基于偏振干涉滤光片的宽波带偏振方向旋转器的设计

首次提出了基于偏振干涉滤光片设计方法的宽波带偏振方向旋转器。该旋转器实现了 380 nm～ 780 nm全波长范围内的偏振方向旋转。与普通的只针对某一特定波长的半波片相比 ,该偏振旋转器特性大大超越了普通 1 /2波片 ,并且入射角在± 2 0°范围仍实现偏振方向旋转 90°的要求。将该偏振方向旋转器用作 LCD或 LCOS投影仪中的偏振转换器 ,将大大提高系统的光能利用率以及投影系统的对比度。

宽波带二次谐波产生过程中误差函数的研究

在无泵浦损耗近似(undepleted pump approximation,UPA)下用模拟退火算法设计的非周期光学超晶格(aperiodi optical superlattice,AOS)中实现了1.06~1.08μm波长范围内高转换效率的宽波带二次谐波产生(second harmonic generation,SHG),并且在该结构中研究了已有文献所提出的误差函数对宽波带SHG过程的适用性。该文献提出的误差函数可以用来很好地估计SHG过程中UPA的适用范围,并且指出误差函数只跟SHG的转换效率有关。研究结果表明:宽波带SHG过程中的误差函数曲线与该文献提出的误差函数曲线(本文中称其为标准曲线)是有偏离的,也即该文献提出的误差函数曲线并不适用于宽波带SHG过程。这是因为在实现宽波带SHG的结构中并不能达到好的准相位匹配(quasi phase matching,QPM),该文献提出的误差函数曲线只有在满足完美的QPM的情况下才完全适用。并且还发现在宽波带SHG过程中,误差函数不仅与SHG的转换效率有关,与入射的基频波波长也有关系;对于某些误差函数曲线与标准曲线偏离不大的波长,该文献提出的误差函数曲线可以近似地用来估计UPA的适用范围。

宽波带光纤放大器与CATV

1前言 最近几年,光纤线路的应用无论在通信业或广播业的发展都非常迅速.例如:在通信界的Internet用户的剧增,促使称作最后1英里的宽带化,而ADSL和FTTH的大容量化更加快了光纤干线的容量扩大.因此,光纤放大器不仅成了补偿光信号长距离传送损耗所不可缺少的重要装置.而且随着光节点的构成小区化以及无源光网络(PON)的实用,为对光纤线路中光器件(如光切换器、光分波合波器等)进行损耗补偿,光放大器也是必须的.

基于矢量光场调控的宽波带全晶体型光瞳滤波器

基于复合波片消色差设计方法，结合矢量光场衍射受限的大数值孔径聚焦理论，以600 nm 为中心波长，提出了一种适用于宽波带的全晶体型光瞳滤波器。该滤波器由三片具有同心分区环带的复合延迟波片构成，每分区波片具有各自的方位角及环带参数，且相邻环带光轴垂直。在轴对称偏振矢量光场入射下，通过调节光瞳滤波器的方位角，经聚焦后，在550-650 nm 波长范围内，均可获得轴向焦深的扩展、横向压缩的光针场以及衍射受限的三维光管场。研究结果表明，该光瞳滤波器在100 nm 波段内实现了宽波带矢量光场的调控，这种光瞳滤波器的设计对发展矢量光场的聚焦理论和拓展矢量光在宽波带光场应用方面有重要意义。

Long wavelength infrared metalens fabricated by photolithography

Metasurfaces in the long wave infrared(LWIR)spectrum hold great potential for applications in ther-mal imaging,atmospheric remote sensing,and target identification,among others.In this study,we designed and experimentally demonstrated a 4 mm size,all-silicon metasurface metalens with large depth of focus opera-tional across a broadband range from 9µm to 11.5µm.The experimental results confirm effective focusing and imaging capabilities of the metalens in LWIR region,thus paving the way for practical LWIR applications of met-alens technology.

光纤相位延迟器的设计

本文给出了一种新型的相位延迟器———光纤相位延迟器的设计方案 ,工作原理及理论分析结果。这种光纤相位延迟器具有连续可调和直读特性 ,同时具有宽波带特点。

Ultra-Wideband Electromagnetic Radiation from GaAs Photoconductive Switches

The experiment results of ultrawide band electromagnetic radiation with DC biased GaAs photoconductive semiconductor switch combining double ridge horn antenna triggered by high repeat frequency femto-second laser pulse are reported.The GaAs switches are insulated by solid multi-layer transparent dielectrics and the distance of two electrodes is 3mm.The electrode material of the switch is ohmic contact through alloy technics with definite proportion of Au/Ge/Ni.This switch and double ridge horn antenna are integrated and the receive antenna is connected with the test instrument.From receiving antenna,ultra fast electrical pulse of 200ps rise time and 500ps pulse width is obtained,the repetition rate of the pulse is about 82MHz and the frequency spectrum is in the range of 4.7MHz～14GHz.The radiation characteristic of the ultrafast electrical pulse is analyzed.

A broad-band sub-harmonic mixer for W-band applications

In order to improve the bandwidth of the conventional sub-harmonic mixer, a broad-band, high intermediate frequency（IF） sub-harmonic mixer for W-band applications is proposed. Replacing the open and short stubs that are used in the convertional sub-harmonic mixer with a broad-band band-pass filter and a low-pass filter, respectively, a wide operating frequency band is achieved. Furthermore, without the use of the edge-coupled band-pass filter at radio frequency（RF） port, the proposed structure can be realized by common hybrid microwave integrated circuit technology at W- band. The measured results show that the proposed subharmonic mixer can operate from 80 to 107.5 GHz for RF frequency and support up to 18 GHz for the IF bandwidth. Also, the measured results show that the single-sideband conversion loss is less than 13. 7 dB over the available RF frequency band, while the minimum conversion loss is about 9 dB at an RF of 92. 5 GHz and an 1F of 3 GHz. Thus, a large operating bandwidth performance at W-band can be achieved by the orooosed mixer.

兼容性隐身材料的研究进展

随着军事探测技术的逐渐成熟,各种隐身材料都面临着巨大的挑战,尤其是单一隐身材料,所以兼容复合隐身材料就成了研究重点。本文从材料的角度上介绍了雷达、红外、激光及兼容隐身原理,揭示了兼容隐身的方法,对现有雷达红外、激光红外、激光雷达和雷达红外激光兼容隐身材料的研究现状与原理做了简述,并对未来兼容隐身材料的发展方向做了总结与展望,并指出质轻、料薄、智能、宽波带、强吸收是未来隐身材料发展的趋势。

Analysis and Design of Broadband Stacked Microstrip Patch Antennas

A broadband microstrip patch antenna was analyzed and designed.Full wave analysis method(FWAM) was employed to show that a stacked microstrip dual patch antenna(SMDPA) might have a much wider bandwidth than that of the ordinanry uni patch one.By means of discrete complex image theory(DCIT),the Sommerfeld integrals (SI) involved were accurately calculated at a speed several hundred times faster than numerical integration method(NIM).The feeding structure of the SMDPA was then improved and the bandwidth was extended to about 22% or more for voltage standing wave ratio (VSWR)s≤2 Finally,a matching network was constructed to obtain a bandwidth of about 25% for s≤1.5.

Compact ultra-wideband monopole antenna with dual-band notched function

A kind of compact ultra wideband （UWB） monopole antenna with dual-band notched function is presented.The proposed antenna,using ＂C＂ and ＂L＂ apertures embedded in the annular ring patch and ground patch,gets two bandnotched characteristics in WiMAX3.5 GHz and WLAN 5.5 GHz.The size of antenna is 24 mm × 36 mm × 1.6 mm.The simulation results show that waveband range of the antenna is 2.7-10.6 GHz for S11 ＜-10 dB and the band-notched wavebands are 3.2-3.8 GHz and 5.1-6 GHz.So it has miniaturization,ultra-band and band-notched characteristics.Meanwhile,the radition pattern,directivety and gain are perfect,which meets the practical need.

A 12～18GHz Wide Band VCO Based on Quasi-MMIC

Using an in-house MMIC and an off-chip,high-quality varactor, a novel wide band VCO covered Ku band is introduced. In contrast to HMIC technology, this method reduces the complexity of microchip assembly. More importantly,it overcomes the constraint that the standard commercial GaAs pHEMT MMIC process is usually not compatible with highquality varactors for VCO,and it significantly improves the phase noise and frequency tuning linearity performances compared to either MMIC or HMIC implementation. It is a novel and high-quality method to develop microwave and millimeter wave VCO.

Dynamic compensation and its application of shock wave pressure sensor

In order to correct the test error caused by the dynamic characteristics of pressure sensor and avoid the influence of the error of sensor＇s dynamic model on compensation results,a dynamic compensation method of the pressure sensor is presented,which is based on quantum-behaved particle swarm optimization（QPSO）algorithm and the mean square error（MSE）.By using this method,the inverse model of the sensor is built and optimized and then the coefficients of the optimal compensator are got.This method is verified by the dynamic calibration with shock tube and the dynamic characteristics of the sensor before and after compensation are analyzed in time domain and frequency domain.The results show that the working bandwidth of the sensor is extended effectively.This method can reduce dynamic measuring error and improve test accuracy in actual measurement experiments.

S-band gain flattened distributed fiber Raman amplifier with chirped fiber bragg grating filter

S-band gain flattened distributed fiber Raman amplifier with a bandwidth from 1 488 nm to 1 541 nm （53 nm in width） ,an averaged gain of 10 dB and a gain ripple of ±0.6 dB is obtained successfully, in which a single-wavelength high power fiber Raman laser with wavelength of 1 427.2 nm is used as the pump and the chirped fiber Bragg grating is used as the gain flattening filter. Besides,filter wavelength division multiplexer（FWDM） is used as the multi-signal multiplexer and 1 427 nm/1 505 nm coarse wavelength division multiplexer（OWDM） is used as the pump-signal coupler. The gain media are G652 fiber of 50 km in length and dispersion compensation fiber（DOF） of 5 km in length. Moreover, the location arrangements of different type of fibers and the effect caused by gain flattening filter as well as their solutions are discussed in detail. It is very significant to extend the range of optical fiber communication band and increase the capacity of fiber communication especially for ultra-long haul and ultra-high capacity communication system.

Thermo-optically tunable arrayed-waveguide-grating made of polymer/Si

A 33×33 thermo-optically tunable arrayed-waveguide-grating (AWG) has been fabricated by using the poly (2,3,4,5,6-pentafluorostyrene-co-glycidylmethacrylate) (PFS-co-GMA).The technological process of the fabrication of the device is described,and the measured results are presented.The measured spacing of the wavelength channel is about 0.81 nm,the 3-dB bandwidth is about 0.35 nm,the crosstalk is about -20 dB,and the insertion loss is between 10.4 dB for the centre port and 11.9 dB for the edge port.The measured thermo-optical tunable shift is about -0.12 nm/K.The measured center wavelength is 1 545.21-1 551.81 nm in the temperature range from 10℃ to 65℃,and the tuning range is 6.6 nm.

Joint Optimal Sensing Threshold and Subcarrier Power Allocation in Wideband Cognitive Radio for Minimising Interference to Primary User

Cognitive Radio （CR） can use the fre- quency band allocated to a Primary User （PU） on the premise that it will prevent significant of avoiding causing great interference to the PU. In this paper, we consider a wideband CR system where the Secondary User （SU） mini- raises its interference to the PU by jointly al- locating the optimal sensing threshold and sub- carrier power. A multi-parameter optimization problem is formulated to obtain the joint opt- imal allocation by alternating direction opti- mization, which minimises the total interfer- ence to the PU over all of the subcarriers sub- ject to the constraints on the throughput, Bit Error Rate （BER） and maximal total power of the SU, the subcarrier rate and interference power of the PU, and the false alarm and mis- detection probabilities of each subcarrier. The simulation results show that the proposed joint allocation algorithm can achieve the desired mitigation on the interference to the PU at the different subcarrier gains.

Ultra-wide-band NRD-guide Antenna

A new ultra-wide-band(UWB) horn antenna based on the nonradiative dielectric waveguide (NRD-guide) was proposed to solve the problem of UWB antennas, TEM horns for example, generally suffer from large side leakage. The rule of the theoretical selection of its parameters, if NRD-guide is used as the UWB antennas, is studied firstly, then the radiation characteristics for an open-ended NRD-guide are calculated by FDTD (finite-difference time-domain) method.

A NOVEL WIDE-BAND CIRCULAR PATCH ANTENNA

In order to overcome the narrow-bandwidth of the patch antenna, one kind of configuration which can widen the bandwidth significantly is discussed in this letter. Analyzed by the equivalent-circuits method and simulated by HFSS, a rule derived from simulated results that can aid to design the microstrip antennas is found. Finally, the structure parameters are optimized out, Which reaches 44.67% impedance bandwidth. Furthermore, this kind of configuration can also be applied to the multi-laver patch antenna.

Single-Frequency Matching Pursuits Based Time-of-Flight Measurement in Viscoacoustic Medium

Broadband ultrasound signals will produce distortion in viscoacoustic medium, which may influence the accuracy of time-of-flight (TOF) measurement. Under the condition of single-frequency acoustic source, the wave propagation process in viscoacoustic medium was analyzed and an approximate solution of the wave propagation was given. Instances of broadband ultrasound were analyzed and simulated based on the single-frequency results. A single-frequency matching pursuits (SFMP) algorithm was then introduced to solve the waveform distortion problem. Time-frequency decomposition was applied to extracting the single-frequency compositions from broadband ultrasound signals, and then these compositions were sent to the matching pursuits (MP) algorithm for calculating the TOF parameters. Compared with the broadband signals, the shapes of extracted single-frequency signals change more slightly as distance and attenuation coefficient increase. The residuals of SFMP were far less than those of MP algorithm. Experimental results show that the SFMP algorithm is able to eliminate waveform distortion of broadband ultrasound in viscoacoustic medium, which helps improve the accuracy of TOF measurement.

A novel and simple coplanar waveguide-fed planar monopole antenna for ultra-wideband applications

In this paper, a novel and simple CPW-fed planar monopole antenna is presented for UWB application. The antenna is fabricated on inexpensive FR4 substrate and fed by 50Ω CPW on the same layer, Measured data show that the antenna provides an impedance bandwidth of about 8GHz for the return loss less than 10dB. It is also observed that the radiation pattems are nearly omni-directional over the entire frequency range. Details of the proposed antenna are presented, and simulated results are presented and discussed.