Hybrid LWIR Microantenna Bolometer Thermal Isolation
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Solution Overview
Problem
Bolometers face sensitivity limitations due to thermal loading, which attenuates temperature changes from scene temperature, leading to reduced noise equivalent delta temperature (NEDT) and increased noise from readout circuits, particularly in long-wave infrared (LWIR) and Terahertz imaging applications.
Innovation Solution
The implementation of a hybrid long-wave infrared (LWIR) microantenna design with pie-shaped arms in a double bow-tie configuration and circumferential teeth, combined with active thermal isolation using electro-thermal feedback, minimizes thermal loading and enhances radiation absorption, thereby improving sensitivity and field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bolometer design with suspended legs is used, then mechanical support and thermal isolation are achieved, but thermal loading from legs degrades sensitivity
Solution Approach 1:
The patent extracts the thermal isolation function from the mechanical support legs by introducing a separate superinsulator structure. The sensing element is suspended by legs that provide mechanical support, while the superinsulator (comprising multiple reflective surfaces and vacuum gaps) provides thermal isolation, separating these two functions to eliminate the thermal loading problem.
Solution Approach 2:
The superinsulator acts as an intermediary thermal barrier between the sensing element and the heat bath. It comprises multiple reflective surfaces and vacuum gaps that mediate thermal transfer, providing extremely low thermal conductance while maintaining mechanical stability.
2Measurement precision
If leg length is increased to reduce thermal conductance, then thermal isolation improves, but mechanical support becomes insufficient
Solution Approach 1:
The thermal isolation path is segmented into multiple stages: the sensing element is first isolated from the immediate surroundings by the superinsulator structure, which itself is thermally isolated from the heat bath by additional insulating layers and vacuum gaps. This segmentation allows achieving low thermal conductance without requiring excessively long leg lengths.
3Measurement precision
If readout circuit noise is considered, then sensitivity degradation increases, but thermal loading attenuation makes signals smaller
Solution Approach 1:
The patent applies preliminary anti-action by preemptively reducing thermal loading effects through the superinsulator structure before the signal reaches the readout circuit. By minimizing thermal conductance G2, the temperature change signal δTD is maximized, ensuring it remains above the readout circuit noise floor without requiring complex noise filtering.
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 significantly enhances the sensitivity and field of view of bolometers, achieving better than a 10× improvement over conventional methods by effectively reducing thermal loading and increasing radiation absorption across the LWIR spectrum.
Implementation Method 1
the pie-shaped arms are sensitive to electric fields and absorb radiation
Implementation Method 2
active thermal isolation using electro-thermal feedback
Implementation Method 3
Certain sensors utilize bolometers. Bolometers detect changes in a scene's actual or radiometric temperature
Implementation Method 4
each leg 12 incorporates an insulator for mechanical support and a thin conductor for electrical readout
Data Source
AI summary
Hybrid microantennas and improved sensor structures incorporating hybrid microantenna embodiments are described herein. A hybrid long-wave infrared (LWIR) microantenna includes four inner pie-shaped arms in which the four inner pie-shaped arms are in a double bow-tie configuration and a plurality of outer pie-shaped arms in which a subset of the outer pie-shaped arms is connected to the four inner pie-shaped arms and the pie-shaped arms are sensitive to electric fields and absorb radiation.