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Unformatted text preview: 1 ENG17 FrequencyDomain Analysis Prof. Spencer AC Sources • AC voltages or currents are generated by: – microphones – musical instruments – sensors (e.g., pressure, temperature) – AC power generators – Many other sources • Most AC voltage and currents are not sinusoidal • But, virtually all practical periodic functions of time can be represented by summations of scaled and shifted sinusoids (using the Fourier series) – When the function is not periodic, we can still handle it, you’ll see how in upperdivision courses (you can use the Fourier or LaPlace transforms) 2 Time and Frequency Domains • We can represent a single sine wave in either the time domain , or the frequency domain • The frequency domain representation of a sine wave is a vertical line; it shows how the energy is distributed in frequency ( ) sin[2 (1 MHz) ] v t t π = frequency (cycles/sec = Hertz) Periodic NonSinusoidal Signals • More complex signals can be decomposed into a sum of scaled and shifted sine waves (only the amplitude is shown here  there is a phase plot in the frequency domain too) ( ) sin[2 (1 MHz) ] 0.3sin[2 (2 MHz) 0.3] 0.4sin[2 (3 MHz) 0.5] 0.2sin[2 (4 MHz) 0.1] v t t t t t π π π π = + − − + + − 3...
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 Fall '08
 Lagerstrom
 Digital Signal Processing, Fourier Series, Frequency, Volt, LTI system theory

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