光收发模块分立元件实现方法探讨

回顾了光收发模块的发展,分析了模块的结构、工作原理和各个主要部分的功能,有针对性地对集成设计中的元件进行了取舍,讨论以分立元件实现光收发模块的具体方案、元件选取原则,给出了模块的155M分立元件光收发一体化设计实例,分析了工作频率、分布参数对分立元件设计的影响,指出了设计中可能遇到的问题,探讨了更高速分立元件设计实现的可行性

Design and Field Analysis of PMMA Rib Optical Waveguides

利用有效折射率法(E IM)理论设计了有机聚合物脊形光波导结构,并分析光波导中传输的模式场,确定出光波导结构的适宜尺寸范围。光波导结构中分别选用PMMA(聚甲基丙烯酸甲酯)与PDM S(聚二甲基硅氧烷)作为波导层与包层的材料,用光漂白法来实现脊形波导结构。首先利用E IM法分析脊形波导区的宽度与高度之间的关系对归一化色散曲线的影响,以及波导层与包层的折射率匹配的影响,然后又通过分析波导区传输的基模场来讨论传输的损耗问题。研究发现波导结构的脊宽与脊高之比w/d越大,其有效折射率neff越大,而此结构尺寸又需约束在一定范围内,否则将造成很大的传输损耗。The structure of the polymer rib optical waveguide is designed by using effective index method(EIM),and the mode field distribution in these waveguides is analyzed to determine the suitable structural size range.For this rib waveguide realized by photo-induced bleaching,two kinds of polymer materials,PMMA and PDMS,are chosen as the core layer and the cladding layer respectively.Firstly with EIM,the influence of the relationship between the rib width w and height d on the normalized dispersion curve and the effect of refractive index matching are studied.Then,the base mode field in the waveguide is analyzed to discuss the transmission loss.It has been found that the larger the size ratio w/d of the PMMA rib waveguide is,the greater its effective index n_(eff)becomes.But this structure size should be limited in certain range,otherwise very large transmission loss would result.高校骨干教师项目资金;; 福建省青年科技人才创新项目资金(2001J024

Fault Characteristic Study Based on FLUX 2D for Large Synchronous Generators With Stator Winding Inter-turn Short Circuits Under Rated Operating Conditions

该文采用单一绕组分析和有限元分析相结合的方法,研究大型同步发电机在额定运行方式下定子绕组匝间短路故障特性。该方法同样适用于确定故障条件下的电流和转矩。对于内部故障情况的电磁瞬态仿真必须考虑到一些特殊措施,如单一绕组和电网之间正确的连接对于模拟内部故障是相当关键的。以往的结果表明,在内部磁场非对称的情况下,基于等效电路的经典算法是不适用的。该文通过对汽轮发电机匝间短路故障进行系统的研究,表明:其短路电流、相电流、转矩和径向力与短路的位置及匝数紧密相关。在一些短路情况下,发电机将产生很大的局部电流,该局部电流对同步发电机的影响甚至超过外部故障。此外,很大的径向力作用在转子上可能对整个转轴产生极大的危害。This paper investigates the stator winding short circuit characteristics in synchronous generators under rated operating conditions by combing the single-winding analytical method and the finite element method(FEM),which is still the effective method to determine currents and torques under specific fault conditions.Some special measures have to be considered in case of the electromagnetic transient process under the condition of inner faults,e.g.,the correct interconnection between sub-strands and the grid is of the particular importance for inner fault simulations.The previous results show that the traditional calculation method based on the equivalent networks fails in case of the inner asymmetry magnetic field.Based on the systematic investigation of a turbo generator with inter-turn short circuits,the results of this paper show the short circuit currents,phase currents,torques and the radial forces have strong correlations with the location and the turn number of faults.In some cases of inter-turn short circuits,the fault currents exceed that of the outer faults.Furthermore,strong radial forces acting on the magnet wheel might lead to the damages of the total shaft train

纳米颗粒对极化聚合物的非线性驰豫特性的影响研究

以K-M模型和光散射理论为基础,建立了纳米颗粒掺杂改性的PMMA聚合物材料的紫外散射模型,推导出了考虑入射波偏振的理论计算公式,解决了在非线性光学性能的抗老化与聚合物波导的加工之间所存在的矛盾。利用MATLAB编制了基于Mie算法的程序,分析了收敛条件,并对体系纳米粒子的粒径与后向散射系数、吸收系数的定量关系进行理论计算。仿真结果表明,在波长约200-400nm范围内,最佳抗老化效果的粒径集中在20-50nm之间。利用偏振对于粒子散射影响较大的特点,提出用带偏振片的紫外灯来进行波导光刻加工的设想,确定了最佳掺杂颗粒半径35-40nm之间的理想范围。最后,将仿真结果与实验结果进行了对比分析,证实了散射模型和仿真过程的可靠性。“福建省科技计划重点项目(2007H0036)”提供资

Design of Ultra-wideband Printed Rectangular Monopole Antenna

针对超宽带通信应用,研究影响印制单极天线阻抗带宽的主要因素,设计基于微带馈电的小型化印制矩形单极天线。按照等效性原理,采用黄金分割比设计矩形振子体;通过接地面上端引入渐变梯形或凹形结构,同时调整馈入端接地面间隙,可实现印制矩形单极天线的超宽带特性。对具有渐变梯形或凹形接地面结构的微带馈电矩形印制单极天线结构进行优化,仿真结果表明,前者的阻抗带宽为2.96~17.94gHz,后者的阻抗带宽为2.9~13.3gHz,而两者的辐射方向基本保持不变。实测结果与仿真结果基本一致,达到了超宽带通信应用的要求。To achieve ultra-wideband(UWB)radio applications,the microstrip-fed printed rectangular monopole antenna is analyzed and devised.Using golden section ratio the rectangular monopole is of layout based on equivalent principle.To maximize the impedance bandwidth,it is necessary introducing the taper or concave ground plane and feed gap of microstrip line.The simulated results of the optimized-size antennas show that the impedance bandwidth defined by return loss less than-10dB is from 2.96GHz to 17.94GHz with a ratio of about 6.06∶1 for taper ground antenna and from 2.9GHz to 13.3GHz with a ratio of about 4.59∶1 for concave ground antenna.At the same time a nearly omnidirectional radiation pattern is exhibited.These results are confirmed by the experimental test and these compact size antennas are suitable for various wideband applications.福建省科技计划重点资助项目(2007H0036

Trapezoid Printed Monopole Band-Notched UWB Antenna

设计了带三角形槽梯形辐射元和阶梯接地面的30 MMx30 MM印制单极超宽带天线原型。实验结果表明,原型天线驻波比小于2的阻抗带宽为2.8 gHz~12.81 gHz,频带内天线具有全向辐射特性,增益变化平坦,相位中心稳定。通过对原型天线振子体的缝隙加载,实现了具有带阻特性的陷波超宽带天线,其驻波比大于3的陷波频带为4.8 gHz~6.0 gHz,陷波频带内最高增益抑制为9 db,而其他频段性能与原型天线基本一致。A trapezoid printed monopole Ultra Wide Band(UWB) antenna of the triangular cut and step ground plane is designed as the prototype,which size is 30 mm×30 mm.The experimental results show that its impedance band width is from 2.8 GHz to 12.81 GHz defined by Voltage Standing Wave Ratio(VSWR) less than 2.Over the operating band the prototype antenna has omni-directional radiating pattern,stable antenna gain and fixed phase center.By cutting a slot in the radiator of the prototype,the band-notched antenna is introduced.Its notch band is from 4.8 GHz to 6.0 GHz defined by VSWR≥3,and the largest gain rejection ratio is 9 dB.In the other working bands the band-notched antenna has the similar radiating performance with the prototype.福建省重大科技专项(2010HZ0004-1

Design of Wideband Bi-directional Microstrip Antenna

针对室内走廊或狭长街道小功率基站应用要求,采用微带结构设计了一款具有双向辐射特性的宽带线极化低剖面天线。天线辐射元为平行四边形结构,馈电点在其几何中心,通过在靠近馈点两侧开两个反对称l形槽,实现了宽带双向辐射特性。低剖面原型天线的相对带宽为5.8%,两端射方向增益约为4.3dbI,在工作频带内天线辐射场为有一定倾角的线极化。该天线结构可置于小功率基站内部,有助于减少系统体积。A linearly polarized wideband microstrip patch antenna with the bi-directional radiation pattern is proposed for the low-power indoor or narrow-street base station systems.The proposed antenna,which has a parallelogram radiator,is fed by a coaxial line at its geometric center.In order to achieve the wideband bi-directional radiation characteristics,two anti-symmetric L-shaped slots were etched near the feed point.The simulation and measurement show that the low profile prototype antenna provides a relative bandwidth of about 5.8%,and the endfire direction gain of 4.3dBi.In the working band its linear polarization direction has incline angles with the vertical.This antenna can be placed inside the low-power base stations to help reduce the system size.福建省重大科技专项(2010HZ0004-1

Patch Loaded Based Ultra-wideband Notch Antenna Design

文章设计一种基于贴片加载的开槽超宽带陷波天线,天线采用微带线-槽线馈电,通过加载贴片实现陷波功能。经过仿真与实测,结果显示该天线在3.03gHz~15.88gHz的频带内电压驻波比(VSWr)小于2,其中在5.14gHz~5.93gHz具有陷波特性,增益抑制最大值达到9.3db,仿真结果与实测结构匹配良好。The slotted ultra-wideband notch antenna was designed based on the patch loaded.The antenna with a line-slot line feed,achieves notch by loading patch.Simulation and experimental results show the antenna band VSWR<2 within 3.03 GHz～15.88 GHz,with a notch at 5.14 GHz～5.9 GHz,and the maximum gain suppression of 9.3 dB.Simulation results match well with the experimental results

Development of composite plate for microwave antenna

Conference Name:2011 International Symposium on Advanced Packaging Materials, APM 2011. Conference Address: Xiamen, China. Time:October 25, 2011 - October 28, 2011.A new kind of machinable composite plate was developed for microwave antenna in this paper, in which ceramic powder of CaO-Li2O-Ln 2O3-TiO2 was mixed with PTFE polymer in different proportions. It was showed that the permittivity of the composite plate was enhanced from 4 to 15 with the increasing content of ceramic powder; meanwhile, the quality factor was maintained at 1000GHz. The antenna was obtained with the composite plate which was machined to suitable size and covered with copper electrodes. The antenna's bandwidth was about 60MHz and standing wave ratio was near 1.12. ? 2011 IEEE

Analysis and computation of ESI coefficient of planar waveguide based on field matching

首次采用了场的最小二乘方 (LSE)和最小均方误差 (LMS)判据寻找平板波导的等效阶跃折射率 (ESI)模型 ,并通过它预测了平板波导的传输特性。计算结果表明 ,原始波导与等效波导场分布在具有最大近似性的基础上 ,ESI模型可以在一定范围内有效的预测平板波导的传输特性。归一化频率与第一个高阶模的截止频率之比在小于 0 7的情况下 ,用上述两种判据找到的ESI模型预测传输常数相对误差小于 0 0 1 % ,预测归一化传输常数的相对误差小于 1 0 %。A method to find Effective Step-Index(ESI) model based on field matching criter ia of least-square-error(LSE) and least-mean-square(LMS) error is put forward, and the propagation quality from ESI coefficients is predicted. When the ESI model a n d the original waveguide have the best approximated field distribution, the prop agation quality of planar waveguide efficiently can be predicted based on ESI mo del in specific range. When the ratio between normalized frequency and cut-off fre quency of the first higher model is lower than 0.7, the relative error of predic t ing propagation constant from the ESI model is less than 0.01%, and the relative error of predictiong normalized propagation constant is less than 10%