使用动画包第 2 部分制作带有 FM 调制的动画余弦波形

Question

这个问题是基于给出的优雅解决方案而提出的这里。

我已经更新了方程式。对于调频 (FM) 信号，这些是方程式：

Carrier = cos(2*pi*fc*t)

Modulation = sin(2*pi*fm*t)

FM = cos(2*pi*fc*t+5*sin(2*pi*fm*t))

我正在尝试获取这个图的 FM：

相反，我得到的是：

您能帮助我获得正确的输出吗？谢谢！

这是我根据原始解决方案修改后的代码：

代码

\documentclass{standalone}

\usepackage{pgfplots}
\pgfplotsset{compat=newest}
\usepackage{animate}
\usepackage{xsavebox} % xlrbox
\usepackage{calc} % \widthof{...}, \real{...}

\usepackage{amsmath}

\begin{document}
%
%save two cycles in an xlrbox
\begin{xlrbox}{TwoCycles}
  \begin{tikzpicture}
    \begin{axis}[hide axis]
      \addplot[domain=-2*pi:2*pi,black,samples=501] {sin(x*2*180/pi)};
      \addplot[domain=-2*pi:2*pi,blue,samples=501] {cos(x*10*180/pi)-2.5};
      \addplot[domain=-2*pi:2*pi,red,samples=501] {cos(x*10*180/pi + 5*sin(x*2*180/pi))-5};
    \end{axis}
  \end{tikzpicture}
\end{xlrbox}%
%
\begin{animateinline}[controls,loop,width=12cm,height=6cm]{10}
  \multiframe{36}{i=0+1}{
    \makebox[\widthof{\theTwoCycles}][l]{% window
      \makebox[\widthof{\theTwoCycles}/\real{72}*\real{-\i}]{}% offset
      \theTwoCycles\theTwoCycles%
    }
  }
\end{animateinline}

\end{document} 

Answer 1

180/piPGF 的三角函数要求其参数以度为单位。因此，绘制第三条曲线时，必须将整个参数乘以。

[0:pi]此外，通过在 中仅保存一个周期的基信号，然后在四个周期宽度的窗口中移动五个周期，进一步优化了尺寸xlrbox。将线连接设置为，round以防止图中出现火花。

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% uncomment \def\export{} below to export animation
%% to multipage PDF a.pdf and run
%% 
%%  convert -density 300 -delay 4 -loop 0 -alpha remove a.pdf b.gif
%%
%% to get an animated GIF b.gif at 100/4 = 25 frames per s
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%\def\export{}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\ifdefined\export
  \documentclass[export]{standalone}
\else
  \documentclass{standalone}
\fi

\usepackage{pgfplots}
\pgfplotsset{compat=newest}
\usepackage{animate}
\usepackage{xsavebox} % xlrbox
\usepackage{calc} % \widthof{...}, \real{...}

\usepackage{amsmath}

\begin{document}
%
%save ONE cycle in an xlrbox
\begin{xlrbox}{OneCycle}
  \begin{tikzpicture}
    \begin{axis}[
      hide axis,
      x=1cm,y=1cm,
      /tikz/line cap=rect, /tikz/line join=round
    ]
      \addplot[domain=0:pi,black,samples=250] {cos(x*2*180/pi)};
      \addplot[domain=0:pi,blue,samples=500] {cos(x*20*180/pi)-2.5};
      \addplot[domain=0:pi,red,samples=500] {cos((x*20 + 6*sin(x*2*180/pi))*180/pi)-5};
    \end{axis}
  \end{tikzpicture}
\end{xlrbox}%
%
\begin{animateinline}[controls,loop]{10}
  \multiframe{18}{i=0+1}{
    \makebox[\widthof{\theOneCycle}*\real{4}][l]{% window = FOUR cycles
      \makebox[\widthof{\theOneCycle}/\real{18}*\real{-\i}]{}% offset
      \theOneCycle\theOneCycle\theOneCycle\theOneCycle\theOneCycle% moving FIVE cycles 
    }
  }
\end{animateinline}

\end{document}