The document provides an overview of digital filters, including their definitions, features, and types such as FIR (Finite Impulse Response) and IIR (Infinite Impulse Response) filters. It discusses the importance of filter specifications and how ideal filters cannot be realized due to practical limitations. Examples of filtering applications include noise suppression in audio signals and image processing enhancements.

1. BASICS OF DIGITAL
FILTERS
Ismile Hossain
1403EEE00052
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2. REFERENCE
Wikipedia
MikroElektronika
(learn.mikroe.com/ebooks/digitalfilterdesign/chapter/b
asic-concepts-of-digital-filtering/)
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3. CONTENT
 What is a Digital Filter?
 Desired Features
 Example of Filtering Operations
 Types of Digital Filters
 FIR Filters
 IIR Filters
 Filter Specification
 Ideal Filters – Magnitude Response
 Designing Ideal Filters is Impossible
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4. WHAT IS A DIGITAL FILTER?
Digital Filter: Numerical procedure of algorithm
that transform a given sequence of
numbers into a second sequence that
has some more desirable properties .
Digital Filter
input sequence output sequence
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Xn Yn

5. DESIRED FEATURES
Desired features depend on the application, for
example
Input Signal Output
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generated by sensing
device (microphone)
having less noise or
interferences
speech with reduced
redundancy for more
efficient transmission

6. EXAMPLES OF FILTERING OPERATIONS
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• received radio signals
• electrical signals measured from human
body (brain, heart, neurological signals)
Noise suppression

7. EXAMPLES OF FILTERING OPERATIONS
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• treble and bass control or graphic equalizers
increase sound level and high and low level frequencies
to compensate for the lower sensitivity of the ear at
those frequencies or for special sound effects
Enhancement of selected frequency ranges
• Enhancement of edges in images

8. TYPES OF DIGITAL FILTERS
Broadly speaking, Two types of digital filters exist.
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FIR Filters(Finite Impulse Response Filters)
IIR Filters(Infinite Impulse Response Filters)

9. FIR FILTERS
The digital filter whose impulse response is
of finite duration is known as FIR Filter &
the response of the FIR filter depends
only on the present and past input
samples.
These FIR filters are also called non recursive filters.
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10. IIR FILTERS
The digital filter whose impulse response is of
infinite duration is known as IIR filter & the
response of an IIR filter is a function of current
and past input signal samples and past output
signal samples.
It is also called recursive filter.
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11. FILTER SPECIFICATION
Before a filter is designed and implemented we need
to specify its performance requirements.
There are four basic filter types:
• Low-pass
• High-pass
• Band-pass
• Band-stop
Frequency band where signal is passed is passband
Frequency band where signal is removed is stopband 11

12. IDEAL FILTERS – MAGNITUDE RESPONSE
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Ideal Filters are usually such that they admit a gain of 1 in a
given passband (where signal is passed) and 0 in their
stopband (where signal is removed).

13. DESIGNING IDEAL FILTERS IS IMPOSSIBLE
If a filter {h(n)} is casual, i.e.
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The transition from passband to stopband cannot be infinitely sharp
So, the Ideal filters cannot be implemented. For that necessary
to perform some approximations.

14. Thank You
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