Impedance Results Research Articles

Design of a Wide Planar Waveguide Antenna for UHF Near-Field RFID Reader With High Reading Rate

UHF near-field RFID reader antenna based on leaky waveguide is proposed and the performance is evaluated using numerical simulation and experiment. In order to suppress the standing wave along transverse direction, a pair of notches is placed on the transverse edge of the mesh layer of the planar waveguide. Diversity operation by switching impedance of the end terminal of the planar waveguide antenna is also introduced to suppress the standing wave effect along longitudinal direction. Numerical simulation and experiment show that the near-field null lines parallel to the longitudinal direction is almost removed by the presence of the notches and the distribution of the field strength becomes almost uniform because of the utilization of the switching diversity. It is demonstrated that the reading performance of the commercial RFID tags is greatly improved by using the proposed RFID reader antenna with the diversity operation of termination impedance.

Modeling of Input Nonlinearity and Waveform Engineered High-Efficiency Class-F Power Amplifiers

A comprehensive time-domain modeling and a generalized design methodology for input and output waveform engineered Class-F power amplifiers (PAs) are presented in this article. A closed-form relationship between input nonlinearity and second harmonic source impedance ( $Z_{\mathrm {2S}}$ ) termination is presented from which efficiency and output power performance are predicted for Class-F PAs. The maximum, minimum, and safe $Z_{\mathrm {2S}}$ design space for a Class-F PA are identified. Moreover, the derived design equations show that the typical fundamental load of a Class-F PA operation must be re-engineered in the presence of input nonlinearity in order to achieve optimum efficiency performance. The theoretical analyses are first validated with pulsed vector load–pull (VLP) measurements with a gallium nitride (GaN) 2 mm device. Then, high-power (210 W) GaN 24-mm devices with in-package $Z_{\mathrm {2S}}$ terminations are implemented. Measurement results with the new source and load design space show efficiency improvement of 4.4% compared to the nominal Class-F PA.

Analytical expression for estimation of the fault location in cable line

A new method for the fault location in a short cable line is proposed in this study. Based on the transmission line theory and circuit theorems, an analytical expression for estimating the fault location in the cable line is derived. According to the problem of incorrect estimation in the high-frequency band, the corresponding essential reason is comprehensively explained. By solving this problem, the fault location can be obtained accurately by the proposed method. To validate the proposed method, some experiments with a 50 Ω coaxial cable are implemented and the accuracy of the proposed method is tested. Meanwhile, it has been validated in these experiments that the proposed method is independent of the fault impedance and terminal impedances.

Advanced Mixed Signal Concepts Exploiting the Strong Body-Bias Effect in CMOS 22FDX®

In this article, an overview of the most recent fully-depleted silicon on insulator technology (FD-SOI) design techniques in the field of mixed-signal circuits and systems are given. Cutting edge performance is achieved by using dynamic as well as static body-biasing techniques. 22FDX <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> is a 22nm CMOS FD-SOI technology providing both, a unique wide-band body-bias tuning range in conjunction with minimized parasitic device loads, due to the significant reduced pn junctions in the signal path. As a result, transistor transit frequencies exceeding 400GHz with improved linearity is achieved. With a linear threshold voltage sensitivity of around 75mV per Volt, 22FDX <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> gives designers a competitive additional degree of freedom. After introducing 22FDX <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> , a 5-bit 18.5GS/s flash ADC is presented utilizing body-biasing to generate accurate threshold voltage offsets within the comparators and thus omitting a power-hungry resistive ladder. Then, dynamic body-biasing is used for a 1.5GS/s track-and-hold circuit to improve the bandwidth while the leakage is reduced obtaining 80dBc SFDR up to the fourth Nyquist zone. Furthermore, a 26GHz ring oscillator is presented, which utilize the strong threshold voltage sensitivity to fully compensate corner dependency. Finally, a body-biasing controlled DAC linearization technique for multi-bit Sigma-Delta modulators enabling 90dBc SFDR, as well as a DAC driver termination impedance control for a 6GS/s 10-bit automotive Ethernet SST-DAC-Driver are presented.

A reconfigurable analog predistorter using tunable impendence matching network

A reconfigurable analog predistoter (APD) based on tunable impedance matching network (TIMN) is proposed in this brief. Firstly, a design method to specific gain and phase conversions is introduced. The equivalent circuit parameters of the impedance matching network (IMN) can be computed for the desired gain and phase conversions. To simplify the design, these parameters can be transformed to the terminal impedance of the IMN. Then the complicated nonlinear circuits design can be transformed to the IMN design. Secondly, a reconfigurable APD using the proposed method is presented for high tuning capability. By designing the coverage area of the TIMN, an experimental reconfigurable APD for traveling-wave tube amplifiers (TWTAs) & solid-state power amplifiers (SSPAs) is designed and fabricated. The fabricated APD shows more than 21 dB tuning range of gain conversion and 114° tuning range of phase conversion in 5.7–6.3 GHz. Good linearity improvement has been obtained for a 45 W C-band TWTA and a 5 W SSPA only by changing the APD bias voltage.

Parallel Control Method of Microgrid Inverter Based on Adaptive Droop Control

Energy is the driving force of social and economic development. With the gradual depletion of conventional energy and the increasingly prominent ecological and environmental problems, the power industry needs to find a sustainable development path. Parallel control of microgrid inverters based on adaptive droop control is an important part of future intelligent and sustainable power systems. However, with the continuous increase of power generation equipment capacity and the continuous increase of load power consumption, the form of power supply by a single inverter can no longer meet the requirements. Therefore, parallel connection of multiple inverters has been widely used in the microgrid. In this paper, a set of parallel control methods for microgrid inverters based on adaptive droop control is established. This paper is based on the inductance of the inverter’s terminal impedance, and the amplitude of the inverter terminal voltage is positively correlated with the output reactive power and has a strong correlation It is concluded that the microgrid based on adaptive droop control has the ability to automatically adjust the voltage and frequency of the microgrid. Properly reducing the droop coefficient can improve the primary frequency modulation capability of the microgrid. In this paper, an improved resistive control equation is used in a parallel system, a multi-loop control structure with a quasi-resonant controller is used for the inverter in the parallel system, and a virtual complex impedance is added to perform small signal analysis on the improved resistive control equation The overall performance of the parallel system is analyzed, and the effect of different control coefficients on the system performance is clarified. The experimental research results show that when analyzing the effect of the inductance coefficient value on the equivalent output impedance in the virtual complex impedance, the value of KL is 1 At this time, the equivalent output impedance becomes resistive again, and the property is stronger than when KL is 0.05.

On the Design of Low-Power Hybrids for Full Duplex Simultaneous Bidirectional Signaling Links

This paper investigates the suitability of full duplex simultaneous bidirectional (FD-SBD) signaling as a method to theoretically double the aggregate data transfer per pin for ultra-short-reach links. Advantages as well as challenges associated with differential FD-SBD links are described, and comparisons are made with single-ended and multilevel signaling schemes. FD-SBD links require a hybrid to recover the weak received signal from the large self-interfering transmitted signal. After providing a summary of prior-art high-speed hybrids, which often utilize replica drivers and current-mode signaling, two voltage-mode hybrids are presented and compared to enable low-power FD-SBD links at high data rates without using any replica drivers. This includes an R- $G_{m}$ driver, as well as a resistor-bridge driver derived from a Wheatstone-bridge. It is shown that maintaining a uniform termination impedance is important to support FD-SBD signaling on low insertion-loss links. Accordingly, a resistor-bridge hybrid utilizing an averaging resistor embedded in the output transimpedance amplifier based voltage-mode driver is implemented. A prototype implemented in a 65 nm CMOS process is measured within a transceiver front-end at an aggregate data rate of 15 Gb/s over a short differential channel with 2.5 dB insertion loss at 3.75 GHz on a 4-layer FR4 PCB. The energy/bit for the transceiver front-end is 1.35 pJ/b at an aggregate data rate of 15 Gb/s.

Design of Compact Coupled-Line Complex Impedance Transformers With the Series Susceptance Component

In this brief, a compact coupled-line complex impedance transformer (CIT) with a series susceptance component is presented. It is composed of a coupled line and a susceptance component series at the edges of the coupled line. By inserting the susceptance component, arbitrary complex impedance can be transformed and the coupled line has weak coupling coefficient and small impedance value, which shows the feature of compact, easy fabrication and size miniaturization. The design equations for the proposed CIT are derived by using the port voltage-current method combined with the even-odd mode decomposition technology. For verification, two prototypes are designed at 1.0 GHz. The measured results demonstrate that good impedance matching is obtained by the proposed CIT with arbitrary terminal impedances.

Simulation of bronchial airway acoustics in healthy and asthmatic subjects.

The onset and development of many airway pathologies affect sound propagation throughout the respiratory system; changes in respiratory sounds are detected primarily by auscultation, which is highly skill dependent. The aim of the present study was to compare healthy and asthmatic pulmonary acoustics by applying a 1D model of wave propagation on CT-based patient-specific geometries. High-resolution CT lung images were acquired in five healthy volunteers and five asthmatic patients at total lung capacity (TLC) and functional residual capacity (FRC). Tracheobronchial trees were reconstructed from CT images. Acoustic pressure, impedance and wall radial velocity were measured by simulating acoustic wave propagation of two external, acoustic pressure waves (1 Pa, 200 and 600 Hz) from the trachea level to the 4th generation. In asthmatic patients, acoustic pressure averaged across the last three generations showed a reduction equal to 29.7% (p<0.01) at FRC, at 200 Hz; input and terminal impedance were 34.5% (p<0.05) higher both at FRC and TLC; wall radial velocity was more than 80% (p<0.05) lower in higher generations both at FRC and TLC. Airway differences in asthma alter acoustic parameters at FRC and TLC, with the greatest difference at FRC and 200 Hz. Acoustic wave propagation analysis represents a quantitative approach that has potential to objectively characterize airway differences in individuals with diseases such as asthma.

A Novel Microstrip Line Balun With Transparent Port Impedance and Flexible Open Arm Structure

In this letter, a novel microstrip line balun with transparent port impedance and unconnected flexible output arms is presented. The proposed balun is designed from a symmetric four-port device with an open end at its isolation port. To achieve balun function, a shunt stub is attached between the unbalanced port and the virtual open-ended port to generate a transmission zero under the even-mode circuit. Its odd-mode circuit is treated as an impedance transformer, where the transformer is independent of the terminal impedance. In addition, the proposed balun has flexible open arm branches and does not require a closed loop structure, which provides design flexibility to integrate with other devices compared to conventional closed-loop branch line baluns. The theoretical design equations are derived first to prove the design concept. Then, two prototypes are designed with 35 $\Omega $ system impedance and loaded with 50 and 75 $\Omega $ port impedance, and the measured results match well with the simulation, which further validates the proposed design theory.

Notice of Retraction: Comments on “A Modified Gysel Power Divider of Arbitrary Power Ratio and Real Termination Impedances”

Without fully understanding the previous works of asymmetric ring hybrids terminated in arbitrary real impedances, it is insisted that the Gysel power dividers terminated in arbitrary real impedances should be first reported in the above article. However, the claim does not seem to be correct. The misinterpreted concept will be clarified.

Failure Mechanism of Avalanche Condition for 1200-V Double Trench SiC MOSFET

Due to superior properties of silicon carbide (SiC), the unipolar conduction mechanism of metal-oxide-semiconductor-field-effect transistor (MOSFET), and the structural feature, double trench SiC MOSFETs have great potential to be one of the next-generation power switches. In this article, an avalanche safe operation area (SOA) is established, and a new failure behavior of 1200-V double trench SiC MOSFET is revealed timely through unclamped inductive switching (UIS) test (300 K of initial temperature). With comprehensive analyses involving terminal impedance measurement, monitoring of V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> and I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gss</sub> before and after each avalanche test, inner electric field comparison by physics-based device modeling, maximum die temperature estimation, and decapsulation validation, the predominant failure mechanism (fracture of trench gate oxide) is identified for double trench SiC MOSFET under UIS test. Before the maximum die temperature approaches the melting point of source metal, the fracture of the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer located at gate trench bottom and corner occurs, which is degraded by duration, excessive electric field, and elevated temperature. Accordingly, we propose I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gss</sub> as a predicting indicator of avalanche failure, which should be a key monitoring scheme in particular for trench type SiC MOSFET.

MR safety watchdog for active catheters: Wireless impedance control with real-time feedback.

To dynamically minimize radiofrequency (RF)-induced heating of an active catheter through an automatic change of the termination impedance. A prototype wireless module was designed that modifies the input impedance of an active catheter to keep the temperature rise during MRI below a threshold, ΔTmax . The wireless module (MR safety watchdog; MRsWD) measures the local temperature at the catheter tip using either a built-in thermistor or external data from a fiber-optical thermometer. It automatically changes the catheter input impedance until the temperature rise during MRI is minimized. If ΔTmax is exceeded, RF transmission is blocked by a feedback system. The thermistor and fiber-optical thermometer provided consistent temperature data in a phantom experiment. During MRI, the MRsWD was able to reduce the maximum temperature rise by 25% when operated in real-time feedback mode. This study demonstrates the technical feasibility of an MRsWD as an alternative or complementary approach to reduce RF-induced heating of active interventional devices. The automatic MRsWD can reduce heating using direct temperature measurements at the tip of the catheter. Given that temperature measurements are intrinsically slow, for a clinical implementation, a faster feedback parameter would be required such as the RF currents along the catheter or scattered electric fields at the tip.

A New Design Methodology for Wideband Analog Predistorter With the Characteristics of Frequency-Dependent Gain and Phase Conversions

A novel design method, which can transform the nonlinear circuits design to the impedance matching network (IMN) design, is proposed for wideband analog predistoter (APD) with the characteristics of frequency-dependent gain and phase conversions in this paper. First, the design method for the desired gain and phase conversions is introduced. The ABCD parameters of the IMN can be computed. To simplify the design, the obtained parameters are transformed to the IMN terminal impedance. Then we can only need to design the IMN terminal impedance to obtain the desired transfer characteristics. In the meanwhile, an APD with 4.5 dB gain conversion and 50° phase conversion is designed and simulated to validate the design method for specify gain and phase conversions. The simulated results show good effectiveness of the design method. Second, for wideband application, the complex gain and phase conversions surface design is transformed to the IMN terminal impendence curve versus frequency design. This gives the designers a well-defined strategy for wideband APD design focusing on frequency-dependent phase conversion as well as gain conversion. To validate the proposed method, a wideband APD operating at K-band (17-20 GHz) is designed, fabricated and measured. A linearized 100W K-band TWTA is shown to achieve a noise power ratio (NPR) >20 dB at 3 dB output power back-off, and phase change <; 6.5° among the operating band.

Generalized Symmetrical 3 dB Power Dividers With Complex Termination Impedances

The paper introduces a class of two-way, 3 dB narrowband power dividers (combiners), closed on complex termination impedances, that generalizes a number of topologies presented during past years as extensions of the traditional Wilkinson design. Adopting even-odd mode analysis, we demonstrate that, under very broad assumptions, any axially symmetric reactive 3-port can be designed to operate as a 3 dB two-way power divider, by connecting a properly designed isolation impedance across two symmetrically but arbitrarily located additional ports. We show that this isolation element can be evaluated by a single input impedance or admittance CAD simulation or measurement; moreover, an explicit expression is given for the isolation impedance. The theory is shown to lead to the same design as for already presented generalizations of the Wilkinson divider; further validation is provided through both simulated and experimental case studies, and an application of the theory to the design of broadband or multi-band couplers is suggested.

Preanodized Screen Printed Carbon Electrode for Detection of Linalool using Three Terminal Network

Linalool is a very important flavouring compound found in plants which is used in food and beverages. Linalool has been traditionally detected by analytical instruments such as gas chromatography (GC) coupled with mass spectroscopy(MS) which are not suitable for routine tests. For fast and low cost detection of chemical compounds electrochemial sensors are most suitable. Screen printed carbon electrode (SPCE) is one of the most popular and low cost device used for detection of chemical compounds. In this article we present the detection of linalool using a low cost preannodized commercial screen printed carbon electrode (SPCE). Traditionally electrochemical sensors are used in two terminal mode, however three terminal analysis of electrochemical sensors are found to be more rationale and accurate. In this paper we have analyzed detection of linalool by an advanced three terminal analysis. First we have performed cyclic voltammetry(CV) of the SPCE which showed clear oxidation peaks at different concentration of linalool. The input-output data of the CV has been used for analysis of the impedance of the SPCE.The impedance model of the SPCE was estimated by autoregressive moving average with exogenous inputs(ARMAX) modelling technique using the CV data. The three terminal impedance fitting revealed the values of electrical parameters and the parasitic elements at different linalool concentration. The stability limits of the SPCE was also determined from the pole-zero and Nyquist plots of the estimated models. Impedance behaviour to frequency of the SPCE was further analyzed by impedance plot( 𝒁 vs −𝒁 ′ ) from which we are able to relate the CV scan rate to the impedance of the SPCE. Finally the sensitivity and repeatability of the SPCE was determined using a measurement circuit.

A Novel Compact Isolation Circuit Suitable for Ultracompact and Wideband Marchand Baluns

A novel compact isolation circuit (IC) is proposed for the ultracompact and wideband UHF Marchand balun topology, and exact design formulas are presented for arbitrary coupling coefficients and impedance-transforming termination impedances. The wideband Marchand balun mainly consists of two identical coupled transmission-line sections which are far shorter than 90° long, connecting segment, two or three lumped elements and the proposed IC. The novel IC features −180° phase delay between two balanced ports, and makes the ultracompact implementation possible, which is quite different from the conventional ones with 180° phase delays between two balanced ports. In addition, due to the −180° phase delays, excellent isolation performance and excellent phase responses can be performed. For the proof-of-concept demonstrations, one prototype with each coupled-line section being only 20° long and the half IC being only 20° long is tested at 700 MHz. The measured frequency responses are in good agreement with the predicted ones with the performance of the 10-dB return loss bandwidth of 40% and −15 dB isolation bandwidth of 121.4%. In terms of sizes versus bandwidths, the fabricated Marchand balun can be regarded as the best and the smallest ever recorded, based on the low-cost microstrip technology.

Impact of the Input Baseband Terminations on the Efficiency of Wideband Power Amplifiers Under Concurrent Band Operation

This article presents a theoretical explanation of the efficiency degradation in wideband radio frequency power amplifiers (RFPAs) under concurrent dual-band operation that is still visible after eliminating all known causes related to the output matching network (OMN). First, the origin of this degradation, identified by the reduction of the PA’s efficiency and linearity, is traced to the input baseband impedance terminations. Then, a theoretical model that describes the phenomenon and qualitatively predicts the efficiency variation under concurrent dual-band operation is presented using a simple model based on two-tone excitation. Finally, the proposed explanation is confirmed by comparing the efficiency performance of two 30-W GaN RFPAs of distinct instantaneous bandwidth determined by different input video-bandwidth terminations, under two-tone and concurrent dual-band operation. This article shows that, in addition to the adequate OMN design, an optimal input baseband impedance profile is also an important design constraint needed to keep the efficiency and linearity performance of RFPAs, for scenarios that require a wide instantaneous bandwidth.

Modeling and Analysis of DC Terminal Impedance of Voltage-Source Converters With Different Control Modes

A dc terminal impedance model of voltage-source converter (VSC) is required to analyze the stability of multiterminal high-voltage direct current system. This article proposes a comprehensive dc terminal impedance model for conventional three-phase two-level VSC under different control modes. The control strategy includes inner decoupled current control and outer control, the latter contains dc voltage control, active/reactive power control, and droop control for grid-connected VSC and ac voltage control for VSC connected to a load. When a VSC is connected to the ac grid, the phase-locked loop (PLL) is also taken into account. The influences of PLL dynamics, control time delay and dead time on the dc-side impedance are explained. Also, how the parameters of the inner current control and outer control affect the characteristics of dc terminal impedance is analyzed in detail. Finally, experimental measurements verify the proposed impedance models and analysis.

High-power traveling-wave photodetector based on an aperiodically loaded open-circuit electrode.

We demonstrate a four-stage silicon distributed traveling-wave photodetector (TWPD) whose input terminal is open-circuit so as to enhance the radio-frequency (RF) output power. In order to mitigate the bandwidth drop caused by the RF reflection at the open input terminal, photodetector (PD) units are aperiodically loaded on the TW electrode. With the aid of an equivalent circuit model, we optimize spacings between PD units and then improve the 3dB bandwidth from 7 to 10GHz. A good agreement between measurement and modeling is obtained. Thanks to the cancellation of the input termination impedance, maximum RF output powers of the device are 10.2 and 6.5dBm at 5 and 10GHz, respectively. The corresponding power conversion efficiencies are 7.0% and 3.2%.