画过高速PCB电路板的人，应该用过阻抗计算软件吧，这个就是一个很好的软件，希望对你们有所帮助。-painted high-speed PCB circuit boards, should impedance calculation software used it, This is a very good software, and I hope to help you.

DSP中全通滤波琦国旅语音，机器适合老师不值得作业，大家加油-All-pass filter in DSP Qi CITS voice, the machine is suitable teachers do not deserve the job, we refuel