ROIC Input Cell Circuit for TDI and Stray Light Blanking
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Solution Overview
Problem
Radiation sensors, such as those used in infrared detection, face limitations in sensitivity due to read noise, which restricts the range and optical power of detection systems, and existing technologies struggle to effectively integrate multiple returns within a single frame time to enhance signal-to-noise ratio.
Innovation Solution
The implementation of a time delay integration (TDI) technique at the readout integrated circuit (ROIC) level, utilizing switches to control integration and biasing of sensor signals, allowing for multiple integration intervals within a frame time and blanking intervals to exclude stray light, thereby increasing sensitivity and range without increasing system size, weight, or power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signal current is integrated during frame interval to improve sensitivity, then signal-to-noise ratio improves, but read noise limitations restrict detection range and optical power
Solution Approach 1:
The patent applies preliminary action by performing multiple integration intervals before the final readout within a single frame time. The TDI circuit accumulates signal charge from multiple returns during predetermined integration periods, then transfers the accumulated charge to a storage node for readout. This preliminary accumulation of signal charge before readout enhances the signal-to-noise ratio, overcoming read noise limitations and extending detection range without requiring increased optical power.
2Measurement precision
If multiple integration intervals are implemented within frame time to enhance sensitivity, then signal averaging improves detection capability, but circuit complexity increases
Solution Approach 1:
The patent merges multiple integration operations into a single TDI circuit unit cell that can perform multiple integration intervals sequentially within one frame time. The circuit combines the transducer, integration capacitor, transfer switch, and storage node into an integrated unit that accumulates charge from multiple returns and transfers it to a shared storage node. This merging approach achieves signal averaging and enhanced sensitivity without proportionally increasing circuit complexity, as multiple integrations share common circuit elements.
Solution Approach 2:
The patent implements dynamic control of the TDI circuit through timed switching operations. The transfer switch is controlled to connect the integration capacitor to the storage node at specific intervals during the frame time, enabling multiple integration periods followed by readout. This dynamic switching allows the circuit to adapt its operation mode (integrating vs. transferring) based on the detection phase, achieving flexible multi-interval integration without requiring separate static circuit paths for each integration interval.
3Measurement precision
If integration capacitor is connected continuously to transducer to maximize signal collection, then signal current is fully integrated, but stray light and unwanted signals are also integrated
Solution Approach 1:
The patent applies preliminary anti-action by using the transfer switch to disconnect the integration capacitor from the transducer at predetermined times during the frame interval. The switch opens the connection between the transducer and integration capacitor during periods when stray light or unwanted signals are expected, preventing these harmful signals from being integrated. Meanwhile, the integration capacitor remains connected during valid signal returns, allowing selective integration of desired signals while rejecting stray light interference through timed disconnection.
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 enhances the sensitivity and range of radiation detection systems by averaging multiple returns within a frame time, improving the signal-to-noise ratio and allowing for flexible timing schemes that can seamlessly vary from frame to frame, effectively overcoming read noise limitations.
Implementation Method 1
a transducer array, and an amplifier having an inverting input and an output. The inverting input is for receiving input from an element of the transducer array... an integration capacitor operatively connected between the inverting input and the output, and for integrating signal from the element of the transducer array
Data Source
AI summary
Techniques are disclosed that provide time delay integration (TDI) in detection signal processing (such as a signal generated by an IR sensor). The techniques can be implemented, for example, to provide blanking and/or TDI functionality at the readout integrated circuit (ROIC) level for active focal plane array (FPA) elements or other transducer elements. In one example embodiment, an integrator circuit is configured with one or more switches for allowing integration of multiple input signal events such that reset of the integration is controlled independently and can be reset equal to or less often than the number of single events, thereby allowing one or more detected events to be integrated together within a frame interval.