Martin Hudlicka

Bianisotropic route to the realization and matching of backward-wave metamaterial slabs

A concept of backward-wave bianisotropic composite medium matched to free space is suggested. It is based on the use of a uniaxial bianisotropic structure embedded into a matrix with negative effective permittivity. Since bianisotropy is easier to achieve in the optical range than artificial magnetism, this concept is prospective for optical backward-wave metamaterials. As an example of possible realizations, a microwave Omega-composite combined with a wire lattice is analytically studied.

Transmission characteristics of bianisotropic metamaterials based on omega shaped metallic inclusions

The authors report the transmission properties of omega shaped metallic inclusions on a dielectric medium that exhibits bianisotropic properties. The resonance frequencies of single omega resonators are investigated experimentally and numerically. The resonance frequency of an Ω structure depends on its orientation with respect to the incident electric field. Increasing the tail length of the Ω resonator causes a decrease in resonance frequency. Band gaps due to the magnetoelectric resonances are observed for various types of periodic omega arrays. A transmission band is observed when a periodic Ω media is combined with a negative permittivity media of periodic thin wires. The transmission band appears below the band gap of periodic omega media, in turn indicating right-handed behavior. A dual transmission band is obtained by composing two different types of metamaterials that are arranged periodically.

A triple wire medium as an isotropic negative permittivity metamaterial

This paper presents an effective medium approach to calculate the attenuation and phase constants of modes in a 3D connected wire medium both below and above the plasma frequency. Physical and nonphysical modes in the structure are identified for all the important lattice directions. According to this, the medium behaves as an isotropic material in the vicinity of the plasma frequency. These results were compared with the numerical simulation and it was observed that the wave spreads below the plasma frequency along all the important lattice directions with the same attenuation constant. This implies isotropic behavior of the 3D wire lattice below the plasma frequency, and thus this medium can be considered as an isotropic negative permittivity medium.

Design and Calibration of a Compact Quasi-Optical System for Material Characterization in Millimeter/Submillimeter Wave Domain

A compact quasi-optical setup based on conventional rectangular horn antennas and two symmetrical parabolic mirrors is designed to provide a plane wave on the material under test. To measure the scattering parameters at millimeter/submillimeter wavelengths, a commercial vector network analyzer and waveguide frequency extension units are used. The calibration of the system is performed with a simple practical deembedding process to determine the S-parameters on the material surface without using high-cost micrometer positioners. A reliable extraction method is presented to derive the material permittivity and calculate the errors and uncertainties as direct functions of the sample and setup geometry and their physical characteristics. Several materials are measured and the complex permittivity is presented together with a detailed uncertainty budget.

Calibration of Wideband Digital Real-Time Oscilloscopes

The representation of the calibration results are discussed for Digital Real-Time Oscilloscopes and an algorithm is described that selects calibration frequencies to avoid instrument impairments. Measurement examples are given.

A reliable simple method to extract the intrinsic material properties in millimeter/sub-millimeter wave domain

A simple method is presented to extract the material characteristics from the scattering parameters in the frequency domain. The method is based on “transmission” measurement data only and can give the complex permittivity and/or the absorption and refraction index via easy arithmetic operations with closed-form formulas. Therefore, a parametric error analysis will be feasible for metrological aspects to show important uncertainty contributions. The actual measurements have been performed with a compact quasi-optical free-space setup in the frequency band from 50 GHz to 500 GHz and the detailed results are presented to show the performance of the method.

Calibration of wideband digital real-time oscilloscopes

We describe a frequency selection algorithm for calibrating the impulse-response (vector frequency response) and timebase characteristics of digital real-time oscilloscopes (DRTOs). The objective of the algorithm is to allow the DRTO to be calibrated as closely as possible to a chosen frequency grid while optimizing oversampling, timebase fidelity, and minimizing the uncertainty contribution due to instrument impairments. Measurement examples are given for cases where the measurement frequency can be selected by the user and where this frequency is predetermined. The use of the Allan variance in the frequency-selection process is described, and an algorithm and an example for interchannel delay measurement are presented. We also discuss the merits of representing the calibration results either as a convolutional correction or as an impulse response.

Waveform metrology for error vector magnitude measurements in a 300 GHz transmission system

The paper presents results of error vector magnitude (EVM) measurements in a 300 GHz transmission system. The EVM was determined using real-time oscilloscope and consecutive mathematical processing in a computer instead of using a commercial vector signal analyser. The uncertainty of EVM measured with the real-time oscilloscope is open to analysis.

Triple wire medium for use in isotropic metamaterials

In this paper a triple wire medium is described as an isotropic negative permittivity medium. A numerical experiment was performed to validate the propagation of electromagnetic waves inside the wire lattice below the plasma frequency, where the effective medium permittivity is negative. For a practical realization, a form of the triple wire medium using a planar technology was designed, fabricated and measured.

BER estimation from EVM for QPSK and 16-QAM coherent optical systems

BER estimation from measured EVM values is shown experimentally for QPSK and 16QAM optical signals with 28 GBd. Various impairments, such as gain imbalance, quadrature error and timing skew, are introduced into the transmitted signal in order to evaluate the robustness of the method. The EVM was measured using two different real-time sampling systems and the EVM measurement accuracy is discussed.