Series Inductance Research Articles

A novel design of a low-voltage low-loss T-match RF-MEMS capacitive switch

This paper presents a novel design, optimization and analysis of capacitive radio frequency (RF) micro-electromechanical system (MEMS) switch. The design incorporates a novel membrane and beams' structure with two short high-impedance transmission-line (T-line) sections added on either side of the switch (namely T-match switch) to improve its RF performance, while maintaining low-actuation voltage. The short high-impedance T-line section has narrower width and higher impedance than the coplanar waveguide (CPW)'s signal line, behaves as series inductor to compensate the switch's up-state capacitance and provides excellent matching at the design frequency. This high-impedance T-line section was designed, simulated and optimized using finite-element-modelling (FEM) tool of electromagnetic (EM) simulator of AWR Design EnvironmentTM. The optimized T-line section's width and length is 10 µm and 70 µm, respectively. The RF-MEMS switch is actuated by electrostatic force with low-actuation voltage of 2.9 V, has maximum von Mises stress of 13.208 MPa which is less than aluminium's yield stress and can be operated in robust conditions. Compared to the normal capacitive RF-MEMS switch, this T-match capacitive RF-MEMS switch with two sections of optimized high-impedance T line has improved the performance of return loss and insertion loss, at switch-on state, by 45.83% and 55.35%, respectively; while at the switch-off state, the isolation is increased by 24.05%; only the switch-off return loss is degraded by 11.7% but the value (ź 0.5519 dB) is still located in the range of design specifications. The RF-MEMS switch's actuation time was simulated to be ~ 27 µs with amplitude of 5 V up-step voltage.

Investigation of a two-electrode gas switch with electrodynamical acceleration of spark channel in oscillatory regime of discharge

We have developed a compact gas switch intended for operation in oscillatory (low damping) regime of discharge. It is two-electrode switch with electrodynamic acceleration of a spark channel and a matched series injection trigger generator. A series inductance is employed for isolation of a trigger pulse from a surrounded circuit. Two operations regimes have been investigated, namely “fast” regime with current amplitude ~ 160 kA, total charge ~ 12 C, period of oscillations 60 μ s, full pulse length ~ 400 μ s and “slow” regime with current amplitude ~ 30 kA, total charge 18 C, period of oscillations 360 μ s, full pulse length ~ 3 ms. The spark gap can be triggered reliably from 16 to 50 kV (at 72 kV self-breakdown voltage). Time delay in firing was less than 35 ns at 1 ns jitter at 30 mm gap and 40 kV charging voltage. The spark gap is designed for 50 kV charging voltage, at a current up to 200 kA, and up to 20 C charge transfer. Arc motion and electrodes erosion in this spark gap have been investigated. The main results are as follows: the arc channel moves on ~ 18 cm in fast regime and ~ 25 cm in slow regime. Results of the switch operation in slow and fast regimes with operational voltage of 40 kV and stored energy 32 kJ promise to get high lifetime. In this paper we present design for the spark gap and trigger generator. Test bed schematics and results of the tests are also described.

Unconditionally Stable Non-Foster Element Using Active Transversal-Filter-Based Negative Group Delay Circuit

This letter introduces a novel type of non-Foster element using a microwave transversal-filter-based negative group delay (NGD) circuit that can exhibit unconditional stability. The proposed device is realized by a distributed amplifier, in which the NGD response is synthesized by adjusting the ratio of transconductance of transistors in each stage. On top of this, by properly amending the in-band magnitude and phase characteristics, the NGD circuit can realize non-Foster elements within the operating band. Furthermore, thanks to the distributed topology, the proposed network has very good input and output matching characteristics. As proof-of-concept, a prototype of the proposed non-Foster element is built to validate the proposed scheme. The experimental results show that the proposed circuit can realize a unilateral non-Foster element composed of a −1 pF shunt capacitor and a −1.25 nH series inductor.

Frequency Response Simulation Analysis of Waveguide Photodetectors

In waveguide photodetectors the bandwidth and the quantum efficiency may be specified almost independently because the absorption of light is in the longitudinal direction whereas the current flows in the transversal direction. Then, these devices may combine high bandwidth with high quantum efficiency. In this paper a detailed numerical analysis of the frequency response of waveguide photodetectors is presented. The calculations show that the capacitive effects limit the bandwidth but that by an appropriate choice of a series inductance the maximum bandwidth almost doubles.

Folded Feedthrough Multilayer Ceramic Capacitor EMI Filter

A chip three-terminal multilayer ceramic capacitor (MLCC) electromagnetic interference (EMI) filter with a good stopband characteristic was designed. Parasitic effects on the internal signal electrode, including equivalent parallel capacitance and series inductance, were utilized to form a tunable transmission zero in stopband by folding the traditional chip three-terminal feedthrough MLCC. Based on a network theory, an equivalent circuit was constructed in ADS to explain the operating mechanism of the proposed structure. The ADS and HFSS were utilized to simulate the proposed structure, and the measured results corresponded to the simulation results. The structure of the proposed EMI filter presents a new method to improve the stopband characteristic of capacitor EMI filters.

Modeling the Frequency-Dependent Series Parasitics of Ground–Signal–Ground Pads Used to Probe On-Wafer Microstrip-Line-Fed Devices

This paper presents a model for the parasitic series resistance and inductance of pads used to on-wafer probing of microstrip-line-fed devices. The model accounts for the frequency-dependent current distribution and skin effects, as well as for the geometry of the pad array, which allows to obtain the series parasitics without the need of measuring a “short” dummy structure. Accordingly, these closed-form formulas can be used by designers in order to predict the series parasitic effects introduced by the pads. In this paper, the proposal is used to correct experimental S-parameters from the pad parasitics on inductor and transmission line measurements requiring the implementation of only an “open” dummy structure. Finally, results as good as those corresponding to using experimental data measured on open and short dummies are obtained up to 40 GHz.

Impedance matching for repetitive high voltage all-solid-state Marx generator and excimer DBD UV sources

The purpose of impedance matching for a Marx generator and DBD lamp is to limit the output current of the Marx generator, provide a large discharge current at ignition, and obtain fast voltage rising/falling edges and large overshoot. In this paper, different impedance matching circuits (series inductor, parallel capacitor, and series inductor combined with parallel capacitor) are analyzed. It demonstrates that a series inductor could limit the Marx current. However, the discharge current is also limited. A parallel capacitor could provide a large discharge current, but the Marx current is also enlarged. A series inductor combined with a parallel capacitor takes full advantage of the inductor and capacitor, and avoids their shortcomings. Therefore, it is a good solution. Experimental results match the theoretical analysis well and show that both the series inductor and parallel capacitor improve the performance of the system. However, the series inductor combined with the parallel capacitor has the best performance. Compared with driving the DBD lamp with a Marx generator directly, an increase of 97.3% in radiant power and an increase of 59.3% in system efficiency are achieved using this matching circuit.

A Short-Current Control Method for Constant Frequency Current-Fed Wireless Power Transfer Systems

Frequency drift is a serious problem in Current-Fed Wireless Power Transfer (WPT) systems. When the operating frequency is drifting from the inherent Zero Voltage Switching (ZVS) frequency of resonant network, large short currents will appear and damage the switches. In this paper, an inductance-dampening method is proposed to inhibit short currents and achieve constant-frequency operation. By adding a small auxiliary series inductance in the primary resonant network, short currents are greatly attenuated to a safe level. The operation principle and steady-state analysis of the system are provided. An overlapping time self-regulating circuit is designed to guarantee ZVS running. The range of auxiliary inductances is discussed and its critical value is calculated exactly. The design methodology is described and a design example is presented. Finally, a prototype is built and the experimental results verify the proposed method.

Analytical multi‐parametric stability boundaries of DC‐DC buck converters under V1 control concept

SummaryTwo main methods for controlling switching converters exist in the literature. The direct one is the voltage mode control, which suffers from some disadvantages such as slow response to load variations and an input voltage‐dependent total loop gain. The current mode control can overcome these problems but at the expense of extra cost and more complex control design. V1 concept is a new promising control technique for designing voltage mode control of buck‐type converters with an optimal response similar to current mode control. In this paper, the dynamics and the stability of buck converters under V1 control are studied. In particular, subharmonic oscillation limits in the parameter space are addressed. First, a closed‐loop state‐space model is derived and then used to formulate an analytical matrix‐form expression for predicting the stability limit of the system. Using this expression, multi‐parametric stability boundaries are obtained. It is shown that the equivalent series inductance of the output capacitor can narrow the stability region. It is also demonstrated that the integral action in the feedback loop of a V1‐controlled buck converter has a negligible effect on the subharmonic oscillation boundary. The theoretical analysis is validated through numerical simulation of the circuit‐level switched model of the system. Copyright © 2017 John Wiley & Sons, Ltd.

Improving Gold/Gold Microcontact Performance and Reliability Under Low-Frequency AC Through Circuit Loading

This paper investigates the performance and reliability of microcontacts under low-frequency and low-amplitude ac test conditions. Current microcontact theory is based on dc tests adapted to RF applications. To help better apply dc theory to RF applications, frequencies between 100 Hz to 100 kHz were experimentally investigated. Microcontacts designed to conduct performance and reliability measurements were used, which in prior dc testing typically lasted for 100 million cycles or more. Under ac loads, at similar power levels, eight devices were tested under cold-switching conditions, and only one was still operational at 10 million cycles. The effect of external circuitry on dc loaded devices was also considered. The experimental data were presented for dc conditions, which demonstrated that both a parallel capacitance with a microcontact and a series inductance were highly detrimental. For all six tested devices, failure occurred typically in 100 thousand cycles or less. However, utilizing series resistive/capacitive circuits as well as parallel resistor/inductive resulted in improved performance, with only one device of the four tested failing prematurely, but those that lasted showed less variation in measure contact resistance throughout the lifetime of the device. Two devices were tested with passive contact protection using parallel and series resistances, and both devices lasted for the full test duration. Finally, the effects of applying circuit protection to microcontacts and repeating ac test conditions were investigated. Reliability and device lifetime were extended significantly (9.1% success rate without protection was increased to 87% success rate). It was also observed in several instances that devices that failed showed subtle signs of variance during contact closure measurements in the range of 5–30 $\mu$ N, indicating a possible means for accurately predicting device failure. For these failed devices, notable physical damage was observed using a scanning electron microscope.

Effect of the Matching Circuit on the Electromechanical Characteristics of Sandwiched Piezoelectric Transducers.

The input electrical impedance behaves as a capacitive when a piezoelectric transducer is excited near its resonance frequency. In order to increase the energy transmission efficiency, a series or parallel inductor should be used to compensate the capacitive impedance of the piezoelectric transducer. In this paper, the effect of the series matching inductor on the electromechanical characteristics of the piezoelectric transducer is analyzed. The dependency of the resonance/anti-resonance frequency, the effective electromechanical coupling coefficient, the electrical quality factor and the electro-acoustical efficiency on the matching inductor is obtained. It is shown that apart from compensating the capacitive impedance of the piezoelectric transducer, the series matching inductor can also change the electromechanical characteristics of the piezoelectric transducer. When series matching inductor is increased, the resonance frequency is decreased and the anti-resonance unchanged; the effective electromechanical coupling coefficient is increased. For the electrical quality factor and the electroacoustic efficiency, the dependency on the matching inductor is different when the transducer is operated at the resonance and the anti-resonance frequency. The electromechanical characteristics of the piezoelectric transducer with series matching inductor are measured. It is shown that the theoretically predicted relationship between the electromechanical characteristics and the series matching inductor is in good agreement with the experimental results.

An On-Chip Electromagnetic Bandgap Structure with ESD Protection for Noise Suppression in 16-nm FinFET CMOS

By using periodical electromagnetic bandgap (EBG) structure, a wideband band-stop filter (BSF) with ESD protection is first realized in 16-nm FinFET CMOS technology for GHz-order noise suppression. The proposed EBG unit cell consists of an on-chip inductor in series with MOS capacitors and gated ESD diodes. The gated ESD diodes are not only used as ESD protection devices, but also co-designed with MOS capacitors and an inductor to form LC resonator for the BSF. The measurement results demonstrate TLP currents of 1.75 A and 1.35 A for the PDS and NDS modes, respectively, corresponding to a HBM ESD level over 2 kV. With the consideration of metal density rule for power/ground mesh, the on-chip EBG array presents a stopband of 15.5 GHz, from 4.5 to 20 GHz, with an isolation level of 30 dB.

High-Isolation CMOS T/R Switch Design Using a Two-Stage Equivalent Transmission Line Structure

A fully integrated Ku-band transmit/receive (T/R) switch based on a two-stage equivalent transmission line structure has been designed using a 180-nm complementary metal-oxide-semiconductor (CMOS) process. An analysis shows a relation between the series inductance and turn-on resistance for high isolation. A stack structure with feed-forward capacitors was chosen as a means of improving the power-handling capability of the switch. A low insertion loss (IL) of the switch was achieved by eliminating series transistors. The measured minimum ILs of the switch in the transmitter (TX) and receiver (RX) modes are 2.7 dB and 2.3 dB, respectively. The measured isolations in the TX and RX modes are greater than 34 and 25 dB, respectively, from 15 to 18 GHz. The design reaches a measured input 1-dB power compression point ( $IP_{1}dB$ ) of 22 dBm at 17 GHz. The switch achieves stringent isolation, insertion loss, and power-handling capability requirements along with the capability of full integration, demonstrating its great potential for use in fully integrated CMOS T/R chips.

Impact of Photo Voltaic Cells on Hybrid Microgrid

In order to reduce the green house gas emissions all over the world the investment on renewable energy infrastructure is increasing particularly in the distribution network. It is also observed that the power generated by distributed system is not only supplied through distribution system but also fed to the grid by appropriately transforming the voltage. It has the advantage that the power generated through distributed generation system is utilized in the grid for other users. The PV cell generates voltage at the distribution level. At the end of distribution line a 1 MVA three phase load is connected. In the absence of the generation from the PV cells, the voltages and currents at various lengths of the line are calculated with a single load of three phase 1 MVA. With the inclusion of PV cells, the improvement in voltage dip is also estimated. This estimate provides the power supplied by the PV cell and improvement in voltages. In order to determine the effect of additional load on voltage profile, a three phase load of 1 MVA was connected to intermediate point in the transmission system. This causes the dip in voltage at various nodes of the distribution line. Several combinations of source and loads have been examined to determine the effect on voltage and power. The above work has been carried out using Electro Magnetic Transient Program (EMTP), free version developed by university of British Columbia, Canada and made available through Indian EMTP user group. In order to simulate the system, 8.98 kV 5 km long line is divided into 5 sections of 1 km each. The sections are represented in the form of Pi-network by its series inductance, resistance and capacitance to ground. Loads are represented by R and L of appropriate magnitude and through EMTP program the calculations are done. The PV cell is represented by a source stepped up to 8.98 kV system. Both single phase and three phase lines have been examined through the above program. The results obtained for various conditions are presented in the paper.

Discussion on lightning impulse test waveform according to breakdown characteristics of SF6 gas gaps

The standard lightning impulse (LI), defined as a smooth full lightning impulse voltage having a front time of 1.2 μs and a time to half-value of 50 μs, obtained from field observation, has remained unchanged from IEC Ed. 1 in 1962 through to Ed. 3 in 2010. LI test plays an important role in the equipment design and insulation defects detection. In order to evaluate the reasonability of the standard LI waveform from the point of insulation characteristics, breakdown characteristics of GIS under LI with different wavefront times Tt and wavetail times Tt were studied. Those experimental results show that the LI waveform parameters have little influence on the breakdown characteristics of a sound GIS equipment, but have great influence on the GIS equipment with defects. For a highly inhomogeneous electric field, with the wavefront time increasing, the 50% breakdown voltages U50% have remarkable change and the U50%−Tt curve tends to be U-shaped. The 50% breakdown voltages decrease significantly with the increase of impulse wavetail time, especially when wavetail time is in the range of 1.5 to 15 μs, but the difference of the values decreases after 15 μs. Ignoring the generating possibility in the field for the large series inductance and load capacitance, a LI with wavefront time in the range of 0.2 to 0.7 μs is proposed in the field for it may increase the probability of detecting insulation defects. Finally, the polarity reversion phenomenon and critical radius phenomenon, observed from the breakdown characteristics, can be explained by the migration and diffusion of space charges.

EBG-based transmission lines with slow-wave characteristics and application to miniaturization of microwave components

In this paper, artificial transmission lines implemented by means of electromagnetic band gaps and consisting of a host line periodically loaded with reactive elements (either shunt capacitances or series inductances) are presented. The considered implementations are restricted to microstrip lines either loaded with patch capacitors or with inductive slots (etched in the ground plane). It is demonstrated that these structures are useful for device miniaturization due to the slow-wave effect associated with the presence of the reactive elements. A prototype device example consisting of a microstrip power divider implemented by means of a 35.35 Ω slow-wave impedance inverter with inductive slots is reported. It is shown that, by virtue of the slow-wave effect, the length of the inverter is reduced by a factor of two. The performance of the resulting power divider is comparable to the one based on an ordinary inverter. The possibility to suppress spurious (harmonic) bands by means of the Bragg effect is also discussed.

Improving Power Integrity by Using Magnetodielectric Absorbers Along the Perimeters of Printed Circuit Boards

Maintaining low and smooth impedance over a wide range of frequency is one of the main issues in designing high-speed digital systems or mixed signal integrated circuits. Cavity resonances of a printed circuit board coupled with discontinuous return current paths, series inductance of the power distribution network, and parasitic inductance make potentials at power/ground planes unstable. One possible solution to improve power integrity and electromagnetic interference is to utilize a magnetodielectric absorber on the perimeter of the board. A mode-matching method and an impedance boundary condition are employed to obtain a computationally inexpensive model of the system. A contour plot of transfer impedance versus normalized surface impedance is introduced to provide useful information for determining the most suitable absorber. Numerical and measurement results are discussed. The results from the proposed modeling agree with those from the measurement and the simulation. The selected absorber effectively reduces selfimpedance and transfer impedance at resonant frequencies, but resonances are not completely eliminated at low frequencies due to the low loss of the absorber.

On Practical Implementation of Electromagnetic Models of Lightning Return-Strokes

In electromagnetic models, the return-stroke channel is represented as an antenna excited at its base by either a voltage or a current source. To adjust the speed of the current pulse propagating in the channel to available optical observations, different representations for the return-stroke channel have been proposed in the literature using different techniques to artificially reduce the propagation speed of the current pulse to values consistent with observations. In this paper, we present an analysis of the available electromagnetic models in terms of their practical implementation. Criteria used for the analysis are the ease of implementation of the models, the numerical accuracy and the needed computer resources, as well as their ability to reproduce a desired value for the speed of the return stroke current pulse. Using the CST-MWS software, which is based on the time-domain finite-integration technique, different electromagnetic models were analyzed, namely (A) a wire embedded in a fictitious half-space dielectric medium (other than air), (B) a wire embedded in a fictitious coating with permittivity (εr) and permeability (μr), and (C) a wire in free-space loaded by distributed series inductance and resistance. It is shown that, by adjusting the parameters of each model, it is possible to reproduce a desired value for the speed of the current pulse. For each of the considered models, we determined the values for the adjustable parameters that allow obtaining the desired value of the return speed. Model A is the least expensive in terms of computing resources. However, it requires two simulation runs to obtain the electromagnetic fields. A variant of Model B that includes a fictitious dielectric/ferromagnetic coating is found to be more efficient to control the current speed along the channel than using only a dielectric coating. On the other hand, this model requires an increased number of mesh cells, resulting in higher memory and computational time. The presence of an inhomogeneous medium generates, in addition, unphysical fluctuations on the resulting current distributions. These fluctuations, which strongly depend on the size of the coating as well as on its electric and magnetic properties, can be attenuated by considering conductive losses in the coating. Considering the efficiency in terms of the required computer resources and ease of implementation, we recommend the use of Model C (wire loaded by distributed inductance and resistance).

Development and Simulation of a Compact Picosecond Pulse Generator Based on Avalanche Transistorized Marx Circuit and Microstrip Transmission Theory

The new biological effect of picosecond pulsed electric fields (psPEFs) has elicited the interest of researchers. A pulse generator based on an avalanche transistorized Marx circuit has been proposed. However, the problem of reflection in the transmission of the generated picosecond pulse based on this circuit has not received much attention and remains unresolved. In this paper, a compact picosecond pulse generator based on microstrip transmission theory was developed. A partial matching model based on microstrip transmission line theory was also proposed to eliminate reflection, and a series inductor was utilized to optimize pulse waveform. Through simulation studies and preliminary experimental tests, a pulse optimized with 1015 V amplitude, 620-ps width, and 10-kHz high stability repetition rate was generated. This pulse generator can be used with microelectrodes in cell experiments to explore the biological effect mechanism of psPEF.

Bootstrap Voltage and Dead Time Behavior in GaN DC–DC Buck Converter With a Negative Gate Voltage

The low threshold voltage of Gallium Nitride enhancement mode FETs is a concern in synchronous dc–dc buck converters. This paper presents a converter using a gate drive with a negative biased gate voltage on the low-side FET to improve the dV / dt robustness. The resulting much larger voltage drop during the dead time conduction is a concern as it can quickly overcharge the bootstrap capacitor voltage. This paper demonstrates that with a negative biased gate voltage, the rise in the bootstrap capacitor voltage is predominantly caused by the change in effective dead time conduction due to a variation in output load. A spice model to estimate the change is presented and verified. This paper also found that a change in the bootstrap capacitor voltage must be prevented as it leads to a significant change in turn-on dynamics, resulting in higher dV / dt stress with an increase in output load. To prevent a change in bootstrap capacitor voltage, different techniques such as Zener diode clamping and an external free-wheeling Schottky diode are tested and discussed. Finally, a modification of a standard bootstrap circuit using a series inductor is proposed and tested. It has been found to be the most effective method in preventing a variation in the bootstrap capacitor voltage and should be included when using a negative gate drive in a GaN dc–dc buck converter.