超聲測距中的偽隨機碼渡越時間的捕獲

采用數字相關的方法確定超聲波測距中的渡越時間。借助于一個經過適當選擇的偽隨機序列信號作為超聲波的發射信號,可以通過數字相關方法求出發射序列和接收序列的相位差,即渡越時間。本文在計算自相關函數時放棄了快速傅立葉變換( FFT) 算法,省去了乘法運算,取而代之的是只用異或和加法的并行數字相關技術,它顯著地減少了數據處理時間和
FPGA 資源。系統以Altera 公司的quartus Ⅱ為開發平臺,經邏輯綜合、布局布線后,適配到FPGA 芯片中,給出了仿真結果。

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.