Research On A Ultrasonic Spread Spectrum Ranging System With Pseudo-random Code

Ultrasonic ranging technology is widely used in many fields, for example, level measurement, self-guided autonomous vehicles, fieldwork robots location, air and underwater target detection, identification and so on. In recent years,it has been put forward more and more higher requirement to the accuracy, range, extent and anti-interference of the rang-find system. Therefore this article uses spread spectrum technology in the ultrasonic ranging system to solve the problems of low accuracy and short measuring distance which the traditional ultrasonic ranging has.This is to promote the development of ultrasonic distance measuring technology of great significance。The paper, based on pulse compression techniques commonly used in radar, uses the high-frequency carrier signal modulated by low-frequency PN codes to stimulate ultrasonic transducer and spread spectrum chip Z87200 to determine the time difference between emitting and receiving waves.Also, the paper designs a hardware platform and software modules,through the LCD module display measuring distance and the experimental show the feasibility of this design. This method improves the effective distance and measurement precision, and can be upgraded to a space positioning system, allows multiple transmitters transmit signals at the same time to identify the signal and avoid signals collision.This has broad application prospect.The main works completed by the author of the paper include:1.By the investigation of the present level and progress of the ultrasonic ranging technology and spread spectrum communication technology. Give a detailed analysis of system errors and various factors that interfere with the measurement accuracy in ultrasonic ranging system.So this paper provides a solution is designed with pseudo random spectrum of ultrasonic ranging system solutions,to solve the contradiction between measuring accuracy and measuring distance in ultrasonic ranging system.2.Whether the rational design of transmitter circuit directly influence transmitter wave power and the repeatability of the waveform.The transmitter system compare three plans to select MAX232 chip as the main transmitter chip stimulate ultrasonic transducer.3.The design uses a digital spread spectrum processor Z87200 by the United States Stanford Telecom companies jointly developed with Zilog Inc.,achieving the waveform signal whitening, spread spectrum, modulation and despreading, demodulation, tracking, and de-whitening and other functions.4.Echo receiving circuit design using a TL852 sonar special receiver chip, which integrates a variable gain, frequency selective amplifier for the echo signal amplification and filtering, to improve signal quality.5.This paper completed a hardware part of the design,designed the software flow chart and finished the program code,maked the hardware circuit. At last papers on the work done and the problems encountered in the process were summarized and the research, analyzes the error causes and puts forward the corresponding improvement scheme.