Ring Oscillator Phase Error Calibration via Current Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for calibrating phase errors between in-phase and quadrature-phase signals in wireless communication systems face challenges such as calibration difficulties, long processing times, and limitations in applicability to systems without Poly Phase Filters, particularly in direct conversion receivers.
Innovation Solution
A phase-error calibration method for PLL circuits and ring oscillators that controls tail and shift current amounts using voltage-current converters and differential amplifiers to adjust delay and shift times, ensuring a 90° phase difference between in-phase and quadrature-phase signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the butterfly structure is used to calibrate phase error in digital signal region, then the phase error can be calibrated using power and correlation measurements, but the processing time becomes long when phase error is large and calibration becomes difficult
Solution Approach 1:
The patent replaces complex digital signal processing operations with a simpler analog/physical measurement approach. Instead of performing lengthy digital correlation measurements and power calculations to determine phase error, the invention uses a measurement signal passed through the receiver to directly observe signal characteristics, significantly reducing processing time while maintaining calibration precision.
2Ease of operation
If direct conversion receiver (DCR) is used to separate signals at high frequencies, then signal separation is achieved, but I/Q phase mismatch effect becomes more severe
Solution Approach 1:
The patent implements a feedback-based calibration approach where a measurement signal is passed through the receiver and the resulting phase error is measured and corrected. This feedback mechanism compensates for the I/Q phase mismatch inherent in direct conversion receivers, maintaining signal separation capability while improving phase accuracy through iterative correction.
Data Source
AI summary
A ring oscillator and a phase error calibration method are provided. The ring oscillator may include a first voltage-current converter for controlling and outputting an amount of tail current Itail according to a magnitude of a first control voltage applied in feedback in a PLL circuit; a second voltage-current converter for controlling and outputting an amount of shift current according to a magnitude of a second control voltage applied from a system phase error detector; and differential amplifiers for controlling, for output signals, a delay time of signals based on the applied tail current amount and a shift time of the signals based on the shift current amount. Thus, a phase relation between in-phase and quadrature-phase signals outputted from the ring oscillator may be controlled.