Decision Feedback Equalizer Asymmetric Delay Element Placement
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Solution Overview
Problem
The convergence accuracy of decision feedback equalizers is compromised when formed into integrated circuits due to increased delay times caused by stray capacitance and the need for additional delay elements, leading to deteriorated waveform equalization performance, especially when channel characteristics change.
Innovation Solution
Asymmetrically disposing delay elements on signal processing and updating paths of weighting devices to ensure that the tap coefficient of the main weighting device is updated more frequently than others, allowing for timely coefficient updates without delaying the waveform equalization operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of taps in the decision feedback equalizer is increased to improve convergence accuracy, then the resolution and equalization performance are improved, but the delay time increases due to increased fan-out of the tap coefficient updating portion and additional delay elements
Solution Approach 1:
The patent segments the tap coefficient updating portion into multiple independent updating portions, each responsible for updating tap coefficients for specific weighting devices. This segmentation reduces the fan-out of each updating portion, thereby reducing the delay time caused by stray capacitance while maintaining the ability to update all tap coefficients necessary for high convergence accuracy
Solution Approach 2:
The patent introduces a hierarchical dimension to the tap coefficient updating structure by dividing the updating portion into a first updating portion for feed forward weighting devices and a second updating portion for feedback weighting devices. This dimensional organization allows parallel updating operations that reduce overall delay time while maintaining accuracy
2Ease of operation
If delay elements are disposed between elements forming the decision feedback equalizer to satisfy timing limitation, then the timing requirement is met, but the convergence accuracy deteriorates because the update timing of tap coefficients is delayed
Solution Approach 1:
The patent implements dynamic tap coefficient updating where the first updating portion updates feed forward weighting device coefficients and the second updating portion updates feedback weighting device coefficients in a coordinated manner. This dynamic updating approach ensures that tap coefficients are updated at appropriate times without excessive delay, maintaining convergence accuracy while satisfying timing requirements
Solution Approach 2:
The patent performs preliminary updates of tap coefficients for feed forward weighting devices before the feedback weighting device coefficients are updated. This preliminary action ensures that the most critical coefficients are available in time for accurate equalization, preventing convergence accuracy deterioration
3Ease of operation
If the number of delay elements is increased to compensate for driving ability and timing, then the timing limitation is satisfied, but the device complexity and number of required delay elements increase
Solution Approach 1:
By segmenting the tap coefficient updating portion into multiple independent updating portions, the patent reduces the fan-out of each portion, thereby reducing the number of delay elements needed in each path while still satisfying timing requirements through parallel operation of the segmented portions
Data Source
AI summary
In a decision feedback equalizer, at least one of weighting devices that has a tap coefficient an absolute value of which is relatively larger than absolute values of tap coefficients of other weighting devices is referred to as a main weighting device, and delay elements are disposed asymmetrically on signal processing paths or updating paths of the tap coefficients of the weighting devices in such a manner that an updating interval of the tap coefficient of the main weighting device is shorter than updating intervals of the tap coefficients of the other weighting devices.