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US 11,671,105 B2Granted
Frequency tracking loop using a scaled replica oscillator for injection locked oscillators
AssigneeCisco Technology, Inc.
InventorsAbhishek Bhat, Romesh Kumar Nandwana, Kadaba Lakshmikumar, Pavan Kumar Hanumolu
Life of this patent
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Abstract
An accurate replica oscillator-based frequency tracking loop (FTL) is provided. The replica oscillator used in the FTL can be at a lower frequency and therefore can consume much lower power compared to a main oscillator, such as an injection locked oscillator (ILO). The proposed FTL accurately sets the free running frequency of an ILO across process, voltage and temperature (PVT). Techniques are also provided to compensate the gain and offset error between the replica oscillator and the ILO.
Claims20
An apparatus comprising:
- a main oscillator having a main oscillator control input, an injection input and a main oscillator output, and configured to provide at the main oscillator output a main oscillator signal at a first frequency based on a control voltage provided at the main oscillator control input;
- a replica oscillator having a replica oscillator control input and a replica oscillator output, and configured to provide at the replica oscillator output a replica oscillator signal at a second frequency based on a control voltage provided at the replica oscillator control input;
- a first frequency detector coupled to the main oscillator output and configured to output a main oscillator frequency value that is representative of a frequency of the main oscillator signal;
- a second frequency detector coupled to the replica oscillator output and configured to output a replica oscillator frequency value that is representative of a frequency of the replica oscillator signal;
- and
- one or more circuit elements coupled to the replica oscillator control input, wherein the one or more circuit elements are configured to adjust a voltage signal or current signal used to provide the control voltage to the replica oscillator control input based on a difference between the main oscillator frequency value and a frequency value representative of a frequency of an injection clock signal provided at the injection input of the main oscillator, wherein the control voltage causes the replica oscillator to have an oscillator gain that is scaled with respect to an oscillator gain of the main oscillator, wherein an oscillator gain is a ratio of change in free-running oscillator frequency to change in control voltage.
3 more elements
A method comprising:
- obtaining a main oscillator signal from a main oscillator at a first frequency based on a control voltage provided at a main oscillator control input;
- obtaining a replica oscillator signal from a replica oscillator at a second frequency based on a control voltage provided at a replica oscillator control input;
- detecting a frequency of the main oscillator signal to provide a main oscillator frequency value that is representative of the frequency of the main oscillator signal;
- detecting a frequency of the replica oscillator signal to provide a replica oscillator frequency value that is representative of the frequency of the replica oscillator signal;
- and
- adjusting a voltage signal or current signal to provide a control voltage to the replica oscillator control input based on a difference between the main oscillator frequency value and a frequency value representative of a frequency of an injection clock signal provided to the main oscillator, wherein the control voltage causes the replica oscillator to have an oscillator gain that is scaled with respect to an oscillator gain of the main oscillator, wherein an oscillator gain is a ratio of change in free-running oscillator frequency to change in control voltage.
3 more elements
An apparatus comprising:
- a main oscillator having a main oscillator control input, an injection input and a main oscillator output, and configured to provide at the main oscillator output a main oscillator signal at a first frequency based on a control voltage provided at the main oscillator control input;
- a replica oscillator having a replica oscillator control input and a replica oscillator output, and configured to provide at the replica oscillator output a replica oscillator signal at a second frequency based on a control voltage provided at the replica oscillator control input;
- a first frequency detector coupled to the main oscillator output and configured to output a main oscillator frequency value that is representative of a frequency of the main oscillator signal;
- a second frequency detector coupled to the replica oscillator output and configured to output a replica oscillator frequency value that is representative of a frequency of the replica oscillator signal;
- a processor configured to generate an error value based on a difference between the main oscillator frequency value and a frequency value representative of a frequency of an injection clock signal provided at the injection input of the main oscillator, and to integrate the error value over time to output an integrated error value;
- a digital-to-analog converter configured to convert the integrated error value to a voltage signal provided at a digital-to-analog converter output that is coupled to the main oscillator control input;
- and
- one or more circuit elements coupled between the digital-to-analog converter output and the replica oscillator control input, wherein the one or more circuit elements are configured to adjust a voltage signal or current signal used to provide a control voltage to the replica oscillator control input that causes the replica oscillator to have an oscillator gain that is scaled with respect to an oscillator gain of the main oscillator, wherein an oscillator gain is a ratio of change in free-running oscillator frequency to change in control voltage.
5 more elements
Dependencies are inferred from the claim text.