Bus Signal Encoding Circuit for Ethernet Jitter Tolerance
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Solution Overview
Problem
Jitter in signals received from a bus complicates the generation of receive signals in transceivers, particularly when these signals need to meet specific standards in Ethernet-based networks like 10BASE-T1S or 10BASE-T1L.
Innovation Solution
The proposed solution involves an encoder in the transceiver that detects edges in the input signal and generates a pulse sequence with specific ramp and hold portions, ensuring the output signal maintains integrity despite jitter, by sampling the input signal to determine voltage levels and adjust pulse generation accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transceiver directly generates receive signal from bus voltage levels, then the signal processing is simple and fast, but the signal is susceptible to jitter and may not meet standards
Solution Approach 1:
The encoder performs preliminary encoding of the input signal before transmission, preparing the signal in advance with embedded timing information. This preliminary action ensures that even when jitter occurs during transmission, the receiver can still accurately reconstruct the signal by detecting edges and using the pre-encoded pulse structure, thus improving signal integrity without requiring complex real-time correction mechanisms.
Solution Approach 2:
The encoder acts as an intermediary between the data source and the transmission medium. It transforms the original signal into an encoded format with specific pulse structures (ramp portions, hold portions, minimum time periods) that serve as a buffer against jitter. This intermediary transformation allows the signal to withstand transmission imperfections while maintaining reliability.
2Reliability
If the encoder generates pulses with extended minimum time periods to mitigate jitter, then the signal becomes more robust against jitter, but the encoding process takes longer
Solution Approach 1:
The encoder uses periodic pulse structures with defined ramp portions, hold portions, and minimum time periods. This periodic action creates a rhythmic, predictable signal pattern where timing information is embedded in the regular structure. The periodic nature allows the receiver to easily identify valid signal transitions and ignore jitter that falls within the expected time windows, achieving jitter resistance without excessive encoding time.
Solution Approach 2:
The encoder changes the temporal parameters of the signal by introducing minimum time periods and hold portions that extend the duration of critical signal features. This parameter modification makes the signal more tolerant to timing variations (jitter) while the changes are constrained to predetermined minimum values to prevent excessive encoding time.
3Measurement precision
If the encoder samples the input signal multiple times to determine voltage levels, then the accuracy of voltage level detection is improved, but the processing complexity increases
Solution Approach 1:
The encoder performs preliminary sampling of the input signal at specific predetermined times (at the first edge and within the time window) before the actual encoding decision is made. This preliminary sampling captures the voltage level information in advance, allowing the encoder to accurately determine whether to generate a pulse without requiring complex real-time analysis during the encoding process.
Solution Approach 2:
The sampling mechanism serves itself by using the inherent timing structure of the encoded signal. The encoder samples at predetermined times that are naturally defined by the pulse generation process itself (at edges and within time windows), eliminating the need for external synchronization or complex sampling control circuits. The encoding process provides its own sampling timing references.
Data Source
AI summary
An apparatus comprising an encoder is configured to:detect a first edge in the input signal and, in response, provide a pulse generation sequence comprising the encoder being configured to:generate, in the output signal, a first pulse, wherein the first pulse is provided over first and second minimum time periods irrespective of an edge subsequent the first edge being present in the input signal; andobtain a first sample of the input signal; andobtain a second sample at an end of the first pulse; andif the first sample and the second sample are indicative of different voltage levels, generate a second pulse; orif the first and second sample and the same maintain the voltage level in the output signal.