CIC插值的代码
R = 2;                       % Interpolation factor.
hm = mfilt.cicinterp(R);           % Use default NumberOfSections and
                             % DifferentialDelay property values.
fs = 22.05e3;               % Original sample frequency:22.05 kHz.
n = 0:5119;                 % 5120 samples, .232 second long signal.
x = sin(2*pi*1e3/fs*n);     % Original signal, sinusoid at 1 kHz.

y_fi = filter(hm,x); % 5120 samples, still 0.232 seconds.
  
% Scale the output to overlay stem plots correctly.
x = double(x);
y = double(y_fi);
y = y/max(abs(y));
stem(n(1:22)/fs,x(1:22),'filled'); % Plot original signal sampled
                           % at 22.05 kHz.
hold on;
stem(n(1:44)/(fs*R),y(4:47),'r');   % Plot interpolated signal
                                   % (44.1 kHz) in red.
xlabel('Time (sec)');ylabel('Signal Value');