实时绘制光谱？ [英] Plot Spectrum in real time?

问题描述

我想在Qwt Oscillocope的例子中添加和绘制信号的频谱。我的想法是创建另一个seriesData类。
SerieData。我不知道是否会在SeriesData的样本和Signaldata的样本之间不会有冲突，或者我只需要修改signaldata？
任何帮助和建议将不胜感激。感谢

解决方案

输入信号通常采用循环缓冲的形式

<输出缓冲区可以是静态的

• 这也适用于时域图

这是我如何做的：

1. 为FFT执行一些缓冲区（数组）

   
   
   
   
   
   • static ...
   
   
   • 不会发生任何更改
   
   
   • 它的大小必须至少 slowest_timebase / fsampling samples
   
   
   • 如果您想要滚动/缩放/取消缩放，则您的FFT具有复杂的域输入，然后加倍大小
   
   

   • 
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     • 通过触发器
     
     
     • 或仅用于最后N个样本的启动器（但由于相位...会闪烁）
     
     
     • ，或者您以N-sampe块从开始到结束以与采样相同的速度预览所有样本
     
     
     • 类似于将数据发送到声卡播放声音
     
     
     过程数据
     
     
     
     
     
     • 将数据从起始点复制到FFT缓冲区
     
     
     • 如果需要，添加样本的虚部（Im = 0.0）
     
     
     • 处理FFT
     
     
     • 绘制实际输出的前半部分
     
     
     • max频率为fsampling / 2
     
     
     • 您也可以将对数轴添加到频率
     
     
     • 在这种情况下不要忘记更改绘图中的x值
     
     
     
     

     • 更新开始位置

       
       
       
       
       
       
       
       • 不要忘记触发器还会使用此时间作为起始点，然后才能找到真正的开始...
       
       
     
     




I would like to add and plot the spectrum of signal on Qwt Oscillocope's example. My Idea is to create another seriesData class. SerieData. I wonder if there will not conflict between sample of SeriesData and sample of Signaldata or I just need to modify the signaldata? Any help and Advice would be appreciated. Thanks

解决方案

input signal is usually in form of cyclic buffer

output buffer can be static one

• this applies also for time domain plot
• without actually see your structures is impossible to answer if you had to change them or not

Here is how I do this:

1. make some buffer (array) for FFT

   • can be static ...
   • no changes in it will happen
   • it size has to be at least slowest_timebase/fsampling samples
   • in case your FFT has complex domain input then double the size
   • if you want to scroll/zoom/unzoom then enlarge the size accordingly

2. find the start sample of the actual Oscilloscope view

   • via trigger
   • or for starters just last N-samples (but it will flicker because of phase ...)
   • or you preview all samples by N-sampe chunks from start to end with the same speed as sampling
   • similar like you would send data to soundcard to play sound
   • you just start after some time so you have enough sampled data already ...

3. process data

   • copy data from start point to FFT buffer
   • add imaginary part of samples if needed (Im=0.0)
   • process FFT
   • plot the first half of real output f it
   • max frequency is fsampling/2
   • you can also add logarithmic axises to frequency
   • in that case do not forget to change the x value in plot too

4. update start position

   • simply add to start position the size of used samples (N)
   • do not forget that trigger also use this time as start point before finding the real start...

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