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Signal Processing Topics - ACK
- In telecommunications, this is the acknowledge character in many data codes; used most commonly for an affirmative response of correct receipt.
- Angular Rate Sensor
- A sensor that measures rotational velocity around its sensitive axis.
- Anti-Aliasing Filter
- A device that attenuates signal content outside the desired bandwidth.
- Asymmetric Waveform
- A waveform that has unequal excursions above and below the horizontal axis.
- Autocorrelation
- The autocorrelation function gives a measure of the extent to which a signal correlates with a displaced version of itself, as a function of the displacement.
- Autocovariance
- This is the degree to which a function is correlated with itself as a function of time.
- Autospectrum
- A spectrum with the coefficients of the components expressed as the square of the magnitudes
- Band Stop Filter
- An electronic network which passes signals having frequencies above and below the band-elimination frequency span.
- Bandpass Filter
- An electronic network which transfers through it a specific band of signal frequencies.
- Bandwidth
- The bandwidth of a filter is the separation between the lower and upper frequencies at which the amplitude of a sinusoidal signal is attenuated by a factor of 2.
- Bandwidth Time Product
- Used in calculating the confidence limit of a measurement.
- Blackman Window
- A weighting that is applied in the time domain to reduce leakage within a Fourier Transform analysis.
- Blackman-Harris Window
- A weighting that is applied in the time domain to reduce leakage within a Fourier Transform analysis. The Blackman-Harris window has much the same performance as the Kaiser-Bessel window, except that it suppreses the sidelobes more than 92dB at a cost of an 11% wider noise bandwidth.
- Bohman Window
- A weighting that is applied in the time domain to reduce leakage within a Fourier Transform analysis.
- Campbell Diagram
- A mathematically constructed diagram used to check for coincidence of vibration sources with natural resonances.
- Cauchy Window
- A weighting that is applied in the time domain to reduce leakage within a Fourier Transform analysis.
- Cepstrum
- A cepstrum is a time history defined as the power spectrum of the logarithm of the Power spectrum.
- Chirp
- A chirp is a sound that has a rapid increase in frequency.
- Circular Frequency
- The frequency of a steady recurring phenomenum in radians per second.
- Clipper Circuit
- A circuit that blocks or removes the portion of a voltage waveform above some threshold voltage.
- Coherence
- This gives a measure of the linear dependence between signal A and B.
- Colourmap
- This is a method of plotting noise or vibration versus engine speed and frequency simultaneously.
- Constant Percentage Bandwidth Filter
- A band-pass filter whose bandwidth is a constant percentage of centre frequency. 1/3 octave filters are constant percentage bandwidth.
- Control System
- A group of components systematically organized to perform a specific control purpose.
- Convolution
- Convolution meaning ..intertwined, coiled…
- Correlation
- Generally speaking, a similarity between data; the extent to which data are related.
- Covariance
- A measure of the joint variability of a pair of numeric variables.
- Crest Factor
- Peak value divided by the R.M.S. value, used as a measure of the severity of a segment of data.
- Cross Correlation
- The cross-correlation function gives a measure of the extent to which two signals correlate with each other as a function of the time displacement between them.
- Cross Spectrum
- The cross spectrum Fxy(f) of fx(t) and fy(t) is the forward Fourier Transform of the cross correlation function Rxy(T). The cross spectrum is in general complex.
- DAC
- Abbreviation of Digital-to-Analogue Converter.
- DAQ
- Abbreviation of Data Acquisition.
- Data Acquisition
- Collecting and measuring electrical signals from sensors, transducers, and test probes or fixtures and inputting them to a computer for processing.
- Data Processing
- The execution of a systematic sequence of operations performed upon data. Synonymous with information processing.
- Date Stamp
- Information added to data to indicate the date at which it was collected.
- DC Component
- The dc value of an waveform that has a value other than zero.
- Degenerative Feedback
- Feedback in which the feedback signal is out of phase with the input signal.
- Delta-Sigma Modulating ADC
- A high-accuracy circuit that samples at a higher rate and lower resolution than is needed and pushes the quantization noise above the frequency range of interest.
- Digital Signal Processing
- The term used for calculations performed on digital signals.
- Digital-to-Analogue Converter
- Converts a digital number into a corresponding analogue voltage or current.
- Discrete Fourier Transform
- The digital version of the fourier transform.
- Dropout
- Any discrete variation in signal level during the reproduction of recorded data which results in a data-reduction error.
- Fast Fourier Transform
- An algorithm, or digital calculation routine, that efficiently calculates the discrete Fourier transform from the sampled time waveform.
- Filter
- Any of various electric, electronic, acoustic, or optical devices used to reject signals, vibrations, or radiation of certain frequencies while passing others.
- Finite Impulse Response Filter
- A commonly used type of digital filter. Digitized samples of the audio signal serve as inputs, and each filtered output is computed from a weighted sum of a finite number of previous inputs.
- FIR Filter
- A commonly used type of digital filter. Digitized samples of the audio signal serve as inputs, and each filtered output is computed from a weighted sum of a finite number of previous inputs.
- Flattop Window
- An amplitude weighting of the time signal used with gated continuous signals to give them a slow onset and cut-off in order to reduce the generation of side lobes in their frequency spectrum.
- Fourier Analysis
- A mathematical analysis of waves, discovered by the French mathematician Fourier (1768-1830).
- Fourier Transform
- The mathematically rigorous operation which transforms from the time domain to the frequency domain and vice versa.
- Gaussian Noise
- Another name for Random Noise.
- G Weighted Overall Level
- This purportedly reflects human response to infrasound.
- Hamming Window
- An amplitude weighting of the time signal used with gated continuous signals to give them a slow onset and cut-off in order to reduce the generation of side lobes in their frequency spectrum.
- Hanning Window
- An amplitude weighting of the time signal used with gated continuous signals to give them a slow onset and cut-off in order to reduce the generation of side lobes in their frequency spectrum.
- Hanning-Poisson Window
- A weighting that is applied in the time domain to reduce leakage within a Fourier Transform analysis.
- Harmonic Analysis
- Statistical method for determining the amplitude and period of certain harmonic or wave components in a set of data with the aid of Fourier series.
- Image Frequency
- An undesired frequency capable of producing the desired frequency through heterodyning.
- Infinite Impulse Response Filter
- A commonly used type of digital filter. This recursive structure accepts as inputs digitized samples of the audio signal, and then each output point is computed on the basis of a weighted sum of past output (feedback) terms, as well as past input values.
- Instantaneous Amplitude
- The amplitude at any given point along a wave at a specific instant in time.
- Instantaneous Value
- The magnitude at any particular instant when a value is continually varying with respect to time.
- Integrating ADC
- An ADC whose output code represents the average value of the input voltage over a given time interval.
- Interaural Cross-Correlation Coefficient
- The measure of the difference in the sounds arriving at the two ears of a listener.
- Kaiser Bessel Window
- A weighting that is applied in the time domain to reduce leakage within a Fourier Transform analysis.
- Kalman Filter
- A technique for estimating an unknown state of a linear dynamic system given observations of the system which have additive (Gaussian) noise.
- Linear Distortion
- Magnitude and phase distortion.
- Lower Frequency Cutoff
- The lowest frequency a circuit will pass.
- Lower Sideband
- All difference frequencies below that of the carrier.
- Mark
- An interval during which a signal is present.
- Minimum Discernible Signal
- The weakest input signal that produces a usable signal at the output of a receiver.
- Modulated Wave
- A complex wave consisting of a carrier and a modulating wave.
- Multiplexing
- A method for simultaneous transmission of two or more signals over a common carrier wave.
- Nonlinear Distortion
- New spectral components are produced.
- Notch Filter
- An electronic network which passes signals having frequencies above and below the band-elimination frequency span.
- Overdriven
- When the input signal amplitude is increased to the point that the transistor goes into saturation and cutoff.
- Overmodulation
- A condition that exists when the peaks of the modulating signal are limited.
- PAM
- Abbreviation of Pulse Amplitude Modulation
- PDM
- Abbreviation of Pulse Duration Modulation.
- Percent of Modulation
- The degree of modulation defined in terms of the maximum permissible amount of modulation.
- Periodic Wave
- A waveform that undergoes a pattern of changes, returns to its original pattern, and then repeats the same pattern of changes.
- PFM
- Abbreviation of Pulse Frequency Modulation.
- Phase Modulation
- Angle modulation in which the phase of the carrier is controlled by the modulating waveform.
- Positive Alternation
- The part of a sine wave that is above the reference line.
- Positive Feedback
- Feedback in which the feedback signal is in phase with the input signal.
- Power Standing Wave Ratio
- The ratio of the square of the maximum and minimum values of a wave.
- PPM
- Abbreviation of Pulse Position Modulation.
- PSWR
- Abbreviation of Power Standing Wave Ratio.
- PTM
- Abbreviation of Pulse Time Modulation.
- Pulse
- Signal characterized by a steep rise from and decay toward an initial level.
- Pulse Amplitude Modulation
- Pulse modulation in which the amplitude of the pulses is varied by the modulating signal.
- Pulse Duration
- The period of time during which a pulse is present.
- Pulse Duration Modulation
- Pulse modulation in which the time duration of the pulses is changed by the modulating signal.
- Pulse Frequency Modulation
- Pulse modulation in which the modulating voltage varies the repetition rate of a pulse train.
- Pulse Modulation
- A form of modulation in which one of the characteristics of a pulse train is varied.
- Pulse Oscillator
- A sine-wave oscillator that is turned on and off at specific times.
- Pulse Position Modulation
- Pulse modulation in which the position of the pulses is varied by the modulating voltage.
- Pulse Time Modulation
- Pulse modulation that varies one of the time characteristics of a pulse train.
- Pulse Width
- Duration of time between the leading and trailing edges of a pulse.
- Pulse Width Modulation
- Pulse modulation in which the duration of the pulses is varied by the modulating voltage.
- PWM
- Abbreviation of Pulse Width Modulation.
- Quantization Error
- When a continuous time signal is digitized, because there isn′t an infinite number of discrete digital levels, the difference between the actual analog value and the digital representation of that value is defined as the quantization error.
- Rectangular Window
- An amplitude weighting used to truncate continuous time signals to fit within the length of the DFT window.
- Recursive Filter
- A filter in which there is no need to store past measurements for the purpose of calculating current estimates.
- Rest Frequency
- The carrier frequency during the constant-amplitude portions of a phase modulation signal.
- Ringing Oscillator
- A sine-wave oscillator that is turned on and off at specific times.
- Ripple Frequency
- The frequency of the ripple current.
- Selectivity
- The ability of a receiver to select the desired signal and reject unwanted signals.
- Shaping Circuit
- A circuit that alters the shapes of input waveforms.
- Signal Ground
- The common return or reference point for analog signals.
- Spectrum
- A spectrum is a definition of the magnitude of the frequency components that constitute a quantity.
- Spectrum Analyser
- An instrument for measuring, and usually recording, the spectrum of a signal.
- Splatter
- Unwanted sideband frequencies that are generated from over modulation.
- Standing Wave Ratio
- The ratio of the maximum to the minimum points of a wave.
- Step by Step Counter
- A counter that provides an output for each cycle of the input in one-step increments.
- SWR
- Abbreviation of Standing Wave Ratio.
- Time History
- A continuous record of the variation of a physical quantity (e.g. displacement, acceleration, force, etc.) with time.
- Tracking Filter
- A low-pass or band-pass filter which automatically tracks the input signal.
- Trigger
- A short pulse, either positive or negative, that can be used to cause an electronic function to take place.
- Turnover Frequency
- Also known as Nyquist Frequency.
- Velocity Servosystem
- A servosystem which controls the speed of the load it is driving.
- Waterfall Plot
- A series of spectral maps taken at regular intervals of time or at regularly spaced shaft speeds, similar to the flow of a waterfall.
- Waveform Analysis
- Observation displays of voltage and current variations with respect to time or by harmonic analysis of complex signals.
- Wavelet
- The wavelet allows a rapidly changing time history (e.g. door slam noise) to be investigated in the frequency domain.
- Windowing
- An amplitude weighting of the time signal used with gated continuous signals to give them a slow onset and cut-off in order to reduce the generation of side lobes in their frequency spectrum.
 
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