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# Topic: Linear filter

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 Electronic filter - Wikipedia, the free encyclopedia The oldest forms of electronic filters are passive analog linear filters, constructed using only resistors and capacitors or resistors and inductors. A filter in which the signal passes through an inductor, or in which a capacitor provides a path to earth, therefore presents less attenuation to low-frequency signals than high-frequency signals and is a low-pass filter. Active filters are implemented using a combination of passive and active (amplifying) components. en.wikipedia.org /wiki/Electronic_filter   (1052 words)

 Voltage-controlled filter - Wikipedia, the free encyclopedia A voltage-controlled filter (VCF) is an electronic filter whose operating characteristics can be controlled by means of a control voltage applied to one or more inputs. A VCF allows its cutoff frequency and Q factor to be continuously varied; it usually gives a lowpass response, but may also be switchable to allow highpass, bandpass or even notch responses. A VCF is an example of an active non-linear filter: however, if its control voltage is kept constant, it will behave as a linear filter. en.wikipedia.org /wiki/Voltage-controlled_filter   (282 words)

 [No title]   (Site not responding. Last check: 2007-10-14) The output of the sampler 58 is passed, via a low-pass filter 60 and an A/D converter 62, to a Y memory 64. Turning now to the position of the linear equalizer 28 along the path, it can be seen that because the output of the Nyquist filter 42 is 32 bit in a complex format, which is then converted to a 16 bit real format, the linear equalizer must have sufficient capacity to handle such a signal. A linear equalizer (112) of a system (110) operates upon the signal to pre-distort the signal in a manner that compensated for subsequent linear distortion. www.wipo.int /cgi-pct/guest/getbykey5?KEY=00/79746.001228&ELEMENT_SET=DECL   (3556 words)

 [No title]   (Site not responding. Last check: 2007-10-14) The Dolby filter, which varies the amplitude of the output signal as a function of the level and frequency of the input, is an example of a nonlinear filter system. To improve the performance of the filter (43) for the first filtering problem, H (jw) is designed to be a fifth order low-pass type 1 Chebyshev filter with cut off frequency 0.5 rad/sec and 0.5 dB of ripple in the pass-band to ensure a satisfactory frequency response over the pass band. When using linear structures for the attenuation of signal energy in a physical system, the attenuated energy is usually absorbed by devices such as dampers in mechanical systems and resistors in electronic circuits and transformed to other energy forms such as thermal energy. www.wipo.int /cgi-pct/guest/getbykey5?KEY=99/45644.990910&ELEMENT_SET=DECL   (5580 words)

 Linear Time-Invariant Filters   (Site not responding. Last check: 2007-10-14) filter as linear or nonlinear, and time-invariant or time-varying. Time-varying filters, on the other hand, can generate audible sideband images of the frequencies present in the input signal (when they vary at audio rates). linearity and time-invariance will be formally introduced, together with some elementary mathematical aspects of signals. ccrma.stanford.edu /~jos/filters/Linearity_Time_Invariance.html   (239 words)

 Finite Impulse Response FAQ: Properties "Linear Phase" refers to the condition where the phase response of the filter is a linear (straight-line) function of frequency (excluding phase wraps at +/- 180 degrees). Minimum-phase filters (which might better be called "minimum delay" filters) have less delay than linear-phase filters with the same amplitude response, at the cost of a non-linear phase characteristic, a.k.a. Similarly, for interpolating filters (in which zeroes are inserted between the input samples to raise the sampling rate) you don't actually have to multiply the inserted zeroes with their corresponding FIR coefficients and sum the result; you just omit the multiplication-additions that are associated with the zeroes (because they don't change the result anyway.) www.dspguru.com /info/faqs/fir/props.htm   (1054 words)

 Nonlinear Signal Processing   (Site not responding. Last check: 2007-10-14) For example, it is well known that linear filters can remove additive high frequency noise as long as the signal and the noise do not overlap in the frequency domain. It is well known that the median filter is optimal among the set of all stack filters for minimizing the output variance when the input distribution is symmetric and no constraints are imposed. A filter is robust if outliers, or more generally, deviations from the statistical assumptions for which the filter is optimal in one way or another, do not greatly affect the performance of the filter. www2.mdanderson.org /app/ilya/NONLINEAR.htm   (1875 words)

 Polarizer It's a very visual filter with which to work: As you rotate it in its mount, the effects are immediately noticeable. A polarizing filter can deepen the color and contrast in a sky (the most intense effects are always 90° from the sun or light source), eliminate glare from wet or reflective surfaces and cut through atmospheric haze to increase clarity and contrast in a scene. The linear element polarizes the light, and the wave retardant de-polarizes it, and then the beam-splitting meter polarizes the light again for proper exposure. www.geocities.com /cokinfiltersystem/polarizer.htm   (1134 words)

 Spatial Filters - Mean Filter   (Site not responding. Last check: 2007-10-14) Mean filtering is usually thought of as a convolution filter. Mean filtering is most commonly used as a simple method for reducing noise in an image. In general the mean filter acts as a lowpass frequency filter and, therefore, reduces the spatial intensity derivatives present in the image. www.cee.hw.ac.uk /hipr/html/mean.html   (878 words)

 Linear Filter Functions This is a linear filtering function which is based on a kernel with gaussian weights. This function is typical of using filters with nonnegative impulse responses to smooth noisy data. All linear filter methods can be realized with this function and an appropriate kernel. mbi.dkfz-heidelberg.de /helios/doc/manuals/ip/bips/ch4_Filter.html   (564 words)

 Frequently asked questions about polarizers and UV filters The idea is to use a linear polarizer up front to get rid of some linearly polarized light you don't want (glare off shiny surfaces, for example, will have a large linearly polarized component), and then it "stirs up" the result so you don't have linearly polarized light bouncing around in the camera. Both of the filters filter out the UV light that can cause a blueish haze on your pictures, since normal film is not only sensitive to visible light, but also to UV. Because the UV is filtered out, you may notice the sky in your pictures is not as deep blue as it used to be. www.mat.uc.pt /~rps/photos/filters_uv_pol   (3421 words)

 Introduction to frequency response of linear filters. This is the origin of the z-plane term used in filter theory: it is the two-dimensional domain of a four-dimensinoal plot. The averaging filter is a special case of the one-zero linear filter. Another filter which would be interesting to examine in terms of transfer functions is are the feedback filters where the output of the filter is recycled in the filter. peabody.sapp.org /class/350.868/lab/frequencyresponse   (3292 words)

 [No title]   (Site not responding. Last check: 2007-10-14) Linear prediction and autoregressive % modeling are two different problems that can yield the same numerical % results. In both cases, the ultimate goal is to determine the parameters % of a linear filter. It is well-known that % the power spectral density of the output of this filter, when the filter % is excited with white gaussian noise is given by the magnitude-squared of % its frequency response multiplied by the variance of the white-noise % input. www.clemson.edu /cle4_share/CWE/COES0915_CLUG/REFERENCE/matlabr14/toolbox/signal/sigdemos/lpc-ardemo.m   (915 words)

 ICMC'96: Experiments with Non-Linear Filters Although the filter exhibits useful behaviour without it, we have found that the most striking effects are dependent on its inclusion, despite the concomitant need for a DC removal filter on the output. However, unlike the response of a linear comb filter, in which the peaks are regular in spacing, width and amplitude, this filter exhibits marked irregularities in all those aspects. Alternatively, the formula can be regarded as a non-linear comb filter with (typically) a low pass or low-frequency band-pass linear filter on the output, serving primarily to remove those extreme high-frequency components which will inevitably arise from the non-linear behaviour. www.bath.ac.uk /~masjpf/HK_poster.html   (1739 words)

 ESS 265: Chapter 9/Linear Prediction Filters and Neural Networks Linear prediction filters are used to describe the relation of one output, or system variable, to one or more inputs. For autoregressive filters, exponential decay occurs as a single spike at the first lag; oscillations appear as adjacent spikes of opposite sign in the first two lags. Coefficient versus lag for three moving average linear prediction filters: one in which the time series showed exponential decay; one in which the time series showed recurrence; and one in which the output was controlled by the derivative of the input. www-ssc.igpp.ucla.edu /personnel/russell/ESS265/Ch9/linear_predict   (5247 words)

 FDI Online Design Guide To convert a normalized amplitude response curve to a curve representing a filter whose corner frequency is not at one Hertz, multiplying any number on the frequency axis by the intended corner or ripple frequency scales the frequency axis. For active filters, the THD is usually specified in dBc (dB relative to the amplitude of the fundamental frequency component) and at a specific frequency and amplitude (ex. In applications where linear phase is critical and long phase delay cannot be tolerated, a linear active Bessel or a constant delay filter may be a better selection. www.freqdev.com /guide/fullguide.html   (8801 words)

 Summary of project   (Site not responding. Last check: 2007-10-14) Solving a system of linear equations still does not seem to be a difficult problem, but the challenge is that for an image of size M x M, we have a system of M In [2] a low complexity method of solving linear systems of equations with block Toeplitz matrices is proposed, in which, using the FFT and an appropriate permutation, the block circulant matrix is converted to a block diagonal matrix. linear equations is reduced to M independent systems of M linear equations, which is much easier to solve. www.owlnet.rice.edu /~elec532/PROJECTS00/commies/synth.html   (516 words)

 Introduction to filtering   (Site not responding. Last check: 2007-10-14) “Linear phase” means the phase varies linearly with the frequency, which means (see eqn above) that the delay is independent of frequency. Filters of a higher order are more complicated to implement, either electronically (for analog filters) or computationally (for digital filters), but they offer improved performance – up to a point. Above examples of types of filters are all “classical” filters that have been around a long time andwhcih were first developed in analog form. www.udel.edu /Biology/rosewc/biomed_sig_proc/notes/intro_to_filtering.html   (1067 words)

 Linear Kalman Filter Theory   (Site not responding. Last check: 2007-10-14) where z is the vector of measurements as a linear function of the states x, and v is a vector of random Gaussian measurement error. The Kalman Filter uses the assumptions that process and measurement may be inaccurate due to Gaussian distributions of noise to iteratively create a Least Squares Estimate of the true state from the states previously encountered. The filter tends to function better with a rising signal to noise ratio and is easily applied to a multitude of dynamic systems due to its flexibility and ease of implementation. www.andrew.cmu.edu /user/nsg/linear_theory.htm   (424 words)

 The Wiener filter The Wiener filter is the MSE-optimal stationary linear filter for images degraded by additive noise and blurring. Calculation of the Wiener filter requires the assumption that the signal and noise processes are second-order stationary (in the random process sense). This illustrates an important point about using MSE as a criteria for global filtering: regions are given priority for restoration according to how large they are, rather than their visual importance. osl.iu.edu /~tveldhui/papers/MAScThesis/node15.html   (452 words)

 Sharing Digital Photography Worldwide :: View topic - The Circular Polarizing Filter This filter is appears to be a single piece, and when screwed onto the lens, the top portion of the filter still turns to adjust the amount of effect. Light reflected from the clouds is not polarized, so it passes through the filter in much greater proportion than the sky light (though the filter does remove a lot of the light from a non-polarized source, much like a neutral-density filter), so the contrast is increased and the cloud structure stands out. Do make sure you are using the filters in circumstances where they have some polarized light to filter (like the display cabinet or at an angle to a window.) You should be able to rotate the filter until it blocks most of the glare that is being reflected from the glass. therealdotin.com /phpbb/viewtopic.php?t=2452   (2220 words)

 Glossary A filter which only passes light vibrating in a certain direction. Since the vibrational locus of the light allowed to pass through the filter is linear in nature, the filter is called a linear polarizing filter. Macro lenses are essential for shooting close-ups of flowers, insects and other small items at life-size magnification or larger. www.usa.canon.com /html/eflenses/lens101/glossary/index_l.html   (1055 words)

 Compensation algorithms Models the effect of linear filtering and additive noise as a shift of the means of the Gaussians in the Gaussian mixture distribution For each test utterance, obtain ML estimate of h, the log spectrum of the impulse response of the linear filter, and the mean and variance of n mean and variance of the additive noise parameters based on this distribution and the test utterance itself Models the effect of linear filtering and additive noise as a shift of the means and a scaling of the variances of the Gaussians in the Gaussian mixture distribution www.cs.cmu.edu /~rsingh/homepage/SPINEcompensation.html   (755 words)

 Linear Prediction analysis   (Site not responding. Last check: 2007-10-14) Linear prediction analysis of speech is historically one of the most important speech analysis techniques. The basis is the source-filter model where the filter is constrained to be an all-pole linear filter. This amounts to performing a linear prediction of the next sample as a weighted sum of past samples: svr-www.eng.cam.ac.uk /~ajr/SA95/node38.html   (78 words)

 High Pass Filter - Java Experiment   (Site not responding. Last check: 2007-10-14) Hence it is useful as a filter to block any unwanted low frequency components of a complex signal whilst passing higher frequencies frequencies. The basic quantities which describe this circuit are similar to those used for the Low Pass Filter. As with the low-pass filter, the circuit's behaviour can be understood as arising due to the time taken to change the capacitor's charge when we alter the applied input voltage. www.st-andrews.ac.uk /~www_pa/Scots_Guide/experiment/highpass/hpf.html   (521 words)

 Theory of linear networks   (Site not responding. Last check: 2007-10-14) But more than one network is consistent with the same linear filter. In other words, any network with W and F satisfying this equation is consistent with a linear filter D. This model could be applied to a single neuron in culture, which grows synaptic connections onto itself (autapses). hebb.mit.edu /courses/9.641/2000/lectures/lecture05.html   (435 words)

 Amazon.com: Cokin Linear Polarizer Filter X-Pro Series: Camera & Photo   (Site not responding. Last check: 2007-10-14) Light rays which are reflected by any surface become polarised and polarising filters are used to select which light rays enter your camara lens. They allow you to remove unwanted reflections from non-metallic surfaces such as water, glass etc. They also saturate colors and increase contrast. Linear polarizers work with older camera meters; circular polarizers are designed for today's newer slpit-beam metering systems used in auto focus cameras; check your camera's manual. www.amazon.com /exec/obidos/tg/detail/-/B00009R7NC?v=glance   (336 words)

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