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Polarization independent quad-bandpass frequency selective surfaces with wide-band ratio
摘要： A single layer polarization independent quad-bandpass frequency selective surface (FSS) with wide-band ratio is demonstrated theoretically as well as experimentally. The proposed structure passes four frequency bands with wide band ratio. The proposed FSS design is implemented by incorporating alternate arrangement of four units which are rotated 90° clockwise to form a unit cell of metal over a FR4 substrate. The geometrical dimensions of proposed unit cell are optimized and arranged in such a way that the structure possesses the quad bandpass characteristic and aspect dimensions of one unit is 0.11λ × 0.11λ with respect to first resonant frequency. This FSS provides stable response for different angle of incidence in transverse electric (TE) mode and transverse magnetic (TM) mode. To validate the results proposed FSS array has been fabricated and measured in free space environment. The measured results are in good agreement with the simulated results. Excellent stability is also observed for different incident angle.
关键词： quad bandpass,polarization independent,frequency selective surface,band ratio
更新于2025-09-23 15:23:52
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A broadband circularly polarized monopole antenna
摘要： A compact modified C-shaped monopole antenna with broadband circular polarization is proposed, fabricated and measured. The antenna structure is simple and only consists of combined modified C-shaped radiation patch and an improved ground plane with the overall size of 25 × 25 × 1 mm3. By cutting the corner on the modified C-shaped patch and adding triangular stubs on the ground plane, the wide impedance bandwidth and axial ratio bandwidth are achieved. The design process of the antenna is given, and the circular polarization mechanism of the circularly polarized antenna is analyzed from the surface current distributions. The measured impedance bandwidth is 95.2% (4.4-12.4 GHz) with return loss better than 10 dB, and the measured 3 dB axial ratio bandwidth is 96.8% (4.42-12.72 GHz). The peak gain is above 3.0 dBi within the working band, which indicates that it is suitable for application of ultra-wideband (UWB) wireless communication systems and satellite communication systems.
关键词： axial ratio,ultra-wideband (UWB),monopole antenna,circular polarization
更新于2025-09-23 15:23:52
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Imaging multiple Rydberg wave packets from shaper-generated two-color femtosecond pump-probe sequences
摘要： We combine a bichromatic white light polarization pulse shaping scheme with angle- and energy-resolved photoelectron spectroscopy to image the dynamics of atomic Rydberg wave packets. Background-free detection of the Rydberg dynamics is performed using shaper-generated bichromatic linearly and circularly polarized femtosecond pump-probe pulse sequences. Photoelectron momentum distributions from linearly polarized bichromatic fields feature pronounced time-, energy-, and angle-dependent dynamics, which result from the interference of s-, d-, and g-type photoelectron wave packets from the ionization of the Rydberg np and nf series. Detailed analysis of the highly differential data allows us to extract the dynamics of both Rydberg wave packets separately. The results are experimentally verified by additional pump-probe studies with bichromatic circularly polarized pulse sequences, which exclusively map the dynamics of the Rydberg nf series via g-type photoelectron wave packets.
关键词： Rydberg wave packets,pump-probe spectroscopy,photoelectron imaging,femtosecond lasers,polarization pulse shaping
更新于2025-09-23 15:23:52
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Polarization and acoustic properties of barium-modified lead-free potassium–sodium niobate ceramics
摘要： Results of polarization and polarization switching in samples prepared by solid phase synthesis of the (1-х)(K0.5Na0.5)(Nb0.93Sb0.07)O3–xBaTiO3 + 0.5mol%MnO2 system at x = 0.01, 0.02, and 0.04 (KNNS7–xBT) studied over a wide range of temperatures are reported. The observed features of the dielectric nonlinearity at the ferroelectric and structural phase transitions in the materials are described. The dielectric response data of the samples of different contents of the admixture in the KNNS7–xВT ceramics are compared with the behaviour of their elastic properties.
关键词： dielectric permittivity,polarization,solid solutions,elastic properties,relaxors,ferroelectrics,ceramics
更新于2025-09-23 15:23:52
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[IEEE 2018 International Symposium on Networks, Computers and Communications (ISNCC) - Rome (2018.6.19-2018.6.21)] 2018 International Symposium on Networks, Computers and Communications (ISNCC) - Design of a Photoconductive Antenna for Pulsed-Terahertz Spectroscopy with Polarization Diversity
摘要： In the present paper, a photoconductive antenna is designed to work as both pulse-terahertz emitter and receiver. The proposed two-port antenna benefits from polarization diversity with high sensitivity of polarization detection. The antenna electrodes consist of three arms and two gaps that can be excited by laser illumination. An 800 nm wavelength laser beam with output power of 80 mW, 100 MHz repetition rate, and 100 fs laser pulse duration is considered as optical excitation. Each port stimulates a pulse that its polarization is orthogonal to that of the other one according to their arrangement. Along with GaAs as photoconductive substrate beneath the antenna electrodes, an anti-reflection coating of Taconic RF-35 is used for depreciating unwanted terahertz echoes. The simulated results clarify that the proposed antenna shows polarization diversity and also, proper broadband behavior.
关键词： spectroscopy,polarization diversity,pulsed terahertz,photoconductive antenna
更新于2025-09-23 15:23:52
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Liquid switchable radial polarization converters made of sculptured thin films
摘要： A radial polarization converter is a super-structured optical retarder that converts a conventional linearly polarized light beam into a structured beam with radial or azimuthal polarization. We present a new type of these sophisticated optical elements, which is made of porous nanostructured sculptured single thin films or multilayers prepared by physical vapor deposition at an oblique angle. They are bestowed with an axisymmetric retardation activity (with the fast axis in a radial configuration). In particular, a Bragg microcavity multilayer that exhibits a tunable transmission peak in the visible range with a retardance of up to 0.35 rad has been fabricated using this methodology. Owing to the highly porous structure of this type of thin films and multilayers, their retardance could be switched off by liquid infiltration. These results prove the possibility of developing wavelength dependent (through multilayer optical design) and switchable (through vapor condensation or liquid infiltration within the pore structure) radial polarization converters by means of oblique angle physical vapor deposition.
关键词： radial polarization converters,q-plates,oblique angle deposition,sculptured thin films
更新于2025-09-23 15:23:52
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A smartphone-based system for fluorescence polarization assays
摘要： This paper demonstrates the use of a smartphone-based sensor for fluorescence polarization (FP) analysis of biomolecules. The FP detection can rapidly sense ligand-analyte bindings by measuring molecule mobility, and thus, FP-based assays have been widely used for rapid diagnostics in clinics. Here, we implemented the FP detection apparatus using a 3D-printed compact holder and the built-in camera of a smartphone. The system offers accurate measurements of the degree of polarization by simultaneously detecting the fluorescence intensities parallel and perpendicular to the polarization of the excitation. The fluorescence signal of the sample is excited by a laser or light-emitting diode and separated by a polarization beam cube depending on the polarization. Parallel and perpendicular polarized emissions are projected onto two different regions of the sensor chip in the smartphone camera. A custom software app was developed to count the average intensity in the areas of interest and compute the degree of polarization. We validated the system by measuring the polarization of dye molecules dissolved in solutions with different viscosities. As an example of biomolecule sensing, a competitive FP immunoassay of Prostaglandin E2 was demonstrated using the developed system and exhibited the limit of detection of 1.57 ng/mL. The smartphone-based FP assay platform can also be implemented for the detection of toxins, disease biomarkers, and pathogens in resource-limited settings.
关键词： immunoassay,mobile sensor,fluorescence polarization assay,smartphone
更新于2025-09-23 15:23:52
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Electronic Structure of Chlorophyll a Solution Investigated by Photoelectron Yield Spectroscopy
摘要： Various bio-related processes are driven by electron transfer reactions. Therefore the electronic structures of bio-molecules in their living environment are keys of their functionalities. One significant example photosynthesis which has attracted much attention due to urgent necessity of clean energy source. In this study, we carried out photoelectron yield spectroscopy (PYS) measurements to demonstrate the electronic structures of oligomerizedChl-a molecules, which is known as an essential reaction center of the photosystem in general green plants, under the atmospheric environment. The ionization energies of the Chl-a aggregates are successfully derived.
关键词： Photoelectron Yield Spectroscopy,Polarization energy,Light harvesting antenna,Photosynthesis,Photosystem,Electronic structure,Ionization energy,Reaction center,Chlorophyll a
更新于2025-09-23 15:23:52
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Broadband simultaneously RHCP-LHCP radiating microstrip fed rectangular slot antenna for polarization diversity applications
摘要： In this article, for the first time, an antenna that can radiate LHCP and RHCP waves simultaneously is presented. The antenna enables simultaneous transmission of both right-handed (RH) and left-handed (LH) circular polarized (CP) waves separately over an elevation range from -45 to 45 degrees from the zenith. The simultaneous radiation of dual sense CP in the different spatial directions enables the antenna to act as polarization diversity transmitter. The mechanism of virtual sequential rotation of magnetic currents inside the different parts of the slot, excited with uniform phase fields results in dual CP generation. The uniform phase orthogonal fields are generated in the different parts of the slot essentially by exciting the full wavelength rectangular slot loaded with grounded stubs, symmetrically, with a shorted microstrip line. The final design of the slot antenna arrived with a rigorous parametric study on different dimensional parameters of slot and grounded stub. The measured impedance bandwidth of 22.5% centered around 7 GHz and axial ratio bandwidth of 19% is achieved. An overlapping bandwidth of 17% is achieved where both matching and AR are very good. The measured isolation between the RHCP and LHCP in the above-mentioned elevation ranges is maintained above 10 dB. The simulated and experimental results are matching very well.
关键词： right-handed CP,magnetic currents,Mobile satellite communications,axial ratio,rectangular slot,polarization diversity,left-handed CP,simultaneous dual CP
更新于2025-09-23 15:23:52
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Measurement and Investigation of the Incident Radiation in Case of Using Transparent Pyramidal Covers for Improving the Solar Panel’s Power Output
摘要： A new approach is presented to enhance the solar radiation intensity incident over the solar panel by using a transparent cover of pyramidal shapes. The pyramidal cover shape is manufactured of Polymethylmethacrylate dielectric material. The normal height of each pyramid is considered as a ratio of the base length. This ratio is considered in the present study to be 0.5, 1, and 1.5. The effect of the pyramidal covers on the solar panel voltage has been studied at different conditions. The experimental results confirm that the pyramidal cover shape causes the improvement to the solar panel output voltage by 4.2% when covering all the panel with pyramids of R=1 with a light incidence angle of 90 when the light rays come parallel to the panel surface. This improvement is found to decreases with covering fewer areas of the solar panel and with fewer incidence angles. It is found also that the distance between the light source and the panel is proportional to the output voltage improvement ratio compared to the panels output voltage without pyramidal cover. A mathematical model has been presented to prove the concept of increasing the electric and magnetic field of the incident radiation from the sun in case of presence of the transverse transparent barrier. Moreover, a mathematical ray tracking model was presented and validated with the experimental results by a maximum relative error of 14.8%
关键词： solar panel improvement,Incident radiation,enhancement of light field radiation,polarization,enhancement of solar radiation,transverse of transparent barrier
更新于2025-09-23 15:23:52