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A 28-GHz Low-Power Vector-Sum Phase Shifter Using Biphase Modulator and Current Reused Technique
摘要： In this letter, we present a low-power vector-sum phase shifter for upcoming 5G communication at 28 GHz. The ±I/±Q signals for phase synthesis by vector adder (VA) are generated by a 90° coupler and two re?ection-type biphase modulators. Modulators are only biased at 0 and 1.8 V to avoid large insertion loss near their phase reversal region. Our proposed single-ended two branches quadrature structure can avoid the differential variable gain ampli?er and achieve low power and compact area. In addition, we use the current reused technique to connect VA and output buffer to save dc power and suppress a change in output impedance among different phase states. The measured average peak gain is ?3.75 dB at 29.25 GHz. Across all phase states, the measured IP1 dB is better than 5 dBm. The 3-dB bandwidth of S21 is 27–33 GHz. Input and output return losses are also better than 10 dB at this frequency range. Total dc power consumption is only 6.6 mW for 1.8 V supplied voltage. To the best of our best knowledge, this phase shifter has low dc power and compact area at K-band and Ka-band.
关键词： vector adder (VA),phase-invertible variable attenuators (PIVAs),Biphase modulator (BM),current reused technique,vector-sum phase shifter (VSPS),buffer ampli?er (BA)
更新于2025-09-23 15:21:01
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[Lecture Notes in Electrical Engineering] Microelectronics, Electromagnetics and Telecommunications Volume 521 (Proceedings of the Fourth ICMEET 2018) || Performance Analysis of a PV System Using HGB Converter
摘要： A photovoltaic array based system using a transformer-less high gain interleaved dc–dc boost converter is proposed in this paper. The renewable energy sources such as photovoltaic array and fuel cells provide only a time-varying and low dc voltage which cannot be directly used as the front-end for the loads or dc grid. Hence, there is a need for power electronic interfaces for matching the environmental-friendly sources of energy to the load. The interleaved converter used in the proposed system has the capability of canceling the input current ripple without increasing the component counts in the converter using a preselected duty cycle. Also, the large voltage gain and high ef?ciency of the converter are the added advantages to the proposed system. Analysis, simulation, and experimental investigation of the system proposed were carried out and the results are compared to validate the proposed system effectiveness.
关键词： Photovoltaic array,Interleaving technique,A high gain boost converter,Transformer-less dc–dc converter
更新于2025-09-23 15:21:01
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Crystal growth and optical properties of Ca <sub/>3</sub> TaGa <sub/>3</sub> Si <sub/>2</sub> O <sub/>14</sub> single crystals
摘要： Transparent yellowish Ca3TaGa3Si2O14 single crystals were grown in Ar+(0.5–3)% O2 along the Y-axis by the Czochralski technique. The structural perfection of Ca3TaGa3Si2O14 samples was studied by X-ray topography and rocking curve methods. Topograms and rocking curves along the surfaces of the Y- and Z-cuts were studied before and after surface treatments (polishing and etching). Transmittance spectra were measured in the wavelength range of 200–3300 nm. Optical anisotropy was studied along the X- and Z-axes, and dichroism along the X-axis. The dispersions of the refractive index No and speci?c rotation of the polarization plane were determined using spectrophotometric methods.
关键词： optical properties,Czochralski technique,single crystals,Ca3TaGa3Si2O14,X-ray topography
更新于2025-09-23 15:21:01
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HIGHLY SELECTIVE LOSSY DUAL-BAND BANDSTOP FILTER SYNTHESIS AND DESIGN BASED ON PREDISTORTION HYBRID DUAL-BAND ELLIPTIC REFECTION FUNCTION
摘要： This paper demonstrates a new class of highly selective bandstop ?lter based on cascading two identical lossy hybrid dual-band bandstop ?lters of low resonator Q factor. Each ?lter is synthesized based on multi-stage predistortion re?ection mode technique. To demonstrate the approach, 4th order hybrid dual-band elliptic ?lter network which is a product of elliptic lowpass and highpass network functions has been predistorted and synthesized with low calculated Q factor. The lossy dual-band bandstop ?lters are fabricated and realized on microstrip planar structure. Both theoretical and experimental results clearly show good agreements with two stopband rejections up to 35 dB for one stage and 50 dB for two stages with passband loss of more than 10 dB.
关键词： microstrip planar structure,highly selective bandstop ?lter,predistortion re?ection mode technique,lossy hybrid dual-band bandstop ?lters
更新于2025-09-23 15:21:01
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RCS REDUCTION USING A MINIATURIZED UNI-PLANAR ELECTROMAGNETIC BAND GAP STRUCTURE FOR CIRCULARLY POLARIZED MICROSTRIP ANTENNA ARRAY
摘要： In this paper, a new method for radar cross section (RCS) reduction of circularly polarized (CP) microstrip antenna array with small element spacing is proposed. By employing the element rotation technique and loading EBG structures, the in-band and out-of-band RCSs are reduced simultaneously despite the extreme small space between array elements. The simulated results show that the proposed antenna has an average RCS reduction over 10 dB in the X-band for x-polarized and y-polarized incident waves impinging from normal direction compared to the original CP microstrip antenna array, indicating a fractional bandwidth of 40%. The maximum RCS reduction is over 25 dB. Meanwhile, the radiation performance of the proposed antenna array is kept.
关键词： RCS reduction,EBG structures,circularly polarized microstrip antenna array,element rotation technique
更新于2025-09-23 15:21:01
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Computation of Propagating and Non-Propagating Lamb-Like Wave in a Functionally Graded Piezoelectric Spherical Curved Plate by an Orthogonal Function Technique
摘要： Non-propagating waves have great potential for crack evaluation, but it is difficult to obtain the complex solutions of the transcendental dispersion equation corresponding to the non-propagating wave. This paper presents an analytical approach based on the orthogonal function technique to investigate non-propagating Lamb-like waves in a functionally graded piezoelectric spherical curved plate. The presented approach can transform the set of partial differential equations for the acoustic waves into an eigenvalue problem that can give the generally complex wave numbers and the field profiles. A comparison of the obtained results with the well-known ones in plates is provided. The obtained solutions of the dispersion equation are shown graphically in three dimensional frequency-complex wave number space, which aids in understanding the properties of non-propagating waves better. The properties of the guided wave, including real, purely imaginary, and complex branches in various functionally graded piezoelectric spherical curved plates, are studied. The effects of material piezoelectricity, graded fields, and mechanical and electrical boundary conditions on the dispersion characteristics, are illustrated. The amplitude distributions of displacement and electric potential are also discussed, to analyze the specificities of non-propagating waves.
关键词： dispersion,orthogonal function technique,displacement distribution,functionally graded piezoelectric material,non-propagating wave
更新于2025-09-23 15:21:01
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High performance UV photodetector based on MoS2 layers grown by pulsed laser deposition technique
摘要： Highly efficient ultraviolet (UV) photodetector based on MoS2 layers has been fabricated using pulsed laser deposition (PLD) technique. Systematic layer dependent photoresponse studies have been performed from single layer to 10 layers of MoS2 by varying the laser pulses to see the effect of the number of layers on the photoelectrical measurements. Raman and Photoluminescence studies have been carried out to ensure the growth of high-quality MoS2 layers. Layers of MoS2 grown at 100 pulses were found to exhibit the characteristic Raman phonon modes i.e. E1 2g and A1g at 383.8 cm-1 and 405.1 cm-1 respectively and Photoluminescence (PL) spectra show B exciton peak for MoS2 at around 625 nm suggesting the growth of high-quality MoS2 layers. Atomic force microscopy (AFM) thickness profiling and cross sectional-high resolution transmission electron microscopy (HRTEM) analysis gives the thickness of grown MoS2 to be 2.074 nm and 1.94 nm, respectively, confirming the growth of trilayers of MoS2. X-ray photoelectron spectroscopy (XPS) spectra of the grown trilayer sample show characteristic peaks corresponding to Molybdenum and Sulphur doublet (Mo4+ 3d5/2,3/2 and S 2p3/2,1/2) confirming the chemical state of pure MoS2 phase without the presence of any Molybdenum oxide state. Dynamic photoelectrical studies with Indium Tin Oxide (ITO) as contact electrode upon UV laser illumination show superior responsivity of 3×104 A/W at 24 μW optical power of the incident laser (λ=365 nm) and very high detectivity of 1.81×1014 Jones at a low applied bias of 2 V. The obtained results are highly encouraging for the realization of low power consumption and highly efficient UV photodetectors based on MoS2 layers.
关键词： Pulsed laser deposition technique (PLD),2D material,UV photodetector,ITO electrode,cross-sectional TEM,Raman,MoS2 layers,XPS,AFM
更新于2025-09-23 15:19:57
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GaAs solar cells grown on intentionally contaminated GaAs substrates
摘要： III-V materials such as GaAs and GaInP have some of the best electronic and optical properties of any semiconductor materials, but deposition of these materials relies on high-quality single crystal GaAs substrates for their superior performance. Unfortunately, the cost of these substrates makes these high-efficiency devices only accessible in high-value or niche markets. Here, we explore the effect of growing bulk GaAs crystals with lower purity input materials in order to reduce their cost. We observe that intentional impurities added to the melt before the crystal growth occurs segregate to the top of the boule. Single junction GaAs solar cells grown on substrates made from contaminated boules showed no performance degradation compared to a high-purity control substrate. These results suggest that lower purity Ga and As source materials can be used during crystal growth to reduce the cost of substrates.
关键词： B2. Semiconducting III-V materials,A2. Gradient freeze technique,A1.Substrates,B3. Solar Cells
更新于2025-09-23 15:19:57
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Efficient generation of nitrogen vacancy centers by laser writing close to the diamond surface with a layer of silicon nanoballs
摘要： We proposed a method to effectively fabricate negatively charged nitrogen vacancy (NV?) centers close to the diamond surface by applying femtosecond laser writing technique. With a thick layer of silicon (Si) nanoballs coated, diamond surface was irradiated by high-fluence femtosecond laser pulses. A large number of NV? centers were created around the laser ablation crater area without thermal annealing. The distribution of the NV? centers was expanded to about 50 μm away from the crater center. To demonstrate the function of Si nanoballs, we performed the exactly same laser illumination process on the bare region of the sample surface. In this case, only a few NV? centers were generated around ablation crater. At distance of 32 μm away from crater centers, the NV? density for the case with nanoballs was up to 15.5 times higher compared to the case without nanoballs. Furthermore, we also investigated the influence of laser fluence and pulse number on the NV? density for the case with Si-nanoball layer. Finally, the formation mechanism of NV? centers and the role of Si nanoballs were explained via Coulomb explosion model. The method is demonstrated to be a promising approach to efficiently and rapidly fabricate NV? centers close to the surface of the diamond, which are significant in quantum sensing. Furthermore, the results provide deep insights into complex light-matter interactions.
关键词： single emitters,nitrogen vacancy centers in diamond,silicon nanoballs,femtosecond laser technique
更新于2025-09-23 15:19:57
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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) - High-Efficiency Corrugated Monocrystalline Silicon Solar Cells with Multi-Directional Flexing Capabilities
摘要： High efficiency, lightweight and low cost flexible solar cells have attracted a growing interest in the last decades due to their increased applications. Here, we show high-efficiency (19%) and large scale (5 × 5 inch wafer) monocrystalline silicon solar cells with multi-directional flexing capabilities. The flexing of rigid solar cells with interdigitated back contacts is achieved using a photolithography-less corrugation technique. Results show that linear patterns enable flexibility in one direction with a minimum bending radius of 5 mm while diamond patterns result in multi-directional flexibility with different minimum bending radii and robust electrical performance.
关键词： monocrystalline silicon,multi-directional flexing,flexible solar cells,corrugation technique,high efficiency
更新于2025-09-23 15:19:57