The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Jennifer T. Bernhard - One of the best experts on this subject based on the ideXlab platform.
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Reconfigurable Null Scanning Antenna With Three Dimensional Null Steer
IEEE Transactions on Antennas and Propagation, 2013Co-Authors: Yong Siwen, Jennifer T. BernhardAbstract:A reconfigurable null scanning antenna (RNSA) capable of continuous null steering in three-dimensional space is presented. This compact antenna maintains its Common Impedance bandwidth through the careful combination of resonances of both the driven and parasitic patches, and the incorporation of 12 varactors enables continuous null steer. Full wave simulations predict antenna performance, whereas Impedance and pattern measurements validate simulated results.
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Design of a MIMO dielectric resonator antenna for LTE femtocell base stations
IEEE Transactions on Antennas and Propagation, 2012Co-Authors: Jie-bang Yan, Jennifer T. BernhardAbstract:A novel multiple-input multiple-output ({MIMO)} dielectric resonator antenna ({DRA)} for long term evolution ({LTE)} femtocell base stations is described. The proposed antenna is able to transmit and receive information independently using {TE} and {HE} modes in the {LTE} bands 12 (698-716 {MHz}, 728-746 {MHz)} and 17 (704-716 {MHz}, 734-746 {MHz).} A systematic design method based on perturbation theory is proposed to induce mode degeneration for {MIMO} operation. Through perturbing the boundary of the {DRA}, the amount of energy stored by a specific mode is changed as well as the resonant frequency of that mode. Hence, by introducing an adequate boundary perturbation, the {TE} and {HE} modes of the {DRA} will resonate at the same frequency and share a Common Impedance bandwidth. The simulated mutual coupling between the modes was as low as - 40 {dB} . It was estimated that in a rich scattering environment with an Signal-to-Noise Ratio ({SNR)} of 20 {dB} per receiver branch, the proposed {MIMO} {DRA} was able to achieve a channel capacity of 11.1 {b/s/Hz} (as compared to theoretical maximum 2 × 2 capacity of 13.4 {b/s/Hz).} Our experimental measurements successfully demonstrated the design methodology proposed in this work.
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A comparative study of diversity gain and spatial coverage: Fixed versus reconfigurable antennas for portable devices
Microwave and Optical Technology Letters, 2007Co-Authors: T.l. Roach, Gregory H. Huff, Jennifer T. BernhardAbstract:This study investigates the performance of planar fixed and/or pattern reconfigurable antennas on a model laptop in terms of diversity gain and spatial coverage. The reconfigurable antenna used in this work has the ability to change its radiation pattern from endfire to broadside while operating over a Common Impedance bandwidth. The research combines diversity gain and spatial coverage into a single parameter that takes into account the effects of both simultaneously. Experimental data, including the resulting diversity gain and spatial coverage calculations, are presented. This work reveals the possibilities and importance of using reconfigurable radiation antennas and weighs their potential impact on high performance wireless systems. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 535–539, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22181
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AHS - On the Applications for a Radiation Reconfigurable Antenna
Second NASA ESA Conference on Adaptive Hardware and Systems (AHS 2007), 2007Co-Authors: T.l. Roach, Gregory H. Huff, Jennifer T. BernhardAbstract:In this work, applications involving a radiation reconfigurable antenna are presented and discussed. The antenna is capable of reconfiguring its radiation pattern from broadside to endfire over a Common Impedance bandwidth. After outlining the operation and radiation behavior of the single element its use in multiple antenna systems, such as multiple input-multiple output (MIMO) and diversity systems, is described. Recent results using the antenna in both one-dimensional and two-dimensional planar arrays setting are also included. These examples illustrate the potential benefits and impact that pattern reconfigurable antennas can have in diverse kinds of wireless communications networks.
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Enabling High Performance Wireless Communication Systems Using Reconfigurable Antennas
MILCOM 2006, 2006Co-Authors: T.l. Roach, Gregory H. Huff, Jennifer T. BernhardAbstract:The use of multiple antenna systems (MIMO, etc.) and signal combining techniques (Maximal Ratio, Spatial, etc.) can create significant advantages in situations requiring a high degree of system agility. Furthermore, the ability to resolve coherent information channels in the context of electrically hostile environments (e.g., noise or jamming sources and complex scattering and/or multi-path environments) can be of significant importance in both logistic and battlefield environments. This work focuses on the combination of radiation reconfigurable antennas and signal processing techniques, focusing on their applications in advanced wireless communication systems and mobile or ad hoc networks. Experimental data demonstrating these concepts will be provided for a canonical structure capable of integrating multiple reconfigurable radiation antennas that have been designed to switch between broadside and endfire radiation characteristics (operating over a Common Impedance bandwidth). This work reveals both the possibilities and the importance of using reconfigurable radiation antennas, and gauges the potential impact on applications requiring a high degree of performance from the radiating structure(s).
Gregory H. Huff - One of the best experts on this subject based on the ideXlab platform.
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A comparative study of diversity gain and spatial coverage: Fixed versus reconfigurable antennas for portable devices
Microwave and Optical Technology Letters, 2007Co-Authors: T.l. Roach, Gregory H. Huff, Jennifer T. BernhardAbstract:This study investigates the performance of planar fixed and/or pattern reconfigurable antennas on a model laptop in terms of diversity gain and spatial coverage. The reconfigurable antenna used in this work has the ability to change its radiation pattern from endfire to broadside while operating over a Common Impedance bandwidth. The research combines diversity gain and spatial coverage into a single parameter that takes into account the effects of both simultaneously. Experimental data, including the resulting diversity gain and spatial coverage calculations, are presented. This work reveals the possibilities and importance of using reconfigurable radiation antennas and weighs their potential impact on high performance wireless systems. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 535–539, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22181
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AHS - On the Applications for a Radiation Reconfigurable Antenna
Second NASA ESA Conference on Adaptive Hardware and Systems (AHS 2007), 2007Co-Authors: T.l. Roach, Gregory H. Huff, Jennifer T. BernhardAbstract:In this work, applications involving a radiation reconfigurable antenna are presented and discussed. The antenna is capable of reconfiguring its radiation pattern from broadside to endfire over a Common Impedance bandwidth. After outlining the operation and radiation behavior of the single element its use in multiple antenna systems, such as multiple input-multiple output (MIMO) and diversity systems, is described. Recent results using the antenna in both one-dimensional and two-dimensional planar arrays setting are also included. These examples illustrate the potential benefits and impact that pattern reconfigurable antennas can have in diverse kinds of wireless communications networks.
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integration of packaged rf mems switches with radiation pattern reconfigurable square spiral microstrip antennas
IEEE Transactions on Antennas and Propagation, 2006Co-Authors: Gregory H. Huff, Jennifer Truman BernhardAbstract:This work describes the integration of commercially available packaged radio frequency microelectromechanical system (RF MEMS) switches with radiation pattern reconfigurable microstrip antennas. Most applications of RF MEMS switches consider the switches as only circuit elements. In contrast, the implementation of packaged switches in this particular antenna must address not only the simple open/closed behavior of the switches but also their impact on the radiation characteristics of the reconfigurable antenna. Here, two Radant MEMS single-pole single throw (SPST) SPST-RMSW100 (packaged RF MEMS) switches are used to reconfigure the radiation patterns of a resonant square spiral microstrip antenna between endfire and broadside over a Common Impedance bandwidth. Switch insertion, matching network design, and other issues are addressed. Results for both simulated and measured antennas, as well as recommendations for future work in this area, are provided.
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Enabling High Performance Wireless Communication Systems Using Reconfigurable Antennas
MILCOM 2006, 2006Co-Authors: T.l. Roach, Gregory H. Huff, Jennifer T. BernhardAbstract:The use of multiple antenna systems (MIMO, etc.) and signal combining techniques (Maximal Ratio, Spatial, etc.) can create significant advantages in situations requiring a high degree of system agility. Furthermore, the ability to resolve coherent information channels in the context of electrically hostile environments (e.g., noise or jamming sources and complex scattering and/or multi-path environments) can be of significant importance in both logistic and battlefield environments. This work focuses on the combination of radiation reconfigurable antennas and signal processing techniques, focusing on their applications in advanced wireless communication systems and mobile or ad hoc networks. Experimental data demonstrating these concepts will be provided for a canonical structure capable of integrating multiple reconfigurable radiation antennas that have been designed to switch between broadside and endfire radiation characteristics (operating over a Common Impedance bandwidth). This work reveals both the possibilities and the importance of using reconfigurable radiation antennas, and gauges the potential impact on applications requiring a high degree of performance from the radiating structure(s).
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A Small Array of Boresight to Endfire Radiation Reconfigurable Antennas
2003Co-Authors: Gregory H. Huff, J. Feng, Jennifer T. BernhardAbstract:Abstract : This work describes the development of a 2x2 array of pattern reconfigurable antennas, capable of switching between boresight and endfire radiation patterns over a Common Impedance bandwidth. The reconfigurable element for the array is a single turn square spiral microstrip antenna on an electrically thin substrate, and is capable of reconfiguring its radiation pattern from boresight to endfire using two surface-mounted switching elements. An outline of the theory developed for standing wave devices to generate reconfigurable pattern behavior is also included. Application of the antenna array to geosynchronous satellites is also provided.
Kwai-man Luk - One of the best experts on this subject based on the ideXlab platform.
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A Cavity-Integrated Self-Polarizing Method for Circularly Polarized Fabry-Perot Antenna Design
2018 IEEE International Symposium on Antennas and Propagation & USNC URSI National Radio Science Meeting, 2018Co-Authors: Kwai-man LukAbstract:In this paper, we present a self-polarizing approach to realize circularly polarized (CP)Fabry-Perot antenna (FPA)using linearly polarized feed. The antenna configuration is simple, including a conventional single-cavity, dielectric-superstrate FPA and a specially designed all-dielectric structure integrated in the FPA cavity. This is a new design method of obtaining CP radiation for this class of antenna. The achieved wide Common Impedance and axial ratio bandwidth outperforms state-of-the-art designs.
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a dual mode wideband mimo cube antenna with magneto electric dipoles
IEEE Transactions on Antennas and Propagation, 2014Co-Authors: Shaobo Chen, Kwai-man LukAbstract:A four-port wideband diversity antenna capable of radiating two broadside patterns and two omnidirectional patterns is realized. This antenna is composed of five dual-polarized magneto-electric dipole elements mounted on the five faces of a grounded metallic cubic structure. By rotationally combining the four dual-polarized elements in a ring-configuration, θ-and φ-polarized waves can be excited, whereas x-and y-polarized orthogonal waves are excited by another radiating element mounted on the top of the whole metallic cube. The simulated Common Impedance bandwidth for these four modes is 38.7% with SWR from 1.77 GHz to 2.62 GHz, while the measured one is 39.1% with SWR from 1.73 GHz to 2.57 GHz. The mutual coupling between any two modes is lower than -30 dB which is low enough for practical usage. This antenna is suitable for wireless communication systems with a hemispherical coverage requirement.
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High performance dual-band dual-polarized magneto-electric dipole base station antenna
2014Co-Authors: Shaobo Chen, Kwai-man LukAbstract:A wideband dual-band dual-polarized antenna suitable for modern base station system is developed. The low band element is composed of four aluminum chunks mounted in a metallic cavity reflector, whereas the high band element is constructed by four triangular aluminum plates and four triangular metal posts. In the center of the whole antenna, the middle area of the low band element is excavated to allocate the high band one. Both of the high band and the low band elements operate as complementary radiators of magnetic dipole and electric dipole. The measured Common Impedance bandwidth for the low band is 21.2% ranging from 0.80 GHz to 0.99 GHz, while the measured one for the high band is 28.4% from 1.66 GHz to 2.21 GHz (SWR < 2). Good agreement could be observed between simulation and measurement. Due to the arrangement of the two radiating elements, it is promising to realize a dual band dual polarized array antenna for modern base station applications.
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A wideband dual-polarized antenna with very low back radiation
2012 Asia Pacific Microwave Conference Proceedings, 2012Co-Authors: Kwai-man LukAbstract:A wideband ±45° dual-polarized antenna based on the magneto-electric dipole is excited by a new feeding technique. The Common Impedance bandwidth is from 1.69GHz to 2.76GHz (48.1%) with SWR≤1.5. The isolation between the two ports is larger than 30dB. The gains of the proposed antenna vary in the range of 7.6–9.3dBi and 7.6–9.4dBi for port 1 and port 2 respectively in the operating frequency range. Due to its complementary nature (or Huygens' source), the proposed antenna has a stable radiation pattern with a low cross-polarization level of less than −21dB and a low back radiation level of less than −29dB.
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A Broadband Dual-Polarized Magneto-Electric Dipole Antenna With Simple Feeds
IEEE Antennas and Wireless Propagation Letters, 2009Co-Authors: Kwai-man LukAbstract:A novel dual-polarized magneto-electric dipole antenna excited by two -shaped strips is presented. The antenna achieves a Common Impedance bandwidth of 65.9% (SWR < 2) at both input ports. The antenna has excellent performance in isolation, which is more than 36 dB between the two input ports, and the gain of the antenna is about 9.5 dBi. The radiation pattern and bandwidth over the operating frequency band are very stable.
Jennifer Truman Bernhard - One of the best experts on this subject based on the ideXlab platform.
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integration of packaged rf mems switches with radiation pattern reconfigurable square spiral microstrip antennas
IEEE Transactions on Antennas and Propagation, 2006Co-Authors: Gregory H. Huff, Jennifer Truman BernhardAbstract:This work describes the integration of commercially available packaged radio frequency microelectromechanical system (RF MEMS) switches with radiation pattern reconfigurable microstrip antennas. Most applications of RF MEMS switches consider the switches as only circuit elements. In contrast, the implementation of packaged switches in this particular antenna must address not only the simple open/closed behavior of the switches but also their impact on the radiation characteristics of the reconfigurable antenna. Here, two Radant MEMS single-pole single throw (SPST) SPST-RMSW100 (packaged RF MEMS) switches are used to reconfigure the radiation patterns of a resonant square spiral microstrip antenna between endfire and broadside over a Common Impedance bandwidth. Switch insertion, matching network design, and other issues are addressed. Results for both simulated and measured antennas, as well as recommendations for future work in this area, are provided.
T.l. Roach - One of the best experts on this subject based on the ideXlab platform.
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A comparative study of diversity gain and spatial coverage: Fixed versus reconfigurable antennas for portable devices
Microwave and Optical Technology Letters, 2007Co-Authors: T.l. Roach, Gregory H. Huff, Jennifer T. BernhardAbstract:This study investigates the performance of planar fixed and/or pattern reconfigurable antennas on a model laptop in terms of diversity gain and spatial coverage. The reconfigurable antenna used in this work has the ability to change its radiation pattern from endfire to broadside while operating over a Common Impedance bandwidth. The research combines diversity gain and spatial coverage into a single parameter that takes into account the effects of both simultaneously. Experimental data, including the resulting diversity gain and spatial coverage calculations, are presented. This work reveals the possibilities and importance of using reconfigurable radiation antennas and weighs their potential impact on high performance wireless systems. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 535–539, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22181
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AHS - On the Applications for a Radiation Reconfigurable Antenna
Second NASA ESA Conference on Adaptive Hardware and Systems (AHS 2007), 2007Co-Authors: T.l. Roach, Gregory H. Huff, Jennifer T. BernhardAbstract:In this work, applications involving a radiation reconfigurable antenna are presented and discussed. The antenna is capable of reconfiguring its radiation pattern from broadside to endfire over a Common Impedance bandwidth. After outlining the operation and radiation behavior of the single element its use in multiple antenna systems, such as multiple input-multiple output (MIMO) and diversity systems, is described. Recent results using the antenna in both one-dimensional and two-dimensional planar arrays setting are also included. These examples illustrate the potential benefits and impact that pattern reconfigurable antennas can have in diverse kinds of wireless communications networks.
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Enabling High Performance Wireless Communication Systems Using Reconfigurable Antennas
MILCOM 2006, 2006Co-Authors: T.l. Roach, Gregory H. Huff, Jennifer T. BernhardAbstract:The use of multiple antenna systems (MIMO, etc.) and signal combining techniques (Maximal Ratio, Spatial, etc.) can create significant advantages in situations requiring a high degree of system agility. Furthermore, the ability to resolve coherent information channels in the context of electrically hostile environments (e.g., noise or jamming sources and complex scattering and/or multi-path environments) can be of significant importance in both logistic and battlefield environments. This work focuses on the combination of radiation reconfigurable antennas and signal processing techniques, focusing on their applications in advanced wireless communication systems and mobile or ad hoc networks. Experimental data demonstrating these concepts will be provided for a canonical structure capable of integrating multiple reconfigurable radiation antennas that have been designed to switch between broadside and endfire radiation characteristics (operating over a Common Impedance bandwidth). This work reveals both the possibilities and the importance of using reconfigurable radiation antennas, and gauges the potential impact on applications requiring a high degree of performance from the radiating structure(s).