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A 1 to 32 GHz broadband multi-octave receiver for monolithic integrated vector network analyzers in SiGe technology
摘要： A multi-octave receiver chain is presented for the use in a monolithic integrated vector network analyzer. The receiver exhibits a very wide frequency range of 1–32 GHz, where the gain meets the 3 dB-criterion. The differential receiver consists of an ultra-wideband low noise amplifier, an active mixer and an output buffer and exhibits a maximum conversion gain (CG) of 16.6 dB. The main design goal is a very flat CG over five octaves, which eases calibration of the monolithic integrated vector network analyzer. To realize variable gain functionality, without losing much input matching, an extended gain control circuit with additional feedback branch is shown. For the maximum gain level, a matching better than ?10 dB is achieved between 1–28 GHz, and up to 30.5 GHz the matching is better than ?8.4 dB. For both, the input matching and the gain of the LNA, the influence of the fabrication tolerances are investigated. A second gain control is implemented to improve isolation. The measured isolations between RF-to-LO and LO-to-RF are better than 30 dB and 60 dB, respectively. The LO-to-IF isolation is better than 35 dB. The noise figure of the broadband receiver is between 4.6 and 5.8 dB for 4–32 GHz and the output referred 1-dB-compression-point varies from 0.1 to 4.3 dBm from 2–32 GHz. The receiver draws a current of max. 66 mA at 3.3 V.
关键词： RF front-ends,active circuits,ultra broadband receiver
更新于2025-09-23 15:23:52
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Ultra-broadband, sensitive and fast photodetection with needle-like EuBiSe3 single crystal
摘要： Ultra-broadband photodetection has been a hot topic with the rapid development of materials science and the application requirements for communication, imaging and sensing. Photodetectors based on bandgap-independent bolometry are promising candidates for detection of light from the ultraviolet to the terahertz range. Here we report a photothermoelectric detector made of an alloy of EuBiSe3 single crystal. The device shows room-temperature self-powered photoresponse from ultraviolet (375 nm) to terahertz (163 μm) with nearly uniform sensitivity against wavelength and fast response speed. Thanks to the large thermoelectric power (Seebeck coefficient) of EuBiSe3, the photovoltage responsivity derived from the incident (not absorbed) power reaches as high as 1.69 V/W at 405 nm without any bias voltage, and exceeds 0.59 V/W even at terahertz frequencies, with noise-equivalent power below 1 nW/√Hz, which is 1–2 orders of magnitude lower than reported photothermoelectric detectors. The response time is around 200 ms, nearly two orders of magnitude faster than silicon-based heterojunction ultra-broadband photodetectors and on the same order as the millimetric-scale graphene- and carbon nanotube-based bolometric photodetectors. In addition, the as-grown EuBiSe3 crystal possesses a unique needle-like shape, intrinsically facilitating integration of the detector. Our work demonstrates that improved thermoelectric materials hold great promise for room-temperature high-performance broadband photodetection.
关键词： EuBiSe3,photothermoelectric,ultra-broadband,sensitive,photodetector,self-powered
更新于2025-09-23 15:22:29
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Preparation of ultra-broadband antireflective coatings for amplifier blast shields by a sol–gel method
摘要： A type of λ/4–λ/4 ultra-broadband antire?ective coating has been developed using modi?ed low refractive silica and high refractive silica layers by a sol–gel dip coating method for ampli?er blast shields of the Shen Guang II high power laser facility (SG-II facility). Deposition of the ?rst layer (high refractive index silica) involves baking at 200 ?C in the post-treatment step. The second layer (low refractive index, n = 1.20) uses low refractive index silica sol modi?ed by acid catalysis. Thermal baking at temperatures no less than 500 ?C for 60 min offers chemical stability, ethanol scratch resistance, and resistance to washing with water. The average residual re?ection of dual-side-coated fused silica glass was less than 1% in the spectral range from 450 to 950 nm. Transmission gain has been evaluated by taking into account angular light, and the results show that the transmission gain increases with increasing light incidence. Even at 60?, the transmission spectrum of the broadband antire?ective coating effectively covered the main absorption peak of Nd:glass.
关键词： blast shields,ampli?er,ultra-broadband,sol–gel,antire?ective coating
更新于2025-09-23 15:21:21
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Self-powered ultra-broadband and flexible photodetectors based on the bismuth films by vapor deposition
摘要： Bismuth (Bi), as a topological semi-metallic material, has received widespread attention on account of its fascinating properties. Here, Bi films were successfully grown through a direct and facile vapor deposition method on 300 nm SiO2/Si (SiO2) and polyimide (PI) substrates. The Bi films were utilized further to fabricate rigid and flexible photodetectors. The rigid photodetector based on Bi/SiO2 show fast, highly stable, self-powered, and ultra-broadband photoresponses. The flexible Bi/PI photodetector exhibits durability and reproducibility in photoresponse behaviors under bending with various curvature radius and after hundreds of bending cycles. Our results demonstrated that the Bi films by vapor deposition have great application potentials in next generation of optoelectronic devices.
关键词： flexible,vapor deposition,ultra-broadband,self-powered,photodetector,Bi films
更新于2025-09-23 15:19:57
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DEVELOPMENT OF AN EQUIVALENT CIRCUIT MODEL OF A FINITE GROUND COPLANAR WAVEGUIDE INTERCONNECT IN MIS SYSTEM FOR ULTRA-BROADBAND MONOLITHIC ICS
摘要： An equivalent circuit model of a ?nite ground plane coplanar waveguide (FGCPW) interconnect in a metal-insulator-semiconductor (MIS) system for an ultra-broadband monolithic IC is proposed and illustrated. An e?ective substrate considering Maxwell-Wagner Polarization is suggested and demonstrated. The method of modeling the weak skin e?ect of the conductor is presented. The accuracy of the equivalent circuit model is evaluated. This proposed FGCPW interconnect equivalent circuit model enables a quick and e?cient time domain simulation to estimate the time delay and bandwidth of ultra-broadband ICs.
关键词： FGCPW interconnect,MIS system,equivalent circuit model,weak skin effect,Maxwell-Wagner Polarization,ultra-broadband monolithic IC
更新于2025-09-23 15:19:57
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A flexible and ultra-broadband terahertz wave absorber based on graphenea??vertically aligned carbon nanotube hybrids
摘要： Electromagnetic wave absorbers are essential devices in imaging, wireless communication and energy harvesting systems. In this paper, we propose and experimentally demonstrate a flexible and ultra-broadband terahertz (THz) wave absorber based on graphene-vertically aligned carbon nanotube (G-VACNT) hybrids. The THz absorber consists of Cu/PDMS/graphene/VACNT functional layers on PET substrate. Measured results show a 100% qualified operating bandwidth (i.e., absorptance >0.9) and an average power absorptance of 0.986 within the 0.2-3.0 THz range. The absorber also exhibits good absorption performances for a wide range of incident angles up to 60°, and can function normally in different bending states due to its excellent flexibility. The incoming energy of THz waves absorbed by the G-VACNT hybrids results in a temperature increase whose spatial distribution is corresponding to the profile of incident THz beam, providing an efficient and low cost approach for THz beam profiling, collimation and focusing. This work paves the way for the development of large-scale and broadband THz wave absorbers.
关键词： Vertically aligned carbon nanotube,Ultra-broadband,Graphene,Flexible,Terahertz wave absorber
更新于2025-09-23 15:19:57
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Thermal Localization Enhanced Fast Photothermoelectric Response in a Quasi-one-dimensional Flexible NbS <sub/>3</sub> Photodetector
摘要： Ultra-broadband photodetection is crucial for various applications like imaging and sensing, and has become a hot research topic in recent years. However, most of the reported ultra-broadband photodetectors can only cover the range from ultraviolet to infrared, which is insufficient. Herein, a photothermoelectric (PTE) detector made of NbS3 is reported. The device shows a considerable performance from ultraviolet to terahertz. For all examined wavelengths, the photoresponsivities are all larger than 1 VW-1 while the response time is less than 10 ms, much shorter than the reported ultra-broadband photodetectors made of millimetric scale graphene, ternary chalcogenide single crystal and other materials. The extraordinary performance is fully discussed and can be attributed to the thermal localization enhanced PTE effect. Due to the short thermal decay length and low thermal loss, the heat generated by the illumination is localized in only a micrometer scale along the channel and thus a strong PTE response is produced. In addition, the fabricated device also demonstrates robust flexibility and stability. Thanks to the quasi-one-dimensional structure, the NbS3 crystal is easy to be scaled down and thus intrinsically facilitate the integration of detectors. With these favorable merits, the quasi-one-dimensional NbS3 crystal holds promising potential in high-performance, ultra-broadband photodectors.
关键词： photodetection,photothermoelectric effect,ultra-broadband,thermal localization,NbS3
更新于2025-09-19 17:13:59
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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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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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A tunable ultra-broadband linear-to-circular polarization converter containing the graphene
摘要： In this paper, a tunable ultra-broadband linear-to-circular polarization converter (LCPC) in terahertz regime containing the graphene is proposed, which are composed of two "I"-shaped gold resonators, a strip-shaped graphene sheet, two dielectric layer and a bottom gold reflector. The proposed LCPC can convert the linearly polarized wave into circularly polarized wave in an ultra-broadband frequency range which can be expanded to the lower frequencies by decreasing the Fermi energy (??f ) of the graphene in terahertz region. When ??f = 0.4 eV, 0.6 eV, 0.8 eV and 1.0 eV, the axial ratio band of the proposed LCPC which is less than 3 dB are covered 0.9248～2.2880 THz, 0.9408～2.2893 THz, 0.9665～2.2803 THz, and 0.9746～2.2780 THz, whose relative bandwidths are 84.86%, 83.49%, 80.93% and 80.15%, respectively. The maximum 3 dB axial ratio band is located at 0.9248～2.2880 THz and its relative bandwidth is 84.86% at the case of ??f = 0.4 eV. The polarization conversion rate curves, reflection phase curves, surface current and electric field diagrams are analyzed to elucidate the physical characteristics of the presented LCPC. In addition, the effect of parameters a, b and c on the axial ratio band are also discussed, respectively. This design offers an effective way to realize the reconfigurable LCPC, and also has enormous potential value in realizing the THz devices.
关键词： Graphene,Ultra-broadband,Tunable line-to-circular polarization converter
更新于2025-09-04 15:30:14