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Can a reconstruction filter be performed in real time?
The ideal sinc waveform has an infinite response to a signal, in both the positive and negative time directions, which is impossible to perform in real time – as it would require infinite delay. Consequently, real reconstruction filters typically either allow some energy above the Nyquist rate, attenuate some in-band frequencies, or both.
How is the reconstruction filter used in digital logic?
Thus, the reconstruction filter smooths the waveform to remove image frequencies (copies) above the Nyquist limit. In doing so, it reconstructs the continuous time signal (whether originally sampled, or modelled by digital logic) corresponding to the digital time sequence.
How is a reconstruction filter used in a DAC?
Reconstruction filter. In a mixed-signal system (analog and digital), a reconstruction filter is used to construct a smooth analog signal from a digital input, as in the case of a digital to analog converter (DAC) or other sampled data output device.
How are techniques used to reconstruct a signal?
There are many techniques that can be used to reconstruct a signal and the selection of the technique to be used is depends on what accuracy of reconstruction is required and how oversampled the signal is.
How to use a DAC reconstruction filter for sinc?
DAC Reconstruction Filter • Need for and requirements depend on application • Tasks: – Correct for sinc distortion – Remove “aliases” (stair-case approximation) B f s /2 0 0.5 1 1.5 2 2.5 3 x 10 6 0 0.5 1 DAC Input 0 0.5 1 1.5 2 2.5 3 x 10 6 0 0.5 1 sinc 0 0.5 1 1.5 2 2.5 3 x 10 6
Why are reconstruction filters called anti-imaging filters?
Reconstruction filters are therefore sometimes called anti-imaging filters. In practice, the specification of the reconstruction filter will depend on the spectrum of the input signal to the digital-to-analogue converter, u (n ), and the degree of attenuation required in the frequency images.
How does the Nyquist reconstruction filter actually work?
The rate conversion and lowpass filtering can be made digitally to have sharp cutoff without aliasing. Same thing when playing audio back, upsample and reconstruct digitally the signal to 192 kHz for playback and the DAC output analog filter can be cheap and simple.