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A millimeter-wave direct-conversion radio-frequency (RF) transmitter requires precise in-/quadrature-phase (I/Q) mismatch calibration and dc offset cancellation to minimize image rejection ratio (IRR) and LO feedthrough (LOFT) for ensuring satisfactory output spectral purity. We present a 28-GHz CMOS RF transmitter with an improved calibration technique for fifth generation (5G) wireless communication applications. The RF transmitter comprises a baseband amplifier, quadrature up-conversion mixer, power amplifier driver, and quadrature LO generator. The I/Q amplitude mismatch is calibrated by tuning the gate biases of the switching stage FETs of the mixer, the I/Q phase mismatch is calibrated by tuning the varactor capacitances at the LC load of LO buffer, and the dc offset is cancelled by tuning the body voltages of the differential-pair FETs at the baseband amplifier. The proposed technique provides precise calibration accuracy by employing mV-resolution tuning voltage generation via 6-bit voltage digital-to-analog converters. It also covers wide calibration range while minimizing the impact on the circuit’s bias point and dissipated current during calibration. Implemented in a 65 nm CMOS process, the RF transmitter integrated circuit shows output-referred 1 dB compression power of +6.5 dBm, saturated output power of +12.6 dBm, and an operating band of 27.5–29.3 GHz while demonstrating satisfactory performances of −55.9 dBc of IRR and −36.8 dBc of LOFT.

This paper presents the integration of an inductor by complementary metal-oxide-semiconductor (CMOS) compatible processes for integrated smart microsensor systems that have been developed to monitor the motion and vital signs of humans in various environments. Integration of radio frequency transmitter (RF) technology with complementary metal-oxide-semiconductor/micro electro mechanical systems (CMOS/MEMS) microsensors is required to realize the wireless smart microsensors system. The essential RF components such as a voltage controlled RF-CMOS oscillator (VCO), spiral inductors for an LC resonator and an integrated antenna have been fabricated and evaluated experimentally. The fabricated RF transmitter and integrated antenna were packaged with subminiature series A (SMA) connectors, respectively. For the impedance (50 Ω) matching, a bonding wire type inductor was developed. In this paper, the design and fabrication of the bonding wire inductor for impedance matching is described. Integrated techniques for the RF transmitter by CMOS compatible processes have been successfully developed. After matching by inserting the bonding wire inductor between the on-chip integrated antenna and the VCO output, the measured emission power at distance of 5 m from RF transmitter was -37 dBm (0.2 μW).