VCO Compensation Module Reducing Frequency Pushing

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Solution Overview

Problem

Voltage-controlled oscillators in phase-locked loop circuits are sensitive to supply voltage variations, leading to frequency changes and phase shifts, which can result in communication devices failing to meet specifications due to the 'frequency pushing' phenomenon.

Innovation Solution

A compensation module and method that includes a compensation circuit and a polarity selection circuit, dynamically adjusting the capacitance of varactors to neutralize the native frequency pushing by generating a compensation frequency pushing with adjustable polarity and magnitude, thereby minimizing overall frequency changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the VCO is designed to be sensitive to supply voltage changes for frequency tuning, then frequency control capability is improved, but frequency stability deteriorates due to frequency pushing

Engineering Contradiction:

Improvefrequency control capabilityVSAvoidfrequency stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The compensation module applies a preliminary counteracting action by generating a compensation frequency pushing effect that opposes the native frequency pushing. The polarity selection circuit and compensation circuit work together to produce an opposite frequency shift that cancels out the harmful effect of supply voltage variations on the output oscillation frequency.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The invention changes the capacitance parameter of the varactor in the compensation circuit dynamically. By adjusting the capacitance value based on the detected polarity and magnitude of frequency pushing, the system optimizes the compensation effect to maintain frequency stability while preserving frequency control capability.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If the capacitance of varactors is fixed, then circuit simplicity is maintained, but frequency tuning range and compensation flexibility are limited

Engineering Contradiction:

Improvecircuit simplicityVSAvoidfrequency tuning range

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The invention transforms the static capacitance value into a dynamic parameter by introducing a tuning mechanism that adjusts the varactor capacitance based on the frequency pushing characteristics. This allows the circuit to adapt to different operating conditions and supply voltage variations while maintaining a relatively simple overall structure.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The calibration circuit performs preliminary characterization of the VCO's frequency pushing behavior before normal operation. This preliminary action stores the detected polarity and magnitude information, which is then used to pre-configure the compensation circuit for optimal performance without requiring complex real-time adjustments.

Inventive Principle:

Principle #10Preliminary action

3Device complexity

If no compensation mechanism is used, then device complexity is reduced, but communication device performance fails to meet specifications

Engineering Contradiction:

Improvedevice complexityVSAvoidperformance specification compliance

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The compensation module acts as an intermediary between the supply voltage variations and the VCO output. It mediates the harmful frequency pushing effect by introducing a compensating signal that counteracts the frequency deviations, thereby ensuring specification compliance without requiring fundamental redesign of the entire communication device.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The solution effectively reduces the sensitivity of the output oscillation signal to supply voltage changes, ensuring the phase-locked loop circuit meets specifications by maintaining a consistent output oscillation frequency despite variations in supply voltage.

Implementation Method 1

changes of capacitance value result in changes of the output oscillation frequency fout

Methodology Applied

Scientific EffectCapacitance variation with voltage: Capacitance

Implementation Method 2

dynamically adjusting the capacitance of varactors to neutralize the native frequency pushing by generating a compensation frequency pushing

Methodology Applied

Scientific EffectCapacitance variation with voltage: Capacitance

Data Source

PatentUS10826429B2Compensation module, oscillation circuit, and associated compensation method capable of reducing sensitivity of output oscillation signal

Publication Date: 2020.11.03 MEDIATEK INC

AI summary

A compensation module, an oscillation circuit and associated compensation method for reducing an oscillation frequency variation in an output oscillation signal of a voltage-controlled oscillator (VCO) core are provided. The compensation module includes a compensation circuit and a polarity selection circuit. The compensation circuit has a capacitance value related to voltages of a first and a second receiving terminals. The oscillation frequency variation is changed with the capacitance value. The polarity selection circuit conducts a periodic regulated signal to one of the first receiving terminal and the second receiving terminal. The polarity selection circuit conducts a filtered bias signal to the other of the first receiving terminal and the second receiving terminal. The periodic regulated signal is sensitive to a regulated voltage variation, and the filtered bias signal is insensitive to the regulated voltage variation.