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The group delay and phase delay properties of a linear time-invariant (LTI) system are functions of frequency, giving the time from when a frequency component of a time varying physical quantity—for example a voltage signal—appears at the LTI system input, to the time when a copy of that same frequency component—perhaps of a different physical phenomenon—appears at the LTI system output.
A PMD compensation system is a device which uses a polarization controller to compensate for PMD in fibers.Essentially, one splits the output of the fiber into two principal polarizations (usually those with dτ dω = 0, i.e. no first-order variation of time-delay with frequency), and applies a differential delay to re-synchronize them.
DDEs are also called time-delay systems, systems with aftereffect or dead-time, hereditary systems, equations with deviating argument, or differential-difference equations. They belong to the class of systems with the functional state , i.e. partial differential equations (PDEs) which are infinite dimensional, as opposed to ordinary ...
Group delay largely frequency-dependent; Here is an image showing the gain of a discrete-time Butterworth filter next to other common filter types. All of these filters are fifth-order. The Butterworth filter rolls off more slowly around the cutoff frequency than the Chebyshev filter or the Elliptic filter, but without ripple.
The bridged T topology is used for delay equalisation, particularly the differential delay between two landlines being used for stereophonic sound broadcasts. This application requires that the filter has a linear phase response with frequency (i.e., constant group delay) over a wide bandwidth and is the reason for choosing this topology.
An ideal delay line characteristic has constant attenuation and linear phase variation, with frequency, i.e. it can be expressed by =where τ is the required delay.. As shown in lattice networks, the series arms of the lattice, za, are given by
The Taylor series expansion of the group delay is = + +. Note that the two terms in and are zero, resulting in a very flat group delay at =. This is the greatest number of terms that can be set to zero, since there are a total of four coefficients in the third-order Bessel polynomial, requiring four equations in order to be defined.
In optics, group-velocity dispersion (GVD) is a characteristic of a dispersive medium, used most often to determine how the medium affects the duration of an optical pulse traveling through it. Formally, GVD is defined as the derivative of the inverse of group velocity of light in a material with respect to angular frequency , [ 1 ] [ 2 ]