Agilent Technologies, Inc.

Avago Technologies General IP (Singapore) Pte. Ltd.

Other

Brian Jeffrey Galloway

Gunter Steinbach

Thomas Allen Knotts

Ken A Nishimura

Charles E Moore

Michael Allen Robinson

Systems and methods of characterizing eye diagrams are described. In one aspect, at measurement times across a measurement interval spanning at least one unit interval of the input signal, corresponding levels of the input signal are classified into groups based on at least one threshold. An eye diagram characteristic width is derived based on a distribution across the measurement interval of the levels in one of the groups.

Characterizing eye diagrams

A linear PLL includes a VCO with first and second tuning elements. The first tuning element is adjusted in proportion to the phase error between an input signal and a VCO signal and the second tuning element is adjusted by an integral function of the phase error. By configuring the VCO with separate tuning elements that are separately adjusted in proportion to the phase error and by an integral function of the phase error, the 3dB bandwidth frequency of the linear PLL depends primarily on the phase detector gain and the VCO gain that is contributed from the proportional adjustment. A linear PLL with separate proportional and integral tuning elements can be designed to exhibit a relatively constant gain over a relatively large frequency range.

Linear phase-locked loop with dual tuning elements

The frequency changes in a bang-bang PLL that are generated using a digital phase detector's up/down signal are initially set to produce a faster pull-in rate and then reduced to produce a slower pull-in rate. The faster pull-in involves relatively large frequency changes and the slower pull-in rate involves smaller frequency changes. The changes in frequency of a bang-bang PLL can be implemented using a step size controller that includes timing control logic and step size logic. The function of the timing control logic is to control the timing of step size changes. The function of the step size logic is to set the step size of the frequency changes that are made by the VCO in response to the pd_up/down signal that is delivered directly to the VCO from the digital phase detector.

Controlling a voltage controlled oscillator in a bang-bang phase locked loop

An offset related to a feedback system for a VCO is quantified and then a parameter of the feedback system is adjusted in response to the quantified offset to correct for the offset. Correcting for offset in a feedback system can improve the performance of a PLL by reducing phase drift between the input signal and the VCO signal. The reduced phase drift can have benefits such as, for example, reduced bit errors and/or improved phase tracking accuracy.

Method and system for operating a feedback system for a voltage controlled oscillator that involves correcting for offset related to the feedback system

The 3 dB frequency bandwidth of a phase-locked loop (PLL) is determined by measuring the frequency of a voltage controlled oscillator (VCO) signal when an up charging current is applied, measuring the frequency of the VCO signal when a down charging current is applied, and then using the two frequency measurements to calculate the 3 dB frequency bandwidth of the PLL. The up and down charging currents can be applied through a charge current switch system and the frequency measurements can be made with a frequency counter, both of which are monolithically integrated with the PLL. The technique for measuring the 3 dB frequency bandwidth can be applied to a first order or a second PLL. When applied to a second order PLL, the technique includes an initial frequency centering operation.

Measuring the 3 dB frequency bandwidth of a phase-locked loop

A technique for correcting for DC offset in a phase locked loop involves generating digital phase information in response to an input signal and then generating an offset correction signal in response to the digital phase information. The digital phase information may include transition samples that are integrated to generate the offset correction signal. Integrating the transition samples helps to compensate for the effects of phase noise, especially phase noise that is contributed by the input signal and/or the recovered clock signal.

Correcting for DC offset in a phase locked loop

In one embodiment a system and method is arranged for bridging the dead-band when asynchronous signals are compared against each other. There is developed a pair of phase related signals from one of the signals, each phase related signal phase shifted from each other, but having the same frequency as the signal from which it was derived. The other frequency signal is compared against each of the phase-related developed signals to generate an error signal which quadrature rotates when the first and second signals are out of frequency with each other. A control signal is generated when the quadrature rotation is outside a certain limit. The error signal is controllably buffered to insure that the error signal only occurs when the frequencies are offset for a selected period of time.

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Campbell, CA, United States of America

Brian Jeffrey Galloway