A Low Phase Error Vector Modulator Using TEST Tunable I/Q Generator for mmWave Communication

This letter presents a low phase error with a high gain vector modulator in a 28 nm CMOS process. It consists of an input balun network (IBN), a tunable I/Q generator, a variable gain amplifier (VGA), and an output balun network (OBN). The proposed I/Q generator uses two transformer-based couplers and a varactor. Through the control of the varactor, the I/Q generator can optimize the operation frequency at which the phase difference of each quadrature signal is 90°. To implement the proposed I/Q generator, the IBN uses a cascode topology to isolate between the IBN and I/Q generator. The VGA utilizes the Gilbert cell design to control the amplitude of the quadrature signal. The proposed vector modulator achieved a phase shift of 22.5° and had an average root-mean-square (rms) phase error of 2.89° and an rms gain error of 1.57 dB at the 31–36 GHz band. The maximum average gain was −3.48 dB at 33 GHz, and the power consumption was 28.8 mW from a 1.8 V supply. The proposed vector modulator achieved a high gain with a low rms phase error based on the tunable I/Q generator in the
$Ka$
-band.