High Frequency Gain Research Articles

Adaptive output‐feedback stabilisation of an uncertain second‐order linear systems

SummaryThe adaptive stabilisation of uncertain second‐order linear systems is addressed, under a lack of information from both states and parameters. The only standard assumptions are no zeros and the sign of the high frequency gain known. To the best of the authors' knowledge, there has been only an explicit solution proposed in the literature so far with proven stability. Despite the simplicity of the system, it does not fit in any of the standard nonlinear control methodologies available. Thus, this work is a complementary contribution providing a mixed control design strategy based on a reduced‐order observer, adaptive Immersion & Invariance and Backstepping approaches. Hence, this solution depicts a transversal outlook of those nonlinear control strategies and provides a breakthrough for the generalisation of this non‐trivial control problem. Numerical simulations are reported to assess the effectiveness of the adaptive strategy. Copyright © 2016 John Wiley & Sons, Ltd.

A New Control Structure for Multiterminal DC Grids to Damp Interarea Oscillations

This paper analyzes the control structure of the multiterminal dc (MTDC) system to damp ac system interarea oscillations through active power modulation. A new control structure is presented that maximizes the relative controllability without the need for communication among the dc terminals. In point-to-point high-voltage dc (HVDC) transmission, the active power modulation of the two terminals occurs in opposite directions. In this case, the control direction is given and only needs to be phase compensated to align for maximal damping. In the case of MTDC systems, the control direction interrelates with the active power modulation share of the dc terminals and the relative controllability depends on this. The new control structure eliminates the need for communication between the dc terminals by performing dc voltage feedback loop shaping. This makes it possible to modulate the power in one terminal and let the other terminals react on the dc voltage change. Through loop shaping, where the feedback gain varies in the frequency plane compared to the regular droop design, the control direction is aligned with the direction of highest relative controllability. Loop shaping takes place without influencing the high frequency or steady-state gain. Simulations in the Nordic32 test system show the validity of the proposed controller and its structure.

Chaotic dynamics of an optical phase locked loop having loop filter with high frequency gain

Nonlinear dynamics of optical phase locked loop (OPLL) in presence of loop delay, considering proportional plus integrating type loop filter (LF) has been studied. Analytical and numerical results show that with proper choice of frequency gain, chaos generated in the system due to loop delay can be suppressed. Also the loop performance can be improved, so that the loop can operate in stable locking condition for some higher values of additional loop delay compared to the loop with imperfect integrating type LF. From analytical results, it is possible to choose a suitable value of the high frequency gain and other system parameters for controlling nonlinear dynamics of the loop. Analytical predictions have been verified by solving the system equations numerically.

Global tracking for a class of uncertain nonlinear systems with unknown sign-switching control direction by output feedback

This paper addresses the design of a sliding mode controller for a class of high-order uncertain nonlinear plants with unmatched state-dependent nonlinearities and unknown sign of the high frequency gain, i.e., the control direction is assumed unknown. Differently from most previous studies, the control direction is allowed to switch its sign. We show that it is possible to obtain global exact tracking using only output-feedback by coupling a relay periodic switching function with a norm state observer. One significant advantage of the new scheme is its robustness and improved transient response under arbitrary changes of the control direction which have been theoretically demonstrated for jump variations and successfully tested by simulations. The proposed controller is also evaluated with a DC motor control experiment.

An 11.5 Gb/s 1/4th Baud-Rate CTLE and Two-Tap DFE With Boosted High Frequency Gain in 110-nm CMOS

As the data rate has been increased over 10 Gb/s with copper interconnect, the intersymbol interference (ISI) caused from the channel loss should be compensated. While a decision feedback equalizer (DFE), which is widely used in the receiver can compensate the ISI, its ability to enhance the signal-to-noise ratio (SNR) is limited especially for high frequency data patterns (alternating data patterns). Even a DFE with a large number of taps, which has powerful compensation capacity for ISI, can improve only limited amount of SNR. To improve SNR, this brief presents a 1/4th baud-rate continuous-time linear equalizer (CTLE) and a two-tap DFE. The 1/4th baud-rate CTLE recovers data to be adequate for the DFE, and remaining ISI is removed by the DFE. To boost the high frequency gain of the DFE, exclusive or merged adders are introduced, so the proposed equalizer is more tolerant against channel noise. It compensates 21.7-dB channel loss and operates with 11.5-Gb/s data rate as it consumes 25.35 mW from 1.3 V supply in a 110-nm CMOS technology.

Multi-Input Sliding Mode Control of Nonlinear Uncertain Non-Affine Systems With Mono-Directional Actuation

In this paper the multi-input Sliding Mode control of nonlinear uncertain non-affine systems with mono-directional actuators is considered. The geometric properties of the regular simplices of vectors are exploited by the mono-directional actuation system. The proposed full-state feedback control method introduces integrators in the input channel and suitably modifies the sliding output to be steered to zero. The resulting high frequency gain matrix (HFGM), which is the matrix multiplying the control vector, turns out to be affected by time and state dependent uncertainties. An effective use of the integral Sliding Mode method in connection with a non-conventional simplex based switching logic is introduced. The proposed simplex control procedure is adequately designed to avoid any possible unbounded increment of the control actions despite the presence of integrators in the input channel and the exploitation of mono-directional devices.

Ternary Gan Based HEMT for High Frequency Application

To achieve high performance in HEMT devices such as high power gain cut off frequency and high current gain cut off frequency and to get maximum drain current and transconductance. By using lattice matched quaternary barrier such as In AlGaN and re-growing the ohmic contacts in HEMT device. To reach high fmax we have to combine a low gate recess technology, scaled device geometry and recessed source and drain omhic contact to simultaneously enable minimum short channel effect. Short channel effect will lead to current leakage in the device. This effect can be suppressed with the help of barrier and back barrier.

The Effect of Viagra on Autonomic Function Using Spectral Analysis and Approximate Entropy Method

Objective: Autonomic nervous system involvement in patients with Erectile Dysfunction (ED) has shown conflicting results. Our main purpose was to assess the effect of treatment with Viagra on autonomic function of group of ED patients in comparison with another group with control subjects with ED treated by herbal substances by measuring the frequency gain response of the two groups. Other aim of this study was to determine wither the duration of Viagra treatment correlated with measures of heart rate variability signal (HRV) using approximate entropy index (ApEn). Methods: Twenty two patients treated for ED by Viagra (100 mg) and twenty one matched control subjects treated ED by herbal were evaluated at Erectile Dysfunction Center, Johns Hopkins Hospital, Maryland, USA during 2012/ 2013 by measuring the breathing at different rates and HRV signal derived from Electrocardiogram (ECG).The autopower and cross power spectra between HRV signal and breathing signal at different breathing rate were calculated and frequency gain response for both groups were obtained. ApEn described as measure of regularity of HRV was calculated for both patients with Viagra treatment and herbal treatment for control subjects. Results: Both frequencies gain response and ApEn measures were increased in patients treated with Viagra in comparison with control group. The power spectra of patients with Viagra men showed both increase High Frequency (HF) value and higher low frequency bands with respect to control subjects. On other hand, ApEn measure was significantly increased in longer Viagra taking duration than in herbal group. Conclusion: These findings suggest that the spectral analysis of HRV signal using breathing at different frequencies may detect balance of autonomic of autonomic system of ED patients treated with Viagra specially with increasing the sympathetic activity (higher low frequency) and as well as the parasympathetic tone(higher frequency gain response) which can lead to reduce sudden deaths in patients with treating with viagra. APEn may be marker related to duration of taking Viagra. Further studies are needed to include more patients to strengthen the quantitive and qualitative indices proposed in this paper.

A metamaterial antenna for WSN applications

ABSTRACTA miniaturized antenna is designed, analyzed, and fabricated for high‐speed wireless sensor networks, which operates at 2.4 GHz frequency. The miniaturization is achieved using metamaterial technique. In this technique, a patch antenna loaded with complementary rectangular split ring resonators and slots is proposed to provide metamaterial effect. The characteristics of designed structure are investigated using finite element method‐based Ansoft High Frequency Simulation Software and gain, return loss, bandwidth, and VSWR are calculated. Double negative existence is confirmed from the measurement results which show negative permeability and negative permittivity. Omnidirectional radiation pattern is obtained for 2.4 GHz frequency. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:120–124, 2015

Lyapunov Design of Multivariable MRAC via Generalized Passivation

AbstractA Lyapunov design of multiple input, multiple output (MIMO) model‐reference adaptive control (MRAC) systems is proposed using new generalized passivity concepts based on WSPR and WASPR properties. The new design avoids control overparameterization and leads to the simplest unnormalized gradient algorithm by means of a passivating multiplier. To this end, a necessary and sufficient condition on the high frequency gain matrix to achieve the WASPR property is established. This condition is referred to as Positive Diagonal Jordan (PDJ) form. Based on the robustness WSPR and WASPR properties, a systematic determination of a robust passivating matrix multiplier is then presented. The advantages of the new design are illustrated by numerical simulation including a robotics adaptive visual servoing problem and a 4‐input‐4‐output dynamic system. © 2014 Chinese Automatic Control Society and Wiley Publishing Asia Pty Ltd

DIRECT AND INDIRECT CLASSIFICATION OF HIGH FREQUENCY LNA GAIN PERFORMANCE – A COMPARISON BETWEEN SVMS AND MLPS

The task of determining low noise amplifier (LNA) high-frequency performance in functional testing is as challenging as designing the circuit itself due to the difficulties associated with bringing high frequency signals offchip. One possible strategy for circumventing these difficulties is to inferentially estimate the high frequency performance measures from measurements taken at lower, more accessible, frequencies. This paper investigates the effectiveness of this strategy for classifying the high frequency gain of the amplifier, a key LNA performance parameter. An indirect Multilayer Perceptron (MLP) and direct support vector machine (SVM) classification strategy are considered. Extensive Monte-Carlo simulations show promising results with both methods, with the indirect MLP classifiers marginally outperforming SVMs.

Multivariable MRAC Design Without Gain Symmetry Conditions Using a Stabilizing Multiplier

A new multivariable MRAC design for plants of arbitrary relative degree, which does not require a stringent symmetry assumption related with the plant high frequency gain matrix, is presented. In contrast to previous results, the new solution does not involve additional parametrization and filtering, being thus close in structure and complexity to conventional solutions. Instead of the fragile symmetry assumption, a less restrictive and robust condition is required, which can be achieved using a multiplier.

Beef Marbling Image Segmentation Based on Homomorphic Filtering

In order to reduce the influence of uneven illumination and reflect light for beef accurate segmentation, a beef marbling segmentation method based on homomorphic filtering was introduced. Aiming at the beef rib-eye region images in the frequency domain, homomorphic filter was used for enhancing gray, R, G and B 4 chroma images. Then the impact of high frequency /low frequency gain factors on the accuracy of beef marbling segmentation was investigated. Appropriate values of gain factors were determined by the error rate of beef marbling segmentation, and the results of error rate were analyzed comparing to the results without homomorphic filtering. The experimental results show that the error rates of beef marbling segmentation was remarkably reduced with low frequency gain factor of 0.6 and high frequency gain factor of 1.425; Compared with other chroma images, the average error rate (5.38%) of marbling segmentation in G chroma image was lowest; Compared to the result without homomorphic filtering, the average error rate in G chroma image has decreased by 3.73%.

Adaptive nonlinear output-feedback dynamic surface control with unknown high-frequency gain sign

In this paper, an adaptive dynamic surface control (DSC) for a class of nonlinear systems with unknown high-frequency gain (HFG) sign is proposed. The novelty of our scheme is that we separate the first virtual control signal from the HFG, which enables us to estimate the HFG directly. As a result, the traditional Nussbaum function (NF) approach is abandoned. By using the proposed DSC, the adaptive laws are needed only at the first design step and the explosion of terms in backstepping control can be eliminated, which greatly reduces the computational burden. In particular, based on an initialisation technique, we prove that the performance of the system tracking error can be guaranteed even when the HFG sign is unknown. It is shown that all signals of the closed-loop system are semi-globally uniformly bounded. Simulation results illustrate that the proposed scheme is more applicable than that of the NF-based backstepping control.

The Bang-Bang Funnel Controller for Uncertain Nonlinear Systems With Arbitrary Relative Degree

The paper considers output tracking control of uncertain nonlinear systems with arbitrary known relative degree and known sign of the high frequency gain. The tracking objective is formulated in terms of a time-varying bound-a funnel-around a given reference signal. The proposed controller is bang-bang with two control values. The controller switching logic handles arbitrarily high relative degree in an inductive manner with the help of auxiliary derivative funnels. We formulate a set of feasibility assumptions under which the controller maintains the tracking error within the funnel. Furthermore, we prove that under mild additional assumptions the considered system class satisfies these feasibility assumptions if the selected control values are sufficiently large in magnitude. Finally, we study the effect of time delays in the feedback loop and we are able to show that also in this case the proposed bang-bang funnel controller works under slightly adjusted feasibility assumptions.

A pre-distortion based design method for digital audio graphic equalizer

The traditional design method for digital audio graphic equalizer using infinite impulse response filters usually has some deficiencies, including center frequency shift, narrower bandwidth at high frequency and inaccurate gain. In this paper, an improved method based on the modified bilinear transformation is proposed to design a digital audio graphic equalizer. The new bilinear mapping can compensate the center frequency shift, and pre-distorting the quality factors and optimizing the gains can correct the bandwidth and gain of each sub-band respectively. Experimental results reveal that both center frequency and bandwidth of the proposed digital graphic equalizer are strictly equal to the desired ones, and the average gain error decreases at least 2 dB.

Adaptive Output Feedback Control of Multivariable Nonlinear Systems Based on Hurwitz Assumption

In this paper, global adaptive output feedback tracking problem is considered for a class of multivariable nonlinear systems with unknown parameters and nonlinear terms linear in unmeasured states. Based on a modified high-gain observer and Hurwitz assumption of high frequency gain matrix, an adaptive backstepping design is proposed, which is able to guarantee global stability of the closed-loop system and circumvent the over-parameterization problem raised by using conventional back stepping method.

Annoyance perception for hearing impaired listeners: A revisit

For hearing impaired (HI) listeners, it is well known that certain sounds are much more annoying than others even though they may have similar spectral shape and level. For example, HI listeners often report paper rustling noise as highly annoying. A common approach to deal with this complaint is to reduce high frequency gain. While this approach may mitigate the complaint, it can create audibility issues for speech. A more effective approach is to determine the underlying cause of annoyance and then design an algorithm to selectively reduce it. While existing literature on annoyance perception for HI listeners is scant, a previous attempt was made to investigate this perception using real-world recordings [Vishnubhotla et al. (2012)]. The study showed a large variability of annoyance ratings across listeners that may have been due to subjective associations with the sound sources. In this study, we use abstract psychoacoustic stimuli designed carefully to avoid possible confounding subjective associations. A magnitude estimation method was used to measure the annoyance of each stimulus in hearing impaired listeners. All stimuli were presented over headphones in a sound treated room. Results will be presented along with implications for hearing aid applications.

Multi-input sliding mode control of nonlinear uncertain non-affine systems with mono-directional actuation

In this paper the control of classes of nonlinear systems characterized by uncertain non-affine dependence on the control vector and controlled by mono-directional actuators is dealt with. We consider systems with mono-directional actuators and with state and time dependent uncertainties affecting the so-called High Frequency Gain Matrix (HFGM). We propose a switching logic based on a simplex of control vectors; the presented switching logic is effective in the case when the uncertain HFGM is time and state dependent with positive unknown, time and state dependent, eigenvalues. It is then introduced an integral sliding mode method which is able to cope with non-affine systems when the control is generated by a set of mono-directional actuators.

Research on Multivariable Model Reference Variable Structure Control

This paper studies the output-feedback variable structure control for MIMO (multi-input multi-output) linear systems with generalized relative degree one. A new variable structure control scheme is proposed within the framework of model reference control. Under the assumption that the high frequency gain matrix of the plant can be transformed to a main diagonal dominant matrix via full rank transformation, it is shown that all signals of the closed-loop system are globally uniformly bounded and meanwhile, the tracking error converges to zero exponentially. Simulation results are presented to illustrate the effectiveness of the proposed scheme.