Flight Recorder Clock Synchronization for Multi-ADC Audio Sampling
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Solution Overview
Problem
Conventional flight recorders face synchronization issues due to variance in sampling frequencies among multiple Analog-to-Digital Converters (ADCs), leading to desynchronization of audio streams over time, which complicates meeting industry standards for recording accuracy and consumes significant processing bandwidth.
Innovation Solution
Implementing a master clock signal across the flight recorder system to synchronize the sampling frequencies of ADCs, eliminating the need for internal clocks to generate sampling rate signals, ensuring synchronized sampling and transmission of audio data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple ADCs with internal clocks are used to sample audio signals, then the system can capture multiple audio streams simultaneously, but the sampling frequencies vary among ADCs causing desynchronization of audio streams over time
Solution Approach 1:
The patent introduces a master clock signal as an intermediary device that mediates between the ADCs and the audio signal sources. This master clock receives a reference frequency and distributes synchronized clock signals to multiple ADCs, ensuring they all sample at the same rate. The master clock acts as a central coordinator that eliminates frequency variance among ADCs while preserving their simultaneous audio capture capability.
Solution Approach 2:
The master clock signal serves multiple functions: it provides the sampling clock for all ADCs, generates time stamp information for data packets, and coordinates the operation of multiple audio recording channels. By making the clocking mechanism universal across all ADCs, the system achieves synchronized sampling without requiring separate clock management for each converter.
2Ease of operation
If each ADC uses its own internal clock to generate sampling rate signals, then the ADCs can operate independently, but significant processing bandwidth is consumed to handle desynchronized audio streams
Solution Approach 1:
The master clock serves as a central intermediary that eliminates the need for each ADC to independently manage its own clocking. By providing a unified clock source, the system reduces the computational burden of synchronizing multiple independent clock sources, thereby lowering processing bandwidth consumption while maintaining operational simplicity.
Solution Approach 2:
The system uses time stamp information generated by the master clock to provide feedback on the sampling rate. This feedback mechanism allows the receiving device to verify that audio streams are being captured at the correct synchronized rate, enabling error detection and correction without requiring complex real-time processing of desynchronized streams.
3Adaptability or versatility
If ADCs sample at different frequencies, then each ADC can be configured independently, but real-time sample rate conversions are required which complicates CVFDR configuration
Solution Approach 1:
The master clock provides a universal sampling frequency to all ADCs, making the sampling rate consistent across the system. This universality eliminates the need for complex real-time sample rate conversions while still allowing each ADC to be configured for its specific audio source, thus reducing device complexity without sacrificing adaptability.
Solution Approach 2:
The synchronization of sampling frequencies is performed in advance by the master clock before the audio data is captured and processed. By pre-establishing the sampling rate for all ADCs, the system avoids the need for complex real-time sample rate conversions during audio stream processing, thereby simplifying CVFDR configuration and reducing processing complexity.
4Measurement precision
If a master clock signal is implemented to synchronize ADC sampling frequencies, then audio stream synchronization is achieved, but an additional clock distribution system is required
Solution Approach 1:
The patent combines the clock distribution function with the existing audio recording system by integrating the master clock into the CVFDR architecture. Rather than adding a completely separate clock distribution system, the master clock is merged with the audio data acquisition and time stamping functions, thereby achieving synchronization while minimizing additional system complexity.
Data Source
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AI summary
A flight recorder system (200) of an aircraft includes a cockpit voice and flight data recorder (250) communicatively coupled, via a data communication network (220), to a first flight recorder module (FRM). The first FRM (211) includes a first sensor (231) configured to generate a first analog signal (235), a first controller (241), and a first analog to digital converter (221) configured to sample the first analog signal (235) based on a respective clock signal and to convert the first analog signal (235) to a first digital data signal (226). The first FRM (211) is configured to receive a master clock signal (265) via the data communication network (220), and to sample the first analog signal (235) based on the master clock signal (265).