A 23.6-46.5 GHz LNA with 3 dB NF and 24 dB Gain Tuning Range in 28-nm CMOS Technology

This paper presents a three-stage wideband LNA with gain switching technique designed for 5G millimeter-wave applications operating at 23.6-46.5 GHz. By deriving an analytical equation of input impedance and noise matching, a two-pole matching network based on ladder transformer is introduced. The coupling between the transformers can be used to control the two poles of S11 and simultaneously match the source impedance to the optimized noise impedance, achieving broadband input matching and low noise figure (NF). A 24 dB gain tuning range with 6 dB per step has been designed to accommodate different input power level for automatic gain control (AGC). The gain control is implemented with current slicing at the 2nd and 3rd stages, which can keep input/output impedance nearly constant during gain switching. The proposed wideband LNA has been fabricated in 28-nm bulk CMOS process with a chip size of only 0.13 mm2. Measured results show a peak gain of 23 dB within a 3-dB bandwidth from 23.6 to 46.5 GHz, with S11 better than −10 dB over the bandwidth. The measured NF is 2.2 - 3.7 dB with an average of 3 dB. The input 1 dB gain compression point (IP1dB) ranges from −27 to −23.8 dBm throughout the gain bandwidth. Moreover, the measured gain can be switched with value of 21.5/14.9/9.1/2.9/−3 dB, and the corresponding NF and IP1dB are 3.7/4.9/7.9/12.8/14.3 dB and −23.8/−19.5/−14.8/ −13.1/−8.8 dBm at 33 GHz, respectively. This design is suitable for wideband 5G millimeter-wave communication.