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- Carlberg, Ulf, 1978
(author)
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Moment Method Analysis of Antennas in Reverberation Chambers and Cylindrical Structures
- 2004
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Licentiate thesis (other academic/artistic)abstract
- This thesis is a collection of papers using the method of moments for numerical analysis. The papers can be divided into two main groups; a study of antennas in reverberationchambers, and a study of antennas in cylindrical structures.The reverberation chamber is a metal cavity for measuring antennas and other devices. A numerical model of the reverberation chamber is developed to be able tobetter understand the field environment in the chamber and improve the performance of the chamber. The effect of lossy objects in the reverberation chamber is studied by calculating the mean absorption cross section of lossy objects and comparing it to measurements in a reverberation chamber. The possibility to extract electrical parametersof dielectric objects by measuring the mean absorption cross section is shown.The second part of the thesis deals with cylindrical structures. Many waveguide and antenna structures can be assumed to be infinitely long in one of the coordinates. It is then possible to efficiently solve a spectrum of two-dimensional problems rather than to solve the complete three-dimensional problem. The present thesis show solutionsfor modes in waveguides with various electromagnetic band-gap surfaces. Also it is shown how the field solutions for cylindrical structures can be interpolated over thespectral domain with the asymptotic waveform evaluation technique. There is also one paper analyzing a high-Q resonator on dielectric substrate by solving the onedimensional numerical Green's function for multi-layer planar structures.
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| 13. |
- Carlberg, Ulf, 1978
(author)
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Moment Method Analysis of Antennas in Reverberation Chambers and Cylindrical Structures
- 2006
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Doctoral thesis (other academic/artistic)abstract
- This thesis is a collection of papers using the method of moments for numerical analysis. The papers can be divided into two main groups; a study of antennas in reverberation chambers and a study of antennas in cylindrical structures.The reverberation chamber is a metal cavity for measuring antennas and other devices. A numerical model of the reverberation chamber is developed to be able to better understand the field environment in the chamber and improve the performance of the chamber. The effect of lossy objects in the reverberation chamber is studied by calculating the mean absorption cross section of lossy objects and comparing it to measurements in a reverberation chamber. The possibility to extract electrical parameters of dielectric objects by measuring the mean absorption cross section is shown.The second part of the thesis deals with cylindrical structures. Many waveguide and antenna structures can be assumed to be infinitely long in one of the coordinates. It is then possible to efficiently solve a spectrum of two-dimensional problems rather than to solve the complete three-dimensional problem. The present thesis shows solutions for modes in waveguides with various electromagnetic band-gap surfaces. Also it is shown how the field solutions for cylindrical structures can be interpolated over the spectral domain with the asymptotic waveform evaluation technique. There is also one paper analyzing a high-Q resonator on dielectric substrate by solving the one-dimensional numerical Green's function for multi-layer planar structures.
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- Carlberg, Ulf, 1978, et al.
(author)
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Numerical study of position stirring and frequency stirring in loaded reverberation chamber
- 2009
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In: IEEE Transactions on Electromagnetic Compatibility. - 0018-9375 .- 1558-187X. ; 51:1, s. pp. 12-17
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Journal article (peer-reviewed)abstract
- A numerical model of a loaded reverberation chamber is used to study the effectiveness of 3-D position stirring and frequency stirring. The numerical model is based on thin wires, the moment method, and a cavity Green's function. The average power transfer level between two dipole antennas is compared to the average power transfer level between a dipole antenna and a loop antenna. The two transmission levels should ideally be the same, as both the dipole and the loop are treated as being lossless and impedance matched. The standard deviation of the level differences is a measure of the accuracy of the chamber, and this is used to estimate the stirring effectiveness. It is shown that frequency stirring must be done over a larger bandwidth than the average mode bandwidth to be effective. The 3-D position stirring is also shown to be much more efficient than expected.
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| 21. |
- Carlberg, Ulf, 1978, et al.
(author)
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Ray based multipath simulation tool for studying convergence and estimating ergodic capacity and diversity gain for antennas with given far-field functions
- 2010
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In: 20th International Conference on Applied Electromagnetics and Communications, Dubrovnik, Croatia, September 2010. - 9789536037582
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Conference paper (peer-reviewed)abstract
- We propose that the rich isotropic multipath environment should be a reference environment for OTA (over-the-air) characterization of wireless stations for use in multipath, in the same way as the anechoic environment is a reference environment for antennas mounted on masts and rooftops. The rich isotropic multipath environment is emulated by a well designed reverberation chamber, but also by a spherical array of probes in an anechoic chamber. The present paper describes a ray-based simulation tool, ViRM-Lab, which enables users to study the performance of arbitrary user-defined multiport antenna located in user-specified multipath environment. The antennas are defined by their far-field functions of the embedded element (with the other ports matched-load terminated). The environment can be determined by its Angle-of-Arrival (AoA) distribution, richness, and polarization balance. The code is made in such a way that the convergence of the cumulative distribution function (CDF) received on all ports can be studied, as well as the convergence of the statistical expectations when estimating the ergodic Shannon capacity and diversity gain.
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- Carlsson, Jan, 1962, et al.
(author)
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About measurements in reverberation chamber and isotropic reference environment
- 2010
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In: 20th International Conference on Applied Electromagnetics and Communications, Dubrovnik, Croatia, September 2010. - : ICECom 2010. - 9789536037582
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Conference paper (peer-reviewed)abstract
- The paper discusses the need for a reference environment for the characterization of small antennas intended to be used in multipath. The conclusion is that a good choice is the rich isotropic multipath environment as emulated by a well designed reverberation chamber, or possibly by a spherical array of antennas in an anechoic chamber. This is the only environment that enables a unique, objective and repeatable antenna characterization. This cannot be achieved in other environments. A few examples are given showing that the performances of different incremental antennas are very different and depend strongly on their orientations when they are located in a 2D horizontal multipath environment, with incident waves only in the horizontal plane, whereas their performances are equal and invariant to orientation when they are located in the rich isotropic multipath environment.
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| 25. |
- Carlsson, Jan, 1962, et al.
(author)
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Diversity Gains in Random Line-Of-Sight and Rich Isotropic Multipath Environment
- 2012
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In: 2012 Loughborough Antennas & Propagation Conference (LAPC), Lough-borough, England, 12-13 Nov., 2012. - 9781467322195
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Conference paper (peer-reviewed)abstract
- Antenna diversity gain for theoretical as well as measured antennas is studied in two extreme environments, the rich isotropic multipath environment (RIMP) and the random line-of-sight environment. The RIMP diversity gain was previously defined based on improved fading performance, here we equivalently consider it as a metric for the cumulative improvement of the 1% worst users randomly distributed in the RIMP environment. Similarly, we consider the diversity gain in the random line-of-sight environment to be the performance improvement of the 1% of the users which receives the weakest signal relative to a theoretical Rayleigh distribution of the signal levels among the users. The random line-of-sight environment is regarded as being caused by the statistics of an ensemble of users (or terminals) with arbitrary 3D orientations.
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| 26. |
- Carlsson, Jan, et al.
(author)
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Diversity gains in random line of sight and rich isotropic multipath environment
- 2012
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In: LAPC 2012 - 2012 Loughborough Antennas and Propagation Conference.
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Conference paper (peer-reviewed)abstract
- Antenna diversity gain for theoretical as well as measured antennas is studied in two extreme environments, the rich isotropic multipath environment (RIMP) and the random line-of-sight environment. The RIMP diversity gain was previously defined based on improved fading performance, here we equivalently consider it as a metric for the cumulative improvement of the 1% worst users randomly distributed in the RIMP environment. Similarly, we consider the diversity gain in the random line-of-sight environment to be the performance improvement of the 1% of the users which receives the weakest signal relative to a theoretical Rayleigh distribution of the signal levels among the users. The random line-of-sight environment is regarded as being caused by the statistics of an ensemble of users (or terminals) with arbitrary 3D orientations. © 2012 IEEE.
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| 27. |
- Condo Neira, Edith, 1979, et al.
(author)
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Evaluation of V2X Antenna Performance Using a Multipath Simulation Tool
- 2014
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In: Antennas and Propagation (EuCAP), Proceedings of the 8th European Conference, The Hague, The Netherlands, Apr. 2014. - 9788890701849 ; , s. 2534-+, s. 2534-2538
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Conference paper (peer-reviewed)abstract
- Antennas are one of the key components for efficient and reliable vehicular communications systems; especially for safety related applications the antenna performance is crucial. It is therefore important to be able to evaluate the antenna performance under realistic conditions so that the best antenna solution can be selected. In this paper we present a statistical method for evaluating the antenna performance by using the antennas radiation patterns and a multipath simulation tool. The multipath environment is generated by a number of incident waves with a specific angle of arrival distribution, defined by the user. In order to generate voltage samples at the antenna ports many sets of incident waves are generated. This simulates a changing environment as, e.g., when the vehicle is moving. By studying the cumulative distribution functions (CDFs) for the voltage samples we are able to compare the performance for different antenna types, positions on the vehicle, etc. The method is fast and effective and, when applied to typical vehicular propagation environments, the importance of having antennas with radiation patterns capable of covering the whole azimuth plane is demonstrated.
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| 29. |
- Hussain, Ahmed, 1985, et al.
(author)
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About Random LOS in Rician Fading Channels for MIMO OTA Tests
- 2011
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In: ISAP2011, Jeju, Korea, 15-18 October 2011.
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Conference paper (peer-reviewed)abstract
- It is often claimed that Rician fading must also be included for Over-The-Air (OTA) testing of mobile devices with Multiple-input Multiple-output (MIMO) capabilities. However, the Line-Of-Sight (LOS) component varies with orientation and location of the mobile device. Therefore, we study Rician channels with random LOS to determine its significance
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| 30. |
- Hussain, Ahmed, 1985, et al.
(author)
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Analysis of statistical uncertainties involved in estimating ergodic MIMO capacity and diversity gain in Rayleigh fading environment
- 2010
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In: 20th International Conference on Applied Electromagnetics and Communications, Dubrovnik, Croatia, September 2010. - : ICECom 2010. - 9789536037582
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Conference paper (peer-reviewed)abstract
- Statistical uncertainties involved in the evaluation of ergodic MIMO capacity and diversity gain in a fading environment is investigated. The study is based on results from a numerical simulation tool called "Rayleigh-Lab. " This tool can be used for accuracy investigation of MIMO capacity and diversity gain, and to determine the number of independent samples needed to estimate them with a reasonable level of confidence. The MIMO capacity is evaluated using Shannon's channel capacity formula. Two different methods of evaluating diversity gains are compared: based on CDF curves, and based on estimating correlation and radiation efficiency and then using them in a newly available compact formula for calculating the diversity gain. Rayleigh-Lab emulates Rayleigh channels by generating sequences of random complex numbers and it provides a convenient graphical user-interface for a pedagogical study of average power level (proportional to antenna efficiency), correlation, diversity gain and maximum available capacity.
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| 31. |
- Hussain, Ahmed, 1985, et al.
(author)
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Correlation between far-field patterns on both sides of the head of two-port antenna on mobile terminal
- 2013
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In: ISAP 2013 - Proceedings of the 2013 International Symposium on Antennas and Propagation.. - 9787564142797 ; , s. 288-289
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Conference paper (peer-reviewed)abstract
- We present an electromagnetic simulation of a practical mobile terminal with a two-port MIMO antenna on left and right sides of the head. The computed far-field patterns include the effect of head and hand phantoms. We show that the far-field patterns on the two sides are strongly correlated if they are presented in the coordinate system of the phone, but they are completely uncorrelated in the coordinate system of the environment.
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| 32. |
- Hussain, Ahmed, 1985, et al.
(author)
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Diversity gains of multiport mobile terminals in multipath for talk positions on both sides of the head
- 2013
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In: 7th European Conference on Antennas and Propagation, EuCAP 2013. - 2164-3342. - 9788890701832 ; , s. 863-866
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Conference paper (peer-reviewed)abstract
- The paper studies the over-the-air (OTA) performance of a mobile terminal. A practical two-port mobile terminal model on the left side and the right side of the head for both standard cheek position and standard tilt position is used to study the diversity gains. The diversity gain has been determined by measurements in a reverberation chamber as well as by simulations using the far field patterns from CST Microwave Studio, and then exposing these patterns to rich isotropic multipath (RIMP) environment in a ray-based simulation tool.
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| 37. |
- Kildal, Per-Simon, 1951, et al.
(author)
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Designing reverberation chambers for measurements of small antennas and wireless terminals: accuracy, frequency resolution, lowest frequency of operation, loading and shielding of chamber
- 2006
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In: First European Conference on Antennas and Propagation (EuCAP), 2006, Nice, France, 6 - 10 November 2006.
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Conference paper (peer-reviewed)
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| 38. |
- Kildal, Per-Simon, 1951, et al.
(author)
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MIMO LTE OTA measurements in reverberation chamber: rich isotropic reference environment makes agreement with theoretical system model
- 2012
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In: Proceedings of 6th European Conference on Antennas and Propagation, EuCAP 2012. Prague, 26-30 March 2012. - 9781457709180 ; , s. 1536-1539
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Conference paper (peer-reviewed)abstract
- The reverberation chamber has during the last 10 years been developed into an accurate instrument for OTA measurements, having a well-defined rich isotropic multipath environment. This has been introduced as a new reference environment for testing of wireless devices, complementing the traditional anechoic reference environment. The rich isotropic multipath environment and the definition of an ideal error-correcting digital receiver have made it possible to develop simple theoretical models that predict the measured throughput data rate in a reverberation chamber versus received power within a few tenth of dBs The present paper overviews the developments of the reverberation chamber that has made it possible to achieve such agreement, as well as the on-going work of determining relevance of the rich isotropic environment compared to real-life environments.
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| 41. |
- Orlenius, Charlie, 1976, et al.
(author)
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Investigation of heavily loaded reverberation chamber for testing of wideband wireless units
- 2006
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In: IEEE AP-S International Symposium, Albuquerque, N.M., July 2006. ; , s. 3569-3572
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Conference paper (peer-reviewed)abstract
- Traditionally, the reverberation chamber has been used as a low-loss cavity to gain high signal levels. For testing of the radiated properties of wireless terminals and their antennas, this is not an issue, and lossy objects like for instance a head phantom can be introduced in the chamber without problem. However, for testing of active units, the bandwidth of the system itself plays an important role. In order to avoid distortion of the signal transmitted in the chamber, the bandwidth of the chamber must be larger than the bandwidth of the signal. This is one reason for loading the reverberation chamber. Another reason is a potential increase in the measurement accuracy, since an increased bandwidth makes more modes excited at a particular frequency. The purpose of this paper is to investigate the effect of loading on the statistics of the chamber and its bandwidth
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| 44. |
- Yang, Jian, 1960, et al.
(author)
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A Fast Mode Analysis for Waveguides of Arbitrary Cross Section With Multiple Regions by Using a Spectrum of Two-Dimensional Solutions and Asymptotic Waveform Evaluation
- 2004
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In: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 52:6, s. 1615-1621
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Journal article (peer-reviewed)abstract
- A fast mode analysis for waveguides of arbitrary cross section with multiple regions is presented in this paper. The analysis is based on a spectrum of two-dimensional (2-D) solutions with application of asymptotic waveform evaluation, which requires only several 2-D solutions in searching for the propagation modes and calculating the field distribution of the modes in waveguides. The boundaries of waveguides can be modeled by perfect electric conductors, perfect magnetic conductors, dielectric materials, and asymptotic strip boundary conditions. By this modeling, one can also analyze the waveguides with the soft and hard surfaces. The method is excitation dependent, which provides a tool to analyze the response of different modes to different excitations. No existence of spurious modes is experienced by using this method. The verification and comparison of the numerical results with analytical, published data, and measurements are also presented in this paper.
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