Design of practical broadband matching networks with commensurate transmission lines

To design broadband matching networks for microwave communication systems, commercially available computer aided design (CAD) tools are always preferred. But these tools need proper matching network topology and element values. Therefore, in this paper, a practical method is proposed to generate distributed-element matching networks with good initial element values. Then, the gain performance of the designed matching network can be optimized employing these tools. The utilization of the proposed method is illustrated by means of the given example. It is shown that proposed method provides very good initials for CAD tools.     

A Modified Particle Swarm Optimizer and its Application to the Design of Microwave Filters

In this paper, a modified particle swarm optimization (PSO) algorithm is presented and its applicability is shown for the design of specific microwave filter as a case study of microwave components. In the proposed modified PSO algorithm, particles in the swarm are divided to form multiple sub-swarms. The social component of PSO’s velocity update equation is modified to include the effects of multiple sub-swarms. Five benchmark functions have been considered for testing the proposed algorithm. The approach has been tested for two basic modifications of PSO namely PSO with inertia weight (IW) and PSO with constriction factor method (CFM). The simulated results illustrate that the modified PSO algorithm has the potential to converge faster, thus reducing the computational expenses, while maintaining/improving the quality of solution. Finally, the proposed algorithm is used for the design of coupled microstrip line band pass filter which is a computationally expensive process when the design is conducted using evolutionary algorithms and electromagnetic (EM) simulation tools.     

Advanced types of the sensitivity analysis in frequency and time domains

The majority of standard tools for computer-aided design can perform only limited types of the sensitivity analysis: Spice determines operating-point sensitivities, and SpectreRF contains a parametric sensitivity analysis that can be used for determining the phase noise, for example. In the paper, some new types of the sensitivity analysis in frequency and time domains are described. These types of the analysis are not implemented in the standard circuit simulators.In the frequency domain, a procedure for determining the sensitivities of the noise figure is suggested. First, an improvement of the method for computing the noise figure is presented, which incorporates necessary circuit matching and eliminates the subtraction of output noise from the load at each frequency. Second, a simple formula is derived for computing the sensitivities of the noise figure. The sensitivity analysis in the frequency domain is generally demonstrated by means of a distributed microwave amplifier. The application of the sensitivity analysis of the noise figure for improving the noise properties of a monolithic microwave amplifier is described.In the time domain, a new recurrent formula is derived for the sensitivity analysis that efficiently uses high-order expressions of the algorithm for implicit numerical integration. Since the chosen integration algorithm is more flexible than the more frequently used Gear's one, the suggested formula leads to more efficient procedure. The sensitivity analysis in the time domain is important for analyzing symmetrical microwave circuits, because their operating-point sensitivities are zero in principle. For this reason, the significance of the proposed method is demonstrated by an analysis of a symmetrical radio-frequency CMOS multiplier. As an unusual example of exploiting the method, a temperature sensitivity analysis of a power operational amplifier is described.     

FIR Photonic Microwave Filter Design Employing Simulated Annealing Algorithm

Photonic microwave filters are important parts of fiber‐optic microwave/millimeter wave processing systems. In this paper, the synthesis problem of fiber‐optic FIR microwave filters is addressed and a novel method for designing photonic microwave filter employing a simulated annealing (SA) algorithm is proposed. The design problem of photonic microwave filter can be reduced to be a multi‐variable function optimization problem, which can be solved by a simulated annealing‐based algorithm. As an illustration of the application of SA to photonic microwave filter design, the synthesis of an optimizedFBG‐based photonic microwave filter is discussed. Numerical results show that the global minimum finding capability of SA makes it be an efficient way to design the photonic microwave filter. Numerical results also demonstrate that the proposed method can be applied to design different filtering systems with different constraints.     

Reliable CAD Analyses of CMOS Radio Frequency and Microwave Circuits Using Smoothed Gate Capacitance Models

The problems with convergence caused by both voltage- and charge-controlled models of MOSFET gate capacitances are often a limiting factor of the computer aided design tools. In the paper, an idea of the exponential smoothing of model discontinuities is proposed. The method is demonstrated on smoothing the gate capacitance discontinuity at zero drain-source voltage. An advanced integration algorithm convenient for the computer aided design of radio frequency and microwave CMOS circuits suppressing possible physically incorrect results of the traditional methods is also described. The updated model and algorithm are checked by analyzing a sophisticated CMOS flip-flop circuit.     

Neuro-fuzzy modeling techniquesfor microwave components

Two modeling techniques of microwave devices are proposed to generate neuro-fuzzy-based models. These techniques use the adaptive neuro-fuzzy inference system approach, which compensates the error between an initial coarse model and an electromagnetic simulator (or measurement data). The aim of these techniques is to generate accurate models from a set of fuzzy if-then rules and coarse models. Models so obtained could be integrated in a toolbox of any commercially available computer-aided design tools for radio frequency/microwave circuits. Results with artificial neural network and neuro-fuzzy based models are listed and discussed for a microwave tunable phase shifter.     

对地观测的微波散射成像方法

以微波为探测手段进行对地成像观测,能够全天候、全天时工作,在许多技术领域得到了重要应用,对微波成像的新思想、新体制、新技术的探索,也是一个非常活跃的研究领域。该文提出了一种新的微波成像方法,称为微波散射成像方法,该方法可采用收发分置工作方式,工作时只需要以单色波照射待成像地域。原理性成像模拟结果表明,使用这种方法可以获得被观测地域高几何分辨率和高辐射分辨率的微波图像。     

Conception assistée par ordinateur des circuits intégrés monolithiques hyperfréquences

Computer aided design of microwave monolithic integrated circuits must combine two different fields. The first domain is the simulation of microwave circuits taking into account non linear aspects development of time domain and harmonic balance simulation algorithms specialized for microwave circuits. In the second place are found, the layout algorithms which were developed for logic circuits (on Si or GaAs). The association of these two types of algorithms leads to the constitution of aCad workstation for microwave monolithic integrated circuits. Two examples of design and realization of integrated circuits with these tools are presented.     

基于稀疏贝叶斯学习的超材料孔径计算微波成像系统离网格成像方法

基于超材料孔径的计算微波成像可以看作微波压缩感知成像。这种成像方式的成像效果受网格失配误差的严重影响。该文针对超材料孔径计算微波成像系统对2维场景的重构过程进行分析,构建了一种基于Sinc插值函数的2维离网格(Off-grid)观测模型,并在此基础上提出一种基于稀疏贝叶斯学习的Sinc插值离网格成像方法(OGSISBL)。在期望最大化算法的框架下,恢复散射体回波的幅值和位置,同时校准网格失配误差。通过对超材料孔径计算微波成像系统的仿真数据进行成像处理验证所提算法的性能,结果表明所提算法具有很强的鲁棒性。     

A novel approach to generate a chirp microwave waveform using temporal pulse shaping technique applicable in remote sensing application

Microwave photonics is a prominent field in which photonic technologies are used to empower and extend the functionalities of microwave system which is a very tough exercise to fulfil directly in microwave domain. A photonic technique to generate a high chirp rate arbitrary microwave waveform using dual-drive LiNbO₃ has been put forward and demonstrated experimentally in this paper. Nowadays in order to increase the Range-Doppler resolution of radar, the chirp microwave waveform is widely used. The Mach-Zehnder modulator (MZM) performs the intensity modulation techniques which can operate on the principle of electro-optic effect. In this paper, the authors used a very simple and straightforward method of producing chirped arbitrary millimetre waveform by change in phase at the two arms of dual-drive LiNbO3 MZM. The generated waveform has the 3 dB bandwidth of 12.6 GHz which exists in extremely high-frequency band applicable in high-frequency microwave radio relay, microwave remote sensing, radar range resolution and millimetre wave scanner. The proposed design is simpler, cost-effective and compact than the previously proposed model of chirped waveform generation using MZM and fibre Bragg grating.     

The influence of microwave pulse width on the thermal burnout effect of an LNA constructed by a GaAs PHEMT

In this paper, the influence of microwave pulse width on the thermal burnout effect of a low noise amplifier (LNA) constructed by a GaAs pseudomorphic high electron mobility transistor (PHEMT) is theoretically analyzed and further verified with simulation and experimental results. By analyzing the electrical procedure and the thermal procedure, a theoretical model of the thermal burnout effect of the studied LNA is established according to the properties of microwave pulses and the structure of the LNA and GaAs PHEMT. Based on the theoretical model, the analytical relationship between the microwave pulse width and the thermal burnout power threshold is further obtained. According to the limitations caused by the approximations in the process of modeling, the available microwave pulse width range for the proposed analytical relationship is more than a nanosecond level and less than a microsecond level. The coefficients of the proposed analytical relationship can be determined by fitting at least two sets of simulation or experimental results, which can greatly reduce the simulation or experimental costs. Finally, the analytical relationship is verified by simulation and experimental results. The results show that the proposed analytical relationship is suitable to estimate the thermal burnout power threshold for a given microwave pulse width within the limit of microwave pulse width range.     

Simultaneous Optical Spectral Shaping and Wavelength-to-Time Mapping for Photonic Microwave Arbitrary Waveform Generation

Photonic microwave arbitrary waveform generation (AWG) based on simultaneous optical spectral shaping and wavelength-to-time mapping in a single specially designed linearly chirped fiber Bragg grating (LCFBG) is proposed. In the proposed approach, the spectrum of a transform-limited ultrashort optical pulse is spectrally shaped, and at the same time is wavelength-to-time mapped by the LCFBG to generate a microwave pulse with a shape identical to that of the shaped optical spectrum. By designing the LCFBG to have an arbitrary reflection profile, a microwave arbitrary waveform is generated. A simple and effective technique to synthesize the LCFBG with an arbitrary reflection response is proposed. Since amplitude-only index modulation is required, the designed LCFBG can be easily fabricated. Two examples showing the generations of a chirped microwave pulse and an ultra-wideband monocycle pulse are experimentally demonstrated.      

基于变换光学的微波加热用超表面数值研究

由于单个微波源的功率值有限,工业上往往采用多源微波加热以满足大功率需求。然而,额外 的微波馈口将增加端口间耦合,可能引起微波源损坏。因此,提出一种基于变换光学的新型超表面,使微波在 进入加热腔体的方向上正常传播而在相反方向被阻挡,从而减少功率反射和耦合。在二维数值模型中,采用 反向传播神经网络优化了超表面的介电性能,使得单源和双源微波加热的能量效率分别提高了42. 2%和53. 3%,且 均具有较好的加热均匀性。数值计算结果表明,超表面可工作在2. 45 GHz 频率,具有60 MHz 的带宽,工业应用前 景良好。     

Recent developments in lightwave network analysis

The widespread use of photonic systems having microwave modulation bandwidths, coupled with the inclusion of photonic components in microwave and millimetre-wave systems, is creating a demand for efficient characterisation techniques. In particular, new tools will be required for the measurement of fundamental quantities such as the microwave frequency response, bandwidth, gain and return loss of microwave photonic components. However, existing lightwave measurement techniques are primitive when compared with conventional RF and microwave network analysis. This paper provides a review of the theory and techniques used for the small-signal characterisation of microwave photonic components. State-of-the-art architectures for lightwave network analysers and the corresponding two-port calibration techniques are described     

数字和模拟微波混合传输的研究与实现

随着微波数字化的进程,传统的微波站已无法满足日益增长的传输业务。研究发现,利用早期的模拟微波传输通道来同时传输模拟和数字微波信号,是一种可行的解决办法。文章以湖北省西南干线微波系统改造为例,提出了数字和模拟微波混合传输系统的改造方法及相关的关键问题。     

Smith charts are easy. I

Smith charts are an extremely powerful visualization tool used by microwave engineers for designing impedance-matching circuits, filters, amplifiers and transmission lines. But, their usefulness extends beyond traditional analog and microwave analysis and design. They can be powerful tools for high-frequency digital designers as well. The basics of Smith charts are covered in this article and it is shown how easy they are to use     

涡旋微波量子雷达

电磁波轨道角动量(OAM)量子态指构成电磁波的每个电磁波量子均具有OAM,是涡旋电磁波的重要形态之一。在微波波段,这种电磁波量子称为“涡旋微波量子”。涡旋微波量子与传统平面波微波量子具有不同的物理特性,针对传统吸波材料具有强反射系数,造成雷达散射截面积(RCS)增加,并提升目标回波的接收信号功率和检测概率,是对抗基于吸波材料的隐身目标之利器。该文提出了基于OAM量子态的涡旋微波量子雷达,给出了基本物理架构和数学模型,借助量子电动力学(QED)从理论上分析了涡旋微波量子的高回波功率特性,并通过实验验证了理论分析的正确性。在收发端均采用相同极化方式下,与传统平面波雷达相比实验中回波功率提高约9 dB。同时,配合典型雷达工作参数进行了仿真,明确了涡旋微波量子雷达在接收功率和检测概率等性能指标上的提升,进一步展现了涡旋微波量子针对吸波材料的反隐身能力。      

基于微波光子的一体化可重构电子系统

针对一体化电子系统必须具备宽带、多频段信号处理能力等要求，提出了一种基于微波光子技术的一体化可重构电子系统方案，采用微波光子混频技术实现宽带、多频段射频信号光域变频，使用微波光子交换技术实现信道复用，系统具备四路并行处理能力，通过软件配置可动态重构各信道功能。