-A high performance 6-18 GHz 5-bit reflection type phase shifter MMIC is presented. It employs a novel ultra-broad-band circuit design technique utilizing a series/parallel LC circuit for an 180 o phase shift over all frequencies. The fabricated phase shifter MMIC with SPDT switch suitable for T/R modules has demonstrated a typical insertion loss of 9.4 dB +/-1.4 dB, a maximum RMS amplitude error of 0.33 dB and a maximum RMS phase error of 7 o over entire operating bandwidths.