Digital Signal Processing Circuit Using Dithering for Noise Suppression

Solution Overview

Problem

In high-speed data transmission systems, the use of fixed-point arithmetic in Fourier transform circuits introduces quantization noise, leading to system instability and non-convergence due to insufficient bit length, which cannot be effectively suppressed by increasing bits without significant circuit area and energy costs.

Innovation Solution

A digital signal processing circuit that adds a random number sequence to the input signal before Fourier transformation, masking specific noise patterns and stabilizing the system by ensuring the power spectral density of the noise exceeds that of the noise pattern, thereby preventing coefficient drift and convergence issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the number of bits used by the Fourier transform circuit is increased to suppress quantization noise, then the noise suppression is improved, but the circuit area and energy consumption increase significantly

Engineering Contradiction:

Improvenoise suppressionVSAvoidcircuit area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

A dithering signal (random noise sequence) is introduced as an intermediary element between the input signal and the Fourier transform circuit. This dithering signal masks the quantization noise by raising the overall noise floor, preventing the formation of harmful colored noise patterns while allowing the use of lower-bit Fourier transform circuits, thus reducing circuit area without sacrificing noise suppression performance

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention converts the harmful quantization noise into a beneficial masking effect by adding a dithering signal. The quantization noise, instead of forming harmful colored patterns, is masked by the random dithering signal, transforming it into benign white noise that does not affect system stability. This allows lower-bit circuits to be used effectively

Inventive Principle:

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

2Reliability

If the number of bits used by the Fourier transform circuit is increased to suppress quantization noise, then the noise suppression is improved, but the energy consumption increases significantly

Engineering Contradiction:

Improvenoise suppressionVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by stationary object

Solution Approach 1:

A dithering signal (random noise sequence) is introduced as an intermediary element between the input signal and the Fourier transform circuit. This dithering signal masks the quantization noise by raising the overall noise floor, preventing the formation of harmful colored noise patterns while allowing the use of lower-bit Fourier transform circuits, thus reducing circuit area without sacrificing noise suppression performance

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention converts the harmful quantization noise into a beneficial masking effect by adding a dithering signal. The quantization noise, instead of forming harmful colored patterns, is masked by the random dithering signal, transforming it into benign white noise that does not affect system stability. This allows lower-bit circuits to be used effectively

Inventive Principle:

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

3Area of stationary object

If the word length is reduced to save circuit area, then the circuit area is reduced, but colored noise patterns are generated that affect equalizer operation and system stability

Engineering Contradiction:

Improvecircuit areaVSAvoidsystem stability

Core Design Contradiction:

Area of stationary objectVSStability of the object's composition

Solution Approach 1:

A dithering signal (random noise sequence) is introduced as an intermediary element between the input signal and the Fourier transform circuit. This dithering signal masks the quantization noise by raising the overall noise floor, preventing the formation of harmful colored noise patterns while allowing the use of lower-bit Fourier transform circuits, thus reducing circuit area without sacrificing system stability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The dithering signal is applied in advance to the input signal before it enters the Fourier transform circuit. This preliminary action prevents the quantization noise from developing into harmful colored noise patterns during the transformation process, thereby preemptively protecting system stability before the noise can cause damage

Inventive Principle:

Principle #9Preliminary anti-action

Data Source

PatentUS20210392026A1Signal processing circuit in digital domain and method thereof

Publication Date: 2021.12.16 REALTEK SEMICON CORP

AI summary

A signal processing method in a digital-domain includes: adding a random number sequence signal into a time-domain input signal to generate a time-domain processed input signal; performing a Fourier transform operation upon the time-domain processed input signal to generate a frequency-domain processed input signal; performing an equalizer operation upon the frequency-domain processed input signal to generate a frequency-domain output signal according to coefficients of the equalizer operation; performing an inverse Fourier transform operation upon the frequency-domain output signal to generate a time-domain output signal; generating a decision output signal and generating a time-domain error signal according to the time-domain output signal; and determining the coefficients according to the time-domain error signal and the frequency-domain processed input signal.