De-Emphasizing Cable Equalizer for Longer SDI Links
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Solution Overview
Problem
Existing SDI cable equalizers have limited maximum cable length support and cannot be cascaded due to performing both linear and non-linear operations, making it difficult to extend cable lengths effectively.
Innovation Solution
An extended equalizer circuit is provided, including a linear equalization circuit and a de-emphasizing filter that applies additional linear operations without non-linear operations, allowing for increased cable lengths by compensating for frequency-dependent attenuation in two portions of the transmission medium, with an optional amplifier to recover flat attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a typical cable equalizer performs both linear and non-linear operations, then the equalizer can compensate for frequency-dependent attenuation, but the equalizer cannot be cascaded to support longer cable lengths
Solution Approach 1:
The equalizer function is segmented into two distinct parts: a de-emphasizing filter that handles only linear frequency-dependent attenuation compensation, and a standard equalizer that handles non-linear operations. This segmentation allows the de-emphasizing filter to be cascaded multiple times to extend cable length support, while the standard equalizer remains unchanged for its specific function.
Solution Approach 2:
The linear equalization function is extracted from the standard equalizer and placed into a separate de-emphasizing filter stage. This extraction allows the standard equalizer to be reused without modification, while the de-emphasizing filter can be cascaded to provide extended cable length compensation capability.
2Adaptability or versatility
If multiple cable equalizers are cascaded to support longer cable lengths, then cable length support is extended, but the complexity of the system increases
Solution Approach 1:
By segmenting the equalizer function into a simple de-emphasizing filter and a standard equalizer, the system achieves cable length extension through cascading only the simple filter, avoiding the complexity of cascading multiple complex equalizers while maintaining the necessary functionality.
3Adaptability or versatility
If a de-emphasizing filter is added in series to compensate for additional cable attenuation, then cable length support is extended, but amplitude loss occurs
Solution Approach 1:
An amplifier is introduced as an intermediary component between the de-emphasizing filter and the standard equalizer. This amplifier compensates for the amplitude loss introduced by the de-emphasizing filter, ensuring that the overall signal level is maintained while still providing extended cable length compensation capability.
Data Source
AI summary
In accordance with the teachings described herein, an extended equalizer circuit is provided for equalizing a digital communication signal transmitted over a transmission medium that causes a frequency-dependent attenuation of the digital communication signal. An equalizer may be used that includes a linear equalization circuit and a non-linear equalization circuit, the linear equalization circuit being configured to apply a linear filter to the digital communication signal to compensate for the frequency-dependent attenuation caused by a first portion of the transmission medium, and the non-linear equalization circuit being configured to apply one or more non-linear operations to the digital communication signal. A de-emphasizing equalizer circuit may be coupled in series between the transmission medium and the equalizer and configured to apply an additional linear filter to the digital communication signal in order to compensate for the frequency-dependent attenuation caused by a second portion of the transmission medium.