The FIRInterpolator
object upsamples an input
by the integer upsampling factor, L, followed by
an FIR antiimaging filter. The filter coefficients are scaled by
the interpolation factor. A polyphase interpolation structure implements
the filter. The resulting discretetime signal has a sampling rate L times
the original sampling rate.
To upsample an input:
Define and set up your FIR interpolator. See Construction.
Call step
to upsample the input according
to the properties of dsp.FIRInterpolator
. The behavior
of step
is specific to each object in the toolbox.
Note:
Starting in R2016b, instead of using the 
H= dsp.FIRInterpolator
returns
an FIR interpolator, H
, which upsamples an input
signal by a factor of 3 and applies an FIR filter to interpolate the
output.
H = dsp.FIRInterpolator('
returns an FIR interpolator, PropertyName
',PropertyValue
,
...)H
, with
each property set to the specified value.
H = dsp.FIRInterpolator(INTERP,
NUM,'
returns an FIR interpolation object, PropertyName
',PropertyValue
,
...)H
,
with the InterpolationFactor
property set to INTERP
,
the Numerator
property set to NUM
,
and other properties set to the specified values.

Interpolation factor Specify the integer factor, L, by which to increase the sampling rate of the input signal. The polyphase implementation uses L polyphase subfilters to compute convolutions at the lower sample rate. The FIR interpolator delays and interleaves these lowerrate convolutions to obtain the higherrate output. The property value defaults to 3. 

FIR filter coefficient source Specify the source of the numerator coefficients as one of 

FIR filter coefficients Specify the numerator coefficients of the FIR antiimaging filter as the coefficients of a polynomial in z^{–1}. Indexing from zero, the filter coefficients are: $$H(z)={\displaystyle \sum _{n=0}^{N1}b}(n){z}^{n}$$ To act as an effective
antiimaging filter, the coefficients must correspond to a lowpass
filter with a normalized cutoff frequency no greater than the reciprocal
of the 
clone  Create FIR interpolator object with same property values 
freqz  Frequency response 
fvtool  Open filter visualization tool 
getNumInputs  Number of expected inputs to step method 
getNumOutputs  Number of outputs of step method 
impz  Impulse response 
isLocked  Locked status for input attributes and nontunable properties 
phasez  Unwrapped phase response 
release  Allow property value and input characteristics changes 
reset  Reset FIR interpolator filter states 
step  Upsample and interpolate input 
This object implements the algorithm, inputs, and outputs described on the FIR Interpolation block reference page. The object properties correspond to the block parameters, except:
The FIRInterpolator
object does not
have a property that corresponds to the Input processing parameter
of the FIR Interpolation block.
The Rate options block parameter
is not supported by the FIRInterpolator
object.