Documentation Center    • Trials   • Product Updates  FIR
Interpolation  This example shows how to increase the sampling
rate of a signal using FIR interpolators from the DSP System
Toolbox™.  Creating FIR Interpolators  The DSP System Toolbox
supports different structures to perform interpolation including
FIR-based structures and CICs. Given an interpolation factor L,
a common design of an FIR interpolation filter is a Nyquist
filter with a cutoff frequency of pi/L and a gain of L. This
type of filter leaves the original samples unchanged and
interpolates L-1 samples between the original samples. See the
FIRHALFBAND, FIRNYQUIST, FIREQINT and INTFILT functions as well
as FDESIGN.INTERPOLATOR and FDESIGN.NYQUIST for more on the
design of interpolation filters.  L  = 3; % Interpolation factor
Hf = fdesign.interpolator(L,'Nyquist',L); Hi =
design(Hf,'SystemObject',true); % Polyphase FIR Interpolator  To
interpolate by a fractional factor, you can use a Direct-Form
FIR Polyphase Sample-Rate Converter. This struc