Oscillators – Automatic frequency stabilization using a phase or frequency... – Particular frequency control means
Reexamination Certificate
1999-07-12
2001-03-06
Mis, David (Department: 2817)
Oscillators
Automatic frequency stabilization using a phase or frequency...
Particular frequency control means
C331S057000, C331S175000, C331S176000, C331S17700V, C331S179000, C327S158000, C327S280000, C327S281000, C375S376000
Reexamination Certificate
active
06198356
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to power supply and temperature compensation circuits for voltage controlled oscillators for example.
BACKGROUND OF THE INVENTION
Voltage controlled oscillators (VCO) are used in a number of circuits including phase lock loops (PLL) for example, which in turn can be used in radio tuning, multiplexer synthesisers, or clock extraction in optical fibre receivers for timing reference for example. To ensure low cost and minimal component count, the VCO is preferably realised as a fully integrated design of the PLL. However the demands of PLL performance such as low jitter, low power supply pushing, and high temperature stability often force PLL designers to use a more costly external voltage controlled crystal oscillator, making the PLL, more difficult and costly to manufacture.
Many electronic components now operate at reduced supply voltages, for example 3V, which makes them more susceptible to supply and temperature pushing. Current integrated VCO which compensate for such temperature and power supply variations have met with limited success and are discussed in more detail below.
OBJECT OF THE INVENTION
It is an object of the present invention to provide an improved temperature and power supply compensation method for VCO.
It is a further object of the present invention to provide an improved VCO.
SUMMARY OF THE INVENTION
In a first aspect the present invention provides a supply voltage pushing compensation circuit stage for use with a variable delay circuit stage comprising one or more delay stages and an analogue multiplexer arranged to control the amount of delay introduced by the delay stages; the compensation circuit comprising a transconductance stage connected to the multiplexer and arranged to produce a compensating current upon deviation from nominal supply voltage which changes said delay.
Preferably the transconductance stage comprises a first transistor having a base voltage provided by a constant current source and a second transistor having a base voltage provided by a voltage divider such that deviation from nominal supply voltage produces a voltage difference between said first and second transistor to produce said compensating current.
In a second aspect the present invention provides a temperature pushing compensation circuit stage for use with a variable delay circuit stage comprising one or more delay stages and an analogue multiplexer arranged to control the amount of delay introduced by the delay stages; the compensation circuit comprising a transconductance stage connected to the multiplexer and arranged to produce a compensating current upon deviation from nominal temperature which changes said delay.
Preferably the transconductance stage comprises a first transistor having a base voltage provided by a constant current source and a second transistor having a base voltage provided by a temperature dependent voltage divider such that deviation from nominal supply voltage produces a voltage difference between said first and second transistor to produce said compensating current.
In a third aspect the present invention provides a variable delay circuit stage comprising one or more delay stages and an analogue multiplexer arranged to control the amount of delay introduced by the delay stages; a supply voltage pushing compensation circuit stage comprising a transconductance stage connected to the multiplexer and arranged to produce a compensating current upon deviation from nominal supply voltage which changes said delay; and a temperature pushing compensation circuit stage comprising a transconductance stage connected to the multiplexer and arranged to produce a compensating current upon deviation from nominal temperature which changes said delay.
In a fourth aspect the present invention provides a voltage controlled oscillator comprising one or more variable delay circuit stages each comprising one or more delay stages and an analogue multiplexer arranged to control the amount of delay introduced by the delay stages; a supply voltage pushing compensation circuit stage comprising a transconductance stage connected to the multiplexer and arranged to produce a compensating current upon deviation from nominal supply voltage which changes said delay; and a temperature pushing compensation circuit stage comprising a transconductance stage connected to the multiplexer and arranged to produce a compensating current upon deviation from nominal temperature which changes said delay.
In a fifth aspect the present invention provides a Phase Lock Loop comprising a voltage controlled oscillator comprising one or more variable delay circuit stages each comprising one or more delay stages and an analogue multiplexer arranged to control the amount of delay introduced by the delay stages; a supply voltage pushing compensation circuit stage comprising a transconductance stage connected to the multiplexer and arranged to produce a compensating current upon deviation from nominal supply voltage which changes said delay; and a temperature pushing compensation circuit stage comprising a transconductance stage connected to the multiplexer and arranged to produce a compensating current upon deviation from nominal temperature which changes said delay.
In a sixth aspect the present invention provides a clock and data recovery circuit arrangement comprising a Phase Lock Loop comprising a voltage controlled oscillator comprising one or more variable delay circuit stages each comprising one or more delay stages and an analogue multiplexer arranged to control the amount of delay introduced by the delay stages; a supply voltage pushing compensation circuit stage comprising a transconductance stage connected to the multiplexer and arranged to produce a compensating current upon deviation from nominal supply voltage which changes said delay; and a temperature pushing compensation circuit stage comprising a transconductance stage connected to the multiplexer and arranged to produce a compensating current upon deviation from nominal temperature which changes said delay.
REFERENCES:
patent: 5349311 (1994-09-01), Mentzer
Forbes Robert James
Visocchi Pasqualino
Lee Mann Smith McWilliams Sweeney & Ohlson
Mis David
Nortel Networks Limited
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