An Ultra-Wideband LNA with Notch Filter

An ultra-wideband (UWB) common-gate low noise amplifier with notch filter is proposed. For extending the bandwidth, the UWB LNA uses the stagger tuning technique of two stages with different resonant frequencies. The notch filter with extremely high quality factor provides deep rejection ratio to eliminate the in-band interference. The circuit is simulated with TSMC 0.18 mum mixed signal/RF CMOS process technology with 1.8 V power supply. The input reflection coefficient S
₁₁
and output reflection coefficient S
₂₂
are both less than -10 dB. The flat power gain (S
₂₁
) is higher than 11 dB while the maximum rejection ratio is over 49 dB at 5.77 GHz. The minimum noise figure is 5 dB.