A Nonrecursive Digital Calibration Technique for Joint Elimination of Transmitter and Receiver I/Q Imbalances With Minimized Add-On Hardware

A nonrecursive digital calibration technique, namely, local oscillator (LO) switching, is proposed for jointly eliminating transmitter (TX) and receiver (RX) I/Q imbalances in one combined process. The add-on analog parts are limited to a set of source followers (0.00228 mm²) and metal-oxide-semiconductor (MOS) switches (0.00017 mm² ) for reusing the 90 ^° phase shift property of the reference LO, avoiding the sinusoidal test tone, loop-back detector, high-speed analog-to-digital converter, and 2-D iterative search algorithm, mostly required in the prior art. A 65-nm complementary MOS transceiver, which is codesigned with a field-programmable-gate-array-based coordinate rotation digital computer algorithm, measures a 10-dB improvement in the image rejection ratio of both the TX (27.8 → 37.2 dB) and the RX (31.2 → 42 dB). The required digital circuitry for the algorithm is also assessed and simulated.