Two-Stream Free Electron Lasers: Physical Analysis of the Systems with Monochromatic Pumping

Nonlinear selfconsistent theory of the Two-stream Superheterodyne Free Electron Lasers (TSFELs) is represented. The one-sectional and klystron type models of TSFEL-amplifiers are analyzed. It is shown that such systems can provide extremely high levels of amplification, and, at the same time, high levels of the input-output decoupling.     

New method and circuit for processing of band-limited periodic signals

The paper presents a reconstruction of analogue multi-harmonic signals, from a number of integrated values of input signals. Based on the value of the integral of the original input signal, with a known frequency spectrum but unknown amplitudes and phases, a reconstruction of its basic parameters is done by the means of derived analytical and summarized expressions. It is applied to signal reconstruction, spectral estimation, system identification, as well as in other important signal processing problems. The proposed method of processing can be used for precise RMS measurements (or power and energy) of periodic signal based on the presented signal reconstruction. Subsequent calculation of all relevant indicators related to the monitoring and processing of ac voltage and current signals is provided in this manner. The paper investigates the errors related to the signal parameter estimation, and there is a computer simulation that demonstrates the accuracy of these algorithms.     

基于多谐波微多普勒信号分析的目标摄动参数提取方法

针对具有微多普勒特征的摄动目标回波信号,该文提出了目标摄动频率、振幅参数的估计方法。基于摄动目标的多谐波微多普勒回波信号模型,推导出了谐波频域峰值比与目标振幅比、最大多普勒频偏与目标振幅的定量关系,实现了由摄动目标回波信号估计摄动参数。该方法适用于具有多谐波微多普勒特征的目标探测。仿真结果表明了该方法的有效性。     

Scalable Multi-harmonic Large-Signal Model for AlGaN/GaN HEMTs Including a Geometry-Dependent Thermal Resistance

A scalable large-signal model of AlGaN/GaN High electron mobility transistors (HEMTs) suitable for multi-harmonic characterizations is presented.This model is fulfilled utilizing an improved drain-source current (Ids) formulation with a geometry-dependent thermal resistance (Rth) and charge-trapping modification.The Ids model is capable of accurately modeling the highorder transconductance (gm),which is significant for the prediction of multi-harmonic characteristics.The thermal resistance is identified by the electro-thermal Finite element method (FEM) simulations,which are physically and easily scalable with the finger numbers,unit gate width and power dissipations of the device.Accurate predictions of the quiescent currents,S-parameters up to 40GHz,and large-signal harmonic performance for the devices with different gate peripheries have been achieved by the proposed model.     

基于频谱特征分析的多谐波时间调制阵列测向方法

针对基于谐波特征分析的时间调制阵列(time-modulated array, TMA)测向技术中信息利用率低的问题,提出了一种基于信号频谱特征分析的多谐波TMA测向方法.通过分析接收信号的频谱特征,构建了基于信号频谱特征多谐波测向模型,推导了基于频谱特征的来波方向最优线性无偏估计(best linear unbiased estimation, BLUE)表达式,从而提高了测向精度及稳定性.以BPSK信号为例,通过仿真实验验证了所提算法的有效性,同时搭建了工作于S频段的二单元TMA测向系统证实了所提方法的可行性.     

基于双向牵引技术的射频功放设计与仿真

射频功率放大器是无线通信系统的核心部件,其输出功率和附加效率是设计的重点和难点,现有方法很难在功率和效率之间取得一致.为了解决这一问题,文中在综合考虑谐波分量以及负载阻抗、源阻抗对输出功率和附加效率影响的基础上,采用新型多谐波双向阻抗牵引技术,结合实例设计了一种高效率的射频功率放大器.在ADS中进行仿真,仿真结果表明功放在获得最佳附加效率的同时又有较高输出功率,证明了该方法的有效性.     

Harmonic Optimization of Rationally Synchronized Oscillators

A new optimization technique is presented for the design of synchronized oscillators with a rational ratio between the input- and output-frequency. The synchronization bandwidth is increased through the generation of the optimum harmonic components of the oscillator- and the input-signal by means of a multi-harmonic load. The synchronization loci are calculated for different values of these harmonic components by means of the use of an auxiliary generator. A 5–3.75 GHz rationally synchronized oscillator has been designed and optimized to obtain a maximum synchronization bandwidth, obtaining a good agreement between the simulated and experimental results.      

一种复杂波形信号产生器的设计与实现

介绍了一种复杂波形信号产生器的设计与实现,采用高速直接数字频率合成器产生各种复杂波形信号,并且通过微波宽带倍频器对DDS产生的复杂波形信号进行倍频,从而实现对DDS输出信号带宽的扩展,最终产生各种宽带复杂波形信号。文中介绍了设计方案与实现方法,并研制出工程样机。最终设计的复杂波形信号产生器能够实现线性调频、非线性调频、相位编码等多种复杂波形信号,输出信号带宽最高可达1 GHz。     

Multitone signals with low crest factor

After an introductory discussion of real-valued and complex signals, it is shown that minimizing the crest factor (CF) of multitone signals is closely related to the construction of complex sequences with low sidelobes in their aperiodic autocorrelation function. Inspired by this observation, a lower bound on the achievable CF is derived. Four differing algorithms for the reduction of the CF of complex multitone signals are compared with each other by computer simulation. The preferred algorithm is presented in detail, and its convergence is proven. Examples of multitone signals with up to 15 tones and lower CF than previously reported in the literature are given     

Alternative approach to dynamic I/V characterisation of microwave FETs

A new and simple approach for the measurement of active device dynamic output I/V characteristics is presented. Device characterisation is performed making use of multi-harmonic exciting signal and variable loads at the output port. The measurement bench has been used to characterise a GaAs 1 mm gate periphery PHEMT as a test vehicle. The results, obtained making use of the proposed setup, successfully compare with those obtained via traditional pulsed measurement systems.     

Design and analysis of a microwave large-range variable phase-shifter based on an injection-locked harmonic self-oscillating mixer

In this letter, a new microwave variable phase-shifter based on an injection-locked harmonic self-oscillating mixer, is presented for its application in an active microstrip phased antenna array. The circuit provides the double functionality of variable phase-shifter and down-converter. Maximum conversion gain is obtained, through the optimization of a new multi-harmonic load at the input-port of the circuit. The ranges of synchronized operation are analyzed versus the circuit parameters and the corresponding phase-shifts are calculated. The stability of the synchronized solutions is analyzed using the envelope transient simulation method. An 11.25-1.5-GHz down-converter with a 3.25-GHz free-running frequency has been designed, providing a phase-shift variation at intermediate frequency up to 540/spl deg/, with a 4.5-dB conversion gain. A good agreement between the simulated and experimental results has been found.     

一类基于非线性PCA准则的复数信号盲分离算法

在阵列信号处理过程中，经常遇到复数信号盲分离问题。例如，卷积混合型的源信号的盲分离；声纳信号盲分离。本文提出了一类基于非线性准则的复数信号盲分离算法。将非线性函数引入学习过程，由算法自动调节学习速率。计算机仿真实验验证了算法的有效性，文中给出了验证结果。     

线性调频与相位编码混合雷达信号处理仿真

为了保证雷达系统能够在复杂的电磁环境中有效地工作,雷达信号的选择尤为重要。本文采用线性调频信号与相位编码信号相结合的码内线性调频信号作为雷达信号,针对这个信号进行了整个雷达信号处理的仿真。仿真结果表明,码内线性调频信号具有较好的抗干扰的特性。     

The bispectrum of complex signals: definitions and properties

The symmetry properties and the relationship between all forms of third-order cumulants of complex signals are investigated. It is shown that all cumulants (for different position of the complex conjugate) are related by simple transformations. Autoregressive modeling of complex-valued signals using third-order cumulants is also investigated. It is shown that modeling of complex-valued signals requires a different approach from modeling of real-valued signals     

Nonparametric polyspectral estimators for k-th-order (almost) cyclostationary complex processes

Higher-order almost cyclostationary complex processes are complex random signals with almost periodically time-varying statistics, which is important to the research of non-Gaussian signals in information system. In this paper, smoothed polyperiodograms are proposed for related to cyclic polyspectral estimation and are shown to be consistent and asymptotically complex normal. Asymptotic covariance expressions are derived along with their computable forms.     

复高阶周期平稳信号的非参数多谱估计

本文研究利用平滑周期图作为离散时间k阶复周期平稳过程k阶循环谱估计的相容性和渐近复正态性,并导出了其渐近协方差表达式.     

NONPARAMETRIC POLYSPECTRAL ESTIMATORS FOR k-TH-ORDER (ALMOST) CYCLOSTATIONARY COMPLEX PROCESSES

Higher-order almost cyclostationary complex processes are complex random signals with almost periodically time-varying statistics, which is important to the research of non-Gaussian signals in information system. In tins paper, smoothed polyperiodograms are proposed for related to cyclic polyspectral estimation and are shown to be consistent and asymptotically complex normal. Asymptotic covariance expressions are derived along with their computable forms.     

The bond between causal complex cepstra and Sheffer polynomials

A strong bond is established between causal complex cepstra and Sheffer polynomials. This bond results in the generation of parametric classes of discrete-time signals and their associated complex cepstra. These signals generally have more advanced singularities than the poles of signals with rational z-transforms. Examples are presented which illustrate the behavior of signals having branch points and essential singularities.     

基于半实物仿真的复杂信号生成设计

针对卫星导航系统干扰模拟与抗干扰测试需求,基于半实物仿真原理,提出了一种利用ADS软件和矢量信号发生器产生自定义波形复杂信号的方法。对半实物仿真系统的硬件平台的搭建要点进行了介绍,完成了复杂信号在ADS系统平台下的建模与仿真,阐述了半实物仿真流程。利用矢量信号分析仪89600S对生成的复杂信号进行了测试,并通过与ADS仿真结果的对比分析,验证该方法的可行性。