超声波扩频测距及其信道自适应均衡技术

Adaptive Ultrasonic Distance Measurement Based on Spread Spectrum Technique

在扩频通讯系统框架中,建立一种新颖的多阵元超声波测距定位系统。从测距系统的仿真结果来看,采用二进制相移键控(BPSK)直序信号数字相关解调技术和基于最小均方算法的超声波接收信道自适应均衡器,不仅可以克服本地载波(相干解调)相位偏移所带来的不利影响,而且可以抑制多径信道噪声干扰和接收信道增益、相位随机漂移对测量精度的影响,从而提高了超声波测距系统的信噪比和分辨率。此外,采用伪随机码扩频解扩方法,容易实现码分多址(只要给安装在大范围测量区域中多个传感器分配相应的伪随机码,就可以方便地辨认出各个区域传感器发出的信号),扩大超声波测距系统的测量范围。

This paper presents a novel method for distance measurement by multi ultrasonic arrays within the Direct Sequence Spread Spectrum (DS-SS) framework of the communication system. In view of the results of ultrasonic distance measurement simulation, it can be seen that the system design considerations, which is ground on the demodulation of BPSK signals by digital correlation and the adaptive equalization of receiving channels by means of Least-Mean-Squares algorithm, lead to strong restraint of the effect of disturbance in many cases, such as the phase error of local carrier used for coherent demodulation, the jam of multipath channels, and the random drift of the gain and phase in receiving channels, hence improve greatly the signal-noise ratio and the resolving power in ultrasonic orientation system accordingly. Furthermore, since the principle of the ultrasonic measurement system adopted here is based on spread spectrum with pseudorandom sequence codes, it is easier to realize of the Code Division Multiple Access (CDMA) by allocating different codes at different testing areas, so as to distinguish different signals transmitted by different ultrasonic transmitters/receivers, which will extend the measuring scope of the system. Thus it can be said that the methods considered in this paper has expansive prospect in the measure and control field for practical purposes.