A switched T-attenuator using 0.18?m CMOS optimized switches for DC-20GHz
A switched T-attenuator for DC-20GHz 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 2125dB, attenuation flatness of <2.4dB, and insertion loss of 0.62.1dB over DC-20GHz frequency band. The worst-case input/output return loss is better than 10dB at DC-20GHz with the RMS phase imbalance of <12 (average of 7.4). The circuit is implemented in a standard 0.18?m CMOS technology and the post-layout simulation results are reported.
cmos flatness attenuation range insertion loss switched attenuator minimum/maximum attenuation