Decision feedback equalization and carrier recovery in 140 Mbit QAM digital radio systems

The tracking behavior of a decision-feedback equalizer coupled to a carrier recovery loop in the presence of dynamic multipath-fading activity is studied. Minimum-phase/non-minimum-phase-type fading transitions, with notch-depth variation-rates up to 120 dB/s, and fadings sweeping across the signal band at 300 MHz/s, are considered. Free interaction between the two adaptive devices is allowed. Simulated tap gains are compared to those theoretically obtained to justify the observed RMS error increase, which can eventually lead to the system outage. The extra degree of freedom arising in the recovered carrier phase does not seem to disturb the behavior of the coupled system.<
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