ABSTRACT Over-the-air performance testing of MIMO wireless devices requires the simulation of an ... more ABSTRACT Over-the-air performance testing of MIMO wireless devices requires the simulation of an RF environment similar to that experienced in the real world. There are a number of standardized spatial channel models that are considered acceptable for evaluating MIMO performance of LTE devices. A number of different methods have been proposed for generating MIMO test environments, but the ability of those methods to reproduce a target wireless channel, and the results they produce, vary. There are several methods for evaluating a spatial channel that are useful validation tools if the goal is to produce a specific known environment. This paper will present the results from several of those for different test cases. In addition, a set of reference device antenna systems have been developed to allow one MIMO radio to be tested with antennas designed for "good", "nominal", and "bad" performance. In this way, the ability of a MIMO test system to provide a relative distinction between different levels of device performance may be assessed. This paper will show results of this comparison for different system configurations and channel models and provide an indication of the suitability of these systems for evaluating MIMO device performance.
A three-dimensional finite-difference time-domain (FDTD) model is used to simulate basic GTEM to ... more A three-dimensional finite-difference time-domain (FDTD) model is used to simulate basic GTEM to OATS and GTEM to free space radiated emissions correlation algorithms. The GTEM models are terminated both with the typical resistor/foam absorber load, or alternately with a numerical absorbing boundary condition to simulate a perfectly-matched load. Radiation from dipole and loop antennas and a 19" dummy EUT is simulated in FDTD GTEM, OATS, and free space models. Comparison is shown of simulated and measured data for these same antennas and EUT fed by a comb generator. Very good agreement is shown between the measured and computed results. Several considerations regarding correlation algorithm application in one-port TEM waveguides are discussed
1999 IEEE International Symposium on Electromagnetic Compatability. Symposium Record (Cat. No.99CH36261), 1999
Log periodic dipole array (LPDA) antennas are one of the most widely used antenna types for norma... more Log periodic dipole array (LPDA) antennas are one of the most widely used antenna types for normalized site attenuation (NSA) and radiated emission (RE) testing. A thorough understanding of the possible error sources associated with the calibration and application of LPDAs for EMC tests over a ground plane is essential for evaluating and minimizing measurement uncertainties. Systematic errors are present
IEEE International Symposium on Electromagnetic Compatibility. Symposium Record (Cat. No.00CH37016), 2000
ABSTRACT A normalized site attenuation (NSA) measurement, made using LPDA free-space antenna fact... more ABSTRACT A normalized site attenuation (NSA) measurement, made using LPDA free-space antenna factors (AF) as specified in ANSI C63.4, has up to 3 dB of systematic errors due to limitations in the current theory. The ANSI model fails to account for the log periodic antenna's radiation pattern and its active phase center position, which were shown to be the dominant effects causing these errors. An enhanced theoretical model is introduced in this paper to take these two effects into account. In the enhanced model, antenna radiation patterns and active phase center positions are assumed to be unknown. At each frequency, the unknowns are solved by fitting the theoretical magnitude or phase response to a measured antenna response taken at different heights. The complex fit NSA (CFNSA) is then obtained by including the varied phase center and radiation pattern of the antennas under test. It is shown that the CFNSA model reduces the systematic errors in the current NSA to less than a dB
2003 IEEE Symposium on Electromagnetic Compatibility. Symposium Record (Cat. No.03CH37446), 2003
ABSTRACT Complex fit normalized site attenuation (CFNSA) is proposed as an improvement over the t... more ABSTRACT Complex fit normalized site attenuation (CFNSA) is proposed as an improvement over the theoretical model in ANSI C63.5. CFNSA accounts for phase center and antenna pattern variations for complex antennas, such as log periodic dipole arrays (LPDA) by solving for the pattern and phase center parameters using S21 at multiple heights. A recent study has shown that a simple antenna pattern such as cosnθ is insufficient to represent that of an LPDA above 500 MHz. This paper studies the feasibility of using a higher order analytical function to characterize the complex patterns of a LPDA. It investigates pattern formulations, which result in realistic antenna patterns with small number of unknowns.
IEEE 1991 International Symposium on Electromagnetic Compatibility, 1991
The results of preliminary measurements of the properties of two stripline transverse electromagn... more The results of preliminary measurements of the properties of two stripline transverse electromagnetic (TEM) cells are presented. The construction of the field cell is illustrated schematically. Measurements of emissions from a standard source made in a stripline TEM cell show good correlation with measurements of the same source made in a semi-anechoic chamber. The stripline TEM cell has several practical
Electrical resistivities of six single crystals of group-IV{ital B} transition-metal carbides are... more Electrical resistivities of six single crystals of group-IV{ital B} transition-metal carbides are reported for temperatures between 4 and 1000 K. Hall coefficients of the crystals are reported for temperatures to 350 K. The chemical analyses of the ratio of carbon-to-metal atoms in the crystals (0.89 to 0.99) were verified by an inverse linear relationship between the carbon-vacancy concentration and the
IEEE Antennas and Wireless Propagation Letters, 2000
ABSTRACT The radiated performance of a multiple-input–multiple-output (MIMO) antenna system is co... more ABSTRACT The radiated performance of a multiple-input–multiple-output (MIMO) antenna system is commonly evaluated based on a set of antenna-centric figures of merit (FoM). These generally include the antenna's total efficiency, branch imbalance, and magnitude of the complex (or envelope) correlation coefficient. On the other hand, to validate the over-the-air (OTA) performance of the MIMO system, including both antennas and other parts of the real transceivers, test methodologies were created based on a single FoM: the absolute data throughput. While an antenna-centric FoM provides a preliminary overall insights into the radiated performance of the MIMO antenna system, these FoMs are limited in their overall applicability. Each of these FoMs is based on far-field antenna measurements and assuming a uniform distribution of the incoming power, meaning that passive antenna measurements are made in single-input–single-output (SISO) anechoic chambers. Furthermore, without the implementation of channel models with controllable spatial characteristics, it is impossible to isolate the effect of polarization changes on MIMO performance. In this letter, the radiated performance of MIMO antenna systems will be compared in terms of data throughput using different channel models both with and without controllable cross-polarization ratio and other spatial characteristics.
ABSTRACT Over-the-air performance testing of MIMO wireless devices requires the simulation of an ... more ABSTRACT Over-the-air performance testing of MIMO wireless devices requires the simulation of an RF environment similar to that experienced in the real world. There are a number of standardized spatial channel models that are considered acceptable for evaluating MIMO performance of LTE devices. A number of different methods have been proposed for generating MIMO test environments, but the ability of those methods to reproduce a target wireless channel, and the results they produce, vary. There are several methods for evaluating a spatial channel that are useful validation tools if the goal is to produce a specific known environment. This paper will present the results from several of those for different test cases. In addition, a set of reference device antenna systems have been developed to allow one MIMO radio to be tested with antennas designed for "good", "nominal", and "bad" performance. In this way, the ability of a MIMO test system to provide a relative distinction between different levels of device performance may be assessed. This paper will show results of this comparison for different system configurations and channel models and provide an indication of the suitability of these systems for evaluating MIMO device performance.
A three-dimensional finite-difference time-domain (FDTD) model is used to simulate basic GTEM to ... more A three-dimensional finite-difference time-domain (FDTD) model is used to simulate basic GTEM to OATS and GTEM to free space radiated emissions correlation algorithms. The GTEM models are terminated both with the typical resistor/foam absorber load, or alternately with a numerical absorbing boundary condition to simulate a perfectly-matched load. Radiation from dipole and loop antennas and a 19" dummy EUT is simulated in FDTD GTEM, OATS, and free space models. Comparison is shown of simulated and measured data for these same antennas and EUT fed by a comb generator. Very good agreement is shown between the measured and computed results. Several considerations regarding correlation algorithm application in one-port TEM waveguides are discussed
1999 IEEE International Symposium on Electromagnetic Compatability. Symposium Record (Cat. No.99CH36261), 1999
Log periodic dipole array (LPDA) antennas are one of the most widely used antenna types for norma... more Log periodic dipole array (LPDA) antennas are one of the most widely used antenna types for normalized site attenuation (NSA) and radiated emission (RE) testing. A thorough understanding of the possible error sources associated with the calibration and application of LPDAs for EMC tests over a ground plane is essential for evaluating and minimizing measurement uncertainties. Systematic errors are present
IEEE International Symposium on Electromagnetic Compatibility. Symposium Record (Cat. No.00CH37016), 2000
ABSTRACT A normalized site attenuation (NSA) measurement, made using LPDA free-space antenna fact... more ABSTRACT A normalized site attenuation (NSA) measurement, made using LPDA free-space antenna factors (AF) as specified in ANSI C63.4, has up to 3 dB of systematic errors due to limitations in the current theory. The ANSI model fails to account for the log periodic antenna's radiation pattern and its active phase center position, which were shown to be the dominant effects causing these errors. An enhanced theoretical model is introduced in this paper to take these two effects into account. In the enhanced model, antenna radiation patterns and active phase center positions are assumed to be unknown. At each frequency, the unknowns are solved by fitting the theoretical magnitude or phase response to a measured antenna response taken at different heights. The complex fit NSA (CFNSA) is then obtained by including the varied phase center and radiation pattern of the antennas under test. It is shown that the CFNSA model reduces the systematic errors in the current NSA to less than a dB
2003 IEEE Symposium on Electromagnetic Compatibility. Symposium Record (Cat. No.03CH37446), 2003
ABSTRACT Complex fit normalized site attenuation (CFNSA) is proposed as an improvement over the t... more ABSTRACT Complex fit normalized site attenuation (CFNSA) is proposed as an improvement over the theoretical model in ANSI C63.5. CFNSA accounts for phase center and antenna pattern variations for complex antennas, such as log periodic dipole arrays (LPDA) by solving for the pattern and phase center parameters using S21 at multiple heights. A recent study has shown that a simple antenna pattern such as cosnθ is insufficient to represent that of an LPDA above 500 MHz. This paper studies the feasibility of using a higher order analytical function to characterize the complex patterns of a LPDA. It investigates pattern formulations, which result in realistic antenna patterns with small number of unknowns.
IEEE 1991 International Symposium on Electromagnetic Compatibility, 1991
The results of preliminary measurements of the properties of two stripline transverse electromagn... more The results of preliminary measurements of the properties of two stripline transverse electromagnetic (TEM) cells are presented. The construction of the field cell is illustrated schematically. Measurements of emissions from a standard source made in a stripline TEM cell show good correlation with measurements of the same source made in a semi-anechoic chamber. The stripline TEM cell has several practical
Electrical resistivities of six single crystals of group-IV{ital B} transition-metal carbides are... more Electrical resistivities of six single crystals of group-IV{ital B} transition-metal carbides are reported for temperatures between 4 and 1000 K. Hall coefficients of the crystals are reported for temperatures to 350 K. The chemical analyses of the ratio of carbon-to-metal atoms in the crystals (0.89 to 0.99) were verified by an inverse linear relationship between the carbon-vacancy concentration and the
IEEE Antennas and Wireless Propagation Letters, 2000
ABSTRACT The radiated performance of a multiple-input–multiple-output (MIMO) antenna system is co... more ABSTRACT The radiated performance of a multiple-input–multiple-output (MIMO) antenna system is commonly evaluated based on a set of antenna-centric figures of merit (FoM). These generally include the antenna's total efficiency, branch imbalance, and magnitude of the complex (or envelope) correlation coefficient. On the other hand, to validate the over-the-air (OTA) performance of the MIMO system, including both antennas and other parts of the real transceivers, test methodologies were created based on a single FoM: the absolute data throughput. While an antenna-centric FoM provides a preliminary overall insights into the radiated performance of the MIMO antenna system, these FoMs are limited in their overall applicability. Each of these FoMs is based on far-field antenna measurements and assuming a uniform distribution of the incoming power, meaning that passive antenna measurements are made in single-input–single-output (SISO) anechoic chambers. Furthermore, without the implementation of channel models with controllable spatial characteristics, it is impossible to isolate the effect of polarization changes on MIMO performance. In this letter, the radiated performance of MIMO antenna systems will be compared in terms of data throughput using different channel models both with and without controllable cross-polarization ratio and other spatial characteristics.
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Papers by M. Foegelle