一种基于LINC发射机系统的信号分离实现方法

在应用LINC系统进行操作时,为了提高LINC系统的效率,巧妙的在信号分离过程中对信息进行处理极其重要。当前普遍采用的的信号分离技术都有其缺陷,对此进行了有效的处理,得到了一种更卓有成效的实现方法。     

一种基于LINC技术的信号分离算法

LINC（Linear Amplifier Using Nonlinear Components）技术是使用非线性的功放来实现信号的线性放大。LINC技术克服了传统线性化技术的效率低,带宽窄的问题,理想情况下能够达到100%的效率。信号分离是LINC的关键技术,信号分离的特性严重影响了LINC合成信号的性能。根据LINC技术信号分离原理,采用CORDIC算法来实现输入信号的幅相分离,将输入的调幅调相的变包络信号分离成两路恒包络调相信号。同时采用了一种优化的信号分离算法,把初步分离的两路数据进行角度比较,根据选择最小夹角原则重新分配两路数据,达到改进信号包络的目的。对信号分离过程进行仿真验证,表明信号的恒包络特点得到了显著改善,最后使用FPGA实现。     

LINC发射机中的矢量信号分解及电路实现

本文利用矢量信号正交分解的原理实现LINC发射机中的信号分解.以Altera公司的QuartusⅡ 7.2作为编译、仿真平台,选用Straxix Ⅱ系列中的EP2S60F6器件进行硬件实现,采用数据归一化处理和查找表技术,使电路设计更加简洁,并且讨论了相位增益不平衡对LINC发射机线性度的影响,说明LINC发射机中需要对支路不平衡进行调节.     

一种非线性元件实现线性放大的改进技术与仿真

提出了一种改进的非线性元件实现线性放大（LINC）理论,将幅度和相位均变化的输入射频信号分离成包络信 号和恒包络角调信号,再将包络信号正交调制到后者的相位中,然后对两路调制后的恒包络信号进行变频放大,最后通 过求和电路得到放大后的上变频输入射频信号。因为恒幅信号可以在放大器的非线性区放大而不失真,从而整体效率高。 本文推导出其电压增益为m KG E ,并对不同频率和幅度进行了仿真,得到的仿真结果表明实现了理论分析的预期的放大 效果。     

一种MIMO雷达非高斯杂波中的信号分离方法

针对传统匹配滤波方法对非高斯相关杂波下MIMO雷达信号分离性能下降的问题,本文基于线性约束最小功率波束形成器原理,给出了一种适用于非高斯相关杂波条件下的MIMO雷达自适应信号分离算法。该方法将需要分离的发射信号以外的信号和相关杂波作为干扰,利用接收信号的分数低阶统计量在线性约束最小功率准则下导出了滤波器权系数,实现了非高斯相关杂波中对信号实时有效的分离。最后采用本文方法在SG-Alpha稳定分布杂波背景下进行了仿真实验,结果表明,本文方法可有效实现非高斯相关杂波中的MIMO雷达信号分离。      

8GHz散射通信中扩频分离多径技术的应用

主要阐述8GHz散射通信系统的设计思路和采用线性调频扩频信号以及分离多径接收的合理性。对线性调频信号的形式和特点进行了分析,给出了分离多径技术的设计和实现方法。并以实际工程为例,给出了实测的通信链路试验波形和试验结果,用以说明扩频、分离多径技术应用于8GHz散射通信中获得的显著效果。实践表明,该系统有很强的实用价值。     

多重直扩信号的捕获方法研究与实现

多重直扩信号的快速捕获是卫星定位与通信系统研制过程中遇到的一个关键技术。它的实现，不仅可以提高系统的多址能力，而且也是系统实现的必要条件。本文阐明了多重信号产生的原因以及可被分离并有效接收的理论依据。提出了一种多重信号快速捕获的方法，给出了硬件实现的方案和部分实验结果。     

基于广义特征分解的盲信号分离算法

针对复杂环境下的线性混叠信号,给出了一种基于广义特征分解的盲信号分离方法。在信号数目未知的情况下,该方法利用广义特征分解即可获得混叠矩阵,无需进行常规的迭代运算即可实现对线性混叠信号的分离。实验证明了该方法的可行性和有效性。     

基于FrFT的欠采样LFM信号分离与参数估计

基于分数阶傅里叶变换，本文提出了一种欠采样条件下的宽带与窄带线性调频信号分离与参数估计方法。该方法先由延迟相乘和牛顿迭代算法估计信号的调频斜率，然后在分数阶傅立叶变换域进行滤波，实现信号分离。最后对欠采样信号解频率模糊，估计信号的初始频率。仿真表明了该方法分离宽带与窄带线性调频信号的可行性与分离后信号参数估计的有效性。     

基于正交编码激励的水下声呐高帧频成像方法

针对水下声速引起的超声成像系统成像帧率不高的问题,提出一种采用伪随机编码线性调频波(平衡Gold-LFM)作为发射信号的高帧频水下声呐成像方法。该方法通过依次发射相互正交的伪随机编码调制线性调频波,结合通道分离技术和波束形成技术,实现不同信号的通道分离与高帧频成像。仿真实验表明所提出的基于平衡Gold-LFM复合信号的成像方法可以实现回波信号的通道分离和提高成像帧率,同时能够降低图像伪影,具有较好的成像信噪比。     

前馈放大器中抵消环路的研究

为了尽可能提高前馈放大器的线性,减少抵消环路抵不匹配及辅助放大器的非线性给系统带来的不良影响。在此通过前馈电路模型讨论分析了经第一抵消环后未完全抵消的基波信号和辅助放大器的非线性对系统造成的影响可以忽略不计的条件。通过该关系式能方便准确的估算出该条件下系统能达到的三阶互调,并通过实验验证。     

Analytical and experimental study of LINC amplifier using unmatched Wilkinson combiners

This work presents an analytical and experimental study of LINC power amplifier where an unmatched Wilkinson combiner is used at the output of two class-B amplifiers. This combiner is called unmatched because of the elimination of the one hundred ohms resistor from its input. This resistor is used to guaranty a good impedance matching between the combiner and the amplifier outputs. An amount of reflection coefficient can be presented at the input of the combiner depending on the signals phase different of the two LINC branches which that may damage the linearity of the amplified signals. Our Analytical study in this paper presents equations for the power efficiency and the signal linearity showing that despite of reflection between the combiner and the amplifiers, very good efficiency and linearity will be obtained. An ADS simulation and experimental work of the LINC system is performed shows an excellent agreement with the analytical study.     

A high-linearity and high-resolution delay line structure with a calibration algorithm in delay-based LINC transmitters

In order to overcome the bottleneck of low linearity and low resolution, an improved delay line structure is proposed with a calibration algorithm to conquer PVT (process, voltage and temperature) variations for an all-digital design. The chip is implemented in 0.13 μ m CMOS technology. Measurement results show that the proposed structure with the calibration algorithm can evidently improve the linearity and resolution of the delay line. The delay resolution is 2 ps and the root mean square jitter of the delay is 4.71 ps, leading to an error vector magnitude enhancement of 1.32 dB.     

一种可重新配置分辨率的全数字可综合的延迟型LINC发射机基带

The linear amplification with nonlinear component transmitter is a promising solution to high efficiency and high linearity amplification for non-constant envelope signals.An all-digital synthesizable baseband for a delay-based LINC transmitter is implemented.This paper proposes a standard-cell based synthesizable methodology which can be applied in the ASIC process efficiently without performance degradation compared to the manual layout.A scheme to overcome the limited resolution of conventional phase detectors is proposed.It employs alternative phase detector structures to provide reconfigurability for higher resolution after fabricating,resulting in an11 ps resolution improvement.Due to the PVT variation,an adaptive calibration scheme focusing on the inherent imbalance between two delay lines is depicted,which reveals an effective EVM enhancement of 5.37 d B.This baseband chip is implemented in 0.13 m CMOS technology,and the transmitter with the baseband has an EVM of –28.96 d B and an ACPR of –29.51 d B,meeting the design requirement.     

A Voltage-Translinear Based CMOS Signal Component Separator Chip for Linear LINC Transmitters

The LINC transmitter is an architecture that provides linear amplification using nonlinear but power efficient amplifiers. One crucial signal processing function of LINC is the signal component separator (SCS) which forms two constant-amplitude phase-modulated signals from the source signal. This paper presents an analog SCS chip implemented in a 0.35 m CMOS process using a novel design based on the so-called voltage-translinear circuit principle. An experimental LINC transmitter was built with the SCS chip, nonlinear amplifiers and a power combiner. Test results showed that all output spurious levels some -55 dBc and -48 dBc could be obtained with a North American Digital Cellular (NADC) signal and an IS-95 signal, respectively. This implies a high degree of linearity.     

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.