Sampling Circuit Noise Suppression via Pixel Voltage Subtraction
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Solution Overview
Problem
Current sampling circuits in imaging applications, such as CT systems, face challenges in reducing pixel sampled noise, which degrades the signal-to-noise ratio (SNR) due to high amplifier bandwidth and parasitic capacitance, leading to increased power consumption and potential non-linearity issues.
Innovation Solution
The implementation of a circuit with a second sampling network that allows for the subtraction of pixel sampled noise voltage from the signal voltage in a subsequent cycle, effectively canceling out the noise and improving SNR without reducing amplifier bandwidth or increasing power spectral density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If amplifier bandwidth is increased to reduce noise, then noise performance is improved, but power consumption increases
Solution Approach 1:
The sampling circuit is divided into two separate sampling networks: a first sampling network that samples the signal voltage, and a second sampling network that samples the pixel sampled noise voltage. This segmentation allows independent processing of signal and noise components, enabling noise reduction without compromising signal quality or increasing power consumption of the amplifier.
Solution Approach 2:
The patent extracts the pixel sampled noise voltage from the total sampled voltage by using the second sampling network to specifically capture and store the noise component. This extracted noise voltage is then subtracted from the signal voltage in subsequent cycles, effectively removing noise without requiring the amplifier to operate at higher bandwidth with increased power consumption.
2Use of energy by moving object
If amplifier bandwidth is reduced to lower power consumption, then power efficiency is improved, but noise performance degrades
Solution Approach 1:
The second sampling network performs preliminary action by sampling and storing the pixel sampled noise voltage in advance (during a first cycle) before the actual signal measurement. This pre-sampled noise voltage is then used for subtraction in subsequent cycles, allowing the amplifier to operate at lower bandwidth while maintaining noise performance through the预先 captured noise characteristics.
3Use of energy by moving object
If amplifier bandwidth is reduced to improve power efficiency, then power consumption is lowered, but linearity may be compromised
Solution Approach 1:
By segmenting the sampling function into two separate networks, the circuit maintains the amplifier's high bandwidth and linearity characteristics while achieving power efficiency through selective noise sampling and subtraction. The first sampling network preserves signal integrity with the amplifier operating at optimal bandwidth, while the second network captures noise independently.
4Device complexity
If pixel sampled noise is not suppressed, then circuit simplicity is maintained, but signal-to-noise ratio degrades
Solution Approach 1:
The second sampling network acts as an intermediary that specifically targets and captures the pixel sampled noise voltage. This intermediary structure enables selective noise measurement and subsequent subtraction without significantly complicating the overall circuit, as the second sampling network reuses existing circuit elements (switches, capacitors) in an additional configuration.
Data Source
AI summary
In described examples, a circuit includes an integrator. The integrator receives an input signal. A first sampling network is coupled to the integrator and generates a signal voltage. A second sampling network is coupled to the integrator and generates a pixel sampled noise voltage. The pixel sampled noise voltage generated in a previous cycle is subtracted from the signal voltage generated in a current cycle to generate a true signal voltage.