User`s guide

Overlap-Save FFT Filter
5-334
5Overlap-Save FFT Filter
Purpose Implement the overlap-save method of frequency-domain filtering.
Library Filtering / Filter Designs
Description The Overlap-Save FFT Filter block uses an FFT to implement the overlap-save
method, a technique that combines successive frequency-domain filtered
sections of an input sequence.
Valid inputs to this block are 1-D vectors, sample-based vectors, frame-based
vectors, and frame-based full matrices. All outputs are unbuffered into
sample-based row vectors. The length of the output vector is equal to the
number of channels in the input vector. An M-by-1 sample-based input has M
channels, so it would result in a length-M sample-based output vector. An
M-by-1 frame-based input has only one channel, so would result in a 1-by-1
(scalar) output.
The block’s data output rate is M times faster than its data input rate, where
M is the input frame-size. Thus, the block’s data input and output rates are the
same when the inputs are 1-D vectors, sample-based vectors, or frame-based
row vectors. For frame-based column and frame-based full-matrix inputs, the
block’s data output rate is M times greater than the block’s data input rate.
1-D vectors are treated as length-N sample-based vectors, and result in
sample-based length-N row vectors.
Overlapping sections of input
u are circularly convolved with the FIR filter
coefficients
The numerator coefficients for H(z) are specified as a vector by the
FIR
coefficients
parameter. The coefficient vector, b = [b(1) b(2) ... b(n+1)],
can be generated by one of the filter design functions in the Signal Processing
Toolbox, such as
fir1. All filter states are internally initialized to zero.
If either the filter coefficients or the inputs to the block are complex, the
Output parameter should be set to Complex. Otherwise, the default Output
setting,
Real, instructs the block to take only the real part of the solution.
Hz() Bz() b
1
b
2
z
1–
… b
n 1+
z
n–
+++==