An Q ‐factor calibration method for compensation of the I/Q signal imbalances in 5–6 GHz beamforming receiver

This article presents 5–6 GHz beamforming receiver with Q ‐factor calibrated vector modulator to reduce phase error and amplitude mismatch. Q ‐factor of vector modulator IQ network has to be 0.95–1.05 in 5–6 GHz to get under ±3° phase error. Proposed Q ‐factor calibration circuit selects the best capacitance and resistance for proper Q ‐factor in desired frequency range. Beamforming receiver prototype, which is implemented in 0.13‐μm CMOS, has 0.98–1.03 Q ‐factor in 5–6 GHz. The prototype has improved performance than without calibration: its rms phase error is maximum 1.5° (4.5° improved), and amplitude mismatch is maximum 0.47 dB (0.73‐dB improved). In addition, noise figure is 3.8–4.6 dB at 5–6 GHz.