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- 2018
- GaN HEMTs
- Power amplifier
- Broadband power amplifier
- SC band
- Power combining
- concentrated capacitive load
- distribution of the complex current at the antenna
- broadband antenna
- standing wave voltage factor
- antenna gain factor
- Electronic Science and Technology
- Oles Honchar Dnipro National University
- University of Tehran
- Gdansk University of Technology
- V. N. Karazin Kharkiv National University
- Reykjavik University
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An ultra-broadband THz absorber based on structured doped silicon with antireflection techniques
摘要： Broadband absorber in the terahertz region (0.1-10 THz) has attracted considerable attentions due to its important applications in detecting, imaging and electromagnetic stealth. Recently, terahertz absorber with broadband features has been widely investigated, however the achievement of ultra-broad bandwidth is still challenging due to the limitations of complex structural design and fabrication processes. In this letter, an ultra-broadband terahertz absorber covering the entire terahertz regime (0.1-10 THz) based on the heavily doped silicon has been designed and fabricated, which is composed of double-layer binary gratings filled with the SU-8 photoresist. Antireflection techniques (SU-8 layer) were utilized to further promote the performance of the terahertz absorber at high frequencies through matching the impedance between free space and doped-silicon substrate. The measured absorption exceeding 87% within the frequency range of 0.3-10 THz has verified the proposed approach in designing the ultra-broadband terahertz absorber. Furthermore, the designed absorber remains high performance in the case of wide-angle incidence even up to 60°. Benefiting from the simple structure, the absorber is easy to be fabricated by common optical lithography. We believe the results of this work could broaden the application areas of terahertz absorbers.
关键词： ultra-broadband,antireflection techniques,terahertz absorber
更新于2025-09-10 09:29:36
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[IEEE 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - Chengdu, China (2018.3.26-2018.3.28)] 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - A Compact Broadband Filter Using Triple-Mode Stepped-Impedance Stub-Loaded Resonator
摘要： In this paper, a compact broadband bandpass filter (BPF) using triple-mode stepped-impedance stub-loaded resonator (TMSISLR) is proposed. The TMSISLR is composed of an impedance-transforming unit and two asymmetrical open-ended stepped-impedance stubs (SIS) at the center. By simply adjusting the impedances of the SIS, the resonant frequencies of the TMSISLR can be flexibly changed. The interdigital coupled-lines are adopted to feed the proposed TMSISLR. This BPF can realize wide bandwidth, low insertion loss, high selectivity, and deep stopband rejection simultaneously. Finally, the proposed BPF is simulated, fabricated, and measured. The measured results show that the impedance bandwidth under -16.7 dB is 86% from 1.89 to 4.75 GHz, while the insertion loss is smaller than 1.47 dB. The measured insertion loss is larger than 30 dB at both low- and upper-stopband (from 0 to 1.27 GHz and 6.03 to 7.66 GHz). The measured results are in good agreement with the simulated counterpart.
关键词： stepped-impedance stubs,broadband,triple-mode resonator,filter
更新于2025-09-10 09:29:36
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Generation of rogue waves in gyrotrons with high excess over the threshold
摘要： Many physical systems exhibit behavior associated with the emergence of the so-called rogue waves which represent dramatically high-amplitude events that occur with low probability but much more frequently than expected in ordinary wave statistics [1]. For example, in laser physics and optics rogue waves arise in the process of supercontinuum generation and represent pulses of ultra broadband light with extremely high peak power [2]. In this paper within the framework of the average approach and in direct 3D PIC (particle-in-cell) simulations we demonstrate that rogue waves can also appear in gyrotrons operating with high excess over the threshold. The mechanism of extreme spikes formation is related to simultaneous cyclotron interaction of a gyrating electron beam with forward and backward waves near the waveguide cutoff frequency as well as with the longitudinal deceleration of electrons. From the practical point of view, experimental observation of the rogue waves generation in gyrotrons can be interesting as a method for production of high-power millimeter-wave radiation with an ultra broadband spectrum. The required exceeding over the threshold can be achieved for routine parameters of the driving electron beams formed by the magnetron-injection guns due to operation at the lowest modes of microwave cavities.
关键词： high-power millimeter-wave radiation,rogue waves,gyrotrons,ultra broadband spectrum
更新于2025-09-10 09:29:36
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High efficient linear polariser using FSS structure
摘要： A linear polarisation converter surface with broadband and high-efficiency properties is proposed. The proposed frequency selective surface (FSS) polariser consists of two-corner-cut diagonal rectangular printed on a substrate backed by a pinwheel loop shape ground. The combination of two-corner-cut diagonal rectangular patch and pinwheel loop shape ground contributes to bandwidth expansion. Numerical results indicate that the FSS structure is capable of converting x or y polarised incident wave to the relevant cross-polarised wave in a wide frequency range from 7.5 to 24.5?GHz with a fractional bandwidth of 106% for ?10?dB rxy reflection amplitude. In addition, the ryy and rxy reflection coefficients of the proposed unit-cell present slight variation for different incident angles up to 40°, which verifies the applicability of the proposed FSS structure in a practical environment. For experimental validation, a prototype of the FSS structure is fabricated and reflection parameters of the proposed structure are measured which agree well with corresponding simulations. Due to the minimal dependency on the angle of incidence and non-uniform ground plane the proposed polarisation converter unit-cell can be a possible choice for secure building applications.
关键词： broadband,linear polarisation converter,frequency selective surface,FSS structure,high-efficiency
更新于2025-09-10 09:29:36
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Magneto-Electric Dipole Antenna (MEDA)-Fed Fabry-Perot Resonator Antenna (FPRA) With Broad Gain Bandwidth in Ku Band
摘要： One planar Fabry-Perot resonator antenna (FPRA) with broad gain bandwidth is proposed in this paper. Magneto-electric dipole antenna (MEDA) is used as the feeding antenna providing good impedance matching and stable radiation pattern over the whole Ku band. Then gain enhancement is realized by loading with one partially reflective surface (PRS), which consists of a single dielectric slab with two-dimensional patches array on both surfaces. Unlike the sharply negative phase slope of conventional cover designs, the proposed one produces a much gentle reflective phase gradient with both negative and positive phase slopes. Thus the gain property of the MEDA is obviously improved along the whole band. One prototype is fabricated for verification and the results show that the proposed antenna has a wide impedance bandwidth, which is 56.25% for S11<-10dB, ranging from 11.5 GHz to 18.7 GHz. It possesses a 3-dB gain bandwidth of 35% from 12.3 GHz to 17.2 GHz with a peak gain of 11.2 dBi at 14 GHz. Compared with the unloaded type, gain enhancement of about 1.5~5 dBi is achieved. Due to the advantages of simple structure and broad gain bandwidth, this method is a good option to design antennas in satellite communication systems in future.
关键词： Fabry-Perot resonator antenna (FPRA).,Broadband high gain,magneto-electric dipole antenna (MEDA)
更新于2025-09-10 09:29:36
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Broadband LWIR and MWIR absorber by trapezoid multilayered grating and SiO2 hybrid structures
摘要： A broadband metamaterial absorber with high absorption simultaneously in mid-wave infrared (MWIR) and long-wave infrared (LWIR) was proposed. In the MWIR, the absorption higher than 0.8 is from 4 to 6.3 μm, while the absorption in the LWIR is from 8.7 and 9.6 μm. The absorber is insensitive to the incident angle. The broadband absorption in the MWIR is due to the slow-light effect of the trapezoid multilayered grating structure. And the broadband absorption in the LWIR is due to the phonon polariton resonant of trapezoid SiO2 layer. In the broadband high absorption region, the atmosphere is transparent, which may greatly promote the practical application of the absorber in double-color IR imaging, detecting, infrared stealth and thermal emitting.
关键词： Metamaterial,Transparent atmosphere window,Broadband absorber,Slow-light effect,Phonon polariton resonant
更新于2025-09-10 09:29:36
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BROADBAND PERFECT METAMATERIAL ABSORBER ON THIN SUBSTRATE FOR X-BAND AND KU-BAND APPLICATIONS
摘要： A broadband Perfect Metamaterial Absorber (PMA) on FR-4 Epoxy substrate for X-band and Ku-Band applications is proposed. The unit cell structure is composed of rectangular patches of appropriate shapes and orientation on top of the metal-backed dielectric substrate having a thickness of 2.7 mm (0.16λL). The relative absorption bandwidth is 79% (more than 85% absorption) covering the entire X-band and the Ku-Band of the microwave frequencies. The surface current distributions of the top and bottom planes have been analyzed to elaborate the absorption mechanism of the structure. The broadband characteristics of the design support its claim of being useful to a wide range of applications in both commercial and research sectors. Such applications include military and stealth devices, thermal sensors and electronic-cloaking devices.
关键词： broadband,FR-4 Epoxy substrate,perfect metamaterial absorber,Ku-band,X-band
更新于2025-09-10 09:29:36
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Design of broadband polarization converter for terahertz waves
摘要： A broadband reflective polarization converter is proposed. The unit cell of polarization converter is composed of a single-split resonant ring, a double-split resonant ring, a dielectric substrate and a metallic ground. The simulated results show that the polarization converter can convert x-polarized waves into y-polarized waves and obtain a broadband polarization conversion from 0.501 0 THz to 1.390 0 THz with the polarization conversion ratio (PCR) beyond 80% at normal incidence. Moreover, the surface current distributions are investigated to explain the polarization conversion mechanism. Finally, a good agreement is achieved between simulated and measured results. The polarization converter can be applied in terahertz imaging, communication and stealthy technology.
关键词： metasurface,terahertz waves,polarization conversion ratio,broadband,polarization converter
更新于2025-09-10 09:29:36
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Broadband Defects Emission and Enhanced Ligand Raman Scattering in 0D Cs <sub/>3</sub> Bi <sub/>2</sub> I <sub/>9</sub> Colloidal Nanocrystals
摘要： Excitonic 0D and 2D lead-halide perovskites have been recently developed and investigated as new materials for light generation. Here broadband (>1 eV) emission from newly synthesized 0D lead-free colloidal Cs3Bi2I9 nanocrystals (NCs) is reported. The nature of their emissive states as well as the relative dynamics which are currently hotly debated are investigated. In particular, it is found that the broadband emission is made by the coexistence of emissive excitons and sub-bandgap emissive trap-states. Remarkably, evidence of enhanced Raman scattering from the ligands is observed when attached to the NCs surface, an effect that is preliminarily attributed to strong exciton-ligands electronic coupling in these systems.
关键词： trap-states emission,enhanced Raman scattering,broadband emission,lead-free perovskites,0D nanocrystals
更新于2025-09-10 09:29:36
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A tunable broadband filter of ternary photonic crystal containing plasma and superconducting material
摘要： This work reports the optical properties of a one-dimensional (1D) ternary periodic structure composed of a dielectric, magnetized cold plasma (MCP) and superconducting material by using well-known simple transfer matrix method. The MCP has considered right-hand and left-hand polarizations having positive (? B) and negative (- B) transverse magnetic ?eld, respectively. The transmittance of the ternary photonic crystals is analyzed by varying the angle of incidence, the magnetic ?eld, the electron density of the magnetized cold plasma, the temperature of the superconductor, the thickness of magnetized cold plasma and superconducting material for the right-hand and left-hand polarization structures. The transmittance of the ternary photonic crystal containing dielectric, magnetized cold plasma and superconducting material has tunable broadband and narrowband ?lters for the left-hand and right-hand polarizations, respectively. The magnetized cold plasma layer in the ternary photonic crystal also played an important role to form the tunable gap due to the transverse magnetic ?eld. The analysis of the transmittance of the ternary photonic crystal containing dielectric, magnetized cold plasma and superconducting materials has shown an innovative idea for the formation of the tunable broadband and the narrowband ?lters.
关键词： 1D ternary photonic crystal,Magnetized cold plasma,Tunable broadband and narrowband ?lters,Superconducting material
更新于2025-09-10 09:29:36