The Importance of Filters and FIR Filters in Digital Signal Processing

June 18, 2019

Digital signal processing relies on many different components. One of these components are filters.

What’s the role of filters insignal processing?

A signal contains many different frequencies. Not all of these frequencies are of use to us. So, we need to get rid of the frequencies that we don’t need and keep the ones that are important for our application. For that, we need to condition the signal. Filters are the most common types of signal conditioners used in electronics today.

The ability of a filter to “filter” out certain frequencies can be explained in terms of its frequency response.

What is frequency response?

A filter has this unique property to respond differently to different frequencies that constitute a signal. This is referred to as the frequency response of the filter.

Filters mainly respond to frequencies in three ways. They either:

• Let them pass through;
• Completely stop them; or
• Partially attenuate them

When filters respond by letting the frequencies pass through, we describe the response as pass band. When filters respond by stopping the frequencies, we describe the response as stop band. And when filters respond by partially attenuating the frequencies, we describe the response as transition band.

A filter can be designed to have a specific pass band, stop band and transition band. This customization is achieved by selecting an appropriate filter length and coefficient. If the designed filter has a finite impulse response, we call it an FIR filter.

What is an FIR filter?

An FIR filter is a filter structure that can be used to implement any sort of frequency response within a system. The filter has a frequency response of finite duration, meaning that it settles to zero in finite time.

The advantages of using FIR filters in digital signal processing are as follows:

• They are easy to implement
• They enable stable system designs
• They effectively support multi rate applications
• They can be used to generate liner phase response

Besides FIR filters, there is another class of filters used in digital signal processing, though less commonly, called IIR filters. These filters have a feedback mechanism and are known for their higher efficiency.

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