A Review of IM2 Distortion and I/Q Imbalance Calibration Techniques in CMOS RF Direct-Conversion Transceivers

CMOS RF direct-conversion transceivers are widely used in modern wireless systems for their high integration and energy efficiency. However, their performance is often limited by impairments such as second-order intermodulation (IM2) distortion and in-phase/quadrature (I/Q) imbalance. This paper reviews calibration techniques developed to address these challenges. It examines the physical origins of IM2 distortion and I/Q imbalance, their impact on system performance, and categorizes calibration approaches as analog, digital, or mixed-signal. The techniques are compared in terms of effectiveness, power consumption, area overhead, and sensitivity to process, voltage, and temperature variations. The paper concludes by discussing recent trends and ongoing challenges, aiming to guide the design of scalable, high-performance CMOS transceivers.