2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)最新文献

{"title":"Microwave imaging of objects hidden by non-penetrating obstacles using time reversal imaging technique","authors":"Ce Zhang, A. Ishimaru, Y. Kuga","doi":"10.1109/USNC-URSI-NRSM.2014.6928001","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928001","url":null,"abstract":"Summary form only given, In recent years, researchers have done extensive studies on “Through Wall Imaging(TWI)”, which reconstructs the image based on the backscattered waves passing through the dielectric wall. However, in some cases,the objects are completely obscured by non-penetrating obstacles such as “hard wall ”and the signals cannot pass through the wall as it is in TWI case.Therefore, conventional techniques are not applicable to “Hard Wall Imaging(HWI)”. In this paper, a new imaging technique is proposed based on time-reversal(TR) imaging technique and diffraction theory to resolve this problem. In our research, the target is assumed to be point scatter obscured by a conducting wall with two diffraction edges, which blocks all the transmission between antennas and targets. Since the target is located in the diffracted-field only region, only diffracted waves from conducting edge are received by the antennas. The conventional steering vector for free space imaging is not working well in this scenario so the diffraction coefficient has to be introduced to formulate a steering vector in HWI. The geometric diffraction theory(GTD) and uniform diffraction theory(UTD)are compared in the formulation of steering vector and the effect of polarization on diffraction boundary is also studied. After having obtained steering vector, TR imaging function applied to reconstruct the image from the received signals and steering vector.However, it was found that the coherence of array elements is not significant due to diffraction at the same edge points and the angle dependent diffraction coefficient results in a biased image around the edge point.Moreover, the product between received signal and steering vector results in undesirable terms and consequent ghost image. For these reasons, the backward signals due to two edges have to be measured separately and the images due to two edges are superimposed after normalization. As the image resolution is only attributed to the frequency correlation of pulse, the superimposed image will be two semi-rings with the center of diffraction edge point and the intersection region is exactly the location of target. In this way, both single antenna and array antenna can give the image with similar resolution using TR imaging function. Nevertheless, the TR-DORT(Decomposition of Time-Reversal Operator) imaging, which includes the measurement of multistatic matrix and subspace signal processing, requires the array antenna to apply eigen-decomposition and extract the dominant response from the target. It is expected that DORT method is more immune to the clutters and gives a cleaner image than conventional TR imaging.Futhermore, in this paper, apart from the formulations, FDTD simulation is employed to verify the validity of the new imaging techniques.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126394970","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":"Remote sensing of sea ice cover using SuperDARN HF radars","authors":"E. Thomas, K. Sterne, P. Ponomarenko, J. Baker, J. Michael Ruohoniemi","doi":"10.1109/USNC-URSI-NRSM.2014.6928034","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928034","url":null,"abstract":"Summary form only given. In addition to returns from field-aligned plasma irregularities in the ionosphere, SuperDARN radars also observe backscatter from Earth's surface on a daily basis. These ground scatter echoes have been used to characterize the ionosphere in variety of ways, such as monitoring atmospheric gravity waves, E and F layer critical frequencies, and ultra-low frequency (ULF) wave propagation. We have calculated monthly ground scatter occurrence rates for four high-latitude SuperDARN radars and compared them to Arctic sea ice boundaries derived from satellite observations courtesy of the National Snow and Ice Data Center (NSIDC). Regions covered by sea ice are shown to be weak scatterers for the HF signals, while sea surfaces not covered by ice produce more easily detectable backscatter than land regions in Canada and Greenland at comparable ranges. The spatial resolution and coverage of these results are influenced by several factors: seasonal ionospheric propagation conditions, relatively large range cell resolution (45 km), and the need for a thick daytime ionosphere to reflect radar signals down to the Earth's surface. In this talk, besides statistical analysis of historical high-latitude SuperDARN observations, we will present first results from a new radar control program designed to improve detection of sea ice boundaries.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"20 8","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113931795","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":"Improvements in an anisotropic ocean surface emissivity model based on WindSat polarimetric brightness observations","authors":"Dean F. Smith, A. Gasiewski","doi":"10.1109/USNC-URSI-NRSM.2014.6928052","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928052","url":null,"abstract":"The goal of this research has been to develop a standardized fast full-Stokes ocean surface emissivity model with Jacobian for a wind-driven ocean surface applicable at arbitrary microwave frequencies, polarizations, and incidence angles. The model is based on the Ohio State University (OSU) two-scale code for surface emission developed by Johnson (2006, IEEE TGRS, 44, 560) as presented in our 2013 URSI talk. A total of five physical tuning parameters were identified, including the spectral strength and the hydrodynamic modulation factor. The short wave part of the spectrum is also allowed to have an arbitrary ratio relative to the long wave part. The foam fraction is multiplied by a variable correction factor, and also modulated to allow an anisotropic foam fraction with more foam on the leeward side of a wave.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"78 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131916635","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":"Optimizing an observable for ocean wind speed retrieval from calibrated GNSS-R delay-Doppler maps","authors":"N. Rodriguez-Alvarez, J. Garrison, C. Ruf, M. Clarizia","doi":"10.1109/USNC-URSI-NRSM.2014.6928068","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928068","url":null,"abstract":"The fundamental measurement produced by Global Navigation Satellite System Reflectometry (GNSS-R) is the cross-correlation between the scattered signal and a local copy of the GNSS code and carrier, producing a bivariate function defined as the delay-Doppler map (DDM). The shape of the DDM is sensitive to the roughness of the scattering surface and, through various empirical models, the ocean surface winds. Ocean winds can be retrieved by fitting a scattering model to DDM observations, or identifying an observable, such as trailing edge slope or DDM area exceeding a threshold. A variety of such methods have been demonstrated with airborne experiments. With the selection of the CYGNSS mission by NASA, there is now a need to extend these methods to spaceborne measurements.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132537204","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 survey of cognitive beamforming techniques","authors":"B. Murray, A. Zaghloul","doi":"10.1109/USNC-URSI-NRSM.2014.6927993","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6927993","url":null,"abstract":"Digital beamforming is a spatial-filtering technique in multi-antenna communication systems. A signal processor controls the excitation of antenna array elements to synthesize a desired radiation pattern with the general objective to increase gain in the direction of intended receivers or wanted signal sources and reduce gain in the direction of known or potential sources of interference. In the context of a cognitive radio network, where interference mitigation is a paramount concern, beamforming and precoding techniques offer significant advantages in terms of spectral efficiency, power control, link capacity, transmission security, and improved signal to interference plus noise ratio (SINR). Cognitive beamforming approaches the selection of array coefficients as a convex optimization problem in a machine-learning algorithm. A cognitive engine stores previously derived solutions in a knowledge base and autonomously applies beamforming decisions toward the ultimate goal of predicting channel conditions and proactively adjusting antenna array patterns to maintain network connectivity and performance. This informed decision-making ability distinguishes cognitive beamformers as an evolution of traditional adaptive arrays and smart antenna systems. This paper presents a survey of various cognitive beamforming techniques in interweave, overlay, and underlay networks. Algorithms are categorized based on their applicability to multiple-input, single output (MISO) or multiple-input, multiple output (MIMO) systems and any constraints or idealization of channel state information and quality of service metrics. The techniques evaluated include distributed, joint, and cooperative beamforming strategies with optimization schemes based in game theory, communication informatics, neural networking, and genetic algorithms. Current limitations of the technology are provided and guidance for future research in the field is suggested.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"24 9","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133267550","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":"UHF deployable antenna structures for CubeSats","authors":"J. Costantine, Y. Tawk, F. Ayoub, C. Christodoulou, G. Olson, S. Pellegrino","doi":"10.1109/USNC-URSI-NRSM.2014.6928057","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928057","url":null,"abstract":"Summary form only given. Antenna design for small satellites such as CubeSats constitute a challenge for designers especially at UHF frequencies. The small size of the CubeSat (10 cm × 10 cm × 10 cm) imposes several constraints on the antenna design. Extreme packaging ratios and advanced deployment mechanisms have to be employed to cater for UHF antennas on a CubeSat platform. Many types of deployable antennas have been used on orbit. Reflector types constitute their widest category. Other deployable structures made with folded hoops or ribs are also used for space communications. Other researchers have resorted to tape springs and neutrally stable material to design their structures. An example of potential CubeSat deployable antenna candidates is a log periodic crossed dipole antenna array. The log periodic crossed dipole antenna array, constructed with a bi-stable composite material, exhibits a directive beam with a wide bandwidth. The characteristics of the bi-stable composite material allow a more efficient antenna deployment mechanism. A log periodic crossed dipole antenna array can extend up to 55 cm for UHF frequency operation with the longest element being around 60 cm. Another potential antenna candidate is the conical log spiral antenna. The conical log spiral antenna typically fed at its apex exhibits a circular polarization with a wide bandwidth. This antenna radiates outwards from the direction of the antenna's apex and thus, it has to deploy in a manner to radiate away from the satellite. A typical conical log spiral antenna's height can extend up to 62 cm with a bottom circular base of radius 23 cm and a top radius of 5 cm. Other configurations of the conical log spiral antenna can also be proposed to satisfy various constraints such as a narrower base or a bigger height. A bottom fed conical log spiral antenna deployed on top of a ground plane is another possible candidate. One of the main benefits of this topology is an easier feeding mechanism after deployment. In this case the antenna still radiates upward and away from the satellite due to the presence of a significant ground plane under its base. Another candidate for deployment on CubeSat is a Quadrifilar Helix antenna. This antenna built with beryllium copper deploys on top of a ground plane that has a square shape with a side of 1.25λ. The antenna is fed by multiple power dividers and phase shifters to allow a progressive 90° phase shift between the four elements constituting the antenna. This antenna achieves a gain around 8 dB at UHF frequencies with a circular polarization performance. The antenna however exhibits a narrower bandwidth than the previously discussed conical log spiral antenna. Finally there are many possible candidates for antenna deployment on CubeSats as long as these candidates satisfy desired constraints. On the other hand, a deployable UHF antenna for CubeSats imposes an additional storage constraint due to size limitation.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132087851","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":"Height dependence of equatorial zonal plasma drifts","authors":"D. Hui, B. Fejer","doi":"10.1109/USNC-URSI-NRSM.2014.6928077","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928077","url":null,"abstract":"Summary form only give. Equatorial ionospheric plasma drifts play important roles on the dynamics of the low latitude ionosphere. We use extensive F region measurements by the Jicamarca incoherent scatter radar and E region observations by the JULIA system to determine the season and solar cycle dependent altitudinal dependence of the equatorial zonal quiet-time plasma drifts. We also examine the altitudinal dependence of the zonal quiet-time drifts in the topside ionosphere over Peruvian equatorial region using Vector Electric Field Instrument (VEFI) onboard the C/NOFS satellite during the 2008-2011 very low solar flux period. The quiet-time F region zonal drifts are westward from about 06 to 16 LT with solar flux independent quiet-time peak values of about 40-60 m/s; they reverse to eastward at about 16-17 LT. Near noon, the zonal drifts do not change much with altitude during June solstice, but increase with height during equinox and December solstice. The nighttime F region drifts are generally eastward with peak values in the early nighttime sector that increase from about 100 to 200 m/s from solar minimum to solar maximum. The F region drifts exhibit large altitudinal variations near dusk where they are westward at the lowest altitudes and eastward near the F layer peak and above. We show that this altitudinal shear varies with season and solar cycle and is closely related to the height variation of the vertical plasma drifts and peak plasma density. We present C/NOFS measurements showing that near solar minimum the post-midnight eastward drifts decrease with altitude above the F layer peak. We also compare our climatological E and F region drifts with results from recent numerical modeling studies and briefly discuss the large short-term variability of these drifts.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114641848","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":"Conformal antenna applicator for Traumatic Brain Injury assessment","authors":"Megan Gillespie, M. Asili, E. Colebeck, E. Topsakal","doi":"10.1109/USNC-URSI-NRSM.2014.6928141","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928141","url":null,"abstract":"Summary form only given. Traumatic Brain Injury (TBI) is a major cause is defined as the trauma caused by the injury to the head and according to Center for Disease Control (CDC), TBI is the major cause of death worldwide. Most TBI injuries are related to traumas sustained at the battle field therefore males experience more TBIs than females. Other major causes of TBI include falls and vehicle accidents. Depending on the severity of the TBI, the effects can be behavioral, physical, social, cognitive, and emotional. The injury can be fatal or can leave the person disable for life. The most effective way of diagnosing TBI is through Magnetic Resonant Imaging since MRI provides excellent soft tissue contrast. Different treatment options are followed based on the severity of the TBI ranging from medication to emergency surgery. Because TBI can be fatal, the early diagnosis and treatment is the key to save lives. According to CDC, a significant percentage of the people are not killed instantly but after a period of time if they do not receive proper assessment and treatment. Although MRI is the most effective technology for assessment, unfortunately, it is very expensive and the bulkiness of the equipment prevents it to be used in many different setting such as battlefield. In order to provide a quick and cost effective assessment technology, in this study, we investigate conformal microwave arrays. We consider different frequencies to study the sensitivity and efficacy of the antenna array. We also provide ex vivo measurement using pig brain and skull phantoms.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116792485","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":"Fine-scale observations of artificial aurora at 777.4 nm","authors":"R. Michell, P. Bernhardt, M. Samara","doi":"10.1109/USNC-URSI-NRSM.2014.6928081","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928081","url":null,"abstract":"We present observations of artificially generated auroral emissions using the High power Active Auroral Research Program (HAARP) ionospheric heating facility located in Gakona, Alaska. We operated an EMCCD imager at the HAARP facility which enabled high temporal and spatial resolution observations of the heater induced airglow emissions. The imager was equipped with a 777.4 nm narrowband filter to investigate this specific prompt emission. These observations were taken at 3 Hz frame rate using a 19 degree field of view lens, that produces spatial resolution of 100s of meters. The small-scale optical features observed will be quantified for different cycles of ionospheric heating, including on-off cycles of minutes to continuous heating for an hour. In addition to the imager at HAARP, we operated several other imagers at Poker Flat, Alaska in order to observe the artificial emissions from the side. This enabled an accurate measure of the altitude of the emissions and allowed us to follow the changes in altitude as the emissions developed in time. The imagers at Poker Flat included a 6300 nm imager with a 47 degree field of view and a 5577 nm imager with 15 degree field of view. This allowed us to image the lower energy and slower emissions, where the decay time of the emissions was observable when the heater was cycled off. The spatial scale, motion, lifetime and altitude of the emission features will be quantified for the different cycles, in order to gain insight into the strong plasma wave activity-generated by the heater-that is causing the local electron acceleration and heating.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117183797","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":"Initial results from a forward-scatter meteor wind radar experiment based on the Colorado Software Radar (CoSRad)","authors":"C. Vaudrin, S. Palo","doi":"10.1109/USNC-URSI-NRSM.2014.6928100","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928100","url":null,"abstract":"Summary form only given. This talk concerns three primary related topics on the subject of forward-scatter meteor wind radar. First, forward-scatter from meteor trails is discussed in the context of the Colorado Software Radar (CoSRad) architecture; a multistatic, phase synchronous software defined radar receiver. Two primary improvements are outlined with respect to the traditional monostatic meteor wind radar. Increased detection rates leading to improvements in spatial and temporal resolution of the wind measurement in addition to expanding the geographic extent of the meteor wind radar measurement capabilities into the mesoscale (thousands of km2) regime. Secondly, the Ground Illumination Pattern (GIP) produced by VHF meteor trail scatter under a wide range of trail geometries is presented and used to justify an optimal multistatic receiver station geometry. Finally, results from a forward scatter experiment using the Bear Lake meteor radar at Utah State University as the transmitter and a receiving station in Platteville, CO are presented and compared with a forward-scatter detection statistics model based on the GIP calculation technique. This experiment stands as a proof-of-concept measurement using the CoSRad architecture, and serves as a basis for our future plans to demonstrate the phase synchronous multistatic meteor wind radar.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124677646","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}