Non-ideal Effects Research Articles

Double-Differential Amplifier for sEMG Measurement by Means of a Current-Mode Approach

This work proposes a Double Differential (DD) amplifier topology which exploits the advantages of the current-mode approach. DD amplifiers are useful as front-ends in standalone active electrodes for superficial electromyography (sEMG) wearable applications and electroneurography (ENG) measurement devices. Front-ends for these applications need to attain low noise, high common-mode rejection ratio, and high input impedance to measure biopotential signals and can further benefit from low power operation, a small size, and an easily adaptable output. Presently published DD amplifiers are either complex in terms of a high part count, leading to higher power consumption and size, or suffer from limited interference-rejection capabilities and require further analog processing for compatibility with single-ended systems. Therefore, in this work, second-generation current conveyors have been leveraged to obtain a simple topology combining a small active-part count, a high common-mode rejection ratio, and a flexible output stage. The current-mode DD amplifier is presented and analyzed in detail to estimate its parameters and model the effects of nonidealities in the circuit. In order to validate the proposed topology, a discrete-component implementation was realized as a proof-of-concept. The results experimentally demonstrated the properties of the proposed topology and its feasibility for measuring superficial sEMG DD signals.

General Approach to the Calibration of Innovative MFP Multichannel Digitizers

Innovative digitizers exploiting mixing, filtering, and processing (MFP) operations can grant ultrahigh bandwidth and sampling rate. Their operation combines analog processing stages with a digital signal processing stage, where massive operations are performed to obtain the digital representation of the input signal. In fact, the samples returned by the analog-to-digital converter (ADC) consist of a transformed, namely, mixed and filtered, version of the input, which shall be processed in the digital domain to reconstruct the input signal. The digital processing is also designed to attain streamline calibration, which provides both the removal of nonideal effects, such as mismatches between individual channels, and the improvement of the frequency response flatness. Calibration strategies represent an asset of manufacturers’ know-how since the performance of the digitizer largely depends on the effectiveness of the calibration process. Gain equalization and aliasing removal are performed in the digital domain by finite impulse response (FIR) filtering of the ADCs’ outputs. A general method for the identification of the calibration filters, and their translation into algorithms for MFP digitizers using two, four, or any number of channels, is proposed here. Functional- and circuit-level Cadence Virtuoso simulations in an STMicroelectronics Si–Ge heterojunction bipolar transistor (HBT) process are also carried out to evaluate the performance of the proposed method through a comparison between the digital representations of the signals obtained with and without calibration.

New full‐wave rectifier based on modified voltage differencing transconductance amplifier

A full-wave rectifier based on a modified voltage differencing transconductance amplifier-MVDTA and four n-MOS transistors (or inverting full-wave rectifier), with no use of any passive elements is proposed in this paper. The proposed design is suitable for a low voltage and high frequency input voltage/current signal. The used MVDTA possesses certain new connections without any changes in the original circuit resources of VDTA. The proposed configuration possesses satisfactory zero crossing performance, excellent linearity, low component count―a simple and compact structure―which makes it an adequate candidate for implementation in the form of IC circuits. The amplitude-waveform of the current/voltage rectified signal at the output of the proposed circuit can be electronically controlled by the applied bias currents. The influence of possible non-ideality and parasitic effects was analysed, while the effects of the parasitic are only marginal due to the absence of any passive elements. To verify the validity of the presented circuits, SPICE simulations deploying 0.18 μm CMOS technology parameters and supply voltage of ±0.9 V are reported, fully consistent with the theoretical predictions. The noise and Monte Carlo analyses were also performed in order to obtain further insight into the robustness of the proposed design. The proposal is also supported by experimental results in order to confirm the workability of the proposed solution.

Application of the Non-Enzymatic Glucose Sensor Combined with Microfluidic System and Calibration Readout Circuit

In this research, we proposed a potentiometric sensor based on copper doped zinc oxide (CZO) films to detect glucose. Silver nanowires were used to improve the sensor’s average sensitivity, and we used the low power consumption instrumentation amplifier (UGFPCIA) designed by our research group to measure the sensing characteristics of the sensor. It was proved that the sensor performs better when using this system. In order to observe the stability of the sensor, we also studied the influence of two kinds of non-ideal effects on the sensor, such as the drift effect and the hysteresis effect. For this reason, we chose to combine the calibration readout circuit with the voltage-time (V-T) measurement system to optimize the measurement environment and successfully reduced the instability of the sensor. The drift rate was reduced by about 51.1%, and the hysteresis rate was reduced by 13% and 28% at different measurement cycles. In addition, the characteristics of the sensor under dynamic conditions were also investigated, and it was found that the sensor has an average sensitivity of 13.71 mV/mM and the linearity of 0.998 at a flow rate of 5.6 μL/min.

Photodetachment of H− in non-ideal classical plasmas

The effects of non-ideality of classical plasmas on the cross sections of the photodetachment of the negative ion of hydrogen (H−) have been investigated within the framework of the dipole approximation. An effective potential, deduced from a solution of Bogolyubov's hierarchy equations, has been used to model the interactions among the charged particles in the non-ideal classical plasmas. Wave functions and energies of H−(1S) and H(1s) are calculated accurately by employing extensive basis sets within the framework of Ritz's variational principle. A detailed study is made on the changes of photodetachment cross section due to the varying non-ideality of plasma in a wide range. It is found that the wavelength corresponding to the maximum value of the photodetachment cross section moves forward due to the increasing non-ideality of plasma.

A High-Performance Standard Dipole Antenna Suitable for Antenna Calibration

Ideal dipole antennas are desirable for antenna calibration. However, real-world implementation issues introduce inevitable nonideal effects that can significantly affect the quality of calibration. In this communication, a 2 GHz standard dipole (SD) antenna is presented with an excellent overall performance. This result is achieved by an innovative design with an optimized element shape and an embedded (shielded) balun. The designed feeding structure is a balanced structure that transitions from parallel strip lines to coaxial lines. The feeding method avoids the impact of electromagnetic environment asymmetry while achieving an appropriate balance. The measured relative bandwidth of the dipole exceeds 15%, and the antenna gain is approximately 2 dBi. The cross-polarization ratio is greater than 27 dB in the horizontal plane, and the horizontal gain variation is less than 0.2 dB. The dipole has a symmetrical vertical plane pattern, and the maximum gain point does not deviate from the horizontal plane. The high performance of this SD makes it suitable for antenna calibration.

Automated prediction of lattice parameters from X-ray powder diffraction patterns.

A key step in the analysis of powder X-ray diffraction (PXRD) data is the accurate determination of unit-cell lattice parameters. This step often requires significant human intervention and is a bottleneck that hinders efforts towards automated analysis. This work develops a series of one-dimensional convolutional neural networks (1D-CNNs) trained to provide lattice parameter estimates for each crystal system. A mean absolute percentage error of approximately 10% is achieved for each crystal system, which corresponds to a 100- to 1000-fold reduction in lattice parameter search space volume. The models learn from nearly one million crystal structures contained within the Inorganic Crystal Structure Database and the Cambridge Structural Database and, due to the nature of these two complimentary databases, the models generalize well across chemistries. A key component of this work is a systematic analysis of the effect of different realistic experimental non-idealities on model performance. It is found that the addition of impurity phases, baseline noise and peak broadening present the greatest challenges to learning, while zero-offset error and random intensity modulations have little effect. However, appropriate data modification schemes can be used to bolster model performance and yield reasonable predictions, even for data which simulate realistic experimental non-idealities. In order to obtain accurate results, a new approach is introduced which uses the initial machine learning estimates with existing iterative whole-pattern refinement schemes to tackle automated unit-cell solution.

A New Realization of Third-Order Inverse Bandpass Filter and Its Application as an Oscillator

A new operational transresistance amplifier (OTRA)-based third-order inverse bandpass filter (IBPF) is presented in this paper. To illustrate an application of the presented IBPF, the proposed configuration is used to implement a third-order quadrature oscillator (TOQO). Furthermore, the nonideal behavior of the proposed topologies has been examined using a single-pole model of the OTRA. It is perceived that for high-frequency applications, the effect of nonidealities may be eliminated through self-compensation. Passive sensitivities are computed and are found to be less than half, rendering proposed topologies insensitive to component variations. Phase noise study and frequency stability analysis have been carried out and found that the proposed TOQO enjoys good frequency stability. The proposed circuits’ workability is verified through an Analog Design Environment (ADE) Spectre tool provided by Cadence Virtuoso using 0.18 [Formula: see text]m CMOS gpdk process parameters. Monte Carlo statistical analysis is also carried out to assess the prefabrication performances. Total harmonic distortion (THD) for the proposed IBPF is found to be less than 5%. Pre- and post-layout simulations are also included to affirm the theory. Excellent agreement among simulation results and theory is observed.

Simple Current-Mode Squaring and Square-Rooting Circuits: Applications of MO-CCCCTA

This work provides new designs of simple current-mode squaring and square-rooting circuits using multiple-output current controlled current conveyor transconductance amplifier (MO-CCCCTA) as an active building block. Since the proposed circuits need no other external components, they are capable of high-frequency operation and well fitted for IC fabrication. Furthermore, they are insensitive to ambient temperature and their gains can be controlled easily by adjusting the bias currents of MO-CCCCTA. Additionally, the effects of MO-CCCCTA non-idealities on the designed circuits have also been investigated and discussed. Simulation results generated through PSPICE software using TSMC 0.18 µm CMOS process parameters have been presented to justify the theoretical analysis. The static power consumption, bandwidth, and maximum linearity error in dc transfer characteristic measurement for the square-rooting circuit are found to be 0.17 mW, 445.63 MHz and 1.12 %, while for the squaring circuit they are 0.326 mW, 61.15 MHz and 2.38 %, respectively. The application of the reported circuits as a 2-input vector summation circuit has also been included to strengthen the design ideas.
 HIGHLIGHTS
 
 Simple structures of fully integrable current-mode squarers and square-rooters with low component count and lower power dissipation
 The circuits are insensitive to temperature drift and their gains can be controlled easily by adjusting the bias currents of MO-CCCCTA
 Bandwidth, static power dissipation, linearity error of square-rooter are 445.63 MHz, 0.17 mW & ≤ 1.12 %; and for the squarer 61.15 MHz, 0.326 mW & 2.38 %, respectively
 
 GRAPHICAL ABSTRACT

Novel Fractional-Order Current-Mode VCOs/SRCOs with All-Grounded-Passive-Elements

Five new structures of linear fractional-order voltage-controlled oscillators (FO-VCOs) utilizing only Multiplication-Mode Current Conveyors (MMCCs) and canonic numbers of all grounded passive elements (AGPEs) are presented in this paper. The derivation procedure has been detailed along with the relevant nonideal analysis. The work also presents three fractional-order cases of the oscillators and brings out the effects of port nonidealities and port parasitics on the performance of presented FO-VCOs. The workability of all the five new FO-VCOs has been validated on PSPICE utilizing library files of AD844 and AD835 for realizing MMCC employed in the FO-VCOs. For all the three special fractional-order cases, the simulation results have been tabulated along with relevant MATLAB plots that facilitate comparison among oscillation parameters and the fractional order. The harmonic distortion figures have been found out by Fourier analysis. Experimental workability of a VCO, employing MMCC realized with AD835 and AD844 of our investigation is included to support hardware functionality.

Analog Circuit Design Using Symbolic Math Toolboxes: Demonstrative Examples

In this article, a synthesis methodology for analog circuit design is presented. This methodology utilizes symbolic math tools to systematically and exhaustively search for candidate analog circuits avoiding tedious manual work. The two-port network matrix representation of active devices, such as MOS transistors, paves the way for efficiently using advanced symbolic math toolboxes (e.g., in MAPLE or MATLAB) to automate the generation of new analog circuits and further investigate the effects of nonidealities and parasitics. Using this synthesis methodology new amplifiers, filters, and oscillators can be obtained starting from a predefined structure. This article aims to motivate and provide an overview of the current status of research in this area. In addition, two detailed design examples of a family of differential filters and a family of differential oscillators along with their simulations and measurement results are provided to illustrate and verify the synthesis methodology.

A novel system-level modeling and design approach for high performance single-loop sigma-delta (∑Δ) modulators

PurposeThis paper attempted a novel approach for system-level modeling and simulation of sigma-delta modulator for low-frequency CMOS integrated analog to digital interfaces. Comparative analysis of various architectures topologies, circuit implementation techniques are described with analytical procedure for effective selection of topologies for targeted specifications.Design/methodology/approachVirtual instruments are presented in labview environment to analyze the correlation of circuit-level non-ideal effects with key design parameters over sampling ratio, coarse quantizer bits and loop filter order. A fourth-order single-loop sigma-delta modulator is designed and verified in MATLAB simulink environment with careful selection of integrator weights to meet stable desired performance.FindingsThe proposed designed achieved SNDR of 122 dB and 20 bit resolution satisfying high-resolution requirements of low-frequency biomedical signal processing applications. Even though the simulation performed at behavioral level, the results obtained are considered as accurate, by including all non-ideal and non-linear circuit errors in simulation process.Originality/valueVirtual instruments using labview environment used to analyze the correlation of circuit-level non-ideal effects with key design parameters over sampling ratio, coarse quantizer bits and loop filter order for accurate design.

Non-ideal gas effect of gas storage inside confined pores: A case study of Yongye shale

Unlike conventional reservoirs, the phase behavior of gas in shale formations rich in nanopores is no longer the same as that in bulk regions because of the non-ideal gas effect. To investigate the role of the non-ideal gas effect introduced by nanopores, gas content distribution along the burial depth (3772 m–3872 m) of one of the Yongye shale formations was analyzed according to its pore properties of fresh shale core samples. It is found that gas content is not uniformly distributed along the burial depth and it has a similar distribution trend with the specific pore volume and specific surface area, especially with those of mesopores and micropores. In addition, the specific volumes of micropores and mesopores are more significant in organic-rich pores obtained from the burial depth of 3805 m–3870 m, where a large amount of gas was found. Since the non-ideal gas effect (i.e., critical temperature and pressure shift) becomes obvious in pores with diameters of less than 10 nm, more gas is stored in the shale matrix with more micropores and mesopores. Compared with the case without considering the non-ideal gas effect, the gas content of the shale formation (with burial depth from 3805 m to 3870 m) under geological conditions increases significantly. A better understanding of the non-ideal gas effect in nanopores may enable a more accurate assessment of the gas-in-place content of shale reservoirs.

Leveraging De Donder relations for a thermodynamically rigorous analysis of reaction kinetics in liquid media

This Mini-review considers the use of De Donder relations to facilitate a thermodynamically rigorous discussion of liquid-phase reaction kinetics through the analysis of elementary steps. In quantifying “solvent effects,” pure species reference states are convenient. Rate expressions developed with this convention capture all effects of thermodynamic non-ideality in solvent-specific activity coefficients or excess free energies, whereas commonly applied infinite dilution reference states lead to solvent- and composition-dependent standard-state rate and equilibrium constants. Two solvent effects are described: a “kinetic” effect, which comprises solvation of a transition state relative to reactants in an elementary step, and a “thermodynamic” effect, which comprises solvation of products relative to reactants in an elementary step. The former impacts the forward rate constant, and the latter impacts the reversibility. These effects are formally encoded in De Donder rate expressions; thus, they inherently account for solvation while maintaining thermodynamic consistency with respect to elementary rate and equilibrium constants. A series of case studies are presented. These demonstrate that solvent effects can lead to substantial deviations from anticipated behavior during routine analysis of liquid-phase reactions. Additionally, we find that surface reactions and degree of rate control in multi-reaction sequences can be impacted by bulk solvation, but such effects are difficult to predict a priori.

Double stage converter with low current stress for low to high voltage conversion in nanogrid

A low to high voltage conversion technique has been proposed in this paper using double stages of switched inductors for nanogrid applications. The proposed converter topology utilizes fewer components, achieves high voltage gain at a small value duty ratio, and has high efficiency. Moreover, the proposed converter provides a reduced switch current stress to obtain a stable constant boosted DC voltage. Therefore, it requires low-current rating switches and hence leads to cost reduction. Additionally, the load and the source end are connected to the same ground. The principle of operation, theoretical waveforms in Continuous Conduction Mode (CCM), and Discontinuous Conduction Mode (DCM) with steady-state analysis are discussed. A detailed discussion about the effect of non-idealities on the high voltage conversion, the design of components, and a comparison of the performance characteristics such as the number of components, Voltage Gain in CCM, switch current stress, normalized switch voltage stress, and efficiency of the proposed converter topology with other converters are presented. The experimental results of the 500W laboratory prototype are also shown to validate the operation of the proposed converter.

Polarisation gating technique in nonlinear Compton scattering: effect of radiation friction and electron beam nonideality

We discuss the effect of radiation friction and quantum recoil on the parameters of a gamma comb with narrow spectral peaks, arising when use is made of laser pulses with time-dependent polarisation, which reduces significantly the ponderomotive broadening of harmonics. A detailed numerical study of the contribution of the electron beam nonideality to the observability of the effect is presented.

Ion core effect on scattering processes in dense plasmas

A pseudopotential approach was used to study the effect of an ionic core on the electron–ion scattering in dense plasmas. Screening of the ion charge is taken into account using the density response function in the long wavelength limit. Additionally, the effect of electronic non-ideality is included using the compressibilty sum-rule connecting the local field correction and the exchange-correlation part of the electronic free energy density. Using a screened pseudopotential, we have computed electron–ion scattering phase shifts, the total elastic scattering cross section, and the transport cross section. It is found that the ionic core leads to the strong decrease in the scattering cross sections. Additionally, it is shown that the transport cross section has a non-monotonic dependence on the variation of the ionic core field parameters.

A simulation study of nonideal mixing effect on the dynamic response of an exothermic CSTR with Cholette’s model

Abstract The study of nonideal mixing effect on the dynamic behaviors of CSTRs has very rarely been published in the literature. In this work, Cholette’s model is employed to explore the nonideal mixing effect on the dynamic response of a nonisothermal CSTR. The analysis shows that the mixing parameter n (the fraction of the feed entering the zone of perfect mixing) and m (the fraction of the total volume of the reactor), indeed affect the characteristic roots of transfer function of a real CSTR, which determine the system stability. On the other hand, the inverse response and overshoot response are also affected by the nonideal mixing in a nonisothemal CSTR. These results are of much help for the design and control of a real CSTR.

Simulation study of the nonideal mixing effect on the stability of continuous and discrete proportional control of a nonadiabatic CSTR based on Cholette’s model

ABSTRACT Studies on discrete control continuous stirred tank reactor (CSTR) with Cholette’s model have not been published in the literature because the mathematical model is far too complicated. This work uses Cholette’s model with discrete proportional control with the mixing parameter n (the fraction of the feed entering the perfect mixing zone) and m (the fraction of the total volume of the reactor) to study exothermic CSTR behavior. Meanwhile, exothermic CSTR continuous proportional control is used to compare the discrete proportional control results. It is found that the nonideal mixing parameters m and n indeed affect the control stability of both the continuous and discrete proportional control. The contribution of this paper is that this analysis can determine the stability region in the control system phase plane. Furthermore, if the nonideal mixing effect is ignored, the stable control system may become unstable and unsafe. Our results are of significant help for CSTR control in industry because the ideal mixing is hardly attainable in reality.

In-situ learning in multilayer locally-connected memristive spiking neural network

Memristive spiking neural networks (MSNNs) have great potential to process information with higher efficiency and lower time latency than conventional artificial neural networks (ANNs). However, MSNNs still lack effective hardware-based training algorithms to achieve comparable performance to the mature ANNs. Therefore, a multilayer locally-connected (LC) MSNN is proposed to realize high performance with self-adaptive and in-situ learning. In the LC-MSNN, spatial and temporal interactions are introduced to activate hidden neurons spontaneously; synaptic weights are updated locally with spike-time-dependent plasticity (STDP) by pulse scheme including processing and updating phases; nonlinear conductance response (CR) is utilized to realize the adjustive learning rate. The LC-MSNN is comprehensively verified and benchmarked with the MNIST dataset. Moreover, self-adaptive activations of the hidden neurons are investigated by extracting and visualizing their internal states and related features; the adjustive learning rate is studied in different nonlinear CR. Effects of non-idealities including finite resolution, device-to-device variation, and yield, are also taken into consideration in the LC-MSNN. Simulation results show the LC-MSNN has better performance (maximum recognition rate of 97.4%) and robustness to non-idealities. Therefore, this method is a hardware-friendly algorithm and can be applied to realize high-performance SNNs in a memristor-based hardware system.