Linearized SQUID Arrays for RF Magnetic Field Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
SQUID amplifiers for magnetic field detection face limitations in dynamic range and linearity, particularly at radio frequencies, due to their nonlinear transfer functions, which result in undesired harmonics and intermodulation products, and require negative feedback to improve performance, but this is challenging given their low gain values.
Innovation Solution
The approach involves combining nonlinear Josephson junctions and SQUIDs to cancel mutual nonlinearities, achieving a piecewise linear triangle wave transfer function through harmonic superposition, differential magnetic frustrated arrays, and modified SQUID cells with a shunting Josephson junction, resulting in a linearized voltage response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional SQUID amplifiers are used for magnetic field detection, then sensitivity is achieved, but dynamic range and linearity are limited due to nonlinear transfer functions
Solution Approach 1:
The invention divides a single SQUID into multiple identical SQUIDs arranged in an array. Each SQUID contributes to the overall output, and through proper phasing and combining of their outputs, the system achieves both high sensitivity and improved linearity. The segmentation allows the nonlinear responses of individual SQUIDs to be combined in a way that extends the overall linear dynamic range.
Solution Approach 2:
Multiple SQUID outputs are merged through a combining network that properly phases and sums their signals. This merging process allows the system to achieve higher sensitivity through signal summation while maintaining linearity through constructive interference of the periodic responses from each SQUID element.
2Ease of operation
If negative feedback is implemented to improve linearity, then dynamic range increases, but maximum operation frequency is limited to a few tens of megahertz
Solution Approach 1:
The invention introduces a combining network as an intermediary that processes the outputs of multiple SQUIDs. This intermediary performs the linearity enhancement function through coherent summation rather than through feedback mechanisms, thereby avoiding the bandwidth limitations imposed by feedback loops while still achieving improved linearity and dynamic range.
3Measurement precision
If arrays of SQUIDs are used to increase dynamic range, then sensitivity improves, but device complexity increases
Solution Approach 1:
The invention designs the SQUID array and combining network to serve multiple functions simultaneously: signal summation for sensitivity enhancement, phase coherence for linearity improvement, and dynamic range extension. This multi-functionality reduces the need for separate components for each function, thereby managing complexity despite the increased number of elements.
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 solution significantly increases the dynamic range and linearity of the detector output, reducing noise and interference, and allows for enhanced performance in radio-frequency magnetic field detection without the need for negative feedback, achieving a power gain of at least 6 dB and a linear response over a range of magnetic fields.
Implementation Method 1
A Josephson junction is known to act as a lossless nonlinear inductance below its critical current Ic, and also exhibits nonlinear resistance above Ic
Implementation Method 2
magnetic flux Φ is inductively coupled into the loop through a coupling inductor L
Implementation Method 3
The Superconducting Quantum Interference Device, or SQUID, is well known as a sensitive detector of weak magnetic fields
Implementation Method 4
Superconducting Quantum Interference Device
Data Source
AI summary
A superconducting quantum interference devices (SQUID) comprises a superconducting inductive loop with at least two Josephson junction, whereby a magnetic flux coupled into the inductive loop produces a modulated response up through radio frequencies. Series and parallel arrays of SQUIDs can increase the dynamic range, output, and linearity, while maintaining bandwidth. Several approaches to achieving a linear triangle-wave transfer function are presented, including harmonic superposition of SQUID cells, differential serial arrays with magnetic frustration, and a novel bi-SQUID cell comprised of a nonlinear Josephson inductance shunting the linear coupling inductance. Total harmonic distortion of less than −120 dB can be achieved in optimum cases.