A 22-34 GHz CMOS Neutralization-Based Direct-Conversion I/Q UpConverter for 1024-QAM Modulation

This paper proposes a 22–34 GHz neutralizationbased direct-conversion in-phase and quadrature (I/Q) upconverter implemented using a 90-nm CMOS process. The upconverter comprises two active double-sideband (DSB) modulators. An innovative topology, incorporating a neutralization cascode amplifier and two reflection-type modulators, is employed within the DSB modulators to enhance output power, gain, bandwidth, circuit stability, and modulation quality for some advanced high-order digital modulation schemes. The proposed I/Q up-converter achieves a conversion gain of 13 dB, an image-rejection ratio better than -40 dBc, a modulation bandwidth exceeding 4 GHz, a compact size of 1 mm², and a maximum output power exceeding 15 dBm. The measured rootmean-square (rms) error vector magnitudes (EVMs) remain within 2% at a transmitted output power of 4 dBm for various quadrature amplitude modulation (QAM) schemes, supporting complex modulations up to 1024-QAM.