A Ka -Band Switchable LNA With 2.4-dB NF Employing a Varactor-Based Tunable Network

This letter presents a multiband switchable low-noise amplifier (LNA) in the 0.1- $\mu \text{m}$ GaAs pHEMT process. Employing a new varactor-based tunable network as the interstage matching circuit, the operation bands can be tuned consecutively and cover the 5G millimeter-wave frequency bands N257/N260. The proposed tunable structure functions well without sacrificing noise performance or increasing dc consumption and chip area. In the entire operation band from 26.5 to 41 GHz, the LNA achieves a small-signal gain of over 24 dB and a noise figure (NF) of less than 2.9 dB. The measured result shows a small-signal gain of 25.1 dB/27.7 dB and an NF of 2.4 dB/2.8 dB at 28 GHz/39 GHz. The measured input 1-dB compression point (IP _1dB ) is −18.3 dBm/−17 dBm at 28 GHz/39 GHz. The measured input-referred intercept point (IIP ₃ ) is −8.8 dBm/−8.5 dBm at 28 GHz/39 GHz. The LNA has a chip size of 1.6 mm $\times 1$ mm, and the total power consumption is 74 mW. To the best of our knowledge, the proposed LNA is the state-of-the-art Ka -band switchable LNA and has similar performance compared with single-band LNAs using the same technology.