In digital signal processing, a digital filter is a system that performs mathematical operations on a discrete-time signal to either reduce or enhance certain aspects of that specific signal. For example, a digital filter can be used to attenuate noise, DC bias etc. Furthermore, a digital filter can be used to extract the signal within a certain frequency range, which is one of the most important role frequency selective digital filters. There are three main categories of digital filters: the recursive filters otherwise known as infinite impulse response (IIR) filters, and the nonrecursive filter otherwise known as finite impulse response (FIR) filters.
The MatDeck software contains a variety of different functions for both IIR and FIR filter design and analysis. The overview of these functions is given in a sequel.
Digital filter design
IIR filters
Filter type | Lowpass/Highpass | Bandpass/Bandstop |
Butterworth | buttlohi() | buttband() |
Chebyshev type I | cheby1lohi() | cheby1band() |
Chebyshev type II | cheby2lohi() | cheby2band() |
Elliptic filter | elliplohi() | elipband() |
FIR filters
- windowing design: firbandpass(), firbandstop(), firhighpass(), firlowpass()
- frequency sampling: firfreqsampl()
- optimal design: firopt(), firoptord ()
Digital filter analysis and implementation
- IIR filters: iirfilter(), initiirfilter(), iirfreqresp(), iirgrpdelay(), iirphasedelay()
- FIR filters: firfilter(), initfirfilter(),firfreqresp()
MatDeck provides several toolkits which enable digital filter designing in a graphical environment, which is very convenient for many users. The list of digital filtering toolkits is given below.
- Filtering Toolkit – IIR Filtering Form
- Filtering Toolkit for FIR design by windowing and frequency sampling – FIR Filtering Form
- Filtering Toolkit for FIR optimal design – FIR Optimal Form
Examples
- FIR filter designing by frequency sampling
- Finite impulse response filters
- IIR filter implementation
- Butterworth filter
- Chebyshev filter type I
- Chebyshev filter type I – bandstop and bandpass case
- Inverse Chebyshev filter – bandpass and bandstop case
- Elliptic filter – lowpass and highpass case
- Elliptic filter – bandpass and bandstop case
- Inverse Chebyshev filter – lowpass and highpass case