A K-Band Variable Gain Low-Noise Amplifier with Low Phase Variation in 65-nm CMOS

Based on the inductive source degenerated cascode amplifier gain cell, a two-stage variable gain K-band low noise amplifier (LNA) with low phase variation is designed for wireless communication. With the transformer-based matching network and current steering variable gain techniques, theoretical analysis and simulations are undertaken, revealing and verifying the way to achieve wide bandwidth and low phase variation. Over 19-to-23 GHz, test results show that the proposed circuit achieves 4.5-to-18.5-dB power gain, 4.1-dB noise figure (NF) and 14.5 dBm OIP3. For a low phase variation, less than 1.8° RMS phase error can be achieved with 6dB gain variation from 19 to 23 GHz. Implemented in a 65-nm CMOS process, the LNA consumes 67.2 mW from a 1.2 V supply and its chip size (including all pads) is 0.8×0.48 mm
²
.