Iterative Calibration Method for Integrated Tunable mmW Vector-Sum Phase Shifter

An iterative calibration method of 5G mmW vector- sum phase shifter (VSPS) is presented in this paper. The phase and amplitude imbalances of I and Q branches can be tuned. The phase is adjusted with a tunable polyphase filter (PPF) by changing its resonance frequency. The VSPS is equipped with differential amplifiers on each branch which are used to compensate for the amplitude imbalance. The iterative calibration method uses information collected during the measurements and adjusts VSPS parameters towards the optimal operation point. The error vector magnitude (EVM) of VSPS phase constellation decreases fast along the iterations, and the calibration process can be finished with a fraction of the measurement time compared with exhaustive search. Results show that the method can reach an RMS amplitude error of 0.11 dB and phase error of 0.6 degrees on selected frequency points.