移动通信直放站互调干扰的消除方法

移动通信直放站广泛应用于移动通信网络中,直放站在对射频信号进行放大的同时,也会产生互调信号,互调信号如果过大将会对通信网络产生严重干扰,降低通信网络的质量.直放站的互调信号主要是由于直放站射频功率放大器的非线性特性产生的,要消除直放站的互调信号就要改善直放站射频功率放大器的非线性.文中首先阐述了直放站互调信号对移动通信网络的影响,然后分析了直放站射频功率放大器互调信号产生的原因,最后介绍了3种改善射频功率放大器线性的方法:功率回退法、预失真法、前馈法.     

三路Doherty功率放大器的设计与仿真

基于可有效提高功放效率的Doherty理论,对两路非对称Doherty所存在的问题进行剖析,提出了一种嵌入内Doherty的三路Doherty(3-way Doherty)结构,并对该三路Doherty的工作状态和阻抗变换等基本理论作了细致描述与分析,最终结合多谐波双向牵引技术和双匹配技术,成功设计了一款平均输出功率为5W的TD-LTE直放站三路Doherty功率放大器.中心频率2600 MHz的仿真结果表明,平均输出功率处的三阶互调系数IMD3为-36 dBc,增益Gp达10.6 dB,功率附加效率PAE保持在56％左右,较普通AB类功放有近38％的提高,且在整个12dB回退范围内功率附加效率曲线相对平坦,符合现代功放高功率回退和高效率的设计要求,可以与数字预失真技术结合用于实际直放站中.     

射频模拟预失真器的研究与设计

利用小信号BJT放大器的非线性特性设计了一个有源模拟预失真器.通过调整小信号放大器的偏置状态和对失真信号的提取控制,使功放的三阶互调失真得到了明显的改善.双音实测数据表明,该预失真器使一个GSM基站功放在5 dB功率回退点附近的三阶互调失真改善了18 dB左右,与传统的射频预失真器相比,该预失真器对功放三阶互调失真的改善度提高了10 dB左右.     

高效率高线性度功率放大器的设计与实现

基于对传统两路Doherty功放存在的问题分析,文中对其结构进行改进,提出了一种新颖的非对称结构。该非对称结构采用相同的功放管,通过变换漏极与栅极电压分别对主辅功放进行负载牵引和源牵引以达到不同的饱和输出功率,从而实现更高的功率回退。基于该理论,结合互调对消技术和多谐波双向牵引技术设计并实现了应用于工作频段为2.57～2.62GHz的TD-LTE直放站功率放大器。在饱和输出功率回退9dB的平均输出功率处,功率附加效率(PAE)为38%,5MHz和10MHz偏移量的相邻信道功率比(ACPR)分别为-41dBc和-50dBc,实测结果显示Doherty功放的参数性能良好,满足TD-LTE直放站要求的同时验证了设计方案的正确性。     

调整初相提高多频点信号功率利用率的方法

通过分析信号初相与多频率合成信号包络的关系,提出利用初相调整的方法来优 化合成信号包络,从而提高功放的功率利用率。仿真分析结果和实际应用表明,该方法可以 很好地降低合成信号包络的最大电平,使合成信号包络尽可能在放大器的线性范围内,从而 有效抑制了交调和互调成分以及谐波成分,提高了功率利用率。     

基于MATLAB的RF功率放大器互调失真仿真分析

应用Matlab仿真平台对RF功率放大器的互调失真(inter-modulation—IMD)进行了分析。结果表明:在输入信号峰值或峰值功率不变时,可以用输入为两个或三个正弦信号情况下的互调失真指标来估计输入为宽频带、高密度信号情况下的互调失真指标;通过降低输入功放信号的峰值功率可以降低互调失真分量的相对幅度。     

Ka 频段200W 线性固态功放设计

介绍了一种Ka频段200W高线性度固态功放的工程实现。采用混合式功率合成与波导功率合成相结合的技术路线,在Ka频段实现了近百路的高效功率合成。功放共合成了96个功放芯片,连续波输出功率可达250W;针对功率器件线性度不足的现状,采用射频预失真技术优化其线性度,三阶互调指标优于-33dBc,改善幅度最高达15dB;固态功放设计中充分考虑了工程化与产品化性能,结构外形标准、散热性能良好,并配置了完善的控保功能,在可靠性及实用性方面均初步达到工程使用的要求。     

前馈超线性放大器双环误差信号的提取

本文结合超线性功放项目的研制实践,分别论述了前馈超线性功放中信号对消环路和互调对消环路中的误差信号提取问题。其中,在信号对消环路,通过新颖的电路设计将幅度差信息和相位差信息分别提取出来,极大简化了控制算法的设计。所讨论的两种误差信号提取方法均在实践中得到了验证,达到了预期的指标。     

利用预失真技术降低功放的非线性

介绍了一种改善大功率功放非线性的数字化预失真技术。在大功率干扰设备中,功率 放大器的非线性失真对通信对抗的多目标干扰的能力可造成严重影响。为了优化干扰信号的质量,可 采用信号预失真技术,可有效提高干扰信号的谐波抑制和多目标干扰信号的互调抑制能力,改善干扰信 号质量,进而提高通信对抗设备的多目标干扰能力。     

关于CATV系统中交调互调指标的分析

1前言随着CATV行业的逐步发展,我区有线电视网中的频道数越来越多,在系统性能指标中,交扰调制、相互调制等非线性失真将会给基带信号引入固定的干扰。因此,对有线电视工程技术人员而言,对交调、互调两项指标的理解显得尤为重要。2交调、互调的定义及公式交扰交调是指需要的调制信号电平的峰峰值和其它频道转移过来的调制信号电平的峰值比。CM=交扰调制比是表示由于系统非线性而造成各个频道的调制信号相互转移,影响用户正常收看的一项技术指标。载波互调是指载波电平有效值和互调产物电平有效值比。IM=载波互调比是表示由于系统存…     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.     

High-quality single-crystal CdSe nanoribbons and their optical properties

Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method, in which two-step-thermal-evaporation is used to control CdSe sources＇ evaporation. The synthesized CdSe nanoribbons are usually several micrometers in width, 50 nm in thickness, and tens to several hundred micrometers in length. Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method. Room-temperature photolumines-cence indicates that the lasing emission at 710 nm has been observed under optical pumping （266 nm） at power densities of 25-153 kW/cm^2. The full width half maximum （FWHM） of the lasing mode is 0.67 nm     

Propagation of hermite-cosh-gaussian beams passing through ABCD optical system with an annular aperture

By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly.     

Influence of polarization extinction ratio on distributed polarization coupling detection

Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited.     

Call for Papers

正Communications—VLSI Researches and industries of telecommunications have been growing rapidly in the last 20 years and will keep their high growing pace in the next decade.The involved researches and developments cover mobile communications,highway and last-mile broadband communication,domain specific communications,and emerging D2D M2M communications.Radio communication steps into its