Programmable Delay Buffer for PPS Phase Alignment
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Solution Overview
Problem
Precision timing in communication and network clock distribution systems faces challenges due to phase shifts in rising and falling edges of GPS pulse per second signals caused by wire routing and impedance mismatches, leading to increased bit-error-rate (BER).
Innovation Solution
An arbitrary delay buffer system with both analog and digital delay mechanisms, utilizing selectable delay stages and resettable ring oscillators, allows for independent and precise delay adjustments to maintain signal duty cycle and period, compensating for phase shifts across different nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If wire routing is used to distribute PPS signals to multiple receivers, then signal distribution is achieved, but phase shifts occur between different nodes due to different routing paths and impedance mismatches
Solution Approach 1:
The delay adjustment is segmented into multiple discrete stages (e.g., 9 stages providing 0-8 ns delay in 1 ns steps). Each stage can be independently enabled or disabled to achieve precise phase alignment without requiring continuous adjustment mechanisms.
Solution Approach 2:
Each receiver node is equipped with its own independent delay adjustment mechanism, allowing local compensation for phase shifts specific to that node's routing path. This enables customized delay adjustment at each location rather than requiring a centralized solution.
2Measurement precision
If delay adjustment mechanisms are added to compensate for phase shifts, then phase alignment is improved, but device complexity increases due to additional components
Solution Approach 1:
The delay adjustment functionality is merged into the existing buffer circuit architecture. The buffer stages serve dual purposes: signal buffering and delay adjustment, eliminating the need for completely separate delay circuitry.
Solution Approach 2:
The delay adjustment is made dynamic and programmable through control logic that can enable or disable specific delay stages based on measured phase shifts. This allows the system to adapt to different routing conditions without requiring fixed, hardwired delay circuits for all possible scenarios.
3Manufacturing precision
If multiple delay stages are implemented to provide precise delay control, then delay precision is improved, but manufacturing complexity increases
Solution Approach 1:
The delay characteristic is made programmable through control signals that enable or disable specific stages. Rather than requiring physically different circuits for different delay values, the same circuit can be reconfigured to provide various delay amounts by changing the activation state of individual stages.
Solution Approach 2:
The total delay range is segmented into discrete stages (e.g., 9 stages of 1 ns each), where each stage is a standardized, repeatable circuit unit. This modular approach simplifies manufacturing compared to creating custom delay circuits for each possible delay value.
Data Source
AI summary
A signal may be arbitrarily delayed in discrete steps by an arbitrary delay buffer having an analog delay and a digital delay. An analog delay may have a number of selectable delay stages (e.g. ring oscillator with VCDL stages). A digital delay may have rising and falling edge detectors, resettable ring oscillators that oscillate in response to rising or falling edges and counters to count oscillations and generate rising and falling edge delay signals when oscillation counts reach rising and falling edge delay counts. A resettable ring oscillator may have a resettable stage (e.g. VCDL) that may be enabled and disabled. Selection of one or both digital and analog delays and respective delay times may be based on one or more characteristics. For example, an analog delay may delay an input signal or a delayed input signal received from the digital delay based on input signal frequency or total delay.