Dmitri Lioubtchenko

Simple and Accurate Analytical Model of Planar Grids and High-Impedance Surfaces Comprising Metal Strips or Patches

Simple analytical formulas are introduced for the grid impedance of electrically dense arrays of square patches and for the surface impedance of high-impedance surfaces based on the dense arrays of metal strips or square patches over ground planes. Emphasis is on the oblique-incidence excitation. The approach is based on the known analytical models for strip grids combined with the approximate Babinet principle for planar grids located at a dielectric interface. Analytical expressions for the surface impedance and reflection coefficient resulting from our analysis are thoroughly verified by full-wave simulations and compared with available data in open literature for particular cases. The results can be used in the design of various antennas and microwave or millimeter wave devices which use artificial impedance surfaces and artificial magnetic conductors (reflect-array antennas, tunable phase shifters, etc.), as well as for the derivation of accurate higher-order impedance boundary conditions for artificial (high-) impedance surfaces. As an example, the propagation properties of surface waves along the high-impedance surfaces are studied.

Dielectric rod waveguide antenna for W band with good input match

Antennas based on dielectric rod waveguide made of GaAs and fused sapphire cut along its optical axis inserted in the end of a standard WR-10 metal waveguide are investigated with computer simulations and experiments in the W band. The radiation pattern is found to be similar to that of the open metal waveguide end, but less frequency-dependent beamwidth and input match: measured return loss is more than 25 dB.

Low-loss sapphire waveguides for 75-110 GHz frequency range

Low-loss dielectric waveguides are promising for use instead of metal ones, but problems in transitions have to be overcome. A simple and effective structure made of a monocrystalline sapphire waveguide has been designed. Experimental results at 75-110 GHz indicate good matching with metal waveguides (VSWR /spl les/1.13) and low insertion loss (0.05-0.35 dB for 47 mm dielectric section).

Analog-type millimeter-wave phase shifters based on MEMS tunable high-impedance surface and dielectric rod waveguide

Millimeter-wave phase shifters are important components for a wide scope of applications. An analog-type phase shifter for W-band has been designed, analyzed, fabricated, and measured. The phase sh ...

Dielectric Rod Waveguide Antenna as THz Emitter for Photomixing Devices

We propose a dielectric rod waveguide antenna (DRW) integrated with a photomixer as a THz emitter. This represents a different approach as opposed to the classical solution of a substrate lens. Main goals are an inexpensive alternative to substrate lenses, reduction of both reflections on the semiconductor-air interface and scattering of terahertz-generated power into the substrate. A radiation pattern measured at 137 GHz is shown as a proof-of-concept. In order to increase radiated power, the improvement of the rod antenna is discussed. Finally, as an application example, evanescent coupling of the DRW into a high index whispering gallery mode resonator is shown.

Millimetre-Wave Phase Shifter Based on Dielectric Rod Waveguide

In this work we propose a novel millimetre-wave phase shifter targeted on thin ferroelectric film technology. Architecture of the phase shifter is proposed to use a dielectric rod waveguide with a periodic printed array of electrically small dipoles loaded with a ferroelectric varactor (pin diode, Schottky diode, etc.) with the function of control the phase of the propagating wave. The proposed architecture of the phase shifter is verified by measuring two prototypes, where the tuneable elements (ferroelectric varactor) are replaced by non-tuneable capacitors with 10 fF and 15 fF respectively. The measurements revealed a considerable phase shift and small insertion losses. It is demonstrated that the proposed periodic structure using the dielectric rod waveguide allows to fully realize a potential of known tuneable elements at millimetre-wavelengths.

High permittivity dielectric rod waveguide antenna for 110-150 GHz

Based on high permittivity dielectric materials, silicon and sapphire, antennas for the frequency range 110-150 GHz were designed. Dielectric rod waveguide (DRW) antennas are travelling wave type of antennas with a wide operating frequency band. Suitable high permittivity dielectrics offer a reduced size compared to low permittivity materials without losing the waveguiding properties. No launching horns are needed either. The designs were studied with simulations and verified with measurements of the prototypes. Both simulation and measurement results show very wide band radiation characteristics with almost constant beamwidth.

Millimeter-wave permittivity measurement of deposited dielectric films using the spherical open resonator

A differential method using the spherical open resonator is developed for permittivity measurement of a thin dielectric film on an optically dense substrate. It is based on a measurement of the resonant frequency shift due to the thin film on the substrate. The accuracy of the method is demonstrated to be about 4% for a 5.6-/spl mu/m photoresist film at 142 GHz.

Differential open resonator method for permittivity measurements of thin dielectric film on substrate

A novel differential method based on the open resonator is developed for permittivity measurement of thin dielectric films on optically dense substrates at millimeter wavelengths. The method is based on measurement of resonant frequency shifts due to appearance of a thin film on upper and lower sides of the substrate. The advantages of the method are that there is no need to know the geometry of the open resonator nor the thicknesses of the film and substrate, though one has to measure separately dielectric properties of the substrate.

GaAs surface modifications under Au evaporating flux

Au films thermally evaporated in vacuum are different from pure Au. New compounds as Au3Ga, Au7Ga2 are formed during the evaporation and ‘‘free’’ (non-incorporated into the crystalline lattice) Ga and As atoms appear in the Au surface layer. In this work the GaAs surface state was investigated with surface acoustic waves in situ during thermal evaporation of Au. The changes of the aggregate state caused by the Au‐Ga liquid phase formation followed by the creation of the solid solutions based on the Au3Ga and the Au7Ga2 compounds are observed. Such transformations in the films seem to be determined by the diffusion of ‘‘free’’ Ga and As atoms towards the GaAs surface due to the plastic deformation induced by the Au evaporated flux. Data were confirmed by the precise chemical analysis and Auger electron spectroscopy. # 2003 Elsevier Science B.V. All rights reserved.