A DC-23 GHz Broadband Digital Step Attenuator MMIC Using Capacitive-Inductive Joint Compensation

This letter presents a broadband, low insert loss (IL) 6-bit switch-type digital step attenuator (DSA) implemented in a 0.25- $\mu \text{m}$ GaAs pHEMT process. The $\pi $ -type attenuation units adopt the proposed capacitive-inductive joint compensation technique, in which the inductor demonstrates an effective zero-pole adjustment to broaden the bandwidth. This DSA maintains a 31.5 dB attenuation range with a 0.5 dB step. Measured results indicate that the root-mean-square (rms) amplitude error is below 0.35 dB and the rms phase error is less than 5° from dc to 23 GHz. The IL is 4.0–6.2 dB. The core area excluding pads is only 0.47 mm2. To the best of our knowledge, this attenuator achieves the widest operating bandwidth among the switch-type GaAs DSAs.