Millimeter wave monolithic high electron mobility (HEM) varactor diode-grid frequency tripler arrays

High Electron Mobility (HEM) varactor structures have been studied for millimeter-wave monolithic diode-grid frequency tripler array applications. The improved HEM varactor diode structures provide a highly nonlinear C-V characteristic (i.e., a steep slope of the C-V curve and a large capacitance ratio) which produces high harmonic generation efficiency and reduce the power requirement for efficiently pumping each device. The effects of the light illumination on the C-V characteristics of the Barrier-Intrinsic-N⁺ (BIN) varactor diode have also been studied and the results will be discussed in this paper. In the development of a monolithic diode-grid frequency multiplier array, the low-loss quasioptical configuration is used for the construction of the multiplier circuit. The study of the effects of the light illumination on the C-V characteristics of varactor diode is important in understanding the potential applications of the quasi-optical varactor diode-grid frequency multiplier array circuit.     

Design criteria of the near-millimeter wave quasi-optical monolithic diode-grid frequency multiplier array

The high-frequency performance along with the optimum designs and operating conditions of near-millimeter wave quasi-optical monolithic diode-grid frequency multiplier arrays have been studied and will be presented in this paper. The limitations of the development of nearmillimeter wave quasi-optical monolithic diode-grid frequency multiplier arrays will be discussed in detail. The optimum operating conditions and performance of different device structures are presented along with the associated device physics. The optimum designs, operating conditions and performance of the monolithic diode-grid frequency multiplier array will also be discussed based upon the temperature distribution study on the diode-grid.     

Design and performance of millimeter-wave end-coupled bandpass filters

The design and performance of millimeter-wave microstrip/suspended-stripline end-coupled bandpass filters are presented. Filters in Ka-band (26.5 to 40 GHz) and W-band (75 to 110 GHz) using suspended-stripline and microstrip have been designed. Good agreement between the experimental results and those predicted theoretically was observed. Measured passband insertion losses of less than 1 and 0.5 dB have been achieved in W- and Ka-band, respectively. An extremely wideband waveguide-to-microstrip transition with an insertion loss of 0.25 dB over the full W-band is also presented.     

Generation and transmission of the double-sideband optical millimeter-wave with signal carried only by optical carrier

In this paper, we have proposed a new scheme to generate double-sideband (DSB) optical millimeter-wave (mm-wave) with signal carried only by optical carrier, and its transmission performance is investigated. The theoretical and numerical results show that the DSB optical mm-wave signal generated by our scheme suffers only from the fading effect, the time shift of the sidebands has little influence on its transmission performance. The signal demodulated from the harmonic photocurrent shows a clear and open eye diagram and has good performance even if the transmission distance is very close to but not just at the fading nodes. The theoretical results are in good agreement with our numerical simulation.     

Fabrication of two-dimensional colloidal arrays

We report the effective fabrication of two-dimensional (2D) arrays of submicron colloidal particles. These colloidal arrays are produced in thin layers of monodisperse colloid suspensions on flat surfaces of solids such as clean glass or cleaved mica. The process of colloid assembling includes two steps, nucleation and growth, similar to those found in crystallization in solution but each of the steps in detail progresses with different mechanisms. The nucleation process is initiated by a special kind of capillary force acting parallel to the surface. The growth is guided by a laminar flow of water to the crystals, which is driven by water evaporation from 2D arrays. What is distinguishable in the 2D assembling is its active nature governed by the forces and flows, making a contrast to the diffusive mechanism in ordinary crystallization. With this two-step mechanism, a domain of hexagonally packed colloidal array can grow with time. A large and uniform film of particle monolayer is, thus, formed in a short period, from several seconds up to several minutes depending on the conditions controlled.     

外腔锁相二极管激光列阵的超模

利用耦合理论推导了通过外腔反馈实现锁相运行的激光二极管列阵所满足的本征值方程。在忽略非相邻单元间耦合的串联运行方式下,解析求解了包括端面反射的列阵方程的本征值。求出了各阶超模的近场分布,并得到了考虑单个发光单元影响时的远场分布,具体为：当列阵运行于基超模时,近场各个单元间的光场同相,在远场中心位置出现光强主极大;而在其它高阶模式,近场各个单元间光场不同相,远场光强主极大出现在中心位置两侧;远场总体受到单个发光单元近场分布函数的调制。     

Study of a millimeter-wave squint indirect holographic algorithm suitable for imaging with large field-of-view

In this paper a millimeter-wave （MMW） squint indirect holographic method is presented, which is suitable for imaging with a large field-of-view. The proposed system employs the squint operation mode to remove the background and twin- image interferences, which achieves a similar effect to off-axis holography but leaves out the large-aperture quasi-optical component. The translational scanning manner enables a large field of view and ensures the image uniformity, which is difficult to realize in off-axis holography. In addition, a corresponding imaging algorithm for the presented scheme is developed to reconstruct the image from the recorded hologram. Some imaging results on typical objects, obtained with electromagnetic simulation, demonstrate good performance of the imaging scheme and validate the effectiveness of the image reconstruction algorithm.     

LD阵列侧面泵浦棒状激光介质内的光场研究

建立了LD侧面泵浦激光介质内的光场分布数值模型。通过光线追迹方法,简化了介质对泵浦光折射的计算方式。利用Matlab软件数值模拟了泵浦光在介质内的归一化分布。提出获得高质量、高能量的激光输出参数的选取原则。当LD的束腰半径为1μm、LD的数量为40个、介质的半径为1.5mm、发光面到介质的泵浦距离为0.5mm、介质吸收系数在2cm-1～6cm-1之间时,泵浦光在激光介质内的增益分布较好。     

Dynamic thermal modeling and parameter identification for monolithic laser diode module

We improve the thermal equivalent-circuit model of the laser diode module (LDM) to evaluate its thermal dynamic property and calculate the junction temperature of the laser diode with a high accuracy. The thermal parameters and the transient junction temperature of LDM are modeled and obtained according to the temperature of the thermistor integrated in the module. Our improved thermal model is verified indirectly by monitoring the emission wavelength of the laser diode against gas absorption lines, and several thermal parameters are obtained with the temperature uncertainty of 0.01 K in the thermal dynamic process.     

A full-duplex radio-over-fiber system based on a novel double-sideband modulation and frequency quadrupling

We propose a novel radio-over-fiber system based on double-sideband (DSB) modulation and frequency quadrupling to reduce the system cost both at central office (CO) and base station (BS). In this system, by properly biasing the intensity modulator, the repetitive frequency of the optical millimeter-wave (mm-wave) is four times frequency of the local oscillator (LO) signal. Additionally, due to the single-sideband of the mm-wave carrying base data signal, our theoretical simulation shows that the generated mm-wave can be immunized the fading effect and the walk-off of signals.     

77 GHz车载毫米波中远距雷达天线阵列设计

为了在雷达中实现对中距和长距的探测,首先研究并实现了针对中长距雷达探测需求的天线及其组阵形式,然后通过雷达方程得出天线阵列所需的增益与组阵方式,设计了高增益窄波束和低增益宽波束形式的毫米波雷达天线阵列,最后的仿真和测试结果表明,该中长距雷达天线阵列能够满足77 GHz车载毫米波雷达对中距大角度和长距小角度的视野范围探测需求。     

自聚焦透镜列阵的设计原理与制造

讨论了自聚焦透镜及其列阵成像的规律.根据所需列阵的共轭距离,分辨率等确定单根自聚焦透镜的几何尺寸和光学参数,设计出复印机用的自聚焦透镜列阵.最后,对列阵的制造作了初步介绍.     

高频大功率磁绝缘线振荡器的理论设计

初步考虑了高频率与高功率的磁绝缘线振荡器的设计问题。用在阴极端头增加发射电流的办法,在C波段理论得到了1.16GW的微波输出功率。利用增加高次谐波的办法在X波段理论获得了270MW的功率输出。     

High-repetitive frequency millimeter-wave signal generation using multi-cascaded external modulators based on carrier suppression technique

We have numerically and experimentally investigated how to generate high-repetitive frequency millimeter (mm)-wave using multi-cascaded intensity modulators based on optical carrier suppression (OCS) scheme. We have found the rule how to generate the high-repetitive frequency mm-wave by adjusting the repetitive frequency of the radio-frequency (RF) signals and the phase relation between the RF signals on the intensity modulators. Based on this rule, we have experimentally demonstrated to generate over 80 GHz optical mm-wave.     

高频大功率磁绝缘线振荡器的理论设计

 初步考虑了高频率与高功率的磁绝缘线振荡器的设计问题。用在阴极端头增加发射电流的办法,在C波段理论得到了1.16GW的微波输出功率。利用增加高次谐波的办法在X波段理论获得了270MW的功率输出。     

High frequency doubling efficiency THz GaAs Schottky barrier diode based on inverted trapezoidal epitaxial cross-section structure

A high-performance terahertz Schottky barrier diode (SBD) with an inverted trapezoidal epitaxial cross-sectional structure featuring high varactor characteristics and reverse breakdown characteristics is reported in this paper. Inductively coupled plasma dry etching and dissolution wet etching are used to define the profile of the epitaxial layer, by which the voltage-dependent variation trend of the thickness of the metal-semiconductor contact depletion layer is modified. The simulation of the inverted trapezoidal epitaxial cross-section SBD is also conducted to explain the physical mechanism of the electric field and space charge region area. Compared with the normal structure, the grading coefficient M increases from 0.47 to 0.52, and the capacitance modulation ratio (C_max/C_min) increases from 6.70 to 7.61. The inverted trapezoidal epitaxial cross-section structure is a promising approach to improve the variable-capacity ratio by eliminating the accumulation of charge at the Schottky electrode edge. A 190 GHz frequency doubler based on the inverted trapezoidal epitaxial cross-section SBD also shows a doubling efficiency of 35% compared to that 30% of a normal SBD.     

THz波段亚波长半导体球形阵列光学特性的数值模拟

利用T-matrix方法对太赫兹波段亚波长半导体球形阵列进行了数值模拟并在数值模拟结果的基础上讨论了其光学特性。在太赫兹波段可以通过掺杂等手段调节半导体的表面等离子体特性。以半导体InSb为例并采用Drude模型,对单个亚波长球及两个或多个亚波长球组成的阵列进行了数值模拟,主要以归一化消光截面为参数,讨论了不同阵元半径、不同球形单元间距、不同单元数目及入射波不同极化方向对阵列特性的影响。     

基于宽波束磁电偶极子天线的宽角扫描线性相控阵列

设计并加工了两款基于宽波束磁电偶极子天线单元的宽角扫描线性阵列.首先,通过加载磁偶极子的方法拓展了天线单元的3-dB波束宽度.然后,基于该宽波束天线单元设计了两款具有良好宽角扫描特性的一维阵列天线.实测结果表明,天线单元的E面方向图3-dB波束宽度在9GHz—12 GHz均大于107°,H面方向图3-dB波束宽度在7GHz—12 GHz均大于178°.E面阵列中心单元的有源驻波比在9GHz—13 GHz小于2,相对阻抗带宽为36.36%.H面阵列中心单元的有源驻波比在9.6GHz—12.6 GHz小于2.5,相对阻抗带宽为27.03%.E面阵列在9GHz—12 GHz可实现±70°的有效宽角扫描.H面阵列在9GHz—GHz可实现±90°的有效宽角扫描.与传统的扫描阵列相比,设计的阵列可实现有效宽带宽角扫描,在X波段相控阵雷达方面具有广阔的应用前景.     

Design and fabrication of multi-channel photodetector array monolithic with arrayed waveguide grating

We have provided optical simulations of the evanescently coupled waveguide photodiodes integrated with a 13-channels AWGs. The photodiode could exhibit high internal efficiency by appropriate choice of layers geometry and refractive index. Aseamless joint structure has been designed and fabricated for integrating the output waveguides of AWGs with the evanescently coupled waveguide photodiode array. The highest simulation quantum efficiency could achieve 92% when the matching layer thickness of the PD is 120 nm and the insertion length is 2 μm. The fabricated PD with 320-nm-thick matching layer and 2-μm-length insertion matching layer present a responsivity of 0.87 A/W.     

Improvement of sound absorption characteristics under low frequency for micro-perforated panel absorbers using super-aligned carbon nanotube arrays

Super-aligned carbon nanotube (SACNT) arrays are grown on the surface of micro perforated panel (MPP) in the hope of improving the acoustic performance of MPP absorbers by virtue of their unique properties. Scanning electron microscopy reveals that SACNT arrays did not block the perforations of MPPs or changed the perforation diameter due to their “super-aligned” nature, although MPPs are thickened. The absorption effect of SACNT arrays which are of the same and different lengths with different incident side on MPP absorbers are investigated, and standing wave tube method is used to determine the normal sound absorption coefficient. Results show that both of the lengths of SACNT arrays and the incident side have effects on the sound absorption performance of MPP absorbers. And generally SACNT arrays help to improve the sound absorption capacity of MPP absorbers in low-frequency regions only when the SACNT arrays surface is the incident side. SACNT arrays decrease absorption performance of MPP absorbers when the MPP surface is used as the incident side. Moreover, SACNT arrays are found to increase the acoustic ability of MPP absorbers with the same structure parameters monotonically at lengths up to 600 μm in the condition that the SACNT arrays surface is used as the incident side.