A new passive vector modulator phase shifter (VMPS) based on a polar architecture is presented in this paper, suitable to be used in advanced beamforming feeding networks. Its cascaded structure of a reflection-type bi-phase variable attenuator (RTBVA) and a reflection-type phase shifter (RTPS) allows a great flexibility regarding phase and amplitude control, and reduces amplitude errors in the phase shifting. A printed circuit was designed and implemented, operating at a central frequency of 3.6 GHz with 5-bit of phase resolution, to validate the proposed concept. The measured results showed a 360° phase shift range, an average insertion loss of 2.4 dB @ 3.6 GHz, a root-mean-square phase and gain error of 1.3° and 0.06 dB, respectively. This VMPS also allows an amplitude control range of ~25 dB and an operation bandwidth of 0.7 GHz (19.4%).