SQUID Array Receiver Flux Bias Control for Mobile Detection
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Solution Overview
Problem
Superconducting quantum interference devices (SQUIDs) face accuracy issues when operated in motion due to changing orientation relative to the Earth's magnetic field, which affects the magnitude and direction of measured magnetic fields, especially when exposed to incident radio frequency signals.
Innovation Solution
A receiver comprising an SQUID array, a bias-tee, and a logic circuit that generates a transfer function of magnetic flux from combined Earth's and oscillating magnetic fields, with a memory store to store voltage and flux bias values for maximum sensitivity, and a logic circuit to adjust flux bias in real-time to maintain sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an SQUID array is operated in motion with changing orientation relative to the Earth's magnetic field, then the receiver can detect electromagnetic signals while moving, but the measurement precision deteriorates due to variations in the magnitude and direction of the measured magnetic field
Solution Approach 1:
The system continuously monitors the DC signal component and uses feedback control to adjust the flux bias in real-time. The logic circuit compares the measured DC signal against stored reference values and dynamically adjusts the flux bias to maintain optimal operating conditions, thereby compensating for orientation changes and maintaining measurement accuracy during motion
Solution Approach 2:
The system changes the flux bias parameter dynamically to compensate for variations in the Earth's magnetic field caused by changing orientation. By adjusting the flux bias based on the measured DC signal, the system maintains the AC coupling capacitor within its linear operating range despite external field variations, thus preserving measurement precision during mobility
2Measurement precision
If the flux bias is adjusted in real-time to compensate for Earth's magnetic field variations, then the sensitivity is maintained, but the device complexity increases due to the need for memory store and logic circuit
Solution Approach 1:
The system performs preliminary action by pre-storing multiple flux bias values and their corresponding DC signal reference values in the memory store before operation. This allows the logic circuit to quickly lookup and select appropriate compensation values without requiring complex real-time calculations, thereby maintaining sensitivity while minimizing the added device complexity
Solution Approach 2:
The AC coupling capacitor serves as an intermediary element that automatically blocks the DC component of the Earth's magnetic field while allowing AC signal components to pass. This passive intermediary simplifies the overall system by providing automatic DC rejection, reducing the complexity of active compensation circuits needed to maintain sensitivity
3Productivity
If the AC coupling capacitor is used to block DC signal and pass AC signal, then the RF signal detection is enabled, but the distortion of oscillating magnetic fields occurs when the capacitor is driven outside its linear range
Solution Approach 1:
The system uses feedback control to monitor the DC signal level and adjust the flux bias accordingly to keep the AC coupling capacitor operating within its linear range. This feedback mechanism prevents the capacitor from being driven into non-linear operation, thereby maintaining signal fidelity while enabling RF signal detection capability
Solution Approach 2:
The system takes preliminary anti-action by proactively adjusting the flux bias to prevent the AC coupling capacitor from entering non-linear operation. By anticipating and counteracting conditions that would drive the capacitor outside its linear range, the system maintains signal fidelity before distortion can occur, enabling reliable RF detection
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
The solution enables accurate detection of electromagnetic signals by compensating for changes in the Earth's magnetic field, maintaining sensitivity and preventing distortion of oscillating magnetic fields, thus allowing concurrent detection of multiple radio-frequency signals.
Implementation Method 1
Superconducting quantum interference devices (SQUIDs)... An array of SQUIDs may be used to detect magnetic fields
Implementation Method 2
Each SQUID 15 in the SQUID array 12 may include a loop of superconducting material... three Josephson junctions
Implementation Method 3
The bias-tee 14 is configured to divide the SQUID array output into a direct current (DC) signal and an RF signal
Implementation Method 4
The logic circuit 18 is configured to find a voltage value in the memory store 16 that most closely matches the DC signal, and to apply to the SQUID array a flux bias corresponding to the most closely matched voltage value
Data Source
AI summary
A receiver for detecting at least one electromagnetic signal while the receiver is moving relative to the Earth's magnetic field, the receiver comprising: an SQUID array for generating an output that is a transfer function of SQUID array magnetic flux that is supplied from a combination of an oscillating magnetic field of the at least one electromagnetic signal, the Earth's magnetic field, and a bias magnetic field; a bias-tee configured to divide the SQUID array output into a DC signal and an RF signal; a memory store configured to store a plurality of voltage and flux bias values, wherein each voltage value has a corresponding flux bias value that results in maximum SQUID array sensitivity; and a logic circuit configured to find a voltage value in the memory store that most closely matches the DC signal, and to apply to the SQUID array a flux bias corresponding to the most closely matched voltage value.