Digital Delay Locked Loop for Accurate Quarter-Cycle Clocking
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Solution Overview
Problem
Conventional digital clock and data recovery circuits face challenges in generating accurate quarter-cycle clock signals, which affects their accuracy and bit error rates.
Innovation Solution
A digital delay locked loop apparatus comprising a delay circuit and a control circuit that generates intermediate signals and output signals with quarter-cycle intervals through a combination of coarse and fine delay adjustment stages, interpolation, and a finite state machine, allowing for accurate quarter-cycle interval generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional digital clock and data recovery circuits are used, then basic clock signal generation is achieved, but the accuracy of quarter-cycle clock signals is insufficient leading to higher bit error rates
Solution Approach 1:
The delay adjustment is segmented into two distinct stages: a coarse delay adjustment stage that provides large-step delay calibration, and a fine delay adjustment stage that provides small-step precision calibration. This segmentation allows the system to efficiently achieve both broad coverage and high precision in quarter-cycle clock signal generation, resolving the contradiction between basic functionality and signal accuracy.
Solution Approach 2:
An interpolation circuit is introduced as an intermediary between the coarse and fine delay adjustment stages. This interpolation circuit generates intermediate delay values by combining outputs from the coarse adjustment stage, enabling smooth transitions and precise control of the quarter-cycle clock signals. The intermediary interpolation mechanism bridges the gap between coarse positioning and fine tuning, achieving high accuracy without requiring an overly complex direct control system.
2Device complexity
If a simple delay adjustment mechanism is used, then device complexity is reduced, but the ability to generate accurate quarter-cycle signals is compromised
Solution Approach 1:
The delay adjustment mechanism is divided into modular coarse and fine adjustment stages, each with dedicated functionality. The coarse stage handles large-range adjustments with simple control logic, while the fine stage handles precision adjustments. This modular segmentation maintains relative simplicity within each stage while achieving high overall precision through their coordinated operation.
Solution Approach 2:
The system dynamically switches between coarse and fine adjustment modes based on the locking status detected by the lock detector. During initial acquisition, the coarse adjustment is active for rapid positioning. Once locked, the system transitions to fine adjustment mode for precision tuning. This dynamic operation allows the system to achieve high precision without maintaining complex control mechanisms continuously, thereby managing device complexity effectively.
Data Source
AI summary
An apparatus comprising a delay circuit and a control circuit. The delay circuit may be configured to generate a plurality of intermediate signals in response to (i) a clock signal and (ii) an adjustment signal. The control circuit may be configured to generate the adjustment signal and a plurality of output signals having a quarter-cycle interval in response to (i) the plurality of intermediate signals and (ii) the clock signal.