A digital 70?140-GHz impedance tuner in 130-nm CMOS technology

A novel structure of a digital controllable impedance tuner is proposed, operating from 70 to 140 GHz with special emphasis on easy control. 20 FETs are used for tuning the impedance. No parasitic compensation has to be applied on the FETs. Therefore the same impedance states can be generated in a wide frequency range and the area consumption of the tuner is small. A test chip of the tuner including an on-chip three wire interface is fabricated in a 130-nm CMOS technology. Based on deembedding structures, verification of the FET model is done in the W- and D-band. The tuners S-Parameters are measured on-wafer from 70 to 140 GHz. The tuner offers a quite constant maximum reflection coefficient over a full circle in the Smith chart.