高Tc超导薄膜/砷化镓场效应器件混合微波振荡器的研制

研制了一种高T_c超导薄膜/砷化镓场效应器件混合的微波振荡器,整个电路采用微带电路形式,制备在一片10mm×15mm的YBa₂Cu₃O_7-δ超导薄膜上。该振荡器采用共源和栅结串联反馈电路结构,以GaAs MESFET(NE72084)为负阻元件,利用高品质因数的超导微带谐振器作为稳频元件。通过提高谐振器的品质因数和调节它与MESFET的耦合强度,降低了振荡器的相位噪声。相位噪声在偏离载频(10.6GHz)为10kHz时达到-87dBc/Hz。     

多重相邻交联振荡器系统的停振

本文分析多重相邻交联振荡器链的停振现象，构造子多重交联振荡器链的上解与下解，比较了最邻近交联与多重交联的两种不同情况对停振的影响。     

毫米波宽带谐波振荡器的理论分析与实验研究

本文提出了一种分析立体型毫米波谐波宽带振荡器阻抗特性的混合场分析方法,首次计算了外电路阻抗(从有源器件向外看去的阻抗)随结构参数变化的曲线,并由此得出一些毫米波谐波振荡器设计准则。在理论分析的基础上我们研制了W波段宽带谐波振荡器,在75—100GHz的频率范围内获得了2—22.5mW的功率输出。     

利用场耦合理论研究开放微波谐振腔

利用电磁场的等效原理，将一个开放微波腔等效于一个闭合边界微波腔（即封闭微波腔）和开放边界（即行波吸收边界）两部分，然后利用等效封闭微波腔的本征模式及其与开放边界的耦合，建立了关于开放微波腔模式（即模式场分布、频率、品质因子）的耦合方程组，其中开放边界为行波吸收边界.以X波段六腔渡越振荡管为例进行分析，将该振荡管等效为封闭微波腔和同轴输出结构两部分，用SUPPERFISH获得封闭腔的各个模式场分布及频率，然后根据封闭微波腔与开放边界的耦合，求得六腔渡越振荡管的工作模频率为9.25GHz，品质因子为115.2，与实验测量结果基本符合.     

GL算法在FM振荡器的稳健性参数设计中的应用

针对FM振荡器幅度稳定性比较差的问题,运用GL算法,通过电路参数的合理搭配,减小了振荡管基极工作点的漂移,得出了比以往更好的稳定中心.     

微波传输路由的数学模型

在微波通讯中，电波射束和障碍物之间应留有足够的余隙，以保证能量的有效传输．本文考虑地球表面自然凸特征，建立在此意义下的余隙的数学模型，从而获得微波传输路由的数学模型．利用此模型的解与海拔制高点的余隙进行比较，便可获得工程建设中的最佳余隙值及相联系的有效的经济的路由设计．     

微波传输路由的数学模型

在微波通讯中，电渡射束和障碍物之间应留有足够的余隙，以保证能量的有效传输，本文考虑地球表面自然凸特征，建立在此意义下的余隙的数学模型，从而获得微波传输路由的数学模型，利用此模型的解与海拔制高点的余隙进行比较，便可获得工程建设中的最佳余隙值及相联系的有效的经济的路由设计。     

吸波材料与微波暗室吸波性能研究

主要解决入射波在尖劈吸波材料几何空缺间反射过程的问题以及微波暗室性能是否满足导引仿真要求的问题.对于问题一,首先建立了二维情况下入射波线在尖劈几何空缺间反射过程的数学模型,提出了临界状态的概念,根据光学原理,三角几何原理推出了辐射波在各个反射点处的入射角及反射点距尖劈底面高度表达式,求出了最终反射波的方向、辐射强度.最后根据坐标分解法将其拓展到三维空间.对于问题二,综合考虑辐射波在六个面间的相互影响,运用微元法的思想和微积分的相关知识,推导出静区直接接收到微波信号的公式以及微波信号经整个微波暗室内壁一次反射后被静区接收到的微波功率公式,用数值积分的方法求得了静区得到的反射信号的功率与静区直接得到的微波功率之比,并对部分反射光难以计算的问题提出了数学模型修正的建议和方法.     

分布作用腔振荡器的大信号研究

本文考虑了空间电荷的作用及互作用间隙宽度的影响,按矩形脉冲轴向高频场分布,建立了分布作用腔振荡器的大信号计算模型,对转换效率进行了计算研究.文中还给出典型情况下的详细结果,并进行了分析讨论。     

微波遥感水面油污状况的研究

本文研究了水面油污的微波反射及辐射特性,在实验室内进行微波介电系数的测量及水面油污反射率实验测量,实验结果和理论预期是一致的。在此基础上讨论了水面油层微波辐射与油层厚度的关系,微波检测水面油污的原理。分析结果,用S极化油面与水面亮度温度差或辐射亮度温度极化比可检测油层厚度。由于海上油污大部分小于2毫米厚度,用1.2—1.6厘米波段微波辐射计遥感油层厚度有较好的分辨率。毫米波段对检测薄油膜有较高的灵敏度。     

On the dynamics of a periodic Colpitts oscillator forced by periodic and chaotic signals

In this paper, we have examined effects of forcing a periodic Colpitts oscillator with periodic and chaotic signals for different values of coupling factors. The forcing signal is generated in a master bias-tuned Colpitts oscillator having identical structure as that of the slave periodic oscillator. Numerically solving the system equations, it is observed that the slave oscillator goes to chaotic state through a period-doubling route for increasing strengths of the forcing periodic signal. For forcing with chaotic signal, the transition to chaos is observed but the route to chaos is not clearly detectable due to random variations of the forcing signal strength. The chaos produced in the slave Colpitts oscillator for a chaotic forcing is found to be in a phase-synchronized state with the forced chaos for some values of the coupling factor. We also perform a hardware experiment in the radio frequency range with prototype Colpitts oscillator circuits and the experimental observations are in agreement with the numerical simulation results.     

A Joint DAE/PDE Model for Interconnected Electrical Networks

To model transmission lines effects in integrated circuits, we couple the network equations for the circuits with the telegrapher's equations for the transmission lines. This results in an initial/boundary value problem for a mixed system of Differential-Algebraic Equations (DAEs) and hyperbolic Partial Differential Equations (PDEs). By semidiscretization the system is transformed into differential-algebraic equations in time only. We apply this modeling approach to a CMOS ring oscillator, an oscillatory circuit with transmission lines as coupling units, and discuss the simulation results.     

Synchronization of van der Pol oscillator and Chen chaotic dynamical system

This paper addresses the synchronization problem of two different electronic circuits by using nonlinear control function. This technique is applied to achieve synchronization for the stable van der Pol oscillator and Chen chaotic dynamical system. Numerical simulations results are given to demonstrate the effectiveness of the proposed control method.     

A numerical scheme for highly oscillatory DAEs and its application to circuit simulation

A new numerical integration scheme for the simulation of differential–algebraic equations is presented. In the context of the computer-aided design of electronic circuits, the modeling of highly oscillatory circuits leads to oscillatory differential–algebraic equations mostly of index 1 or 2. Standard schemes can solve these equations neither efficiently nor reliably. The new discretiziation scheme is constructed in such a way as to overcome the problems of classical numerical methods. It uses the Principle of Coherence due to Hersch in combination with a multistep approach. A combined Maple and Fortran77 implementation of the presented integration scheme reduces the simulation time for a quartz-controlled oscillator to about 2% compared with standard methods. Therefore, it is a powerful tool for the design of highly oscillatory circuits. This revised version was published online in June 2006 with corrections to the Cover Date.     

Multiplication de fréquence et stabilité en phase

Summary A frequency multiplying system which delivers an exact multiple of the frequency of a 100 kc/s standard in the microwave region has been developed. High spectral purity of the signal has been obtained by servo-controlling the phase of a high frequency quartz crystal oscillator through an integrating filter with long time-constant.     

Multirate models for simulating a colpitts oscillator

A model based on multirate partial differential algebraic equations yields an efficient numerical simulation of electric circuits in radio frequency applications. Considering frequency modulation, free parameters of the model are determined appropriately by a minimisation strategy. We apply the multirate approach to simulate a modified version of a Colpitts oscillator, which exhibits frequency modulation at widely separated time scales. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

The nature of the bufferness phenomenon in weakly dissipative systems

We propose a mechanism for accumulating attractors in finite-dimensional weakly dissipative systems. The essence of this mechanism is that if a Hamiltonian or a conservative system with one and a half or more degrees of freedom is perturbed by small additional terms ensuring that it is dissipative, then under certain conditions, the number of its attractors appearing in small neighborhoods of different elliptic equilibriums or cycles of the nonperturbed system can increase without bound as the perturbations tend to zero. We consider meaningful examples from mechanics and radio physics: models of the bouncing ball dynamics, Fermi accelerations, the linear oscillator with impacts, and the self-excited oscillator with a discrete sequence of RLC circuits in the feedback circuit. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 146, No. 3, pp. 447–466, March, 2006.     

High-T c superconducting thin film/GaAs MESFET hybrid microwave oscillator

A high-T _c superconducting (HTSC) thin film/GaAs MESFET hybrid microwave oscillator operated at 10.6 GHz has been designed, fabricated and characterized. Microstrip line structures were used throughout the circuit with superconducting thin film YBa₂Cu₃O_7-δ(YBCO) as the conductor material. The YBCO thin films were deposited on 15 mm×10 mm×0.5 mm LaAlO₃ substrates. The oscillator was common-source, series feedback type using a GaAs-MESFET (NE72084) as the active device and a superconducting microstrip resonator as the frequency stabilizing element. By improving the unloaded quality factorQ ₀ of the superconducting microstrip resonator and adjusting the coupling coefficient between the resonator and the gate of the MESFET, the phase noise of the oscillator was decreased. At 77 K, the phase noise of the oscillator at 10 kHz offset from carrier was −87 dBc/Hz. Project supported by the National Center for Research and Development on Superconductivity of China.     

Secure communication by chaotic synchronization: Robustness under noisy conditions

In this work we present a thorough investigation of the effect of noise (internal or external) on the synchronization of a drive-response configuration system (unidirectional coupling between two identical systems). Moreover, since in every practical implementation of a communication system, the transmitter and receiver circuits (although identical) operate under slightly different conditions it is essential to consider the case of the mismatch between the parameters of the transmitter and the receiver. In our work we consider the non-autonomous second order non-linear oscillator system presented by G. Mycolaitis et al. in Proceedings of Seventh International Workshop on Nonlinear Dynamics of Electronic Systems [Globally synchronizable non-autonomous chaotic oscillator, Denmark, July 1999, pp. 277–280], which is particularly suitable for digital communications. Binary information is encoded by combining square pulses of two different frequencies selected so that the system is always in the chaotic regime independent of the encoded message.     

Stable torus and its bifurcation phenomena in a simple three-dimensional autonomous circuit

It is well known that a stable torus is observed as a result after the system meets the super-critical Neimark–Sacker bifurcation for a limit cycle. Although tori are easily observed in two-dimensional and periodically forced dynamical systems, there is a few papers about stable tori in three-dimensional autonomous systems. Besides, as physical circuit implementations, such circuits contain very special active elements, or have difficulty in realizing. In this paper, we show a very simple circuit of three-dimensional autonomous system, an extended Bonhöffer–van der Pol (BVP) oscillator, which is demonstrating a stable torus.Firstly we explain a discovery of the torus in a computer simulation of the model equation. To implement it as a circuitry, we design a new nonlinear resistor. Although this contains an FET and an op-amp, it is simpler than any other nonlinear resistors proposed in previous papers. We confirm that this BVP oscillator can generate a stable torus in a real circuitry. We thoroughly investigate the bifurcation phenomena of various limit cycles and tori in this circuit, i.e., a super-critical Neimark–Sacker and tangent bifurcations of limit cycles are concretely obtained, furthermore, phase locking and chaos regions are clarified in a bifurcation diagram.