Contactless electromagnetic measuring system using conventional calibration algorithms to determine scattering parameters

In this paper, a contactless measuring system for the determination of the S-parameters of planar circuits is presented. With a contactless measuring system it is possible to characterise a device-under-test (DUT) embedded in a planar circuit environment without cutting the planar transmission lines connecting the DUT. The technique utilizes four identical capacitive probes in conjunction with a vector network analyser (VNA). For the usage of electromagnetic probes compared to other coupling techniques like the electro-optic probing, there is no need for expensive and complex equipment in addition to the typical equipment of a common microwave laboratory. The S-parameters are determined accurately using conventional calibration methods. A simple analytical model for the representation of the basic characteristics is developed. Furthermore, the influences on the S-parameters as a result of a variation in the coupling are presented. With the knowledge of the system characteristics, an accurate contactless measurement system is set up. The comparison between conventional and contactless measurements in a frequency range of 1-20 GHz shows a very good agreement with a phase error smaller than 1°

Radiation pattern analysis of antenna systems for MIMO and diversity configurations

Multiple-input multiple-output (MIMO) antenna systems and antenna configurations for wideband multimode diversity rank among the emerging key technologies in next generation wireless communication systems. The analysis of such transmission systems usually neglects the influences of real antenna radiation characteristics as well as the influences of mutual coupling in a multielement antenna arrangement. Nevertheless, to achieve a detailed description of diversity gain and channel capacity by using several transmit-and receive antennas in a wireless link, it is essential to take all those effects into account. The expansion of the radiation fields in terms of spherical eigenmodes allows an analytical description of the antenna radiation characteristics and accounts for all the coupling effects in multielement antenna configurations. Therefore the radiation pattern analysis by spherical eigenmode expansion provides an efficient alternative to establish an analytical approach in the calculation of envelope correlation or channel capacity. © 2005 Copernicus GmbH

Computation of antenna pattern correlation and MIMO performance by means of surface current distribution and spherical wave theory

In order to satisfy the stringent demand for an accurate prediction of MIMO channel capacity and diversity performance in wireless communications, more effective and suitable models that account for real antenna radiation behavior have to be taken into account. One of the main challenges is the accurate modeling of antenna correlation that is directly related to the amount of channel capacity or diversity gain which might be achieved in multi element antenna configurations. Therefore spherical wave theory in electromagnetics is a well known technique to express antenna far fields by means of a compact field expansion with a reduced number of unknowns that was recently applied to derive an analytical approach in the computation of antenna pattern correlation. In this paper we present a novel and efficient computational technique to determine antenna pattern correlation based on the evaluation of the surface current distribution by means of a spherical mode expansion

Extended post processing for simulation results of FEM synthesized UHF-RFID transponder antennas

The computer aided design process of sophisticated UHF-RFID transponder antennas requires the application of reliable simulation software. This paper describes a Matlab implemented extension of the post processor capabilities of the commercially available three dimensional field simulation programme Ansoft HFSS to compute an accurate solution of the antenna's surface current distribution. The accuracy of the simulated surface currents, which are physically related to the impedance at the feeding point of the antenna, depends on the convergence of the electromagnetic fields inside the simulation volume. The introduced method estimates the overall quality of the simulation results by combining the surface currents with the electromagnetic fields extracted from the field solution of Ansoft HFSS

Spherical mode analysis of planar frequency-independent multi-arm antennas based on its surface current distribution

Deployment in the design of mobile radio terminals focuses on the implementation of multiradio transmission systems, using a multiplicity of different radio standards combined with high-speed data communication over multiple-input multiple-output (MIMO) and multimode diversity techniques. Hence, planar log.-per. four-arm antennas are predistined to meet the requirements of future mobile multiradio RF-frontends and will be introduced and analysed in terms of an efficient spherical mode analysis by means of surface current distribution in order to derive an analytic access to MIMO- and polarisation-diversity performance computation. A remarkable parameter reduction and a faster numerical analysis with respect to conventional techniques may be achieved. The sources in the near-field antenna region are based on the numerical computation of surface currents involving the finite element method (FEM). Relations between the variations of the geometrical antenna parameters and the excitation of discrete spherical modes are presented and will be analysed in detail

Considering even-order terms in stochastic nonlinear system modeling with respect to broadband data communication

As a tradeoff between efficiency and costs modern communication systems contain a variety of components that can at least be considered weakly nonlinear. A critical element in evaluating the degree of nonlinearity of any underlying nonlinear system is the amount of undesired signal strength or signal power this system is introducing outside the transmission bandwidth. This phenomenon called spectral regrowth or spectral broadening is subject to stringent restrictions mainly imposed by the given specifications of the particular communication standard. Consequently, achieving the highest possible efficiency without exceeding the linearity requirements is one of the main tasks in system design. Starting from this challenging engineering problem there grows a certain need for specialized tools that are capable of predicting linearity and efficiency of the underlying design. Besides a multitude of methods aiming at the prediction of spectral regrowth a statistical approach in modeling and analyzing nonlinear systems offers the advantage of short processing times due to closed form mathematical expressions in terms of input and output power spectra and is therefore further examined throughout this article

Determination of the input impedance of RFID transponder antennas with novel measurement procedure using a modified on-wafer-prober

This paper shows a new method to determine the input impedance of RFID transponder antennas with a combination of on-wafer-prober and network analyzer. It is shown that the results are in a good agreement with FEM simulations (HFSS) for a large part of the examined antenna structures

Design of Sievenpiper HIS for use in planar broadband antennas by means of effective medium theory

The claim for multistandard operating handsets of small physical size as well as the ever increasing demand for higher data rates require new broadband operating antennas. Because of the widespread use of especially planar broadband antennas a lot of factors influencing the characteristic antenna parameters have to be regarded. Furthermore, aspects regarding the electromagnetic compatibility inside the handheld as well as the protection of biological systems, e.g. the user of a mobilephone, have to be payed attention to. An electromagnetic structure which allows for protection by means of shielding as well as enhances the antennas efficiency by providing unique electromagnetic properties are the so called Sievenpiper High Impedance Surfaces (HIS) invented by Sievenpiper (1999). This paper will present the theory and the well known design equations for those structures. An investigation by means of simulation tools and measurement setups will be done to approve the accuracy of the theoretical results. Here measurement results of the impedance and radiation properties of a planar log.-per. fourarm antenna equiped in conjunction with a fabricated prototype Sievenpiper HIS will be presented

Negative phase time for Scattering at Quantum Wells: A Microwave Analogy Experiment

If a quantum mechanical particle is scattered by a potential well, the wave function of the particle can propagate with negative phase time. Due to the analogy of the Schr\"odinger and the Helmholtz equation this phenomenon is expected to be observable for electromagnetic wave propagation. Experimental data of electromagnetic wells realized by wave guides filled with different dielectrics confirm this conjecture now.Comment: 10 pages, 6 figure

Considering even-order terms in stochastic nonlinear system modeling with respect to broadband data communication

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