Phase Offset Calibration in Multi-Channel Radio-Frequency Transceivers

Abstract

Phase measurements by the quadrature scheme in radio transceivers can be applied to phase-sensitive applications like precision multi-static 3D localization. However, measurements at different channels with individual local oscillators suffer from random phase offsets due to non-repeatable initial phases of phase-locked loops in frequency synthesizers. In this paper, a novel phase calibration method is proposed to cancel out both the random and systematic time-invariant phase offsets at the superheterodyne receiver frontends. Direct phase offset measurements and on-site calibration are made possible by additional hardware connections, achieving simple implementation and accurate differential phase measurements without relying on bandwidth resources. The proposed calibration method generates repeatable phases for each device reboot with standard deviation less than 2 degrees, which translates to 0.9 mm ranging accuracy for 1.8 GHz carrier frequency. This method can also be flexibly extended to accommodate a broad range of practical network scenarios with more channels, various network topologies, and a wider bandwidth.INDEX TERMS Multi-channel radio transceivers, phase calibration, phase locked loops (PLL), radio frequency (RF), software defined radios (SDR).