A New High-Gain Microstrip Yagi Array Antenna With a High Front-to-Back (F/B) Ratio for WLAN and Millimeter-Wave Applications

A new printed microstrip Yagi array antenna is proposed that can achieve a high gain and low backside radiation for various applications up to the millimeter-wave frequency range. The high front-to-back (F/B) ratio (up to 15 dB) is attributed to the constructive interference that takes place between the individual printed Yagi arrays in the design. Through the spacing of the elements, the directivity (between 9-11.5 dBi) and the F/B ratio can be altered to suit the application of interest. The operational principles of this design are discussed to give insight on the radiation mechanism of the antenna. An initial design at around 32.5 GHz is presented to show the performance capabilities of this configuration. An impedance bandwidth of 8.3% can be achieved around this frequency. Then, a parametric analysis is conducted to estimate the significance of the design parameters that affect the antenna's performance. Finally, measured return loss and radiation pattern performance at 5.2 GHz is displayed to validate the principles and simulated results of the design. The measured impedance bandwidth of 10% is achieved. The F/B ratio is 15 dB which is larger than values previously published by 5-10 dB. Additionally, a gain of 10.7 dBi is observed. To the author's knowledge, this is the first microstrip Yagi array antenna presented that has a high gain and a high F/B ratio designed using simple fabrication techniques     

Tapered backfire helical antenna with loaded termination

In order to improve the radiation characteristics of a backfire bifilar helical antenna, a means of terminating the arm ends with a resistor is numerically and experimentally investigated. Owing to the reduction of reflected current, the present backfire helix realises an excellent front-to-back ratio and axial ratio, while maintaining inherent absolute gain.     

EBG高阻表面结构的矩形波导宽边缝隙天线

本文提出了波导宽边缝隙天线提高方向图前后辐射比的一种新的实现途径.文中采用在波导宽边上附加EBG (electromagnetic band-gap)高阻表面结构作为高阻接地面的新方法来提高波导缝隙天线方向图的前后辐射比,并对设计的EBG波导缝隙天线单元和阵列的辐射特性进行了仿真分析和实际测量,仿真和测量结果说明该方法对提高矩形波导宽边缝隙天线方向图的前后辐射比是十分有效的.     

Beam-Switching Antenna Based on Plane Dipole Structure

A novel method for designing a beam-switching antenna with the plane dipole is presented. The antenna is composed of double dipoles placed at the center of an active square structure that is divided in four equal sectors by metallic sheets. Metallic patches at the outside of the structure are used to enhance the radiation performance of the antenna. In each step, the diodes in one sector are on, whereas other diodes are off. The sector with off-state diodes defines the direction of the radiation pattern. An antenna model is designed on the substrate of FR4. The proposed antenna operates from 4.8 GHz to 5.5 GHz with gain of 6.3 dBi and F/B (front to back ratio) of 13.2 dBi when the operating frequency is 5.2 GHz. The antenna radiation pattern can be swept in the entire azimuth plane in four steps with a 3 dB beamwidth of 90. The results reveal that the antenna could be used in the base station of the wireless communication systems.     

Numerical analysis of 4-arm Archimedean spiral antenna

The radiation fields of a 4-arm Archimedean spiral antenna excited with three types of balanced mode, M1(1, j, ?1, ?j), M2(1, ?1, 1, ?1) and M3(1, ?j, ?1, j), are evaluated on the basis of the current distributions which are determined numerically. An axial beam and conical beams are presented with experimental results. It is demonstrated that an axial ratio of less than 3 dB can be obtained over a wide angle range of about ± 60°, when the spiral is excited with modes 1 and 2. It is also found that the axial ratio for mode 3 is liable to be deteriorated by the reflected current, particularly around the spiral axis.     

菲涅耳透镜下多结电池表面局部高辐射功率对短路电流的影响

为探索以菲涅耳透镜为聚光器的聚光光伏模组中,多结电池中心局部高辐射功率对短路电流的影响,测量菲涅耳透镜的高亮度光斑直径,并据此分别测试室内不同局部光照面积下和户外不同尺寸透镜下的GaInP/GaInAs/Ge三结电池的短路电流,利用电路网络模型分析实验结果。结果表明,短路电流与局部聚光的面积无关;小尺寸菲涅耳透镜聚焦下,沿光轴电流与辐射功率同步变化;透镜尺寸增大到一定程度,电池中心局部承受过高辐射功率,电流受峰值隧穿电流限制,宏观体现为焦平面处短路电流下降。电池放置在焦平面两侧,均可缓解局部高辐射功率,短路电流最高提升 8.0%。     

Radiation characteristics of prime focus paraboloids with square aperture

Radiation characteristics of a paraboloid with a square aperture are described in this paper. A systematic analysis of the principal plane radiation patterns of the dish employing the uniform geometrical theory of diffraction (UGTD) [3], [4] reveals that for the square paraboloid the backlobes are weak because there is no caustic at the rear boresight as in the case of circular apertures. Based on the method enunciated in [7] the front-to-back (F/B) ratio for different square paraboloids are also tabulated.     

ALPSS: a millimetre-wave aperture-coupled patch antenna on asubstrate lens

The feasibility of millimetre-wave (MM-wave) aperture-coupled patch antennas, printed at the back surface of substrate-lenses is demonstrated and the corresponding radiation characteristics are investigated. A specific realisation of such an air-lens-patch-slot-strip (ALPSS) antenna on a low-permittivity ϵ _r=4.0 extended hemispherical lens substrate is theoretically and experimentally characterised at 70 GHz. It is demonstrated that the ALPSS antenna exhibits clean, axially symmetric patterns of low cross-polarisation (26 dB), a directivity of 30.4 dB and the 3 dB pattern full-beamwidth remains within 6°-5° between 60-80 GHz. In addition, a very-high front-to-back (F/B) ratio, of the order of 50 dB is measured at 70 GHz, despite the absence of a backing ground-plane. The ALPSS antenna is well suited for low-cost broadband point-to-point communications and collision avoidance applications     

Studies of the Focal Region of a Spherical Reflector: Polarization Effects

The polarization of the reflection of a uniform plane wave incident on a spherical reflector is analyzed using the current distribution method for scattered fields. The current distribution on the reflector is derived. For reflectors subtending about60degor less, the radiation scattered in the direction of the circle of least confusion has essentially the same polarization as that reflected specularly from the tangent plane. The effective current, the component of surface current density radiating toward the focal region, is derived in several representations. Assuminghat{i}incident polarization, contour plots are provided forhat{i},hat{j}, andhat{k}components in spherical coordinates. Next, general formulas are derived for thehat{i},hat{j},hat{k}components of the reflected fields, in terms of the direction cosines of the normal to the reflecting surface. These are displayed in terms of projections, and apply directly to the spherical reflector.     

微波活化制备双电层电容器用活性炭的研究

以炭化椰壳为原料,微波活化制备出高比电容量双电层电容器用活性炭。考察了微波辐射时间、起电弧时间,以及KOH与炭化椰壳配比对活性炭比电容量的影响。结果表明,在微波辐射时间为7min,起电弧时间为5min,KOH与炭化料质量比约为3∶1时,比电容量达266.71F/g。以该活性炭作电极的双电层电容器具有良好的充放电性能和循环稳定性能。     

BF_2~+,F~+ +B~+和Ar~++B~+注入硅快速退火剩余损伤及对浅P~+N结的影响(英文)

The residual damage is analysed by transmission electron microscopy (TEM) for BF2+, F+ + B+ and Ar+ + B+ implanted silicon after rapid thermal annealing(RTA). And the reverse leakage current of the implanted diodes is measured using a FJ-356 electrometer. The results show that 1 ) The residual damage due to BF2+ implantation is less than that of F+ + B + and Ar++ B+ implantation. 2) The reverse leakage current of BF2+ implanted diodes is less than that of F+ + B+ and Ar++ B + implanted diodes. 3) The reverse leakage current of F++B+ and Ar++ B+ implanted diodes increases with the increase of F+ and Ar+ energies, respectively. Therefore the physical behaviour of the interaction between molecular ion and silicon is different from that of the interaction between individual atom ion and silicon.     

Ultrafast all-optical modulation of infrared radiation viametal-semiconductor waveguide structures

We present a novel optical-optical semiconductor switching technique for application to infrared laser beam modulation and ultrashort infrared laser pulse switching. This method relies on the ultrafast optical excitation, with femtosecond above-bandgap laser radiation, of an air-filled metal-clad semiconductor waveguide. Guided electromagnetic wave analysis combined with time-varying dielectric properties of the semiconductor layer are used to investigate the ultrafast switching speed of the structure. The device is capable of modulation at various infrared wavelengths. In particular, we investigate intensity modulation of the quasi-TE₁₀ mode for 10.6-μm laser radiation. At an electron-hole photoinjection density of ~1.8×10¹⁸ cm^-3, an extinction ratio of 83 dB is demonstrated. This ratio is significantly higher than that exhibited by current optical-optical semiconductor switches. Potential applications to all-optical Mach-Zehnder metal-clad semiconductor modulators and self-limiting switches are also discussed     

微波辐照石油焦制备双电层电容器用活性炭

以石油焦为原料,KOH为活化剂,采用微波辐照加热法,制备了石油焦基双电层电容器用活性炭。研究了石油焦与KOH活化剂的比例、微波功率以及微波辐照时间对活性炭孔径分布和比电容量的影响。结果表明:在KOH活化剂与石油焦的质量比为3.5∶1,微波功率800W和辐照时间7min时,制备的活性炭比表面积为2031.96m2/g,比电容量达286.79F/g,以该活性炭作电极的双电层电容器有良好的循环稳定性和充放电性能。     

An integral equation and its application to spiral antennas onsemi-infinite dielectric materials

This paper presents an integral equation that can handle wire antennas on a semi-infinite dielectric material. The integral equation is reduced to a set of linear equations by the method of moments. For efficiency, the impedance matrix element Z_m,n is divided into two parts on the basis of weighted Green's function extractions. The far-zone radiation field, which is formulated using the stationary phase method, is also described. After the validity of the presented numerical techniques is checked using a bow-tie antenna, a spiral antenna is analyzed. The current distribution, radiation pattern, axial ratio, power gain, and input impedance are discussed. It is found that the radiation field inside a dielectric material is circularly polarized. As the relative permittivity of the dielectric material increases, the angle coverage over which the axial ratio is less than 3 dB becomes narrower     

抗辐射加固集成稳压电源的最新设计和研究

本文探讨了降低线性集成稳压电源的功耗和提高它们的抗辐射能力的技术途径。介绍了一种新型稳压器电路,以低功耗电流放大器为其基础,改电压控制型为电流控制型,使电路在满载情况下,输入输出最小压差降到1V左右;并具有良好的启动保护功能,纹波抑制比可达70db以上;当输出电压V_o=12V时,其效率的典型值为90％。 为了尽量提高这种电路的抗辐射能力,在设计电路时就注意到了降低有源元件与无源元件的数量比,使电路设计尽量简化。并充分注意到光电流补偿单元的设置和增益裕量的限度。采用了介质隔离技术和晶体管归一化的标准设计,在工艺参数的设计中采用特殊加固晶体管的设计方法。使该电路的抗中子能力比初步加固的器件提高一倍左右,抗γ瞬时辐照能力提高二倍以上。     

Microwave noise characterisation of poly-emitter bipolar junction transistors

The microwave noise characteristics of poly-emitter bipolar junction transistors have been evaluated in a 0.8 mu m silicon BiCMOS process, at frequencies between 1 and 5.6 GHz and for collector currents between 0.5 and 15 mA. Using a small-signal model for the poly-emitter bipolar junction transistors, very good agreement has been obtained between measurements and calculations of both noise figure (F/sub MIN/) against frequency, and F/sub MIN/ against collector current. It is found that F/sub MIN/ was 2.3 dB at 1 GHz and 8.3 dB at 5.6 GHz for a collector current of 5 mA.<>     

逆F类放大器漏极电压波形研究

为了更清晰地了解逆F类功率放大器通过规整漏极电压和电流波形实现高效率的本质,对其漏极电压波形进行了理论分析和仿真验证。结果表明,在仅考虑二、三次谐波,且当谐波比例k=1/4时,v(θ)波形最平坦,最近似于半正弦波。利用电磁软件仿真设计并制作了一款k=0.271的逆F类功率放大器,经测试在输出功率为36.33 dBm时,功率附加效率达到了71%。     

A new "mixed-mode" reliability degradation mechanism in advanced Si and SiGe bipolar transistors

A new mixed-mode base current degradation mechanism is identified in bipolar transistors for the first time, which, at room temperature, induces a large I/sub B/ leakage current only after simultaneous application of both high J/sub C/ and high V/sub CB/. This new mechanism differs fundamentally from well-known I/sub B/ degradation mechanisms such as the reverse EB voltage stress, high forward current stress and damage due to ionizing radiation. Extensive measurements and two-dimensional (2-D) simulations have been used to help understand the device physics associated with this new degradation mechanism.     

用蒙特卡罗方法和MATLAB计算冷屏内壁表面辐射光线落入探测器芯片的比例

介绍了用蒙特卡罗方法和MATLAB计算圆形冷屏内壁表面辐射落入探测器芯片比例的一种解决方案。该 方案基于三维空间中的方向数概念,首先利用MATLAB命令生成冷屏内壁表面上的随机点,再赋予该点一组随机方向数,获得 一条随机直线方程,以判断它是直接投向芯片平面还是经反射后投向芯片平面。对于反射的情况,根据镜面反射的性质及解析几 何公式,生成该直线在冷屏内壁上的反射光线,并判断它们是否落在探测器芯片区域。经统计后,可算出冷屏各部分落入芯片表面 的辐射光线在冷屏内壁表面发射出来的总光线数中所占的比例。该方法具有编程简单和方便实用等特点。     

Reducing IGBT losses in ZCS series resonant converters

The fundamental operational parameter that controls the losses in series resonant power converters was found to be the reflected DC voltage transfer ratio. Losses which are a function of the average current (such as conduction losses of insulated gate bipolar transistors and diodes) are independent of the switching frequency. Losses which are associated with the RMS current are a function of both the reflected DC voltage ratio and the switching frequency ratio. Universal and normalized graphs, derived in this paper, can be conveniently used to assess the expected RMS and average current conduction losses under any given operational conditions. The residual switching losses in zero-current-switching series resonant power converters operating in continuous current mode can be reduced by simple current snubbers placed in the commutation circuits. The experimental results of this paper confirm the theoretical predictions and demonstrate that the turn-on snubbers can reduce switching losses by about 1.5% at a switching frequency of 65 kHz