TY - CHAP A1 - Eberspächer, Mark A. T1 - Simulation method for multiple reflections in near-field applications T2 - Proceedings of the German Microwave Conference, Stuttgart, Deutschland N2 - A field simulation procedure for structures where multiple reflections occur is presented. The basic objective is the computation of each particular reflection contributing significantly to the steady state reflection coefficient of a problem. The method is based on plane-wave field expansion including evanescent waves in order to account for near-field effects. As an example, an arrangement similar to a Fabry-Perot resonator is analyzed and the results are compared to that of a commercial field solver. Y1 - 2019 U6 - https://doi.org/10.23919/GEMIC.2019.8698171 ER - TY - CHAP A1 - Eibert, Thomas F. A1 - Eberspächer, Mark A. T1 - Analysis and Design of Composite Right/Left-Handed Periodic Waveguides and Leaky-Wave Antennas by Even/Odd-Mode Techniques, Nürnberg, Deutschland T2 - Workshop im Rahmen der European Microwave Week (EUMW) Y1 - 2013 ER - TY - JOUR A1 - Eberspächer, Mark A. A1 - Eibert, Thomas F. T1 - Dispersion Analysis of Complex Periodic Structures by Full-Wave Solution of Even-Odd-Mode Excitation Problems for Single Unit Cells JF - EEE Transaction on Antennas and Propagation N2 - 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. Y1 - 2013 U6 - https://doi.org/10.1109/TAP.2013.2283279 VL - 61 IS - 12 SP - 6075 EP - 6083 PB - IEEE ER - TY - CHAP A1 - Eberspächer, Mark A. A1 - Eibert, Thomas F. T1 - Bloch mode analysis by even-odd-mode simulations T2 - 7th European Conference on Antennas and Propagation (EUCAP), Göteborg, Schweden N2 - 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. Y1 - 2013 UR - https://ieeexplore.ieee.org/document/6546439 PB - IEEE ER - TY - JOUR A1 - Eberspächer, Mark A. A1 - Eibert, Thomas F. T1 - Analysis of Composite Right/Left-Handed Unit Cells Based on Even-Odd-Mode Excitation JF - IEEE Transaction on Microwave Theory and Techniques N2 - 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. Y1 - 2012 U6 - https://doi.org/10.1109/TMTT.2012.2188722 VL - 60 IS - 5 SP - 1186 EP - 1196 PB - IEEE ER - TY - CHAP A1 - Eberspächer, Mark A. A1 - Eibert, Thomas F. T1 - An Analysis and Design Procedure for Composite Right/Left-Handed Unit Cells T2 - 6th European Conference on Antennas and Propagation (EUCAP), Prag, Tschechische Republik N2 - 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. Y1 - 2012 U6 - https://doi.org/10.1109/EuCAP.2012.6205901 SP - 1391 EP - 1394 PB - IEEE ER - TY - JOUR A1 - Eberspächer, Mark A. A1 - Bauer, Marius A1 - Eibert, Thomas F. T1 - Design and Analysis of an Isotropic Two-Dimensional Planer Composite Right/Left-Handed Waveguide Structure JF - Advances in Radio Science N2 - 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. Y1 - 2011 U6 - https://doi.org/10.5194/ars-9-73-2011 VL - 9 SP - 73 EP - 78 ER - TY - CHAP A1 - Eberspächer, Mark A. A1 - Eibert, Thomas F. T1 - Extraction of Embedded Dispersion Characteristics T2 - Asia Pacific Microwave Conference (APMC), Melbourne, Australien N2 - 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. Y1 - 2011 UR - https://ieeexplore.ieee.org/document/6173872 SP - 801 EP - 804 ER - TY - CHAP A1 - Eberspächer, Mark A. A1 - Eibert, Thomas F. T1 - A Narrow Via-free Composite Right/Left-Handed Leaky Wave Antenna with Low Cross-Polarization T2 - IEEE Antennas and Propagation International Symposium, Toronto, Kanada N2 - 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. Y1 - 2010 U6 - https://doi.org/10.1109/APS.2010.5561739 SP - 1 EP - 4 PB - IEEE ER - TY - CHAP A1 - Ott, Arndt T. A1 - Eberspächer, Mark A. A1 - Eibert, Thomas F. T1 - Ultra-Wideband Balun for Biconical Antenna Structures T2 - IEEE Antennas and Propagation International Symposium, Toronto, Kanada N2 - 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. Y1 - 2010 U6 - https://doi.org/10.1109/APS.2010.5562124 SP - 1 EP - 4 PB - IEEE ER - TY - CHAP A1 - Eibert, Thomas F. A1 - Eberspächer, Mark A. T1 - Treating Linear Antenna Arrays as Sampled Continuous Source Distributions T2 - URSI International Symposium on Electromagnetic Theory, Berlin, Deutschland N2 - 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. Y1 - 2010 U6 - https://doi.org/10.1109/URSI-EMTS.2010.5637265 SP - 707 EP - 710 PB - IEEE ER - TY - JOUR A1 - Eberspächer, Mark A. A1 - Eibert, Thomas F. T1 - Leaky wave antenna with amplitude controlled beam steering based on composite right/left-handed transmission lines JF - Advances in Radio Science N2 - 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. Y1 - 2010 U6 - https://doi.org/10.5194/ars-8-27-2010 SP - 27 EP - 32 ER - TY - CHAP A1 - Eberspächer, Mark A. A1 - Eibert, Thomas F. A1 - Russer, Peter T1 - An Analysis Procedure for 3D Metamaterial Unit Cells Based on the Rotated Transmission-Line Matrix Scheme T2 - Loughborough Antennas and Propagation Conference, Loughborough, Großbritannien N2 - A procedure is presented which enables, based on electromagnetic simulation, simple network parameter determination of three dimensional Composite Right/Left-Handed (CRLH) unit cells. The procedure is successfully applied to a three dimensional structure derived from the rotated transmission-line matrix (TLM) scheme. Based on the calculated element values a CRLH unit cell is optimized in order to realize a well balanced metamaterial structure. Y1 - 2010 U6 - https://doi.org/10.1109/LAPC.2010.5666239 SP - 161 EP - 164 PB - IEEE ER - TY - CHAP A1 - Tolani, Harshita A1 - Eberspächer, Mark A. A1 - Eibert, Thomas F. T1 - Composite Right/Left-Handed Leaky Wave Antenna with Structurally Non-Periodic Unit Cell Arrangement T2 - Loughborough Antennas and Propagation Conference, Loughborough, Großbritannien N2 - A unique dominant mode structurally non-periodic Composite Right/Left-Handed (CRLH) Transmission-Line (TL) based Leaky Wave Antenna (LWA) is proposed, with a novel kind of unit cell arrangement, which utilizes the additional degree of freedom obtained from non uniform spacing between the unit cells to control the radiation behavior of the antenna. We investigated the influence of non uniformly spaced unit cell arrangements on the radiation performance of the CRLH LWA and determined an optimum unit cell arrangement which leads to an improvement of 3 dB in side lobe level (SLL) suppression when compared to its structurally periodic counterpart for broadside direction. Furthermore, various aspects which are critical and should be taken into consideration while designing a structurally non-periodic LWA comprising of non uniformly spaced unit cell arrangement are also addressed. Y1 - 2010 U6 - https://doi.org/10.1109/LAPC.2010.5666240 SP - 165 EP - 168 PB - IEEE ER - TY - CHAP A1 - Eberspächer, Mark A. A1 - Eccleston, Kim A1 - Eibert, Thomas F. T1 - Realization of Via-free Microstrip Composite Right/Left-Handed Transmission Lines T2 - Proceedings of the German Microwave Conference, München, Deutschland N2 - Three via-free microstrip composite right/left handed (CRLH) unit cells are presented, which enable easy and low-cost fabrication of transmission lines exhibiting the infinite wave length phenomenon. All guiding structures are designed in an entirely printed circuit technology based on the transmission line theory and its equivalent circuit. Supported by EM simulation software the unit cells are optimized to operate at a frequency of 10 GHz. Appropriate experiment boards were fabricated and the measurements obtained from a microwave vector network analyzer are compared to the simulated results. Furthermore, an approach is worked out to determine the dispersion characteristics of the unit cells without the need of an equivalent circuit. The introduced and applied method allows to calculate dispersion relations directly based on simulated and measured ABCD parameters. Left and right-handed regions are pointed out by the dispersion diagram and the so-called infinite wavelength phenomenon is exhibited. Y1 - 2009 U6 - https://doi.org/10.1109/GEMIC.2009.4815867 SP - 1 EP - 4 PB - IEEE ER - TY - CHAP A1 - Liebgott, Florian A1 - Jandt, Marvin A1 - Eberspächer, Mark A. A1 - Liebgott, Annika A1 - Yang, Bin T1 - Spectrum-based online estimation of IQ imbalance for near field radar distance sensors T2 - 29th European Signal Processing Conference (EUSIPCO), Dublin, Irland N2 - A mismatch of the in-phase (I) and quadrature (Q) signal path of a direct-conversion receiver results in IQ imbalance, which distorts the demodulated signal. However, if the imbalance parameters can be estimated, the influence of the IQ imbalance can be compensated. We propose a novel method to estimate the parameters during normal operation of a stepped frequency continuous wave (SFCW) radar distance sensor without the need for a pilot signal. To estimate the imbalance parameters, we exploit the structure of the spectrum of the demodulated signal. Evaluating our method on real sensor data shows superior results especially for very short distances. Y1 - 2021 U6 - https://doi.org/10.23919/EUSIPCO54536.2021.9616359 ER - TY - CHAP A1 - Jandt, Marvin A1 - Eberspächer, Mark A. A1 - Kallfass, Ingmar T1 - Radar imaging based on multiple non-coherent antennas T2 - Proceedings of the SPIE, Florida, USA N2 - A concept for radar imaging based on multiple incoherent millimeter wave antennas is presented. The goal is to use 3D-Imaging, where the object moves along a line and passes a linear array of antennas. To reduce the hardware complexity, a novel radar principle is introduced, which does not require a coupling between TX and RX, but a reference reflector. The RX performs just a RF-power measurement for each frequency step in a SFCW setup. After preprocessing the raw data, any focusing algorithm can be used to obtain the 2D image. Multiple 2D images can be combined to 3D with backprojection. Y1 - 2021 U6 - https://doi.org/10.1117/12.2585568 ER - TY - CHAP A1 - Eberspächer, Mark A. A1 - Dorneich, Albert D. T1 - Level probing in highly overmoded waveguides T2 - Proceedings of the German Microwave Conference, Cottbus, Deutschland N2 - This paper deals with a tank level probing scenario using electromagnetic waves where the vessel supports a significant number of higher order modes which deteriorate the accuracy of the measurement. A signal model is presented which allows to estimate the accuracy of interferometric measurements taking higher order modes into account. Based on the predicted estimation an appropriate waveguide taper with a high suppression of parasitic modes is designed, fabricated and measured. The presented design approach is validated by measurements. Y1 - 2020 UR - https://ieeexplore.ieee.org/document/9080215 PB - IEEE ER - TY - CHAP A1 - Oladapo, Jeleel Alao A1 - Adrian, Simon B. A1 - Eberspächer, Mark A. T1 - Frequency-Dependent RCS Characterization of a CRLH-Based Leaky Wave Antenna T2 - 2024 Kleinheubach Conference Y1 - 2024 U6 - https://doi.org/10.23919/IEEECONF64570.2024.10739083 SP - 1 EP - 4 PB - IEEE ER - TY - JOUR A1 - Oladapo, Jeleel Alao A1 - Adrian, Simon B. A1 - Eberspächer, Mark A. T1 - Backscattering-Based Radiation Mode Analysis for Angle Estimation of a CRLH Leaky Wave Antenna JF - Advances in Radio Science N2 - Abstract. This study explores the extraction of the radiation mode field from backscattering field components of a composite right/left-handed (CRLH) leaky wave antenna (LWA) to estimate the relative angle to the radiation mode field within its frequency band of operation. Two methods, transmission line delay (TLD) and impedance loading (IL), for extracting the radiation mode from backscattering field components, are employed to isolate the radiation mode field of a CRLH LWA. In the IL method, backscattered fields are measured by terminating the CRLH LWA with short and open load impedances to express the radiation mode and structure mode field components. The TLD method uses a coaxial transmission line to connect the CRLH LWA to a high-gain X-band horn antenna, enabling isolation of the radiation mode field component from the backscattered field components, using time gating. This analysis employs two measurement setups for TLD, one in which both the CRLH LWA and the horn antenna rotate along the azimuth and the other in which only the CRLH LWA rotates. The analysis shows the frequency-angle relationship of the CRLH LWA radiation mode field, which reveals the frequency-dependent features of the CRLH LWA. Additionally, an evaluation of frequency ambiguity is done to provide more insights into the effectiveness of each approach for angle estimation of CRLH LWA relative to the incident wave. Y1 - 2025 U6 - https://doi.org/https://doi.org/10.5194/ars-23-59-2025 SN - 1684-9973 VL - 25 SP - 59 EP - 69 PB - Copernicus GmbH ER - TY - CHAP A1 - Oladapo, Jeleel Alao A1 - Adrian, Simon B. A1 - Daun, Marian A1 - Eberspächer, Mark A. T1 - Simulation-Based Frequency-Dependent RCS Estimation of a CRLH Leaky-Wave Antenna Using Gain and Impedance-Loading Methods T2 - 2025 9th International Conference on Computational System and Information Technology for Sustainable Solutions (CSITSS) Y1 - 2025 U6 - https://doi.org/10.1109/CSITSS67709.2025.11295030 SP - 1 EP - 6 PB - IEEE ER -