Oscillators – Ring oscillators
Reexamination Certificate
2002-11-26
2004-10-05
Mis, David (Department: 2817)
Oscillators
Ring oscillators
C331S175000, C703S014000
Reexamination Certificate
active
06801095
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related, in general, to electronic oscillators, and more particularly, to an interconnected multi-stage oscillator apparatus and a corresponding system, program and method for designing an interconnected multi-stage oscillator.
BACKGROUND OF THE INVENTION
Oscillators are utilized in a wide variety of applications, such as voltage controlled oscillators used in phase-locked loops. Such oscillators often suffer from certain defects, such as instability and lock up. In a particular mode of oscillation, various prior art oscillators may suffer catastrophic changes, such as collapsing to a lower frequency of oscillation in a different mode pattern.
One such prior art oscillator is illustrated in Sun et al. U.S. Pat. No. 6,075,419, issued Jun. 13, 2000 (the “Sun patent”). The Sun patent illustrates a 5-stage ring oscillator, where each stage is an inverter. There are two inputs to each inverter, one input being the output from the preceding stage, and the other input being the inverted output from a succeeding stage. While the oscillator of the Sun patent allows for adjustment of the gain in the various stages, using a control signal, it continues to suffer from instability problems, including the catastrophic problem of collapsing into a bad mode of oscillation. These problems of the oscillator of the Sun patent are illustrated in
FIGS. 17 and 18
, discussed in greater detail below.
Multi-stage oscillators have, in the prior art, been highly limited in terms of frequency characteristics. Most of these multi-stage oscillators are unable to achieve the desired frequency range with use of additional stages, because given their various designs, these additional stages actually lower the maximum frequency of operation.
Other prior art oscillators are also subject to these instability problems. The prior art does not provide a consistent methodology both to guarantee stability of oscillation of a desired mode of oscillation, and to predict the dynamics of the oscillator in operation. In addition, the prior art does not provide for any type of interconnected oscillator having more than five stages and more than two inputs per stage, or any design process to create such multi-stage interconnected oscillators having the desired stability characteristics. In addition, the prior art does not provide for any ability to provide higher frequencies of oscillation by increasing the number of stages employed.
REFERENCES:
patent: 6150894 (2000-11-01), Seng et al.
Agere Systems Inc.
Gamburd Nancy R.
Mis David
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