Analog Devices,inc.

John Jerome Kornblum

David T Crook

Charles D Lane

Ken Gentile

Ziwei Zheng

Baeton Charles Rigsbee

Methods and structures are provided to improve the transfer functions of analog-to-digital converter systems. They address the converter error function that corresponds to a converter's transfer function. In particular, they provide a corrector with a corrector transfer function that defines a corrector error function which substantially mirrors at least a portion of the converter error function. The corrector processes the converter's output digital signals to realize corrector digital signals which are then combined with the original output digital signals to obtain a system with a system error function that is significantly reduced from the original converter error function.

Correction methods and structures for analog-to-digital converter transfer functions

Feedback methods and systems are provided to achieve rapid switching of oscillator frequencies without compromising operational feedback loop bandwidths that filter out spurious tones and phase noise to thereby enhance loop spectral and noise performance. The methods respond to frequency changes in a reference signal by providing an open-loop drive current to drive a feedback signal towards the reference signal. The drive current is terminated and the feedback control loop closed when the feedback signal is within a predetermined acquisition range of the reference signal. Preferably, the closed loop is initially configured with a first feedback bandwidth and is subsequently reconfigured with a second steady-state feedback bandwidth that is less than the first feedback bandwidth. The invention also provides a feedback control system that practices the invention's methods

Feedback methods and systems for rapid switching of oscillator frequencies

Direct digital synthesis (DDS) methods and structures are provided that increase DDS output frequencies f without requiring a corresponding increase in the rate f at which DDS structures must operate. An exemplary method generates a periodic stream of digital words at a clock frequency f wherein the words represent respective amplitudes of a predetermined periodic waveform, the periodic stream has a period P and the digital words are spaced by a phase step &phgr; . This method comprises the steps of a) with a count capacity C, counting modulo n&phgr; at a reduced clock frequency (1/n)f to thereby generate a primary substream of digital words, b) phase offsetting the primary substream to form n&minus;1 secondary substreams of digital words wherein the primary and secondary substreams are phase spaced by the phase step &phgr; , c) converting the digital words of each of the primary, and secondary substreams to converted digital words that represent respective amplitudes of the predetermined waveform, and d) interleaving the primary and secondary substreams to thereby form the periodic stream of digital words that occur at the clock frequency f .

Multiphase, interleaved direct digital synthesis methods and structures

Feedback methods and systems are provided to achieve rapid switching of oscillator frequencies without compromising operational feedback loop bandwidths that filter out spurious tones and phase noise to thereby enhance loop spectral and noise performance. The methods respond to frequency changes in a reference signal by providing an open-loop drive current to drive a feedback signal towards the reference signal. The drive current is terminated and the feedback control loop closed when the feedback signal is within a predetermined acquisition range of the reference signal. This is determined by successively comparing a feedback frequency of the feedback signal to a destination frequency of the reference signal over a comparison window of time. The invention also provides a feedback control system that practices the invention's methods.

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Greensboro, NC, United States of America

John Jerome Kornblum