the propagation distance in the medium and the slow energy consumpation in the process of transmission. At the same time, the ultrasonic ranging system is widely used in many fields such as military, industry and automobile manufacturing because of its high adaptability to bad weather such as sleety weather,haze weather and sand duststorm weather. At present, the domestic ultrasonic distance measuring system is still far away from the overseas system in the precision of ranging,so it is urgent to study the digital signal processing with high accuracy.In this thesis, the characteristics of ultrasonic wave are introduced firstly, and the anti-jamming performance of ultrasonic ranging system based on ultrasonic carrier is analyzed. The NUC472 is introduced as the core of the development of the hardware system of the distance measurement system, combined with the hardware architecture design of the programmable module of the drive function. The stepping amplification algorithm based on AGC controllable gain technique is analyzed and the feasibility of non - equal interval stepping scheme is analyzed. The algorithm of FFT matching is designed to avoid the jump of step series caused by false triggering of long range ranging noise.A technical scheme for digital signal path of ultrasonic echo is introduced, The idea of this scheme is to use the elliptic digital filter algorithm as the input and output.Combining with the programmed envelope detection and down sampling processing,the algorithm comes down to five-step algorithm. By using MATLAB software and MDK software, the design and simulation of each algorithm are compared and the rationality of algorithm development is verified. This paper also presents a square-law detection algorithm for processing the output of a five-step algorithm, which is used as an optional module to improve the dynamic range of small-signal.An ultrasonic echo matching algorithm based on the NUC472 master control system is designed to avoid the interference of external ultrasonic equipment and realize the intelligent identification of the signal of the specified transducer in the ranging system.The scheme of BCH coding and decoding algorithm is designed and simulated. The structure of the transmitter symbol sequence and the software modulation mode are constructed. Threshold setting method of the single threshold system is analyzed in detail, and the sequence regression by software threshold is designed. The feasibility of the matching algorithm is tested by a board-level experiment. |
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