An Ultra-wideband (UWB), 1-to-6 GHz, 4-bit phase shifter design is presented. The proposed phase shifter utilizes lumped-element, three-stage all-pass network to achieve UWB phase characteristics. Ideal predesign of the phase shifter is done successfully by following the three-stage all-pass network design procedure described in this paper. Following the ideal predesign, circuit elements are implemented using lumped planar spiral inductors (PSIs) and Metal-Insulator-Metal (MIM) capacitors for each phase shift bit and a practical design incorporating element parasitics is accomplished. The simulation results for each phase shift bit as well as all bit-states are provided for the practical design and the ideal one along with phase-related error information. According to the simulation results, the practical design exhibits a maximum rms phase error of 5.3% over 1-6 GHz frequency band. Prototype planar spiral inductors are fabricated using an in-house surface micromachining technology and a good agreement is attained between the simulation and measurement results, which validates the design procedure. © 2012 IEEE.