Many fundamental physical phenomena, such as heat, air pressure, temperature, electrical voltage or current and electromagnetic field, change in time. They are generally known as waveforms or signals which are described by mathematical functions of time. Most of these signals can be described as a series that is a linear combination of orthogonal basis functions φk (n) (k =⋯,-2,-1,0,1,2,⋯), where the basis functions are in a discrete format. If these basis functions are in a complete orthogonal set, these signals can be accurately defined. For example, a signal x(n), where n is the data index in the time domain, can be expressed as
KeywordsDiscrete Fourier Transform Fast Algorithm Digital Signal Processing Wigner Distribution Orthogonal Basis Function
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