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Author

Kent Rosengren

Bio: Kent Rosengren is an academic researcher from Flextronics. The author has contributed to research in topics: Electromagnetic reverberation chamber & Antenna efficiency. The author has an hindex of 11, co-authored 22 publications receiving 1625 citations.

Papers
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Journal ArticleDOI
TL;DR: This work explains how MIMO and diversity antennas with mutual coupling can be analyzed by classical embedded element patterns that can be computed by standard computer codes and how the radiation efficiency, diversity gain, correlation, and channel capacity can be measured in a reverberation chamber.
Abstract: MIMO systems are characterized by their maximum available capacity, which is reduced if there is correlation between the signals on different channels. The correlation is primarily caused by mutual coupling between the elements of the antenna arrays on both the receiving and transmitting sides. Similarly, diversity antennas can be characterized by a diversity gain that also is affected by mutual coupling between the antennas. We explain how such MIMO and diversity antennas with mutual coupling can be analyzed by classical embedded element patterns that can be computed by standard computer codes. In the MIMO example under investigation, the mutual coupling reduces both correlation, which increases the capacity, and radiation efficiency, which decreases it, and the combined effect is a net capacity reduction. We also explain how the radiation efficiency, diversity gain, correlation, and channel capacity can be measured in a reverberation chamber. The measurements show good agreement with simulations.

588 citations

Journal ArticleDOI
04 Apr 2005
TL;DR: In this article, a six-monopole circular antenna array for use in a MIMO system is considered and the authors show how to calculate the embedded element patterns, both by classical analytical modeling and by the method of moments.
Abstract: A six-monopole circular antenna array for use in a MIMO system is considered. The authors show how to calculate the embedded element patterns, both by classical analytical modeling and by the method of moments. Thereafter, these are used to calculate the radiation efficiency of each embedded element, correlation and diversity gain, as well as the maximum average capacity of the MIMO system when the array is located in a rich scattering environment. The theoretical value for the capacity is obtained by numerically distributing many plane wave sources statistically uniformly over 4/spl pi/, letting them illuminate the calculated embedded element pattern and using Shannon's capacity formula on the received wave amplitudes. The calculated results are compared with measurement in a reverberation chamber, representing a similar scattering environment. The agreement is good.

353 citations

Journal ArticleDOI
TL;DR: In this article, the authors show that the measurement accuracy can be significantly improved by rotating the antenna under test, which is referred to as platform stirring, and demonstrate in the 900 MHz GSM band by measurements in a reverberation chamber of dimensions 1.0 m×0.8 m×1.0m.
Abstract: It has been demonstrated that the radiation efficiency of antennas can be measured in reverberation chambers. The measurement accuracy is known to be better the larger the size. The present paper shows that the measurement accuracy can be significantly improved by rotating the antenna under test. This is demonstrated in the 900 MHz GSM band by measurements in a reverberation chamber of dimensions 1.0 m×0.8 m×1.0 m. We refer to this new stirring method as platform stirring. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 391–397, 2001.

180 citations

Journal ArticleDOI
TL;DR: In this paper, the authors defined an effective diversity gain, which is an absolute measure of diversity gain and can therefore be used to compare different diversity antennas, and also showed how the effective diversity gains can be measured in a reverberation chamber.
Abstract: The performance of cellular phones and other mobile or wireless terminals operating in multipath propagation environment can be greatly improved by introducing different diversity schemes. The improvement is characterized in terms of a diversity gain. An effective diversity gain is defined here. This is an absolute measure of diversity gain and can therefore be used to compare different diversity antennas. The Letter also shows how the effective diversity gain can be measured in a reverberation chamber. Measured effective diversity gains agree much better with theoretical diversity gains than measured values published previously. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 56–59, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10372

168 citations

Journal ArticleDOI
TL;DR: In this paper, the radiation efficiency, effective diversity gain, and apparent diversity gain of two parallel dipoles and how they depend on dipole spacing were calculated. But the results for 50 /spl Omega/ termination were verified by measurements of effective diversity in a reverberation chamber.
Abstract: Two parallel dipoles are often used as a reference case for measuring diversity gain. The present paper shows how to calculate the radiation efficiency, effective diversity gain, and apparent diversity gain of two parallel dipoles and how they depend on dipole spacing. We treat several cases for different terminations of the neighboring dipole; open-circuited, short-circuited, and 50 /spl Omega/ termination. The results for 50 /spl Omega/ termination are verified by measurements of effective diversity gain in a reverberation chamber.

142 citations


Cited by
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Journal ArticleDOI
TL;DR: This work explains how MIMO and diversity antennas with mutual coupling can be analyzed by classical embedded element patterns that can be computed by standard computer codes and how the radiation efficiency, diversity gain, correlation, and channel capacity can be measured in a reverberation chamber.
Abstract: MIMO systems are characterized by their maximum available capacity, which is reduced if there is correlation between the signals on different channels. The correlation is primarily caused by mutual coupling between the elements of the antenna arrays on both the receiving and transmitting sides. Similarly, diversity antennas can be characterized by a diversity gain that also is affected by mutual coupling between the antennas. We explain how such MIMO and diversity antennas with mutual coupling can be analyzed by classical embedded element patterns that can be computed by standard computer codes. In the MIMO example under investigation, the mutual coupling reduces both correlation, which increases the capacity, and radiation efficiency, which decreases it, and the combined effect is a net capacity reduction. We also explain how the radiation efficiency, diversity gain, correlation, and channel capacity can be measured in a reverberation chamber. The measurements show good agreement with simulations.

588 citations

Journal ArticleDOI
TL;DR: Several solutions are presented to reduce the mutual coupling between two planar inverted-F antennas working in close radiocommunication standards and positioned on a finite-sized ground plane modeling the printed circuit board (PCB) of a typical mobile phone.
Abstract: Several solutions are presented to reduce the mutual coupling between two planar inverted-F antennas (PIFAs) working in close radiocommunication standards and positioned on a finite-sized ground plane modeling the printed circuit board (PCB) of a typical mobile phone. First, the two PIFAs are designed on separate PCBs to, respectively, operate in the DCS1800 and UMTS bands. In a second step, they are associated on the top edge of the same PCB. Realistic arrangements are then theoretically and experimentally studied. Finally, several solutions are investigated to maximize the isolation. They consist in inserting a suspended line between the PIFAs' feedings and/or shorting points. All along this paper, several prototypes are fabricated and their performances measured to validate the obtained IE3D moment method-based simulation results

530 citations

Journal ArticleDOI
TL;DR: In this article, the proposed 2D and 3D electrical and magnetic-based EZ antennas are shown to be naturally matched to a 50 source, i.e., without the introduction of a matching network.
Abstract: Planar two-dimensional (2D) and volumetric three-dimensional (3D) metamaterial-inspired efficient electrically-small antennas that are easy to design; are easy and inexpensive to build; and are easy to test; are reported, i.e., the EZ antenna systems. The proposed 2D and 3D electrical- and magnetic-based EZ antennas are shown to be naturally matched to a 50 source, i.e., without the introduction of a matching network. It is demonstrated numerically that these EZ antennas have high radiation efficiencies with very good impedance matching between the source and the antenna and, hence, that they have high overall efficiencies. The reported 2D and 3D EZ antenna designs are linearly scalable to a wide range of frequencies and yet maintain their easy-to-build characteristics. Several versions of the 2D EZ antennas were fabricated and tested. The measurement results confirm the performance predictions. The EZ antennas systems may provide attractive alternatives to existing electrically-small antennas.

430 citations

Journal ArticleDOI
TL;DR: In this article, the authors discuss how a reverberation chamber can be used to simulate a controllable Rician radio environment for the testing of a wireless device, and they present both a one-and a two-antenna test configuration approach.
Abstract: With the proliferation of wireless devices in recent years, there is a growing need to test the operation and functionality of these various devices in different multipath environments, ranging from line-of-sight environment to a pure Rayleigh environment. In this paper we discuss how a reverberation chamber can be used to simulate a controllable Rician radio environment for the testing of a wireless device. We show that by varying the characteristics of the reverberation chamber and/or the antenna configurations in the chamber, any desired Rician K-factor can be obtained. Expressions for the desired K-factor as a function of the chamber and antenna characteristics will be presented. Experimental results are presented to illustrate the validity of these expressions, to show how the reverberation chamber can be used to simulate different multipath environments, and to show the realization of a controlled K-factor test facility. We present both a one-antenna and a two-antenna test configuration approach

378 citations

Journal ArticleDOI
04 Apr 2005
TL;DR: In this article, a six-monopole circular antenna array for use in a MIMO system is considered and the authors show how to calculate the embedded element patterns, both by classical analytical modeling and by the method of moments.
Abstract: A six-monopole circular antenna array for use in a MIMO system is considered. The authors show how to calculate the embedded element patterns, both by classical analytical modeling and by the method of moments. Thereafter, these are used to calculate the radiation efficiency of each embedded element, correlation and diversity gain, as well as the maximum average capacity of the MIMO system when the array is located in a rich scattering environment. The theoretical value for the capacity is obtained by numerically distributing many plane wave sources statistically uniformly over 4/spl pi/, letting them illuminate the calculated embedded element pattern and using Shannon's capacity formula on the received wave amplitudes. The calculated results are compared with measurement in a reverberation chamber, representing a similar scattering environment. The agreement is good.

353 citations