Closed-Loop Signal Delay Estimation for Continuous Timing Alignment
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Solution Overview
Problem
In signal processing applications, especially in closed-loop configurations of wireless transmitters, the varying loop-back delay degrades measurement accuracy if not compensated, and existing methods require pausing normal operation for delay measurement using test signals, which is not feasible for most systems.
Innovation Solution
A signal delay estimator with an adjustable delay element, a delay amount estimator, a leading signal determiner, and a selective inverter, which forms a closed control loop to estimate and compensate for the delay between similar signals without requiring special modulation patterns or pausing normal operation, using separate processing paths for absolute delay and delay direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If test signals are used to measure delay, then measurement accuracy is improved, but normal operation must be paused
Solution Approach 1:
The system performs delay measurement using the actual transmitted signal itself, which is prepared in advance through the feedback path. The feedback signal is already available and contains all necessary characteristics for delay estimation, eliminating the need for separate test signal injection and system pause
Solution Approach 2:
The transmitted signal serves dual purposes: both for normal communication function and for delay measurement. The feedback signal, which is a copy of the transmitted signal delayed by the system, is used directly as the measurement reference, allowing the system to measure its own delay without external test signals
2Device complexity
If loop-back delay is not compensated, then system simplicity is maintained, but measurement accuracy degrades
Solution Approach 1:
A feedback mechanism is introduced where the delayed transmitted signal is continuously monitored and compared with the original transmitted signal. The delay estimator uses this feedback to calculate the actual delay, and this information can then be used to compensate for the delay in real-time, maintaining measurement accuracy without excessive complexity
Solution Approach 2:
A dedicated delay estimator module is introduced as an intermediary component between the transmitter and feedback path. This module specifically handles the delay measurement and compensation function, isolating the complexity from the main transmission system while enabling accurate measurements
Data Source
AI summary
A signal delay estimator includes an adjustable delay element for delaying a first signal to obtain a delayed first signal, a delay amount estimator for estimating a delay amount between the delayed first signal and a second signal that is similar and delayed relative to the first signal, and a leading signal determiner for determining whether the delayed first signal leads the second signal or vice versa, and for generating a corresponding binary signal. A selective inverter is provided for selectively inverting the delay amount depending on the binary signal. The signal delay estimator also includes a feedback element to the adjustable delay element for controlling a delay based on an output of the selective inverter. Another exemplary signal delay estimator includes a closed control loop with an adjustable delay element and separate first and second processing paths for absolute delay amount and delay direction, respectively.