- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Demonstration of Large Bandwidth Hard X-Ray Free-Electron Laser Pulses at SwissFEL
摘要： We have produced hard x-ray free-electron laser (FEL) radiation with unprecedented large bandwidth tunable up to 2%. The experiments have been carried out at SwissFEL, the x-ray FEL facility at the Paul Scherrer Institute in Switzerland. The bandwidth is enhanced by maximizing the energy chirp of the electron beam, which is accomplished by optimizing the compression setup. We demonstrate continuous tunability of the bandwidth with a simple method only requiring a quadrupole magnet. The generation of such broadband FEL pulses will improve the efficiency of many techniques such as x-ray crystallography and spectroscopy, opening the door to significant progress in photon science. It has already been demonstrated that the broadband pulses of SwissFEL are beneficial to enhance the performance of crystallography, and further SwissFEL users plan to exploit this large bandwidth radiation to improve the efficiency of their measurement techniques.
关键词： large bandwidth,SwissFEL,free-electron laser,spectroscopy,hard x-ray,x-ray crystallography
更新于2025-09-23 15:19:57
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[IEEE 2018 16th International Conference on Emerging eLearning Technologies and Applications (ICETA) - Stary Smokovec, Slovakia (2018.11.15-2018.11.16)] 2018 16th International Conference on Emerging eLearning Technologies and Applications (ICETA) - High-Capacity Wavelength Division Multiplexing Optical Transmission Systems
摘要： The new services and constantly growing number of users develop constant pressure for current transmission systems. Although the first optical systems started to be used at the beginning of 1980s, the last forty years have brought unprecedented development of these systems. Today's optical transmission systems play key role for satisfaction bandwidth demands. This paper provides short insight into the technological evolution of optical transmission systems and show why these systems are mostly used in long-haul and metro networks. The first transmission systems had transmission capacity around 45 Mb/s, today's capacity is beyond 2 Pb/s. We looked at the key technologies as well as their future trends.
关键词： optical transmission systems,wavelength division multiplexing,bandwidth demands,WDM,CWDM,DWDM,optical fiber
更新于2025-09-23 15:19:57
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A Low-profile Wide Band “S” Shaped Rectangular Dielectric Resonator Antenna for “X” Band Application
摘要： The main goal of this article is to design a low-profile wide band Rectangular Dielectric Resonator Antenna (RDRA). The proposed “S” shaped rectangular DRA is excited by means of a popular microstrip line feeding. By using “S” shaped design, our proposed DRA yields an impedance bandwidth of 32% from 9.2 to 12.48 GHz, covering “X” band frequency. The proposed antenna has a wide impedance bandwidth, extremely low profile with the volume of 447 mm3, and a thickness equal to 2.5 mm. This design provides stable radiation patterns and high radiation efficiency. The proposed design is compared with some other designs in the literature in order to emphasize its significance. The proposed RDRA was fabricated and its characteristics were tested. Excellent agreement between simulated and measured ones was obtained.
关键词： Radiation pattern,Rectangular dielectric resonator antenna (RDRA),Low profile,X band,Impedance bandwidth
更新于2025-09-23 15:19:57
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Spoof Surface Plasmon Polaritons Based Reconfigurable Band-Pass Filter
摘要： This letter reports the design and analysis of the bandwidth (B.W.) reconfigurable band-pass filter using spoof surface plasmon polaritons at THz/Microwave frequency. The designed filter consists of a spoof SPP T-shape resonator in which tuning has been introduced using variable capacitor device (having a cutoff frequency in THz regimes). Even and odd mode analysis has been carried out for a better understanding of the phenomenon. The proposed concept of variable bandwidth at a THz frequency in SSPP structure has been demonstrated through Co-EM simulation. For the experimental validation of the proposed approach, the filter has been designed at microwave frequency and developed on a 60 mil (1.52mm) thick microwave laminate and characterized using Keysight Field-Fox analyzer N9918A. In THz and microwave frequency regime, the designed filter has 3dB B.W. reconfigurability of 20GHz (0.41THz-0.43THz) and 300MHz (100MHz – 400MHz) with the insertion loss (I.L.) of ~3dB and ~1.7dB - 3.2dB respectively. The Proposed reconfigurable band-pass filter will pave an important role in the design and development of plasmonic circuits and systems.
关键词： bandwidth,reconfigurable,spoof surface plasmon polaritons,Band-pass filter
更新于2025-09-19 17:15:36
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Fast and accurate model for a coax-fed rectangular patch antenna with varying aspect ratio, feed location and substrate electrical parameters
摘要： An improved closed-form model based on cavity model and single resonant parallel R-L-C circuit analysis is proposed to predict the resonant frequency, quality factor, bandwidth, gain and input impedance of a coax-fed rectangular patch antenna as a function of aspect ratio, feed location and substrate electrical parameters. The computed values employing the present model are compared with our experimental results and experimental results available in open literature. We have also employed electromagnetic high-frequency structure simulator (HFSS) software to validate the model. The present model shows very close agreements with the experimental and simulation results compared to the other models. This model is very simple, fast and accurate. The present model can be directly applied to CAD program.
关键词： Improved closed-form model,microstrip antennas,gain,bandwidth,input impedance,resonant frequency,quality factors
更新于2025-09-19 17:15:36
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A novel analytical method for designing a multi-band, polarization-insensitive and wide angle graphene-based THz absorber
摘要： In this paper, we propose a simple and analytical method to design a multi-band tunable graphene-based absorber using circuit model. The presented paper provides a flowchart and equations to design a multi-band absorber which tremendously simplifies the design procedure of a multi-band absorber. This paper only investigates the disk shape graphene-based absorber, but we believe the proposed method is extendable to all presented shapes of graphene which previously designers provided with a circuit model. To verify the accuracy of the presented method; we have designed several multi-band absorbers and used Full-wave numerical modeling of the structure to approve our method. Also, this paper studies the reliability of our proposed model by investigating the fabrication sensitivity of the structure. Lastly, this paper investigates to see how a multi-band absorption spectra behave, in case there are any errors during the fabrication phase. The designed absorbers have potential applications in various fields of active THz metamaterials, tunable filters, and sensors. The graphene-based disk-shaped absorber has the advantage of polarization insensitivity, wide-angle absorption and ease of implementation due to its simple shape. Another advantage of using graphene in the absorber structure is that with the availability of changing the Fermi energy level, it is possible to tune the absorption frequency of the multi-band absorbers.
关键词： Circuit model,Absorber,Graphene Terahertz,Tunable bandwidth,Transmission line method
更新于2025-09-19 17:15:36
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A Heavy Load Optimized Dynamic Bandwidth Allocation Algorithm for Hybrid WDM/TDM VPONs
摘要： Hybrid wavelength division multiplexed (WDM)/Time division multiplexed (TDM) virtual passive optical networks (VPONs) are considered to provide cost efficient solutions for increasing bandwidth requirements of next generation optical access networks. With the development in technology effective bandwidth assignment has emerged as a major concern area. In this paper a novel heavy load optimized dynamic bandwidth allocation algorithm (HLO-DBA) is proposed for the hybrid WDM/TDM VPONs. Multi point control protocol of Ethernet passive optical network (EPON) is implemented for WDM/TDM VPONs subscribers. The excess bandwidth of lightly loaded subscribers is distributed among heavily loaded users through an efficient mechanism. The proposed technique effectively utilize the idle period between the last REPORT messages from previous transmission cycle (t-1) to the first GRANT message in the current cycle (t). Optical network units (ONUs) connecting the subscribers are scheduled in such a way so as to reduce the wastage of bandwidth. Performance evaluation of HLO-DBA in terms of quality of service (QOS) metrics like throughput and average delay is done to validate the optimization of the proposed mechanism.
关键词： heavily loaded onus,upstream channel,bandwidth allocation,throughput,VPONS
更新于2025-09-19 17:15:36
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Effects of high photon gas density and radiative efficiency on upper bounds of energy conversion efficiency in single-crystal solar cells
摘要： The impact of the signal bandwidth and observation bandwidth on the detection performance of the maximum-minimum eigenvalue detector is studied in this letter. The considered signals are the Gaussian signals. The optimum ratio between the signal and the observation bandwidth is analytically proven to be 0.5 when reasonable values of the system dimensionality are used. The analytical proof is verified by simulations.
关键词： Maximum-minimum eigenvalue detection,detection bandwidth,Marchenko Pastur density,occupation bandwidth
更新于2025-09-19 17:13:59
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[IEEE 2019 International Electronics Symposium (IES) - Surabaya, Indonesia (2019.9.27-2019.9.28)] 2019 International Electronics Symposium (IES) - Identification and Protection of Series DC Arc Fault for Photovoltaic Systems Based on Fast Fourier Transform
摘要： This letter develops a distributed algorithm for relay pairing in bandwidth exchange (BE) based cooperative forwarding scenarios, where each node can delegate a fraction of its allocated resources to a neighboring node as an incentive for relaying. Determining the relay pairs that maximize the overall network utility yields a non-bipartite matching problem, which incurs a considerable computational load when implemented in a centralized way. To resolve this challenge, we use a message-passing framework to develop an efficient distributed solution. Simulation results verify that the proposed algorithm outperforms existing approaches.
关键词： bandwidth exchange,message passing algorithm,Affinity propagation,cooperative forwarding
更新于2025-09-19 17:13:59
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Narrow bandwidth optimization using a polymer microring resonator in a thulium holmium fiber laser cavity
摘要： A thulium–holmium fiber (THDF) laser cavity has been demonstrated with a SU-8 polymer microring resonator (PMRR) in the cavity. The PMRR has a 500 μm radius and fabricated using the lithography method, with the SU-8 polymer acting as a host material. The butt coupling method was used for the horizontal coupling of light from a ultra-high numerical aperture (UHNA) fiber to the polymer waveguide. Lasing in the cavity without the PMRR is obtained at a center wavelength of 1.910 μm, 1.869 μm when the PMMR is inserted into the cavity. A maximum power of -5 dBm was extracted from the laser oscillator, and the laser linewidth was measured to be ～26.6 kHz by radio-frequency spectrum analyzer analysis. The PMRR was able to generate an output with a free spectral range of 0.79 μm at a frequency of 59.25 GHz.
关键词： Thulium–holmium fiber lasers,Narrow bandwidth,Polymer microring resonator
更新于2025-09-19 17:13:59