Analysis and Design of a Phase-Tunable Source Injection-Coupled LC Quadrature Oscillator

This paper presents the design and analysis of phase-tunable injection-coupled quadrature oscillator (PT-IC-QO). Like other LC QOs, the mismatches between LC tanks are the main source of phase error in this oscillator. Using tail current in network coupling is novel approach to design new IC-QO. One of the advantages using added extra tail current in coupling network is control of coupling factor and also that it drastically reduces supply noise over classic IC-QO. Analysis and simulation result show that phase error can be controlled and cancelled simply by using tunable tail current in network coupling while that is difficultly controlled in the previse work. The basic idea of the presented design to reduce phase error due to tank mismatches is its compensation with an intentional mismatch between \(I\hbox {/}Q\)-side injection current. Based on the equations, a new tunable source-injected QO is proposed which is able to cancel the phase errors up to \(\pm 20^\circ \), without undesirable impact on phase noise. To evaluate the proposed analysis and consequent designed quadrature oscillator, a 5.4-GHz CMOS PT-QO is designed and simulated using the practical \(0.18\,\upmu \hbox {m}\) TSMC CMOS technology.     

RF Power Amplifier Behavioral Modeling Based on Takenaka–Malmquist–Volterra Series

In this paper, a Takenaka–Malmquist–Volterra (TMV) model structure is employed to improve the approximations in the low-pass equivalent behavioral modeling of radio frequency (RF) power amplifiers (PAs). The Takenaka–Malmquist basis generalizes the orthonormal basis functions previously used in this context. In addition, it allows each nonlinearity order in the expanded Volterra model to be parameterized by multiple complex poles (dynamics). The state-space realizations for the TMV models are introduced. The pole sets for the TMV model and also for the previous Laguerre–Volterra (LV) and Kautz–Volterra (KV) models are obtained using a constrained nonlinear optimization approach. Based on experimental data measured on a GaN HEMT class AB RF PA excited by a WCDMA signal, it is observed that the TMV model reduces the normalized mean-square error and the adjacent channel error power ratio for the upper adjacent channel (upper ACEPR) by 1.6 dB when it is compared to the previous LV and KV models under the same computational complexity.     

A Low-Voltage Fully Differential Pure Current Mode Current Operational Amplifier

In this paper a novel high-frequency fully differential pure current mode current operational amplifier (COA) is proposed that is, to the authors’ knowledge, the first pure MOSFET Current Mode Logic (MCML) COA in the world, so far. Doing fully current mode signal processing and avoiding high impedance nodes in the signal path grant the proposed COA such outstanding properties as high current gain, broad bandwidth, and low voltage and low-power consumption. The principle operation of the block is discussed and its outstanding properties are verified by HSPICE simulations using TSMC \(0.18\,\upmu \hbox {m}\) CMOS technology parameters. Pre-layout and Post-layout both plus Monte Carlo simulations are performed under supply voltages of \(\pm 0.75\,\hbox {V}\) to investigate its robust performance at the presence of fabrication non-idealities. The pre-layout plus Monte Carlo results are as; 93 dB current gain, \(8.2\,\hbox {MHz}\,\, f_{-3\,\text {dB}}, 89^{\circ }\) phase margin, 137 dB CMRR, 13 \(\Omega \) input impedance, \(89\,\hbox {M}\Omega \) output impedance and 1.37 mW consumed power. Also post-layout plus Monte Carlo simulation results (that are generally believed to be as reliable and practical as are measuring ones) are extracted that favorably show(in abovementioned order of pre-layout) 88 dB current gain, \(6.9\,\hbox {MHz} f_{-3\text {db}} , 131^{\circ }\) phase margin and 96 dB CMRR, \(22\,\Omega \) input impedance, \(33\,\hbox {M}\Omega \) output impedance and only 1.43 mW consumed power. These results altogether prove both excellent quality and well resistance of the proposed COA against technology and fabrication non-idealities.     

Global Robust Sliding Mode Control for Time-Delay Systems with Mismatched Uncertainties

A novel robust sliding mode control method for time-delay systems with mismatched uncertainties is presented, taking into consideration of both the norm-bounded mismatched uncertainties in the input matrix and the unknown input disturbance. First of all, an original time-delay system is changed into a new form without time delay via a nonsingular transformation, based on which, an integral sliding mode controller is then designed in the form of linear matrix inequalities, to guarantee the existence of the sliding motion from the initial time. In order to estimate the upper bound of unknown input disturbance, a new adaptive law is also proposed. Finally, a numerical simulation case is given to show the effectiveness of the proposed method.     

Adaptive Fuzzy Output-Feedback Control for Switched Nonlinear Systems with Arbitrary Switchings

This paper investigates the adaptive fuzzy output-feedback control problem for single-input and single-output switched uncertain nonlinear systems. The addressed systems in this paper have the characteristics of arbitrary switchings, unknown nonlinear dynamics and immeasurable states. A common state observer is designed independent of switching signals. Fuzzy logic systems are utilized to approximate unknown lumped nonlinear dynamics. Based on the framework of backstepping design technique, an adaptive fuzzy output-feedback control scheme is developed. By using the common Lyapunov function theory, the stability of the closed-loop system is proved. The proposed control scheme does not need the assumptions that the states of the controlled system are available for measurement and that the switching signals satisfy the average dwell time. Moreover, it can guarantee that all the closed-loop signals are bounded, and the system output eventually converges to a small neighborhood of the origin. Finally, simulation studies are provided to further check the effectiveness of the proposed control scheme.     

Approximated Fractional-Order Inverse Chebyshev Lowpass Filters

In this paper we use a least-squares fitting routine to approximate the stopband ripple characteristics of fractional-order inverse Chebyshev lowpass filters which have fractional-order zeros and poles. MATLAB simulations of \((1+\alpha )\)-order lowpass filters with fractional steps from \(\alpha =0.1\) to \(\alpha =0.9\) are given as examples. SPICE simulations of 1.2-, 1.5-, and 1.8-order lowpass filters and experimental results of a 1.5-order filter using approximated fractional-order capacitors in a Multiple-Input Biquad circuit validate the implementation of these circuits.     

Asymptotic Stability Conditions and Estimates of Solutions for Nonlinear Multiconnected Time-Delay Systems

This paper examines certain classes of multiconnected (complex) systems with time-varying delay. Delay-independent stability conditions and estimates of the convergence rate of solutions to the origin for those systems are derived. It is shown that the exponents in the obtained estimates depend on the parameters of Lyapunov functions constructed for the corresponding isolated subsystems. The problem of computing parameter values that provide the most precise estimates is investigated. Some examples are presented to demonstrate the effectiveness of the proposed approaches.     

Fault-Tolerant Control for Markovian Jump Delay Systems with an Adaptive Observer Approach

This paper investigates the problem of fault estimation and fault-tolerant control for a class of Markovian jump systems with mode-dependent interval time-varying delay and Lipschitz nonlinearities. In this paper, a new adaptive fault observer is designed to solve the problem of fault estimation. The proposed observer can estimate the states and faults simultaneously, whether faults are of time-varying or constant characterization. Based on the fault estimation, a fault-tolerant controller is designed to stabilize the closed-loop system. Sufficient conditions for the existence of the observer gain and fault-tolerant controller gain are got by a set of linear matrix inequalities. Finally, a numerical example is presented to illustrate the effectiveness of the proposed fault-tolerant control method.     

Toward a Game Theoretic View of Secure Computation

We demonstrate how Game Theoretic concepts and formalism can be used to capture cryptographic notions of security. In the restricted but indicative case of two-party protocols in the face of malicious fail-stop faults, we first show how the traditional notions of secrecy and correctness of protocols can be captured as properties of Nash equilibria in games for rational players. Next, we concentrate on fairness. Here we demonstrate a Game Theoretic notion and two different cryptographic notions that turn out to all be equivalent. In addition, we provide a simulation-based notion that implies the previous three. All four notions are weaker than existing cryptographic notions of fairness. In particular, we show that they can be met in some natural setting where existing notions of fairness are provably impossible to achieve.     

MFLP: a low power encoding for on chip networks

Network on chip (NoC) has been proposed as an appropriate solution for today’s on-chip communication challenges. Power dissipation has become a key factor in the NoCs because of their shrinking sizes. In this paper, we propose a new encoding approach aimed at power reduction by decreasing the number of switching activities on the buses. This approach assigns the symbols to data word in such a way that the more frequent words are sent by less power consumption. This algorithm dedicates the symbols with less ones to high probability data and uses transition signaling to transmit data. The proposed method, unlike the existing low power encoding, does not rely on spatial redundancy and keeps the width of the bus constant. Experimental evaluations show that our approach reduces the power dissipation up to 46 % with 2.70, 0.51, and 15.43 % power, critical path and area overhead in the NoCs, respectively.