Discrete-time, overlap-add, FIR filter
Hd = dfilt.fftfir(b,len)
Hd = dfilt.fftfir(b)
Hd = dfilt.fftfir
This object uses the overlap-add method of block FIR filtering, which is very efficient for streaming data.
Hd = dfilt.fftfir(b,len)
returns
a discrete-time, FFT, FIR filter, Hd
, with numerator
coefficients, b
and block length, len
.
The block length is the number of input points to use for each overlap-add
computation.
Hd = dfilt.fftfir(b)
returns
a discrete-time, FFT, FIR filter, Hd
, with numerator
coefficients, b
and block length, len=
100.
Hd = dfilt.fftfir
returns
a default, discrete-time, FFT, FIR filter, Hd
,
with the numerator b=1
and block length, len=
100.
This filter passes the input through to the output unchanged.
Note
When you use a |
The fftfir
uses an overlap-add block processing
algorithm, which is represented as follows,
where len
is the block length and M
is
the length of the numerator-1, (length(b)-1
),
which is also the number of states. The output of each convolution
is a block that is longer than the input block by a tail of (length(b)-1
)
samples. These tails overlap the next block and are added to it.
The states reported by dfilt.fftfir
are the tails
of the final convolution.
Create an FFT FIR discrete-time filter with coefficients from a 30^{th} order lowpass equiripple design:
b = firpm(30,[0 .1 .2 .5]*2,[1 1 0 0]); Hd = dfilt.fftfir(b)
To view the frequency domain coefficients used in the filtering, use the following command.
freq_coeffs = fftcoeffs(Hd);
dfilt
| dfilt.dfasymfir
| dfilt.dffir
| dfilt.dffirt
| dfilt.dfsymfir