MULTI-PHASE REALIGNED VOLTAGE-CONTROLLED OSCILLATOR AND PHASE-LOCKED LOOP INCORPORATING THE SAME
First Claim
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1. A multiphase-realigned voltage-controlled oscillator (VCO) circuit, comprising:
- a plurality of inverting stages coupled together in series into a ring, each of these inverting stages in the ring providing an oscillating voltage signal to the next stage in the ring with a relative phase delay between the stages automatically adjusting itself according to the number of stages in the ring, each inverting stage in the ring responsive to a control voltage input to provide a long-term adjustment of propagation time delay through each inverting stage in the ring and hence adjusting the oscillating frequency of the ring to a target frequency; and
an output stage coupled to an output of one of the inverting stages, the output stage configured to provide a VCO clock output;
wherein each of the inverting stages in the ring is further coupled to receive in parallel a realignment current impulse, these inverting stages responsive to said realignment current impulse effective to immediately shift the phase of the oscillating voltage signal output from each stage, whereby an overall phase realignment of the VCO clock output is achieved after a relative phase readjustment between the stages.
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Abstract
A multi-phase realigned voltage-controlled oscillator (MRVCO) achieves phase realignment based on charge injection in the VCO stages with the injection amount proportional to the instantaneous phase error between the VCO output clock and a reference clock. The MRVCO may be incorporated as part of an implementation of a multi-phase realigned phase-locked loop (MRPLL). A separate phase detector, as well as a specific realignment charge pump, may be provided in the PLL for controlling the VCO. The VCO has lower phase modulation noise, so that the PLL has very large equivalent bandwidth.
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Citations
13 Claims
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1. A multiphase-realigned voltage-controlled oscillator (VCO) circuit, comprising:
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a plurality of inverting stages coupled together in series into a ring, each of these inverting stages in the ring providing an oscillating voltage signal to the next stage in the ring with a relative phase delay between the stages automatically adjusting itself according to the number of stages in the ring, each inverting stage in the ring responsive to a control voltage input to provide a long-term adjustment of propagation time delay through each inverting stage in the ring and hence adjusting the oscillating frequency of the ring to a target frequency; and
an output stage coupled to an output of one of the inverting stages, the output stage configured to provide a VCO clock output;
wherein each of the inverting stages in the ring is further coupled to receive in parallel a realignment current impulse, these inverting stages responsive to said realignment current impulse effective to immediately shift the phase of the oscillating voltage signal output from each stage, whereby an overall phase realignment of the VCO clock output is achieved after a relative phase readjustment between the stages. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A multiphase-realigned voltage-controlled oscillator (VCO) circuit, comprising:
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a plurality of inverting stages coupled together in series into a ring, each of these inverter stages configured to provide an oscillating voltage signal to the next inverting stage in the ring with a relative phase delay between the stages automatically adjusting itself according to the number of stages in the ring;
a voltage-to-current converter coupled to receive a control voltage input and provide a mirrored bias current to each of the inverter stages to establish a propagation time delay through each inverter stage, and hence, establishing an oscillation frequency of the ring at a target frequency;
an output stage coupled to an output of one of the inverter stages of the ring, the output stage configured to provide a VCO clock output;
a phase detector coupled to receive and compare the phase of a stable reference clock signal with the VCO clock output and provide up/down control signals that are dependent upon whether the VCO clock output lags or leads the reference clock signal;
a charge pump coupled to receive the up/down control signals from the phase detector and operative to produce a realignment current impulse corresponding to the phase delay between the VCO clock output and the reference clock signal; and
a realignment current copy subcircuit coupled to receive the realignment current impulse from the charge pump and to provide copies thereof in parallel to current copy transistors within each of the inverter stages, such that within each inverter stage of the ring the copied realignment current impulse is superimposed upon the mirrored bias current effective to immediately shift the phase of the oscillating voltage signal output from each stage, whereby an overall phase realignment of the VCO clock output is achieved after a relative phase readjustment between the stages. - View Dependent Claims (8, 9)
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10. A multiphase-realigned phase-locked loop (PLL) circuit, comprising:
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a multiphase-realigned voltage-controlled oscillator (VCO) circuit of the ring type, operative to provide an oscillating clock output that is responsive both to a control voltage input to provide long-term adjustment of an oscillating frequency and also to a realignment current impulse applied in parallel to all ring stages of the VCO circuit to effect an immediate phase realignment within the ring stages and an overall phase realignment of the VCO clock output;
a divide-by-N circuit coupled to receive the VCO clock output and act upon VCO clock edges to generate a divided clock signal of 1/Nth frequency relative to the VCO clock output;
a main phase-frequency detection circuit configured to compare an average frequency of the divided clock signal with that of a stable reference clock over many clock cycles and to generate long-term up/down control signals as a result of such comparison; and
a main charge pump and a low pass filter configured to produce the control voltage input to the VCO circuit in response to the long-term up/down control signals. - View Dependent Claims (11, 12, 13)
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Specification