Complementary DCDL Stages for Delay Linearity and Spur Reduction
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Solution Overview
Problem
Digitally controlled delay lines (DCDLs) suffer from non-linearity, leading to fractional spurious signals that are challenging to filter out, primarily due to the dependence of delay on the slope of voltage at the delay elements, which affects the performance in applications like digital phase-locked loop (PLL)-based frequency synthesizers.
Innovation Solution
The implementation of a multi-stage DCDL design with complementary switching, cross-stage aggregation, and segmentation of delay elements, controlled by a digital control signal, to address systematic integral nonlinearity and mismatch between stages, enhancing linearity and reducing fractional spurs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional DCDL design is used, then the device complexity is low, but the linearity is poor leading to fractional spurs
Solution Approach 1:
The delay line is divided into multiple delay stages, each with segmented delay elements that can be independently controlled. This segmentation allows for finer granularity in delay control and enables complementary switching operations across stages to cancel non-linearities, thereby improving linearity without requiring a complete redesign of the entire delay line.
Solution Approach 2:
The patent employs complementary switching control that dynamically changes the operating parameters of delay elements across different stages. By controlling corresponding delay elements in different stages to switch in complementary patterns (one on while the other is off), the system adjusts effective delay parameters to cancel systematic integral nonlinearity, improving linearity while managing complexity through controlled parameter variation.
2Manufacturing precision
If complementary control is applied to reduce non-linearity, then the linearity improves, but the control complexity increases
Solution Approach 1:
The control mechanism is segmented to match the physical segmentation of delay stages. Each stage has its own set of control signals that follow complementary patterns, allowing the complex control function to be decomposed into simpler, repeatable units. This modular control approach improves linearity through systematic complementary switching while keeping control complexity manageable through repetition of standardized control patterns.
Solution Approach 2:
The patent implements control mechanisms that monitor and adjust delay element states based on complementary switching patterns. By establishing feedback loops that ensure corresponding elements in different stages maintain complementary states, the system achieves improved linearity while automating the complex control requirements, reducing the burden on external control systems.
3Object-generated harmful factors
If multiple delay stages with complementary control are used, then fractional spurs are reduced, but the device area increases
Solution Approach 1:
The delay line is segmented into multiple stages with corresponding delay elements that can be selectively activated. By segmenting the delay function across stages and using complementary switching, the patent reduces fractional spurs through cancellation of non-linear effects while optimizing area usage through selective activation of delay elements rather than requiring all elements to be simultaneously active.
Solution Approach 2:
The patent combines multiple delay stages into a unified delay line structure where corresponding delay elements across stages work together through complementary control. This merging approach allows the system to achieve spur reduction through coordinated operation of multiple stages while sharing common control infrastructure and resource elements, thereby mitigating the area increase that would result from completely independent stages.
Data Source
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AI summary
A digitally controlled delay device includes a plurality of first delay stages connected in series between a first input port and a first output port, and a plurality of second delay stages connected in series between a second input port and a second output port. Each first delay stage of the plurality of first delay stages includes a plurality of first delay elements and each second delay stage of the plurality of second delay stages includes a corresponding plurality of second delay elements. A controller performs complementary control based on a digital control signal by controlling one or more of the plurality of first delay elements to be in a first control state and controlling a corresponding one or more of the plurality of second delay elements to be in a second control state, opposite the first control state.