Technological evolution and performances improvements of a tunable phase‐shifter using liquid crystal

Large Microwave Birefringence Liquid-Crystal Characterization for Phase-Shifter Applications

“…In order to improve the phase-shift variation, we can change the circuit configuration, 11) and/or use a higher microwave birefringence liquid crystal. Here, we have replaced the 5CB liquid crystal with the mixture presented in §3.…”

Epitaxially grown ferroelectric thin films for agile devices

“…Also MMIC technology FET transistors, with very low power consumption, are used as on-off switches in digital circuits [5], but their insertion losses are high; (ii) Micro Electro Mechanical Systems (MEMS), processed in the shape of cantilevers or bridges, give access to switches or variable capacitors, used in agile filters [6] or phase shifters [7]; their insertion losses are low, but the technology of their integration in microwave devices is quite complex; (iii) magnetic materials (mainly yttrium iron garnet [8] or ferromagnetic materials [9]) use the variation of magnetic permeability under application of an external magnetic field; their main drawbacks are long response time and large size; (iv) liquid crystals, in their nematic phase, exhibit a dielectric anisotropy that changes under an applied electric field: this property has been used to built agile phase shifters and capacitors [10][11][12]; however their insertion losses are still too high [13]; (v) ferroelectric compounds are currently very attractive materials for applications in electrically tunable high-frequency devices [14], as these materials are characterized by nonlinear dielectric properties [15] and then exhibit an electric field dependent dielectric permittivity (") driven by a DC voltage [16].…”

Wcip Applied to Active Plasma Circuits

“…Nevertheless, such components are characterized by a noise level which is detrimental to the system noise figure. Tunable techniques based on electrically controllable material such as ferroelectric [4][5][6], liquid crystal [7] or ferromagnetic material [8][9][10] can be used. However, such components suffer from long reaction time and power consumption.…”