Signal processing

In communications and information processing, code is a system of rules to convert information—such as a letter, word, sound, image, or gesture—into another form, sometimes shortened or secret, for communication through a communication channel or storage in a storage medium. An early example is an invention of language, which enabled a person, through speech, to communicate what they thought, saw, heard, or felt to others. But speech limits the range of communication to the distance a voice can carry and limits the audience to those present when the speech is uttered. The invention of writing,

thumb|right|In The Signal by William Powell Frith, a woman sends a signal by waving a white handkerchief.

function that repeats its values in regular intervals or periods

models and analyzes data representations of physical events

difference between the upper and lower frequencies passed by a filter, communication channel, or signal spectrum

measurement of a signal at discrete time intervals

stability mechanism which occurs when some function of the output of a system, process, mechanism is fed back in a manner that tends to reduce the fluctuations in the output, whether caused by changes in the input or by other disturbances

process of mapping a continuous set to a countable set

modulation technique

thumb|300px|right|Above: A plot of a series of 100 random numbers concealing a sine function. Below: Its [[correlogram plots the autocorrelation function (ACF) of the series on the y-axis for every lag on the x-axis. Peaks occur at lags where the series is highly correlated with itself. Peaks to the right of the initial peak at lag 0 indicate periodicity in the series and help estimate the concealed sine's period.]] thumb|400px|Visual comparison of convolution, cross-correlation, and autocorrelation. For the operations involving function , and assuming the height of is 1.0, the value of the re

filter that passes signals with a frequency lower than a certain cutoff frequency, and attenuates signals with higher frequencies

quantitative measure of the output spectrum of a system or device in response to a stimulus

thumb|upright=1.35|Spectrogram of the spoken words "nineteenth century". Frequencies are shown increasing up the vertical axis, and time on the horizontal axis. The legend to the right shows that the color intensity increases with the density. thumb|upright=1.35|A 3D spectrogram: The RF spectrum of a battery charger is shown over time

Instrument that measures the magnitude of an input signal versus frequency within the full frequency range of the instrument

graph of the frequency response of a linear system presented in logarithmic scale

spectrometer for visible light

In digital signal processing, aliasing is a phenomenon that a reconstructed signal from samples of the original signal contains low frequency components that are not present in the original one. This is caused when, in the original signal, there are components at frequency exceeding a certain frequency called Nyquist frequency, f_s / 2, where f_s is the sampling frequency (undersampling). This is because typical reconstruction methods use low frequency components while there are a number of frequency components, called aliases, which sampling result in the identical sample. It also often refer

special mathematical function defined as sin(x)/x

A wavelet is a wave-like oscillation with an amplitude that begins at zero, increases or decreases, and then returns to zero one or more times. Wavelets are termed a "brief oscillation". A taxonomy of wavelets has been established, based on the number and direction of its pulses. Wavelets are imbued with specific properties that make them useful for signal processing. thumb|Seismic wavelet

ratio between the largest and smallest values that a certain quantity can assume, often used in the context of signals

sum of methods of simultaneous or sequential time measurement and counting for measurable or quantifiable data and groups of contiguous data

thumb|400px|Visual comparison of convolution, cross-correlation and [[autocorrelation. For the operations involving function , and assuming the height of is 1.0, the value of the result at 5 different points is indicated by the shaded area below each point. Also, the vertical symmetry of is the reason f*g and f \star g are identical in this example.]]

electronic manipulation of audio signals

thumb|upright=1.5|Frequency mixer symbol used in schematic diagrams. Here, the input signal consists of signals at multiple frequencies, which are mixed to create the output signal that are signals at new frequencies.

Nyquist stability criterion in control systems

relative importance of certain frequencies in a composite signal

stochastic process whose unconditional joint probability distribution does not change when shifted in time

angle of complex number about real axis

mathematical model of system that produces an output signal from any input signal subject to the constraints of linearity and time-invariance

concept in signal processing

thumb|Spectrum of a baseband signal, energy E per unit frequency as a function of frequency f. The total energy is the area under the curve.

thumb|right|Before and after deconvolution of an image of the lunar crater Copernicus (lunar crater)|Copernicus using the Richardson-Lucy algorithm.

analyzed the detection of difficult to detect signals and provides a measure of the quality of the detection

representation of a type of random process

integral transform and linear operator that takes a function of a real variable and produces another function of a real variable with a 90 degree phase shift

discrete Fourier transform with short overlapping windows

branch of statistics to estimate models based on measured data

study of speech signals and the processing methods of these signals

sound with a sinusoidal waveform

type of signal processing

signal processing device or process that removes unwanted components or features from a signal, or enhances wanted ones, or both

thumb|upright=1.3|A linear chirp waveform; a sinusoidal wave that increases in frequency linearly over time

plot

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signal processing filter

mathematical technique used in data compression and analysis

Mathematic test in control system theory

process of reducing the sampling rate of a signal

periodic distribution ("function") of "point-mass" Dirac delta sampling

mathematical model

non-linear digital filtering technique to remove noise

In Fourier analysis, the cepstrum (; plural cepstra, adjective cepstral) is the result of computing the inverse Fourier transform (IFT) of the logarithm of the estimated signal spectrum. The method is a tool for investigating periodic structures in frequency spectra. The power cepstrum has applications in the analysis of human speech.

time behavior

signal boosting phenomenon using white noise

form of modulation used in analog to digital conversions

the process of boosting noise-prone parts of the signal before transmission (and reversing upon receival)

model of signal reconstruction in digital-to-analog (DAC) converters

a specialized flow graph, a directed graph in which nodes represent system variables, and branches (edges, arcs, or arrows) represent functional connections between pairs of nodes

spectral decomposition theorem of stationary processes' autocorrelations

signal processing technique