射频CMOS平面螺旋电感2-π等效电路模型参数的提取

从有理分式拟合方法出发,提出了用于射频CMOS平面螺旋电感2-π等效电路模型参数提取的新方法.通过比较提参后等效电路给出的S参数和实验测量的S参数,证明该方法的精度很高.此外,提参的策略非常直接,因此容易在CAD里面编程实现.提参得到的等效电路模型对于射频电路设计者来说也是非常有用的.     

用磁控溅射和退火方法制备AlSb多晶薄膜

采用磁控溅射法在玻璃衬底上制备Al/Sb预制多层薄膜,然后将Al/Sb预制多层薄膜在退火炉中退火得到AlSb多晶薄膜.用X射线衍射(XRD)法测薄膜结构;用扫描电镜(SEM)测薄膜Al/Sb成分比,结果表明AlSb多晶薄膜具有单一的晶相、均匀的结构,以及粒径大约20nm的晶粒.根据电导率(lnσ)与温度(T)的关系得到电导激活能为0.21和0.321eV,为制备出适用于太阳电池的AlSb多晶薄膜奠定了一定的技术基础.     

FPGA-based test bed for measurement of AM/AM and AM/PM distortion and modeling memory effects in RF PAs

Using a field-programmable gate array (FPGA) development board, a digital signal processor (DSP) builder, and the phase-to-amplitude conversion principle, a low-cost system for measuring the amplitude-to-amplitude (AM/AM) and amplitude-to-phase (AM/PM) distortion curves of radio frequency (RF) power amplifiers (PAs) is presented. The state of the art based on the measurements and preliminary studies of AM/AM and AM/PM distortion curves is discussed. A full digital control of the test bed simulated/emulated in Matlab/Simulink is introduced to recalculate the known AM/AM and AM/PM measurements stored as look-up table (LUT). Finally, the low-cost system comprises the memory polynomial model (MPM) that involves the nonlinearity order and memory effects of real PAs.     

Distributed NGD active circuit for RF-microwave communication

This paper is aimed to the investigation on innovative distributed negative group delay (DNGD) circuits for RF communication. Thanks to the analogy between the lumped and distributed circuits, NGD circuit topologies were identified. By using the S-parameter theory, analysis and synthesis methods of these topologies are proposed. The DNGD circuits developed are mainly comprised of a transistor combined with a series resistance ended by a stub. Then, synthesis relations enabling to determine the NGD circuit parameters from the desired NGD and gain values are established. As application, an active phase shifter (PS) operating independently with the frequency based on the cascade of PGD and NGD devices was synthesized. First, an NGD PS with transmission phase of (135 ± 5)° around 2.56 GHz over the bandwidth of about 1.02 GHz was obtained. Then, a two-stage DNGD PS exhibiting 90° with ±10° flatness from 4.1 GHz to 6.8 GHz was designed. The DNGD circuit presented can be used in various telecommunication areas notably for correcting RF/numerical signal delays in the RF-microwave analogue-digital devices.     

Observation of defect clustering in Gd-doped calcium fluoride

Abstract

Solid solutions Ca_1-xGd_xF_2+x for 3 × 10^?7≤ x ≤10^?1 have been studied by electron paramagnetic resonance (EPR) and ionic thermal currents (ITC). The EPR experiments show the presence of two single-ion sites a cubic and a tetragonal Gd³⁺ center which co-exist with comparable abundances for intermediate impurity concentrations. The cubic center predominates at very low and high concentrations. Seven different relaxation processes have been identified from the ITC spectra and the variation of their intensity vs. x was measured. The absolute concentrations of the cubic and nn Gd³⁺ dipoles were calculated. The scavenging of interstitial fluorines by the neutral clusters explains both the abundance of cubic sites at high concentration and the variety of orientable clusters detected by ITC.     

Thermalization of the flow of sputtered target atoms during ion-plasma deposition of films

The boundary of the zone in which sputtered atoms are thermalized in the substrate–target drift space during the ion-plasma magnetron deposition of films is determined theoretically and experimentally. A comparison of the thicknesses of films deposited on the front and back sides of substrates situated at different distances from the target makes it possible to divide the flow of atoms sputtered toward substrates into direct and diffusion flows and to determine the dimensions of the spatial zone in which sputtered atoms are thermalized. The experimental data are in quantitative agreement with the results of a statistical simulation of the thermalization process of atomic particles during the ion-plasma deposition. This simulation enables optimization of the technology of defect-free growth of films with uniform thickness on substrates with complex 3D configuration.     

Erosion of Thin Foils by Sputtering in Hollow Cathodes

A thin copper foil placed diagonally in a cylindrical copper hollow cathode undergoes fast erosion caused by cathode sputtering. Changes in the foil shape are related to current distribution along the hollow cathode axis. The experimental results aid in understanding the increase in spectral lines intensities emitted from conical bottom hollow cathode lamps.     

Summary of ISO/TC 201 Standard: ISO 22415—Surface chemical analysis—Secondary ion mass spectrometry—Method for determining yield volume in argon cluster sputter depth profiling of organic materials

The International Standard ISO 22415 provides methods to measure sputtering yield volumes of organic test materials using argon cluster ions. The test materials should consist of thin films of known thicknesses between 50 and 1000 nm. The format of the test materials, the measurement of sputtering ion dose, sputtered depth, and reporting requirements for sputtering yield volumes are described.     

Frequency doubling of Nd:YAG- and GaAs-lasers by KNbO3: Ta crystals

Abstract

For KNb_1-xTa_xO₃ crystals the influence of the Ta-concentration on the phase-matching properties for optical second harmonic generation (SHG) was measured. For non-critical phase matched SHG of the Nd:YAG-laser (1064nm) the coefficient d₃₁ of the tensor of the nonlinear susceptibility was applied, while for the GaAs-laser (905 nm) the coefficient d₃₂ was used. For both laser wavelengths the phase-matching temperature decreases with increasing Ta-concentration. Non-critical phase-matching at room temperature can be reached with the GaAs-laser for a Ta-concentration of ≈9%. The corresponding value for the Nd:YAG-laser is ≈14%.