基于FPGA的超声信号数字正交解调器

Digital quadrature demodulator for detecting ultrasonic signal based on FPGA

利用FPGA设计用于检测微弱超声信号的数字正交解调器。将经高速A/D采样的数字信号分为两路正交的基带信号,通过数字混频、低通滤波和数据抽取,最后从两路正交基带信号中提取出超声回波信号的幅度信息。本文对数字正交解调进行了理论分析,并分别利用FPGA中的内建RAM实现数控振荡器,内嵌乘法器实现数字混频,IP核实现低通滤波器,及宏模块实现数学运算。对玻璃杯的扫描成像实验结果,证明了设计的正确性。

A digital quadrature demodulator is designed to detect weak ultrasonic signal using FPGA. The digital ultrasonic signal is divided into two quadrature baseband signals which are processed by frequency mixer, LPF and data abstraction. Finally, the demodulator extracts the envelope of ultrasonic signal from the two baseband signals. First, we introduce the principle of digital quadrature demodulation. Secondly, we implement NCO using RAM in FPGA, frequency mixer using embodied multiplier, LPF using IP core, and mathematical manipulation using megafunctions. The performances have been validated by the experimental result gotten by scanning a glass.