Gigahertz DAC Synchronization Using Shared Clock and Timing Trigger
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Solution Overview
Problem
Modern radar systems face challenges in synchronizing gigahertz digital-to-analog converters (DACs) for real-time radio frequency (RF) scene generation, particularly in hardware-in-the-loop applications, due to misalignment and uncertainty in signal timing across multiple DACs located on separate circuit cards, which affects the fidelity and accuracy of radar returns.
Innovation Solution
A method and apparatus that utilize a radar timing card to receive radar timing information and a synchronous clock signal, generating a timing trigger to align the simultaneous transmissions of DAC channels, ensuring deterministic timing and reducing uncertainty by using a synchronous clock signal to synchronize the DACs across multiple cards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple DACs are located on separate circuit cards with internal PLLs, then each DAC can operate independently, but timing alignment and synchronization between DACs becomes uncertain due to PLL stability variances
Solution Approach 1:
The patent merges the clock sources of multiple independent DACs by distributing a single external synchronous clock signal to all DAC channels. This eliminates the need for each DAC to generate its own clock via internal PLL, thereby synchronizing all DAC outputs to the same time reference and removing timing uncertainties caused by PLL stability variances.
2Speed
If DAC high-speed serial input is in a different clock domain than output sample clock, then DAC can process high-speed data, but deterministic timing becomes difficult to achieve
Solution Approach 1:
The patent introduces an intermediary clock synchronization mechanism that mediates between the high-speed serial input clock domain and the output sample clock domain. By using a distributed synchronous clock signal as a common reference, the system establishes deterministic timing relationships across different clock domains, enabling both high-speed processing and precise timing control.
3Adaptability or versatility
If external trigger is on yet another clock domain, then system can accommodate multiple clock domains, but trigger to analog data output timing uncertainty increases
Solution Approach 1:
The patent creates an equipotential timing reference by distributing the external synchronous clock signal to all DAC channels and the trigger mechanism. This ensures that all components operate from the same time reference potential, eliminating timing uncertainties that would otherwise arise from operating in different clock domains. The trigger to analog data output timing becomes deterministic because all elements are synchronized to the same clock edge.
Data Source
AI summary
A method includes receiving, at a radar timing card, radar timing information and a synchronous clock signal. The method also includes generating, using the radar timing card, a timing trigger to indicate a time of transmission for radar return information. The method further includes receiving, at each of multiple digital-to-analog converter (DAC) channels of one or more DAC cards, the synchronous clock signal and the timing trigger. In addition, the method includes simultaneously transmitting, from each of the DAC channels, a dedicated portion of the radar return information based on the time of transmission indicated by the timing trigger. The synchronous clock signal is used to align the simultaneous transmissions of the DAC channels on the one or more DAC cards.