A compact CMOS UWB LNA using tunable active inductors for WLAN interference rejection

A compact 2.0-11.0GHz CMOS ultra-wideband (UWB) low-noise amplifier (LNA) using tunable active inductors for suppressing in-band (over 4.8-6.0 GHz) WLAN interference signals is presented. In the proposed LNA, the active inductor in series with a small capacitor forms an active LC resonator which rejects or notches the undesired signals at the resonance frequency. Employing multiple resonators in the LNA increases the rejection depth. Moreover, the tunability of the active inductors allows for notching the signals over a wide frequency range. Designed and simulated in a 90 nm digital CMOS process, the proposed LNA with such active inductors used in notch filters occupies a core chip-area of only 0.0182 mm². The LNA exhibits an average power gain of 16.5 dB over 2.0-11.0 GHz bandwidth while the rejection of unwanted WLAN interference signals is -44.8 dB at 5.81 GHz. The notch-frequency can be tuned in excess of 4.5-6.6 GHz, and the rejection depth can be increased to -87.5 dB, the highest rejection among the reported notch-filter UWB LNAs.