The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Wee-sang Park - One of the best experts on this subject based on the ideXlab platform.
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design of a frequency selective surface fss type superstrate for dual band Directivity enhancement of microstrip patch antennas
IEEE Antennas and Propagation Society International Symposium, 2005Co-Authors: Raj Mittra, Wee-sang ParkAbstract:A novel design of a high-Directivity resonator antenna that utilizes a two-layered frequency selective surface (FSS) superstrate - as an alternative to a dielectric electromagnetic band gap (EBG) superstrate - for dual band Directivity enhancement and reduction in height is presented in this paper.
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thin frequency selective surface fss superstrate with different periodicities for dual band Directivity enhancement
International Workshop on Antenna Technology, 2005Co-Authors: Raj Mittra, Wee-sang ParkAbstract:In this paper we present a novel design of a high Directivity resonator antenna that utilizes a two-layered frequency selective surface (FSS) superstrate with different periodicities - as an alternative to a conventional FSS superstrate - for dual band Directivity enhancement to reduce its height. Two strip dipole arrays with different periodicities are placed above and below a dielectric layer. The proposed thin FSS superstrate yields 13.1 and 19.54 dBi Directivity enhancements at 8.75 GHz and 12.7 GHz, respectively, as compared to that of a patch antenna (6 dBi), while its height is only one half of that of a conventional patch antenna.
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Design of a Frequency Selective Surface (FSS) type superstrate for dualband Directivity enhancement of microstrip patch antennas
IEEE Antennas and Propagation Society AP-S International Symposium (Digest), 2005Co-Authors: Young-ju Lee, Junho Yeo, Raj Mittra, Wee-sang ParkAbstract:A novel design of a high-Directivity resonator antenna that utilizes a two-layered frequency selective surface (FSS) superstrate - as an alternative to a dielectric electromagnetic band gap (EBG) superstrate - for dual band Directivity enhancement and reduction in height is presented in this paper.
Karu P Esselle - One of the best experts on this subject based on the ideXlab platform.
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Comparison Between Fully and Partially Filled Dielectric Materials on the Waveguide of Circularly Polarised Radial Line Slot Array Antennas
2020 International Workshop on Antenna Technology (iWAT), 2020Co-Authors: Nishat Yasmin Koli, Karu P Esselle, Muhammad U. Afzal, Md Zahidul IslamAbstract:This paper presents an investigation on the waveguide of circularly polarised radial line slot array (RLSA) antennas to improve gain and radiation bandwidth. Two circularly polarised (CP) RLSA antennas were designed with two different waveguide configurations. In the first configuration the waveguide is fully filled with dielectric materials and in the second configuration the waveguide is partially filled with dielectric materials and rest of the waveguide is filled with air. Numerical results of these two CP-RLSA antennas with two different waveguide configurations are presented and compared. Significant improvements have been made in the 3-dB Directivity bandwidth and aperture efficiency of the antenna having waveguide partially filled with dielectric material. The 3-dB Directivity bandwidth was measured 6.2% and aperture efficiency increased to 55.5%. The CP-RLSA antenna has also achieved a peak Directivity of 31.7 dBic and a gain of 31.2 dBic as compared to the Directivity 30.1 dBic and gain 29.5 dBic, respectively achieved with the CP-RLSA antenna having waveguide fully filled with dielectric material.
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Investigation on Aperture Field Distribution of Circularly Polarised Radial Line Slot Array Antennas
2018 IEEE Asia-Pacific Conference on Antennas and Propagation (APCAP), 2018Co-Authors: Nishat Yasmin Koli, Karu P Esselle, Muhammad U. Afzal, Md Zahidul IslamAbstract:This paper presents an analysis on aperture slot distribution of circularly polarised radial line slot array (RLSA) antennas. Two circularly polarised RLSA (CP-RLSA) antennas were designed with two different layout of slots on the antenna aperture. The distributions were optimised by controlling the slot surface density. Numerical results of these two different aperture distributions are presented and compared. A significant improvement has been made in broadside Directivity. One distribution has achieved a peak Directivity of 22.7 dBi as compared to the Directivity of 19.6 dBi achieved with the other distribution.
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wideband gain enhancement of slot antenna using superstructure with optimised axial permittivity variation
Electronics Letters, 2016Co-Authors: Affan A Baba, Raheel M Hashmi, Karu P EsselleAbstract:A simple method is proposed to significantly enhance the broadside Directivity of a simple slot antenna over a wide bandwidth. This improvement is achieved by introducing a simple optimised dielectric superstructure with an axial variation of permittivity. In this antenna, both the superstructure and ground plane are cylindrical in shape with an area of 1.62λ0 2. The antenna has a measured peak Directivity of 18.1 dBi and an extremely wide 3 dB Directivity bandwidth of 51.1%. A WR-75 waveguide is used to feed the slot antenna. The antenna is well matched over the entire Directivity bandwidth, which extends from 8.75 to 14.75 GHz. The measured average aperture efficiency is ∼88% over the 3 dB Directivity bandwidth.
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a class of extremely wideband resonant cavity antennas with large Directivity bandwidth products
IEEE Transactions on Antennas and Propagation, 2016Co-Authors: Raheel M Hashmi, Karu P EsselleAbstract:Extremely wideband resonant cavity antennas (RCAs) with large Directivity-bandwidth products (DBPs) are presented. Their distinct feature is a single-slab superstrate that has a permittivity gradient in the directions transverse to the antenna axis. The application of such a superstrate in a single-feed RCA improves the DBP by a factor of three or more as compared with superstrates composed of uniform dielectric slabs. Their very small area enables an antenna designer to achieve unprecedented figures of DBP per unit area, from a simple planar antenna. Prototype RCAs have been fabricated and measurements have validated the concept. A measured 3-dB Directivity bandwidth of 52.9% was demonstrated with a measured Directivity of 16.4 dBi for an RCA that has a very small total footprint area of 1.54 $\lambda_0^2$ at the lowest operating frequency (2.84 $\lambda_{0,c}^2$ at the center frequency). This represents an increase of 90% over the previous best measured RCA Directivity bandwidth of 28%.
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Effect of truncating the superstructures in broadband Fabry-Pèrot cavity antennas
2013 SBMO IEEE MTT-S International Microwave & Optoelectronics Conference (IMOC), 2013Co-Authors: Raheel M Hashmi, Karu P Esselle, Basit A. Zeb, Stuart G. HayAbstract:Fabry-Perot cavity antennas, while offering design simplicity and high Directivity, are promising candidates for microwave and millimeter wave communication links. Recommendations for effectively truncating the 1-D/2-D periodic structures, designed to act as superstructures in such antennas, are presented. It is shown that the aperture size in such antennas contributes, in part, towards the Directivity-bandwidth product. A simple Fabry-Perot cavity antenna which uses a two layered 1-D Electromagnetic Band Gap (EBG) structure as its superstructure is studied to quantify the effects of aperture size on peak Directivity and half-power Directivity-bandwidth. Conventional aperture size for such antennas ranges from 5-6λ02, which results in over-dimensioning as well as narrowband behavior. It is shown that comparable performance with existing designs can be achieved by using much smaller aperture sizes and thus reducing the antenna footprint. This work serves as a guide to effectively choose and fine-tune aperture sizes for Fabry-Perot cavity antennas, thus reducing the redundant computational load in the full-scale design process.
Densil Cabrera - One of the best experts on this subject based on the ideXlab platform.
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effect of acoustic environment on the sensitivity of speech transmission index to source Directivity
Architectural Science Review, 2009Co-Authors: Ken Stewart, Densil CabreraAbstract:Source Directivity has the potential to affect speech transmission index (STI) measurements. When the source is a model of a human talker, there is a question of how accurate that model needs to be. However, in many acoustic environments source Directivity has little effect on STI because other factors dominate. One instance is soundfields in which the direct sound is dominant (e.g., in the quiet outdoors, in the nearfield, or in an anechoic room): Directivity will have no effect on STI so long as the direct sound is strong enough. Another instance is soundfields in which the reverberant soundfield is dominant (e.g., in the far field in a room with moderate or more reverberation). This paper examines theoretical situations where source Directivity has a substantial influence on STI because of the balance between direct (or early) and reverberant soundfields, as well as the role that background noise can have in increasing the importance of source Directivity.
Raj Mittra - One of the best experts on this subject based on the ideXlab platform.
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A novel design for a low profile high Directivity Fabry-Perot cavity antenna
2009 IEEE Antennas and Propagation Society International Symposium, 2009Co-Authors: Li Yanfei, Raj Mittra, Lu GuizhenAbstract:In this paper we present a novel design for a low-profile Fabry-Perot (FP) cavity type antenna, which achieves a high Directivity combined with an excellent aperture efficiency. Unlike similar FP cavity-type antennas, that are excited with either a dipole or a microstrip patch antenna (MPA), the proposed approach utilizes a slot feed, which not only is easier to fabricate than the presently available designs, but also offers a better control of the return loss characteristics of the antenna, We show that the proposed design achieves a Directivity of 17.52 dB with an aperture size of 3lambda0 times 3lambda0, and an aperture efficiency of 85% relative to the uniform aperture case (Directivity is 20.53 dB), which is considered to be quite good.
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design of a frequency selective surface fss type superstrate for dual band Directivity enhancement of microstrip patch antennas
IEEE Antennas and Propagation Society International Symposium, 2005Co-Authors: Raj Mittra, Wee-sang ParkAbstract:A novel design of a high-Directivity resonator antenna that utilizes a two-layered frequency selective surface (FSS) superstrate - as an alternative to a dielectric electromagnetic band gap (EBG) superstrate - for dual band Directivity enhancement and reduction in height is presented in this paper.
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thin frequency selective surface fss superstrate with different periodicities for dual band Directivity enhancement
International Workshop on Antenna Technology, 2005Co-Authors: Raj Mittra, Wee-sang ParkAbstract:In this paper we present a novel design of a high Directivity resonator antenna that utilizes a two-layered frequency selective surface (FSS) superstrate with different periodicities - as an alternative to a conventional FSS superstrate - for dual band Directivity enhancement to reduce its height. Two strip dipole arrays with different periodicities are placed above and below a dielectric layer. The proposed thin FSS superstrate yields 13.1 and 19.54 dBi Directivity enhancements at 8.75 GHz and 12.7 GHz, respectively, as compared to that of a patch antenna (6 dBi), while its height is only one half of that of a conventional patch antenna.
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Design of a Frequency Selective Surface (FSS) type superstrate for dualband Directivity enhancement of microstrip patch antennas
IEEE Antennas and Propagation Society AP-S International Symposium (Digest), 2005Co-Authors: Young-ju Lee, Junho Yeo, Raj Mittra, Wee-sang ParkAbstract:A novel design of a high-Directivity resonator antenna that utilizes a two-layered frequency selective surface (FSS) superstrate - as an alternative to a dielectric electromagnetic band gap (EBG) superstrate - for dual band Directivity enhancement and reduction in height is presented in this paper.
Ken Stewart - One of the best experts on this subject based on the ideXlab platform.
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effect of acoustic environment on the sensitivity of speech transmission index to source Directivity
Architectural Science Review, 2009Co-Authors: Ken Stewart, Densil CabreraAbstract:Source Directivity has the potential to affect speech transmission index (STI) measurements. When the source is a model of a human talker, there is a question of how accurate that model needs to be. However, in many acoustic environments source Directivity has little effect on STI because other factors dominate. One instance is soundfields in which the direct sound is dominant (e.g., in the quiet outdoors, in the nearfield, or in an anechoic room): Directivity will have no effect on STI so long as the direct sound is strong enough. Another instance is soundfields in which the reverberant soundfield is dominant (e.g., in the far field in a room with moderate or more reverberation). This paper examines theoretical situations where source Directivity has a substantial influence on STI because of the balance between direct (or early) and reverberant soundfields, as well as the role that background noise can have in increasing the importance of source Directivity.
