超声测距中的伪随机码渡越时间的捕获

超声测距中的伪随机码渡越时间的捕获

采用数字相关的方法确定超声波测距中的渡越时间。借助于一个经过适当选择的伪随机序列信号作为超声波的发射信号,可以通过数字相关方法求出发射序列和接收序列的相位差,即渡越时间。本文在计算自相关函数时放弃了快速傅立叶变换( FFT) 算法,省去了乘法运算,取而代之的是只用异或和加法的并行数字相关技术,它显著地减少了数据处理时间和
FPGA 资源。系统以Altera 公司的quartus Ⅱ为开发平台,经逻辑综合、布局布线后,适配到FPGA 芯片中,给出了仿真结果。

Digital correlation approach is used to find t he time of flight (tof) in ult rasonic distance measure2 ment . Wit h t he help of an adequately chosen Pseudo random Number ( PN) as t ransmit ting signal of t heult rasonic sensor , t he time of flight can be got by using digital correlation approach to fine t he p hase differ2 ence between t ransmit ting sequence and receiving sequence. The correlation f unction is comp uted by usingxor and add operation taking place of FF T algorit hm using multiplication. This met hod shortens t he pro2
cessing time and FPGA resource. The system design is based on Alet ra’s quart us Ⅱsof tware , and described by V HDL language and be fit ted to FPGA chip af ter logic synt hesizing and placement routing. The timing simulation result in placement and routing is also presented.