ABSTRACT
Signal filtering is one of the most important operations in many electrical engineering systems [1]. However, the most widely used application of filtering is found in communications engineering, with some typical examples given below:
Frequency selection process• : In the car radio, for example, a tunable bandpass filter enables us to select our favorite AM or FM radio channel. In a more recent application, a cell phone switches its carrier frequency rapidly when it moves around from cell to cell. Signal Demodulation• : In amplitude or frequency demodulation, low pass filters are used to filter out the low-frequency baseband signal from the high-frequency modulated signal. Removal of signals from noise• : Generic filters such as low pass, bandpass, and specific filters such as Wiener and Matched filters [1] are used to extract audio and video signals from noisy signals. An audio signal can be represented as a one-dimensional time-dependent function x(t), representing signal amplitude, in volts, whereas video signals are two-dimensional functions of space f(x,y), representing the image intensity. A more detailed discussion on two-dimensional video analysis and filtering will be provided in Chapter 6. Analysis of practical signals• : Biomedical signals such as the EKG (heart) and EEG (brain) [2] provide valuable information into the workings of specific areas in the human body. Filters are essential to remove noise, or “smoothen” the received biomedical signal, before the signal is analyzed using tools such as the Fast Fourier Transform (FFT).
