A CMOS wide-bandwidth high-power linear-in-dB variable attenuator using body voltage distribution method

A wide bandwidth, highly linear variable attenuator designed in 0.18 μm triple-well CMOS process is presented. This attenuator is based on three cascade π-networks with body voltage distribution scheme to minimize the effects of the input power levels. Measurements show it achieves minimum 1-dB gain compression of 7.5 dBm. The mid-band insertion loss is 1.6 dB and the maximum attenuation is 34.8 dB. This attenuator has a linear-in-dB controllability from 400 MHz to 3.7 GHz with input return loss better than 9 dB. To our knowledge, this is the highest linear CMOS variable attenuator with a wide bandwidth of 3.3 GHz.