A Complex BPF with On Chip Auto-tuning Architecture for Wireless Receivers

A 3(rd) order complex band-pass filter (BPF) with auto-tuning architecture is proposed in this paper. It is implemented in 0.18um standard CMOS technology. The complex filter is centered at 4.092MHz with bandwidth of 2.4MHz. The in-band 3(rd) order harmonic input intercept point (IIP3) is larger than 16.2dBm, with 50 Omega as the source impedance. The input referred noise is about 80uV(rms). The RC tuning is based on Binary Search Algorithm (BSA) with tuning accuracy of 3%. The chip area of the tuning system is 0.28 x 0.22 mm(2), less than 1/8 of that of the main-filter which is 0.92 x 0.59 mm(2). After tuning is completed, the tuning system will be turned off automatically to save power and to avoid interference. The complex filter consumes 2.6mA with a 1.8V power supply.

A Complex BPF with On Chip Auto-tuning Architecture for Low-IF Receivers

A 3(rd) order complex band-pass filter (BPF) with auto-tuning architecture is proposed in this paper. It is implemented in 0.18 mu m standard CMOS technology. The complex filter is centered at 4.092MHz with bandwidth of 2.4MHz. The in-band 3(rd) order harmonic input intercept point (IIP3) is larger than 19dBm, with 50 Omega as the source impedance. The input referred noise is about 80 mu V-rms. The RC tuning is based on Binary Search Algorithm (BSA) with tuning accuracy of 3%. The chip area of the tuning system is 0.28x0.22mm(2), less than 1/8 of that of the main-filter which is 0.92x0.59mm(2). After tuning is completed, the tuning system will be turned off automatically to save power and to avoid interference. The complex filter consumes 2.6mA with a 1.8V power supply.

Uncooled Submarine Pump Laser Module at 980 nm

We present a new generation 980 nm submarine pump module that consists of a hermitically sealed 8-pin ceramic MiniDIL package without thermo-electric cooler.

A New Technique for Side Pumping of Double-Clad Fiber Lasers

We report a new technique, called SAP, for side pumping of double-clad, rare-earth-doped fiber lasers using fiber-coupled pump sources. The highest coupling efficiency can even exceed 92% in theory with this structure.

An Improved Selective Area Growth Method in Fabrication of Electroabsorption Modulated Laser

An improved selective area growth (SAG) method is proposed to better the fabrication and performance of the Electroabsorption modulated laser The typical threshold current of the EML is 18mA, and the output power is 5.6mW at EAM facet.

Optical and electrical investigation of low dimensional self-assembled InAs quantum dot field effect transistors

Self-assembled InAs QD dot-in-a-well (DWELL) structures were grown on GaAs substrate by MBE system, and heterojunction modulation-doped field effect transistor (MODFET) was fabricated. The optical properties of the samples show that the photoluminescence of InAs/GaAs self-assembled quantum dot (SAQD) is at 1.265 mu m at 300 K. The temperature-dependence of the abnormal redshift of InAs SAQD wavelength with the increasing temperature was observed, which is closely related with the inhomogeneous size distribution of the InAs quantum dot. According to the electrical measurement, high electric field current-voltage characteristic of the MODFET device were obtained. The embedded InAs QD of the samples can be regard as scattering centers to the vicinity of the channel electrons. The transport property of the electrons in GaAs channel will be modulated by the QD due to the Coulomb interaction. It has been proposed that a MODFET embedded with InAs QDs presents a novel type of field effect photon detector.

Lateral intersubband photocurrent study on InAs/InAlas/InP self-assembled nanostructures

We present lateral intersubband photocurrent (PC) study on self-assembled InAs/InAIAs/InP(001) nanostructures in normal incidence. With the help of interband excitation, a broad PC signal has been observed in the photon energy range of 150-630 meV arising from the bound-to-continuum intersubband absorption in the InAs nanostructures. The large linewidth of the intersubband PC signal is due to the size inhomogeneity of the nanostructures. With the increase of the interband excitation the intersubband PC signal firstly increases with a redshift of PC peak and reaches its maximum, then decreases with no peak shift. The increase and redshift of the PC signal at low excitation level can be explained by the state filling effect. However, the decrease of PC signal at high excitation level may be due to the change of the mobility and lifetime of the electrons. The intersubband PC signal decreases when the temperature is increased, which can be explained by the decrease of the mobility and lifetime of the electrons and the thermal escape of electrons.

Corrugated surfaces formed on GaAs (331)a substrates: The template for laterally ordered InGaAs nanowires

Morphology evolution of high-index (331)A surfaces during molecular beam epitaxy (MBE) growth have been investigated in order to uncover their unique physic properties and fabricate spatially ordered low dimensional nanostructures. Atomic Force Microscope (AFM) measurements have shown that the step height and terrace width of GaAs layers increase monotonically with increasing substrate temperature in conventional MBE. However, this situation is reversed in atomic hydrogen-assisted MBE, indicating that step bunching is partly suppressed. We attribute this to the reduced surface migration length of Ga adatoms with atomic hydrogen. By using the step arrays formed on GaAs (331)A surfaces as the templates, we fabricated laterally ordered InGaAs self-aligned nanowires.

Tuning of emission wavelength of InAs/GaAs quantum dots sandwiched by combination layers

We investigate about controlling of photoluminescence (PL) wavelengths of InAs/GaAs self-assembled quantum dots (QDs) sandwiched with combination strained-buffer layer (CSBL) and combination strained-reducing layer (CSRL). The emission peak position of QDs is red-shifted to 1.37 mu m. The density of the QDs is increased to 1.17x10(10) cm(-2). It is indicated that optical properties of QDs could be improved by optimizing of the buffer and covering layers for the QDs. These results may provide a new way to further developing GaAs-based 1.3 mu m light sources.

Surface morphology evolution of strained InAs/GaAs(331)a films

Surface morphology evolution of strained InAs/GaAs(331)A films was systematically investigated in this paper. Under As-rich conditions, InAs elongated islands aligned along [1 (1) over bar0] are formed at a substrate temperature of 510 degrees C. We explained it as a result of the anisotropic diffusion of adatoms. Under In-rich conditions, striking change has occurred with respect to the surface morphology of the InAs layers. Instead of anisotropic InAs elongated islands, unique island-pit pairs randomly distributed on the whole surface were observed. Using cooperative nucleation mechanisms proposed by Jesson et al. [Phys. Rev. Lett. 77, 1330 (1996)], we interpret the resulting surface morphology evolution.

Production of biodiesel from soapstock using an ion-exchange resin catalyst

The feasibility of biodiesel production from soapstock containing high water content and fatty matters by a solid acid catalyst was investigated. Soapstock was converted to high-acid acid oil (HAAO) by the hydrolysis by KOH and the acidulation by sulfuric acid. The acid value of soapstock-HAAO increased to 199.1 mg KOH/g but a large amount of potassium sulfate was produced. To resolve the formation of potassium sulfate, acid oil was extracted from soapstock and was converted to HAAO by using sodium dodecyl benzene sulfonate (SDBS). The maximum acid value of acid oil-HAAO was 194.2 mg KOH/g when the mass ratio of acid oil, sulfuric acid, and water was 10:4:10 at 2% of SDBS. In the esterification of HAAO using Amberylst-15, fatty acid methyl ester (FAME) concentration was 91.7 and 81.3% for soapstock and acid oil, respectively. After the distillation, FAME concentration became 98.1% and 96.7% for soapstock and acid oil. The distillation process decreased the total glycerin and the acid value of FAME produced a little.

直接甲醇燃料电池阳极催化剂及甲醇氧化稀土助催化剂剂研究

燃料电池以其高效、环境友好的发电方式，被誉为21世纪的能源技术。其中，直接甲醇燃料电池（DMFC）更以燃料甲醇来源丰富，价格低廉，储存、携带方便而成为近年的研究热点。但是，DMFC在其实用化之前还需要解决一些重要问题，其中的关键之一就是高性能的贵金属催化剂的研究。我们知道，甲醇的电化学活性要低于氢气三个数量级；而且甲醇在R表面进行电化学氧化时，其中间解离吸附产物会造成贵金属催化剂中毒，显著降低了催化剂的活性。因此，要使DMFC具有相当高的电流密度和运行稳定性，就需要对贵金属催化剂制备进行不断的研究和改进。在本文的工作中，主要从Pt/C催化剂的制备方法、新型碳纳米管载体、稀土助催化剂等三个方面进行了研究和探索，取得的具体结果如下：1．Pt／C催化剂制备方法的研究与改进（1）在本组已有的研究结果基础上，对预沉积还原法进行了一些改进，采用原子吸收光谱（AAS）进行表征，发现Pt的利用率得到了明显的提高。采用X射线衍射。（RD）、透射电子显微镜（TEM）和BET表征铂的粒径、晶态结构和催化剂特性，分析表明，经过改进的预沉积还原法制备的催化剂仍然具有良好的分散性、较小的粒径、较低的晶态结构和良好的催化剂特性，电化学测试证明其性能要优于同等的E-TEK催化剂。（2）借鉴冶金学中的相关技术，提出了一种新的Pt/C催化剂制备方法一程序升温焙烧法。该方法的具体步骤增强了金属催化剂粒子和碳载体之间的相互作用力，提高了碳载体的导电性，并且形成了部分有利于催化反应进行的活性晶态结构。得到的R／C催化剂获得了近似E-TEK催化剂的催化活性，在具体方法上仍有改进的潜力。采用了同（1）的催化剂表征方法。2．甲醇电化学氧化稀土助催化剂研究在直接甲醇燃料电池Pt/C催化剂的研究过程中，一个重要的方面就是助催化剂的研究，并且已经得到了较好的结果。本工作选用了稀土元素为研究对象，因为稀土元素属于过渡金属，具有丰富的d电子轨道，易于和金属形成强的类化学键的吸附作用，并且能够和有机小分子形成多种配位化合物。经过初步的工作，发现了有些稀土离子如Sm3+能够在Pt表面吸附并且对甲醇电化学氧化具有较稳定的促进作用，采用循环伏安法，计时电流，交流阻抗等电化学方法进行了表征。根据实验结果，对其反应机理进行了初步的探讨。3．碳纳米管（CNTs）作为贵金属催化剂载体的研究碳纳米管（CNTs）由于其结构上的特殊性（径向尺寸为纳米量级，轴向尺寸为微米量级）而表现出典型的一维量子材料，同时具有较高的机械强度和超常的电学性能，能够为化学反应提供纳米级的反应场所，因此受到了化学界包括电化学研究人员的极大关注。已经在作为贵金属催化剂载体方面进行了一些研究，本工作的主要内容就是针对Pt/CNTs催化剂对碳纳米管的要求，对其预处理方法进行了改进，采用了如（1）中的催化剂表征方法和（2）中的相关电化学方法进行测定，发现碳纳米管作为贵金属催化剂载体时，对它的纯化处理方法的不同明显地影响了其载体性质和催化剂的活性。

镍-金属氢化物电池新型负极材料研究

贮氢合金是镍一金属氢化物电池的核心材料，其综合性能的改善是提高镍一金属氢化物电池性能的关键。本研究以探索镍一金属氢化物电池新型负极材料为目的，以非ABS型贮氢合金为研究对象，采用X射线衍射、Rietveld分析、恒电流充／放电、P-C-T曲线及线性微极化等方法，从基础和潜在应用等方面详细研究了非ABS型合金的结构与电化学性能。对La-Ni体系中非ABS型二元合金的结构和电化学性能的研究表明，LaNi_(228)具有最优异的高倍率充电性能；La_2Ni_7合金电极的高倍率放电性能最佳；La_7Ni_3在低温条件下表现出较好的放电性能。然而，所有得到的La-Ni合金电极容量远低于其理论容量。因此，必须通过进一步研究，如元素取代、热处理、表面处理等来提高其电化学容量。对RENi_3（RE＝La，Ce，Pr，Nd，Sm，Gd，Th，Dy，Ho，Er，Y）研究表明：YNi_3合金因其具有最大的晶胞体积，最小的密度，而表现出最好的高倍率充／放电性能及低温放电性能，但其高温放电性能需要进一步提高，以满足实际应用的要求。用Al、Mn、Ti、Fe、Sn、Si、Cr、M。、Cu和Co十种元素取代Ni进行了大量的配方筛选工作。得到了大量的实验数据，并发现LaNi_(3.7)Al_(0.3)合金电极电化学放电容量最高，达290.8mAh／g；LaNi_(3.7)Mo_(0.3)合金电极的高倍率放电性能最好，在以4200mA/g的电流密度下进行放电时，其放电容量仍达到145.8mA/g；而I镍一金属氢化物电池新型负极材料研究镍一金属氢化物电池新型负极材料的研究Al的取代会使合金电极性能对温度不敏感。以我们的实验为基础，进一步进行合金配方的微调，具有可能开发出具有实用价值的贮氢合金的潜力。在Ar保护下用真空电弧炉熔炼合成了四种Lal一xMg：（NICoAI）3．6体系贮氢合金，制成姐卜Ni电池负极，通过恒电流充／放电方法研究了其电化学性能。结果表明：Lal一xMg：（NiCoAI）3．6体系金属氢化物电极较容易活化，室温下具有优异的高倍率放电性能，在以4200mA／g电流放电时，La卜汉gx（NICoAI）36合金电极的放电容量是ABS型合金电极的3倍，达152hah／g，显示出良好的动力学特性。R，入1兮Ni（R：raree田劝，Ca，Y）型合金因能吸引／释放1．8一1．87％质量的HZ而被认为是种很有希望的贮氢合金。但其吸／放氢平台过高，循环寿命短。如何提高Rh厦g剑19循环稳定性是这类合金能否成功商业化的关键。研究发现，Co能够显著提高ABS型合金电极的循环寿命，但其价格太贵。人们发现Al在提高电极寿命方面与C。有类似的作用，但Al元素的添加因其在碱性电解质的作用下在电极表面易生成致密的氧化膜而不利于氢的扩散，进而对高倍率放电性能不利。入物在提高电极表面活性，改善其高倍率放电性方面作用明显。本工作在前面的基础上用Al和MO联合取代Ni，以期待同时改善La一Mg一Ni一Co合金的循环稳定性和高倍率放电性能。详细研究了La07Mg03Ni切一（A105Mo05）x（x：o，0．2，0．4，0．6，0．8）系列贮氢合金的晶体结构和电化学性能。X射线衍射及Rietveld分析发现：所有La07Mg03Ni4D一x（A105Mo05）x合金均为包含PuNi3结构的六方LaZMgNig相、CaCus结构的LaNis主相及L匆Ni7，LaN儿和LaNi杂相的多相结构。合金中La（La，Mg）剑19相及LaNis相的晶格参数及晶胞体积均随合金中Al和Mo含量的增加而增大。用电化学方法测得的RC一T曲线显示：Al和'fo部分取代Ni降低了氢的平台压力。随合金中Al和Mo含量的增加，电极的电化学容量从329．7（x＝0）、徽橇毓孺鑫盆一11瀚加至365．物A吨（＝0．6）后又降低到351．3毗吨（x＝0．8）。当以1200m刀g的电流密度进行放电时，其I｛RD从62．0％沁0）增加到82．1％沁0．8）。线性微极化结果显示：Al和Mo的添加增大了合金表面的交换电流密度，因而也改善了合金电极的高倍率放电性能。另外，Al和M。取代合金中的Ni增大了氢在电极合金中的扩散系数（D），改善了La07Mgo3Ni4。一x（Alo5M。。5）x（X＝o，0．2，0．4，0．6，0．8）合金电极的低温放电性能（LTD）。

稀土固体剂量计材料的合成、发光及剂量光学性质

采用高温固相扩散反应合成了稀土元素激活的碱土硼酸盐MB4O7:RE（M=Sr， Ba；RE＝D又Tb，Tm， Ho）；过渡金属硼酸盐Zn4B6O13：RE（RE＝Dy,Tb，Tm，Ho）； Zn（BO2）2:RE（RE＝Dy,Tb，Tm，Ho）；碱土磷酸盐M3（PO4）2:RE（M=Sr，Ba；RE＝Du, Tb）。通过）。RD和琅光谱对其结构进行了表征。测定了上述化合物的红外、荧光、余辉、漫反射和热释光谱及剂量学性质。研究了高能60Co伽玛射线和p-射线辐照下，稀土离子激活的碱土硼酸盐 MB407：Dy（M=Sr，Ba）；过渡金属硼酸盐Zn4B6O13:Dy；Zn（BO2）2：Dy，Zn毋o承：Tb； 碱土磷酸盐Sr3（PO4）2:Dy的三维热释光谱及MB4O7:Dy（M=Sr，B）的电子顺磁共 振谱（EPR）的性质。发现稀土离子激活剂的浓度在一定的范围内增加时，能够改变陷阱的分布，不同深度陷阱的相对分布发生变化，使峰温向高温方向移动，这可提高剂量器的 热稳定性。发现稀土离子对材料的热释发光亦存在浓度碎灭作用。通过热释发光曲线；结合定量公式，计算了一些硼酸盐化合物的动力学参数。首次应用荧光、三维热释光谱等手段确证了高能60Co伽玛射线和p-射线辐 照没有导致稀土离子D3+和Tb3+的价态变化，即未改变为二价或四价化合物。研究了这类电子俘获材料的存储机理和辐照前后，基质和稀土离子的物理、化学 变化。通过电子顺磁共振谱卿）分析了缺陷的类型，即在高能60Co伽玛射线和p 一射线辐照下，存在空穴和电子两类陷阱中心。热释发光曲线与电子顺磁共振谱 的快衰退部分对应着浅陷阱能级，而慢衰退部分对应着深陷阱能级，陷阱能级是 连续分布的。在个人防护和临床治疗剂量范围内，筛选出7个60Co伽玛射线和中能x一射 线辐照下具有应用前景的高效热释发光材料，为深入研究打下基础。研究了高能p-射线辐照下，两．种潜在的具有应用前景的用于辐射加工剂量范围的p-射线固体剂量计材料。