Filter input signal in the frequency domain
DSP System Toolbox / Filtering / Filter Implementations
The FrequencyDomain FIR Filter block implements frequencydomain, fast
Fourier transform (FFT)based filtering to filter a streaming input signal. In the time
domain, the filtering operation involves a convolution between the input and the impulse
response of the finite impulse response (FIR) filter. In the frequency domain, the
filtering operation involves the multiplication of the Fourier transform of the input
and the Fourier transform of the impulse response. The frequencydomain filtering
becomes more efficient than timedomain filtering as the impulse response grows longer.
You can specify the filter coefficients directly in the frequency domain by setting
Numerator domain to
Frequency
.
This block uses the overlapsave and overlapadd methods to perform the frequencydomain filtering. For filters with a long impulse response length, the latency inherent to these two methods can be significant. To mitigate this latency, the FrequencyDomain FIR Filter block partitions the impulse response into shorter blocks and implements the overlapsave and overlapadd methods on these shorter blocks. To partition the impulse response, select the Partition numerator to reduce latency check box. For more details on these two methods and on reducing latency through impulse response partitioning, see Algorithms.
Data Types 

Direct Feedthrough 

Multidimensional Signals 

VariableSize Signals 

ZeroCrossing Detection 

[1] Stockham, T. G., Jr. "High Speed Convolution and Correlation." Proceedings of the 1966 Spring Joint Computer Conference, AFIPS, 28 (1966): 229–233.