An Analysis of the Diode Mixer Consisting of Nonlinear Capacitance and Conductance and Ohmic Spreading Resistance

A method is presented for calculating the mixer admittance matrix Y' which results when an ohmic impedance is connected in series with a diode mixer described by an admittance matrix Y. There are no restrictions on the frequency dependence of the ohmic impedance nor on the number of harmonic sidebands considered. The equations are worked out in detail for the "low Q" case in which signal, image, and intermediate frequencies are considered, and it is shown that Y' in this case is "nearly low Q." As a result of this analysis the usual criterion for good high-frequency mixing, i.e., that the product of the spreading resistance and the barrier capacitance be small compared with unity, is criticized and a new figure of merit is proposed. Explicit formulas have been derived for calculating the elements of Y' when Y represents the parallel combination of a nonlinear conductance and capacitance. In general, these formulas are cumbersome, but three special cases have been considered in detail.     

基于泰勒级数展开的蜂窝TDOA定位算法

基于用户位置的应用已经成为移动数据业务的重要组成部分,使得蜂窝系统用户定位技术成为蜂窝移动通信领域的研究热点。泰勒级数展开算法因为具有精度高和顽健性强等特点而在求解非线性定位方程组中得到了广泛的应用,但它对初始值有很强的依赖性。本文使用最小二乘方法估计用户位置的初始值并使用泰勒级数展开算法确定用户坐标。通过对算法的仿真分析,结果表明本算法具有近似于基于真实值的泰勒级数展开算法的性能。     

A behavioral circuit simulation model for high-power GaAs Schottky diodes

This paper proposes a physically based behavioral circuit simulation model for high-power GaAs Schottky diodes which is valid over all regions of operation. No conditional statements are needed to define the regions of operation. A new and more accurate method of obtaining depletion capacitance model parameters from the measured capacitance values is proposed. A simple current- and temperature-dependent resistance model is used to model the nonlinear diode resistance as well as contact and packaging resistances. The validity of the model is demonstrated under various DC and transient switching conditions. Simulation results are compared with the experimental data obtained from a 200 V GaAs Schottky diode. The diode model is tested at various temperatures in different test circuits and the simulation results are shown to be in excellent agreement with the measured data under static and dynamic switching conditions. The model can be easily implemented in other circuit simulators.<>     

Numerical analysis technique for diode-loaded dipole antennas

A circuit model for a double-loaded dipole electric field measurement probe that is valid for frequencies below 10 GHz is developed. A nonnegligible dipole radius and the nonlinear characteristics of the diode are taken into consideration. The dipole lumped-circuit elements and diode capacitances are determined by theoretical means, while the diode V-I characteristics and resistance are determined by a combined theoretical and empirical approach. Newton's iteration method is used to numerically solve the resulting nonlinear differential equation. Experimental measurements on a probe designed for operation between 1 and 1000 MHz are reported and compared with the theoretical results     

Application of Volterra-Wiener spline series for the analysis of nonlinear electric circuits

The functional atlas of the initial system of nonlinear differential equations is split into local charts with the help of a multidimensional Taylor series expansion. In each chart, the approximation with a weakly nonlinear Volterra-Wiener series up to the fourth order is used, where a chart is changed when its boundaries are crossed. It is established that the obtained approach allows one to increase the accuracy and reliability of the calculated output response of the nonlinear system as compared to the classical Volterra-Wiener series approach. The results of the numerical simulation of a nonlinear RC circuit are presented and the efficiency of the proposed method is shown.     

Perturbation-Based Fourier Series Analysis of Transistor Amplifier

A perturbation-based Fourier series model is proposed to approximate the nonlinear distortion in weakly nonlinear circuits. This general model is applicable to any set of multi-variable state equations that completely describe a nonlinear circuit. This model is applied to a common emitter amplifier circuit wherein the transistor is represented by Ebers–Moll nonlinear current equations. Appropriate state variables are defined, then the linear and nonlinear parts of the Ebers–Moll current equations are separated, and a small perturbation parameter is incorporated into the nonlinear part. Now these current equations are incorporated into the set of KCL, KVL equations defined for the circuit and the state variables are perturbatively expanded. Hence, multi-variable state equations are obtained from these equations. The state variables are approximated up to first order through Fourier series expansion, as described in the proposed model. The main advantage of the proposed model is that it is simple and straightforward approach to analyze weakly nonlinear circuits, as it involves matrix computations and the calculations of exponential Fourier coefficients.     

Spectral modeling of switched-mode power converters

A new modeling approach for the spectral analysis of pulsewidth modulated (PWM) converters with independent inputs is developed. The key of this approach is to extend the Volterra functional series to nonlinear systems with multiple independent inputs. After formulating the state-space equations describing the dynamical behavior of PWM converters, the Volterra transfer function characterizing the output frequency response can be obtained, which is then symmetrised to form the spectral model. Since the model is developed in a closed form, it is suitable for computer analysis. The modeling approach has been applied to various PWM converters, and the results are verified. The spectral models of different power converters can readily be obtained by using this general approach     

脉冲束六维非线性动力学方程级数解

针对脉冲束六维非线性动力学方程被积函数的不可积性,首先将方程的被积函数展为自变量的Taylor级数,通过直接积分获得方程关于自变量的一般级数解,然后进一步将自变量各阶项的系数对初值作Taylor展开,从而获得方程关于自变量及初值的级数解.对于脉冲束中任意粒子相对于参考粒子的相对运动动力学方程的求解问题,在方程的被积函数...     

基于切比雪夫多项式的新形式调频变标合成孔径雷达成像算法

该文提出一种基于切比雪夫(Chebyshev)多项式逼近的新形式的调频变标(Chirp Scaling, CS) SAR成像算法。该算法采用切比雪夫多项式逼近替代了原始CS算法中对回波信号2维频谱的泰勒(Taylor)级数展开近似,公式更加精确。然后利用光学系统抽象出的数学模型确定变标函数以校正距离徙动。并且该算法使由近似引入的误差有了上界限,改善了场景边缘点的聚焦效果,增加了场景的聚焦深度。仿真结果验证了该算法的有效性。     

Perturbation-Based Stochastic Modeling of Nonlinear Circuits

This paper presents a general model for a nonlinear circuit, in which, the circuit parameters (e.g. resistance and capacitance) are subject to random fluctuations due to noise, which vary with time. The fluctuating amplitudes of these parameters are assumed to be Ornstein–Uhlenbeck (O.U.) processes and not the white noise owing to temporal correlations. The nonlinear circuit is represented by a system of nonlinear differential equations depending upon a set of parameters that fluctuate slowly with time. To model these fluctuations, we use the theory of Ito’s stochastic differential equations (SDEs). Then the driving force of the circuit dynamics is in accordance with the general perturbation theory decomposed into the sum of a strong linear component and a weak nonlinear component by the introduction of a small perturbation parameter. The circuit states are expanded in the powers of this small perturbation parameter and recursive solutions to the various approximates obtained. Finally, the approximate expressions for the output states are obtained as stochastic integrals with respect to Brownian motion processes. The proposed method is applied to a half-wave rectifier circuit which is built out of a diode, a resistor and a capacitor. The diode is represented by nonlinear voltage–current equation, and resistance and capacitance are subject to random fluctuations due to noise, which vary slowly with time. The results, obtained using the proposed method, are compared with those obtained via the conventional perturbation-based deterministic differential equations model for a nonlinear circuit. Hence, the noise process component, present at the output, is obtained.     

窄带信号中的放大器"指纹"特征提取:原理分析及FM广播实测实验

 本文提出了一种利用放大器非线性特性来进行特定辐射源识别的多通道相关指纹识别(Multi-Channel Correlation Fingerprinting;MCCF)方法.该方法首先由功率放大器的泰勒级数模型导出窄带输出信号的载频分量和谐波分量表达式,然后利用两分量的关联性,将载频分量作为放大器激励信号的近似,代入谐波分量的表达式中,用最小二乘方法估计出"指纹"特征量.在此基础上本文分析了MCCF的指纹特征的可观测条件和估计的CRLB.该方法定义的指纹特征与放大器的级数模型有关,与激励信号的形式无关,因此是发射机固有的.依据本方法对长沙地区的调频广播的电台进行了"指纹"提取实测实验,在谐波分量功率比载频分量小60到80dB的典型条件下,对四个电台的发射机进行了有效的分类.     

Small-Signal Power Measuring Technique for Measuring the Frequency Response of Electroabsorption Modulators

We propose and demonstrate measurement of the frequency response of an electroabsorption (EA) modulator using an extended small-signal power measuring technique. In this technique, the modulator is driven by a microwave carrier amplitude modulated by a low-frequency signal, and the modulator frequency response is obtained without the need of a high-speed photodetector. Based upon the nonlinear characteristics of the EA modulator and the underlying principle of the present method, equations have been derived. A measurement scheme using a network analyzer and a low-speed photodetector has been proposed and constructed, and the experimental results confirm that our proposed method is as accurate as the swept-frequency measurement using a network analyzer directly     

Intermodulation nulling in HEMT common source amplifiers

A new model of the second- and third-order intermodulation products from HEMT and MESFET small-signal amplifiers, resulting from nonlinear drain-source current has been proposed in our previous publications. Based on this model, intermodulation nulling conditions in terms of the Taylor series coefficients, hence in terms of bias, have been investigated. This paper now examines the load dependence of the second- and third-order intermodulation products in HEMT small-signal common source amplifiers. Intermodulation nulling conditions are proposed and validated. This is useful in designing a high performance amplifier by calculation of optimum load for minimum distortion and studying distortion generation as a function of circuit topology     

Perturbation Analysis of Nonlinear Distortion in Analog Integrated Circuits

A method for predicting the distortion in weakly nonlinear analog circuits is presented, which relies on the classical theory of regular perturbation. Accordingly, a nonlinear circuit is described and analyzed as a perturbation of its linearized model, and the response to a periodic signal is analytically calculated through frequency-domain recurrent formulas. The method is simple and quite straightforward to apply, as it involves the calculation of frequency-domain transfer functions and of Fourier coefficients only, making it easily adaptable to any circuit topology. The method can be a valid alternative to the Volterra series method. A relationship between the proposed method and the Volterra series method is established, showing that they lead to very similar approximants to the solution. The method has been numerically tested in practical circuits wherein the devices are modeled by polynomial and exponential nonlinearities.     

基于小波变换的UKF改进算法及其应用

众所周知,UKF滤波的应用需要事先准确知道量测噪声的统计特性。首先简要分析了UKF滤波的基本算法,然后利用小波变换可以实时分离信号和噪声的特性,提出了一种在未知量测噪声条件下的UKF算法,该算法可以实时跟踪量测噪声的变化,即实现了对量测噪声的实时估计,从而解决了在未知量测噪声的条件下UKF滤波问题。最后讨论了该方法在信息融合中的应用,仿真结果证明了方法的有效性和实用性。     

基于顺序统计的窄带通信辐射源指纹特征抽取方法

该文提出将窄带射频功率放大器的静态非线性特性作为窄带无线通信设备的指纹特征。为了在未知放大器输入的前提下提取特征量,首先建立静态非线性的Hammerstein模型,然后分白化采样信号和估计泰勒级数的系数两个步骤提取特征。应用顺序统计的方法将白化信号转换为单调递增序列,通过最小二乘法对顺序统计结果做线性回归,得到泰勒级数的系数并作为个体特征量。通过数值仿真的方法提取了4种射频功率放大器模型的指纹特征,结果表明该文所提出的算法能够在特征空间中有效地识别不同的窄带射频功放。     

Large-signal lumped modeling and characterization of an IMPATT diode

An accurate large-signal lumped model of a Read IMPATT diode and external circuit is developed. The equations in state-space form are solved on an 8K-word computer, allowing complete interaction between the operator and the machine. Results obtained agree closely with measurement.     

Shot-Noise in Resistive-Diode Mixers and the Attenuator Noise Model

The representation of a pumped exponential diode, operating as a mixer, by an equivalent Iossy network, is reexamined. It is shown that the model is correct provided the network has ports for all sideband frequencies at which (real) power flow can occur between the diode and its embedding. The temperature of the equivalent network is eta/2 times the physical temperature of the diode. The model is valid only if the series resistance and nonlinear capacitance of the diode are negligible. Expressions are derived for the input and output noise temperature and the noise-temperature ratio of ideal mixers. Some common beliefs concerning noise-figure and noise-temperature ratio are shown to be incorrect.     

A New MIC Doppler Module

A new microwave integrated circuit (MIC) Doppler module comprising a germanium avalanche oscillator diode and a Schottky-barrier detector diode has been fabricated and analyzed. The module is essentially a high-stability MIC oscillator, which is connected to an X-band waveguide by means of a stripline probe. In addition to high minimum detectable signal level --100 dBm, a prominent feature that has been revealed is that the Doppler signal level is practically independent of oscillator output power under a specific condition. It is also shown that a simple adaptor attached to the module can provide a direction-sensitive device in a compact form.