Signals and systems 2ed oppenheim pdf


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Discretization means that the signal is divided into equal intervals of time, and each interval is represented by a single measurement of amplitude. Quantization means each amplitude measurement is approximated by a value from a finite set. Numerical methods require a quantized signal, such as those produced by an ADC. The processed result might be a frequency spectrum or a set of statistics. The most common processing approach in the time or space domain is enhancement of the input signal through a method called filtering. Linear filters satisfy the superposition condition, i.

A non-causal filter can usually be changed into a causal filter by adding a delay to it. A “stable” filter produces an output that converges to a constant value with time, or remains bounded within a finite interval. An “unstable” filter can produce an output that grows without bounds, with bounded or even zero input. FIR filters are always stable, while IIR filters may be unstable. The Fourier transform converts the signal information to a magnitude and phase component of each frequency. Often the Fourier transform is converted to the power spectrum, which is the magnitude of each frequency component squared.