A compact Ku-band 5-bit monolithic microwave integrated circuit (MMIC) phase shifter has been demonstrated. The total gate width of switching FETs and the total inductance of spiral inductors are proposed as the figures of merit for compactness. The phase shifter uses the T-type and PI-type high-pass filter (HPF)/band-pass filter (BPF) circuits in which FET "off"-state capacitances are incorporated as the filter elements. According to the figures of merit, the T-type is selected for 90-degree phase shift circuit and the PI-type is selected for the 45-degree phase shift circuit. The fabricated 5-bit phase shifter performs average insertion loss of 5.6 dB and RMS phase shift error of 3.77 degrees with die size of 1.65 mm 0.76 mm (1.25 mm2) in Ku-band.

A C-Ku band 5-bit MMIC phase shifter using optimized reflective series/parallel LC circuits is presented. The proposed circuit has frequency independent characteristics in the case of 180 phase shift, ideally. Also, an ultra-broad-band circuit design theory for the 180 optimized reflective circuit has derived, which gives optimum characteristics compromising between loss and phase shift error. The fabricated 5-bit MMIC phase shifter with SPDT switch has successfully demonstrated a typical insertion loss of 9.4 dB 1.4 dB, and a maximum RMS phase shift error of 7 over the 6 to 18 GHz band. The measured results validate the proposed design theory of the phase shifter.