A Ka-band 3-bit RF MEMS switched line phase shifter implemented in coplanar waveguide

A Ka-band 3 bit RF MEMS switched line phase shifter implemented in coplanar waveguide (CPW) on Borofloat™ glass substrate is presented. The basic switched line phase shifter unit is composed of two single-pole double-throw (SPDT) switches with phase offset transmission line lengths. Air-bridge with step compensation technique is used to improve the mm-wave performance of CPW discontinuities such as bend and Tee-junction. The SPDT switch composed of matched Tee-junction and two compact metal-to-metal contact series MEMS switches is optimized to obtain broad band performance. The three-bit phase shifter is designed to shift 0°, 45°, 90°, 135°, 180°, 225°, 270°, 315° at 35GHz and the measured RMS phase error is only 2.3°. The average insertion loss over all states is 2.35dB. Return loss is better than -12dB at Ka band for all eight states.