Switched-Capacitor Amplifier Noise Cancellation Using Auxiliary Sampling
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Solution Overview
Problem
Existing integrated circuits using switched capacitor circuits sample both input signals and thermal noise, which is problematic for high-accuracy and high-resolution applications, as previous techniques only reduce noise power but do not cancel it, leaving residual noise in the system.
Innovation Solution
The implementation of a noise cancellation unit within the integrated circuit, comprising a buffer, auxiliary capacitor, and additional switches, which selectively controls switching devices during clock phases to cancel thermal noise after the input signal has been sampled, using a pair of amplifiers with a negative feedback loop to control gain and eliminate noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If switched capacitor circuits are used for sampling, then discrete time signal processing is enabled, but thermal noise is sampled along with the input signal
Solution Approach 1:
The patent segments the sampling process into two distinct phases: a first sampling phase that captures both the input signal and thermal noise, and a second sampling phase that captures only the thermal noise. By separating these functions into different time periods, the circuit can later subtract the noise component from the signal component to achieve noise cancellation while maintaining signal processing capability.
Solution Approach 2:
The patent performs preliminary noise sampling before the main signal processing. By capturing the thermal noise characteristics in advance during a dedicated noise sampling phase, the system prepares the noise reference that will be used to cancel the noise from the subsequently sampled signal, enabling effective noise removal without compromising signal integrity.
2Object-affected harmful factors
If noise reduction techniques are applied, then noise power is reduced, but actual noise cancellation is not achieved
Solution Approach 1:
The patent implements a feedback mechanism where the thermally noisy voltage sampled during the first phase is fed into a subtraction circuit that removes this noise component from the signal. The system continuously monitors and subtracts the noise reference from the sampled signal, providing active noise cancellation rather than merely reducing noise power, thereby achieving reliable noise removal.
Solution Approach 2:
The patent converts the harmful thermal noise into a useful reference signal. By deliberately sampling the thermal noise during a dedicated phase and using it as a reference for subtraction, the system transforms the noise from a detrimental element into a beneficial tool for achieving noise cancellation. The noise becomes the key to removing itself from the signal path.
3Volume of moving object
If sampling capacitor size is reduced, then circuit integration is improved, but sampled noise power increases
Solution Approach 1:
The patent performs preliminary noise sampling before the main signal sampling, capturing the thermal noise characteristics in advance. This allows the system to know and subtract the noise component regardless of the capacitor size, enabling small capacitor usage without suffering from increased noise power, as the noise is actively removed through the subtraction process.
Solution Approach 2:
The patent uses a feedback-based noise cancellation approach where the noise sampled during the first phase is continuously subtracted from the signal. This active noise removal mechanism compensates for the increased noise power that would otherwise result from smaller capacitor sizes, allowing the circuit to maintain low noise levels even with reduced capacitor dimensions for better integration.
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 approach effectively cancels thermal noise from the sampled signal, improving the accuracy and resolution of integrated circuits by removing noise power, thereby enhancing the overall performance of high-accuracy and high-resolution data converters.
Implementation Method 1
capacitor 10 that is proportional to the input signal, and this charge is held on capacitor 10 when switch 20 is opened
Implementation Method 2
This noise is primarily produced by the switch, such as switch 20 in FIG. 1, in the switched capacitor circuits
Implementation Method 3
the thermal noise power of the sampled noise in a switched capacitor circuit can be expressed by Equation (i)
Data Source
AI summary
An architecture of an integrated circuit allows for the canceling of noise sampled on a capacitor in the integrated circuit, after an input signal has already been sampled. Thermal noise correlated with an arbitrary input signal may be canceled after selectively controlling a plurality of switching devices during a sequence of clock phases. An auxiliary capacitor may be used to store a voltage equal to the thermal noise and enable the cancellation of the thermal noise from the sampled signal in conjunction with a noise cancellation unit.