2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)最新文献

{"title":"Single level fast multipole method on GPU cluster for electromagnetic problems","authors":"V. Dang, Q. Nguyen, O. Kilic, E. El-Araby","doi":"10.1109/USNC-URSI-NRSM.2013.6525071","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6525071","url":null,"abstract":"Fast Multipole Method (FMM) is a mathematical technique which was developed to seek rapid solutions to integral equations of scattering for Helmholtz problems. For scattering problems, the integral equation is discretized into a matrix equation by the method of moments (MoM). The resultant equation is then typically solved by the direct LU, or an iterative method which requires O(N3) or O(N2) floating point operations respectively. However, if FMM is implemented, the complexity is reduced to O(N3/2). Moreover, the multilevel fast multipole algorithm (MLFMA) which is a multistage FMM can further reduce the complexity to O(NlogN). These methods are promising for providing a path to large scale computing in electromagnetics.In this paper, the exploitation of an HPC GPU cluster to implement single level fast multipole method for large scale scattering problems is investigated. The NVIDIA's Compute Unified Device Architecture (CUDA) and MVAPICH2 programming environments are utilized on a 13-node cluster equipped with GPUs and interconnected through a high bandwidth, low latency Infiniband network.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129063033","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rationale for reverberation chamber testing","authors":"V. Rajamani, C. Bunting, G. Freyer","doi":"10.1109/USNC-URSI-NRSM.2013.6525046","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6525046","url":null,"abstract":"Summary form only given. Several test facility options for conducting electromagnetic compatibility testing including immunity, emissions, and shielding effectiveness are available. Generally each facility provides a different test electromagnetic environment. A reverberation chamber is a cavity enclosed by conducting surfaces with a method of exciting modal structure changes within the cavity. The test electromagnetic environment, a superposition of plane waves with random phase, results from repeated reflections from the conducting surfaces. The statistical isotropy, random polarization, and uniform electromagnetic environment of a reverberation chamber permit a robust, all aspect angle test without the requirement for rotation or translation of the equipment-under-test. The reverberation chamber electromagnetic environment provides the correct emulation of the equipment-under-test performance when it operates in a cavity. Many standards permit the use of reverberation chambers as an alternate method for certification. As with every electromagnetic compatibility test technique, reverberation chambers are not a panacea and have disadvantages as well as advantages.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115778564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lightsabers (“laster swords”) for improving photodetector speed and responsivity","authors":"I. Hasan, J. Simpson","doi":"10.1109/USNC-URSI-NRSM.2013.6525093","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6525093","url":null,"abstract":"The micrometer scale of optics is significantly larger than the nanometer scale of modern electronic devices. To produce photodiodes yielding both superior speed and responsivity, a critical challenge is to confine the incident light efficiently to an active region having a small (subwavelength) area. In recent years, plasmonics has been applied as a means to confine light to subwavelength areas. In this case, the plasmonic structure converts the incident (far-field) light into near fields in order to achieve the sub-wavelength confinement. However, the surface plasmons are a near-field phenomenon such that the electromagnetic energy does not penetrate deeply. Further, surface plasmon resonances are generated only over narrow range of frequencies. Thus, the question arises: can we avoid the conversion to near fields and propagate the light into the semiconductor over a sub-wavelength area? When desired, can we propagate broadband electromagnetic energy into the sub-wavelength area to provide efficient broadband photodiodes? The latter may especially be desirable if the common silicon semiconductor is replaced with a more broadband semiconductor such as graphene. Here, it is proposed that a propagating sub-wavelength beam of light called a photonic nanojet and resembling a lightsaber or “laser sword” can be used to focus light onto the small active area of a photodiode. Exploratory three-dimensional, Maxwell's equations finite-difference time-domain (FDTD) simulations are conducted and demonstrate that the nanojets can confine light to an area comparable to a nanostructured dipole antenna while propagating multiple wavelengths into the semiconductor, even over a broad range of frequencies when desirable.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114889196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Radar interferometric imaging using the maximum entropy method for the case of point targets","authors":"Qian Zhu, J. Mathews","doi":"10.1109/USNC-URSI-NRSM.2013.6525102","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6525102","url":null,"abstract":"Summary form only given. The radar interferometry technique was first used at the Jicamarca Radio Observatory by Woodman (1971) for measuring the inclination of geomagnetic field. Since then, this technique has been successfully developed for imaging ionospheric plasma irregularities phenomena (Farley 1981; Kudeki 1987; Hysell 1996; etc.). With this technique, we can obtain the spatial and temporal (image) information of objects at the same time. We explore practical methods to achieve both fine spatial and temporary resolutions for radar imaging of meteor (point target) events. The basic mathematical description of radar interferometric imaging is the linear Fourier transform relationship (Woodman 1997). The complex visibility measurement from one interferometer baseline is a Fourier component of the objects brightness distribution. However, since the observed visibility data (the Fourier coefficients) from radar interfereometry is necessarily incomplete and noisy, in most cases the directly linear inversion is not sufficient to obtain the desired resolution of objects. We need non-linear inversion techniques to remove “ringing” effects and obtain details that are not revealed using linear inversion techniques. Among the non-linear inversion techniques, the maximum entropy method has been widely used in many fields (e.g., radio astronomy, etc.) to reconstruct images of objects. According to the comparisons between maximum entropy method and other conventional inversion methods (CLEAN, etc.) from many papers, we believe maximum entropy method is an optimal choice to achieve satisfactory reconstructions from incomplete and noisy data. Therefore, for meteor head-echoes modeling purposes, a discrete linear radar interferometric signal model is derived, and a maximum entropy image reconstruction method based on Newton-Raphson technique is applied to point targets. Its advantages and limitations are discussed.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126966058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A investigation on the correlation-coefficient and power metrics for MIMO antennas in a reverberation chamber","authors":"N. Janssen, W. Young, C. Holloway, K. Remley","doi":"10.1109/USNC-URSI-NRSM.2013.6525047","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6525047","url":null,"abstract":"Many MIMO antenna specifying aspects have been investigated. These aspects include capacity, diversity gain, BER between multiple antennas, K-factor and their mutual relations in both a reverberation chamber and an anechoic chamber. In this presentation, the correlation-coefficient (ρCC) of the transmission coefficients will be compared to the complex transmission-coefficient squared (TCS) by investigating the behavior of the coefficient of variance (Cv) for the two measures. The Cv is calculated by normalizing the standard deviation by the mean for the different positions in the reverberation chamber. The transmission coefficients S13 and S23 are obtained from a three-port vector network analyzer measurement done between two monopole antennas (connected on ports 1 and 2, on a single ground-plane) and a brass-horn antenna (on port 3). Three sets of monopoles are at fixed separation distances on a ground plane (called fix separation parallel-monopole antenna (FSPA)), and are representative of good, bad, and average multiple-input multiple-output (MIMO) antenna's. Another antenna with an adjustable separation distance between the monopoles (called variable separation parallel-monopole antenna (VSPA)), allows variation of the MIMO antenna over a range from good to bad. For both types of MIMO antennas, the ρCC as function of the monopole separation follows the trend of the analytic model (Bessel-function). The ρCC is better (i.e., a smaller value) at larger separations as can be seen in Figure 1a and 1b. With increasing separation the Cv increases to values of approximately 0.4 to 0.5, which implies that the ρCC is becoming less accurate. However, if we look at the case were there are 6 typical RF absorbers-sections added for loading, the Cv of the TCS almost doubles while the Cv of the ρCC stays more-or-less the same. In conclusion, for a small separation between the monopoles, especially in a heavily loaded environment, the ρCC would likely exhibit less uncertainty as a performance metric for a MIMO system, than the TCS measurement.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"82 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123081841","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microwave dielectric properties of brown adipose tissue (BAT)","authors":"E. Colebeck, E. Topsakal","doi":"10.1109/USNC-URSI-NRSM.2013.6525127","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6525127","url":null,"abstract":"Brown adipose tissue (BAT) is prevalent in mammals that lack the capability to produce enough heat to stay warm due to their surroundings, i.e. shivering. This form of thermogenisis is found in new born children, and while it was believed to change into a type of white adipose tissue by adulthood, BAT has been discovered along the neck and torso in adults. While occurrence of BAT in adults is limited, its presence is becoming better known. Unlike white adipose tissue, BAT contains a significant amount of mitochondria, which leads to the browning in color. The mitochondria assist in converting high amounts of glucose and lipids into the necessary heat for the individual to stay warm. Not only does this conversion provide heat, it also provides assistance in increasing metabolic output. Several recent studies proposed the possibility of manipulating BAT to reverse the obesity in adults. One big challenge in developing drugs to stimulate BAT is that there is no technology available to continuously monitor its activity. To overcome this challenge, in collaboration with our colleagues from Duke Medical School, we are currently designing a small radiometer to continuously monitor temperatures at the BAT site in the body. Because the radiometer operates at microwave frequencies, the design requires the knowledge of BAT microwave electrical properties. Thus, in this study, we performed microwave dielectric property measurements of BAT samples extracted from rats between 500 MHz and 20 GHz. We used Agilent 85070 E dielectric slim form probe, a fiber optic temperature probe, and a water bath. The tissues dielectric properties are measured at a temperature range from 25 °C to 45 °C. Based on these measurements, we have developed first- and second-order cole-cole models. We will present dielectric constant, electrical conductivity and cole-cole model data over the frequency range of interest.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"114 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131557370","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spectral encoding of spatial frequency approach for imaging and characterization of 3D structures","authors":"S. Uttam, S. Alexandrov, R. Bista, Yang Liu","doi":"10.1109/USNC-URSI-NRSM.2013.6525015","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6525015","url":null,"abstract":"Probing the internal 3D structure of label-free objects, such as biological cells and tissues in their natural environments, with nano-scale accuracy and sensitivity is of great importance in many biomedical applications. Using the 3D scattering potential description of an object's structure, we present the principle of spectral encoding of 3D spatial frequency (SESF) that encodes different spatial frequencies of the scattering potential into corresponding wavelengths. The SESF principle allows us to (1) perform real-time quantitative dominant-structure imaging of a label-free object. This imaging approach produces a color map in real time in which dominant axial spatial period (or frequency) at each image point is encoded as a corresponding spectral color. We demonstrate the efficacy of real-time imaging using model systems and show the potential of this technique to detect dominant structural changes in pre-cancerous cells that are not visible using conventional microscopy. (2) We extend the SESF principle to measure the entire axial spatial period distribution for each image point. Experimental results based on characterization of cell cycle phases are presented along with comparison with structural information extracted from TEM cell images. (3) Finally, we present spectral tomographic imaging (STI), a new SESF-based integrated tomographic approach that is able to simultaneously reconstruct the 3D object with sub-micron resolution, and also provide spatially-resolved characterization of its structure that has the ability to construct local axial spatial period distribution for any 3D sub-region of interest within the object. Simulation-based examples are presented. In all three cases structural characterization is achieved with nanoscale sensitivity and accuracy.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122324000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analysis of non-linear magnetic core for magnetic neural stimulators","authors":"A. K. RamRakhyani, G. Lazzi","doi":"10.1109/USNC-URSI-NRSM.2013.6524984","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6524984","url":null,"abstract":"Magnetic stimulation is a non-invasive technique to stimulate the central and peripheral nervous system. Using time-varying magnetic fields, a magnetic stimulator induces eddy currents in the tissue to achieve neural excitation (M. Yamaguchi et. al., JAP'89). Due to a non-invasive technique, it has been used in a variety of clinical applications which include brain mapping, treatment of mood disorder, treatment of epilepsy, and treatment of chronic pain. Traditionally, magnetic stimulators consume high power and cause significant heat dissipation in the coil. Thus, use to these devices has been limited to transcranial magnetic stimulation (TMS) only.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"71 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121476397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Real time assimilative foF2 maps for IRI","authors":"B. Reinisch, Xueqin Huang, I. Galkin, D. Bilitza","doi":"10.1109/USNC-URSI-NRSM.2013.6525132","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6525132","url":null,"abstract":"Ionospheric models are mostly unable to correctly predict the effects of space weather events on the ionosphere. This is especially true for the International Reference Ionosphere (IRI) which by design is a monthly median (climatologic) model (Bilitza et al., J. Geodesy, 85, 909-920, 2011). The IRI electron density profile is critically dependent on the correct values of the F2 layer peak height and density, hmF2 and NmF2 (or foF2). For the ionospheric characteristics IRI uses predictions based on CCIR/URSI coefficients (W. B. Jones and R. M. Gallet, ITU Telecomm. J. 29(5), 129-149, 1962) that were derived from the monthly median values of hourly ionosonde measurements. The diurnal variation of the foF2 characteristic, for example, is presented by the Fourier series foF2(T,φ,λ,χ)=a₀(φ,λ,χ) + Σ_n=1⁶ (a_n(φ,λ,χ)cos nT + b_n(φ,λ,χ)sin nT), where T is Universal Time in hours, and φ, λ, χ are the geographic latitude, longitude, and modified dip latitude, respectively. The coefficients a_n and b_n are in turn expanded as functions φm λ, χ resulting in a set of 24 global maps of 988 coefficients each, one for each month of the year and for two levels of solar activity, R₁₂=10 and 100, where R₁₂ is the 12-month running-mean of the monthly sunspot number R_m (2*12*988 = 23,712 coefficients in all) (ITU-R, Information Document on Ionospheric Mapping, Oct. 2011). Real time data from the Digisonde GIRO network (B. W. Reinisch and I. A. Galkin, Earth, Planets and Space, 63(4), 377-381, 2011) can be used to adjust the coefficients to produce more accurate foF2 maps. Adjusting 988 coefficients with merely 42 measured foF2 values is a completely underdetermined problem requiring special techniques (e.g., Galkin et al., Radio Sci., 47, RS0L07, 10 PP, 2012). We have applied the mathematical tool of linear optimization to determine new sets of 988 coefficients that reduce the global deviation of the model prediction from the measured values by a factor of 2.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130711232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Interference mitigation via phase only transmit nulling: Preliminary experimental results","authors":"T. Higgins, T. Webster, A. Shackelford","doi":"10.1109/USNC-URSI-NRSM.2013.6525040","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6525040","url":null,"abstract":"The increasingly crowded RF spectrum necessitates development of techniques that foster coexistence between multiple RF users. Radar systems can typically mitigate received interference using sidelobe cancellation and adaptive beamforming. In the future, radar systems could possibly use similar techniques to produce nulls in the transmit beampattern further reducing RF fratricide. However, transmit nulling is difficult due to the constant modulus constraint associated with the waveforms transmitted by high power radar systems. Several algorithms have been developed that attempt to determine phase only (PO) weights capable of inducing a transmit null. In this talk, the re-iterative uniform weight optimization (RUWO) algorithm is used as a means to produce PO weights from a measured interference covariance matrix.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134086827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}