Abstract:
Over the past few years, RF MEMS varactor and switches have attained significant interest in the field of telecommunication and Microwave engineering. These RF MEMS varactors have many advantages over the conventional
based varactors. Conventional solid state varactor use PIN diodes and are
composed of GaAs metals and semiconductors. But these varactors have
poor performance as compared to RF MEMS varactors in terms of various
parameters. RF MEMS varactors requires low voltage, consumes less power,
have high reliability,with high tunability, high isolation and less insertion loss
than the conventional solid state varactors.
This thesis presents a novel design and modelling of RF MEMS Varactor
to achieve low actuation voltage and wide tunability. The proposed design
consist of 3-bit tunable capacitor connected with beam. There are slits are
used in central plates to increase the area tuning capability of varactors. A
new beam design is proposed to reduce the stiffness of the beam which results
in reduction of pull in voltage to 3.8V. Optimized result is obtain using finite
element method (FEM) and CST microwave studio. Electrostatic actuation
is used in this model because of its low power consumption and simplicity of
fabrication. The proposed design is optimized using length, width of beam,
electrode and central plate. A 50 Ω coplanar waveguide line is used, and
optimized scattering parameter results are achieved for both actuated and
unactuated state. A standardized process having low losses gold CPW, which
is used to make complex circuits on high resistive silicon wafer and can be
used for frequency range upto 100GHz. There are eight states of capacitance
and at pull in voltage of 3.8V maximum tunability is achieved that is 159
%. Total Varactor design dimensions are 750 µm x 750 µm. The beam
having 2 µm thickness and low losses CPW is of gold material. Mechanical
simulation is done on Intellisuite software while electrical analysis done on
CST microwave studio.
