Title ANALOG AND DIGITALCOMMUNICATION.pdf ✅

Multidimensional signal: Signals can be functions of more than one variable, e.g., image signals (2D), Colour image (3D), etc. Classification of signals Broadly we classify signals as: 1. Continuous-time signal: A signal x(t), is said to be continuous-time signal if it is defined for all time t, where t is a real-valued variable denoting time. Ex: x(t) = e -3t u(t) Discrete-time signal: A signal x(n), is said to be discrete-time signal; if it is defined only at discrete instant of time, where n is an integer-valued variable denoting the discrete samples of time. We use square brackets [·] to denote a discrete-time signal. Ex: x[n] = e -3n u[n] 2. Even and odd signal: A continuous-time signal x(t) is even, if x(-t) = x(t) and it is odd if x(-t) = -x(t). A discrete-time signal x[n] is even if x[-n] = x[n] and is odd if x[-n] = -x[n]. Example 1: x(t) = t 2 - 40 is even. Example 2: x(t) = 0.1t 3 is odd. Example 3: x(t) = e 0.4t is neither even nor odd. (a) (b) (c) Figure: Illustrations of odd and even functions. (a) Even; (b) Odd; (c) Neither. 1 t  X[n] e -3 e -6 e -9 0 1 2 3