FIR Narrowband Filters

You can design narrowband FIR filters using the FIR Narrowband Coefficients VI, and then implement the filtering using the FIR Narrowband Filter VI. The design and implementation are separate operations because many narrowband filters require lengthy design times, while the actual filtering process is fast and efficient. Keep this in mind when creating your narrowband filtering diagrams.

The parameters required for narrowband filter specification are filter type, sampling rate, passband and stopband frequencies, passband ripple (linear scale), and stopband attenuation (decibels). For bandpass and bandstop filters, passband and stopband frequencies refer to bandwidths, and you must specify an additional center frequency parameter. You can also design wideband lowpass filters (cutoff frequency near Nyquist) and wideband highpass filters (cutoff frequency near zero) using the narrowband filter VIs.

The following illustration shows how to use the FIR Narrowband Coefficients VI and the FIR Narrowband Filter VI to estimate the response of a narrowband filter to an impulse.