Victor Kazmirenko

Electrically Tunable Phase Shifters With Air-Dielectric Sandwich Structure

Abstract : Electrically tunable microwave phase shifter was developed by inserting dielectric slab and piezoelectric actuator inside a waveguide. Air-dielectric sandwich structure of dielectric material and thin air gap was placed inside a waveguide, where the thickness of air gap is controlled by the actuator. Small changes in the ratio between the thickness of dielectric material and air gap induce significant changes in the effective dielectric constant of the air-dielectric sandwich structure. Phase shifts of 20 ^ 200 degrees were realized with the dielectric materials such as (Mg, Ca)TiO3 while the thickness of air gap is changed between 0 to 30 micrometers by piezoelectric control. Since the dielectric ceramics has very small loss (tan delta ^ 10 (exp-4)) and the air gap has practically no loss, the total structure shows low insertion loss.

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

Low loss phase shifter based on piezo-controlled layered dielectric structure

Layered structure made of high-/spl epsiv/ dielectric and piezo-controlled air slot, filling various type waveguides, is used as tunable low loss wide-band phase shifter. A contemporary piezoelectric actuator is employed for fast variation of air slot width. This alteration results in considerable change in effective dielectric constant /spl epsiv//sub ef/ of the structure. Using high quality microwave dielectrics, it is possible to realize low loss phase shifters in the microwave as well as in the millimeter wave region.

Non-resonant, electrode-less method for measuring the microwave complex permittivity of ferroelectric thin films

A procedure is described for measuring the complex permittivity of dielectric thin films with relatively large dielectric constants (e: about 102–104) and considerable losses (tan δ: about 10−3–1). The ferroelectric films studied here are deposited on a relatively low-e dielectric substrate and placed in the centre of a rectangular waveguide parallel to the direction of wave propagation. The dielectric constants and losses of thin films are determined not by the shift of the resonant peak, but by numerical analysis of measured scattering parameters using a vector network analyser. The proposed method does not require electrode deposition on the film surface, and provides the natural properties of the film without complications due to conductive electrodes and their interfaces.

Q-factor of tuned microstrip resonator

The paper presents research of quality factor in the micro-mechanically tunable microstrip resonator and its change in response to tuning. In the presented design unloaded quality factor increases about 10% during tuning due to reduction of dielectric loss in substrate’s 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 loss reduction and frequency tuning.

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.

Dielectric based frequency agile microwave devices

Low loss highly tunable microwave material can be fabricated using dielectric laminate structure in which effective dielectric constant /spl epsiv//sub ef/ is efficiently controlled. The proposed combined structure usually consists of two dielectric parts with an air gap between them. This gap has to be arranged in such a way that provides the largest perturbation in the electromagnetic filed. By means of fast piezo electric mini-actuator, the size of the air gap is changed. As a result, the /spl epsiv//sub ef/ of given structure strongly varies that is used for device control. Wideband low loss waveguide phase shifters, highly tunable dielectric resonators, and based on them 20%-tunable filter are realized experimentally.

Q-factor of micromechanically tuned microstrip resonator

The paper presents study of quality factor in the micro-mechanically tunable microstrip resonator and its change in response to tuning. In the presented design unloaded quality factor increases about 10 percent during tuning due to reduction of 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 loss reduction and frequency tuning.

Quality factor of tunable shielded cylindrical metal-dielectric resonator

The paper discusses quality factor of tunable shielded cylindrical metal-dielectric resonator taking into account dielectric and metal losses. It was shown that both metal and dielectric losses decrease in case of the air gap inclusion. It was investigated that the dielectric loss has local minimum.

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.