Passive Transmission Line Receiver With Interferometer Pulse Isolation
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Solution Overview
Problem
Josephson junction-based digital logic circuits face challenges with spurious pulses generated by passive transmission lines, leading to data errors due to specific clock frequencies and line lengths, which complicates circuit design and increases potential for mis-triggering and data errors.
Innovation Solution
The implementation of a receiver circuit that isolates the SFQ-generating junction from the passive transmission line, using a three-junction interferometer configuration for amplification and isolation, and terminating the PTL with an inductor instead of a Josephson junction, as well as matching the resistance at the driver end to eliminate counter-propagating pulses, thereby reducing data errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional receiver uses a Josephson junction to receive signals from the passive transmission line, then the receiver can detect SFQ pulses, but spurious pulses are generated that propagate back along the transmission line causing data errors
Solution Approach 1:
An inductor is introduced as an intermediary component between the passive transmission line and the receiver Josephson junction. This inductor acts as a mediator that allows the receiver junction to detect SFQ pulses from the transmission line while preventing the generation and propagation of spurious pulses back along the line, thus resolving the contradiction between signal detection capability and spurious pulse generation
Solution Approach 2:
The receiver circuit is segmented into distinct functional components: the transmission line interface (with inductor termination), the biasing circuitry, and the Josephson junction detector. This segmentation isolates the SFQ-generating junction from the passive transmission line, allowing the junction to perform its detection function without directly generating harmful spurious pulses on the line
2Device complexity
If the passive transmission line length and clock frequency are not carefully matched, then circuit design is simplified, but data errors occur due to spurious pulse interference
Solution Approach 1:
The problematic interaction between transmission line length and clock frequency is extracted and eliminated by using inductor termination at the receiver end. This removes the dependency relationship between line length and clock frequency, allowing independent optimization of these parameters without causing spurious pulse interference, thus simplifying design while maintaining reliability
Solution Approach 2:
The termination condition at the receiver end is changed from a direct Josephson junction connection to an inductor-based termination. This parameter change in the boundary condition of the transmission line fundamentally alters the pulse propagation characteristics, eliminating the clock frequency and line length dependent data errors while maintaining signal integrity
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 reduces the impact of spurious pulses, resulting in improved reception and performance by minimizing the generation and propagation of interference signals, leading to more reliable data transmission and reduced errors in digital logic circuits.
Implementation Method 1
Josephson junctions are typically a circuit element comprising two superconducting electrodes separated, for example, by a thin insulating tunnel barrier, which can support a current that flows indefinitely without any voltage applied
Implementation Method 2
A three-junction interferometer configuration is used for amplification and isolation
Implementation Method 3
The PTL terminates into an inductor instead of a Josephson junction
Implementation Method 4
a PTL is terminated with a matching resistance at the driver end
Data Source
AI summary
The present disclosure relates to improved electronic structures for propagating logic states between superconducting digital logic gates using a three-junction interferometer in a receiver circuit to reduce reflecting signals that otherwise result in distortions in the signals being transmitted between the gates. Other improved electronic structures comprise passive transmission lines (PTLs) with transmission line matching circuitry that has previously been avoided. The matching circuitry minimizes generation and propagation of spurious pulses emitted by Josephson junctions used in the digital logic gates.