BACKMAT

# BACKMAT - Glossary 631 Glossary 1/f noise A type of random...

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Glossary 631 Glossary 1/f noise: A type of random noise that increases in amplitude at lower frequencies. It is widely observable in physical systems, but not well understood. See white noise for comparison. -3dB cutoff frequency: The division between a filter's passband and transition band. Defined as the frequency where the frequency response is reduced to -3dB (0.707 in amplitude). "A" law: Companding standard used in Europe. Allows digital voice signals to be represented with only 8 bits instead of 12 bits by making the quantization levels unequal. See mu law for comparison. AC: Alternating Current. Electrical term for the portion of a signal that fluctuates around the average (DC) value. Accuracy: The error in a measurement (or a prediction) that is repeatable from trial to trial. Accuracy is limited by systematic (repeatable) errors. See precision for comparison. Additivity: A mathematical property that is necessary for linear systems. If input a produces output p , and if input b produces output q , then an input of a + b produces an output of p + q . Aliasing: The process where a sinusoid changes from one frequency to another as a result of sampling or other nonlinear action. Usually results in a loss of the signal's information. Amplitude modulation: Method used in radio communication for combining an information carrying signal (such as audio) with a carrier wave. Usually carried out by multiplying the two signals. Analysis: The forward Fourier transform; calculating the frequency domain from the time domain. See synthesis for comparison. Antialias filter: Low-pass analog filter placed before an analog-to-digital converter. Removes frequencies above one-half the sampling rate that would alias during conversion. ASCII: A method of representing letters and numbers in binary form. Each character is assigned a number between 0 and 127. Very widely used in computers and communication. Aspect ratio: The ratio of an image's width to its height. Standard television has an aspect ratio of 4:3, while motion pictures have an aspect ratio of 16:9. Assembly: Low-level programming language that directly manipulates the registers and internal hardware of a microprocessor. See high-level language for comparison. Associative property of convolution: Written as: . This is ( a [ n ] t b [ n ]) t c [ n ] a [ n ] t ( b [ n ] t c [ n ]) important in signal processing because it describes how cascaded stages behave. Autocorrelation: A signal correlated with itself. Useful because the Fourier transform of the autocorrelation is the power spectrum of the original signal. Backprojection: A technique used in computed tomography for reconstructing an image from its views. Results in poor image quality unless used with a more advanced method. BASIC:

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## This note was uploaded on 02/10/2012 for the course ECE 3551 taught by Professor Staff during the Spring '11 term at FIT.

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BACKMAT - Glossary 631 Glossary 1/f noise A type of random...

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