Optimized Liquid Crystals (LCs) for microwave applications enable the design of low loss and, due to their direction dependent permittivity, continuously tunable RF components.
The development of methods concerning their numerical modeling and dielectric characterization within the microwave region as well as the design of tunable transmission line phase shifter and analog RF circuits constitute the main content of this thesis.
For this purpose, design techniques for tunable circuits are derived, in order to expand the modern network synthesis by considering the specification of variable transfer functions.
To enable the modeling and hence the design of lc-based rf-components, new material characterization methods and measurement setups have been developed.
This allows the accurate estimation of the anisotropic dielectric properties of nematic liquid crystal followed by the synthesis of LCs with improved performance.
Further investigations combine numerically aided broad- and narrowband characterization methods with analytical techniques.
This enables an efficient and accurate estimation of the complex dielectric properties by performing just one simulation in conjunction with the described Eigen-dielectric formulation.
Using the knowledge thus obtained, various LC-filled waveguide topologies are extensively investigated regarding their suitability as tunable transmission line phase shifter.
Their characteristics like tunability, switching behavior and loss mechanism are calculated by using a multiphysics simulation tool which has been developed for this purpose.
Beside the provided insight into the physical working mechanism behind these structures, also there optimal design, new topologies and advanced steering concepts for transmission line phase shifters are discussed.
Based on this, variable Ka-band delay line phase shifters for phased array antennas in "Low Temperature Cofired Ceramics" (LTCC)-and hollow waveguide technology are designed, fabricated an measured.
The commonly used multi-layer LTCC-technology enables the integration of digital and analog circuitry, bias networks and rf-elements within a single module and features a very high package density.
On the other hand, accordingly designed hollow waveguides with partially LC filling, lead to the highest electrical performance which has been published in recent works.
They offer the development of components like electronically tunable high gain antennas for space applications. | English |