A CMOS 2.4 GHz tunnable RF bandpass filter in 0.35μm technology

A tunable Q-enhanced bandpass filter is presented. The Q of the passive inductors that form the filter resonators is enhanced using a cross-coupled differential pair of transistors which is degenerated by a negative resistance. This technique allows compensation of frequency dependent inductor losses and ensures the Q-enhanced LC resonators to have frequency behaviour close perfectly ideal in the pass band of the filter. The filter centered at 2.4 GHz with a 31.5 MHz bandwidth is tunable in frequency by 3.75%, exhibits a -33 dBm for 1-dB compression point and a 16.64 dB noise figure while consuming 4 mW of power. The circuit was simulated in AMS 0.35 μm CMOS technology.