10BASE-T1S Driver Delay Filtering for FM and DAB Emission Control
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Solution Overview
Problem
In vehicle wired local area networks, stringent emission limits at Frequency Modulated Broadcast Band (FM) and Digital Audio Broadcasting (DAB) frequencies are challenging to meet due to interference from harmonic lobes, which can cause communication difficulties.
Innovation Solution
The implementation of a variable delay driver with multiple stage notch/band stop filtering reduces emissions in specific frequency ranges by shaping the rise and fall of signal levels, using delay elements and sub-drivers to generate a reduced slew rate signal with controlled delays, effectively filtering out predetermined frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If multiple stage notch/band stop filtering is implemented to reduce high frequency emissions, then emission compliance is improved, but device complexity increases
Solution Approach 1:
The filtering function is divided into multiple stages, with each stage targeting specific frequency ranges. The driver circuit includes multiple filtering stages that progressively reduce emissions at different frequency bands, allowing complex emission reduction to be achieved through modular, manageable segments rather than a single complex filter
Solution Approach 2:
The patent implements nested filtering structures where band stop filters and notch filters are combined in a hierarchical manner. The band stop filters address broader frequency ranges while notch filters provide targeted suppression at specific frequencies, creating a nested filtering architecture that efficiently reduces emissions across multiple frequency bands
2Object-affected harmful factors
If delay elements are used to shape signal rise and fall, then emission reduction is improved, but signal transmission delay increases
Solution Approach 1:
The delay elements are configured to provide controlled slew rate reduction only during the rise and fall transitions of the signal, rather than affecting the entire signal duration. By applying delay action selectively to the transient portions of the signal where emissions are generated, the solution achieves emission reduction while minimizing impact on overall signal transmission timing
Solution Approach 2:
The patent adjusts the delay parameters of the delay elements to optimize the balance between emission reduction and signal transmission performance. By carefully tuning the delay values, the system achieves sufficient slew rate control to meet emission requirements while maintaining acceptable signal transmission speed and timing characteristics
Data Source
AI summary
Reducing emissions of predetermined frequencies using delay elements and related apparatuses, methods, and systems are disclosed. An apparatus includes an input terminal to receive a signal, delay elements electrically connected to the input terminal, an output terminal to provide a reduced slew rate signal, and combination circuitry electrically connected to the delay elements and the output terminal. The delay elements provide delayed signals responsive to the received signal. Respective ones of the delayed signals include delayed versions of the received signal. The combination circuitry combines the delayed signals to generate the reduced slew rate signal. Delays associated with the delay elements are chosen to reduce emissions of one or more predetermined frequencies of the reduced slew rate signal as compared to the received signal.