An efficiency measurement of microwave two-ports using perturbation methods

For the determination of the efficiency of a reciprocal microwave two-port loaded with a known variable impedance, the measurement of three values of input impedance is required. If the region in which the load impedance can be changed is narrow, the error of the classical method (Ginzton 1957) may be significant. The perturbation method (Morawski 1973) which is described in this report can be used to determine the efficiency of any two-port and the error is comparable or even smaller than the error of the classical method. The perturbation method is particularly useful when the region of the load impedance change is narrow. This method is much simpler than the classical one for the matched network and for some special cases of unmatched networks. The method is convenient for the determination of the efficiency of jigs including PIN diodes, or varactors.     

Measurement and analysis of phase noise generated fromsemiconductor optical amplifiers

The phase noise generated from traveling-wave semiconductor optical amplifiers is measured. It is found that the phase noise is strongly correlated with the intensity noise and has bandwidth of 600 MHz. Phase-noise formulas are derived for semiconductor optical amplifiers to explain such phase-noise characteristics. It is shown that the phase noise is induced by the carrier density fluctuation associated with the intensity noise and the spontaneous carrier recombination. For the coherent heterodyne DPSK system, the phase noise, instead of the intensity noise, is found to be the limiting factor on the number of repeater amplifiers     

Effect of direct current on spuriously generated third harmonics

An investigation is made into the effect of direct current on the third harmonic voltage produced by a very pure sinusoidal current passing through commercially available resistors. It is found that the third harmonic voltage falls in amplitude as the direct current is increased.     

Voltage harmonics generated by voltage-fed inverters using PWMnatural sampling

The harmonics generated by natural sampled pulse width modulation are investigated experimentally and by theoretical models for the outputs obtained with triangular and sawtooth carrier signals. These equations are valid for synchronous and asynchronous operation. It is shown that triangular carriers generate less harmonics than sawtooth carriers, and that in synchronous operation with single-phase modulation, the carrier-to-output frequency ratio may be any integer value     

Error vector magnitude relation to magnitude and phase distortionin 8-PSK systems

Distortion in 8-PSK systems is a consequence of magnitude and phase disturbances. This work investigates the effects of such distortions (either isolated or combined) due to Gaussian bandpass noise, through analytical and simulation studies. Analytical expressions are derived and analytical-based results, relating error vector magnitude to symbol error rate, are contrasted with simulation results     

高精度幅相检测系统的设计

为了提高幅相检测精度、简化电路、扩展频率范围,设计了一种基于AD8302高精度幅度相位检测系统。通过分析AD8302的特点以及工作原理,提出了几种提高相位检测精度的方法,并设计采用AD8302、DDS和单片机组成高精度幅相检测系统,成功地解决了AD8302相位检测过程中存在的二值性、非线性、移相以及校准问题,实现两路模拟输入信号的相位差和幅度差的精确测量。测试结果表明基于AD8302的幅相检测系统具有精度高、抗干扰能力强等优点。     

激光辐照平面靶产生的二次谐波结构

一、实验布置 用六路钕玻璃激光器中的一路进行实验,激光输出能量为5～10焦耳,脉宽100微微秒,激光进入靶室之前由检偏器检偏,偏振度达98％以上,并使用旋光片产生在入射平面内的P偏振及垂直于入射平面内S偏振两种偏振光,以0°、10°、20°、30°、45°等不同入射角对平面铝靶及2微米、3.5微米铝箔进行辐照,用光栅光谱仪拍摄反激光二次谐波(5300(?))的光谱,从拍摄的大量的二次谐波照片中可观察到谱线的频移加宽、精细结构与空间细丝分裂现象。     

Spherical harmonics microwave algorithm for shape and location reconstruction of breast cancer tumor

A reconstruction algorithm to simultaneously estimate the shape and location of three-dimensional breast cancer tumor is presented and its utility is analyzed. The approach is based on a spherical harmonic decomposition to capture the shape of the tumor. We combine a gradient descent optimization method with a direct electromagnetic solver to determine the coefficients in the harmonic expansion as well as the coordinates of the center of the tumor. The results demonstrate the potential advantage of collecting data using a multiple-view/tomographic-type strategy. We show how the order of the harmonic expansion must be increased to capture increasingly "irregularly" shaped tumors and explore the resulting increase in the central processing unit (CPU) time required by the algorithm. Our approach shows accurate reconstruction of the tumor image regardless of the source polarization. This work demonstrates the promise of the algorithm when used on data corrupted with Gaussian noise and when perfect knowledge of the tumor electrical properties is not available.     

Gain, phase imbalance, and phase noise effects on error vector magnitude

The error vector magnitude (EVM) is extensively applied as a measure of communication systems' performance. In this paper, the effects of gain, phase imbalance, and phase noise on EVM are examined. The work is focused on single-carrier, linear, and memoryless modulated signals, such as phase-shift keying and quadrature amplitude modulation (QAM). The EVM is calculated under the assumption that the transmitted signal consists of zero-mean uncorrelated inphase and quadrature components that are corrupted by additive white Gaussian noise. The contributions of this paper are as follows. First, an expression for the EVM is derived using a simple model that accounts for linear transmitter and receiver imperfections, inspired by the works of Cavers and Liao, 1993. Second, a union bound on the symbol error rate (SER) is derived. The root mean square EVM is shown to be independent of the constellation shape. The SER, however, is sensitive to the individual transmitted symbols and, therefore, the constellation shape. The resulting equations are used to examine the relation between EVM, sideband suppression, and phase noise.     

宽频带幅度比和相位差测量系统的设计

AD8302是一款集测量幅度和相位于一体的单款集成电路,且测量精度高,测量频带范围宽。适用于移动通信及接收系统。介绍AD8302结构原理及工作模式,并结合C8051F单片机对AD8302测得的2路信号的幅度比和相位差值进行模数转换,构建一个基于C8051F单片机的片上数据采集系统,并利用VB语言编写单片机与PC机的串口通信,可将实时采集到的数据送到PC机中。     

NEW THREE PHASE VFVA SINE WAVE GENERATOR AND PWM HARMONICS ANALYSIS

The new three phase VFVA sine wave generator is presented in this paper. A new sampling holding three phase VFVA sine wave generator's principle, circuit and experimentation waveform are introduced. The principle of this sampling holding circuit is simple and the realization of har'dware circuit is easy. Here we describe the three phase reference sine wave which is produced by this generator's circuit and is required by PWM inverter is described in this paper, and also introduced the speed control and harmonir analysis of PWM inverter variable frequency.     

宽频带幅度比和相位差测量系统的设计

AD8302是一款集测量幅度和相位于一体的单款集成电路,且测量精度高,测量频带范围宽.适用于移动通信及接收系统.介绍AD8302结构原理及工作模式,并结合C8051F单片机对AD8302测得的2路信号的幅度比和相位差值进行模数转换,构建一个基于C8051F单片机的片上数据采集系统,并利用VB语言编写单片机与PC机的串口通信,可将实时采集到的数据送到PC机中.     

含有径向节点的拉盖尔-高斯光束产生涡旋高次谐波的特征

利用红外超快涡旋激光脉冲与气体介质相互作用可以产生携带轨道角动量的极紫外高次谐波。采用含有径向节点的拉盖尔-高斯（LG）光束作为驱动光,利用定量重散射模型计算单原子响应,通过求解谐波场在介质中传播的三维麦克斯韦方程以及在傍轴近似下的惠更斯积分,分别获得近场和远场高次谐波的强度和相位分布。结果表明:随着驱动光的径向节点数增加,高次谐波的强度分布呈现多环结构,相位分布上出现节点结构,强度分布的空间范围在近场减小,而在远场增大。相位匹配分析显示,短轨道和长轨道高次谐波的空间相干长度分布图对驱动激光的模式非常敏感,与高次谐波场在气体介质内的演化图像定性一致,解释了有径向节点的LG光束作用下产生的涡旋高次谐波的特征。     

Voltage variable microwave phase shifter

Results are given on the fabrication, test and theory of operation of a voltage-controlled, continuously variable phase shifter designed to operate from DC to 150 GHz. The device was fabricated in a way that makes it compatible with current gallium arsenide monolithic microwave circuit technology.     

基于谐波分析的相位型表面等离子体共振传感器

提出了一种利用电光调制和谐波分析的相位型表面等离子体共振(SPR)传感器结构。和传统的相位型SPR传感系统相比,该系统结构采用一路光路并用软件实现相位提取和分析,简化了系统结构;P光、S光采用共光路的光路结构,可以有效抑制相位噪声;可以使用较低电压的调制电源。利用该系统对不同浓度酒精溶液进行了测量,取得了和理论预期相一致的结果。     

Measurement of intermodulation products generated by structuralcomponents

A computer-controlled measurement system is described, developed to investigate intermodulation products generated by nonlinear junctions in antenna towers, mast support and mounting components. Results are presented which suggest that certain mechanical features, commonly encountered in some components, should be regarded as more likely to be associated with this cause of interference     

基于中心对称梯度幅值相位模式的单样本人脸识别

针对传统人脸识别算法在单训练样本情况下识别 效果不佳的问题,提出一种基于中心对称梯度幅值 相位模式(CSGMP)的单样本人脸识别算法。首先,提取人脸图像的梯度幅值和相位信息;然 后,用一种新 的中心对称局部方向模式(CSLDP)算子对梯度幅值进行编码,再将梯度相位量化到8个区间 进行编码,将 二者融合形成人脸图像的CSGMP特征;最后,分块统计直方图特征信息,将所有块的直方图 串联后作为 人脸图像的特征向量,利用最近邻分类器分类识别。在YALE和AR人脸库上进行测试的结果表 明,本文所提方 法简单有效,对光照变化、表情变化和部分遮挡等环境下单样本人脸识别具有较好的效果。     

Review of semiconductor microwave phase shifters

The electronically controlled phased array radar antenna has received considerable attention in the last decade. Requiring no mechanical motion for steering, it can scan in microseconds or, with some phase control elements, in nanoseconds. Even multiple beams can be formed electronically. In the future, for almost every antenna steering application, the electrically steered array will be desired provided cost, reliability, power handling capability, bandwidth, and insertion loss can be made comparable with the mechanical systems. At present, only the electronic array can be used to achieve microsecond steering. Both ferrite and semiconductor media have undergone serious development to meet the task of controlling rapidly the phase of the signals applied to elemental radiators in the phased array. In this paper, an attempt is made to review the progress and potential of the discrete increment, semiconductor controlled, microwave phase shifter.     

Measurement of photoconductivity with microwave bridge

When measuring the photoconductivity of low-loss materials at microwave frequencies, it is shown that an initially unbalanced bridge is more sensitive than an initially balanced one. In addition, an expression is derived for the effective conductivity in a material that is nonuniformly excited.     

Design of recursive polyphase networks with optimum magnitude and minimum phase

A novel approach to the design of recursive polyphase networks with application to multirate filtering and digital filter banks is proposed. To this end, Pelloni's method [4] is extended such that all zeros of the polyphase network are located on the z-plane unit circle and all poles are single, corresponding to an optimum magnitude response with minimum phase. An example, taken from transmultiplexing applications, shows that the proposed method results in substantially improved filter designs compared with the approaches of Bellanger et al. [1], Vary [6] and Pelloni [4].