Time-Encoding ADC Modulator Feedback for Ring Oscillator Linearity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional time-encoding modulators, particularly those using ring oscillators, suffer from poor linearity, which results in distortion and non-linearities in digital output signals, especially in audio applications where high linearity and low distortion are required.
Innovation Solution
The proposed solution involves an analogue-to-digital converter circuitry that includes a time-encoding modulator with a comparator and loop filter generating a pulse-width-modulated signal, a controlled oscillator with a control switch controlled by the PWM signal, and a feedback mechanism that accounts for timing errors between the PWM signal and the switch control signal to improve linearity and reduce distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a ring oscillator VCO is used for ADC, then power consumption and circuit area are reduced, but linearity deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the output of the ring oscillator is fed back through a divider to the PWM modulator. This feedback loop allows the system to compensate for non-linearities in the VCO by adjusting the PWM duty cycle based on the actual oscillation frequency, thereby maintaining linearity while using the power-efficient ring oscillator architecture.
Solution Approach 2:
The patent introduces a PWM modulator as an intermediary between the input signal and the ring oscillator VCO. This PWM modulator converts the input voltage to a pulse-width modulated signal that controls the VCO, providing linearization by ensuring that the VCO receives a properly conditioned control signal that compensates for its inherent non-linearities.
2Manufacturing precision
If PWM modulator is added to linearize VCO output, then linearity is improved, but device complexity increases
Solution Approach 1:
The patent combines the PWM modulator and the VCO into a single integrated ADC architecture. The PWM modulator is directly coupled to the ring oscillator, and the feedback path merges the VCO output with the PWM input, creating a unified system that achieves linearization without requiring separate external components or complex additional circuitry.
Solution Approach 2:
The ring oscillator serves multiple functions: it acts as both the VCO for frequency generation and as part of the feedback mechanism for linearization. The same oscillation signal is used for both the output frequency generation and for generating the feedback signal that drives the PWM modulator, reducing the need for additional dedicated components.
3Object-generated harmful factors
If feedback signal includes timing error information, then distortion is reduced, but measurement precision requirements increase
Solution Approach 1:
The patent implements feedback that includes timing error information, but does not require perfect timing measurement. The feedback signal incorporates sufficient timing error information to reduce distortion to acceptable levels without demanding ultra-precise timing measurement capabilities, accepting partial correction rather than attempting perfect linearization.
Data Source
AI summary
This application relates to analog-to-digital converter (ADC) circuitry (200). A time-encoding modulator (TEM 201) has a comparator (104) and a loop filter (105) configured to generate a pulse-width-modulated (PWM) signal (SPWM) in response to an input signal (SIN) and a feedback signal (SFB). A controlled oscillator, such as a VCO (202) receives the PWM signal and generates an output oscillation signal (SOSC) with a frequency that varies based on a drive signal at a drive node (109), e.g. a drive node of a ring oscillator (107). The controlled oscillator (202) comprises at least one control switch (112) controlled by a switch control signal (S1) generated from the received PWM signal so as to control the drive strength of the drive signal applied to the drive node (109). The feedback signal (SFB) for the TEM (201) is derived from the controlled oscillator (202) so as to include any timing error between the PWM signal and the switch control signal (S1) applied to said control switch.