High-Performance Wideband Low-Noise Amplifier Using Enhanced $\pi$ -Match Input Network

A low noise-figure (NF) and high power gain (S21) 3 ~ 10 GHz ultra-wideband low-noise amplifier (UWB LNA) with excellent phase linearity using 0.18 μm CMOS technology is reported. An enhanced π-match input network is used to achieve wideband input impedance matching as well as high and flat S₂₁. To achieve low and flat NF, the pole frequency and pole quality factor of the second-order NF frequency response are tuned to approximate the maximally flat condition. The LNA consumes 18 mW, achieving S₁₁ better than -10 dB for frequency lower than 12.2 GHz and group-delay (GD) variation smaller than ±14.6 ps for frequencies 3 ~ 10 GHz. Additionally, high and flat S₂₁ of 13.7 ± 1.5 dB is achieved for frequencies 1 ~ 12.5 GHz, which means the corresponding 3-dB bandwidth is 11.5 GHz. Furthermore, the LNA achieves minimum NF of 2.2 dB at 4 GHz and NF of 2.3 ± 0.1 dB for frequencies of 3 ~ 10 GHz, one of the best NF results ever reported for a 3 ~ 10 GHz CMOS LNA.