RF variable gain amplifier with linear control and automatic matching in 28 nm CMOS

A broadband radio frequency (RF) variable gain amplifier (VGA) enhanced with a gain control and automatic input impedance matching is presented in this work. Due to the control loop, the gain is linear-in-magnitude versus the control input. Additionally, the control loop makes the circuit robust towards process and temperature variations of the transistors. The measured low phase variation versus control range of less than 3.5° and the high gain control range of 33 dB make this VGA a suitable building block for multi-antenna front-ends. Furthermore, the circuit shows a large 3 dB bandwidth of 15 GHz and therewith covers multiple ISM frequency bands. The chip is implemented using a Global Foundries (GF) 28nm bulk CMOS process and the active area amounts to 130μm×200 μm. It consumes maximum 4.75mA from a supply of 2.0 V.