Showing papers by "Per-Simon Kildal published in 2002"

Definition of effective diversity gain and how to measure it 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

Detection of a polarization imbalance in reverberation chambers and how to remove it by polarization stirring when measuring antenna efficiencies

Abstract: It has previously been shown that the radiation efficiency of small antennas can be measured with good accuracy in reverberation chambers. The results are obtained by averaging several measurements of the transmitted power between the antenna under test and a fixed antenna, both located inside the chamber. Further investigations have shown that the results depend strongly on the orientation of the antenna under test and thereby on its polarization. The present Letter explains why it is like this, and how this imbalance can be removed by polarization stirring, that is, by using three orthogonal fixed antennas instead of one. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 145–149, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10398

Measurement of free-space impedances of small antennas in reverberation chambers

Abstract: We have recently shown that reverberation chambers can be used to measure the radiation efficiency of antennas for wireless and mobile terminals. In the present paper, we show that it is possible, in the same measurement setup, to measure the input impedance of the antenna as would be seen when the antenna radiates in free space. If the antenna is located close to, e.g., a head phantom inside the chamber, we will measure the impedance of the antenna as it would be seen if the dipole and the phantom were located in free space with the same location and orientation relative to each other. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 112–115, 2002.

Calculation of Self Impedance and Radiation Efficiency of a Dipole near a Lossy Cylinder with Arbitrary Cross Section by Using the Moment Method and a Spectrum of Two-dimensional Solutions

Abstract: We present a computation method for the self-impedance and radiation efficiency of a dipole near a lossy dielectric cylinder with arbitrary cross section by using a spectrum of two-dimensional (2-D) solutions. The 2-D solutions for the spectral Green's functions of the cylinder as well as the 3-D solution for the current on the dipole are found by the method of moments (MoM). The 2-D MoM approach makes use of the algorithm G2DMULT (Green's function of 2-D multiregion structures). The geometry of a dipole near a lossy circular dielectric cylinder is, in a parallel work, used to validate a reverberation chamber for measuring the radiation efficiency and self-impedance of small antennas. Therefore, the results in the present paper could be verified against results from other numerical programs and from measurements in both an anechoic chamber and a reverberation chamber. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 108–112, 2002.

Presentation of the spectral electric and magnetic field integral equations used in G2DMULT for analyzing cylindrical structures of multimaterial regions

Abstract: When dealing with electromagnetic problems of three-dimensional (3D) elements, such as dipoles, microstrip patches, and slots, in the vicinity of two-dimensional (2D) structures, it is very efficient to find the radiation characteristics of the 3D elements and the mutual couplings between them by using a spectrum of 2D solutions (S2DS). G2DMULT is a general algorithm that applies the S2DS technique to calculate the spectral Green's functions of 2D multiregion structures by using the method of moments (MoM). When these spectral Green's functions are used, the spectral electric and magnetic field integral equations (EFIE and MFIE) are needed to solve the 2D problems in the spectral domain. This Letter presents the spectral electric and magnetic field integral equations (EFIE and MFIE), their moment-method solution formulations, and the special expressions needed to handle the discontinuity of some field components at the material boundaries. Several numerical examples show that G2DMULT with these spectral EFIEs and MFIEs can provide accurate results compared with measurements. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 88–93, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10382

Influence of hard corrugated PBG wall design on performance of conical horn antenna

Abstract: Some numerical results for a conical horn with three modifications of a hard corrugated PBG wall are presented. It is shown that a completely corrugated horn of diameter 4–5 wavelengths provides 80–87% aperture efficiency and a cross-polar level below −30 dB for a horn length greater than 20 wavelengths. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 265–268, 2002.

Measurements of mobile phone antennas in small reverberation chambers

Abstract: The paper gives a summary of the work that have been performed in the Antenna group at Chalmers University of Technology on measuring antennas for mobile phones in reverberation chambers. Reverberation chambers were originally developed for EMC measurements. We have shown that it also can be used to measure performance of antennas that are designed for use in multipath propagation environment, as well as the performance of complete phones. The antennas and phones can be measured with or without the presence of a head phantom or other objects. The antenna measurements give both radiation efficiency and reflection coefficient at different positions relative to an object such as a head phantom, as they would appear if the antenna and the head phantom were located in free space. The phone measurements give the total radiated power, which we refer to as the telephone communication power (TCP), also at different positions relative to an object. The present summary includes results from both antenna and phone measurements.

Actual diversity gain measured in the reverberation chamber

Abstract: In this paper, we introduce the actual diversity gain measured in the reverberation chamber. The experiments have been made with two dipoles with a lossy cylinder. The interesting frequency range was between 869 and 894 MHz. Actual diversity gain of two dipoles for selection and maximum ratio combining shows the significant improvement comparing to one dipole.

Performance of mobile phones located in the vicinity of the human body measured in reverberation chamber

Abstract: Performance of mobile phones located in the vicinity of the human body measured in reverberation chamber

Accurate measurements of small antennas and radiation from mobile phones in reverberation chambers

Abstract: The paper gives a summary of the work that has been performed in the Antenna group at Chalmers University of Technology and the start -up company Bluetest AB (www.bluetest.se) on measuring radiated power from mobile phones in reverberation chambers. Reverberation chambers were originally developed for EMC measurements. We have shown that it also can be used to accurately measure performance of antennas that are designed for use in multipath propagation environment, as well as the total radiated power of complete phones. The antennas and phones can be measured with or without the presence of a head phantom or other objects. In the present paper we describe the measurements of the total radiated power and provide results for phones with different types of antennas. We will also show results of validation against measurements of the total radiated power by integration of three-dimensional far field patterns measured in anechoic chambers.