光子晶体平板透镜表面减反结构

报道了用来抑制光子晶体平板透镜表面反射的优化表面结构.当入射角小于48°,透镜的表面反射率可降到0.3%以下.     

Skin-like Omnidirectional Stretchable Platform with Negative Poisson's Ratio for Wearable Strain–Pressure Simultaneous Sensor

Conventional elastomeric polymers used as substrates for wearable platforms have large positive Poisson's ratios (≈0.5) that cause a deformation mismatch with human skin that is multidirectionally elongated under bending of joints. This causes practical problems in elastomer-based wearable devices, such as delamination and detachment, leading to poorly reliable functionality. To overcome this issue, auxetic-structured mechanical reinforcement with glass fibers is applied to the elastomeric film, resulting in a negative Poisson's ratio (NPR), which is a skin-like stretchable substrate (SLSS). Several parameters for determining the materials and geometrical dimensions of the auxetic-structured reinforcing fillers are considered to maximize the NPR. Based on numerical simulation and digital image correlation analysis, the deformation tendencies and strain distribution of the SLSS are investigated and compared with those of the pristine elastomeric substrate. Owing to the strain-localization characteristics, an independent strain-pressure sensing system is fabricated using SLSS with a Ag-based elastomeric ink and a carbon nanotube-based force-sensitive resistor. Finally, it is demonstrated that the SLSS-based sensor platform can be applied as a wearable device to monitor the physical burden on the wrist in real time.     

Double S-Shaped Polarization – Voltage Curve and Negative Capacitance from Al2O3-Hf0.5Zr0.5O2-Al2O3 Triple-Layer Structure

The negative capacitance (NC) effect, recently discovered in a fluorite-based ferroelectric thin film, has attracted great attention as a rescue to overcome the scaling limitations of the conventional memory and logic devices of highly integrated circuits. The NC effect manifesting an S-shaped polarization–voltage (P–V) curve is initially interpreted by a 1-dimensional Landau Ginzburg Devonshire (LGD) model. However, a series of recent studies have found that this effect can also be explained by the inhomogeneous stray field energy (ISE) model. In this study, by extending the ISE model in the ferroelectric (FE)-dielectric (DE) layered structure, an analytical model that considers the influence of the interfacial screening charge distribution is presented. This model showed that the NC effect in the FE-DE heterostructure can be manifested in various forms other than a single S-shaped P–V curve. In particular, a double S-shaped P–V curve is expected from the fully compensated anti-parallel domain structure, confirmed experimentally in the actual Al₂O₃/(Hf_0.5Zr_0.5)O₂/Al₂O₃ triple-layer structure. Furthermore, to reveal the origin of the double S-shaped P–V curve, a multidomain LGD model is presented. It is confirmed that this phenomenon is attributed to the evolution of inhomogeneous stray field energy.     

负阻异质结晶体管的模拟与实验

采用MBE方法生长了8nm基区的InGaP/GaAs双异质结材料,研制成具有负阻特性的异质结晶体管.在恒压恒流条件下均观察到了负阻特性并对其物理机制进行了讨论.推导出集电极电流Ic与VCE的关系表达式,讨论了负阻与器件结构和参数的关系.使用PSPICE模拟软件建立电路网表模型,代入推导出的IC-VCE公式进行模拟,模拟结果与器件的测量结果十分接近.     

Design and measurement of a 53 GHz balanced Colpitts oscillator

A 53 GHz Colpitts oscillator implemented in a SiGe:C BiCMOS technology is presented. Limited by a 26.5 GHz frequency analyzer, the oscillator was measured indirectly through an on-chip mixer. The mixer down-converted the oscillating frequency to an intermediate frequency (IF) below 26.5 GHz. By adjusting the local os-cillating (LO) frequency and recording the changes of IF frequency, the oscillator's output frequency (RF) was determined. Additionally, using phase noise theory of mixers, the oscillator's phase noise was estimated as-58 dBc/Hz at 1 MHz offset and the output power was about-21 dBm. The chip is 270×480 μm in size.     

含负折射率材料的1维光子晶体掺杂缺陷模研究

为了研究含有负折射率材料的光子晶体掺杂缺陷模的光学传输特性,利用传输矩阵理论进行数值分析.采用插入和替代两种方式对排列整齐的光子晶体进行掺杂,产生了缺陷模式.结果表明,引入正折射率缺陷只能在布喇格带隙中产生缺陷模,引入负折射缺陷能够同时在全方位光子带隙和布喇格带隙中产生缺陷模.同时研究了掺杂方式、入射方向、缺陷厚度、缺陷位置、缺陷类型对缺陷模式的影响,并对含有两层缺陷的光子晶体进行研究,得到两缺陷层的距离与带隙产生的关系,即距离越近越容易产生缺陷模式,且缺陷模的深度越深.这对于制造新型的全方位滤波器是有指导作用的.     

大功率金属陶瓷四极管的负阻振荡

文章对四极管的二次电子放射进行了阐释,分析了产生负阻振荡的机理,并结合DF-100A PSM短波广播发射机发生的负阻振荡故障实例,阐述了负阻振荡的危害及防止负阻振荡的方法。     

半绝缘GaAs光电导开关亚皮秒传输特性的研究

 本文应用Ensemble-Monte Carlo方法模拟了半绝缘GaAs(SI-GaAs)光电导开关基于Auston等效电路亚皮秒传输特性.从载流子在开关体内的动态特性出发,研究了光电导开关在飞秒激光脉冲触发下光电导传输特性、电介质弛豫特性、开关储能特性以及开关工作模式;分析了非线性光电导开关对光能阈值和偏置电场阈值要求的物理机制.     

双沟道实空间电子转移晶体管的设计、研制和特性测量

采用双沟道结构和GaAs衬底,成功设计研制了双沟道实空间电子转移晶体管.它具有RSTT典型的"A"形负阻I-V特性和较宽的平坦谷值区.通过栅压可改变各种负阻参数值,当栅压从0.6V增至1.0V时,PVCR的变化范围是2.1～10.6峰值电流跨导约为3×10-4 S.负阻参数VP,VV和开始产生负阻的栅极阈值电压都小于国际上同类器件的报道值,因此更适合低功耗的运用.     

直接补码阵列乘法的手工计算方法

直接补码阵列乘法器的工作原理是《计算机组成原理》课程的难点。教材在介绍定点数乘法时包括3种乘法器电路,其中在直接补码阵列乘法器中,被乘数和乘数均采用补码表示,符号位一起参加运算,积也采用补码形式表示。文中从补码与真值的关系出发,结合一般化的全加器形式,说明负权参加运算时的特征,并介绍如何将出现在数值位中的负权值在不改变真值的情况下向左移动,直至符号位。通过4种情况给出4个实例,说明使用直接补码阵列乘法的手工计算方法,从而揭示出直接补码阵列乘法器的工作原理。