Digital Filters Analog Filters

A digital filter is programmable (The transfer function can be changed by exchanging coefficients in the memory without affecting the circuitry).

An analog filter can only be changed by redesigning the filter circuit.

Easy to design, test, simulate and implement. Difficult to design, test, simulate and implement.

Extremely stable with respect both to time and temperature.

Less stable as the characteristics of analog filter circuits are subject to drift and are dependent on temperature.

Fast DSP processors can handle complex combinations of filters in parallel or cascade, making the hardware requirements relatively simple and compact.

hardware is complex and large in size

High accuracy and better performance (Sharp Cut-off in the transition band)

Less accuracy (component tolerances)

Linear Phase (FIR Filters) Non Linear Phase

Computation must be completed in sampling period-Limits real time operation

Analog Filters required at high frequencies and for anti aliasing filters

Requires high performance ADC, DAC & DSP No ADC, DAC & DSP required.

Adaptive Filtering possible (ability to adapt to changes in the characteristics of the signal).

Adaptive Filters difficult.

Low cost High cost

Digital filters are classified into one of two basic forms, according to how they respond to a unit impulse:• Finite Impulse Response (FIR) Filters• Infinite Impulse Response (IIR) Filters

Finite Impulse Response Filters:

• In signal processing, a FIR filter is a filter whose impulse response is offinite duration, because it settles to zero in finite time.

• FIR digital filters use only current and past input samples, and none ofthe filter's previous output samples, to obtain a current output samplevalue

• Transfer function of the filter is

• To give a Finite Impulse Response (FIR), a filters must be non recursivei.e. no feedback, N = 0

Finite Impulse Response Filters:

• Higher filter order than IIR filters• Corresponding higher delay than IIR filters

Infinite Impulse Response Filter:

• https://engineering.purdue.edu/ME579/SummaryDigFilt.pdf

• https://www.slideshare.net/binbinno/fir-filter-design-windowing-technique

• https://www.ee.iitb.ac.in/~esgroup/es_mtech02_sem/es02_sem_rep_arojit.pdf

• https://www.eecis.udel.edu/~barner/courses/eleg305/lecture_notes/L22.pdfhttps://www.slideshare.net/amrelsayedm/dsp2018foehu-lec-07-iir-filter-design