Linear filters Linear filters An active filter is a type of analog electronic filter, distinguished by the use of one or more active component i.e. one which provides some form of power amplification. Typically this will be a vacuum tube, transistor or operational amplifier. ...more on Wikipedia about "Active filter"
An analog sampled filter an electronic filter that is a hybrid between an analog and a digital filter. The input signal is analog, and usually stored in capacitors. The time domain is digital, however. Distinct analog samples are shifted through an array of holding capacitors as in a bucket brigade. Analog summers and amplifiers do the arithmetic in the signal domain, just as in an analog computer. ...more on Wikipedia about "Analog sampled filter"
An anti-aliasing filter is commonly used in conjuction with digital signal processing and is a filter to restrict the bandwidth to approximately satisfy the Shannon-Nyquist sampling theorem. ...more on Wikipedia about "Anti-aliasing filter"
Audio crossovers are a class of electronic filters designed specifically for use in audio applications, especially hi-fi. A commonly used dynamic loudspeaker driver is incapable of covering the entire audio spectrum all by itself. Thus, crossovers serve the purpose of splitting the audio signal into separate frequency bands which can be handled by individual loudspeaker drivers optimized for those bands. A combination of multiple drivers each catering to a different frequency band constitutes most hi-fi speaker systems. An audio crossover may also be constructed mechanically and is commonly found in full-range speakers. ...more on Wikipedia about "Audio crossover"
A band-pass filter is a device that passes frequencies within a certain range and rejects ( attenuates) frequencies outside that range. An example of an analogue electronic band-pass filter is an RLC circuit (a resistor- inductor- capacitor circuit). These filters can also be created by combining a low-pass filter and a high-pass filter. ...more on Wikipedia about "Band-pass filter"
In signal processing, a band-stop filter or band-rejection filter is a filter that passes most frequencies unaltered, but attenuates those in a range to very low levels. It is the opposite of a band-pass filter. A notch filter is a band-stop filter with a narrow stopband (high Q factor). ...more on Wikipedia about "Band-stop filter"
In electronics and signal processing, a Bessel filter is a variety of linear filter with a maximally flat group delay (linear phase response). Bessel fiters are often used in audio crossover systems. ...more on Wikipedia about "Bessel filter"
The Butterworth filter is one type of electronic filter designs. It is designed to have a frequency response which is as flat as mathematically possible in the passband. Another name for them is 'maximally flat magnitude' filters. ...more on Wikipedia about "Butterworth filter"
Chebyshev filters, are analog or digital filters having a steeper roll-off and more passband ripple than Butterworth filters. Chebyshev filters have the property that they minimise the error between the idealised filter characteristic and the actual over the range of the filter, but with ripples in the passband. ...more on Wikipedia about "Chebyshev filter"
A crystal filter is a special form of quartz crystal used in electronics systems, in particular communications devices. It provides a very precisely defined centre frequency and very steep bandpass characteristics, that is a very high Q factor - far higher than can be obtained with conventional lumped circuits. ...more on Wikipedia about "Crystal filter"
An elliptic filter (also known as a Cauer filter) is a filter with equiripple behavior in both the passband and the stopband. ...more on Wikipedia about "Elliptic filter"
In audio processing, equalization (EQ) is the process of modifying the frequency envelope of a sound. Etymologically, it means to correct, or make equal, the frequency response of another audio device. The term "equalizer" is sometimes applied to audio filters in general, though strictly speaking not all audio filters are equalizers. ...more on Wikipedia about "Equalization"
An equalization (EQ) filter is a filter, usually adjustable, chiefly meant to compensate for the unequal frequency response of some other signal processing circuit or system. ...more on Wikipedia about "Equalization filter"
A filter bank is an array of band-pass filters that separates the input signal into several components, each one carrying a single frequency subband of the original signal. It also is desirable to design the filter bank in such a way that subbands can be recombined to recover original signal. The first process is called analysis, while the second is called synthesis. The output of analysis is referred as subband signal with as many subbands as there are filters in filter bank. ...more on Wikipedia about "Filter bank"
A high-pass filter is a filter that passes high frequencies well, but attenuates (or reduces) frequencies lower than the cutoff frequency. The actual amount of attenuation for each frequency varies from filter to filter. It is sometimes called a low-cut filter; the terms bass-cut filter or rumble filter are also used in audio applications. A high-pass filter is the opposite of a low-pass filter. See also bandpass filter. ...more on Wikipedia about "High-pass filter"
The Kalman filter is an efficient recursive filter which estimates the state of a dynamic system from a series of incomplete and noisy measurements. An example of an application would be to provide accurate continuously-updated information about the position and velocity of an object given only a sequence of observations about its position, each of which includes some error. It is used in a wide range of engineering applications from radar to computer vision. Kalman filtering is an important topic in control theory and control systems engineering. ...more on Wikipedia about "Kalman filter"
A linear filter applies a linear operator to a time-varying input signal. Linear filters are very common in electronics and digital signal processing (see the article on electronic filters), but they can also be found in mechanical engineering and other technologies. ...more on Wikipedia about "Linear filter"
A low-pass filter is a filter that passes low frequencies well, but attenuates (or reduces) frequencies higher than the cutoff frequency. The actual amount of attenuation for each frequency varies from filter to filter. It is sometimes called a high-cut filter, or treble cut filter when used in audio applications. ...more on Wikipedia about "Low-pass filter"
The Optimum "L" filter (also known as a Legendre filter) was proposed by Athanasios Papoulis in 1958. It has the maximum roll off rate for a given filter order while maintaining a monotonic frequency response. It provides a compromise between the Butterworth filter which is monotonic but has a slower roll off and the Chebyshev filter which has a faster roll off but has ripple in either the pass band or stop band. The filter design is based on Legendre polynomials which is the reason for its alternate name and the "L" in Optimum "L". ...more on Wikipedia about "Optimum "L" filter"
A polyphase quadrature filter, or PQF is a filter bank, which splits an input signal into a given number N (mostly a power of 2) of equidistant sub-bands. These sub-bands are subsampled by a factor of N, so they are critically sampled. ...more on Wikipedia about "Polyphase quadrature filter"
In digital signal processing, a quadrature mirror filter is a filter bank which splits an input signal into two bands which are subsampled by a factor of 2. The upper band has inverted frequencies, i.e. low frequencies are encoded as high frequencies and vice versa. ...more on Wikipedia about "Quadrature mirror filter"
The raised-cosine filter is a particular electronic filter, frequently appearing in telecommunications systems due to its ability to minimise inter-symbol interference (ISI). It is so called due to the non-zero portion of the frequency spectrum of its simplest form () being a cosine function, 'raised' up to sit above the (horizontal) axis. ...more on Wikipedia about "Raised-cosine filter"
A Sallen and Key filter is a type of active filter, particularly valued for its simplicity. The circuit produces a 2-pole (12dB/octave) lowpass or highpass response using two resistors, two capacitors and a unity-gain buffer amplifier. Higher-order filters can be obtained by cascading two or more stages. ...more on Wikipedia about "Sallen Key filter"
A state variable filter is a type of active filter which can produce simultaneous lowpass, highpass and bandpass outputs from a single input. ...more on Wikipedia about "State variable filter"
The Wiener filter is a filter proposed by Norbert Wiener during the 1940s and published in 1949 . ...more on Wikipedia about "Wiener filter"
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