Controlled Oscillator ADC Offset Switching to Prevent Locking

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Solution Overview

Problem

In voltage-controlled oscillator (VCO) analog-to-digital converters, coupling between oscillators can lead to locking, resulting in output code errors and increased noise due to similar or equal frequencies and parasitic coupling.

Innovation Solution

Introducing a disturb signal to the analog interface or controlled oscillators to create an offset between their output signals, preventing locking by ensuring they oscillate at the same frequency only briefly, thus reducing layout space and costs compared to isolation techniques.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If two controlled oscillators are used with similar or equal frequencies in a VCO ADC, then the ADC can operate with reduced component count and integrated circuit fabrication simplicity, but coupling between oscillators causes locking that leads to output code errors and increased noise

Engineering Contradiction:

Improveoscillator configurationVSAvoidoutput code accuracy

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent applies preliminary anti-action by introducing a disturb signal to one or both controlled oscillators before coupling effects can cause locking. This disturb signal creates an offset frequency that prevents the oscillators from synchronizing, thereby preemptively counteracting the harmful coupling effect while maintaining the benefit of using two oscillators with similar base frequencies

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The patent changes the frequency parameter of the controlled oscillators by superimposing a disturb signal with a specific frequency offset. This parameter modification ensures that even though the oscillators have similar base frequencies, the introduced frequency offset prevents locking while allowing the system to maintain its integrated circuit fabrication simplicity

Inventive Principle:

Principle #35Parameter changes

2Reliability

If isolation techniques are used to prevent coupling between oscillators, then locking is prevented, but layout space and manufacturing costs increase

Engineering Contradiction:

Improvelocking preventionVSAvoidlayout space

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent replaces the mechanical/physical isolation approach (spatial separation, shielding, or grounding techniques) with a signal processing approach. Instead of physically isolating the oscillators through layout techniques, a disturb signal is injected to electronically prevent locking, thereby eliminating the need for additional layout space while maintaining reliable locking prevention

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS20220123756A1Offset switching to prevent locking in controlled oscillator analog-to-digital converters

Publication Date: 2022.04.21 INFINEON TECHNOLOGIES AG

AI summary

A controlled oscillator Analog-to-Digital Converter (ADC) includes an analog interface configured for receiving an analog differential input signal, and configured for providing a differential control signal; first and second controlled oscillators configured for receiving the differential control signal; and a frequency-to-digital converter having a first input coupled to an output of the first controlled oscillator, a second input coupled to an output of the second controlled oscillator, and an output for providing a digital output signal proportional to the analog differential input signal, wherein the analog interface or at least one of the first and second controlled oscillators is configured for receiving at least one disturb signal to prevent locking between the first and second controlled oscillators.