Center-Tap Biased VCO Circuit for Low-Jitter High Frequencies

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Solution Overview

Problem

Voltage-controlled oscillator circuits face significant jitter issues, particularly at high oscillation frequencies, which affect the stability and performance of high-performance computer systems, as variations in noise patterns between components increase jitter, limiting their ability to operate at desired frequencies.

Innovation Solution

The proposed solution involves a novel VCO circuit design where the center-tap bias voltage is shared between the inductor and coupling capacitors, reducing noise differences and jitter by providing a single source for bias voltage, thereby stabilizing the oscillation frequency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If separate bias voltage sources are used for inductor and coupling capacitors, then each component can be independently optimized, but noise differences increase and jitter worsens

Engineering Contradiction:

Improvejitter reductionVSAvoidbias voltage source configuration

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges separate bias voltage sources for the inductor and coupling capacitors into a single shared bias voltage source. This consolidation reduces noise differences between components and eliminates the need for multiple independent voltage sources, thereby reducing jitter while simplifying the overall circuit configuration.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The single bias voltage source is designed to serve multiple functions simultaneously: it provides bias voltage to both the inductor and the coupling capacitors. This multi-functional approach reduces component count and ensures consistent noise characteristics across all biased components, directly addressing the jitter problem.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Productivity

If VCO operates at higher oscillation frequencies, then performance increases, but jitter increases due to noise pattern variations

Engineering Contradiction:

Improveoscillation frequencyVSAvoidsignal stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent converts the harmful effect of noise pattern variations at high frequencies into a benefit by using a shared bias voltage source. The common noise reference created by the shared source causes noise patterns to correlate between the inductor and coupling capacitors, transforming what would be detrimental uncorrelated noise into beneficial correlated noise that cancels out, thereby maintaining signal stability at high oscillation frequencies.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If shared bias voltage is used for inductor and coupling capacitors, then jitter is reduced through noise correlation, but noise filtering requirements increase

Engineering Contradiction:

Improvejitter reductionVSAvoidnoise filtering circuitry

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The shared bias voltage source creates a self-filtering effect where the correlated noise from the inductor and coupling capacitors naturally cancels out. The circuit leverages its own noise characteristics to achieve jitter reduction without requiring additional external noise filtering components, thereby maintaining simplicity while achieving the desired reliability improvement.

Inventive Principle:

Principle #25Self-service

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This design reduces jitter and enhances system reliability, enabling VCO circuits to operate at higher oscillation frequencies with improved stability, thus supporting higher performance in computer systems.

Implementation Method 1

A capacitance of the varactor is dependent upon a control voltage

Methodology Applied

Scientific EffectVaractor effect: Capacitance

Implementation Method 2

The voltage-controlled oscillator comprises a varactor, an inductor, and a coupling capacitor

Methodology Applied

Scientific EffectLC resonance: Resonance

Data Source

PatentUS11496094B1Voltage-controlled oscillator with centertap bias

Publication Date: 2022.11.08 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

A voltage-controlled oscillator comprises a varactor. A capacitance of the first varactor is dependent upon a control voltage. The voltage-controlled also comprises an inductor. The inductor is connected to a center-tap connection. The voltage-controlled oscillator also comprises a power source. The power source is configured to provide a bias voltage to the inductor through the center-tap connection. The voltage-controlled oscillator also comprises a coupling capacitor. The coupling capacitor is located between the inductor and the varactor. The voltage-controlled oscillator also comprises a coupling resistor. The coupling resistor is located between the coupling capacitor and the center-tap connection. The center-tap connection provides the bias voltage to the coupling capacitor through the coupling resistor.