Transition-Edge Bolometer Circuit with Dual Feedback
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Solution Overview
Problem
Transition-edge bolometers face instability due to positive thermal feedback when using constant current biasing, leading to increased noise and complexity in electronics, making it difficult to measure with room-temperature equipment without increasing noise, especially in multipoint imaging applications.
Innovation Solution
Implementing a circuit that combines both positive and negative feedback by using current biasing with positive thermal feedback and voltage biasing with negative thermal feedback, maximizing dynamic resistance while maintaining system stability, using an operation amplifier and feedback resistor to achieve high impedance and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If constant current biasing with positive thermal feedback is used, then dynamic impedance increases, but system stability deteriorates
Solution Approach 1:
The patent applies feedback by using a SQUID amplifier to detect changes in bolometer resistance and adjust the bias current accordingly. The SQUID measures the resistance change caused by radiation absorption, and the feedback circuit modifies the bias current to maintain stable operation while preserving the positive thermal feedback effect that increases dynamic impedance.
2Stability of the object's composition
If voltage biasing with negative thermal feedback is used, then system stability improves, but dynamic impedance decreases
Solution Approach 1:
The patent employs negative feedback through the SQUID amplifier circuit that detects resistance changes and adjusts bias current to counteract thermal fluctuations. This feedback mechanism stabilizes the system while the positive thermal feedback from current biasing maintains high dynamic impedance, resolving the contradiction between stability and impedance.
3Object-generated harmful factors
If SQUID is used as pre-amplifier, then noise is reduced, but sensitivity to mechanical vibration increases
Solution Approach 1:
The patent introduces a magnetic shield as an intermediary between the SQUID amplifier and the external environment. The magnetic shield blocks mechanical vibrations and electromagnetic interference from reaching the sensitive SQUID, while allowing the SQUID to continue functioning as a low-noise pre-amplifier for the bolometer signal.
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 stabilizes the system, reduces noise, and allows for efficient multipoint imaging by maximizing dynamic resistance, enabling the use of low-noise amplifiers at room temperature and minimizing thermal noise, suitable for millimeter and infrared radiation detection.
Implementation Method 1
If the temperature of a superconducting thermally insulated object is very close to the transition point, its resistance will change very greatly due to even a small amount of additional energy caused, for example, by radiation or a mass particle.
Implementation Method 2
Because the change in the resistance as a function of temperature is very great, the current following through it heats the components and gives rise to thermal feedback.
Data Source
AI summary
The invention relates to a circuit for transition-edge bolometers, which comprises a resistor element (1) arranged to operate in the transition-edge zone, and an amplifier (5) connected to the resistor element (1). According to the invention, in connection with the amplifier (5) means are arranged for implementing positive (4, 5) and negative (5, 2) feedbacks in the resistance measurement.