A Ka-band CMOS low-phase-variation variable gain amplifier with good matching capacity

This paper presents a Ka-band variable gain amplifier (VGA) fabricated in a standard 0.18-μm CMOS process using the proposed cascade amplifier method to achieve both low phase variation and good output matching capacity in a variable gain mode. The proposed VGA achieves 14.2 dB gain control range with a phase variation of 8.9°. The input and output reflection coefficients versus the gain control bias at 26.6 GHz are below -19 dB and -10 dB, respectively. A 14.2 dB gain control range with low phase variation and good input and output matching is achieved. The chip size is 0.65 mm2 with pads.