Calibration of transmitter IQ imbalance with 1-bit feedback

Modern wireless technology calls for high throughput, which can be achieved by large spectral bandwidth, and/or high-order modulation. The in-phase and quadrature (IQ) imbalance is an important factor degrading the transmitter error vector magnitude (EVM), thus limiting the transmitter performance. In order to compensate for the IQ imbalance, a feedback path at the transmitter output is needed to estimate the mismatch. The analog-to-digital converter (ADC) in the feedback path can be power hungry when the signal bandwidth is large. In this paper, we propose a digital IQ imbalance estimator and compensator with 1-bit quantization in the feedback path. We show that the proposed algorithm is valid in terms of estimation convergence and accuracy. Numerical results show that the proposed algorithm achieves comparable estimation accuracy as that using the conventional least mean squares (LMS) method at a much lower cost.