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How are delay and distortion introduced by filters?
Filtering a signal introduces a delay. This means that the output signal is shifted in time with respect to the input. When the shift is constant, you can correct for the delay by shifting the signal in time. Sometimes the filter delays some frequency components more than others. This phenomenon is called phase distortion.
When does phase distortion occur in signal processing?
In signal processing, phase distortion or phase-frequency distortion is distortion, that is, change in the shape of the waveform, that occurs when (a) a filter’s phase response is not linear over the frequency range of interest, that is, the phase shift introduced by a circuit or device is not directly proportional to frequency,…
What is the phase response of a filter?
The phase response of a filter which linearly shifts the output with respect to the input is where K and L are nonnegative integers. 0, forx O. In addition to its shifting effect, filtering can cause the output picture to be close to or equal to the neg2tive of the input picture.
Is the phase of a digital filter linear?
Huang et al. [3] have dem- onstrated the significance of phase in digital image-processing filters. In general, the phase of a digital filter will have error. Linear phase, which does not degrade the phase of input sig- nals, cannot be obtained in causal, realizable IIR digital filters.
Why are linear phase filters called group delay?
Linear-phase filters delay the envelope of every signal by the same amount of time, called group delay, no matter what is the carrier frequency of the signal. They are called linear phase because their phase shift varies linearly with the frequency. NON-PHASE LINEAR FILTERS?
Which is the best way to filter a signal?
Filter the signal. The filtered signal is cleaner than the original, but lags in time with respect to it. It is also distorted due to the nonlinear phase of the filter. A look at the group delay introduced by the filter shows that the delay is frequency-dependent. Filter the signal using filtfilt.
What does a delay of 0.4µs mean?
Its period is 1/250,000Hz = 4µs. Therefore, a delay of 0.4µs means a phase shift of 1/10 of a period, or 360 degrees /10 = 36 degrees. However, if the signal frequency is multiplied by 2 (500kHz), its period is 2µs, and the same 0.4µs delay now means a phase shift of 1/5 of a period or 72 degrees.
How to make CIC compensation filter-signal processing?
This approach makes use that the sinc function in the passband can be reasonably approximated by a weighted cosine function. Therefore a raised cosine function in frequency, meaning b − ( α) c o s ( ω) can be used in cascade with the CIC filter as compensation.
How does a distortion analyzer do its job?
Distortion analyzers inject a low distortion sine wave into the input of the DUT and then extract that signal somewhere downstream from that point. The signal is fed into a very sharp notch filter to null out only the original sine wave frequency. Anything that remains is distortion products; noise and hum that were created in the DUT.
How are distortion levels measured in a DUT?
Anything that remains is distortion products; noise and hum that were created in the DUT. That level is compared to the level of the extracted signal prior to the filter and converted to a numerical, percentage, decibel figure, or whatever is desired, and displayed on a readout.