Controlled Oscillator Tuning for Temperature-Stable Frequency Output

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Solution Overview

Problem

Existing methods for generating precise frequencies in electronic systems, such as crystal-less clock generators and crystal-based reference clocks, face limitations in accuracy and require continuous operation of a second reference oscillator, leading to inefficiencies in hardware and power usage, as well as limitations in producing multiple frequencies from a single device.

Innovation Solution

A method and apparatus that utilize a controlled oscillator with a frequency ratio measurement circuit to determine and adjust the tuning of the oscillator to produce a desired, temperature-independent frequency without the need for a continuously operating reference oscillator, employing a polynomial or table-based approach to relate temperature and frequency, allowing for 'on the fly' frequency selection and simplifying inventory management.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a crystal-based reference clock is used to tune a controlled oscillator, then frequency precision can be achieved, but hardware area and power consumption increase due to requiring two continuously operating oscillators

Engineering Contradiction:

Improvefrequency precisionVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent extracts only the necessary function of the reference oscillator (frequency measurement) and removes the continuous operation requirement. By measuring frequency ratio intermittently and using polynomial compensation for temperature effects, the system eliminates the need for a continuously operating reference oscillator while maintaining frequency precision.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The system performs preliminary frequency ratio measurements and polynomial coefficient determination during production testing. This preliminary action allows the controlled oscillator to be accurately tuned without requiring continuous reference oscillator operation during normal use, reducing power consumption while maintaining precision.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If a crystal-based reference clock is used to tune a controlled oscillator, then frequency precision can be achieved, but hardware area increases due to requiring two oscillators

Engineering Contradiction:

Improvefrequency precisionVSAvoidhardware area

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent merges the frequency measurement function with the controlled oscillator itself by using it to measure its own frequency ratio. This eliminates the need for a separate reference oscillator hardware component, reducing hardware area while maintaining the ability to achieve precise frequency tuning.

Inventive Principle:

Principle #5Merging (Combining)

3Measurement precision

If temperature compensation is used to adjust VCO output based on measured temperature, then frequency accuracy can be achieved at a particular temperature, but the system cannot produce other frequencies accurately

Engineering Contradiction:

Improvefrequency accuracyVSAvoidfrequency flexibility

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent implements dynamic frequency tuning capability by allowing the controlled oscillator to be retuned to different frequencies while using the same polynomial compensation approach. The system measures the frequency ratio at the new desired frequency and updates the polynomial coefficients accordingly, enabling accurate operation at multiple frequencies rather than being fixed to a single production-test frequency.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the polynomial coefficients based on the desired frequency and measured temperature. By updating these parameters dynamically, the system maintains frequency accuracy across different operating frequencies and temperature conditions, achieving both precision and versatility.

Inventive Principle:

Principle #35Parameter changes

4Measurement precision

If a crystal-based reference clock is used, then frequency reference can be provided, but spurs may arise from energy at the reference clock frequency leaking into the output clock

Engineering Contradiction:

Improvefrequency referenceVSAvoidspurs

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS8975970B2Producing a desired frequency using a controlled oscillator with known temperature sensitivity

Publication Date: 2015.03.10 SILICON LABORATORIES INC

AI summary

A controlled oscillator is tuned to produce a desired, temperature independent frequency. A first frequency ratio is determined between a first frequency of the output signal generated by the controlled oscillator and a frequency of an output signal from another oscillator. The first frequency is determined based on a sensed temperature. A desired frequency of the output signal of the controlled oscillator is used to determine a desired frequency ratio between the desired frequency and the frequency of the output signal from the other oscillator. The controlled oscillator is tuned and the frequency ratio measured until the tuning has caused the desired frequency ratio to be achieved, thereby causing the controlled oscillator to provide the desired frequency.