A switched T-attenuator using 0.18 μm CMOS optimized switches for DC-20 GHz

A switched T-attenuator for DC-20 GHz frequency band is presented. An nMOS-switch with optimized switching performance is used as shunt switch to improve the flatness and maximum attenuation range of the attenuator. Furthermore, the proposed attenuator has good impedance matching and reasonable phase imbalance. The design shows maximum attenuation range of 21–25 dB, attenuation flatness of <2.4 dB, and insertion loss of 0.6–2.1 dB over DC-20 GHz frequency band. The worst-case input/output return loss is better than 10 dB at DC-20 GHz with the RMS phase imbalance of <12° (average of 7.4°). The circuit is implemented in a standard 0.18 μm CMOS technology and the post-layout simulation results are reported.