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ABSTRACT: We present a compact dual-band patch antenna array designed for use in a 3-D microwave tomography system for breast imaging. The array is designed for operation within the interstitial space of an MRI patient support platform. This configuration permits scattered-field data acquisition with the breast in the same position as a benchmark MRI scan, thereby enabling precise co-registration with breast MRI. We investigate operating characteristics of the antenna array elements contained in the array using numerical simulations. We demonstrate that dual-band operation of the array is maintained in the presence of an ellipsoidal breast phantom.
General Assembly and Scientific Symposium, 2011 XXXth URSI; 09/2011
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ABSTRACT: We propose a new communication architecture - continuous aperture phased MIMO - that combines the elements of MIMO, continuous aperture antennas, and phased arrays, for achieving the capacity of line-of-sight (LoS) links. CAP-MIMO is based on a hybrid analog-digital transceiver architecture that employs a novel antenna array structure - a high-resolution discrete lens array - to enable a continuous aperture phased-MIMO operation with a low-complexity analog-digital interface. Our focus is on millimeter-wave (60-100GHz) LoS links for high-rate (1-100Gb/s) applications. We propose a framework for modeling and analyzing a LoS link in beamspace, discuss the key elements of the CAP-MIMO system, and present results on its significant capacity advantages over two state-of-the-art designs: i) systems that employ continuous aperture “dish” antennas for high power efficiency but no spatial multiplexing gain, and ii) MIMO systems that use discrete antenna arrays for multiplexing gain but suffer in power efficiency.
Antennas and Propagation (APSURSI), 2011 IEEE International Symposium on; 08/2011
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ABSTRACT: Many insects possess acute directional hearing capabilities and are able to localize sound sources of interest with an astonishing degree of precision. An analogy can be drawn between the auditory systems of such insects and electrically small antenna arrays that demonstrate enhanced sensitivity to the direction of arrival of an electromagnetic wave, compared to regular arrays occupying the same aperture. Inspired by this, we discuss the design of biologically inspired electrically small antenna arrays that mimic the hearing mechanism of such insects. A method for designing such antenna arrays is presented, and the tradeoffs involved in achieving this enhanced sensitivity are discussed. Simulation and measurement results of two fabricated prototypes are also presented and discussed in this letter.
IEEE Antennas and Wireless Propagation Letters 02/2011; · 1.37 Impact Factor
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ABSTRACT: We present a comprehensive synthesis procedure for designing low-profile, band-pass frequency selective surfaces composed of non-resonant constituting elements. The proposed FSSs use arrays of sub-wavelength periodic structures with non-resonant constituting unit cells with unit cell dimensions and periodicities in the range of , where is the free space wavelength. The main advantages of this type of FSS, compared to traditional ones, are that they allow for the design of low-profile and ultra-thin FSSs that can provide sharp frequency selectivity and stable frequency responses as functions of angle and polarization of incidence of the EM wave. An order FSS designed using this technique typically has an electrical thickness in the order of which is significantly smaller than the overall thickness of a traditionally designed order FSS . The proposed synthesis procedure is validated for two FSS prototypes having third- and fourth-order band-pass responses. Principles of operation, detailed synthesis procedure, measurement results of a fabricated prototype, and implementation guidelines for this type of FSS are presented and discussed in this paper.
IEEE Transactions on Antennas and Propagation 01/2011; · 2.15 Impact Factor
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ABSTRACT: We present a new design of a dual-band frequency selective surface (FSS) with closely spaced bands of operation and a highly-selective frequency response at each band. A multi-stage design procedure is also proposed for the design and synthesis of this class of frequency selective surfaces. The design procedure is based on synthesizing the desired device from its equivalent circuit parameter values. An approximate analytical technique is provided, which can be used to determine the values of the equivalent circuit parameters of this dual-band device from the basic system level characteristics of its transfer function including the center frequencies of operations of its two bands of operation and the bandwidth at each of these bands. The use of this design procedure is described in detail by a design example which follows the proposed design procedure step by step; the validity of the procedure is verified using full-wave EM simulations and experimental characterization of a fabricated prototype of the proposed device. Experimental characterizations of this device show that it has a stable frequency response as a function of angle of incidence for both the transverse electric (TE) and the transverse magnetic (TM) polarizations. This stability is attributed to the extremely small overall thickness of the structure as well as its small unit cell dimensions.
IEEE Transactions on Antennas and Propagation 01/2011; · 2.15 Impact Factor
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ABSTRACT: Given the proliferation of wireless communication devices, the need for increased power and bandwidth efficiency in emerging technologies is getting ever more pronounced. Two technological trends offer new opportunities for addressing these challenges: mm-wave systems (60-100GHz) that afford large bandwidths, and multi-antenna (MIMO) transceivers that exploit the spatial dimension. In particular, there has been significant recent interest in mm-wave communication systems for high-rate (1-100 Gb/s) communication over line-of-sight (LoS) channels. Two competing designs dominate the state-of-the-art: i) traditional systems that employ continuous aperture “dish” antennas and offer high power efficiency but no spatial multiplexing gain, and ii) MIMO systems that use discrete antenna arrays for a higher multiplexing gain but suffer from power efficiency. In this paper, we propose a new communication architecture - continuous aperture phased MIMO - that combines the advantages of both designs and promises very significant capacity gains, and commensurate gains in power and bandwidth efficiency, compared to the state-of-the-art. CAP-MIMO is based on a hybrid analog-digital transceiver architecture that employs a novel antenna array structure - a high-resolution discrete lens array - to enable a continuous aperture phased-MIMO operation. We present the basic theory behind CAP-MIMO and the potential capacity/power gains afforded by it. We also highlight potential applications of CAP-MIMO in mm-wave communications.
Communication, Control, and Computing (Allerton), 2010 48th Annual Allerton Conference on; 11/2010
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ABSTRACT: A biomimetic electrically small antenna system is proposed in this paper, which may lead to advancements in designing electrically small antennas. It was demonstrated that using an antenna system modeled based on the hearing mechanism of a parasitoid fly may allow us to design electrically small antenna systems with directional characteristics that are commonly found in larger antenna array systems. Further investigations are necessary to evaluate the extent to which such biomimetic concepts can enhance the current state-of-the-art in electrically small antenna design.
Wireless Information Technology and Systems (ICWITS), 2010 IEEE International Conference on; 10/2010
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ABSTRACT: In this letter, a new technique for designing tunable frequency selective surfaces (FSSs) with the second-order band-pass response is presented and experimentally verified. The technique is applied to an FSS utilizing nonresonant, subwavelength, constituting unit cells. Frequency tuning is achieved by adjusting the location of a liquid metal slug within capillary tubes embedded between the FSS's metallic layers. A wideband flexible frequency tuning covering nearly the entire X band is tested in a waveguide environment and excellent agreement between the measured and simulated results is demonstrated.
IEEE Microwave and Wireless Components Letters 09/2010; · 1.72 Impact Factor
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ABSTRACT: A new technique for design low profile FSS with high order band-pass performance is presented. By choosing the hybrid resonator properly, single band with third order performance or dual band with second order behavior at upper band and first order behavior at lower band can be realized.
Antennas and Propagation Society International Symposium (APSURSI), 2010 IEEE; 08/2010
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ABSTRACT: In this paper, we apply this technique to a class of MEFSSs with second-order band-pass responses capable of providing a phase shift of 0180° in their pass-band. We show how dynamic phase shift tuning can be obtained. To prove the proposed tuning concept, a waveguide version of a second-order band-pass MEFSS is fabricated and tested at X-band.
Antennas and Propagation Society International Symposium (APSURSI), 2010 IEEE; 08/2010
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ABSTRACT: This paper introduces a generalized methodology to design low profile N<sup>th</sup>-order bandpass frequency selective surfaces. The generalized methodology is based on coupled resonators filter theory. The design procedure is validated by design examples of second and third-order frequency selective surface with band-pass response.
Antennas and Propagation Society International Symposium (APSURSI), 2010 IEEE; 08/2010
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ABSTRACT: In this paper, a new technique for designing low-profile dual-band frequency selective surfaces, with second-order band pass responses, is presented. Using this technique, a dual-band response with a small separation between the two bands and high out-of-band rejection can be achieved. Similar to the structure reported in [6], the constituting elements composed of resonant elements and sub-wave length non-resonant elements. The combination of sub-wavelength unit cell dimensions and the small overall thickness of the proposed structure results in an FSS with a frequency response that is less sensitive to the angle of incidence of the EM wave.
Antennas and Propagation Society International Symposium (APSURSI), 2010 IEEE; 08/2010
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ABSTRACT: In this paper a dual-band miniaturized patch antenna element for a 3-D breast imaging sensor array is designed, fabricated, and validated experimentally. The miniaturized patch antenna exhibits higher gain at the desired frequencies. This will ensure a higher signal-to-noise ratio and imaging sensitivity when immersed in the coupling medium. A high degree of correlation between simulated and measured values is obtained. Due to its miniature size, multi-frequency performance, and efficient radiation characteristics, this antenna is a promising candidate for use in a 3-D microwave tomographic system.
Antennas and Propagation Society International Symposium (APSURSI), 2010 IEEE; 08/2010
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ABSTRACT: We present a generalized synthesis procedure for designing low-profile frequency selective surfaces (FSS) with bandpass responses of odd-order (N = 3,5,7,...). The FSSs designed using this technique use a combination of resonant and non-resonant sub-wavelength constituting unit cells with unit cell dimensions and periodicities in the order of 0.15 λ<sub>0</sub>, where λ<sub>0</sub> is the free space wavelength. The main advantage of using this technique, compared to traditional FSS design techniques, is that it allows for the design of low-profile and ultrathin FSSs that can provide sharp frequency selectivity. An Nth order FSS designed using this technique typically has an electrical thickness in the order of ~ (N - 1) λ<sub>0</sub>/50 which is significantly smaller than the overall thickness of a traditionally designed Nth order FSS (~ (N - 1) λ<sub>0</sub>/4). The proposed synthesis procedure is validated for two FSS prototypes having third- and fifth-order bandpass responses. Principles of operation, detailed synthesis procedure, and implementation guidelines for this type of FSS are presented and discussed in this communication.
IEEE Transactions on Antennas and Propagation 08/2010; · 2.15 Impact Factor
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ABSTRACT: We present a miniaturized, dual-band patch antenna array element that is designed for use in a three-dimensional (3-D) microwave tomography system for breast imaging. Dual-band operation is achieved by manipulating the fundamental resonant mode of the patch antenna and one of its higher order modes. Miniaturization and tuning of the resonant frequencies are achieved by loading the antenna with nonradiating slots at strategic locations along the patch. This results in a compact, dual-band antenna with symmetric radiation patterns and similar radiation characteristics at both bands of operation. The performance of the antenna in a biocompatible immersion medium is verified experimentally.
IEEE Antennas and Wireless Propagation Letters 02/2010; · 1.37 Impact Factor
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ABSTRACT: A new technique for designing wideband dual-polarized slot antennas is presented. The proposed structure is in the form of a differentially fed cross-slot antenna backed by a shallow substrate-integrated cavity with a depth of approximately λ<sub>0</sub>/10 . This technique takes advantage of a double-resonance observed in off-center microstrip-fed slot antennas to enhance its bandwidth to double that of typical cavity-backed cross-slot antennas of the same size. Experimental results demonstrate a bandwidth of 19%, average gain of 5.3 dBi, isolation better than 28 dB, and wideband polarization purity.
IEEE Antennas and Wireless Propagation Letters 02/2010; · 1.37 Impact Factor
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N. Behdad
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ABSTRACT: In this paper, we present some of our recent results in the area of designing single- and dual-polarized miniaturized slot antennas. Examples of miniaturized slot antennas that are 15 to 20 times smaller than traditional dipole or patch antennas are presented and discussed. In particular two examples of miniaturized on-chip slot antennas, operating at 5.0 GHz and 9.0 GHz frequency bands, integrated with radio frequency integrated circuits on a complementary metal oxide semiconductor (CMOS) chips are presented and discussed. Finally, the design and operational principles of a dual-polarized electrically small slot antenna is presented.
Antenna Technology, 2009. iWAT 2009. IEEE International Workshop on; 04/2009
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ABSTRACT: In this study, a new method for designing low profile frequency selective surfaces (FSS) with second-order bandpass responses is presented. The FSSs designed using this technique utilize non-resonant subwavelength constituting unit cells with unit cell dimensions and periodicities in the order of 0.15lambda<sub>0</sub>. It is demonstrated that using the proposed technique, second-order FSSs with an overall thickness of lambda<sub>0</sub>/30 can be designed. This is considerably smaller than the thickness of second-order FSSs designed using traditional techniques and could be particularly useful at lower frequencies with long wavelengths. To facilitate the design of this structure, an equivalent circuit based synthesis method is also presented in this paper. Two bandpass FSS prototypes operating at X-band are designed, fabricated, and tested. A free space measurement setup is used to thoroughly characterize the frequency responses of these prototypes for both the TE and TM polarizations and various angles of incidence. The frequency responses of these structures are shown to have a relatively low sensitivity to the angle of incidence. Principles of operation, detailed design and synthesis procedure, and measurement results of two fabricated prototypes are presented and discussed in this paper.
IEEE Transactions on Antennas and Propagation 03/2009; · 2.15 Impact Factor
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ABSTRACT: We demonstrate a new class of low-profile frequency selective surfaces (FSS) with an overall thickness of lambda/24 and a third-order bandpass frequency response. The proposed FSS is a three layer structure composed of three metal layers, separated by two electrically thin dielectric substrates. Each layer is a two-dimensional periodic structure with sub-wavelength unit cell dimensions and periodicity. The unit cell of the proposed FSS is composed of a combination of resonant and non-resonant elements. It is shown that this arrangement acts as a spatial bandpass filter with a third-order bandpass response. However, unlike traditional third-order bandpass FSSs, which are usually obtained by cascading three identical first-order bandpass FSSs a quarter wavelength apart from one another and have thicknesses in the order of lambda/2 , the proposed structure has an extremely low profile and an overall thickness of about lambda/24 , making it an attractive choice for conformal FSS applications. As a result of the miniaturized unit cells and the extremely small overall thickness of the structure, the proposed FSS has a reduced sensitivity to the angle of incidence of the EM wave compared to traditional third-order frequency selective surfaces. The principles of operation along with guidelines for the design of the proposed FSS are presented in this paper. A prototype of the proposed third-order bandpass FSS is also fabricated and tested using a free space measurement system at C band.
IEEE Transactions on Antennas and Propagation 03/2009; · 2.15 Impact Factor
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ABSTRACT: In this letter, a new technique for designing dual-band frequency selective surfaces with arbitrary bands of operation, with second-order band-pass responses at each band of operation, is presented and experimentally verified. The technique is based on utilizing a particular topology of a second-order band-pass microwave filter and synthesizing its constituting elements using periodic structures with inductive, capacitive, or resonant type surface impedances. The result is a low-profile planar structure composed of three metal and two dielectric layers that acts as a spatial version of the dual-band microwave filter.
IEEE Microwave and Wireless Components Letters 01/2009; · 1.72 Impact Factor
