Complex Permittivity Measurements at Variable Temperatures of Low Loss Dielectric Substrates Employing Split Post and Single Post Dielectric Resonators

A split post dielectric resonator in a copper enclosure and a single post dielectric resonator in a cavity with superconducting end-plates have been constructed and used for the complex permittivity measurements of single crystal substrates. (La,Sr)(Al,Ta)O3, LaAlO3, MgO and quartz substrates have been measured at temperatures from 20 K to 300 K in the split post resonator and from 15 K to 80 K in the single post resonator. The TE01delta mode resonant frequencies and unloaded Qo-factors of the empty resonators at temperature of 20 K were: 9.952 GHz and 25,000 for the split post resonator and 10.808 GHz and 240,000 for the single post resonator respectively.Comment: 4 pages, 8 figures, 1 tabl

Discovery of Bragg confined hybrid modes with high Q-factor in a hollow dielectric resonator

The authors report on observation of Bragg confined mode in a hollow cylindrical dielectric cavity. A resonance was observed at 13.4 $GHz$ with an unloaded Q-factor of order $2\times10^5$, which is more than a factor of 6 above the dielectric loss limit. Previously such modes have only been realized from pure Transverse Electric modes with no azimuthal variations and only the $E_{\phi}$ component. From rigorous numeric simulations it is shown that the mode is a hybrid mode with non-zero azimuthal variations and with dominant $E_r$ and $E_{\phi}$ electric field components and $H_z$ magnetic field component.Comment: Accepted to be published in Applied Physics Letter

Detrapping and retrapping of free carriers in nominally pure single crystal GaP, GaAs and 4H-SiC semiconductors under light illumination at cryogenic temperatures

We report on extremely sensitive measurements of changes in the microwave properties of high purity non-intentionally-doped single-crystal semiconductor samples of gallium phosphide, gallium arsenide and 4H-silicon carbide when illuminated with light of different wavelengths at cryogenic temperatures. Whispering gallery modes were excited in the semiconductors whilst they were cooled on the coldfinger of a single-stage cryocooler and their frequencies and Q-factors measured under light and dark conditions. With these materials, the whispering gallery mode technique is able to resolve changes of a few parts per million in the permittivity and the microwave losses as compared with those measured in darkness. A phenomenological model is proposed to explain the observed changes, which result not from direct valence to conduction band transitions but from detrapping and retrapping of carriers from impurity/defect sites with ionization energies that lay in the semiconductor band gap. Detrapping and retrapping relaxation times have been evaluated from comparison with measured data.Comment: 7 pages, 6 figure

Whispering gallery resonator method for permittivity measurements, Journal of Telecommunications and Information Technology, 2002, nr 1

The new method of measuring permittivity is described. The measurements are performed using whispering gallery mode open dielectric resonators. The accuracy is assured by applications of the mode matching method. Three resonant modes (HE511, HE611 and HE711) are used in measurement procedure. Accuracy of the method is much better than 0.3% for the relative permittivity having values from 20 to 50

Application of dielectric resonators to surface impedance measurements of microwave susceptors

[EN] This paper describes the application of dielectric resonators (DR) to the measurements of surface impedance of microwave susceptors. We demonstrate that the single-post (SiPDR) configuration is applicable to plain susceptors before use, while the split-post (SPDR) configuration - to crazed susceptors after use. Attention is given to the full characterisation of active packaging, that is, the influence of paper support on the overall electric losses is also investigated. The measurements can be preformed with various form-factor VNAs, including benchtop VNAs and hand-held FieldFox, though the most economical setup is constructed with a dedicated computer-controlled microwave signal oscillator system available under the name of Q-Meter. Finally, an extension of dielectric resonator measurements to surface imaging is presented, achieved by incorporating the resonator in a 2D automatic scanner.This project has received funding from the European Union’s Horizon 2020 research and innovation programme (H2020-NMBP-07-2017) under grant agreement MMAMA No. 761036.Celuch, M.; Rudnicki, J.; Krupka, J.; Gwarek, W. (2019). Application of dielectric resonators to surface impedance measurements of microwave susceptors. En AMPERE 2019. 17th International Conference on Microwave and High Frequency Heating. Editorial Universitat Politècnica de València. 500-505. https://doi.org/10.4995/AMPERE2019.2019.9953OCS50050

Precise microwave characterization of MgO substrates for HTS circuits with superconducting post dielectric resonator

Accurate data of complex permittivity of dielectric substrates are needed for efficient design of HTS microwave planar circuits. We have tested MgO substrates from three different manufacturing batches using a dielectric resonator with superconducting parts recently developed for precise microwave characterization of laminar dielectrics at cryogenic temperatures. The measurement fixture has been fabricated using a SrLaAlO3 post dielectric resonator with DyBa2Cu3O7 end plates and silver-plated copper sidewalls to achieve the resolution of loss tangent measurements of 2 {\times} 10-6. The tested MgO substrates exhibited the average relative permittivity of 9.63 and tan {\delta} from 3.7 {\times} 10-7 to 2 {\times} 10-5 at frequency of 10.5 GHz in the temperature range from 14 to 80 K.Comment: 6 pages, 8 figures, 3 table

Low-loss Materials for high Q-factor Bragg Reflector Resonators

A Bragg resonator uses dielectric plates within a metallic cavity to confine the energy within a central free space region. The importance of the permittivity is shown with a better Q-factor possible using higher permittivity materials of larger intrinsic dielectric losses. This is because the electric energy in the reflectors decreases proportionally to the square root of permittivity and the coupling to the metallic losses decrease linearly. In a sapphire resonator with a single reflector pair a Q-factor of 2.34x10^5 is obtained, which may be improved on by up to a factor of 2 using higher permittivity materials