K-band CMOS low-noise amplifier with 180° phase shift function using cascode structure

In this study, a K-band CMOS low-noise amplifier (LNA) with a 180 & DEG; phase shift function is presented to reduce the chip area of the beamforming system. The proposed LNA is composed of three stages, and the last stage is designed with a differential cascode structure for 180 & DEG; phase shift function. The 180 & DEG; phase shift function was implemented by dividing one cascode transistor into two transistors. As a result, it is possible to equip the 180 & DEG; phase shift function without an additional chip area. The LNA was designed with a 65-nm CMOS process to verify the feasibility of the proposed technique. The core size was 0.66 x 0.41 mm(2). The measured phase difference between 0 & DEG; and 180 & DEG; phase shift modes was approximately 178 & DEG; in the operating frequency of 22.0 GHz. The measured noise figure and gain were 3.8 and 12.7 dB, respectively.