SFQ Pulse Multiplier Circuit for RSFQ-CMOS Voltage Interfacing
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Solution Overview
Problem
RSFQ electronics face challenges in interfacing with CMOS technologies due to low operating voltages, making frequency and voltage conversion difficult, and requiring room temperature amplification for small voltage measurements.
Innovation Solution
A circuit and method that split an SFQ pulse into separate paths, store one path in a latch, and recombine them with a delay Josephson transmission line to achieve even or odd frequency multiplication, allowing for variable multiplication factors by tuning the delay via current bias.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SFQ pulses are used for digital signal processing in RSFQ circuits, then information can be transferred in the form of quantized voltage pulses, but the operating voltage remains very low (microvolt level) making interfacing with CMOS technologies difficult
Solution Approach 1:
The patent introduces an SFQ pulse multiplier circuit as an intermediary device that converts low-voltage SFQ pulses into higher voltage pulses suitable for CMOS interfacing. The multiplier uses Josephson junctions and transmission lines to generate multiple output pulses from a single input pulse, with each pulse having sufficient voltage amplitude for CMOS compatibility, thus mediating between the RSFQ and CMOS domains
Solution Approach 2:
The patent changes the voltage parameter of the SFQ pulses through frequency multiplication. By generating N output pulses from one input pulse and controlling the timing and amplitude, the system effectively transforms the voltage level parameter to make it compatible with CMOS operating ranges while preserving the digital signal integrity
2Ease of operation
If frequency multiplication is implemented to overcome low operating voltages, then voltage conversion capability is improved, but device complexity increases due to additional circuit components
Solution Approach 1:
The patent divides the frequency multiplication function into separate modular components: SFQ pulse sources, multiplier circuits with Josephson junctions, transmission lines for pulse propagation, and latch circuits for timing control. This segmentation allows each component to be optimized independently and facilitates integration with CMOS technologies while managing overall system complexity
3Ease of operation
If pulse splitting and latching is used to achieve frequency multiplication, then voltage amplitude can be increased for CMOS compatibility, but the circuit requires precise timing control which increases design difficulty
Solution Approach 1:
The patent employs periodic action through clock signals that control the latching and release of SFQ pulses at precise intervals. The clocked D-latch circuits operate at predetermined frequencies to ensure that multiplied pulses are generated with correct timing and phase relationships, automating the timing control function and reducing design complexity
Solution Approach 2:
The patent implements feedback mechanisms where the output pulses are monitored and used to control subsequent pulse generation and latching operations. This feedback ensures precise timing synchronization and allows the circuit to self-correct timing deviations, simplifying the overall timing control design
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
Enables efficient frequency and voltage multiplication, facilitating the integration of RSFQ with CMOS technologies and overcoming the limitations of low operating voltages in RSFQ electronics.
Implementation Method 1
A single flux quantum (SFQ) pulse is created when the superconducting phase difference across a resistively shunted Josephson Junction (JJ) evolves by 2π. From the second Josephson relation, SFQ pulses have a quantized area ∫V(t)dt=Φ0
Implementation Method 2
An RSFQ circuit is a digital electronic circuit that uses superconducting devices, such as JJs, to process digital signals. In RSFQ logic, information is stored in the form of magnetic flux quanta and transferred in the form of SFQ voltage pulses
Data Source
AI summary
A method of generating an output signal based on a single flux quantum (SFQ) pulse includes receiving the SFQ pulse and splitting it into a first path and a second path. The split SFQ pulse of the second path is stored in a latch. A second splitting of the split SFQ pulse of the first path is provided to provide a first output signal and a second output signal of the first path. The second output signal is delayed by a delay Josephson transmission line (JTL). An output of the delay JTL is provided as a clock input to the latch. The first output of the first path is recombined with an output of the latch to provide an output signal.