Optimization of design and fabrication for micromachined true time delay (TTD) phase shifters

Distributed techniques have been widely employed as a solution to obtain wide band circuits at microwave and millimeter wave band. This paper presents five different designs for true-time delay (TTD) phase shifters that are based on characteristic impedance of 75, 65 and 50 Ω coplanar waveguide (CPW) distributed microelectromechanical systems (MEMS) transmission line (DMTL), which are loaded with different designs and number of shunt capacitive switches. The TTD phase shifters are fabricated on a 675 μm high resistivity silicon (Si) wafer using surface micromachining process. The design operates up to Ku band with a measured return loss below −15 dB and an average loss of 2.3 dB/phase shift of 250° at 20 GHz. The TTD phase shifters have wide applications for high-performance of microwave and millimeter-wave integrated circuits.