Extract a frequency subband using a onesided (complex) bandpass decimator
DSP System Toolbox / Filtering / Multirate Filters
The Complex Bandpass Decimator block extracts a specific subband of frequencies using a onesided, multistage, complex bandpass decimator. The block determines the bandwidth of interest using the specified center frequency, decimator factor, and bandwidth values.
Data Types 

Multidimensional Signals 

VariableSize Signals 

The complex bandpass decimator is designed by applying a complex frequency shift transformation on a lowpass prototype filter. The lowpass prototype in this case is a multirate, multistage finite impulse response (FIR) filter. The desired frequency shift applies only to the first stage. Subsequent stages scale the desired frequency shift by their respective cumulative decimation factors. For details, see Complex Bandpass Filter Design and Zoom FFT.