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

{"title":"Design of opto-electronic nano-structures, capability for optimization of different solar cells","authors":"A. Ghahremani, A. Fathy","doi":"10.1109/USNC-URSI-NRSM.2013.6525094","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6525094","url":null,"abstract":"Development of CAD tools for optical devices is under way to include multi-physics tools. Previously, tools like “RCWA” was used for the diffraction mode of periodic structure analysis, while FDTD is typically used as a general numerical method for analyzing field propagation in the time domain to investigate transmission, reflection, and absorption of electromagnetic energy for devices like optical ring resonators. Meanwhile, for sources it is essential to analyze the semiconductor physics, generation and recombination of electron/hole pairs and the photons generation efficiency linking current to light like in lasers, LEDs, photodiodes, and solar cells.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"17 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":"134474370","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":"Surface and elevated ducts and implications on the modeling of mesoscale NWP refractivity and radio-wave propagation","authors":"A. Kulessa, J. Hacker","doi":"10.1109/USNC-URSI-NRSM.2013.6525089","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6525089","url":null,"abstract":"Summary form only given. Atmospheric processes that involve subsiding or advecting air masses in either littoral environments or large scale subsidence at the top of the boundary layer are often associated with temperature inversions and corresponding decreases in atmospheric moisture content, resulting in the formation of ducts. This paper discusses aircraft measurements carried out in Australia of ducting events caused by various atmospheric processes. From the measurements it is evident that ducting structure results from large changes in atmospheric temperature and water vapour content which are associated with small changes in height. These sharp changes in temperature and humidity produce either elevated or surface ducts with large M-deficits. The situation is rather complicated as the ducting layers can occur at a wide range of altitudes and are usually horizontally inhomogeneous. Recent research has focused attention on the use of meso-scale numerical weather prediction (NWP) models in forecasting the refractive index structure in littoral environments as a means of providing the necessary refractive index input for the computation of radio-wave propagation effects. Investigations show that there is sufficient mesh resolution to effectively calculate the horizontal variations in refractivity over the sea surface, which are due to changing sea surface conditions and unique land features nearby. However the typical mesh size may be too coarse vertically, to adequately predict the refractive index gradients that are often observed. Several propagation scenarios are considered for the observed ducting events and a comparison is made between propagation coverage predictions based upon the actual measured profiles and “under-sampled” versions that may occur in the case of NWP generated refractivity profiles. In some cases, the comparisons are quite different. Simply increasing the vertical grid resolution in the NWP model may not be the best solution to this issue, although a better resolution would no doubt produce more accurate refractive index profiles. However, the use of an adaptive vertical grid in a series of nested model runs, may be worth considering.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"64 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":"133350941","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 performance degradation with in-band OFDM communications system interference","authors":"B. Cordill, S. A. Seguin, L. Cohen","doi":"10.1109/USNC-URSI-NRSM.2013.6525039","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6525039","url":null,"abstract":"Summary form only given. New technology and innovations are giving rise to novel and diverse wireless systems. Unfortunately, as these systems come to fruition worldwide, the already crowded spectrum becomes even more congested due to the high-speed data links offered by systems like WiMAX and LTE. Spectral crowding is acutely problematic in S-Band (2000-4000 MHz), where favorable propagation characteristics make spectrum attractive to both long-range radar and communication systems. The widespread deployment of 4G cellular systems (for example LTE) has the potential to cause widespread interference with existing radar systems, such as those used for weather surveillance. Ideally, these two systems would peacefully coexist in adjacent bands, but the non-constant modulus nature of 4G OFDM waveforms and the relatively high peak-to-average power ratios can lead to intermittent transmitter saturation, resulting in both in-band and adjacent-band interference to a radar receiver. Their intermittent nature and wide bandwidth make interfering OFDM waveforms difficult to eliminate at the radar receiver. The first instinct when dealing with an interfering signal is often to apply a notch filter in an attempt to mitigate the interfering signal's impact on the system. This talk assesses the effectiveness of this instinctive solution. The impact of OFDM interference on a simulated weather radar system is presented, as well as an assessment of the effectiveness of applying a notch filter to mitigate an interfering OFDM signal. As part of this assessment, radar performance data, probability of detection statistics, and receiver operating characteristic (ROC) curves are presented. This type of assessment will help quantify this first instinct solution and help define the trade space for radar system engineers and spectrum managers when considering interference mitigation techniques. Successful mitigation of both in-band and adjacent-channel OFDM interference should not only improve current radar system performance, but it will also allow mission requirements to be met in a crowded spectrum.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"24 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":"114675042","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":"Y-band radar assessment for indoor navigation and mapping","authors":"M. Moallem, K. Sarabandi","doi":"10.1109/USNC-URSI-NRSM.2013.6525115","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6525115","url":null,"abstract":"In this paper, the application of sub-millimeter-wave imaging radars for collision avoidance and navigation of autonomous platforms in indoor environments is investigated. The polarimetric scatter phenomenology of walls and doorways are studied to aid the designing and system specifications of such radar systems. An instrumentation radar operating at 215 GHz is setup to collect backscatter data from corridors in an indoor setting. The backscattered data as a function of azimuth angle are collected while the radar is moved along the corridors. At each radar position, radar range profiles for both vertical and horizontal polarizations as a function of angle are used to form polar images. These images can be generated real time for obstacle-detection and navigation of autonomous robots. It is shown that horizontally polarized incident wave can generate higher backscatter level from smooth walls at steep angles of incidence and thus is the preferred polarization configuration for this application. Using the coordinate radar positions at each point, the polar images at each location are then co-registered in a global coordinate matrix through a “see-and-remember” algorithm to form a complete map of the interior layout. A number of image processing techniques are applied to the raw radar range profile maps to enhance the image quality and to remove the undesired effects. A linear feature extraction method based on Hough transform is used to extract the rectilinear features (walls, doors, etc.) in the complete map. Algorithms are developed to eliminate the ghost targets resulted from multi-path in the hallways.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"8 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":"122214343","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":"Terahertz computed tomography using a large-format, real-time focal plane array sensor","authors":"G. Trichopoulos, K. Sertel","doi":"10.1109/USNC-URSI-NRSM.2013.6525073","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6525073","url":null,"abstract":"Sub-millimeter scale image resolution afforded by the THz frequency band, coupled with the ability of THz waves to penetrate through packaging materials have sparked significant interest in THz frequencies for security screening. Conventionally, large-format THz images have been solely acquired using a raster scan of a single pixel, taking several minutes to create a single 2D image of a stationary scene. For stand-off screening applications, coherent THz radars with bulky reflector antennas and fast 2D scanning optics (via rotating mirrors) have cut the imaging time down to several frames per second (K. B. Cooper, IEEE Trans. on Terahertz Science and Technology, vol. 1, no 1, Sept. 2011). Nonetheless, the image resolution and the noise of the acquired images have yet to produce acceptable performance.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"49 4 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":"121196010","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":"Design of a multibeam spectrometer for the Green Bank Telescope","authors":"J. Ford, M. Bloss, P. Brandt, Hong Chen, J. Chennamangalam, J. Cobb, R. Creager, P. Demorest, G. Jones, R. McCullough, J. Ray, D. Roshi, S. Scott, A. Siemion, M. Wagner, G. Watts, D. Werthimer, M. Whitehead","doi":"10.1109/USNC-URSI-NRSM.2013.6525022","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6525022","url":null,"abstract":"A new multi-beam spectrometer for the Green Bank Telescope (GBT) is being designed and built by a partnership between the National Radio Astronomy Observatory (NRAO) and the University of California at Berkeley, and partially funded by a National Science Foundation Advanced Technology Instrumentation grant. The spectrometer is a heterogeneous computing device based on a Field Programmable Gate Array (FPGA) front-end and a heterogeneous compute server backend, comprised of Graphical Processing Units (GPUs) and x86 CPUs. Working together, the hardware in this system provides processing power to analyse up to 8 dual-polarization or 16 single-polarization inputs, at bandwidths of up to 1.25 GHz per input. An aggregate of up to 10 GHz of bandwidth, dual polarization, may be processed with the spectrometer.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"23 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":"121384434","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":"Structure of polar cap patches and fast shear flows following the CME impact on 22 January 2012 inferred from GPS scintillation spectra","authors":"C. Carrano, S. Basu, E. MacKenzie, K. Groves, T. Pedersen, J. Holmes","doi":"10.1109/USNC-URSI-NRSM.2013.6524986","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6524986","url":null,"abstract":"Polar cap patches are localized enhancements in ionospheric density which originate from solar EUV ionization on the dayside, enter the polar cap at the dayside cusp, convect anti-sunward at km/s velocities, and exit the polar cap near midnight to merge with sunward returning flow patterns. Plasma irregularities associated with polar patches are the leading cause of scintillations in L-band satellite signals such as GPS, and fast shear flows near the dayside cusp are thought to be integral to patch formation. In this paper, we report on the on the characteristics of polar cap patches and fast flows derived via analysis of the spectra of GPS scintillations recorded at Longyearbyen, Svalbard, following the CME impact on 22 January 2012. Following the interaction of the CME with the high latitude ionosphere, elevated GPS TEC values indicate the passage of patches through the cusp between 11-15 MLT, accompanied by significant GPS phase scintillations (σφ ~ 0.5 radians) but minimal amplitude scintillations (S4 <; 0.05). Examination of the scintillation spectra reveal that amplitude fluctuations were present, but not easily detected in the S4 observations because the fluctuation power was concentrated at high frequencies. In fact, these amplitude spectra can be explained in terms of Fresnel filtering of the path integrated irregularity spectrum with a relatively high cutoff frequency (8 Hz). This filtering is consistent with weak scatter of the satellite signals by irregularities scanning past the ray path with an effective velocity ~ 3 km/s. Since the velocity of the satellite penetration point is negligible, by comparison, this scan velocity is attributed to fast plasma flow, presumably associated with shear flows near the cusp. To exploit the Fresnel filtering effect, we developed a technique to derive the flow velocity by reconciling the phase and amplitude spectra with weak scatter theory. We applied this approach to investigate the noontime entrance of patches into the dayside cusp and the midnight exit of patches from the polar cap. We find clear evidence of strong phase scintillations with reduced S4 values in the presence of fast flows near the cusp, when the increasing Fresnel break frequency effectively suppresses the low frequency content in the amplitude fluctuations. The scan velocity increased from about 500-1000 m/s following the initial CME impact at ~6:00 UT, to sustained velocities between 1500-3000 m/s measured by GPS satellites whose ray paths intersected fast plasma flows near the cusp. In this sector, the phase spectral index (p) generally ranged between 2.4-2.8, with a tendency for somewhat larger values when the flow is faster. Weaker irregularities were detected in the outflow sector between 20-24 MLT, when p generally ranged from 2.6-3.0. The scan velocities measured in the outflow sector were slower, generally between 400-600 m/s. These velocity estimates compare favorably with ion drift measurements made by the DMSP satelli","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"86 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":"122684843","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":"The promise of cognitive radio for communications and remote sensing for critical infrastructure, disaster, safety, and risk management","authors":"C. Bostian","doi":"10.1109/USNC-URSI-NRSM.2013.6525045","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6525045","url":null,"abstract":"Public safety and disaster communications are hampered by problems of interoperability and dependence on critical infrastructure, particularly base stations and repeaters requiring fiber or wire backhaul and reliable primary power. Under normal conditions these are masked by workarounds (mutual aid agreements between nearby agencies, multiple radios in police cars, batteries and gasoline powered generators at base stations, etc.), but they become very obvious when disaster strikes, as in the case of New Orleans during Hurricane Katrina. Cognitive radios (transceivers that are aware of their RF and physical environments, able to take intelligent action based on that awareness to perform their mission and capable of learning from experience) offer attractive solutions to the interoperability and infrastructure problems. Integrating cognitive radios with small autonomous aerial vehicles (which like the radios survey their environments and take intelligent action) enhances the value of both, allowing the vehicles to consider communications requirements like propagation conditions and interference when they position themselves while providing real-time three-dimensional data from their sensors to track smoke, toxic plumes, structural damage, etc. This presentation reviews practical cognitive radio technology, particularly as applied to public safety and disaster management, and describes both some recent prototypes and ongoing research toward networks of autonomous vehicles that combine environmental sensing, intelligent response, and learning in a single “brain” that controls many aspects of motion control and radio operation.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"72 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":"122495573","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":"Experimental observation and computational modeling of hypervelocity impacts with emphasis on plasma formation and its consequences","authors":"D. Crawford","doi":"10.1109/USNC-URSI-NRSM.2013.6525001","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6525001","url":null,"abstract":"In experiments performed at the NASA Ames Vertical Gun Range (AVGR), optical and radiofrequency electromagnetic emissions, plasma formation and electrostatic charge separation during hypervelocity impact have been characterized for a variety of impactor and target geometries. While being investigated as potentially diagnostic of an event, such effects could also interfere with communications or remote sensing equipment if an impact occurred on a satellite. The highly conducting plasma could act as a current path across normally shielded circuits, potentially leading to satellite loss. In the AVRG experiments, early time solid debris ejected from the impact site are negatively charged and impact-generated plasma, late-time ejecta and materials left in the transient cavity are positively charged. Charge separation can lead to large electrostatic fields with implications for dust motion, especially in low gravity environments. The motion of charged ejecta can create transient magnetic fields. The experiments demonstrate that total charge separation is a function of impactor kinetic energy with a near linear mass dependence and velocity dependence proportional to v2.6. CTH is a Sandia developed, well validated, Eulerian, multi-material, computational hydrocode designed to treat a wide range of shock propagation and material motion phenomena in one, two, or three dimensions. Adaptive mesh refinement is available for maximizing resolution in regions of interest. CTH has models suitable for most conditions encountered in hypervelocity impact including material strength, fracture and multi-state materials, including plasma. It has been used extensively in hypervelocity impact studies at laboratory and large scale. Computational studies using CTH have shown that a simple two dimensional model based on electrostatic probe theory can match experimentally observed plasma and electrostatic charge separation. We are extending the CTH model to three dimensions to improve our ability to predict plasma formation and charge separation under more general circumstances.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"249 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":"132084709","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":"Natural cyclotron harmonic radiation from the ionosphere","authors":"J. Labelle","doi":"10.1109/USNC-URSI-NRSM.2013.6525086","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2013.6525086","url":null,"abstract":"Summary form only given. Earth's auroral ionosphere emits several types of spontaneous emissions, including auroral hiss, medium frequency burst, and roar. Auroral roar occurs at harmonics of the electron cyclotron frequency. The most commonly observed harmonic is 2fce, first reported in the 1970's. Since the 1990's, the 3fce harmonic has also been regularly observed from ground level. These emissions both favor pre-midnight magnetic local times and require darkness for observation at ground-level. Significant evidence has accumulated that they result from mode conversion of upper hybrid waves excited where the upper hybrid frequency matches the cyclotron harmonic. Satellite and rocket observations of the 2fce emission support that mechanism. Recently, two papers report observations of 4fce and 5fce emissions in Svalbard and in Antarctica. These higher harmonic emissions also favor pre-midnight magnetic local times but require sunlit ionosphere for observation. For all harmonics observed so far, the frequency scales linearly with the strength of the geomagnetic field at the observing station. Combining data from multiple stations allows estimation of source altitudes. Observations of the harmonics at a given station also provides a method for remotely sensing the ionospheric density.","PeriodicalId":123571,"journal":{"name":"2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"20 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":"130620800","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}