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ABSTRACT: A variety of antennas have been engineered with metamaterials (MTMs) and metamaterial-inspired constructs to improve their performance characteristics. Examples include electrically small, near-field resonant parasitic (NFRP) antennas that require no matching network and have high radiation efficiencies. Experimental verification of their predicted behaviors has been obtained. Recent developments with this NFRP electrically small paradigm will be reviewed. They include considerations of increased bandwidths, as well as multiband and multifunctional extensions.
Proceedings of the IEEE 11/2011; · 6.81 Impact Factor
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ABSTRACT: Several metamaterial-inspired, electrically small, near-field resonant parasitic antennas are presented. Both electric and magnetic couplings to the parasitic are compared and contrasted. The electric-coupled versions are shown to be more efficient and to have more bandwidth. The evolution of circular polarized designs from their linear counterparts by introducing multiple parasitics having different resonant frequencies is demonstrated. Single L1 and dual band L1/L2 GPS systems are emphasized for practical illustrations of the resulting performance characteristics. Preliminary experimental results for a dual band, circularly polarized GPS L1/L2 antenna are provided and underscore several practical aspects of these designs.
IEEE Transactions on Antennas and Propagation 06/2011; · 2.15 Impact Factor
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ABSTRACT: Several electrically small antenna systems that utilize the magnetic couplings between a coaxially-fed semi-loop antenna and capacitively-loaded loop (CLL)-based near-field resonant parasitic (NFRP) elements are presented. Both one and two gap CLL elements are considered; their impact on the system performance, particularly their effects of the resonance frequencies and the corresponding Q values, is evaluated. By integrating multiple NFRP CLL elements with the coaxially-fed semi-circular loop antenna, electrically small multi-band systems are achieved. They can be designed for a broad range of frequencies by tuning the NFRP elements separately. Dual band designs are reported that achieve operation at the GPS LI (1.5754 GHz) and L2 (1.2276 GHz) frequencies. Their operational modes and performance characteristics are studied. These lead to additional electrically small antenna designs, which feature only one driven loop antenna and two NFRP CLL elements and which achieve circularly polarized (CP) operation. A CP antenna whose electrical size is ka = 0.495 at the GPS LI frequency is presented in detail. Its simulated bandwidth and beamwidth, for which the axial ratio (AR) is less than 3 dB, are, respectively, 7.8 MHz and 76°.
IEEE Transactions on Antennas and Propagation 04/2011; · 2.15 Impact Factor
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ABSTRACT: A 1.575 GHz rectenna has been developed for low input power operation. The rectenna incorporates a high efficiency, electrically small, metamaterial-inspired near field resonant parasitic antenna, and a Schottky diode that has a low built-in voltage, and a resistor as the load. The rectenna was analyzed with the Harmonic Balance method provided by the Advanced Design System (ADS). The measurement results show that the output efficiency of the rectenna with the resistive load is 34.1% and the voltage across the resistor is 0.73 V when the power delivered to the antenna is 1.0 mW (0.0 dBm). The predicted and measured results are in reasonable agreement.
Radio and Wireless Symposium (RWS), 2011 IEEE; 02/2011
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ABSTRACT: A wide variety of metamaterial-engineered NFRP ESAs have been designed, fabricated and tested. The predicted and measured performance properties of several of these metamaterial-engineered NFRP ESAs will be compared in our presentation.
Antennas and Propagation Society International Symposium (APSURSI), 2010 IEEE; 08/2010
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ABSTRACT: We have developed a variety of electrically small, near-field resonant parasitic (NFRP) antennas. Several examples and their performance characteristics will be presented. These are based on capacitively-loaded loop (CLL) NRFPs with both electric and magnetic couplings to the driven element; both varieties will be compared and contrasted. Integrating multiple NFRP CLL elements with coaxially-fed electrically-small monopoles or semi-circular loop antennas, both single- and dual-band, linearly (LP) and circularly polarized (CP) antenna designs are achieved. The CP designs rely on two orthogonal equivalent magnetic dipoles tuned at slightly different resonance frequencies to achieve the requisite 90° phase shift between them at an intermediate frequency. Two driven monopoles are required for the electrically-coupled version; one driven semi-loop antenna is required for the magnetically-coupled version. However, only the electrically-coupled design has enough tuning parameters to lead to a dual-band, NFRP CLL-based CP antenna. This dual-band CP design will be discussed in our presentation.
Antenna Technology (iWAT), 2010 International Workshop on; 04/2010
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ABSTRACT: The possibility of using an active internal matching element in several types of metamaterial-inspired, electrically small antennas (ESAs) to overcome their inherent narrow bandwidths is demonstrated. Beginning with the Z antenna, which is frequency tunable through its internal lumped element inductor, a circuit model is developed to determine an internal matching network, i.e., a frequency dependent inductor, which leads to the desired enhanced bandwidth performance. An analytical relation between the resonant frequency and the inductor value is determined via curve fitting of the associated HFSS simulation results. With this inductance-frequency relation defining the inductor values, a broad bandwidth, electrically small Z antenna is established. This internal matching network paradigm is then confirmed by applying it to the electrically small stub and canopy antennas. An electrically small canopy antenna with k?? = 0.0467 that has over a 10% bandwidth is finally demonstrated. The potential implementation of the required frequency dependent inductor is also explored with a well-defined active negative impedance converter circuit that reproduces the requisite inductance-frequency relations.
IEEE Transactions on Antennas and Propagation 03/2010; · 2.15 Impact Factor
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ABSTRACT: Electrically small electric and magnetic dipole antennas are introduced that are based on electric and magnetic near-field resonant parasitic (NFRP) elements that are electrically coupled to the driven element. By properly combining these two NFRP antenna types, electrically small Huygens sources are realized. The proposed Huygens sources have one feed point, are well matched to 50 Ω, and have high radiation efficiencies. Their predicted directivity patterns approach the known Huygens source theoretical limit.
IEEE Antennas and Wireless Propagation Letters 02/2010; · 1.37 Impact Factor
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ABSTRACT: Metamaterial-inspired electrically small Z, stub and canopy antennas are reported. They are near-field, resonant parasitic designs. Different Z and stub antenna configurations and the effect on their Q values are studied. Their behavior led to the canopy antenna design. At the size of ka ~ 0.046, the canopy antenna is an electric-based antenna with high overall efficiency (over 90%) and low Q -ratio value and whose input resistance is almost completely matched to a 50 Omega source. The resonant frequency, ~300 MHz, in the UHF band is selected for the designs. The canopy antenna is studied extensively to explore the lowest achievable Q values. Various coupling configurations, canopy shapes, and metal-air ratios are investigated. Circuit models are also introduced to explain the radiation mechanism. Numerical simulation results are analyzed and compared with previously derived Q value limits for electrically small antennas that are based on the standard circuit models of spherical wave multipoles. The Q value of the canopy antenna for the lowest order, single electric resonance is shown to reach a fundamental limit of approximately 1.75 times the Chu value.
IEEE Transactions on Antennas and Propagation 10/2009; · 2.15 Impact Factor
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ABSTRACT: In this paper, a very electrically small canopy antenna is introduced. The canopy antenna radiates at ap 297Mhz with a Q<sub>ratio</sub> ap 1.75. An active internal matching network is applied to this canopy antenna; over a 10% fractional bandwidth is obtained for this ESA (a ~ lambda/137).
Antennas and Propagation Society International Symposium, 2009. APSURSI '09. IEEE; 07/2009
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ABSTRACT: Electrically small antennas are a critical enabling technology for a variety of wireless applications. The usually incompatible demands for electrically small, efficient, and broad bandwidth antenna systems often becomes further acerbated by practical demands of multi-functionality, low weight, low cost, and easy manufacturing. A variety of metamaterial-based and metamaterial-inspired antenna systems have been achieved recently that meet many of these demands. The essential features of these antennas and the experimental validation of their performance, especially their overall efficiencies, as well recent design extensions that have bandwidths near the Chu limit, will be reviewed.
Antenna Technology, 2009. iWAT 2009. IEEE International Workshop on; 04/2009
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ABSTRACT: The paper discusses analysis and measurements of electrically small antennas. The antennas discussed here are based on antennas designed from metamaterial inspired concepts. An electromagnetic reverberation chamber is used for the tests of the antennas. A reverberation chamber is basically a shielded room (metallic wall) with an arbitrarily shaped metallic rotating paddle and is an ideal environment for measuring the total radiated power of an antenna. Simulations and measurements of various antennas will be presented.
Antenna Technology, 2009. iWAT 2009. IEEE International Workshop on; 04/2009
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ABSTRACT: Both 300- and 570-MHz versions of an electrically small, coaxially fed Z antenna were designed and tested. These two cases demonstrate the ability to change the resonance frequency of the Z antenna by changing the value of its lumped element inductor. The numerically predicted and measured results are in good agreement.
IEEE Antennas and Wireless Propagation Letters 02/2009; · 1.37 Impact Factor
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ABSTRACT: A metamaterial-enabled approach is presented that allows one to engineer the dispersion of a log-periodic dipole array antenna (LPDA) to make it more suitable for wide bandwidth pulse transmission. By modifying the LPDA with electrically small transmission line metamaterial-based negative and positive phase shifters, the phase of each element of the LPDA are adjusted such that in the main beam direction, the phase shifts between each element approximates a linear phase variation. The performance characteristics of the resulting dispersion-engineered LPDA are obtained numerically with HFSS and MATLAB simulations. By measuring in the far field the fidelity between the actual transmitted pulse and the idealized output waveform, the required component values of the phase shifters are optimized. Significant improvements in the fidelity of the pulses transmitted are demonstrated with eight and ten element LPDAs.
IEEE Transactions on Antennas and Propagation 01/2009; · 2.15 Impact Factor
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ABSTRACT: The performance characteristics of a simplified electric, lumped-element based, meta-material -inspired, efficient, electrically small antenna have been determined numerically for a fixed reactive element value over a band of frequencies. These characteristics were used to define an internal matching network (in contrast to the usual non-Foster external matching networks) which would provide the appropriate reactance at the appropriate frequency that can substantially increase the instantaneous bandwidth of the antenna. Over 10% instantaneous fractional bandwidth for an system with ka 0.048 (i.e., a/lambda<sub>0</sub> 132) while maintaining a high overall efficiency has been demonstrated at VHF frequencies.
Antennas and Propagation Society International Symposium, 2008. AP-S 2008. IEEE; 08/2008
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ABSTRACT: We are considering transmission line-based metamaterials (MTMs) to achieve negative phase shift elements and their introduction into a log-periodic array to correct for the detrimental phase shifts associated with it. We have preliminary indications that this approach leads to a modified log-periodic array that has a flat spectral response over a wide frequency band. Consequently, this modified log-periodic array may be applicable to UWB applications.
Antennas and Propagation Society International Symposium, 2007 IEEE; 07/2007
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ABSTRACT: Electrically small antennas are a critical enabling technology for a variety of wireless applications. A variety of metamaterial-inspired antenna systems have been designed, fabricated and tested recently that meet many of the performance demands for these applications, including high effi-ciency, broad bandwidth, and multi-functionality. These designs and their operating characteristics will be reviewed.
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ABSTRACT: Electrically small antennas (ESAs) are a critical enabling technology for many wireless applications. The usually incompatible demands for electrically small, efficient, and broad bandwidth systems becomes further acerbated by practical demands of low weight, low cost, and easy manufacturing. A variety of metamaterial-based and metamaterial-inspired designs have been achieved that meet many of these demands from the VHF and UHF bands to millimeter-wave frequencies. These designs, their fabrication and experimental validation will be reviewed.
