@inproceedings{EibertEberspaecher, author = {Eibert, Thomas F. and Ebersp{\"a}cher, Mark A.}, title = {Analysis and Design of Composite Right/Left-Handed Periodic Waveguides and Leaky-Wave Antennas by Even/Odd-Mode Techniques, N{\"u}rnberg, Deutschland}, series = {Workshop im Rahmen der European Microwave Week (EUMW)}, booktitle = {Workshop im Rahmen der European Microwave Week (EUMW)}, language = {en} } @article{EberspaecherEibert, author = {Ebersp{\"a}cher, Mark A. and Eibert, Thomas F.}, title = {Dispersion Analysis of Complex Periodic Structures by Full-Wave Solution of Even-Odd-Mode Excitation Problems for Single Unit Cells}, series = {EEE Transaction on Antennas and Propagation}, volume = {61}, journal = {EEE Transaction on Antennas and Propagation}, number = {12}, publisher = {IEEE}, doi = {10.1109/TAP.2013.2283279}, pages = {6075 -- 6083}, abstract = {The Bloch modes of complex periodic structures are computed by superimposing results obtained from even-odd-mode full-wave driven simulations of individual unit cells. In order to emulate the periodic boundary conditions for the Bloch modes, one full-wave simulation is performed with magnetic and one with electric boundary conditions yielding the even- and odd-mode results, respectively. Therefore, the employed full-wave solver does not even need to support periodic boundary conditions. Since the non-periodic boundary conditions can be arbitrary, even open and radiating problems can be analyzed. The excitation of the structures is performed by discrete ports, which are located appropriately in order to excite the desired mode, typically the fundamental mode of the background structure. The found even- and odd-mode impedances deliver directly the complex propagation constant and the Bloch impedance of the periodic structure without any iterative search and under consideration of all electromagnetic interaction effects. This is in contrast to alternative solution methods, which require to solve computationally intensive eigenproblems or many excitation problems. Moreover, this approach allows to determine the field data corresponding to the Bloch mode, where arbitrary real and complex modes can be handled. Numerical results for different classes of problems including 1D and 2D microstrip structures as well as hollow waveguide based unit cells are presented.}, language = {en} } @inproceedings{EberspaecherEibert, author = {Ebersp{\"a}cher, Mark A. and Eibert, Thomas F.}, title = {Bloch mode analysis by even-odd-mode simulations}, series = {7th European Conference on Antennas and Propagation (EUCAP), G{\"o}teborg, Schweden}, booktitle = {7th European Conference on Antennas and Propagation (EUCAP), G{\"o}teborg, Schweden}, publisher = {IEEE}, abstract = {An analysis method is presented which allows to determine the Bloch modes of periodic structures by superimposing their even- and odd-modes. In order to conserve the periodic behavior of the electromagnetic field of the Bloch mode, the even-odd-modes are obtained by performing electromagnetic full-wave simulations using electric and magnetic boundary conditions, respectively. Since these two boundary conditions are only used to emulate the periodic boundary conditions, the remaining boundaries can be chosen arbitrarily. Thus, even open and radiating problems can be analyzed.}, language = {en} } @article{EberspaecherEibert, author = {Ebersp{\"a}cher, Mark A. and Eibert, Thomas F.}, title = {Analysis of Composite Right/Left-Handed Unit Cells Based on Even-Odd-Mode Excitation}, series = {IEEE Transaction on Microwave Theory and Techniques}, volume = {60}, journal = {IEEE Transaction on Microwave Theory and Techniques}, number = {5}, publisher = {IEEE}, doi = {10.1109/TMTT.2012.2188722}, pages = {1186 -- 1196}, abstract = {Even-odd-mode analysis is applied to symmetric composite right/left-handed (CRLH) structures in order to decompose the network into the two impedances Z e and Z o . It is shown that these impedances are sufficient to completely describe the behavior of arbitrary symmetric CRLH structures. Consequently, the propagation constant, as well as the Bloch impedance, are derived based on Z e and Z o . Furthermore, the balancing condition, as well as the band limits, are formulated in terms of poles and zeros of Z e and Z o . This simplifies significantly the analysis and design process of unit cells, especially when the structure comprises transmission lines. The theoretical expectations are validated by circuit simulations and electromagnetic simulations, as well as measurements of fabricated prototypes.}, language = {en} } @inproceedings{EberspaecherEibert, author = {Ebersp{\"a}cher, Mark A. and Eibert, Thomas F.}, title = {An Analysis and Design Procedure for Composite Right/Left-Handed Unit Cells}, series = {6th European Conference on Antennas and Propagation (EUCAP), Prag, Tschechische Republik}, booktitle = {6th European Conference on Antennas and Propagation (EUCAP), Prag, Tschechische Republik}, publisher = {IEEE}, doi = {10.1109/EuCAP.2012.6205901}, pages = {1391 -- 1394}, abstract = {A practical approach to design composite right/left-handed unit cells is presented which is based on the impedances obtained by even-odd mode excitation. Typical cell characteristics including the balancing condition are derived in terms of poles and roots of these impedances. In a design process based on EM-simulations, this allows immediately to identify the unit cell parameters to be modified in order to meet given specifications. The concept is applied to a unit cell based on microstrip technology and verified by measurements.}, language = {en} } @article{EberspaecherBauerEibert, author = {Ebersp{\"a}cher, Mark A. and Bauer, Marius and Eibert, Thomas F.}, title = {Design and Analysis of an Isotropic Two-Dimensional Planer Composite Right/Left-Handed Waveguide Structure}, series = {Advances in Radio Science}, volume = {9}, journal = {Advances in Radio Science}, doi = {10.5194/ars-9-73-2011}, pages = {73 -- 78}, abstract = {A two-dimensional isotropic Composite Right/Left-Handed (CRLH) waveguide structure is proposed which is designed for operation in X-band. The balanced structure possesses left-handed behaviour over a large bandwidth from 7.5 GHz up to its transition frequency at 10 GHz. Above this region, the unit cell behaves in a right-handed manner up to 13.5 GHz. Operating the structure within these bands yields a frequency dependent index of refraction ranging from -2.5 ≤ n ≤ 0.8. Isotropic characteristics are obtained between 8.5 GHz ≤ f ≤ 12 GHz resulting in -1.5 ≤ n ≤ 0.8. The planar CRLH structure is designed based on transmission line theory, implemented in microstrip technology and optimized using full-wave simulation software. An equivalent circuit model is determined describing the electromagnetic behaviour of the structure whose element values are obtained by even and odd mode analysis. The design of the unit cell requires an appropriate de-embedding process in order to enable an analysis in terms of dispersion characteristics and Bloch impedance, which are performed both.}, language = {en} } @inproceedings{EberspaecherEibert, author = {Ebersp{\"a}cher, Mark A. and Eibert, Thomas F.}, title = {Extraction of Embedded Dispersion Characteristics}, series = {Asia Pacific Microwave Conference (APMC), Melbourne, Australien}, booktitle = {Asia Pacific Microwave Conference (APMC), Melbourne, Australien}, pages = {801 -- 804}, abstract = {A de-embedding method is presented which allows to extract the dispersion characteristics of embedded periodic waveguiding structures. It is shown that the only required reference standard is a Thru dummy. Except symmetry, no further requirements on the dummy are requested. Particularly, the Thru does not need to possess a certain network topology, like T or π-shaped network. Furthermore, no equivalent circuit needs to be assumed. By adding an additional Line standard S-parameters may also be determined.}, language = {en} } @inproceedings{EberspaecherEibert, author = {Ebersp{\"a}cher, Mark A. and Eibert, Thomas F.}, title = {A Narrow Via-free Composite Right/Left-Handed Leaky Wave Antenna with Low Cross-Polarization}, series = {IEEE Antennas and Propagation International Symposium, Toronto, Kanada}, booktitle = {IEEE Antennas and Propagation International Symposium, Toronto, Kanada}, publisher = {IEEE}, doi = {10.1109/APS.2010.5561739}, pages = {1 -- 4}, abstract = {A frequency scanned leaky wave antenna is proposed and designed for operation in X-band. The guiding structure is realized as a composite right/left-handed transmission line composed of planar, periodically arranged via-free unit cells, implemented in microstrip technology. The main focus of the work was on the optimization of the electric field polarization characteristics. Hence, a cross-polarization level is achieved which is at least 20 dB below the co-polarization. The resulting maximum gain of the antenna is 13.7 dBi with a beamwidth of 9.5°. Furthermore, several of these narrow leaky wave antennas could be arranged in parallel resulting in an array with a clearance of less than half of a free space wavelength and allowing grating lobe free operation.}, language = {en} } @inproceedings{OttEberspaecherEibert, author = {Ott, Arndt T. and Ebersp{\"a}cher, Mark A. and Eibert, Thomas F.}, title = {Ultra-Wideband Balun for Biconical Antenna Structures}, series = {IEEE Antennas and Propagation International Symposium, Toronto, Kanada}, booktitle = {IEEE Antennas and Propagation International Symposium, Toronto, Kanada}, publisher = {IEEE}, doi = {10.1109/APS.2010.5562124}, pages = {1 -- 4}, abstract = {In this paper the design of a novel feeding structure is presented which has almost no impact on the antenna peformance and is furthermore adjustable to the input impedance of the antenna. The designed balun is characterized by measurement and simulation results of the input reflection coefficient. A biconical antenna is simulated with the balun and a coaxial transmission line feed to show the influence on the radiation patterns in the Eand H-planes.}, language = {en} } @inproceedings{EibertEberspaecher, author = {Eibert, Thomas F. and Ebersp{\"a}cher, Mark A.}, title = {Treating Linear Antenna Arrays as Sampled Continuous Source Distributions}, series = {URSI International Symposium on Electromagnetic Theory, Berlin, Deutschland}, booktitle = {URSI International Symposium on Electromagnetic Theory, Berlin, Deutschland}, publisher = {IEEE}, doi = {10.1109/URSI-EMTS.2010.5637265}, pages = {707 -- 710}, abstract = {Linear antenna arrays are usually described by the product of an array factor and a single element pattern. For certain configurations, such as the uniform linear array, the array factor can be obtained analytically by summing up the corresponding polynomial representation. The alternative of treating an array of finite extent as sampled continuous source distribution has been introduced many years ago, where however, the not very intuitive z-transformation approach has often been utilized in order to obtain closed form representations for many linear array configurations. In this paper, we work with sampled continuous source distributions and discuss their representation with Fourier transforms rather than with z-transforms. The relation to dispersion diagrams is shown and sampling with alternating sign is discussed. Particular focus is on leaky-wave antennas, where radiating TEM-waveguides, rectangular hollow waveguides, and composite right/left-handed waveguides together with the corresponding leaky-wave antennas are considered.}, language = {en} } @article{EberspaecherEibert, author = {Ebersp{\"a}cher, Mark A. and Eibert, Thomas F.}, title = {Leaky wave antenna with amplitude controlled beam steering based on composite right/left-handed transmission lines}, series = {Advances in Radio Science}, journal = {Advances in Radio Science}, doi = {10.5194/ars-8-27-2010}, pages = {27 -- 32}, abstract = {An antenna comprising two different composite right/left-handed transmission line structures is proposed which enables easy beam steering at an operation frequency of 10 GHz. The composite right/left-handed transmission lines are based on planar, periodically arranged via free unit cells, implemented in microstrip technology. Both transmission lines exhibit the infinite wavelength phenomenon which occurs at 9.72 GHz and 9.89 GHz, respectively. Thus, operating the different leaky wave structures at 10 GHz, radiation with azimuth angles of ±8° and ±17° can be achieved depending on the selected input port. In order to obtain a tunable main beam direction, the radiation patterns of both structures are superimposed by feeding them simultaneously. The influence of each guiding structure, and hence the direction of the main beam, can be controlled via the feeding amplitude. As a result of this, the beam can be steered between ±17° with a gain of up to 10 dBi. The guiding structures are arranged in parallel with a clearance of a=12.2 mm which is less than half of the wavelength in free space. This allows in a further step the attachment of additional guiding structures in order to increase the tunable angle range or creating an antenna array with a small beamwidth in the elevation plane without the occurrence of grating lobes. An antenna prototype was fabricated and validated by measurements.}, language = {en} }