Analysis of quantized feedback low-frequency restoration in digital regenerators

Quantized feedback, a DC restoration technique utilizing decision feedback equalization, can be used to compensate for unavoidable low-frequency cutoff in digital regenerators. An analysis is provided of the error probability and sensitivity to timing offsets of quantized feedback for a single-pole high-pass filter regenerator characteristic. Error probability is expressed in terms of the moments of the intersymbol interference (ISI), and these moments are calculated using the Markov chain properties of the ISI. To keep degradations small, the low-frequency cutoff should be no greater than 15% of the bit rate