Ka频段抗干扰卫星通信系统地球站射频单元研究

主要探讨Ka频段抗干扰卫星通信系统地球站射频单元的几项关键性技术，首先，简介Ka频段抗干扰卫星通信系统的特点及国内外Ka频段射频技术研究现状和发展方向，进而讨论一种Ka频段抗干扰卫星通信地球站射频单元的主要研究内容和主要电性能指标，最后给出其几项关键技术的解决方法。     

A radio-frequency moving-boundary detector

A new type of moving-boundary detector is described in which boundaries are detected at platinum ring electrodes situated on the outside of a moving-boundary tube. These rings are part of a bridge circuit operating at radio frequencies. Impedance changes in the region of the rings are converted by a phase-sensitive detector to a voltage output which, when operating in the differential mode, takes the form of a sharp peak as a boundary passes through the rings. Boundary displacements of less then 20 m can be detected, and a precision of better than 0.02% is obtained in the measurement of boundary velocities in typical transference measurements. The fact that only three electrical leads are required in the detecting circuit gives this detector a decided advantage for high-pressure work. Equally important is the elimination of electrode polarization problems associated with other types of electrical detectors.Taken, in part, from a Ph.D. thesis, Carnegie-Mellon University, 1971.     

On the Use of Global Kinetics Models for the Investigation of Energy Deposition and Chemistry in RF Argon–Oxygen Plasmas Working in the Torr Regime

A global plasma model is used to investigate the chemistry and energy deposition in 13.56 MHz radio-frequency capacitively coupled oxygen–argon discharges under conditions usually used for the deposition of tin oxide films. These models are based on the solution of a stationary electron Boltzmann equation coupled to species balance equations including the vibrational kinetics equations of O₂. The results obtained showed that vibrational non equilibrium of O₂-molecule is not significant. The dissociation degree of O₂ was found to be around a few percents and the discharge was often moderately electronegative even for small O₂ contents in the feed gas. The ionization and energy dissipation mechanisms are mainly governed by the collisional processes involving O₂ for an oxygen feed gas composition greater than 20%. Results also showed that the predicted densities of the charged species and the electronegative character of the discharge are strongly linked to the assumption made on the homogeneity of the power deposition. On the contrary, the predicted density of O-atom is not sensitive to this assumption.     

Investigation of a resorcinol–formaldehyde resin by 13C-NMR spectroscopy and intrinsic viscosity measurement

Various molecular weight fractions and oligomers isolated from a novolac type resorcinol–formaldehyde (RF) wood adhesive resin were studied by ¹³C-NMR, gel permeation chromatography (GPC), and intrinsic viscosity measurements. The ¹³C-NMR results indicate that methylene groups occur mostly between C₄–C′₄ and C₂–C′₄ carbons and in minor amounts between C₂–C′₂ carbons of resorcinol rings. By suppressing the nuclear Overhauser effect (nOe) and using a long delay time for ¹³C-NMR measurements, reasonable methylene/aromatic carbon ratios were obtained from the aromatic C₁ carbon patterns that have resulted from different numbers of methylene groups bonded on the aromatic ring. This analysis results indicate that the RF resin has an appreciable amount of branch structures and compare favorably with the gel permeation chromatography and intrinsic viscosity measurement results. © 1993 John Wiley & Sons, Inc.     

Photocatalytic properties of TiO2/ZnO thin film

ABSTRACT

TiO₂, ZnO and ZnO/TiO₂ thin films have been prepared by radio frequency magnetron sputtering method under different temperatures. Their photo catalytic activities have been investigated. The structural of the thin films were characterized by X-ray diffraction and Raman spectroscopy. The photo catalytic activities of TiO₂ and ZnO/TiO₂ samples were evaluated by the photo decomposition of methylene blue. We note that the structural proprieties of the thin films showed a perfect crystallization along the (002) for ZnO, Rutile (110) for TiO₂ and Anatase (101) for TiO₂. The experimental results show that the bilayer ZnO/TiO₂ were the most efficient photo catalysts compared to the layer of TiO₂. This increased catalytic effect can attributed to the interface between the ZnO layer and the TiO₂ one, which modify significantly the chemical potential of the bilayer.     

Radio interference challenges in a multiprotocol compact RF hardware platform for home and building automation applications

In the field of smart home and smart building, there is a wide range of products using various proprietary and open standards for their interconnection. However, the coexistence of those standards imposes serious constraints because of the inherent nature of the radio frequency propagation. A way to investigate this issue is to study the interferences in a compact hardware platform/box in which several radio transceivers work side by side, potentially causing interference and radio link degradation due to antennas coupling. To achieve this analysis and predict the radio issues, a simulation tool was developed, and several experimental tests were conducted indoors and outdoors to validate the simulation model. The compact platform investigated consists of multiprofile KNX‐RF modules for home automation and smart grid control, and a radio alarm module for security needs. Simulations were conducted using MATLAB/Simulink, which are based on a calculation of bit error rate according to the signal to noise ratio in order to deduce the radio coverage range in different interference scenarios. The simulation tool developed was optimized to match the behavior of a specific transceiver commonly used for KNX‐RF devices. Yet the tool can be adapted to simulate other kinds of transceivers. Furthermore, the methodology applied to evaluate the cross‐technology interference can be extended to other technologies like Wi‐Fi, ZigBee, and EnOcean.     

基于ATE的射频电路的非线性性能分析

非线性是影响射频电路一个非常重要的因素,随着无线通信技术的发展,对非线性性能的测试显得越来越重要。ATE可同时提供数字、模拟和射频测试资源,能够满足各种复杂射频电路的测试。本文以一款IQ调制器射频电路芯片为例,介绍了一种利用ATE测试1dB增益压缩点和输出三阶截点OIP3的方法。     

Investigation on a source of dominant donor in vanadium-doped ZnO films grown by reactive RF magnetron sputtering

The influences of O₂ gas addition in argon plasma on reactive RF magnetron sputtering deposition of vanadium-doped ZnO (VZO) films were examined. ZnO or VZO films with vanadium concentration of 2 at% were deposited on a quartz substrate. Vanadium doping caused oxygen deficiency in ZnO and formed a large number of zinc interstitials (Zn_i), oxygen vacancies (V_O), and zinc vacancies (V_Zn). Carrier density of VZO decreased from 9×10²⁰ to 9×10¹⁸ cm⁻³ between O₂ partial pressure ratio (α_O2) of 0.6% and 1.0% in spite of the increase in valence number of vanadium. This result suggests that Zn_i is the dominant donor in VZO since Zn_i is a shallow-level defect. Average optical transmittance (T_v) at wavelength between 450 and 800 nm of VZO was 61% while that of ZnO was 82% without oxygen addition. Although the optical transmittance of VZO was largely deteriorated by optical absorption of V_O, T_v of VZO improved by oxygen addition and reached 85% at α_O2 of 1.0% via suppression of V_O formation.     

双频段接收机中的BiFET低噪声放大器

设计了一种采用BiFET结构的低噪声放大器（LNA）,这种结构通过BiCMOS工艺使低噪声放大电路集合了双极型晶体管的低噪声特性和CMOS晶体管的高线性度。应用优化的BiFET Cascode共源共栅结构能够明显地提高低噪声放大器的性能,并且能应用于两个不同频率。本文设计的低噪声放大器在低偏置电流（1．7mA）和低功耗（5．7mW）的情况下能取得1．69dB的噪声系数、15．96dB的电压增益、一8．5dBm的IIP3和-67dB的反向隔离。设计的BiFET低噪声放大器是采用了AMS0．8μm的BiCMOS混合信号工艺,经过优化可以用于工业、室内的远程无线控制系统包括无线门禁系统。