Superconducting Mixer Circuit With Flux-Tuned Harmonic Compensation
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Solution Overview
Problem
In radiofrequency signal processing, mixers generate unwanted parasitic lines when handling wide frequency bands, and existing solutions fail to effectively eliminate these lines across the entire frequency range.
Innovation Solution
A mixer design incorporating quantum interference superconducting elements in differential doublets with controlled magnetic flux, along with specific Josephson junction configurations, to minimize parasitic signals by adjusting critical currents and magnetic flux, thereby reducing unwanted frequency lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a mixer is used to process wide frequency bands, then the frequency processing capability is improved, but unwanted parasitic lines appear at frequencies n.fsignal - m.fOL
Solution Approach 1:
The patent applies quantum interference superconducting elements (SQUIDs) that exploit quantum interference effects to selectively enhance the desired mixing product while suppressing parasitic lines. The non-linear transfer function of the SQUID is controlled through magnetic flux to achieve frequency-selective signal processing, converting the harmful parasitic lines into beneficial frequency discrimination.
Solution Approach 2:
The patent changes the operating parameters of the mixer by controlling the magnetic flux applied to the quantum interference superconducting elements. By adjusting the magnetic flux parameter, the transfer function of the mixer can be optimized to minimize parasitic lines at specific frequency combinations while maintaining wide frequency band coverage.
2Reliability
If quantum interference superconducting elements are used to reduce parasitic lines, then the purity of the output signal is improved, but the device complexity increases
Solution Approach 1:
The patent introduces quantum interference superconducting elements as intermediary components between the input signals and output. These SQUID-based elements act as non-linear mediators that perform the mixing function while their quantum interference properties naturally suppress parasitic lines, achieving signal purification without requiring complex post-processing filters.
3Object-generated harmful factors
If the critical current of Josephson junctions is adjusted to minimize parasitic signals, then the suppression of unwanted frequency lines is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent incorporates feedback mechanisms to control and adjust the magnetic flux applied to the quantum interference superconducting elements. This feedback system allows for dynamic optimization of the transfer function to minimize parasitic lines, compensating for manufacturing variations in Josephson junction critical currents without requiring extremely tight manufacturing tolerances.
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 proposed mixer design significantly reduces parasitic signals, achieving low noise and high bandwidth operation while minimizing unwanted frequency lines, thus enhancing signal processing efficiency across wide frequency bands.
Implementation Method 1
two first quantum interference superconducting elements mounted in differential forming a first doublet, and each connected to one of the outputs of the mixer and to one of the two inputs for the second signal
Implementation Method 2
at least one Josephson junction, the critical current of which is equal to the critical current of the first Josephson junction to within 1%
Implementation Method 3
a means of controlling the difference in magnetic flux applied to the two superconducting elements with quantum interference of the first doublet
Implementation Method 4
two first quantum interference superconducting elements mounted in differential forming a first doublet
Data Source
Figure 1~2
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Figure 5~7
AI summary
The mixer (10) comprises an input (12) for injecting a first signal, two inputs (14, 16) for a second signal, the potential difference between the two inputs (14, 16) corresponding to the voltage of the second signal or the potential difference between the two inputs (14, 16) being zero; two outputs (18, 20), the potential difference between the two outputs (18, 20) corresponding to a multiplication of the first signal by the second signal; two first superconducting quantum interference elements (22, 24, 26, 28, 30, 32, 34, 36) mounted differentially forming a first doublet, and each linked to one of the outputs (18, 20) and to one of the two inputs (14, 16) for the second signal; and a means for controlling the difference in magnetic flux applied to the two superconducting quantum interference elements (22, 24, 26, 28, 30, 32, 34, 36) of the first doublet, in which at least one of the superconducting quantum interference elements of the doublets (22, 24, 26, 28, 30, 32, 34, 36, 110) is a superconducting component (110), comprising a first superconducting loop (112), the first superconducting loop (112) comprising a first branch (120) comprising a first Josephson junction (132) and a second branch (122) comprising a first DC superconducting quantum interference device (138), in which the first DC superconducting quantum interference device (138) of the or each component (110) comprises a second Josephson junction (150) and a third Josephson junction (156), a critical current (Ic1, Ic2, Ic3) being defined for each Josephson junction (132, 150, 156), the critical current (Ic1) of the first Josephson junction (132) being greater than the absolute value of the difference between the critical current (Ic3) of the third Josephson junction (156) and the critical current (Ic2) of the second Josephson junction (150) and less than the sum of the critical current (Ic2) of the second Josephson junction (150) and the critical current (Ic3) of the third Josephson junction (156), and in which the or each component (110) comprises means for generating magnetic flux (114, 116, 158, 160, 162 and 164) arranged so as to effectively inject magnetic flux into the first superconducting loop (112) and the first DC superconducting quantum interference device (138).