Motorola Corporation

At&t Company and At&t Bell Laboratories

Peter J McLane

Sangil Park

Dion M Funderburk

Mohsen Kavehrad

In an asynchronous communication system such as a V.32 modern (80), an input signal is sampled at a near-end clock rate. Each sample is then interpolated in an interpolation filter (92) to provide corresponding interpolated values. The interpolation filter (92) uses a selected one of a predetermined number of sets of windowed sinc function coefficients, each set having a successively greater phase offset. A time drift between near-end and far-end clocks is measured by tracking the coefficient shift in a passband phase-splitting, fractionally-spaced equalizer (95). When the time drift exceeds a threshold, a subsequent set of windowed sinc function coefficients is selected. When the time drift exceeds the threshold after the last set of coefficients is used, the first set is again selected and an interpolated value is either dropped or repeated in forming the far-end data samples.

Method and apparatus for asynchronous timing recovery using

A digital receiver (10) has a symmetrical base band processor (28, 30, 32, 34, and 36) which concurrently provides a left and a right channel of audio information. Because of the symmetrical design of the base band processor, each of the left and right channels of information has perfectly balanced phase and amplitude with respect to each other. The base band processor includes an adaptive gain compensator (28), multipliers (30, 32), and high pass filters (34, 36). Compensator (28) iteratively derives a gain factor which is multiplied by both an in-phase component and a quadrature component of a quadrature modulated input signal to respectively provide a composite of the left and right channels and a difference between the left and right channels. Subsequently, adders (44, 48) arithmetically manipulate the composite and difference of the channels to separate the left and the right audio information.

Symmetrically balanced phase and amplitude base band processor for a

The present invention relates to a wireless PBX network wherein direct sequence spread spectrum multiple access is used for voice and data communications to support a plurality of local-local and local-external calls. The present wireless PBX arrangement comprises a plurality of local user transceivers using a first separate unique chip sequence patterns for information communication and a second common chip sequence pattern for call-set up; and a central PBX comprising (a) a plurality of PBX transceivers, each of which uses a separate first chip sequence pattern which is matched to a corresponding local user transceiver; (b) a switching means for interconnecting local users to each other or to an external network via the associated PBX transceivers; and (c) a call set-up receiver responsive solely to initial call set-up information sent by any user using the second common chip sequence pattern. Optional selection diversity or equal gain combining diversity and/or error correction encoding may also be included in the transceivers.

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Kingston, Canada

Peter J McLane