Design of a Wideband CMOS Digital Step Attenuator with High Accuracy and Low Phase Error

This paper demonstrates a wideband CMOS digital step attenuator (ATT) with high accuracy and low phase error working at 25GHz to 33GHz with 40nm CMOS technology. Shunt capacitors in the ground path are adopted for phase error compensation in bridged-T, T and π type ATT. The attenuation range is 15.5dB and the step is 0.5dB. The root-mean-square (RMS) attenuation error of the ATT can be less than 0.25dB and RMS phase error can be less than 1° under the whole bandwidth.