Wideband 120-GHz CMOS I/Q Transmitter With Suppressed IMRR and LOFT for Wireless Short-Range High-Speed 6G IoT Applications

Abstract

In this study, a wideband 120-GHz I/Q transmitter with suppressed image rejection ratio (IMRR) and LO feed through (LOFT) is presented using 40-nm complementary metal oxide semiconductor technology. For the up-conversion mixer, an NMOS/PMOS pair with resistive feedback is used during the transconductance stage to increase the input bandwidth with gain boosting, and a novel switching core without LO-RF coupling is used to suppress the LOFT effect. For the quadrature injection locked tripler, an I/Q calibration circuit is inserted to minimize the I/Q mismatch; accordingly, the measured IMRR is greatly improved. The peak conversion gain of the proposed transmitter was 10.8 dB, and the 3-dB gain bandwidth was 20 GHz. The measured IMD2 and IMD3 were above 40 dBc. Moreover, the IMRR was measured as 43.1 dBc, applying I/Q calibration. The measured LOFT was 33.7 dBc. The data rate of the proposed transmitter was measured up to 20 Gbps and at a distance of 5 cm. Subsequently, the error vector magnitudes were 13.4 dB for QPSK and -19.1 dB for 16-QAM modulation. It is expected that such wireless high-speed communication can be applied to wireless short-range high-speed 6G IoT applications.