Digital filters are used for two general purposes: (1) separation of signals that have been combined, and (2) restoration of signals that have been distorted in some way. Frequency Filters - high and low pass image filters… 8.2 c J.Fessler,May27,2004,13:18(studentversion) So far our treatment of DSP has focused primarily on the analysis of discrete-time systems. Analog filters are used in audio systems by engineers to send various frequencies to various speakers. Gaussian Smoothing - NR using convolution with a Gaussian smoothing kernel . Contents. Digital Filter Types in Delta-Sigma ADCs 2 Digital Filters in Delta-Sigma ADCs To understand why the digital filter is an important aspect in delta-sigma analog-to-digital conversion, it is critical to have a basic understanding of a delta-sigma modulator. These filters can be used to limit the analog signal’s bandwidth before altering them to digital signals. By varying the weight of the coefficients and the number of filter taps, virtually any frequency response characteristic can be realized with an FIR filter. Digital filters are discrete-time systems. 6.1 Classification of digital filters. Analog-to-digital conversion: Filters are placed in front of an ADC input to minimize aliasing. Conservative Smoothing - NR using maximum and minimum of neighborhood . Digital filters are often embedded in a chip that operates on digital signals, such as an MCU, SoC, processor, or DSP. Therefore, they possess all the properties of linear discrete-time systems discussed in Chapter 3. Chapter 14: Introduction to Digital Filters. All LTI systems can be thought of as lters, so, at least for LTI systems, to ﬁdesignﬂ Analog (electronic) filters can be used for these same tasks; however, digital filters can achieve far superior results. The type of digital filters that we shall design in this course is linear. Four Major Types of Filters. All linear discrete-time operations on an input sequence can be viewed as a filtering of the sequence to produce an output sequence. Crimmins Speckle Removal - more complex NR operator . Median Filter - NR using median of neighborhood . Now we nally have the analytical tools to begin to design discrete-time systems. Digital Filters. (From Rabiner et al, “Terminology in Digital Signal Processing.” Commonly, we limit the term filter to devices (hardware or software) that were designed specifically to boost or attenuate regions of a signal spectrum. There are two fundamental types of digital filters: finite impulse response (FIR) and infinite impulse response (IIR). The four primary types of filters include the low-pass filter, the high-pass filter, the band-pass filter, and the notch filter (or the band-reject or band-stop filter). Mean Filter - noise reduction NR using mean of neighborhood . For example, in the music industry, record & playback applications are needed to control the frequency components. 6 Linear Time-Invariant Filters 95% of what we need will be: Linear Homogeneity: Input and output scales at the same rate. Analog filters are fairly simple but increase in complexity if you desire a more precise roll-off; that is, making the filtered result more precisely “step-like” at roll-off requires successively more components. As the terminology suggests, these classifications refer to the filter’s impulse response.