@article{hayes_so_qusba_dickey_lazzi_2012, title={Flexible Liquid Metal Alloy (EGaIn) Microstrip Patch Antenna}, volume={60}, ISSN={["0018-926X"]}, DOI={10.1109/tap.2012.2189698}, abstractNote={This paper describes a flexible microstrip patch antenna that incorporates a novel multi-layer construction consisting of a liquid metal (eutectic gallium indium) encased in an elastomer. The combined properties of the fluid and the elastomeric substrate result in a flexible and durable antenna that is well suited for conformal antenna applications. Injecting the metal into microfluidic channels provides a simple way to define the shape of the liquid, which is stabilized mechanically by a thin oxide skin that forms spontaneously on its surface. This approach has proven sufficient for forming simple, single layer antenna geometries, such as dipoles. More complex fluidic antennas, particularly those featuring large, co-planar sheet-like geometries, require additional design considerations to achieve the desired shape of the metal. Here, a multi-layer patch antenna is fabricated using specially designed serpentine channels that take advantage of the unique rheological properties of the liquid metal alloy. The flexibility of the resulting antennas is demonstrated and the antenna parameters are characterized through simulation and measurement in both the relaxed and flexed states.}, number={5}, journal={IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Hayes, Gerard J. and So, Ju-Hee and Qusba, Amit and Dickey, Michael D. and Lazzi, Gianluca}, year={2012}, month={May}, pages={2151–2156} }
 @article{khan_hayes_so_lazzi_dickey_2011, title={A frequency shifting liquid metal antenna with pressure responsiveness}, volume={99}, ISSN={["0003-6951"]}, DOI={10.1063/1.3603961}, abstractNote={This letter describes the fabrication and characterization of a shape shifting antenna that changes electrical length and therefore, frequency, in a controlled and rapid response to pressure. The antenna is composed of a liquid metal alloy (eutectic gallium indium) injected into microfluidic channels that feature rows of posts that separate adjacent segments of the metal. The initial shape of the antenna is stabilized mechanically by a thin oxide skin that forms on the liquid metal. Rupturing the skin merges distinct segments of the metal, which rapidly changes the length, and therefore frequency, of the antenna. A high speed camera elucidates the mechanism of merging and simulations model accurately the spectral properties of the antennas.}, number={1}, journal={APPLIED PHYSICS LETTERS}, publisher={AIP Publishing}, author={Khan, Mohammad Rashed and Hayes, Gerard J. and So, Ju-Hee and Lazzi, Gianluca and Dickey, Michael D.}, year={2011}, month={Jul} }
 @article{singh_ajeet_kwatra_cela_ziriax_d'andrea_lazzi_2010, title={Computation of Induced Current Densities in the Human Body at Low Frequencies Due to Contact Electrodes Using the ADI-FDTD Method}, volume={52}, ISSN={["1558-187X"]}, DOI={10.1109/temc.2009.2039482}, abstractNote={We report the use of the alternating direction implicit (ADI) finite-difference time-domain (FDTD) method in a D-H formulation to compute induced current densities and recruitment volumes in the human body due to contact electrodes for human electromuscular incapacitation devices at frequencies below 200 kHz. A computational model resolution of 1 mm has been used for most of the human body model, including regions proximal to the electrode contact points, while a progressively coarser resolution up to 5 mm is utilized, according to an expanding grid scheme for body regions distant from the source, such as the lower extremities. Using quasi-static assumptions, discrete Fourier transforms have been used to average the electric field values at the desired frequencies for times much shorter than their time periods. The field values induced in the human body were then obtained as ratios with respect to the source, which can be scaled depending on the magnitude. This study suggests that the ADI-FDTD method can be used for the solution of low-frequency large-scale bioelectromagnetic problems. It is shown that, when used with quasi-static assumptions, Fourier series decomposition, and expanding grid, the D-H ADI-FDTD can be an effective computational bioelectromagnetics tool.}, number={3}, journal={IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY}, author={Singh, Vinit and Ajeet, Ajeet and Kwatra, Nitin and Cela, Carlos J. and Ziriax, John and D'Andrea, John and Lazzi, Gianluca}, year={2010}, month={Aug}, pages={537–544} }
 @article{domizioli_hughes_gard_lazzi_2010, title={Noise Correlation in Compact Diversity Receivers}, volume={58}, ISSN={["1558-0857"]}, DOI={10.1109/tcomm.2010.05.080601}, abstractNote={The impact of antenna mutual coupling on signal correlation in multi-antenna receivers has been studied in great detail. By contrast, there has been little work on how mutual coupling affects noise. In this paper we present a noise model for a diversity receiver that includes noise generated by the antennas, front-end amplifiers, and other receiver components. This model shows that noise in a compact diversity receiver may be spatially correlated. Expressions relating noise correlation to properties of the antennas and amplifiers are derived and its impact on the outage probability of an optimal diversity combiner is studied. Examples illustrating the relationship between mutual coupling and noise correlation demonstrate how different noise sources may impact performance in profoundly different ways.}, number={5}, journal={IEEE TRANSACTIONS ON COMMUNICATIONS}, author={Domizioli, Carlo P. and Hughes, Brian L. and Gard, Kevin G. and Lazzi, Gianluca}, year={2010}, month={May}, pages={1426–1436} }
 @inproceedings{lazzi_2009, title={Computational and experimental bioelectromagnetics for a retinal prosthesis}, booktitle={ICEAA: 2009 International Conference on Electromagnetics in Advanced Applications, vols 1 and 2}, author={Lazzi, G.}, year={2009}, pages={978–980} }
 @article{so_thelen_qusba_hayes_lazzi_dickey_2009, title={Reversibly Deformable and Mechanically Tunable Fluidic Antennas}, volume={19}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.200900604}, abstractNote={Abstract}, number={22}, journal={ADVANCED FUNCTIONAL MATERIALS}, publisher={Wiley}, author={So, Ju-Hee and Thelen, Jacob and Qusba, Amit and Hayes, Gerard J. and Lazzi, Gianluca and Dickey, Michael D.}, year={2009}, month={Nov}, pages={3632–3637} }
 @article{singh_qusba_roy_castro_mcclure_dai_greenberg_weiland_humayun_lazzi_2009, title={Specific Absorption Rate and Current Densities in the Human Eye and Head Induced by the Telemetry Link of an Epiretinal Prosthesis}, volume={57}, ISSN={["1558-2221"]}, DOI={10.1109/TAP.2009.2028498}, abstractNote={The fields induced in the human head by the wireless telemetry used for Second Sight Medical Product, Inc.'s epiretinal prosthesis system are characterized for compliance testing with international safety standards using a three-dimensional (3-D) finite-difference time-domain (FDTD) code in D-H formulation. The specific system under consideration utilizes an inductive link with a primary coil mounted on the subject's eyeglasses and a secondary coil that is strapped on the eye, over the sclera. The specific absorption rate (SAR) and the current density have been obtained computationally for different relative positions of the primary and secondary coils to account for the relative misalignment of the two due to the movement of the eye with the implant. For a peak normalized current of 0.62 A in the primary coil at 10 MHz, the highest peak 1-g SAR was found to be 0.45 W/Kg, and the maximum root mean square (rms) current density averaged over a 1-cm2 area was found to be 16.05 A/m2, both of which are within the limits imposed by IEEE and ICNIRP safety standards. Simulations between 2 and 20 MHz indicated that the induced electric field values scale well with frequency, thus providing guidelines for the determination of the final frequency and input power requirements of operation for the telemetry system to meet safety standards.}, number={10}, journal={IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION}, author={Singh, Vinit and Qusba, Amit and Roy, Arup and Castro, Richard A. and McClure, Kelly and Dai, Rongching and Greenberg, Robert J. and Weiland, James D. and Humayun, Mark S. and Lazzi, Gianluca}, year={2009}, month={Oct}, pages={3110–3118} }
 @article{soora_gosalia_humayun_lazzi_2008, title={A comparison of two and three dimensional dipole antennas for an implantable retinal prosthesis}, volume={56}, ISSN={["0018-926X"]}, DOI={10.1109/tap.2008.916889}, abstractNote={The feasibility is investigated using three dimensional folded dipole antennas as a data-telemetry implantable receiving antenna in a dual-unit retinal prosthesis to restore partial vision to the blind. Three dimensional designs are explored in an effort to enhance certain antenna characteristics such as bandwidth and maximum gain while reducing the planar footprint size in comparison to its two dimensional equivalent. The current vector alignment between the three dimensional layers are examined through folding and rotating the dipole arms with respect to each other to fully optimize the antenna's characteristics. The performance of the 2D and 3D antennas were compared in simulations and further examined by fabricating and characterizing the performance in a transmit/ receive system in air and inside eye phantoms. Results show that three-dimensional antennas can provide larger bandwidth while being physically smaller than the correspondent two-dimensional ones, thus providing larger channel capacity that could lead to a system with an increased number of stimulating electrodes.}, number={3}, journal={IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION}, author={Soora, Shruthi and Gosalia, Keyoor and Humayun, Mark S. and Lazzi, Gianluca}, year={2008}, month={Mar}, pages={622–629} }
 @inproceedings{srinivas_george_lazzi_2008, title={Finite difference formulation to calculate the induced current density profile inside the retina by a microcoil array}, ISBN={978-1-4244-2041-4}, booktitle={2008 IEEE International Symposium on Antennas and Propagation and USNC/URSI National Radio Science Meeting}, publisher={[Piscataway, NJ]: IEEE}, author={Srinivas, S. and George, J. S. and Lazzi, G.}, year={2008}, pages={3074–3077} }
 @article{dong_hughes_lazzi_2008, title={Mutual Coupling Effects in MIMO MRC Systems with Limited Feedback}, ISSN={["1930-529X"]}, DOI={10.1109/glocom.2008.ecp.692}, abstractNote={We consider the impact of transmitter correlation, mutual coupling and matching networks on the design and performance of MIMO MRC systems with limited feedback. We present codebook design techniques for three measures of transmitted power and we investigate the impact of antenna matching on the performance of these codebooks. Numerical results suggest that, regardless of the power measure and matching networks, the benefits of MIMO MRC with limited feedback can be achieved with antennas spaced as close as 0.2 - 0.3 wavelengths apart.}, journal={GLOBECOM 2008 - 2008 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE}, author={Dong, Yuhan and Hughes, Brian L. and Lazzi, Gianluca}, year={2008} }
 @article{gupta_hughes_lazzi_2008, title={On the degrees of freedom in linear array systems with tri-polarized antennas}, volume={7}, ISSN={["1558-2248"]}, DOI={10.1109/TWC.2008.070160}, abstractNote={In this paper, we provide a theoretical, simulation and experimental characterization of the performance of linear arrays of tri-polarized dipole antennas in multiple input multiple output (MIMO) systems in terms of degrees of freedom and channel capacity. Specifically, we formulate three distinct approaches, theoretical and experimental, that lead to the conclusion that linear arrays of tri-polarized dipole antennas employed at the transmit and receive end of a MIMO system can achieve a three-fold increase in channel capacity with respect to analogous arrays of linearly polarized antennas.}, number={7}, journal={IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS}, author={Gupta, Gaurav and Hughes, Brian L. and Lazzi, Gianluca}, year={2008}, month={Jul}, pages={2458–2462} }
 @inproceedings{lazzi_qusba_singh_2008, title={On the design of telemetry coils and implantable small antennas for a retinal prosthesis to restore partial vision to the blind}, ISBN={978-1-4244-2041-4}, booktitle={2008 IEEE International Symposium on Antennas and Propagation and USNC/URSI National Radio Science Meeting}, publisher={[Piscataway, NJ]: IEEE}, author={Lazzi, G. and Qusba, A. and Singh, V.}, year={2008}, pages={592–594} }
 @inproceedings{gupta_rajagopalan_pourdeyhimi_lazzi_2008, title={On the use of vector antennas embedded on fabric as frequency selective surfaces}, ISBN={978-1-4244-2041-4}, DOI={10.1109/aps.2008.4619220}, abstractNote={In this paper a three element vector antenna (two orthogonal dipoles and a square loop) was proposed for use in FSSs. A prototype design working at 8 GHz was tested. Measurement results show that vector antennas provide a higher mean signal energy (MSE) as compared to conventional dipole antennas. The multiple signatures are obtained when using loop and dipole antennas at the transceiver. These multiple signatures can be combined to provide even higher MSE ( ap4 dB) as compared to the system with two dimensional dipole array and dipole transceiver. The vector antenna system is also more resistant to misalignment with the transceiver.}, booktitle={2008 IEEE International Symposium on Antennas and Propagation and USNC/URSI National Radio Science Meeting}, publisher={[Piscataway, NJ]: IEEE}, author={Gupta, G. and Rajagopalan, A. and POURDEYHIMI, BEHNAM and Lazzi, G.}, year={2008}, pages={1208–1211} }
 @article{domizioli_hughes_gard_lazzi_2008, title={Optimal Front-End Design for MIMO Receivers}, ISSN={["1930-529X"]}, DOI={10.1109/glocom.2008.ecp.717}, abstractNote={The effect of antenna mutual coupling on fading correlation in compact MIMO arrays has received considerable attention. By contrast, relatively little attention has been paid to the noise. In this paper we present a circuit model for a noisy MIMO receiver front-end that includes arbitrary coupling and noise correlation. The noise figure for two-port networks is extended to multiport networks, from which theorems for optimal front-end design are derived. Numerical results are presented which provide insight into receiver noise behavior in the presence of coupled antennas.}, journal={GLOBECOM 2008 - 2008 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE}, author={Domizioli, Carlo P. and Hughes, Brian L. and Gard, Kevin G. and Lazzi, Gianluca}, year={2008} }
 @article{rajagopalan_gupta_konanur_hughes_lazzi_2007, title={Increasing channel capacity of an ultrawideband MIMO system using vector antennas}, volume={55}, ISSN={["0018-926X"]}, DOI={10.1109/TAP.2007.905938}, abstractNote={Recently it was shown that co-located vector antennas can provide the same capacity increase as spatial array antennas in multiple-input multiple-output (MIMO) systems. This paper describes the design of a vector antenna consisting of a loop antenna and two orthogonal bowtie antennas for a ultrawideband (UWB) MIMO system that operates in the frequency range 3.6-8.5 GHz. Channel capacity calculations performed with the antenna operating in a rich scattering environment show that spectral efficiency of the UWB vector antenna system approaches that of the traditional spatial array. This demonstrates that vector antennas can be used in place of spatial arrays where compact UWB multiantenna systems are needed.}, number={10}, journal={IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION}, author={Rajagopalan, Ajit and Gupta, Gaurav and Konanur, Anand S. and Hughes, Brian and Lazzi, Gianluca}, year={2007}, month={Oct}, pages={2880–2887} }
 @article{buff_steer_lazzi_2006, title={Cole-Cole dispersion models for aqueous gelatin-syrup dielectric composites}, volume={44}, ISSN={["0196-2892"]}, DOI={10.1109/TGRS.2005.861409}, abstractNote={A dielectric composite is developed with permittivity ranging from 8 to 75 with selectable conductive and dielectric losses. The composite comprises gelatin, high fructose corn syrup (HFCS), NaCl, and water, and can be used to model soils, loams, and sands in the 200-MHz to 20-GHz range. A single-term Cole-Cole dispersion equation is developed with frequency-independent parameters being functions of component concentrations. Fits are provided for various soil samples and surrogate concentrations.}, number={2}, journal={IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING}, author={Buff, PM and Steer, MB and Lazzi, G}, year={2006}, month={Feb}, pages={351–355} }
 @article{xiao_kim_lazzi_zavada_2006, title={Tunable waveguiding in electrically programmable VO2-based photonic crystals}, volume={99}, ISSN={["1089-7550"]}, DOI={10.1063/1.2200873}, abstractNote={The feasibility of electrically programmable waveguiding in a photonic crystal (PC) is explored based on the metal-insulator transition of vanadium dioxide (VO2). Unlike the ordinary PCs, wave propagation in the desired structure may be switched on/off or redirected by applying an electrical bias on the selective electrodes by taking advantage of the electrically induced VO2 phase transition and subsequent modulation of dielectric properties. The characteristics of the two-dimensional VO2-based PCs with line defects are analyzed using the iterative plane wave and finite difference time domain methods. Particularly, the influence of the Drude relaxation on waveguiding is examined as the high rate typical for metallic VO2 can lead to the signal loss. An optimized structure is proposed to minimize the loss and simplify the fabrication.}, number={11}, journal={JOURNAL OF APPLIED PHYSICS}, author={Xiao, D. and Kim, K. W. and Lazzi, G. and Zavada, J. M.}, year={2006}, month={Jun} }
 @article{gosalia_humayun_lazzi_2005, title={Impedance matching and implementation of planar space-filling dipoles as intraocular implanted antennas in a retinal prosthesis}, volume={53}, ISSN={["1558-2221"]}, DOI={10.1109/TAP.2005.852514}, abstractNote={In this work, an extremely compact planar meander line dipole is designed and implemented for use as an intraocular element in a retinal prosthesis. This planar meander dipole antenna exhibits a high degree of current vector alignment and is impedance matched by inducing a current phase reversal along its length. This current phase reversal is induced by a minor offset in feed location which yields a highly directive broadside radiation pattern on this particular planar antenna geometry. This concept is applied in designing and implementing a 6/spl times/6 mm planar compact wire dipole at 1.4 GHz as the intraocular element for the data telemetry link of a retinal prosthesis. Coupling measurements between an external microstrip patch antenna and the intraocular wire dipole are presented and compared with those obtained with intraocular microstrip patch antennas in place of the wire dipole. It is demonstrated that such compact meander dipoles can perform better than previously reported microstrip patch antennas as intraocular elements for a retinal prosthesis.}, number={8}, journal={IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION}, author={Gosalia, K and Humayun, MS and Lazzi, G}, year={2005}, month={Aug}, pages={2365–2373} }
 @article{konanur_gosalia_krishnamurthy_hughes_lazzi_2005, title={Increasing wireless channel capacity through MIMO systems employing co-located antennas}, volume={53}, ISSN={["1557-9670"]}, DOI={10.1109/TMTT.2005.848105}, abstractNote={Wireless networks consisting of compact antennas find applications in diverse areas such as communication systems, direction of arrival estimation, sensor networks, and imaging. The effectiveness of many of these systems depend on maximizing the reception of RF power and extracting maximum information from the incident electromagnetic (EM) wave. Traditionally, this has been achieved through multiple-input multiple-output (MIMO) systems employing a spatial array of antennas that enhance the channel capacity. In this paper, we report similar increases in channel capacity obtained through the use of vector antennas consisting of co-located loops and dipoles, which can respond to more than one component of the EM field. It is shown that systems with three- and four-element vector antennas at both the transmitter and receiver operating around the frequency of 2.25 GHz support three and four times more information, respectively, as compared to conventional systems consisting of sensors with single antennas. Comparison with a simplified theoretical model of a MIMO system with co-located antennas in a rich multipath environment shows good agreement.}, number={6}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Konanur, AS and Gosalia, K and Krishnamurthy, SH and Hughes, B and Lazzi, G}, year={2005}, month={Jun}, pages={1837–1844} }
 @article{lazzi_2005, title={Thermal effects of bioimplants}, volume={24}, ISSN={["0739-5175"]}, DOI={10.1109/MEMB.2005.1511503}, abstractNote={Implantable devices are well on the way to becoming small, dedicated, and highly complex embedded systems. As such, they are plagued by the same thermal management problems that afflict the computer industry: increased functionality causes increased heat generation. Herein, the effects of various parameters on the temperature increase in the human body tissue are considered, with a focus on a specific proposed implant: a dual-unit retinal prosthesis to restore partial vision to the blind . This particular example is educative since it includes most of the potential causes of thermal dissipation: a microchip that could dissipate relatively large power, a telemetry system, and a potentially large number of stimulating electrodes. The power dissipation characteristics of implanted electronic systems will have increasing importance for the design of future implantable devices. It was shown in this article that in some cases, this power dissipation can lead to temperature increases in the human tissue that are not negligible. In particular, the design of implantable stimulating devices with a large number of stimulating channels must be performed with a clear idea of the potential thermal implications of the device. Fortunately, reliable numerical and experimental methods are available to characterize the temperature increase caused by the implantable device. These methods should be used during the design phase of these devices.}, number={5}, journal={IEEE ENGINEERING IN MEDICINE AND BIOLOGY MAGAZINE}, author={Lazzi, G}, year={2005}, pages={75–81} }
 @article{gosalia_lazzi_humayun_2004, title={Investigation of a microwave data telemetry link for a retinal prosthesis}, volume={52}, ISSN={["1557-9670"]}, DOI={10.1109/TMTT.2004.832007}, abstractNote={In this paper, we investigate a novel approach of establishing a data telemetry link for a dual-unit retinal prosthesis at microwave frequencies (1.45 and 2.45 GHz) using a pair of microstrip patch antennas. Appropriately sized extraocular (25/spl times/25 mm) and intraocular (6/spl times/6 mm) antennas are designed to operate at both the frequencies using the finite-difference time-domain method, and the coupling between them is examined computationally in the presence of a 0.25-mm resolution human-head model. Good agreement between numerical and experimental coupling results is shown and it is observed that the eyeball acts as a dielectric lens for the implanted antenna, thus improving the coupling between the extraocular and intraocular antennas. Specific absorption rate (SAR) computations are also performed at both the frequencies, and the peak 1-g SAR value is calculated. Detailed analysis of the design issues of the antennas, results of the numerical and experimental coupling measurements, and SAR calculations are presented.}, number={8}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Gosalia, K and Lazzi, G and Humayun, M}, year={2004}, month={Aug}, pages={1925–1933} }
 @article{lazzi_gandhi_ueno_2004, title={Special issue on medical applications and biological effects of RF/microwaves - Guest editorial}, volume={52}, ISSN={["0018-9480"]}, DOI={10.1109/TMTT.2004.832682}, number={8}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Lazzi, G and Gandhi, OP and Ueno, S}, year={2004}, month={Aug}, pages={1853–1855} }
 @article{gosalia_weiland_humayun_lazzi_2004, title={Thermal elevation in the human eye and head due to the operation of a retinal prosthesis}, volume={51}, DOI={10.1109/TMBE.2004.827548}, number={8}, journal={IEEE Transactions on Biomedical Engineering}, author={Gosalia, K. and Weiland, J. and Humayun, M. and Lazzi, G.}, year={2004}, pages={1469–1477} }
 @article{schmidt_lazzi_2004, title={Use of the FDTD thin-strut formalism for biomedical telemetry coil designs}, volume={52}, ISSN={["1557-9670"]}, DOI={10.1109/TMTT.2004.832019}, abstractNote={The finite-difference time-domain (FDTD) method extended by thin-strut formalism was used to study the current coupling between rectangular coils for use in biomedical telemetry links. Further, a new stability condition, different from the Courant-Friedrichs-Lewy stability limit, was derived for the thin-strut method. Results obtained for varying coil sizes and distances of separation show that the thin-strut FDTD formulation, applied to the calculation of current coupling between telemetry coils, is in closer agreement to the analytical approximation than is the standard FDTD code. These results indicate that the thin-strut method is a promising method for the study and the design of coils for telemetry links between implantable and external devices.}, number={8}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Schmidt, S and Lazzi, G}, year={2004}, month={Aug}, pages={1952–1956} }
 @article{ozkar_lazzi_mortazawi_2003, title={A modified unsplit PML formulation for evanescent mode absorption in waveguides}, volume={13}, ISSN={["1531-1309"]}, DOI={10.1109/LMWC.2003.814109}, abstractNote={In this letter, a modified unsplit perfectly matched layer (PML) formulation for the absorption of evanescent waves in waveguides is presented. The proposed formulation combines the advantages of the stretched coordinate and unsplit D - E - H PML formulations, which separates PML conductivities from the properties of the physical materials in the FDTD mesh. Results show that the proposed boundary outperforms the traditional unsplit PML in the evanescent region by 20 to 40 dB.}, number={6}, journal={IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS}, author={Ozkar, M and Lazzi, G and Mortazawi, A}, year={2003}, month={Jun}, pages={220–222} }
 @article{demarco_liu_singh_lazzi_humayun_weiland_2003, title={An arbitrary waveform stimulus circuit for visual prostheses using a low-area multibias DAC}, volume={38}, ISSN={["0018-9200"]}, DOI={10.1109/JSSC.2003.817264}, abstractNote={Attempts are underway to construct a retinal prosthesis to recover limited vision for blind patients with retinitis pigmentosa using implantable electronic devices. These microchips provide electrical stimulation to damaged retinal tissues using an array of stimulus circuits. This paper describes improvements to conventional circuit designs with significantly decreased implementation area and the ability to support arbitrary stimulus waveforms where an array of such stimulus circuits is required. This yields greater spatial resolution in stimulation owing to more stimulus circuits per chip area. Also introduced are digital-to-analog converter gain prescalar and dc-offset circuits which tune the stimulus circuits to an optimally effective range due to variation in retinal degradation. The prototype chip was fabricated by MOSIS in 1.2-/spl mu/m CMOS technology.}, number={10}, journal={IEEE JOURNAL OF SOLID-STATE CIRCUITS}, author={DeMarco, SC and Liu, WT and Singh, PR and Lazzi, G and Humayun, MS and Weiland, JD}, year={2003}, month={Oct}, pages={1679–1690} }
 @article{demarco_lazzi_liu_weiland_humayun_2003, title={Computed SAR and thermal elevation in a 0.25-mm 2-D model of the human eye and head in response to an implanted retinal stimulator - Part I: Models and methods}, volume={51}, ISSN={["1558-2221"]}, DOI={10.1109/TAP.2003.816395}, abstractNote={Retinitis pigmentosa and age-related macular degeneration lead to blindness through progressive loss of retinal photoreceptors. Attempts are under way to construct a visual prosthesis to recover a limited sense of vision for these patients with the aid of implantable electronic devices. The function of these microchips is to provide electrical stimulation to existing viable retinal tissues - living ganglion and bipolar cells - using an array of on-chip stimulus circuits, while the dominant mechanism for power and data communication for these implanted devices has been wireless inductive telemetry using coils. This paper describes methods and models used to estimate the heating induced in the human eye and surrounding head tissues subject to the operation of this retinal prosthesis. A two-dimensional 0.25-mm high-resolution human head model has been developed with the aid of a new semiautomatic graphical segmentation algorithm. Finite-difference-based numerical methods for both electromagnetic and thermal modeling have been used to determine the influence of the specific absorption rate (associated with 2-MHz inductive coupling to the implant) and of stimulator integrated circuit (IC) power on tissue heating under different operational conditions and different hypothesis on choroidal blood flow and properties of the complex implanted circuitry. Results, provided in Part II of this paper, show that temperature increases of approximately 0.6 and 0.4/spl deg/C are induced in the midvitreous of the human eye in the absence and presence of choroidal blood flow, respectively, for a 60-electrode retinal prosthesis chip. Correspondent temperature rises of approximately 0.19 and 0.004/spl deg/C on the retina are obtained for these cases. Comparison with in vivo experimental measurements on intraocular heating in dog eyes shows good agreement.}, number={9}, journal={IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION}, author={DeMarco, SC and Lazzi, G and Liu, WT and Weiland, JD and Humayun, MS}, year={2003}, month={Sep}, pages={2274–2285} }
 @article{lazzi_demarco_liu_weiland_humayun_2003, title={Computed SAR and thermal elevation in a 0.25-mm 2-D model of the human eye and head in response to an implanted retinal stimulator - Part II: Results}, volume={51}, ISSN={["0018-926X"]}, DOI={10.1109/TAP.2003.816394}, abstractNote={Retinitis pigmentosa and age-related macular degeneration lead to blindness through progressive loss of retinal photoreceptors. Attempts are under way to construct a visual prosthesis to recover a limited sense of vision for these patients with the aid of implantable electronic devices. The function of these microchips is to provide electrical stimulation to existing viable retinal tissues—living ganglion and bipolar cells—using an array of on-chip stimulus circuits, while the dominant mechanism for power and data communication for these implanted devices has been wireless inductive telemetry using coils. This paper describes methods and models used to estimate the heating induced in the human eye and surrounding head tissues subject to the operation of this retinal prosthesis. A two-dimensional 0.25-mm high-resolution human head model has been developed with the aid of a new semiautomatic graphical segmentation algorithm. Finite-difference-based numerical methods for both electromagnetic and thermal modeling have been used to determine the influence of the specific absorption rate (associated with 2-MHz inductive coupling to the implant) and of stimulator integrated circuit (IC) power on tissue heating under different operational conditions and different hypothesis on choroidal blood flow and properties of the complex implanted circuitry. Results, provided in Part II of this paper, show that temperature increases of approximately 0.6 and 0.4 C are induced in the midvitreous of the human eye in the absence and presence of choroidal blood flow, respectively, for a 60-electrode retinal prosthesis chip. Correspondent temperature rises of approximately 0.19 and 0.004C on the retina are obtained for these cases. Comparison with in vivo experimental measurements on intraocular heating in dog eyes shows good agreement.}, number={9}, journal={IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION}, author={Lazzi, G and DeMarco, SC and Liu, WT and Weiland, JD and Humayun, MS}, year={2003}, month={Sep}, pages={2286–2295} }
 @article{schmidt_lazzi_2003, title={Extension and validation of a perfectly matched layer formulation for the unconditionally stable D-H FDTD method}, volume={13}, ISSN={["1558-1764"]}, DOI={10.1109/LMWC.2003.815693}, abstractNote={In this letter, a modification to the recently proposed unconditionally stable D-H ADI FDTD method is presented that considerably reduces the late-time error induced by the corner cells. The PML boundary is derived from the direct discretization of the modified D-H Maxwell's equations rather than the superposition of uniaxial PML boundaries. An optimal choice of the PML conductivity profile coefficients is proposed. Results show that the reflection error of the PML is limited for increased time step size beyond the Courant-Friedrichs-Lewy stability bound, and maximum reflection errors are 15 to 20 dB lower than the original formulation.}, number={8}, journal={IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS}, author={Schmidt, S and Lazzi, G}, year={2003}, month={Aug}, pages={345–347} }
 @article{gosalia_lazzi_2003, title={Reduced size, dual-polarized microstrip patch antenna for wireless communications}, volume={51}, ISSN={["1558-2221"]}, DOI={10.1109/TAP.2003.816344}, abstractNote={A novel, compact, probe-fed microstrip patch antenna for operation in dual-polarization mode is proposed. The novel design is achieved by etching out a symmetric pattern of crossed slots from the surface of a square probe-fed patch. Reduction in patch size of up to 51% with respect to a traditional dual-polarized square patch operating at the same frequency is obtained. Results show linear polarizations in the +45 and -45/spl deg/ with a high isolation of 38 dB between the two ports. Moreover, the 50-/spl Omega/ feed position can be achieved by moving the feed point along the diagonal of the square patch, leading to ease in fabrication.}, number={9}, journal={IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION}, author={Gosalia, K and Lazzi, G}, year={2003}, month={Sep}, pages={2182–2186} }
 @article{eberdt_brown_lazzi_2003, title={Two-dimensional SPICE-linked multiresolution impedance method for low-frequency electromagnetic interactions}, volume={50}, ISSN={["0018-9294"]}, DOI={10.1109/TBME.2003.813534}, abstractNote={A multiresolution impedance method for the solution of low-frequency electromagnetic interaction problems typically encountered in bioelectromagnetics is presented. While the impedance method in its original form is based on the discretization of the scattering objects into equal-sized cells, our formulation decreases the number of unknowns by using an automatic mesh generation method that does not yield equal-sized cells in the modeling space. Results indicate that our multiresolution mesh generation scheme can provide a 50%-80% reduction in cell count, providing new opportunities for the solution of low-frequency bioelectromagnetic problems that require a high level of detail only in specific regions of the modeling space. Furthermore, linking the mesh generator to a circuit simulator such as SPICE permits the addition of arbitrarily complex passive and active circuit elements to the generated impedance network, opening the door to significant advances in the modeling of bioelectromagnetic phenomena.}, number={7}, journal={IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING}, author={Eberdt, M and Brown, PK and Lazzi, G}, year={2003}, month={Jul}, pages={881–889} }
 @article{margalit_maia_weiland_greenberg_fujii_torres_piyathaisere_o'hearn_liu_lazzi_et al._2002, title={Retinal prosthesis for the blind}, volume={47}, DOI={10.1016/S0039-6257(02)00311-9}, abstractNote={Most of current concepts for a visual prosthesis are based on neuronal electrical stimulation at different locations along the visual pathways within the central nervous system. The different designs of visual prostheses are named according to their locations (i.e., cortical, optic nerve, subretinal, and epiretinal). Visual loss caused by outer retinal degeneration in diseases such as retinitis pigmentosa or age-related macular degeneration can be reversed by electrical stimulation of the retina or the optic nerve (retinal or optic nerve prostheses, respectively). On the other hand, visual loss caused by inner or whole thickness retinal diseases, eye loss, optic nerve diseases (tumors, ischemia, inflammatory processes etc.), or diseases of the central nervous system (not including diseases of the primary and secondary visual cortices) can be reversed by a cortical visual prosthesis. The intent of this article is to provide an overview of current and future concepts of retinal and optic nerve prostheses. This article will begin with general considerations that are related to all or most of visual prostheses and then concentrate on the retinal and optic nerve designs. The authors believe that the field has grown beyond the scope of a single article so cortical prostheses will be described only because of their direct effect on the concept and technical development of the other prostheses, and this will be done in a more general and historic perspective..}, number={4}, journal={Survey of Ophthalmology}, author={Margalit, E. and Maia, M. and Weiland, J. D. and Greenberg, R. J. and Fujii, G. Y. and Torres, G. and Piyathaisere, D. V. and O'Hearn, T. M. and Liu, W. T. and Lazzi, G. and et al.}, year={2002}, pages={335–356} }
 @article{lazzi_2001, title={Unconditionally stable D-H FDTD formulation with anisotropic PML boundary conditions}, volume={11}, ISSN={["1531-1309"]}, DOI={10.1109/7260.916326}, abstractNote={An unconditionally stable finite difference time domain (FDTD) method based on a D-H formulation and the recently proposed alternating-direction-implicit (ADI) marching scheme is presented. The advantage of the D-H algorithm over the conventional E-H is the possibility to easily implement an unsplit field components formulation of the PML absorbing boundary condition that is independent from the background material used in the FDTD grid. The method allows therefore immersing any dielectric in the PML layers without any special consideration, and is amenable for models truncation often used in biomedical simulations. Furthermore, the proposed scheme can be extended to account for frequency dispersive dielectrics.}, number={4}, journal={IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS}, author={Lazzi, G}, year={2001}, month={Apr}, pages={149–151} }
 @article{lazzi_gandhi_2000, title={A mixed FDTD-integral equation approach for on-site safety assessment in complex electromagnetic environments}, volume={48}, ISSN={["0018-926X"]}, DOI={10.1109/8.901271}, abstractNote={A mixed finite-difference time-domain (FDTD)-integral equation approach for the evaluation of the power deposition in the human body model immersed in a complex electromagnetic environment is proposed. The advantage of the proposed approach is that safety assessment for exposure to generic sources may be performed on-site, in a few minutes, with high accuracy and without the need of a high-power workstation. The method uses previously stored FDTD-computed impulse responses (Green's functions) of the human body model by integrating them with the complex incident electromagnetic field distribution that can be measured on site. The application of this method to the dosimetry of cellular telephone base station antennas is presented to show its versatility and ease of use.}, number={12}, journal={IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION}, author={Lazzi, G and Gandhi, OP}, year={2000}, month={Dec}, pages={1830–1836} }
 @article{lazzi_gandhi_sullivan_2000, title={Use of PML absorbing layers for the truncation of the head model in cellular telephone simulations}, volume={48}, number={11 pt.2}, journal={IEEE Transactions on Microwave Theory and Techniques}, author={Lazzi, G. and Gandhi, O. P. and Sullivan, D. M.}, year={2000}, pages={2033–2039} }