Phase Rotator Current Steering for Thermometer-Code Linearity
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Solution Overview
Problem
Phase rotators in clock and data recovery circuits face significant non-linearity issues due to the relationship between thermometer-coded signals and output signal phases, leading to inefficiencies in phase compensation.
Innovation Solution
A phase rotator design with current bias circuitry that adjusts individual current biases to minimize non-linearity by using a configuration of n-channel field effect transistors and resistive ladders to steer currents between nodes, ensuring a controlled and reduced non-linear relationship between thermometer code values and output signal phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional current bias circuitry is used in phase rotators, then the circuit structure is simple, but significant non-linearity occurs between thermometer-coded signals and output signal phases
Solution Approach 1:
The patent applies local quality by assigning different current bias values to different segments of the phase rotator circuit. Specifically, different current biases are applied to different groups of current steering circuits corresponding to different phase ranges, allowing each local region to be optimized for its specific phase output requirements, thereby reducing overall non-linearity while maintaining manageable circuit complexity
Solution Approach 2:
The patent changes the parameter of current bias values from uniform to non-uniform distribution. By adjusting the current bias parameters across different segments of the phase rotator, the patent optimizes the linearity between thermometer-coded inputs and phase outputs, transforming the system from a simple but non-linear structure to a more complex but linearized structure
2Manufacturing precision
If uniform current biases are used in phase rotator, then the circuit design is straightforward, but non-linearity between thermometer code values and phase output cannot be minimized
Solution Approach 1:
Different current bias values are assigned to different local regions (phase segments) of the phase rotator. Each local region has optimized current biases tailored to its specific phase range, improving overall phase linearity while keeping the design methodology systematic and manageable
Solution Approach 2:
The phase rotator is divided into multiple segments or groups, each handling a specific phase range. This segmentation allows independent optimization of current biases for each segment, making the complex design task more manageable while achieving superior overall linearity performance
3Measurement precision
If non-linearity reduction techniques are applied to phase rotator, then phase compensation accuracy improves, but the current bias circuitry becomes more complex
Solution Approach 1:
The patent optimizes phase compensation accuracy by carefully adjusting current bias parameters across different segments. This parameter optimization reduces non-linearity effects, improving measurement precision of phase compensation while accepting increased circuit complexity as a necessary trade-off
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 solution effectively reduces phase rotator non-linearity, improving the accuracy and efficiency of phase compensation in clock and data recovery circuits by optimizing the current bias profile, thereby enhancing the performance of clock signal generation.
Implementation Method 1
resistive ladders to steer currents between nodes
Implementation Method 2
n-channel field effect transistors to steer currents between nodes
Data Source
AI summary
A phase rotator receives control signals and thermometer coded signals that specifies the phase of an output signal. The phase rotator may be used, for example, by a clock and data recovery (CDR) circuit to continually rotate the phase of a clock to compensate for phase/frequency mismatches between received data and the clock. The control signals determine the phase quadrant (i.e., 0°-90°, 90°-180°, etc.) of the output signal. The thermometer coded signals determine the phase of the output signal within a quadrant by steering a set of bias currents between two or more nodes. The set of bias currents are selected to reduce the non-linearity between the thermometer coded value and the phase of the output signal.