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Adaptive Phase Filter Canceler

IP.com Disclosure Number: IPCOM000100846D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Maddens, F: AUTHOR [+2]

Abstract

The error estimation and carrier phase tracking block is provided with an anti-phase filter device which eliminates any stationary low frequency noise from the phase of the signal.

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This is the abbreviated version, containing approximately 58% of the total text.

Adaptive Phase Filter Canceler

       The error estimation and carrier phase tracking block is
provided with an anti-phase filter device which eliminates any
stationary low frequency noise from the phase of the signal.

      Amplitude and delay distortions of a signal received by Data
Circuit Equipment are cancelled by means of an equalizer.
Nevertheless, some other improvements are still needed such as:
           Ph(s)     carrier frequency offset
           Ph(o)     carrier phase offset
           Ph(j)     carrier phase jitter which have to be cancelled.

      Previously, the demodulation function cancelled only carrier
phase offset and carrier frequency offset thanks to a second-order
filter operating in the demodulation feedback loop. So carrier phase
jitter could not be cancelled efficiently without degrading
performance in terms of the signal-to-noise ratio.

      Now an additional feature working in parallel with the function
previously described allows to cancel any sinusoidal carrier phase
jitter, found at the output of the equalizer, whose frequency is
found in the 0 to 300 Hz bandwidth.

      This feature is a phase predictor (P on the functional diagram)
fed with the same phase error (carried out from the decision process)
as the one feeding the second-order filter.

      This predictor, being in feedback form, has a tendency to be
unstable. To deal with the parameters contributing to thi...