TX-RX PLL Phase Synchronization for Accurate RTT Calibration
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Solution Overview
Problem
The phase delay variation between transmitter and receiver phase-locked loops in wireless communication systems introduces errors in processing delay calibration, particularly during transient conditions, affecting the accuracy of round-trip time measurements used for positioning procedures.
Innovation Solution
A phase correction signal is generated using the output signals of the transmitter and receiver phase-locked loops, which are then adjusted to maintain a consistent phase relationship, ensuring accurate synchronization and reducing phase delay variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase correction signal is applied to synchronize TX and RX PLLs, then measurement precision of RTT is improved, but device complexity increases due to additional synchronization circuitry
Solution Approach 1:
The patent introduces a phase correction signal as an intermediary element that mediates between the TX and RX PLLs. This signal is generated by detecting the phase relationship between waveforms from both PLLs and applying correction to synchronize them, thereby improving RTT measurement precision without requiring complete system redesign
Solution Approach 2:
The patent implements a feedback mechanism where the phase relationship between TX and RX waveforms is continuously monitored and used to generate corrective phase adjustment signals. This closed-loop feedback system automatically maintains synchronization between PLLs, improving measurement precision while managing complexity through automated control
2Productivity
If processing delay calibration is performed during transient conditions, then calibration speed is improved, but measurement precision deteriorates due to phase delay variation
Solution Approach 1:
The patent applies preliminary phase correction actions during transient conditions by continuously generating and applying phase correction signals before RTT measurements are taken. This preliminary synchronization ensures that even during fast transient calibration, the phase relationship between TX and RX PLLs remains controlled, preventing the deterioration of calibration precision
Solution Approach 2:
The patent maintains continuous phase correction action throughout the calibration process, including during transient conditions. Rather than interrupting correction during transient states, the system continuously monitors and adjusts phase relationships, ensuring uninterrupted useful action that maintains precision while enabling fast calibration
Data Source
AI summary
Phase variations between a transmitter (TX) waveform and a receiver (RX) waveform produced by a TX Phase-Locked-Loop (PLL) and a RX PLL, respectively, is a source of error in processing delay calibration used, e.g., in Round Trip Time (RTT) estimation. While a TX waveform and a RX waveform have a constant phase delay while in steady state conditions, during transient times, e.g., at start up or reset, the phase delay may vary by as much as ±180°, which at baseband frequencies of 50 MHz, introduces a random delay variations of as much as ±10 nsec, which is undesirable for fine position estimation using RTT. The phase delay variation between the TX waveform and RX waveform may be reduced or eliminated using a phase correction signal generated using the output signals of the TX PLL and RX PLL.