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Comparative design of millimeter wave RF-MEMS phase shifters

Kobal, Enis
Phase shifters are widely used for electronic beam steering for various antenna applications. This thesis presents design and comparison of 3 di erent 3-bit transmission type phase shifters, which are switch-line, Distributed MEMS Transmission Line (DMTL) and triple stub phase shifters, realized with capacitive contact Radio Frequency (RF) Micro-Electro-Mechanical Systems (MEMS) switches for Ka-Band applications. For the design of switch-line phase shifter reducing the sensitivity of the electrical performance to the fabrication tolerances and by this way increasing the yield is targeted by minimizing the air-bridges used in the design. In order to achieve this, new Coplanar waveguide (CPW) T-junction and CPW bend structures are designed. For DMTL phase shifter design, a new method based on using circuit models is used instead of the conventional DMTL phase shifter for reducing the computational work and for preventing to obtain an inapplicable design, because of the dimensions, with the conventional method. In this thesis also a triple stub phase shifter is designed with the motivation of reducing the number of control bits. Comparisons of these phase shifters are done in terms of their insertion/return losses, maximum phase errors, bandwidths at 35 GHz, pull-in voltages of the switches used in the designs, layout dimensions of the phase shifters and number of control bits of the phase shifters. DMTL phase shifter is the most favourable phase shifter in terms of its low loss, small size and low pull-in voltage. Whereas switch-line phase shifter shine outs only with its large bandwidth. Compared with DMTL and switch-line phase shifters, triple stub phase shifter is only favourable in terms of its layout dimensions.