A 3 Gb/s 64-QAM E-band Direct-Conversion Transmitter in 40-nm CMOS

This paper describes a fully integrated E-band transmitter (TX) in 40-nm CMOS. Circuit, layout and calibration techniques are presented to suppress the LO feed-through (LOFT) and I/Q imbalance over both 71-76 and 81-86 GHz bands. A systematic design methodology is proposed for the millimeter-wave poly-phase filter (PPF) to achieve lowest I/Q imbalance with minimum EM simulations. The 40-nm E-band transmitter achieves a measured output power of 12 dBm and TX efficiency of 15% with about 15 GHz bandwidth. Measured from 3 chips, the transmitter features an un-calibrated I/Q imbalance of less than -30 dB from 62.5 to 85.5 GHz. The calibration circuits further reduce the I/Q imbalance by 3-5 dB and ensure the LOFT less than -30 dBc over more than 30 dB output dynamic range. The presented TX achieves 3-Gb/s 64-QAM across the complete E-band.