Design of a high-frequency planar power transformer in multilayertechnology

A high-frequency power transformer using multilayer printed circuit board (ML-PCB) technology is presented for applications in switched-mode power supplies operating at frequencies up to several megahertz. The mechanical configuration of laboratory prototypes is discussed, as well as the electrical, parasitic, and thermal behavior. The focus is on the leakage inductance, since the analysis of other aspects is relatively simple. Test results show that the transformer has high efficiency, low leakage inductance, good thermal behavior, and good line insulation properties. The topology enables the designer to make a trade-off between leakage inductance and interwinding capacitance. Due to the well-defined geometry, parasitic interwinding capacitance and leakage inductance are reproducible and can be computed relatively easily     

Modal analysis of a planar waveguide with gain and losses

In this study, we analyze the waveguiding properties of a planar waveguide amplifier in which losses and gain can be present simultaneously. It is found that the subsequent modes comprise both loss and gain modes. Also, the dependence of the gain on the state of polarization turns out to be significant for realistic dielectric structures. For strong losses or gain, the standard transfer matrix approach may become numerically unstable, therefore, a scattering matrices formalism is employed. A semiconductor-like gain profile enables us to study the gain as a function of ω for realistic laser amplifier structures     

Analysis of high-frequency parameters of superconducting planar structures

Planar microwave devices that make it possible to determine parameters of fabricated layers are developed and produced. The parameters are needed for correct numerical simulation based on the Mattis–Bardeen theory and may differ from the tabulated parameters of materials.     

Performance of a planar filter using a 0/spl deg/ feed structure

The advantage of using a 0/spl deg/ feed structure in filter design is that two extra transmission zeros are created in the stopband while the passband response remains unchanged. This feed structure is analyzed by using transmission matrices. A new lumped-circuit model for a coupled resonator filter is then proposed to take into account the effects of this feed structure. Finally, the feed structure is applied to the design of a cross-coupled filter. All the theoretical analysis and design procedures have been successfully verified by experiment results.     

高频变压器绕组涡流损耗等效因子分析

针对平面磁性元件,利用Dowell模型和有限元方法对绕组涡流损耗等效因子Δ进行研究。分别对单股、多股圆导线和其等截面积正方形导线进行仿真分析,得到当圆导线直径为2~6个集肤深度时,涡流损耗减小显著;当圆导线直径大于6个集肤深度时,涡流损耗趋于平稳。圆导线直径为2~6个集肤深度时,等效因子的值较为理想;圆导线直径大于6个集肤深度时,其值偏低。为了提高设计的精确性应尽量选择直径少于6个集肤深度的圆导线。     

Reduction of dielectric losses in substrate integrated waveguide

The impact of different loss mechanisms on the attenuation of the substrate integrated waveguide (SIW) is investigated. Using a multilayer PCB technology, an air-cut region is introduced in the SIW structure to reduce the attenuation caused by dielectric losses. Numerical results obtained using a mode-matching technique verify that the attenuation constant of the SIW can be reduced significantly if the width of the air-cut is chosen properly     

High performance submicrometer pentacene-based organic thin-film transistor using planar bottom-contact structure

This paper presents a pentacene-based organic thin-film transistor (OTFT) with a submicrometer channel length of 0.5 μm that uses a planar bottom-contact (pBC) structure to achieve high electrical performance. The performance of the submicrometer OTFT is dominantly influenced by the growth continuity of pentacene near the edge of the source/drain (S/D). The pBC structure with a bilayer dielectric can provide a continuous plane for improving the growth continuity and quality of pentacene near the edge of the S/D. This results in high electrical performance for the submicrometer OTFT with pBC structure, such as a mobility of 0.14 cm²/V s and an on/off current ratio of 1.9 × 10⁵.     

Study of the DC biasing effect on insertion losses in high-frequency interconnections

The paper deals with an experimental investigation of the behavior of high-frequency Si/SiO₂/Al based interconnects when an extra DC bias voltage is applied, by means of which the conductor line changes the surface properties of the semiconductor substrate. By superposing a DC bias to the high-speed signal applied to the line, the insertion losses caused by the semiconductor substrate show a significant decrease over the observed frequency range. In order to study this effect a number of test samples containing several microstrip asymmetric transmission lines were prepared and measured. The obtained results suggest a way of controlling the performance and energy propagation of interconnects on semiconductor substrates. The observed effect can be successfully applied in high-speed blocks with tunable parameters.     

PIN-bipolar optical receiver using a high-frequency high-beta transistor

A PIN-photodiode bipolar-transistor optical receiver for the 1.1?1.6 ?m wavelength range capable of operation up to 320 Mbit/s is described. Low input capacitance and high DC transistor current gain are shown to be important in achieving good sensitivity, and these factors are emphasised in the design of the receiver and the devices used. Error-rate measurements show a receiver sensitivity of ?34.5 dBm at 280 Mbit/s.     

对流热损失对双曲两步热传导的影响

在激光热源加热时间远小于达到热平衡所需时间的条件下,研究了对流热损失对金属薄膜热行为的影响。指出当热源强度非常高且薄膜厚度满足L<20hc,e/G时,电子气的对流热损失对薄膜热行为的影响是不能忽略的;当L<20hc,l(θl-1)/Gθe时,固体晶格的对流热损失对薄膜行为有显著的影响。从双曲两步热传导模型出发,运用Laplace变换给出在考虑对流热损失的情况下,金属薄膜的电子气和固体晶格温度在Laplace变换域内的解析表达式,同时给出各种工作条件和材料参数对薄膜热损失的影响。     

Pumping planar waveguide amplifiers using a coupled waveguidesystem

A novel scheme is presented that can be used to efficiently pump optical waveguide amplifiers. It is based on the coupling between two adjacent waveguides, where pump light is gradually coupled from a nonabsorbing pump waveguide into the amplifier waveguide. The coupling between the waveguides in such a configuration is calculated using an improved coupled mode theory (CMT). The proposed distributed coupling scheme can enhance the optical gain in systems that exhibit a reduced pumping efficiency at high pump power. A numerical example is given for a sensitized neodymium-doped polymer waveguide amplifier, in which the optical gain increases from 0.005 dB to 1.6 dB by changing from conventional butt-coupling to distributed coupling     

Reduction of absorption losses in ZrF4-based IR fibres

By incorporating oxidising gases into the melt atmosphere during the fabrication of ZrF4-based IR fibres, it has been possible to reduce absorption due to Fe2+ to extremely low levels. This was accompanied by an increase in loss from Cu2+, but this absorption tails off rapidly beyond 1.5 ?m. Overall absorption losses have been reduced to the order of 2 dB/km at 2.5 ?m, estimated to have arisen from other 3d transition metals and some rare earths.     

An algorithm for the determination of eddy-current losses and temperatures in a conductor subjected to high-frequency magnetic-flux variations

An algorithm is presented for the determination of temperature at any time and at any interior point of a plane metallic body, given the surface heat flux. Alternatively, given the temperature at a specific point and time in a plane semi-infinite metallic body, with little or no assumed surface heat loss, the surface heat flux can be determined. The technique can be used to estimate open-circuit tooth ripple eddy-current losses in a smooth section of the laminated poles of synchronous machines. It is readily implemented on a programmable calculator.     

Investigation of a planar chiral waveguide structure by a modified ATR method

Chiral properties of planar waveguide structures with a core layer formed by a poly(methyl methacrylate) (PMMA) host matrix doped with chiral santonin were investigated by means of a modified attenuated total reflection (ATR) method. Distinct modification of the observed ATR spectra was revealed for right and left circularly polarised incident beams. From comparison of the experimental spectra with theoretical curves, the following specific rotation was obtained: [α]=11,200 deg cm² g⁻¹ (santonin/ PMMA mass ratio 2:1). The origin of the observed optical activity and its influence on the waveguide dispersion characteristics are briefly discussed. © 1998 John Wiley & Sons, Ltd.     

High-voltage planar structure using SiO2-SIPOS-SiO2film

The BVCB0leakage current hFEwere studied for high-voltage planar transistors which had three kinds of passivation films; SiO2-semi-insulating polycrystalline silicon (SIPOS)-SiO2; SIPOS-SiO2; and SiO2-phosphosilicate glass (PSG)-SiO2. The SiO2-SIPOS-SiO2type had a lower leakage current (surface generation current) and higher hFEthan the conventional SIPOS-SiO2type. The SiO2-SIPOS-SiO2type also had the highest BVCB0due to the field-plate effect.     

A zero voltage transition boost converter employing a soft switching auxiliary circuit with reduced conduction losses

This paper presents a zero-voltage-transition (ZVT) boost converter using a soft switching auxiliary circuit for power factor correction (PFC) applications. The improvement over existing topologies lies in the positioning of the auxiliary circuit capacitors and the subsequent reduction in the resonant current and therefore the conduction losses as compared to other similar topologies. The proposed converter operates in two modes - Mode 1 and Mode 2. It is shown in the paper that the converter should be designed using the constraints obtained in Mode 1 to achieve low-loss switching. The converter is analyzed and characteristic curves presented which are then used in a detailed design example. Experimental results from a 250 W, 127 V input laboratory prototype switching at 100 kHz verify the design process and highlight the advantages of the proposed topology. The proposed converter is suitable for single-phase, two stage power factor correction circuits with universal input voltage range and power levels up to 3 kW.     

An integral equation method for the evaluation of conductor anddielectric losses in high-frequency interconnects

An integral equation method is developed to solve for the complex propagation constant in multilayer planar structures with an arbitrary number of strip conductors on different levels. Both dielectric losses in the substrate layers and conductor losses in the strips and ground plane are considered. The Green's function included in the integral equation is derived by using a generalized impedance boundary formulation. The microstrip ohmic losses are evaluated by using an equivalent frequency-dependent impedance surface which is derived by solving for the fields inside the conductors. This impedance surface replaces the conducting strips and takes into account the thickness and skin effect of the strips at high frequencies. The effects of various parameters such as frequency, thickness of the lines, and substrate surface roughness on the complex propagation constant are investigated. Results are presented for single strips, coupled lines, and two-level interconnects. Good agreement with data available in the literature is shown     

PECVD grown multiple core planar waveguides with extremely lowinterface reflections and losses

A novel and generic method for fabricating silica-on-silicon planar lightwave circuits with cores composed of two or more different types of glasses is described. The basic process technologies used are silane/germane/nitrous-oxide based plasma enhanced chemical vapor deposition and fluorine based reactive ion etching. Very high-quality interfaces between the different core glasses are obtained with interface losses as low as 0.022±0.012 dB and reflection levels below -80 dB. This technique adds flexibility and ease to the design of complex silica planar waveguide components, allowing, e.g., independent optimization of amplifying and passive sections in lossless devices based on erbium-doped planar waveguides     

A novel zero-voltage and zero-current switching PWM DC-DC converterwith reduced conduction losses

A novel zero-voltage and zero-current switching PWM DC-DC converter with low conduction losses is presented in this paper. A new interleaved two-switch forward soft-switching converter topology is developed to minimize circulating current with no additional auxiliary circuits. This converter has many advantages such as less components, better efficiency, high power density and cost efficiency for high power applications. The principle of operation is illustrated together with steady-state analysis. Moreover, the effectiveness of the proposed converter topology is verified by implementing a 500 W-100 kHz breadboard using IGBTs     

一种新型平面结构的双陷波超宽带天线设计

为了避免现存的一些窄带通信系统对超宽带天线的干扰,提出了一种具有双陷波特性的超宽带天线结构。由于采用了渐变式阶梯阻抗匹配结构作为超宽带基础天线的馈电,使天线具有了宽阻抗匹配能力。通过在基础天线背面附加双偏T寄生单元和在辐射贴片上开窗的联合方法,实现了超宽带天线的双陷波特性。天线电流分布结果可以完全反映出在陷波频率下两种方法的谐振抑制作用,而且实验结果表明该结构的天线对 WLAN(5.15～5.825 GHz) 和WiMAX(3.4～3.69 GHz)频段的信号起到了有效的抑制作用,同时在工作频段内表现出较好的全向辐射特性。