ADC Pseudo-Noise Circuit for Higher Resolution Low-Noise Signals
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Solution Overview
Problem
Analog to digital converters face a resolution limit due to quantization noise, where digital codes become indistinguishable, and traditional methods like averaging require a minimum noise level, which can be absent or cumbersome to introduce.
Innovation Solution
A repeating deterministic signal is generated using a circuit with switchable voltage sources and resistors, added to the analog input signal before conversion, allowing for increased resolution through oversampling and averaging, with the signal being filtered out to avoid disrupting the digital output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital averaging is used to raise the resolution of an A/D converter, then the noise free code resolution is improved, but a minimum level of noise must be present in the signal which may not be available
Solution Approach 1:
A pseudo-noise signal is introduced as an intermediary element to provide the necessary variability for digital averaging. This signal is generated by a dedicated circuit that creates a deterministic yet unpredictable sequence, serving as a mediator between the lack of natural noise and the requirement for noise-based resolution improvement.
Solution Approach 2:
The invention changes the parameter of signal variability by introducing a pseudo-noise signal with specific statistical properties. The signal has a known probability distribution that mimics random noise, allowing the system to achieve the required variability without relying on natural noise sources.
2Measurement precision
If white noise is introduced to enable averaging, then the resolution can be improved, but significant additional circuitry is required
Solution Approach 1:
The patent uses a simple resistor network with switchable connections to generate the pseudo-noise signal, replacing complex white noise generation circuitry. This approach uses inexpensive, simple components (resistors and switches) to create the necessary signal variability without requiring significant additional circuitry.
Solution Approach 2:
The invention replaces physical noise sources or complex electronic noise generators with a deterministic digital-controlled system. By using digitally controlled switches to select resistor combinations, the system substitutes mechanical/physical noise generation with a controlled electronic switching mechanism.
3Measurement precision
If a pseudo-noise signal is added to the input signal, then the distribution of digital outputs is improved for averaging, but the signal may introduce additional noise that disrupts the digital output
Solution Approach 1:
The pseudo-noise signal is generated with a periodic structure that allows it to be completely filtered out after serving its purpose. The signal repeats a known sequence, enabling the system to apply digital filtering that eliminates the added noise while retaining the benefits of improved output distribution during the averaging process.
Solution Approach 2:
The invention converts the potentially harmful effect of added noise into a beneficial tool for improving resolution. The pseudo-noise signal intentionally adds variability to the input, which initially appears as noise but is actually used to spread out digital output codes, improving the effectiveness of averaging and resolution.
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 method enhances the resolution of analog to digital converters by introducing a pseudo-noise signal that is filtered out, improving the distribution of digital outputs and reducing noise, thus overcoming the limitations of existing noise-free code resolution.
Implementation Method 1
The analog repeatable deterministic signal is generated by a circuit including a plurality of resistors making up at least two circuit branches
Implementation Method 2
The common connection point is connected to a ground connection through a current summing resistor
Data Source
AI summary
Systems and methods for improving resolution of low-noise signals in an analog-to-digital conversion circuit. A simple, low cost pseudo-noise generating circuit is disclosed that, when connected to the signal conditioning circuitry of A/D conversion circuit, adds pseudo-noise to an analog input voltage signal. Additional pseudo-noise is beneficial for improving the resolution of analog-to-digital conversion when oversampling and summing or averaging are used in post-conversion processing operations. The circuit is composed of a plurality of resistors configured in at least two parallel branches. An individually switchable voltage source output is connected to each branch. A resulting analog voltage can be measured at a common termination point for the branches, depending on the combination of switchable voltage source output turned on, and the branch to which the voltage output is applied. By varying the combination of switchable voltage source outputs turned on over time, a known analog pseudo-noise signal is developed.