Decision Feedback Equalizer Timing for Delayed Multipath Removal
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Solution Overview
Problem
Existing decision feedback equalizers (DFEs) require excessive circuitry or logic to account for strong delayed reflections due to their inability to effectively manage multipath interference caused by substantial delays in signal transmission, particularly in environments like ocean or flat ground transmissions.
Innovation Solution
A multipath delay calculator determines the delay between the line-of-sight and reflected signals, allowing decisions to be delayed until the reflection is received, thereby reducing the number of taps required for equalization and minimizing circuitry needed, by limiting the correction window to the time of reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a decision feedback equalizer uses a long correction window to account for strong delayed reflections, then the ability to remove multipath interference is improved, but the number of registers and multipliers required increases excessively
Solution Approach 1:
The patent segments the correction process by dividing the correction window into multiple segments, each handled by a separate DFE instance. Each DFE processes a specific time segment of the received signal, allowing the system to handle long delays without requiring a single excessively long correction window that would demand excessive circuitry.
Solution Approach 2:
The patent implements dynamic adjustment of the correction window length based on the detected multipath delay. The delay estimator measures the actual delay between LOS and reflected signals, and this measurement dynamically configures the DFE's correction window to match the actual interference duration, avoiding the need for a fixed overly-long window.
2Device complexity
If a forward filter with limited span is used, then the device complexity is reduced, but the ability to account for reflected signals with substantial delay is lost
Solution Approach 1:
The patent employs feedback mechanisms where the delay estimator continuously monitors the received signal to detect reflected signal arrivals. This feedback information is used to dynamically adjust the DFE's correction window and tap coefficients, enabling the system to adapt to varying delay conditions without requiring a permanently oversized filter.
Solution Approach 2:
The system performs preliminary delay estimation and detection before applying the full DFE correction. By first identifying the presence and characteristics of reflected signals through delay estimation, the system can prepare appropriate correction parameters in advance, allowing a compact filter to handle delayed reflections effectively when they occur.
Data Source
AI summary
The present invention is directed to a decision feedback equalizer that implements a multipath delay calculator to determine the delay between a line-of-sight component of a received data signal and a reflection of the line-of-sight component. The determined delay is used to control when decisions are used within the decision feedback equalizer so that the appropriate decisions are delayed until the reflection is received. In this way, the reflection can be substantially removed from the data signal using decisions that were generated when the line-of-sight component was received. Because the correction window is limited to the time when the reflection is received, the number of taps required to perform equalization is greatly reduced resulting in a decision feedback equalizer with less circuitry or logic.