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Discrete-Time Signal Processing (A Review). Sampling. CT. DT. Zero-Order Hold (ZOH). Sampling. Impulse train. Sampling. δ (t-nT). Spectrum of Sampled Signal ( Ω s >2 Ω N ). The spectrum of the sampled signal is periodic in Ω s =2 π /T. Spectrum of Sampled Signal ( Ω s <2 Ω N ).
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Sampling CT DT
Sampling Impulse train
Sampling δ(t-nT)
Spectrum of Sampled Signal (Ωs>2ΩN) The spectrum of the sampled signal is periodic in Ωs=2π/T.
Spectrum of Sampled Signal (Ωs<2ΩN) • Aliasing (folding) results in irreversible signal distortion. • Can only be avoided by using sufficiently high sample rate, or band- limit the input signal with a coarse, continuous-time filter – AAF.
Reconstruction Filter (Nyquist) Reconstruction filter = “smoothing” filter = “interpolation” filter