Irina Golubeva

Low Loss Microwave Piezo-Tunable Devices

Tunable by the mechanical reconfiguration low loss dielectric filter and wide-band phase shifter are elaborated. Dielectric or metallic parts of device should have a piezo-dirigible air gap between them. Key idea is to provide strong perturbation in electromagnetic field in the region influenced by the mechanical control. Energy distribution within the device is controlled by fast piezo-actuator, and can be described as a change in the effective dielectric permittivity. Highly tunable devices are realized experimentally

Loss in tunable microstrip lines

Electromagnetic energy loss in the micro-mechanically tunable microstrip line is studied including dielectric loss in substrates medium and ohmic loss in metal electrodes. When total loss in the device is relatively small, loss mechanisms contribute additively, so complex effective permittivity can be used to account both phenomena. This simplifies analysis and design of tunable microstrip lines. It is shown that with micro-mechanical tuning both dielectric and metal loss decrease comparing to those of conventional line.

Calculation of frequency and power characteristics of the composite metal-dielectric resonator using the method of partial regions

A new method for calculating the frequency and power characteristics of different modes of a microwave metal-dielectric resonator has been proposed. The results of measurements of experimental specimens are presented that are in good agreement with calculation results. The relationships of the frequency and power characteristics of a resonator as a function of its geometrical and electrophysical parameters were obtained by using the method of partial regions. A high sensitivity of the main mode resonant frequency to the thickness of air inhomogeneity was detected. In this case the introduction of inhomogeneity increases the resonator Q-factor. Thus, the proposed design can be used as a high-Q tunable resonator.

Piezo-controlled dielectric phase shifter with microstrip and coplanar lines

Report presents design, simulation and study of new kind of microwave device, namely piezo-driven dielectric phase shifter. The study develops principles of hybrid type piezo-controlled devices.

Calculation of quality factor of tunable shielded cylindrical metal-dielectric resonator using mode matching technique

The paper discusses quality factor of shielded cylindrical metal-dielectric resonator tuned by means of variable air gap between resonators base and shield. Mode matching technique was used to estimate resonators quality factor taking into account dielectric and metal losses. It was shown that metal and dielectric losses decrease in case of the air gap inclusion.

Electromechanical Control over Effective Permittivity Used for Microwave Devices

Ferroelectrics are well known tunable dielectric materials. Permittivity of these materials can be controlled by an applied electrical bias field. Controllable permittivity leads to alteration of characteristics of tunable microwave components such as propagation constants, resonant frequency etc. However, dielectric losses in the ferroelectric-type tunable components are comparatively high and show substantial increase approaching to the millimetre waves due to fundamental physical reason.

Coplanar line based low loss microwave phase shifters with electromechanical control

Paper presents the study of phase shifters with mechanical control based on coplanar line. Reconfiguration in a form where signal line of coplanar waveguide can be lifted above substrate provides strong perturbation of electromagnetic filed and thus ensures strong sensitivity. Utilization of high-Q dielectric materials makes it possible to extend substantially the operation frequency range while maintain low loss. Need displacement may be reduced to the range of tens micrometers, thus allowing utilization of fast piezo-actuators or MEMS.

MEMS-Like Phase Shifter with Piezoelectric Control

This paper presents an attempt to realize control over effective parameters of transmission line utilising design suitable for MEMS applications. Proposed combined structure usually consists of two dielectric parts (or dielectric and electrode) with an air gap between them. By means of fast piezoelectric mini-actuator, the size of the air gap is changed. At present time phase shifters, based on varactor and PIN diodes constitute main options in MMICs.

Complex Effective Dielectric Permittivity of Micromechanically Tunable Microstrip Lines

It is considered an influence of physical-topological parameters of controlled microstrip lines where characteristics modification is achieved by signal electrode movement over the substrate on effective dielectric permittivity and electromagnetic energy loss in the line expressed in form of complex permittivity. There are stated the ways of increase of sensitivity of effective dielectric permittivity modification to signal electrode shift and loss decrease. There are determined ultimate characteristics of tuning and loss. There are represented calculations of transfer factor effective permittivity corresponding to experimental results. These results can be used for development of controlled resonant elements and phase shifters with application of electrically tunable micromovement devices, such as piezo- and electrostrictive actuators or microelectromechanic systems. Due to application of invariant relations of physical-topological parameters represented calculations are suitable for estimation of tuning factors and loss of devices with micromechanical control in a wide range of operating frequency with application of wide range of materials.

Tunability limits of the microstrip line with electromechanical control

The paper presents study of the tunable microstrip line with electromechanical control. The study derives dependencies of the effective permittivity and insertion loss on combination of substrate material properties and device dimensions. Asymptotic boundaries for effective permittivity and loss are derived.