fft滤波器中dac输出的噪声

Question

我使用STM32F429 Discovery Board在Keil uvision中设计了一个fft滤波器（前向和反向FFT）。然而，在将DAC的输出带到示波器时，在两个连续的DAC输出之间会产生很多噪声。

编码或其他相关知识方面的任何帮助都会有很大的帮助。

显示DAC（黄色）和输入信号（粉红色）输出的示波器图片链接和FFT滤波器代码如下： Link1：https://drive.google.com/open?id=0B9NG28tRmEefVlBsTDNIZG1EUWM&authuser=0 Link2：https://drive.google.com/open?id=0B9NG28tRmEefZGlFdWc1N2Q5ZnM&authuser=0

Answer 1

Since you mentioned decreasing the number of samples in the FFT reduces the issue it sounds like a processing speed issue.

An FFT has an O(N log2(N)) so the increasing the number of samples greatly increases the amount of processing power required.

How are you coming up with the number of samples you need? What frequency resolution do you need for your application? If you intend for your sample rate to stay as it is now, then the only way to you to change the time and frequency resolution would be changing the number of samples.

I would recommend coming up with a minimum frequency resolution required. Round the number of samples to the closest power of 2 and test out the program with that criteria.