Method to Improve the Linearity of Active Commutating Mixers Using Dynamic Current Injection

Dynamic and static current injection methods to improve the linearity of a current commutating mixer are investigated and a double-balanced CMOS mixer (DBM) providing high linearity is presented in this paper. A cross-coupled pair is used in the IF stage of the mixer to dynamically inject current into the mixer to provide a high linearity. The proposed DBM was fabricated using a standard 130-nm CMOS process and was tested on-wafer. The double-balanced mixer delivers 10-dB conversion gain, 9.5-dBm third-order intercept point, and input P1dB of -2.4 dBm. RF bandwidth of the proposed mixer is 6 GHz, covering 0.5-6.5 GHz with an IF bandwidth of 300 MHz. RF to IF and LO to IF isolation are also better than 59 dB in the whole frequency band. The circuit uses an area of 0.015 mm
²
excluding bonding pads and draws 4.5 mW from a 1.2 V supply.