Time‐varying linear controllers for exponential tracking of non‐holonomic systems in chained form

In this paper, the authors address the tracking problem for non‐holonomic systems in chained form with target signals that may exponentially decay to zero. By introducing a time‐varying co‐ordinate transformation and using the cascade‐design approach, smooth time‐varying controllers are constructed, which render the tracking‐error dynamics globally ??‐exponentially stable. The result shows that the popular condition of persistent excitation or not converging to zero for the reference signals is not necessary even for the globally ??‐exponential tracking of the chained‐form system. The effectiveness of the proposed controller is validated by simulation of two benchmark mechanical systems under non‐holonomic constraints. Copyright © 2006 John Wiley & Sons, Ltd.     

Output tracking with disturbance attenuation for cascade control systems subject to network constraint

In this paper, we investigate the output tracking control and disturbance attenuation for a class of cascade control systems subject to network‐induced delays. In order to indicate the time‐varying characteristics and uncertainty of network‐induced delays, a switched system approach is applied to the cascade architecture. This leads to the simultaneous design of controllers and switching signals in terms of the network transmission. Unlike the traditional cascade control design approach, which needs to first tune the secondary controller and then the primary one, we can provide a simultaneous design method of the double‐loop controllers and switching signals to make the networked cascade control system achieve the output tracking performance with disturbance attenuation. Finally, two examples are proposed to demonstrate the feasibility and the effectiveness of the approach.     

New approach for the analysis and design of negative‐resistance oscillators: Application to a quasi‐MMIC VCO

This article proposes a new approach for the analysis and design of negative‐resistance oscillators using computer‐aided engineering tools. The method presented does not require any special probe and makes the oscillator design similar to the methodology applied to amplifiers. It speeds up convergence and avoids uncertainties in the solution. The negative‐resistance oscillator is split into two parts: an active‐amplifying part and a resonator part. A chain is constructed by linking both parts and repeating them several times, which is known as the repeated circuit simulation procedure. This method allows the separation of the signal flowing between them. Small‐signal AC‐sweep and harmonic‐balance techniques, both available in several commercial software packages, are applied. This method is theoretically justified and shows convergence with less iteration. Furthermore, it is more robust than standard harmonic‐balance probes in the case of multiple frequencies of oscillation. It has been demonstrated in the design of a quasi‐MMIC VCO. This VCO has an external resonator circuit (coaxial resonator and varactor) and a MMIC negative‐resistance circuit, which was manufactured using ED02AH p‐HEMT technology (OMMIC). © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

Rapid surrogate‐assisted design optimization of minimum‐size broadband branch‐line couplers with variable topology

This work discusses simulation‐driven design of miniaturized wideband branch‐line couplers with a variable topology. Size reduction is enabled here by replacing uniform transmission lines of the original coupler with slow‐wave structures in the form of cascaded compact cells and meander lines. The primary goal is to determine a number of cells in the cascade and particular cell dimensions for which the minimum size of the coupler as well as its required operating conditions are ensured. To this end, we employ a surrogate‐assisted technique involving a trust‐region gradient search framework. Computational efficiency of the design process stems from estimating the Jacobian of circuit responses at the level of a low‐fidelity model of the cascade. The latter is composed in a circuit simulator from duplicated EM‐evaluated data blocks of a single cell and is well correlated with the corresponding high‐fidelity model. The key advantage of this work is the utilization of a reconfigurable, cheap, and well‐aligned low‐fidelity model. The proposed approach is demonstrated through design of a minimum‐size two‐section branch‐line coupler with quasi‐periodic dumbbell‐shaped cells and meander lines. Excellent circuit performance as well as its small size showcase the reliability and usefulness of the presented method. Experimental verification is also provided.     

A novel full‐wave CAD for the design of tapered leaky‐wave antennas in hybrid waveguide printed‐circuit technology

This work presents a novel computer‐aided design (CAD) tool for the design of tapered leaky‐wave antennas (LWAs) in hybrid waveguide printed‐circuit technology. The software package is composed of several tools, which are connected together to provide a semi‐automated step‐by‐step design procedure. The design procedure is presented and the different tools are described, together with the involved theory, leading to the design of tapered LWAs. A practical taper design is performed, and comparisons with simulations using commercial software (HFSS) are presented for validation purposes. Due to the full‐wave nature of the technique used in the analysis engine, excellent agreement is shown between the proposed 2D‐based approach, and 3D HFSS results. Also, the analysis procedure is fast, thus leading to semi‐automated designs that are not affordable with common 3D optimization techniques. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

Closed‐form approach to design distributed matching networks for high‐frequency amplifiers

Based on the use of distributed lossless elements, a closed‐form synthesis for double‐frequency‐matching networks is introduced with an emphasis on the design of high‐frequency amplifiers. Three different circuit conditions are considered and design relationships are provided and discussed. Finally, the proposed approach, which uses the circle method, is successfully employed to design a Ka‐band (26–32 GHz) linear amplifier with gain equal to 8 dB and return loss greater than 10 dB for the considered band. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

Hybrid Ku‐band low‐noise amplifier for mobile DBS active phased‐array antennas

In this article we present a two‐stage Ku‐band low‐noise amplifier (LNA) using discrete pHEMT transistors on non‐PTFE substrates for low‐cost direct broadcast satellite (DBS) phased‐array systems (patent pending). The vertical input configuration of the LNA lends itself to direct integration with input port of antenna modules of the phased array, which minimizes preamplification losses. DC decoupling between LNA stages is realized using interdigital microstrip capacitors such that the implementation reduces the number of discrete microwave components and thereby not only reduces the component and assembly costs but also decreases the standard deviation of such crucial parameters of phased‐array systems as the end‐to‐end phase shift of the amplifier and the amplifier gain. Using the proposed printed decoupling capacitors, a cost reduction better than 30% of the original costs has been achieved. Additionally, we present a hybrid design procedure for the complete LNA, including its input and output connectors as well as packaging effects. This method is not based on parameter extraction, but encompasses electromagnetic (EM) field simulator results which are further combined using a high‐level circuit simulator. According to the presented measurement results, the implemented Ku‐band LNA has a noise figure better than 0.9 dB and a gain higher than 20 dB with a gain flatness of 0.3 dB over a 5% bandwidth. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

Event‐triggered cascade high‐gain observer and its application

In this article, we consider the event‐triggered cascade high‐gain observer (ETCHGO) for a class of nonlinear systems. By cascading lower dimensional observers, we design a cascade high‐gain observer together with a Zeno‐free event‐triggered mechanism to estimate the state of the plant. We show that the ETCHGO has the same steady‐state performance as the continuous‐time cascade high‐gain observer, that is, there is a finite time after which the estimation error will not exceed the given threshold, and moreover, the finite time and the threshold can be made sufficiently small by adjusting some design parameters. We also investigate an ETCHGO with saturation, which will reduce the peaking value while maintaining the steady‐state estimation performance. Furthermore, we use the ETCHGO with saturation to solve the output feedback stabilization problem for a class of nonlinear systems. An example is given to illustrate our results.     

Analysis and design of packaged and ESD protected BiCMOS RF front‐end for a UHF receiver

The design of packaged and ESD protected RF front‐end circuits for UHF receiver working at ISM band is presented. By extensively evaluating the effects of the package and ESD parasitics on the LNA input impedance, transconductance, and noise figure, some useful guidelines on the design of inductively degenerated common emitter LNA with package and ESD protection are provided. In addition, by taking advantage of both the bipolar and MOSFET devices, a BiFET mixer with low noise and high linearity is also described in this article. With the careful consideration of the tradeoffs among noise figure, linearity, power gain, and power consumption, the front‐end is implemented in a generic low‐cost 0.8‐μm BiCMOS technology. The on‐board measurement of the packaged RF front‐end circuits demonstrates a 20.3‐dB power gain, 2.6‐dB DSB noise figure, and ?9.5‐dBm input referred third intercept point while consuming about 3.9‐mA current. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Building design‐time and run‐time knowledge for QoS‐based component assembly

Modern software systems are required to dynamically adapt to changing workloads, scenarios, and objectives and to achieve a certain Quality of Service (QoS). Guaranteeing QoS requirements is not trivial, as run‐time uncertainty might invalidate the design‐time rationale, where software components have been selected by means of off‐line analysis. In this work, we propose a QoS‐based feedback approach that makes a combined use of design‐time predictions and run‐time measurements to manage QoS data over time and support software architects while selecting software components that best fit QoS requirements. We illustrate the feasibility and efficacy of the approach on a case study, where the quantitative evaluation shows how the analysis effectively identifies the sources of QoS violations and indicates possible solutions to achieve QoS requirements.     

Global output feedback stabilization of upper‐triangular nonlinear systems using a homogeneous domination approach

This paper addresses the problem of global output feedback stabilization for a class of upper‐triangular systems with perturbing nonlinearities that are higher‐order in the unmeasurable states. A new design method based on the homogeneous domination approach and finite‐time stabilization technique is developed, which leads to global output feedback stabilizers for the upper‐triangular nonlinear systems under a homogeneous growth condition. A new perspective shown in this paper is that the finite‐time stabilization, in addition to its faster convergence rate, can also be utilized to handle control problems that were previously unresolved under asymptotic stabilization. Copyright © 2006 John Wiley & Sons, Ltd.     

Frequency‐dependent maximum average power‐handling capabilities of single and edge‐coupled microstrip lines on low‐temperature co‐fired ceramic (LTCC) substrates

The frequency‐dependent maximum average power‐handling capabilities (APHCs) of single and edge‐coupled microstrip lines (MLs) on low‐temperature co‐fired ceramic (LTCC) substrates are investigated in this article. Although LTCCs have excellent high‐frequency performance, the thermal conductivity is about 2.0–3.0 W/m°C, which is much smaller than that of sapphires, alumina, silicon, and GaAs. The method used to predict the APHC is based on the calculated conductive and dielectric attenuation constants for different modes, and the proposed multilayer thermal model for the temperature rise. Numerical investigations are carried out to examine the effects of geometric and physical parameters on the wideband pulse responses and maximum APHC for single finite‐ground thin‐film and coupled MLs, respectively. Methodologies to enhance the power‐handling capability which are useful in the design of high‐density microstrip interconnects on or embedded in multi‐layer LTCCs are proposed. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

Design and simulation of a flexible beamforming interface for MIMO receivers using a Butler labyrinth

This article focuses on the design and simulation of a new component for analog beamforming based on the Butler labyrinth. The proposed component enables the analysis of four‐antenna beamforming in systems with two receive channels. The problem was to design a component that would enable simulation of a MIMO receiver with an accurate account of the analog beam‐former effects on the digital signal processing level. The entire process is described—from layout design to the final DSP level integration and simulation. The performance of the simulated Butler component is compared to that of an ideal, theoretical one. The differences in the results indicate the importance of taking into account the effects of the layout level design on the DSP simulation level. The new component proves valuable for the bottom‐up approach in the design and simulation of a wireless system. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Stability analysis and design of nonlinear sampled‐data systems under aperiodic samplings

In this paper, the problem of exponential stability analysis and the design of sampled‐data nonlinear systems have been studied using a polytopic linear parameter‐varying approach. By means of modeling a new double‐layer polytopic formulation for nonlinear sampled‐data systems, a modified form of piecewise continuous Lyapunov‐Krasovskii functional is proposed. This approach provides less conservative robust exponential stability conditions by using Wirtinger's inequality in terms of linear matrix inequalities. The distances between the real continuous parameters of the plant and the measured parameters of the controller are modeled by convex sets, and the analysis/design conditions are given at the vertices of some hyper‐rectangles. In order to get tractable linear matrix inequality conditions for the stabilization problem, we performed relaxation by introducing a slack variable matrix. Under the new stability criteria, an approach is introduced to synthesize a sampled‐data polytopic linear parameter‐varying controller considering some constraints on the location of the closed‐loop poles in the presence of uncertainties on the varying parameters. It is shown that the proposed controller guarantees the exponential stability of the closed‐loop system for aperiodic sampling periods smaller than a known value, ie, maximum allowable sampling period. Finally, the effectiveness of the proposed approach is verified and compared with some state‐of‐the‐art existing approaches through numerical simulations.     

Analysis and design of a fully integrated CMOS low‐noise amplifier for concurrent dual‐band receivers

This article thoroughly analyzes a concurrent dual‐band low‐noise amplifier (LNA) and carefully examines the effects of both active and passive elements on the performance of the dual‐band LNA. As an example of the analysis, a fully integrated dual‐band LNA is designed in a standard 0.18‐μm 6M1P CMOS technology from the system viewpoint for the first time to provide a higher gain at the high band in order to compensate the high‐band signal's extra loss over the air transmission. The LNA drains 6.21 mA of current from a 1.5‐V supply voltage and achieves voltage gains of 14 and 22 dB, input S₁₁ of 15 and 18 dB, and noise figures of 2.45 and 2.51 dB at 2.4 and 5.2 GHz, respectively. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

Simulation of noise figure of nonlinear amplifiers using the orthogonalization of the nonlinear model

A simulation procedure of noise figure (NF) of nonlinear amplifiers is developed. NF is defined in terms of the effective signal‐to‐noise ratio (SNR) at the output of a nonlinear amplifier. The effective output SNR when the input consists of a communication signal plus Gaussian noise is evaluated through the identification of the effective output noise and nonlinear distortion power using the orthogonalization of the nonlinear model. The approach is useful for the assessment of noise performance of low‐noise amplifiers in wireless systems. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE 2009.     

On techniques for optimal noise matching of a class of multimode antenna

This article investigates techniques to design noise‐matching networks for a class of multimodal antennas, specifically, the so‐called quad‐mode antenna. Such an antenna utilizes weighted combinations of four very dissimilar radiation patterns, and different modal input impedances, which vary across scan angle. The matching problem is therefore quite different from that of a classical array, where antenna elements are normally assumed to be similar. In addition to the standard techniques, a new, recursively averaged active impedance, is proposed and applied, as well one using a noise‐active impedance, and two optimization approaches. It is shown for the first time that the quad‐mode antenna displays excellent noise properties, with the simplest technique, namely that of matching to the self‐impedances, producing noise performances across all scan angles which are almost as good as the best solution found by all the techniques.     

Passivity‐based asymptotic stabilization for switched nonlinear systems using the sampled integral stabilization technique

The asymptotic stabilization problem is studied for a cascade connection of passive switched nonlinear systems and a passive switched nonlinear system in this paper. When each subsystem is asymptotically zero state detectable and passive on active time intervals, asymptotic stabilization is achieved via co‐design of switching laws and controllers without damping injection. First, an output‐feedback controller is designed to asymptotically stabilize a cascade connection of two passive switched systems if outputs are measurable. Second, when the output of the first switched system is noisy or unmeasurable, a sampled integral stabilization (SIS) technique is employed to investigate asymptotical stabilization of a cascade connection by measuring only the storage function of the second switched system. Finally, as a special case of a cascade connection, the SIS technique is used to stabilize a passive switched system without damping injection. Under this circumstance, the controller is designed by sampling the integral of the passive output. The two‐link robot manipulator is provided to illustrate the effectiveness of the SIS technique.     

A straightforward design technique for narrowband multi‐stage low‐noise amplifiers with I/O conjugate match

Low‐noise amplifier (LNA) designers often struggle to simultaneously satisfy gain, noise, stability, and I/O matching requirements. In this article, a novel design technique, tailored for two‐stage low‐noise amplifiers, is presented. The proposed design method is completely deterministic and exploits inductive source degeneration to obtain a two‐stage LNA featuring perfect input and output match together with low noise figure (NF) and a pre‐determined gain, including stability analysis. A novel flowchart is provided together with the corresponding design chart that contains gain, matching, and stability information, therefore addressing all key figures‐of‐merit of a linear amplifier. The design chart is easily implementable in commercial Electronic Design Automation software, to aid designers in the difficult task of selecting the appropriate source degeneration inductor value. The noise performance, on the other hand, is the best possible since the matching networks are designed to provide the input of the two Field Effect Transistors with the optimum termination for noise. The design method is validated with two separate test vehicles operating respectively at Ka‐band (26.5‐31.5 GHz) and K‐band (20.0‐24.0 GHz). The realized Monolithic Microwave Integrated Circuits exhibit 18 dB gain for both versions, NF of 1.5 and 1.2 dB, respectively for the Ka‐band and K‐band version. Input and output matching are typically better than 12 and 15 dB.