RSFQ Digital Phase Rotator for Bidirectional Clock Shifting
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Solution Overview
Problem
Existing superconducting digital circuits lack a phase rotator capable of adjusting phase in both positive and negative directions at ultra-fast rates using RSFQ logic.
Innovation Solution
A fast digital phase rotator circuit is developed using superconducting RSFQ elements, including toggle flip-flops, confluence buffers, inverters, and a latch, allowing for phase shifts in both directions with a master clock of 32 GHz and decimated output clock of 2 GHz, optimized for speed and precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a phase generator is designed for precise phase adjustment, then measurement precision is improved, but speed of phase adjustment deteriorates
Solution Approach 1:
The phase adjustment range is segmented into multiple discrete steps, each controlled by individual control lines. This allows precise phase control through digital selection of discrete phase values while maintaining fast switching speeds between segments.
Solution Approach 2:
The circuit uses dynamic control signals that can rapidly switch between different phase states. The control mechanism is designed to respond quickly to input signals, enabling both precise phase positioning and fast adjustment speed through time-varying control.
2Productivity
If a circuit is optimized for ultra-fast operation, then productivity is improved, but manufacturing precision deteriorates
Solution Approach 1:
The circuit operates by changing the state parameters of superconducting elements (Josephson junctions, TFFs) rather than relying on precise analog component values. This digital approach allows ultra-fast operation while being tolerant of fabrication variations in superconducting materials.
Solution Approach 2:
The patent replaces traditional analog phase adjustment mechanisms with superconducting digital logic elements. This substitution enables operation at GHz frequencies while reducing sensitivity to manufacturing tolerances through digital state control.
3Adaptability or versatility
If a phase rotator uses bidirectional control, then adaptability is improved, but device complexity increases
Solution Approach 1:
The circuit uses asymmetric control logic where increment and decrement operations share common infrastructure but have distinct control paths. This allows bidirectional phase control while minimizing redundant circuitry through shared TFF and control line resources.
Solution Approach 2:
The same TFF and control circuit infrastructure is used for both phase increment and decrement operations. The control lines can be configured to perform either function, providing bidirectional control capability without duplicating the entire phase adjustment mechanism.
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 circuit enables precise phase modulation at 2 GHz rates, suitable for digital phase modulation and direct digital synthesis, and can be cascaded for arbitrary precision, applicable in high-speed digital amplifiers and clock synchronization.
Implementation Method 1
superconducting digital circuits
Implementation Method 2
based on Josephson junctions integrated together according to RSFQ Logic
Data Source
AI summary
An important component in digital circuits is a phase rotator, which permits precise time-shifting (or equivalently, phase rotation) of a clock signal within a clock period. A digital phase rotator can access multiple discrete values of phase under digital control. Such a device can have application in digital clock synchronization circuits, and can also be used for a digital phase modulator that encodes a digital signal. A digital phase rotator has been implemented in superconducting integrated circuit technology, using rapid single-flux-quantum logic (RSFQ). This circuit can exhibit positive or negative phase shifts of a multi-phase clock. Arbitrary precision can be obtained by cascading a plurality of phase rotator stages. Such a circuit forms a phase-modulator that is the core of a direct digital synthesizer that can operate at multi-gigahertz radio frequencies.