PLL-Based CDR Circuit for Phase Alignment Stability
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Solution Overview
Problem
Traditional clock and data recovery (CDR) circuits in optical fiber communication suffer from phase errors due to manufacturing variations, leading to increased bit error rates (BER).
Innovation Solution
A CDR circuit design incorporating a phase locked loop (PLL) circuit, delay devices, an edge detector, a gated voltage-controlled oscillator, a phase detector, and amplifiers to improve phase alignment and generate accurate recovery clock and data signals, with specific configurations involving reference voltages and control signals to adjust delay times and amplify phase signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional CDR circuit is used, then the circuit structure is simple, but phase errors occur due to manufacturing variations leading to increased bit error rate
Solution Approach 1:
The CDR circuit is segmented into multiple functional modules: delay devices for timing adjustment, edge detector for signal processing, gated voltage-controlled oscillator for clock generation, phase detector for phase comparison, and amplifier for signal enhancement. Each module performs a specific function to collectively solve the phase error problem while maintaining manageable complexity through modular design.
Solution Approach 2:
The circuit employs dynamic elements including delay devices with adjustable delay times, a gated voltage-controlled oscillator that dynamically generates clock signals based on phase detection feedback, and an amplifier that dynamically adjusts phase signal strength. These dynamic components enable the circuit to adapt to manufacturing variations and maintain low bit error rates.
2Manufacturing precision
If delay devices and amplifiers are added to improve phase alignment, then phase alignment improves, but device complexity increases
Solution Approach 1:
Delay devices are positioned in the signal path to preliminarily adjust timing of data and clock signals before they reach the phase detector. This preliminary timing adjustment compensates for manufacturing variations in signal propagation delays, establishing proper phase alignment before final comparison and reducing the need for extensive post-correction circuitry.
Solution Approach 2:
The phase detector continuously monitors the phase difference between data and clock signals and generates a phase signal that feeds back to the gated voltage-controlled oscillator and delay devices. The amplifier enhances this phase signal to improve the precision of feedback control. This closed-loop feedback mechanism automatically corrects phase alignment errors without requiring complex manual calibration circuits.
Data Source
AI summary
The invention provides a clock and data recovery (CDR) circuit, including: a phase locked loop (PLL) circuit, providing a reference voltage; a first delay device, delaying an input data according to a control signal so as to generate a first delay signal; an edge detector, generating an edge signal according to the first delay signal and the input data; a second delay device, delaying the edge signal so as to generate a second delay signal; a first gated voltage-controlled oscillator, generating an output recovery clock according to the second delay signal and the reference voltage; a phase detector, detecting a phase difference between the first delay signal and the output recovery clock so as to generate a phase signal and a output recovery data; and an amplifier, amplifying the phase signal by a factor so as to generate the control signal.