Yu. M. Poplavko

Frequency-tunable microwave dielectric resonator

A new type of tunable composite dielectric resonator (DR) has been designed, In the structure of this DR, a controllable insert was used to change the resonance frequency (f/sub 0/) in a wide spectral range, while preserving a high quality factor. The simplest of proposed resonance systems for obtaining f/sub 0/ control is a microwave DR crossed by an air slot, which is controlled by fast piezoelectric actuator. Analytical and experimental techniques were employed for optimization of the composite DR structure. It has been observed that this device can create a change up to 20%-25% in its resonance frequency.

Microwave dielectric relaxation in barium lanthanide tetratitanates (BLT)

Abstract Polycrystalline monophase mixed oxides BaLn2Ti4O12 where Ln = La, Pr, Nd, Sm and Eu have been studied at the frequency interval 10–1013 Hz in temperature range 4–1000 K in order to established a reasons of unusual combination its properties: low microwave losses, high dielectric permittivity and its thermal stability. In the BLT we have first detected an intensive electronic relaxation process with very low activation energy. The last suggesting that large polarizable and strongly coupled with the lattice 4f/5d hybridizated bonds viscously suppress paraelectric-like soft lattice mode.

Tunable dielectric resonator: Design and parameters

Dependences of normalized resonance wave-number versus normalized distance between parts of cube, sphere, disk, ring dielectric resonators (DR) and metal-dielectric resonator (MDR) are presented. Influence of resonators geometry and permittivity on resonant frequency alteration is discussed.

Ferroelectric non-hysteresis actuator for microwave tuneable devices

Low loss and highly tuneable microwave filters controlled by piezoelectric actuator are discussed. Dielectric or metallic parts of device should have the piezo-dirigible air gap between them. The most important for these devices is to use non-hysteresis relaxor ferroelectric ceramics with large electrostriction. Electromechanic way of control has restriction in the speed of operation, and this problem is estimated by the microwave investigation of relaxor ceramics that is used as main actuator material.

Microwave tunable filters with impedance step

Calculation of resonant frequencies and the characteristics for the coupling coefficients of quarter-wave resonators with an impedance step are discussed. The problems of numerical calculation and synthesis of filters based on resonators with stepped heterogeneity are considered, experimental results are submitted for consideration.

Microwave structures electromecanical reconfiguration for tunable devices elaboration

Various highly tunable low-loss microwave devices are elaborated by piezoelectrically induced mechanical changes in the microwave structures utilizing high Q dielectrics. In this connection, an effective dielectric constant, epsieff, of used composite structures is controlled by fast actuator that results in energy distribution within the devices. Typical device consist of dielectric and metallic parts with an air gap between them that provides the largest perturbation in the electromagnetic field. By mini-actuator, the size of the air gap is changed and, as a result, the epsieff can be tuned that is used for a device control. Highly tunable dielectric resonators as filters as well as wideband, low-loss phase shifters are realized experimentally

Thermomechanically induced pyroelectricity and its possible applications

Abstract The feasibility of pyroelectric response creation from piezoelectric crystals has been examined. Performance evaluation of pyroelectric detectors with working substances SiO2, Bi12SiO20, GaAs and other sphalerite crystals has been revealed.

The nature of dielectric thermostability of barium lantanoid tetratitanates

The problem of combining in barium lantanoid tetratitanates (BLT) polycrystalline compositions a high dielectric permittivity with its temperature independence and low microwave losses has been revealed. It is suggested that 4f/5d lantanoid bonds viscously suppress the interaction of large polarizable TiO6 octahedrons. This hypothesis has been verified by intensive electronic relaxation process with a low activation energy and by submillimeter waves absorption. Because of the last the microwave applications of BLT-compositions is bounded by frequency limit 3-5 GHz.