Linear Mode Of Operation Research Articles

About theory of hybride TWTO and an amplifire with a complex permittivity

The purpose of this work is to construct a nonlinear theory of a hybrid between travelling wave tube (TWT) and an amplifier with a complex permittivity. Methods. The following model is considered: an ion-compensated one-dimensional electron beam penetrates the input travelling wave tube section, then flies into a medium with a complex permittivity, and then enters the output travelling wave tube section. A linear theory of this hybrid is constructed, and its results are compared with the results of the well-known linear theory of travelling wave tube. A nonlinear theory of this hybrid was constructed by a modified wave method, and the results were compared with the nonlinear travelling wave tube theory obtained by the classical Ovcharov–Solntsev’s wave method. In addition, to test the limits of applicability of the obtained results, a stationary nonlinear theory of the hybrid was constructed, obtained using the large particle method. The results of this theory were also compared with the stationary nonlinear travelling wave tube theory constructed using the large particle method. Results and conclusion. Based on the results of the developed theories, it is shown that, under certain parameters, the linear theory and nonlinear theories (both by the modified Ovcharov–Solntsev’s wave method and by the large particle method) make it possible to obtain comparable results both in the case of a classical travelling wave tube and for the hybrid under study. It is shown that under certain parameters, due to the resistive instability, the bunching of electrons can be noticeably improved and, as a result, the gain of the hybrid can exceed the gain in a classical travelling wave tube with the same parameters and the same total length of the device in the linear mode of operation. In the nonlinear mode of operation, the specified hybrid, with optimal environmental parameters, can have significantly higher values of output power and efficiency than travelling wave tube with the same value of the space charge parameter and the Pierce parameter.

Importance of source and drain extension design in cryogenic MOSFET operation: causes of unexpected threshold voltage increases

Increased threshold voltages have been observed during linear-mode operation of short-channel bulk metal-oxide-semiconductor field-effect transistors (MOSFETs) employing shallow source and drain extension technology at cryogenic temperatures. These increases were suppressed during saturation-mode operation, which resulted in the increase of a threshold voltage variation between linear- and saturation-modes as if drain-induced barrier lowering occurred. Numerical simulations revealed that these increases originate from enhanced depletion in the extension region and subsequent increases in channel resistance at cryogenic temperatures. These data suggest that shallow extensions should be designed more carefully in the case of MOSFETs intended for cryogenic operation.

Direct Electrochemical Signaling in Organic Electrochemical Transistors Comprising High-Conductivity Double-Network Hydrogels.

In composite hydrogels, the high electrical performance of poly(3,4-ethylenedioxythiophene) complexed with poly(styrenesulfonate) (PEDOT:PSS) is integrated with complementary structural and electrochemical functions via a rationally designed poly(acrylamide) second network incorporating phenylboronic acid (PBA). Free-standing double-network hydrogels prepared by a simple one-pot radical polymerization exhibit state-of-the-art electrical conductivity (∼20 S cm-1 in phosphate buffered saline) while retaining a degree of hydration similar to that of biological soft tissues. Low resistance contacts to Au electrodes are formed via facile thermo-mechanical annealing and demonstrate stability over a month of continuous immersion, thus enabling hydrogels to serve as channels of organic electrochemical transistors (OECTs). Despite thicknesses of ∼100 μm, gating of hydrogel OECTs is efficient with transconductances gm ∼ 40 mS and on/off ratios of 103 in saturation mode operation, whereas sufficiently high conductivity enables linear mode operation (gm ∼ 1 mS at -10 mV drain bias). This drives a shift of sensing strategy toward detection of electrochemical signals originating within the bulky channel. A kinetic basis for glucose detection via diol esterification on PBA is identified as the coupling of PBA equilibrium to electrocatalyzed O2 reduction occurring on PEDOT in cathodic potentials. Hydrogel OECTs inherently amplify this direct electrochemical signal, demonstrating the viability of a new class of soft, structural biosensors.

A prominent unified crosstalk model for linear and sub-threshold regions in mixed CNT bundle interconnects

With the feasibility to scale the devices and interconnects in highly sophisticated VLSI technology, the demand for high-speed and low-power e-applications have also subsequently increased stupendously. Based on the applications and requirements, a VLSI system is operated in different modes as linear or sub-threshold. A unified analytical model for describing both these linear and sub-threshold modes is highly desirable. This has been innovatively presented in the current paper. Moreover, the futuristic and emerging mixed carbon nanotube bundle (MCB) as interconnects for both linear and sub-threshold region of operations has been considered. The essential signal integrity analysis comprising of several crosstalk effects such as associated transient response, delay and power have been analyzed. To evaluate this, analytical model is formulated and proposed using accurate unconditionally-stable finite-difference time-domain (USFDTD) technique. Utilizing the proposed model, it is investigated that linear mode of operation is good for realizing high-speed systems while sub-threshold is a preferable operation for applications targeted for low-power. Comprehensively, it is envisaged that the average power-delay-product in MCB interconnects operating in sub-threshold region is low and reduced by 74% compared to corresponding linear region of operation. Also, it is demonstrated that the proposed unified USFDTD based model for MCB interconnects operating in different modes of operation is stable and not constricted by the Courant condition. At maximum allowable time step, the proposed model is nearly 10 and 25 times faster than the conventional FDTD analytical and HSPICE simulation models, respectively. The results reveal that USFDTD technique provides better accuracy than the FDTD technique. The different performance analyses are performed at 22 nm technology node.

Extraction of source resistance in thin film transistors using a single gated-probe outside the channel

Extraction of source resistance in top contact thin film transistors (TFTs) is described using a gated three probe device structure. The three probes include a source terminal, a drain terminal and an electrode deposited outside the channel and kept open-circuited leading to unperturbed transistor operation. A measurement of floating potential of this probe together with a family of universal curves is presented, which allows estimation of source resistance from dc measurements in the linear mode of operation on a single device. Simulation results obtained for TFTs with different semiconductor technologies, like organic semiconductor pentacene, indium-gallium-zinc-oxide and amorphous silicon demonstrate the applicability of this technique. Experimental results obtained from organic TFTs with pentacene semiconductor confirm that the method gives estimates that are close to the values obtained from the relatively more complex transfer length measurement (TLM) technique. It is also shown that unlike the TLM method, the outside gated probe technique is much less sensitive to errors in device parameters and variations in device dimensions, such as the channel length.

Development of an Application Specific Integrated Circuit for Signal Detection in Experimental Studies of Fast Processes

This paper presents a new integrated circuit designed for signal readout in a silicon microstrip detector in experimental observations of fast processes at a synchrotron radiation beam. The first variants of this circuit were used in a prototype detector based on a microstrip silicon sensor and were tested at an intense synchrotron radiation beam at the VEPP-4M storage ring in the Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences. The results of the first measurements showed that the main objectives of this development were achieved: the time resolution and frame rate satisfy the initial specifications and the maximum detected signal in a linear mode of operation provides a significant increase in the detected photon flux compared to the previous version of the detector based on gas technology. The main problem detected during testing of the prototype is the relatively high noise level, which will be reduced in the next version of the integrated circuit by optimizing some circuit solutions.

The condition for the maximum of the generalized power function in the problem of forming a multi-mode control law with limitation

A quasi-optimal control law is developed based on the condition for the maxi-mum of the generalized power function taking into account the stationarity of the Hamiltonian on the switching line for control objects that can be represented by the Lagrange equations of the second kind. The comparative analysis is carried out based on the mathematical simulation using the optimal nonlinear control laws with respect to several criteria. We found that the modes of the proposed control law provide high accuracy of approximation to the optimal performance laws and the Fuller laws, reducing energy costs for control by eliminating more frequent switching. The choice of the parameters of the developed control law makes it possible to implement a wide range of both nonlinear and linear operating modes, which allows to classify the obtained control law as multimode law.

Experimental Study of the Cells Interaction on Linear and Nonlinear Operating Modes

In this article, the results of SAS samples laboratory research on an interferometer with a normal sound wave incidence at sound pressure levels of 100 and 130 dB are presented. The mutual influence of prismatic resonators was revealed, which leads to a decrease in the resonators group acoustic efficiency.

Design of Helmholtz Resonator with Required Characteristics

The method of calculation design of the Helmholtz resonator in the duct is considered based on the transition to dimensionless parameters, which are determined concerning the transverse size of the duct. The acoustical impedance of Helmholtz resonator is analyzed. The application of this approach to the special case of a short-neck resonator and the general case with a linear operating mode of the resonator is described.

Ion-Sensitive Gated Bipolar Transistor

In this article, we study the ion-sensitive gated bipolar transistor (ISBiT) by forward biasing the source-body diode of the ion-sensitive field-effect transistor (ISFET). Based on theory, extensive TCAD device simulations, and experiments, it is shown that the ISBiT operates at lower gate-voltages with a higher transconductance ( ${g}_{m}$ ) than the ISFET both in subthreshold and near-threshold modes. In addition, overall maximum $g_{m}$ ’s have been obtained for the former when operating in saturation mode. However, in the linear superthreshold operation mode, the ISBiT shows lower $g_{m}$ ’s because of the field-induced mobility reduction. The same trends have been obtained for the pH-sensitivity expressed as $\partial {I}_{\text {D}}/\partial {\text {pH}}$ , since it is linearly dependent on the ${g}_{m}$ , as predicted by the theory. Basically, the ISBiT offers more tunability, hence, freedom in the sensor system.

Understanding Normalized Mean Squared Error in Power Amplifier Linearization

This letter provides a detailed analysis of the normalized mean squared error (NMSE) of an ideal orthogonal frequency-division multiplexing (OFDM) system, subject to soft clipping of the power amplifier (PA) output. Based on the central limit theorem, the OFDM baseband input is modeled as white Gaussian noise, and based on the Bussgang theorem, the NMSE is studied in some detail. Asymptotes describing the NMSE for the considered system are derived, when the system is working in the linear operation mode and when working under compression, respectively. Detailed yet simple expressions between the NMSE, average output power, saturation voltage of the PA, and the noise level of the additive channel or thermal noise are derived, which are believed to provide insight into the system's behavior.

Bifurcation Phenomena Studies of a Voltage Controlled Buck-Inverter Cascade System

This paper studies the complex bifurcation phenomena of a voltage-controlled Buck-inverter cascade system. A state-flow chart is drawn to illustrate the complex relations among the linear operating modes. Combined with the state transition function of each mode, the time response of the system can be obtained. For period-one steady state, the periodic mapping function and its fixed point are further derived, on the basis of which the Jacobi matrix is developed and its maximum eigenvalue is analyzed to understand the bifurcation diagram. By globally analyzing the state space using this cell mapping method, the coexistence of attractors is revealed in the Buck-inverter system. All theoretical results have been verified experimentally on a prototype system. The results obtained can be used for guiding the design and analysis of the Buck-inverter system. The analyzing method can be helpful for studying other power electronics systems with compound topologies.

Generalized PWM-Based Method for Multiphase Neutral-Point-Clamped Converters With Capacitor Voltage Balance Capability

This paper presents a generalized pulse width modulation (PWM)-based control algorithm for multiphase neutral-point-clamped (NPC) converters. The proposed algorithm provides a zero sequence to be added to the reference voltages that contributes to improve the performance of the converter by: 1) Regulating the neutral-point (NP) current to eliminate/attenuate the low-frequency NP voltage ripples; 2) reducing the switching losses of the power semiconductors; and 3) maximizing the range of modulation indices for linear operation mode. The control method is formulated following a carrier-based PWM approach. Hence, dealing with complex space-vector diagrams to solve the modulation problem for multiphase converters is avoided. The recursive approach means that it can be easily extended to n -phase converters without increasing the complexity and computational burden, making it especially attractive for digital implementation. The proposed method allows regulating the NP voltage without the need for external controllers; therefore, no parameter tuning is required. The algorithm has been tested in a four-leg NPC converter prototype performing as a three- and four-phase system and operating with balanced and unbalanced loads.

Control of Three-to-Five-Phase Matrix Converter Using Carrier-Based PWM Algorithm

Abstract - This paper proposes a simple Carrier-Based PWM (CBPWM) technique to control the three- to five-phase Direct Matrix Converter (3×5 DMC). The proposed technique uses the indirect modulation approach to control the 3×5 DMC such as a three-phase bidirectional rectifier followed by five-phase voltage source inverter (VSI). Based on this approach, it is possible to synthesize the desired five-phase output voltages with sinusoidal three-phase input currents and unity input power factor. A CBPWM method is suggested for each stage independently including both linear and overmodulation operating modes. By the proposed technique, in both operating modes, the maximum possible overall Voltage Transfer Ratio (VTR) are achieved. Moreover, this technique allows the input power factor to be controlled by controlling the input current displacement angle. The feasibility of the proposed technique has been verified by a series of simulation and experimental results based on Matlab/Simulink and dSPACE-DS1104 platform. The results show that, a sinusoidal output and input waveforms can be achieved with a maximum possible VTR in the linear region. However, in the overmodulation region, a maximum possible VTR is achieved at the cost of some distortion of output and input waveforms. Therefore, this technique can be used for the application where a higher VTR is essential.

Photon-counting and analog operation of a 24-pixel photon number resolving detector based on superconducting nanowires.

We investigate the transition from the photon-counting to the linear operation mode in a large-dynamic range photon-number-resolving-detector (PNRD). A 24-pixel photon-number-resolving-detector, based on superconducting nanowires in a series configuration, has been fabricated and characterized. The voltage pulses, generated by the pixels, are summed up into a single readout pulse whose height is proportional to the detected photon number. The device can resolve up to twenty-five distinct output levels corresponding to the detection of n = 0-24 photons. Due to its large dynamic range, high sensitivity, high speed and wide wavelength range, this device has potential for linear detection in the few tens of photons range. We show its application in the detection of analog optical signals at frequencies up to few hundred MHz and investigate the limits related to the finite number of pixels and to the pixel's dead time.

Not Just a Phase: Outphasing Power Amplifiers

Performing RF amplification in a way that is simultaneously linear and efficient has long been a challenge in power amplifier (PA) design. In short, single-transistor PAs can either be operated in a linear (but inefficient) current-source mode of operation or as efficient (but nonlinear) switches, but these two modes are mutually exclusive. The outphasing concept has been explored to address this tradeoff by using efficient but nonlinear elements in an architecture providing linear output power control.

Charge-layer design considerations in SAGCM InGaAs/InAlAs avalanche photodiodes

We report on the development of mesa-processed InGaAs/InAlAs avalanche photodiodes (APDs) for short-wave infrared (SWIR) imaging applications with demand for high gain and low breakdown voltage. Devices are designed with separate absorption, grading, charge, and multiplication (SAGCM) layers. Special attention has been paid to the charge layer in order to optimize the structure for low band discontinuities and an appropriate electric field distribution. Hereof, a combination of a p-type grading layer and charge layer is presented. Band-edge profile calculations as well as electro-optical characterization results of the APDs will be discussed in this article. Our optimized APD structures reveal low punch-through and low breakdown voltage of and , respectively. A maximum gain of in the linear operation mode is demonstrated at room temperature and has been measured at 20 V bias.

Surface wave and linear operating mode of a plasma antenna

The relation between the propagation conditions of a surface electromagnetic wave along a finiteradius plasma cylinder and the linear operating mode of a plasma antenna is investigated. The solution to the dispersion relation for a surface wave propagating along a finite-radius plasma cylinder is analyzed for weakly and strongly collisional plasmas. Computer simulations of an asymmetrical plasma dipole antenna are performed using the KARAT code, wherein the dielectric properties of plasma are described in terms of the Drude model. The plasma parameters corresponding to the linear operating mode of a plasma antenna are determined. It is demonstrated that the characteristics of the plasma antenna in this mode are close to those of an analogous metal antenna.

Performance evaluation of a prototype multi-bounce time-of-flight mass spectrometer in linear mode and applications in space science

Mass spectrometry is a powerful tool to measure the composition of volatile and semi volatile gases. The necessity to accurately identify and quantify unknown species lead to the requirements of a mass spectrometer as the detector of choice in most separation science and direct sample analysis situations. Advantages of time-of-flight mass spectrometry (TOFMS) are the high mass resolution, high mass range, and the measurement of the entire mass range in each extraction. The multi-bounce time-of-flight mass spectrometer (MBTOF) described in this work, takes advantage of a small footprint without sacrificing mass resolution. To achieve this, the MBTOF prototype uses a linear flight path with dual lens stacks. Ions are bounced in between the mirrors for a specified duration whereby increasing their flight time and resolution. The number of bounces can tune the resolution of the instrument. To show the minimum capabilities of the instrument and further applications of it, MBTOF was operated in linear mode. The instrument is designed for a multibounce passage of the ion optics and the focal point of the ion optics is optimized for this application, therefore the resolution in linear mode is limited. However, even in linear mode of operation, the mass resolution meets or exceeds that of a quadrupole mass spectrometer with limited power supplies required for operations. The measurements presented here are based on lab measurements of the early lab prototype MBTOF operated in a linear flight mode with low ion source extraction fields. A detailed evaluation including filament characterization, dynamic range and resolution are investigated. Further discussion involving applications on planetary missions for rocket science, coupling of MBTOF with laser thermal desorption or gas chromatography for potential organic determination in deep space are included.

Experimental investigation of the charge-layer doping level in InGaAs/InAlAs avalanche photodiodes

We report on the development of mesa-processed InGaAs/InAlAs avalanche photodiodes (APDs) for short-wave infrared (SWIR) applications with demand for high gain and low breakdown voltage. Devices are designed with separate absorption, grading, charge and multiplication (SAGCM) layers. Special attention has been paid to the charge layer in order to optimize the distribution of the electric field across the device. Since the device performance significantly changes for deviations of only several percent in the doping concentration a series with variation of the charge-layer doping level has been carried out. Band-edge profile calculations as well as electro-optical characterization results of the APDs will be discussed in this article. Our optimized APD structures reveal a low dark-current density of Id=1×10-4A/cm2 at gain M=10 and a low breakdown voltage Vbd<30V. A maximum gain larger than 300 in the linear operation mode is demonstrated at room temperature as well as 140K.