Showing papers in "Circuits Systems and Signal Processing in 2013"

Optimization of Fractional-Order RLC Filters

Abstract: This paper introduces some generalized fundamentals for fractional-order RL β C α circuits as well as a gradient-based optimization technique in the frequency domain. One of the main advantages of the fractional-order design is that it increases the flexibility and degrees of freedom by means of the fractional parameters, which provide new fundamentals and can be used for better interpretation or best fit matching with experimental results. An analysis of the real and imaginary components, the magnitude and phase responses, and the sensitivity must be performed to obtain an optimal design. Also new fundamentals, which do not exist in conventional RLC circuits, are introduced. Using the gradient-based optimization technique with the extra degrees of freedom, several inverse problems in filter design are introduced. The concepts introduced in this paper have been verified by analytical, numerical, and PSpice simulations with different examples, showing a perfect matching.

A Design Example of a Fractional-Order Kerwin–Huelsman–Newcomb Biquad Filter with Two Fractional Capacitors of Different Order

Abstract: Design, realization and performance studies of continuous-time fractional order Kerwin–Huelsman–Newcomb (KHN) biquad filters have been presented. The filters are constructed using two fractional order capacitors (FC) of orders α and β (0<α, β≤1). The frequency responses of the filters, obtained experimentally have been compared with simulated results using MATLAB/SIMULINK and also with PSpice (Cadence PSD 14.2), where the fractional order capacitor is approximated by a domino ladder circuit. It has been observed that fractional order filters can give better performance in certain aspects compared to integer order filters. The effects of the exponents (α and β) on bandwidth and stability of the realized filter have been examined. Sensitivity analysis of the realized fractional order filter has also been carried out to investigate the deviation of the performance due to the parameter variation.

A Novel Color Image Segmentation Approach Based on Neutrosophic Set and Modified Fuzzy c-Means

Abstract: Color image segmentation is an important technique in image processing, pattern recognition and computer vision. Many segmentation algorithms have been proposed. However, it is still a complex task especially when there are noises in the images, which have not been studied in much detail. Neutrosophic set (NS) studies the origin, nature, and scope of neutralities. In this paper, we apply NS in the color image and define some new concepts. A directional α-mean operation is proposed to reduce the set indeterminacy. The fuzzy c-means clustering method is improved by integrating with NS and employed for the color image segmentation. The computation of membership and the clustering termination criterion are redefined accordingly. Moreover, a validity criterion is employed to determine the optimal clustering number. Numerical experiments serve to illustrate the effectiveness and reliability of the proposed approach. Experimental results demonstrate that our approach can segment color images automatically and effectively, produce good results as favorably compared to some existing algorithms. The optimal clustering number is determined automatically and no prior knowledge is required. Especially, it can segment both images with the simple and distinct objects and the images with complex and noisy objects, which is the most difficult task for color image segmentation.

Exponential Stability of Switched Systems with Unstable Subsystems: A Mode-Dependent Average Dwell Time Approach

Abstract: This article studies the exponential stability of switched systems with unstable subsystems. By using the multiple Lyapunov function (MLF) method combined with mode-dependent average dwell time (MDADT) techniques, less conservative exponential stability conditions are derived in terms of a set of solvable linear matrix inequalities (LMIs). Compared to the existing results, unstable subsystems are considered based on MDADT in this paper. It is revealed that switched systems can be exponentially stable under slow switching schemes and also in the presence of fast switching of unstable subsystems. A numerical example and its simulations are also given to verify the effectiveness of the proposed method.

Performance Analysis of the Auxiliary Model-Based Stochastic Gradient Parameter Estimation Algorithm for State-Space Systems with One-Step State Delay

Abstract: How to use the observation data to build the mathematical models of time-delay systems and how to estimate the parameters of the obtained models are important for studying the laws of motion of systems. This paper presents an auxiliary model-based stochastic gradient parameter estimation algorithm and studies its convergence for the input–output representation for state-space systems with one-step delays, by means of the auxiliary model identification idea. The simulation results indicate that the proposed algorithm can effectively estimate the parameters of the systems.

Stability Analysis and Stabilization of Discrete-Time 2D Switched Systems

Abstract: This paper is concerned with stability analysis and stabilization problems for two-dimensional (2D) discrete switched systems represented by a model of Roesser type. First, sufficient conditions for the exponential stability of the 2D discrete switched system are derived via the average dwell time approach. Then, based on this result, a state feedback controller is designed to achieve the exponential stability of the corresponding closed-loop system. All the results are presented in linear matrix inequalities (LMIs) form. A numerical example is given to illustrate the effectiveness of the proposed method.

Diagnostics of Analog Circuits Based on LS-SVM Using Time-Domain Features

Abstract: Most researchers use wavelet transforms to extract features from a time-domain transient response from analog circuits to train classifiers such as neural networks (NNs) and support vector machines (SVMs) for analog circuit diagnostics. In this paper, we have proposed some new feature selection methods from a time-domain transient response, and compared the diagnostic results based on a least squares SVM (LS-SVM) using different time-domain feature vectors. First, we have improved two traditional feature selection methods: (a) using the mean and standard deviation in wavelet transform features, and (b) using the mean, standard deviation, skewness, kurtosis, and entropy in statistical property features. Then, a conventional time-domain feature vector based on the impulse response properties of a control system has been proposed. The simulation experiments for a leapfrog filter and a nonlinear rectifier show that: (1) the two improved methods have better accuracy than the traditional methods; (2) the proposed conventional time-domain feature vector is effective in the diagnostics of analog circuits—over 99 % for both of the two example circuits; (3) the proposed diagnostic method can diagnose soft faults, hard faults, and multi-faults, regardless of component tolerances and nonlinearity effects.

Electronically Tunable Single-Input Five-Output Voltage-Mode Universal Filter Using VDTAs and Grounded Passive Elements

Abstract: This paper presents a possible usage of the voltage differencing transconductance amplifier (VDTA) for the design of an electronically tunable single-input five-output voltage-mode universal filter. The presented filter is constructed using two VDTAs, two capacitors and two resistors that are all grounded. The circuit simultaneously realizes lowpass (LP), bandpass (BP), highpass (HP), bandstop (BS) and allpass (AP) filtering responses, without changing the circuit topology. The circuit is capable of providing an independent electronic control of the natural angular frequency (ω 0) and the quality factor (Q) through the transconductance gains of the VDTAs. By simply adjusting the transconductance ratio, a high-Q filter can also be obtained. Because of the high-input impedance of the circuit, it is advantageous for cascade connection. To support the theoretical analysis, the properties of the designed filter have been verified by PSPICE simulation results.

Observer Design of Switched Positive Systems with Time-Varying Delays

Abstract: This paper is concerned with the design of positive observers for switched positive linear systems with time-varying delays. Attention is focused on designing the positive observers such that the error switched systems are exponentially stable. Based on the average dwell time approach, sufficient conditions, which ensure the estimated error exponentially converges to zero, are formulated in a set of linear matrix inequalities (LMIs). Finally, an illustrative example is given to show the efficiency of the proposed method.

Low-Noise Low-Pass Filter for ECG Portable Detection Systems with Digitally Programmable Range

Abstract: This paper presents the design of an operational transconductance amplifier-C (OTA-C) low-pass filter for a portable Electrocardiogram (ECG) detection system. A fifth-order Butterworth filter using ladder topology is utilized to reduce the effect of component tolerance and to provide a maximally flat response. The proposed filter is based on a novel class AB digitally programmable fully differential OTA circuit. Based on this, PSPICE simulation results for the filter using 0.25-μm technology and operating under ±0.8 V voltage supply are also given. The filter provides a third harmonic distortion (HD3) of 53.5 dB for 100 mV p-p @50 Hz sinusoidal input, input referred noise spectral density of , total power consumption of 30 μW, and a bandwidth of 243 Hz. These results demonstrate the ability of the filter to be used for ECG signal filtering that is located within 150 Hz.

Edge Effect Elimination in Single-Mixture Blind Source Separation

Abstract: Blind source separation (BSS) of single-channel mixed recording is a challenging task that has applications in the fields of speech, audio and bio-signal processing. Ensemble empirical mode decomposition (EEMD)-based methods are commonly used for blind separation of single input multiple outputs. However, all of these EEMD-based methods appear in the edge effect problem when cubic spline interpolation is used to fit the upper and lower envelopes of the given signals. It is therefore imperative to have good methods to explore a more suitable design choice, which can avoid the problems mentioned above as much as possible. In this paper we present a novel single-mixture blind source separation method based on edge effect elimination of EEMD, principal component analysis (PCA) and independent component analysis (ICA). EEMD represents any time-domain signal as the sum of a finite set of oscillatory components called intrinsic mode functions (IMFs). In extreme point symmetry extension (EPSE), optimum values of endpoints are obtained by minimizing the deviation evaluation function of signal and signal envelope. Edge effect is turned away from signal by abandoning both ends’ extension parts of IMFs. PCA is applied to reduce dimensions of IMFs. ICA finds the independent components by maximizing the statistical independence of the dimensionality reduction of IMFs. The separated performance of edge EPSE-EEMD-PCA-ICA algorithm is compared with EEMD-ICA and EEMD-PCA-ICA algorithms through simulations, and experimental results show that the former algorithm outperforms the two latter algorithms with higher correlation coefficient and lower relative root mean square error (RRMSE).

A Security Framework for NoC Using Authenticated Encryption and Session Keys

Abstract: Network on Chip (NoC) is an emerging solution to the existing scalability problems with System on Chip (SoC). However, it is exposed to security threats like extraction of secret information from IP cores. In this paper we present an Authenticated Encryption (AE)-based security framework for NoC based systems. The security framework resides in Network Interface (NI) of every IP core allowing secure communication among such IP cores. The secure cores can communicate using permanent keys whereas temporary session keys are used for communication between secure and non-secure cores. A traffic limiting counter is used to prevent bandwidth denial and access rights table avoids unauthorized memory accesses. We simulated and implemented our framework using Verilog/VHDL modules on top of NoCem emulator. The results showed tolerable area overhead and did not affect the network performance apart from some initial latency.

An Adaptive Clipping and Filtering Technique for PAPR Reduction of OFDM Signals

Abstract: In recent years, many peak-to-average power ratio (PAPR) reduction techniques have been proposed for orthogonal frequency division multiplexing (OFDM) signals. Among various techniques, the iterative clipping and filtering (ICAF) technique has been considered as a practical scheme, and widely used owing to its non-expansion of bandwidth, low computational complexity, and simplicity in implementation without receiver-side cooperation. However, the performance of conventional ICAF technique is degraded, because the same signals are iteratively clipped with a fixed clipping threshold (CT) in every clipping operation. In this paper, we analyze the performance of conventional ICAF technique, and then propose an adaptive ICAF scheme, which clips the signal with an adaptively modified CT in every clipping operation to achieve enhanced PAPR reduction of OFDM signals. Simulation results show that the proposed scheme significantly outperforms the conventional scheme, in PAPR reduction of OFDM signals at the same number of iterations.

Multichannel Sampling of Signals Band-Limited in Offset Linear Canonical Transform Domains

Abstract: The aim of the multichannel sampling is the reconstruction of a band-limited signal f(t), from the samples of the responses of M linear time invariant systems, each sampled by the 1/Mth Nyquist rate. As the offset linear canonical transform (OLCT) has been found wide applications in signal processing and optics fields, it is necessary to consider the multichannel sampling based on offset linear canonical transform. In this paper, we develop a multichannel sampling theorem for signals band-limited in offset linear canonical transform domains. Moreover, by designing different OLCT filters, reconstruction formulas for uniform sampling from the signal, from the signal and its first derivative or its generalized Hilbert transform are obtained based on the derived multichannel sampling theorem. Since recurrent nonuniform sampling for the signal has valuable applications, reconstruction expression for recurrent nonuniform samples of the signal band-limited in the offset linear canonical transform domain is also obtained by using the derived multichannel sampling theorem and the properties of the offset linear canonical transform.

On a Non-homogeneous Singular Linear Discrete Time System with a Singular Matrix Pencil

Abstract: In this article, we study the initial value problem of a non-homogeneous singular linear discrete time system whose coefficients are either non-square constant matrices or square with an identically zero matrix pencil. By taking into consideration that the relevant pencil is singular, we provide necessary and sufficient conditions for existence and uniqueness of solutions. More analytically we study the conditions under which the system has unique, infinite and no solutions. Furthermore, we provide a formula for the case of the unique solution. Finally we provide some numerical examples based on a singular discrete time real dynamical system to justify our theory.

Steady-State MSE Performance of the Set-Membership Affine Projection Algorithm

Abstract: The set-membership affine projection (SM-AP) algorithm has many desirable characteristics such as fast convergence speed, low power consumption due to data-selective updates, and low misadjustment. The main reason hindering the widespread use of the SM-AP algorithm is the lack of analytical results related to its steady-state performance. In order to bridge this gap, this paper presents an analysis of the steady-state mean square error (MSE) of a general form of the SM-AP algorithm. The proposed analysis results in closed-form expressions for the excess MSE and misadjustment of the SM-AP algorithm, which are also applicable to many other algorithms. This work also provides guidelines for the analysis of the whole family of SM-AP algorithms. The analysis relies on the energy conservation method and has the attractive feature of not assuming a specific model for the input signal. In addition, the choice of the upper bound for the error of the SM-AP algorithm is addressed for the first time. Simulation results corroborate the accuracy of the proposed analysis.

Delay-Dependent Stability for Discrete 2D Switched Systems with State Delays in the Roesser Model

Abstract: This paper is concerned with the problem of delay-dependent stability analysis for a class of two-dimensional (2D) discrete switched systems described by the Roesser model with state delays. First, the concept of average dwell time is extended to 2D switched systems with state delays. Then, based on the average dwell time approach, a delay-dependent sufficient condition for the exponential stability of the addressed systems is derived. All the results are formulated in terms of linear matrix inequalities (LMIs), which can be solved efficiently. A numerical example is given to illustrate the effectiveness of the proposed method.

Improved Delay-Dependent Stability Criteria for Discrete-Time Systems with Time-Varying Delays

Abstract: This paper considers the stability problem for discrete-time systems with interval time-varying delays. By construction of a suitable Lyapunov–Krasovskii (L–K) functional and utilization of Finsler’s lemma, novel delay-dependent criteria for asymptotic stability of the systems are established in terms of linear matrix inequalities (LMIs) which can easily be solved by various effective optimization algorithms. Three numerical examples are given to illustrate the effectiveness of the proposed method.

On the Realization of MOS-Only Allpass Filters

Abstract: The objective of this paper is to present a simple filter topology, which can be used to implement first- and second-order MOS-only allpass filters. The resulting filters realize the allpass functions without using any external passive components; hence these occupy very small chip area and are capable of operating at high frequencies. Cadence Spectre simulation and experimental results verifying the main advantages of the filters are provided.

Stabilization of Discrete-Time Positive Switched Systems

Abstract: This paper addresses the stabilization for a class of discrete-time positive switched systems. Based on the average dwell time switching strategy, the stabilization of the underlying systems in the autonomous form is studied. Further, the control synthesis of non-autonomous systems is discussed. The state-feedback and output-feedback controllers are constructed, respectively. All the present conditions are solvable in terms of linear programming. Finally, four simulation examples illustrate the validity of the design.

Delay-Dependent Stabilizability of 2D Delayed Continuous Systems with Saturating Control

Abstract: This paper deals with the problem of stability and stabilization of 2D delayed continuous systems with saturation on the control. An improved delay-dependent stability condition taken from the recent literature is first extended to the case of 2D systems. Second, a delay-dependent stabilizability condition is deduced. The synthesis of stabilizing saturating state feedback controllers for such systems is then given. A set of allowed delays for both directions of the state is computed. All involved conditions are given under LMI formalism. Examples are worked to show the effectiveness of the approach.

Application of Memristor-Based Controller for Loop Filter Design in Charge-Pump Phase-Locked Loops

Abstract: In this work, a monotonic increasing piecewise-linear (PWL) memristor-based proportional-integral (PI) controller is analyzed. A periodic rectangular pulse current source is used as the input signal, and the proportionality constant of the PWL memristor-based PI controller is varied according to the amount of charge that passes through the memristor. A circuit is proposed to achieve zero net-charge injection for the memristor so that the memristance of the PWL memristor can be varied in the subsequent period. The proposed PWL memristor-based PI controller can be used in the design of the loop filter for the charge-pump phase-locked loop for achieving a faster dynamical response from an unlocked state to a locked state compared to conventional fixed proportional constant PI controllers.

Exponential l2–l∞ Control for Discrete-Time Switching Markov Jump Linear Systems

Abstract: The problem of exponential l 2–l ∞ control is considered in this paper for a class of discrete-time switching Markov jump linear systems. First, the definition of exponential l 2–l ∞ mean square stability for discrete-time switching Markov jump linear systems is introduced. Then, by resorting to the average dwell time approach, the mean square exponential stability criteria are presented with an exponential l 2–l ∞ performance index and a decay rate, and the corresponding controller is also designed. Finally, numerical and application examples are provided to demonstrate the effectiveness of the obtained results.

Numeric Variable Forgetting Factor RLS Algorithm for Second-Order Volterra Filtering

Abstract: Nonlinear adaptive filtering techniques for system identification (based on the Volterra model) are widely used for the identification of nonlinearities in many applications. In this correspondence, the improved tracking capability of a numeric variable forgetting factor recursive least squares (NVFF-RLS) algorithm is presented for first-order and second-order time-varying Volterra systems under a nonstationary environment. The nonlinear system tracking problem is converted into a state estimation problem of the time-variant system. The time-varying Volterra kernels are governed by the first-order Gauss–Markov stochastic difference equation, upon which the state-space representation of this system is built. In comparison to the conventional fixed forgetting factor recursive least squares algorithm, the NVFF-RLS algorithm provides better channel estimation as well as channel tracking performance in terms of the minimum mean square error (MMSE) for first-order and second-order Volterra systems. The NVFF-RLS algorithm is adapted to the time-varying signals by using the updating prediction error criterion, which accounts for the nonstationarity of the signal. The demonstrated simulation results manifest that the proposed method has good adaptability in the time-varying environment, and it also reduces the computational complexity.

A Novel Resistor-Free Electronically Adjustable Current-Mode Instrumentation Amplifier

Abstract: In this paper, a novel topology for implementing resistor-free current-mode instrumentation amplifier (CMIA) is presented. Unlike the other previously reported instrumentation amplifiers (IAs), in which input and/or output signals are in voltage domain, the input and output signals in the proposed structure are current signals and signal processing is also completely done in current domain benefiting from the full advantages of current-mode signal processing. Interestingly the CMRR of the proposed topology is wholly determined by only five transistors. Compared to the most of the previously reported IAs in which at least two active elements are used to attain high common-mode rejection ratio (CMRR) resulting in a complicated circuit, the proposed structure enjoys from an extremely simple circuit. It also exhibits low input impedance employing negative feedback principal. Of more interest is that, using simple degenerate current mirrors, the differential-mode gain of the proposed CMIA can be electronically varied by control voltage. This property makes it completely free of resistors. The very low number of transistors used in the structure of the proposed CMIA grants it such desirable properties as low-voltage low-power operation, suitability for integration, wide bandwidth etc. SPICE simulation results using the TSMC 0.18-μm CMOS process model under supply voltage of ±0.8 V show a high CMRR of 91 dB and a low input impedance of 291.5 Ω for the proposed CMIA. Temperature simulation results are also provided, which prove low temperature sensitivity of the proposed CMIA.

A Reconfigurable Low-Noise Amplifier Using a Tunable Active Inductor for Multistandard Receivers

Abstract: A reconfigurable low-noise amplifier (LNA) based on a high-value active inductor (AI) is presented in this paper. Instead of using a passive on-chip inductor, a high-value on-chip inductor with a wide tuning range is used in this circuit and results in a decrease in the physical silicon area when compared to a passive inductor-based implementation. The LNA is a common source cascade amplifier with RC feedback. A tunable active inductor is used as the amplifier output load, and for input and output impedance matching, a source follower with an RC network is used to provide a 50 Ω impedance. The amplifier circuit has been designed in 0.18 µm CMOS process and simulated using the Cadence Spectra circuit simulator. The simulation results show a reconfigurable frequency from 0.8 to 2.5 GHz, and tuning of the frequency band is achieved by using a CMOS voltage controlled variable resistor. For a selected 1.5 GHz frequency band, simulation results show S 21 (Gain) of 22 dB, S 11 of −18 dB, S 22 of −16 dB, NF of 3.02 dB, and a minimum NF (NFmin) of 1.7 dB. Power dissipation is 19.6 mW using a 1.8 V dc power supply. The total LNA physical silicon area is (200×150) µm2.

Exponential H ∞ Output Tracking Control for Switched Neutral System with Time-Varying Delay and Nonlinear Perturbations

Abstract: In this paper, the problem of exponential H∞ output tracking control is addressed for a class of switched neutral system with time-varying delay and nonlinear perturbations. The considered system consists of different neutral and discrete delays. By resorting to the average dwell time approach, a new Lyapunov–Krasovskii functional is proposed to establish sufficient conditions for the exponential stability and H∞ performance of switched neutral systems. Then, the problem of exponential H∞ output tracking control is investigated, an explicit expression for the desired exponential tracking controller is also given. Finally, a numerical example is provided to demonstrate the potential effectiveness of the proposed method.

A Low Voltage and Low Power Current-Mode Analog Computational Circuit

Abstract: A new current-mode analog computational circuit is presented. The circuit can be digitally controlled to produce multiplying, squaring and inverse functions. The design is based on using MOSFETs operating in sub-threshold region to achieve ultra low power dissipation. The circuit is operated from a ±0.75 V DC supply. The proposed circuit has been simulated using Tanner in 0.35-μm TSMC CMOS process. Simulation results confirm the functionality of the circuit. The total power consumption is 2.3 μW, total harmonic distortion is 1.1 %, maximum linearity error is 0.3 % and the bandwidth is 2.3 MHz.

Event-Triggered Control for Linear Descriptor Systems

Abstract: In this paper, event-triggered strategies for linear descriptor systems are presented. By studying the descriptor system in terms of the second equivalent form and employing the Lyapunov theory and linear matrix inequality (LMI) approach, the control law and event-triggered condition guaranteeing the admissible behavior of the descriptor system are proposed. Furthermore, we prove that the inter-sampling times are strictly positive in the proposed event-triggered condition. Finally, a simulation example is given to illustrate the efficiency of the results.

H∞ Synchronization of Directed Complex Dynamical Networks with Mixed Time-Delays and Switching Structures

Abstract: This paper is concerned with the H ∞ synchronization problem of directed complex dynamical networks. For the system under study, mixed time-delays and stochastic factors are taken into consideration. By stochastic analysis techniques, we establish sufficient conditions under which the network is synchronized to the prescribed system in the H ∞ sense. Moreover, the effect of exogenous disturbance on synchronization performance is reduced to a given H ∞ norm. Finally, numerical simulations are given to verify the usefulness and effectiveness of our results.