Multi-PLL Phase Alignment Using Closed-Loop Feedback Calibration
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Solution Overview
Problem
In wireless communication devices, maintaining accurate phase alignment among multiple Phased Locked Loops (PLLs) is challenging due to impairments like charge-pump output impedance mismatch and temperature drift, especially in high-frequency millimeter-wave systems, which affects beamforming performance and requires frequent recalibration that disrupts ongoing transmission.
Innovation Solution
A system and method for phase alignment of multiple PLLs using a closed-loop calibration process where phase detectors compare feedback signals from adjacent PLLs to generate adjustment signals, allowing for phase adjustments in the charge-pump, time-to-digital converter, or frequency divider, reducing accumulation errors and enabling infrequent recalibration based on temperature drift or elapsed time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate PLLs are used for each transceiver to reduce noise correlation and improve SNR, then signal-to-noise ratio improves, but phase alignment between PLLs becomes difficult to maintain
Solution Approach 1:
The patent implements a feedback mechanism where phase detectors continuously monitor the phase relationship between feedback signals from separate PLLs and generate adjustment signals to correct phase deviations. This closed-loop feedback system maintains phase alignment while allowing the PLLs to operate independently for noise reduction.
Solution Approach 2:
The patent introduces phase detectors and adjustment signals as intermediary components between separate PLLs. These intermediaries measure and correct phase relationships without requiring direct coupling between PLLs, enabling phase alignment while maintaining independence for noise reduction.
2Measurement precision
If frequent recalibration is performed to maintain phase alignment accuracy, then phase alignment precision improves, but transmission interruption occurs
Solution Approach 1:
The patent implements a self-calibrating system where the phase detectors and adjustment signals automatically maintain phase alignment between PLLs during normal operation. The system performs self-correction without external intervention or transmission interruption, as the calibration occurs in the feedback path that is already present for PLL operation.
3Measurement precision
If antenna calibration algorithm is rerun to compensate for temperature drift, then phase alignment accuracy improves, but time and resources are consumed and transmission is interrupted
Solution Approach 1:
The patent maintains continuous phase alignment through the closed-loop feedback system with phase detectors and adjustment signals. Unlike periodic recalibration that interrupts transmission, this system continuously adjusts phase relationships in real-time, eliminating calibration interruptions and associated time losses while maintaining accuracy despite temperature drift.
Data Source
AI summary
A system and method for phase alignment of multiple PLLs are disclosed. The system comprises a plurality N of PLLs (PLL_1 . . . PLL_N) and a plurality N of phase detectors (DET_1 . . . DET_N). The plurality N of phase detectors and the plurality N of PLLs are connected in a loop such that an i-th phase detector (DET_i) is configured to receive an i-th feedback signal (FB_i) generated from the i-th PLL and an (i+1)-th feedback signal (FB_i+1) generated from the (i+1)-th PLL, and the N-th phase detector (DET_N) is configured to receive the first feedback signal (FB_1) generated from the first PLL and the N-th feedback signal (FB_N) generated from the N-th PLL. The an i-th phase detector (DET_i) is configured to generate an i-th adjustment signal indicating an i-th phase difference between the i-th and (i+1)-th feedback signals for adjusting a phase of the i-th or (i+1)-th PLL, wherein i=1, 2, 3, . . . N−1. The N-th phase detector (DET_N) is configured to generate a N-th adjustment signal indicating a N-th phase difference between the first and N-th feedback signals.