Compact microstrip lowpass filter with sharp roll-off and wide stop-band

A microstrip lowpass filter with enhanced performance is developed. The studied filter is based on a novel patch resonator that features strong slow-wave effects, and can also implement either an improved roll-off or an enhanced stop-band. A demonstrator filter with 3 dB cutoff frequency fc ? 2.4 GHz is optimally designed, fabricated and measured. Results indicate that a roll-off of 92.5 dB/GHz together with a relative stop-band bandwidth of 135.5% (referred to a 30 dB suppression) is obtained while achieving a highest figure-of-merit of 10106. Both simulations and measurements are presented and compared.     

不同波长紫外光信号在高空大气通信中的性能分析

为分析高空紫外光通信性能,建立了高空太阳辐射分布模型;研究了不同波长紫外光的高空散射系数和吸收系数;考虑太阳辐射的背景光和接收端散粒噪声,对紫外光直视与非直视链路的损耗和信噪比进行了仿真分析.结果表明:在高空30 km以下,由太阳辐射产生的背景光远小于接收端散粒噪声;在7 km的高度上280 nm的信号光可实现距离为5 km、速率为10Mb/s的直视通信和距离1 km、速率50 kb/s、收发端仰角为20°的非直视通信.直视与非直视通信可以通过选择波长在“日盲区”两端的信号来减小臭氧对紫外光的吸收作用,提高信噪比;非直视通信还可以选择“日盲区”波长短的信号来增强散射效应,改善通信性能.     

Electronic band structures and optical properties of atomically thin AuSe: first-principle calculations

As a large family of 2D materials, transition metal dichalcogenides(TMDs) have stimulated numerous works owing to their attractive properties. The replacement of constituent elements could promote the discovery and fabrication of new nanofilm in this family. Using precious metals, such as platinum and palladium, to serve as transition metals combined with chalcogen is a new approach to explore novel TMDs. Also, the proportion between transition metal and chalcogen atoms is found not only to exist in conventional form of 1 : 2. Herein, we reported a comprehensive study of a new 2D precious metal selenide, namely AuSe monolayer. Based on density functional theory, our result indicated that AuSe monolayer is a semiconductor with indirect band-gap of 2.0 eV, which possesses superior dynamic stability and thermodynamic stability with cohesive energy up to–7.87 eV/atom. Moreover, it has been confirmed that ionic bonding predominates in Au–Se bonds and absorption peaks in all directions distribute in the deep ultraviolet region. In addition, both vibration modes dominating marked Raman peaks are parallel to the 2D plane.     

FAPbI3 Flexible Solar Cells with a Record Efficiency of 19.38% Fabricated in Air via Ligand and Additive Synergetic Process

Compared with silicon‐based solar cells, organic–inorganic hybrid perovskite solar cells (PSCs) possess a distinct advantage, i.e., its application in the flexible field. However, the efficiency of the flexible device is still lower than that of the rigid one. First, it is found that the dense formamidinium (FA)‐based perovskite film can be obtained with the help of N‐methyl‐2‐pyrrolidone (NMP) via low pressure‐assisted method. In addition, CH₃NH₃Cl (MACl) as the additive can preferentially form MAPbCl_3?xI_x perovskite seeds to induce perovskite phase transition and crystal growth. Finally, by using FAI·PbI₂·NMP+x%MACl as the precursor, i.e., ligand and additive synergetic process, a FA‐based perovskite film with a large grain size, high crystallinity, and low trap density is obtained on a flexible substrate under ambient conditions due to the synergetic effect, e.g., MACl can enhance the crystallization of the intermediate phase of FAI·PbI₂·NMP. As a result, a record efficiency of 19.38% in flexible planar PSCs is achieved, and it can retain about 89% of its initial power conversion efficiency (PCE) after 230 days without encapsulation under ambient conditions. The PCE retains 92% of the initial value after 500 bending cycles with a bending radii of 10 mm. The results show a robust way to fabricate highly efficient flexible PSCs.     

Characterization of Ni/Ho and Ni/Er fully silicided metal gates on SiO2 gate dielectric

This paper investigates the effects of Ho and Er on the sheet resistance and crystallinity of Ni(Ho) and Ni(Er) silicides, the work function (WF) modulation of Ni(Ho) and Ni(Er) fully silicided (FUSI) gate electrodes on SiO₂ dielectric, and the FUSI gated SiO₂/Si interface trap properties by using high-frequency capacitance-voltage (C-V) and photonic high-frequency C-V measurements. It was found that as the thickness percentage of rare earth (RE) metal in the Ni(Ho) or Ni(Er) increases, the sheet resistance of the silicide increases. The crystallinity decreases in the Ni(Ho) and Ni(Er) silicides, and the crystallinity decreases as the Ho thickness percentage increases. As the thickness percentage of Ho in the Ni(Ho) increases from 13% to 30%, the flatband voltage (V_FB) shift increases from −0.19 to −0.27 V. The V_FB shifts negatively 0.17 V due to 10% Er incorporation in the Ni(Er). The V_FB shift can be attributed to the effective WF decrease which may be due to the crystallinity decrease of Ni(Ho) and Ni(Er) FUSI. The interface trap density D_it calculated from the photonic high-frequency C-V curves is in good agreement with that calculated from the high-frequency and photonic high-frequency C-V curves. The Ho or Er addition does not increase the D_it.     

多TDI CCD拼接遥感相机异速成像抗干扰设计

多TDI CCD拼接相机在异速工作模式下,不同通道的CCD图像间会存在相互干扰现象,不同行频差会在图像上产生不同斜率、不同宽度的干扰斜条纹。为了解决此问题,文中对原设计电路系统进行了详细分析和优化设计。首先,从异速时序在不同行周期的相位差别上进行分析,异速模式下不同CCD成像电路时序间存在行频差异,导致各个行周期内CCD个别像元上与其他像元叠加的干扰不一致,是干扰斜条纹产生的原因。然后,采取优化关键信号布线方式、系统地和电源布置、去耦电容接地方式等多方面对电路系统进行了改进,优化多TDI CCD成像系统电路抗异速干扰设计。最后,对改进后的电路系统进行测试,去除干扰斜纹,并将图像均方根噪声水平由21.5 mV降低到4.2 mV。结果表明:采用抗干扰技术,有效地去除了通道间干扰斜纹,提高了图像质量。     

LTE无线移动通信系统加密算法验证

一种新的加密算法在提出到最终被采纳用于LTE无线移动通信系统,其间需要进行充分的验证和测试。文章阐述了目前无线移动通信系统所使用的加密算法所应满足的技术要求,并对加密算法、加载了加密算法的网络和设备的评估及验证提出了具体的指标和测试方法。     

Weighted Discriminator Function Based Unambiguous Tracking Method for Dual-Frequency Constant Envelope Modulated Signals

The dual-frequency constant envelope modulated (DCEM) signals, represented by alternative binary offset carrier signal, have obvious advantages in code tracking accuracy and anti-multipath performance compared with traditional binary phase shift keying signal, and are attracting more and more attention in the field of global navigation satellite system signal design. However, DCEM signal has a multiple-peaked auto-correlation function, which would lead to the tracking ambiguity problem. To deal with this problem, this paper proposes an unambiguous tracking method based on weighted discriminator function (WDF). This method uses the discriminator functions of noncoherent early minus late power (NELP) and sub carrier phase cancellation (SCPC) to generate a linear WDF without no false-lock points. In addition, a simplified version of the proposed WDF method is also provided for interoperable application. The theoretical code tracking error in thermal noise is derived out and verified. The performance of the proposed WDF is evaluated and compared with SCPC and pseudo correlation function methods with the help of simulation. Results show that our method has a significant improvement in code tracking accuracy. Not only the ambiguity threat is efficiently removed, but also the outstanding performance of DCEM signal is maintained.     

透明介质材料的超快激光微纳加工研究进展

透明介质材料具有高透光性、高耐热性和良好的耐腐蚀性,被广泛应用于航空航天、微电子器件和光学元件等领域,这些应用对透明介质材料微纳加工的精度与质量提出了一定的要求。超快激光具有超高的峰值强度与超短的脉冲持续时间,可突破衍射极限并极小化热影响区,具有出色的加工精度与加工质量,为透明介质材料的微纳尺度加工提供了多样化的手段。综述了透明介质材料的超快激光微纳加工研究进展,包括超快激光加工透明介质材料的内部结构、相关机理和应用领域三个方面,并对透明介质材料的超快激光微纳加工进行了总结与展望。     

Vanadium Doping Enhanced Electrochemical Performance of Molybdenum Oxide in Lithium‐Ion Batteries

Molybdenum trioxide (MoO₃) suffers from poor conductivity, a low rate capability, and unsatisfactory cycling stability in lithium‐ion batteries. The aliovalent ion doping may present an effective way to improve the electrochemical performances of MoO₃. Here, it is shown, by first‐principle calculations, that doping MoO₃ with V by 12.5% can modulate significantly electronic structure and provide a small diffusion barrier for enhancing the electrochemical performance of MoO₃. The ultralong Mo_0.88V_0.12O_2.94 nanostructures, which retain the h‐MoO₃ structure and present an exceptionally high conductivity and fast ionic diffusion due to the substitution of V, facilitating lithiation/delithiation behavior, and induce a fine nanosized structure with a reduced volume change are prepared. As a result, the stress and strain are alleviated during the Li‐ion intercalation/deintercalation processes, improving the cycling stability and rate capability. Such a large improvement in the electrochemical properties can be ascribed to the stabilizing effect of V, the small migration energy barrier, and short diffusion path, which arise from the introduction of V into MoO₃. The unique engineering strategy and facile synthesis route open up a new avenue in modifying and developing other species of electrode materials.