Resistive Termination Research Articles

On-Chip Temperature Distribution of Josephson Voltage Standard Devices

A substrate surface temperature characterization for the National Institute of Standards and Technology Josephson voltage standard has been performed by fabricating and measuring Josephson junction arrays with on-chip thermometry. Circuits were designed with a single voltage standard style array consisting of 12 810 junctions. 31 banks of thermometer junctions were placed around the array and microwave termination resistor to monitor temperature via a junction critical current measurement. Temperature rise in devices with on-chip termination resistors were compared to that of devices terminated off-chip. The thermal profiles on several different substrates were measured and compared to determine which substrate exhibited the best thermal transport. Finally, the thermal properties of junctions deposited directly on silicon were compared to those of the junctions deposited on an interface layer. We found that devices with off-chip terminations had half the temperature rise compared to the devices with on-chip termination, and the devices with remotely located terminations exhibited larger constant-voltage steps over a larger frequency/power range than the devices with termination resistors very close to array junctions. Comparing substrates, we found that sapphire was best for transporting heat from voltage standard circuits and that an interface layer did not affect heat transport in the substrate.

Investigation of HTS CrossConductor Joints, Connectors, and Terminations

The high-temperature superconductor (HTS) CrossConductor (HTS CroCo) is a modified stacked-tape arrangement, aiming for high current density and easy long-length fabrication. It is intended to be used as a strand for a high current cable in industrial dc applications or large high-field magnets. In order to allow for an economical operation, terminations, joints, and connector parts need to be sufficiently low-resistive to minimize the heat generation and thus the cooling cost. On the other hand, industrial applicability requires reliable and easy-to-use concepts. In this paper, three approaches to fabricate soldered joints and terminations for HTS CroCos are presented and assessed based on resistance measurements at 77 K, self-field. Termination resistances of some tens of nano-Ohms were achieved for the best termination concepts. Additionally, four types of low-resistive HTS CroCo connectors with bending radii of less than 5 cm are introduced and assessed. For the best connector types, some tens of nano-Ohms were achieved giving rise to a heat generation of less than 1 W at operating conditions.

An Enhanced Patient-Specific Computer Model Using an Iterative Multi-Staged Algorithm

Background: A previously introduced patient-specific computer model was applied to predict outcomes of the balloon occlusion test (BOT). The goal of this work was to propose an enhanced patient-specific computer model using a new iterative multi-staged algorithm. Method: This work presents an enhanced patient-specific computer model which converts several more terminals from generic, to patient-specific, resistances and also makes the aortic pressure and the stiffness coefficient patient-specific. A new iterative multi-staged algorithm is proposed to determine the terminal resistances, the aortic pressure, and the stiffness coefficient using vessel sizes and vessel flows measured by quantitative magnetic resonance angiography (qMRA) and cuff pressure. The predictions of the BOT were also evaluated for the validation of the proposed model. Results: The predictions from the proposed model were accurate in comparison with the clinical outcomes of the two BOTs. The computed stiffness coefficients were consistent with the ages of the two patients. The correlation coefficients between the flow measurements and the computed flows using the proposed computer model at baseline for the two patients were 0.9861 and 0.9995, respectively. The computed aortic pressures were also comparable in waveform shape with the actual aortic pressure measurements obtained during the BOT using a catheter-transducer. Conclusion: The present study makes the computer model more patient-specific with a new algorithm using non-invasive data from qMRA and cuff pressure. The six more sectors have made the terminal resistances more patient-specific. The patient-specific aortic pressure has made the forcing function patient-specific. And the stiffness coefficient has made the compliance patient-specific. J Neurol Res. 2017;7(3):25-38 doi: https://doi.org/10.14740/jnr435w

Comments on “An Analytical Design Method for a Novel Dual-Band Unequal Coupler With Four Arbitrary Terminated Resistances”

IN the above paper [1], the authors proposed a dual-band unequal power division branch line coupler(BLC) with four arbitrary terminated resistance using dual-band impedance matching network (IMN) and BLC with complex port impedance. However the authors have not considered the transmission phase of the IMNs [2] and the BLC, which leads to non-quadrature phase difference (6 S21􀀀6 S31 6= 90) at the output ports when the termination resistances are unequal.

Balanced RF Rectifier for Energy Recovery With Minimized Input Impedance Variation

A balanced RF rectifier is proposed to replace terminations in microwave circuits and thus to recycle the otherwise dissipated power in resistances. In order not to degrade the performance of the original circuits, a balanced configuration is adopted because it minimizes the variation of input impedance of the rectification circuitry. This approach achieves good input reflection coefficient over a large dynamic range and operating frequencies. The highly efficient energy recycler is composed of a 3 dB quadrature coupler and two identical RF rectifiers. The impact of amplitude and phase imbalances of the transfer characteristics of the coupler is discussed. Furthermore, an arbitrary-port-resistance coupler is studied to replace non-50- $\Omega $ terminations. The experimental verification demonstrates that the proposed circuit provides an input reflection coefficient of better than −15 dB from 2.2 to 2.5GHz over different input power levels. The measured peak RF-to-dc efficiency is 74.9% at 2.34 GHz with $S_{11} = -24\,\mbox {dB}$ . The proposed balanced rectifier thus significantly improves $S_{11}$ over existing rectifiers and is therefore suitable for replacing resistive terminations in a large variety of circuits.

Capacitive cancellation technique in design of CMOS low noise amplifier for ultrasound applications

In this paper active capacitive cancellation technique, is proposed for alleviating the side effects of the parasitic capacitance of the ultrasound piezoelectric probe and cable. This parasitic capacitance imposes a low frequency pole at the input of the circuit, which deteriorates the noise and the transient response of the circuit, crucial parameters for ultrasound imaging systems. Employing a capacitor in a positive feedback loop of a well-defined gain amplifier actively cancels the parasitic capacitance at the input of the amplifier. Making use a binary weighted capacitor bank keeps the circuit safely away from the instability problems due to the variations of process and corner cases. For verification of the proposed technique, the circuit was designed and simulated in a 0.18 µm, 1.8 V CMOS technology. Simulation results show that this technique for equal power consumption presents a better noise performance and more than 100% higher bandwidth compared to the conventional active resistive termination approach.

A gating grid driver for time projection chambers

A simple but novel driver system has been developed to operate the wire gating grid of a Time Projection Chamber (TPC). This system connects the wires of the gating grid to its driver via low impedance transmission lines. When the gating grid is open, all wires have the same voltage allowing drift electrons, produced by the ionization of the detector gas molecules, to pass through to the anode wires. When the grid is closed, the wires have alternating higher and lower voltages causing the drift electrons to terminate at the more positive wires. Rapid opening of the gating grid with low pickup noise is achieved by quickly shorting the positive and negative wires to attain the average bias potential with N-type and P-type MOSFET switches. The circuit analysis and simulation software SPICE shows that the driver restores the gating grid voltage to 90% of the opening voltage in less than 0.20µs, for small values of the termination resistors. When tested in the experimental environment of a time projection chamber larger termination resistors were chosen so that the driver opens the gating grid in 0.35µs. In each case, opening time is basically characterized by the RC constant given by the resistance of the switches and terminating resistors and the capacitance of the gating grid and its transmission line. By adding a second pair of N-type and P-type MOSFET switches, the gating grid is closed by restoring 99% of the original charges to the wires within 3µs.

A 50 MHz ~ 10 GHz, 3.3 dB NF, +6 dBm IIP3 resistive feedback common source amplifier for cognitive radio application

Cognitive radio is a smart ultra-wideband wireless communication system that is capable of optimizing the usage of the available frequency spectrum. In this work, an ultra-wideband low noise amplifier with an operating bandwidth from 50MHz to 10GHz with integrated resistive feedback and π-matching network is presented. The amplifier is designed to self-bias via the feedback path to optimize the chip area consumption. The input signal is sourced to two common-source amplifiers to achieve the input matching configuration and subsequently cascaded to another common source amplifier with resistive termination in achieving the output matching. On-chip inductors were adapted to improve the high frequency response and to extend the bandwidth up to 10GHz. Measured results show that the input and output matching are better than −10dB with a gain variation of 10.32–13.28dB, noise figure variation of 3.29–6dB, and a third order intercept point ranging from −3.2 to +6dBm in a frequency span of 50–10GHz on a CMOS 0.13µm platform. The physical layout occupies 0.77mm2 chip area with the bondpads intact and consumes 31.2mW of DC power from 1.2V DC supply headroom.

A wideband, sensitive current sensor employing transimpedance amplifier as interface to Rogowski coil

In this paper a new method to increase the bandwidth of Rogowski current sensors is presented. Instead of using a termination resistor, in the proposed method a simple circuit based on transimpedance amplifier is used to suppress the parasitic capacitance of the coil. Using the lumped model of Rogowski coil, bandwidth, gain, and noise of the proposed current sensor is analyzed. The analyses are validated by both simulation and measurement results. Measurement of the proposed circuit demonstrates that without having any special coil design, a bandwidth close to 12MHz can be achieved, using a simple circuit with off-the-shelf electronic components.

Assessment of reduced-order unscented Kalman filter for parameter identification in 1-dimensional blood flow models using experimental data.

This work presents a detailed investigation of a parameter estimation approach on the basis of the reduced-order unscented Kalman filter (ROUKF) in the context of 1-dimensional blood flow models. In particular, the main aims of this study are (1) to investigate the effects of using real measurements versus synthetic data for the estimation procedure (i.e., numerical results of the same in silico model, perturbed with noise) and (2) to identify potential difficulties and limitations of the approach in clinically realistic applications to assess the applicability of the filter to such setups. For these purposes, the present numerical study is based on a recently published in vitro model of the arterial network, for which experimental flow and pressure measurements are available at few selected locations. To mimic clinically relevant situations, we focus on the estimation of terminal resistances and arterial wall parameters related to vessel mechanics (Young's modulus and wall thickness) using few experimental observations (at most a single pressure or flow measurement per vessel). In all cases, we first perform a theoretical identifiability analysis on the basis of the generalized sensitivity function, comparing then the results owith the ROUKF, using either synthetic or experimental data, to results obtained using reference parameters and to available measurements.

Low Cross-Polarization Gaussian Tapered Post-Wall Slotline Antenna for Short Pulse Applications

A Gaussian tapered slot antenna based on post-wall structured slotline for improvement of cross-polarization for ultra-wideband applications is proposed and experimentally demonstrated. The antenna is composed of two pairs of Gaussian tapered slotline which have the same structure printed on both sides of the PCB, two metallic via arrays positioned along the slot edges, and two terminal resistors. The metallic via arrays are used to reduce the characteristic impedance of the conventional slotline which form a post-wall slotline and thus can be fed by a coaxial connector directly. More importantly, the balanced symmetrical post-wall structure ensures low cross-polarization levels of the antenna. The Gaussian tapered edges and the terminal resistors diminish reflected signal and thus can enlarge the bandwidth significantly. Good agreements between the simulated and the measured results have been observed. Results show that the proposed antenna exhibits a −10 dB impedance bandwidth from 1.5 GHz to 20 GHz, a maximum realized gain of 12 dBi, and the broadside cross-polarization level is averaged about −32 dB in the lower frequency band and −25 dB in the higher frequency band with a maximum value of −22 dB in the whole working frequency band.

An Enhanced Patient-Specific Computer Model Using an Iterative Multi-Staged Algorithm

Background: A previously introduced patient-specific computer model was applied to predict outcomes of the balloon occlusion test (BOT). The goal of this work was to propose an enhanced patient-specific computer model using a new iterative multi-staged algorithm. Method: This work presents an enhanced patient-specific computer model which converts several more terminals from generic, to patient-specific, resistances and also makes the aortic pressure and the stiffness coefficient patient-specific. A new iterative multi-staged algorithm is proposed to determine the terminal resistances, the aortic pressure, and the stiffness coefficient using vessel sizes and vessel flows measured by quantitative magnetic resonance angiography (qMRA) and cuff pressure. The predictions of the BOT were also evaluated for the validation of the proposed model. Results: The predictions from the proposed model were accurate in comparison with the clinical outcomes of the two BOTs. The computed stiffness coefficients were consistent with the ages of the two patients. The correlation coefficients between the flow measurements and the computed flows using the proposed computer model at baseline for the two patients were 0.9861 and 0.9995, respectively. The computed aortic pressures were also comparable in waveform shape with the actual aortic pressure measurements obtained during the BOT using a catheter-transducer. Conclusion: The present study makes the computer model more patient-specific with a new algorithm using non-invasive data from qMRA and cuff pressure. The six more sectors have made the terminal resistances more patient-specific. The patient-specific aortic pressure has made the forcing function patient-specific. And the stiffness coefficient has made the compliance patient-specific. J Neurol Res. 2017;7(3):25-38 doi: https://doi.org/10.14740/jnr435w

Reflection modulation basis dual‐port intermodulation generator for dynamic calibration application in passive intermodulation measurements

The high-accuracy passive intermodulation (PIM) measurement shows great significance in PIM quality checking and related researches. As the key point to guarantee the test accuracy, the IM reference is essential in realizing precise PIM calibration. This paper presents a design of dual-port IM generator that can generate dynamic IM reference for this demand. The proposed generator employs a cascaded coupling network consists of two couplers, while a reverse biased Schottky diode is working as a tunable reflection IM source. The bias voltage and coupling coefficient are introduced to regulate the quiescent operation points of diode and the IM signal excitation strength respectively, they work together to put the IM reference signal on a desired level. Specially, a trimming strategy by using a compact terminal matching resistor is adopted to smartly regulate the IM tunable interval. These configurations can promote the utilization of this proposed IM generator to be flexible not only for design engineers but also for commercial users. The test results demonstrate that this generator can provide the tunable IM3 whose dynamic range can reach about 30 dB@2x43 dBm, 50 dB@2 × 31 dBm. Meanwhile, the significance of bidirectional dynamic IM reference signals is demonstrated.

Component Attachment with Pressureless Ag Sintering for 300°C Applications

With an increased demand for high-power and high-temperature electronics, Ag sintering paste has been considered a promising Pb-free die-attach material candidate for these applications. Extensive research has been carried out investigating pressure and pressureless Ag sintering for die attach. In this work, passive component (chip resistor) attachment with Ag sintering was explored. Due to termination geometry differences between resistors and dies, different processing procedures and parameters were developed. For PtAu terminated resistors, the mean shear force of as-built samples on thick-film Ag metallized substrates was 90 N, but dropped to 18.6 N after 1,500 h at 300°C. Formation of a dense Ag layer near the PtAu resistor termination and a void region near the thick-film metallization was observed in cross sections after 1,000 h at 300°C. For PdAg terminated resistors with a plated Ni/Au finish, the initial shear force results were low due to Ag diffusion along Au metallization surface. For PdAg terminated resistors with Ag thick-film substrates, the initial shear force was ~60 N and remained in the range of 50–70 N during aging at 300°C for 1,500 h. A new thick-film metallization (Au + Ag) was developed to enable the use of thick-film Au interconnect metallization.

Application of a Miniature Parallel Strip Line to Hard Disk Drive Immunity Test

A parallel strip line of very small size has been designed and fabricated in order to study the susceptibility of hard disk drive heads to electromagnetic noise. The target voltage standing wave ratio and internal-to-external field ratio have been confirmed up to at least 6 GHz. Calibration was conducted by measuring the field across the termination resistors. One example of susceptibility test to hard disk drive is shown.

Performance Test of an 8 kA @ 10-T 4.2-K ReBCO-CORC Cable

CERN is developing high-current ReBCO conductor on round core (CORC) cables for application in future detector and accelerator magnets. A characterization test on a ReBCO-CORC cable sample and its joints is performed in the 10-T FRESCA cable test facility at CERN. The sample is taken from the first 12-m-long CORC production. Key is the characterization of the field- and temperature-dependent critical currents of the CORC cable at 1.9 K and 4.2 K. Secondary objectives include evaluating the response of the CORC cable to quenches and the performance of cylindrical low resistive cable terminals especially designed and manufactured for use on CORC cables. The 7.6-mm CORC cable features 8 kA at 4.2 K and 10 T, and the joint terminals show a $25\pm 5-{n}\Omega$ resistance for 20-cm length.

A Low-Power Two-Tap Voltage-Mode Transmitter With Precisely Matched Output Impedance Using an Embedded Calibration Circuit

In this brief, a low-power two-tap voltage-mode transmitter (TX) with precisely matched output impedance using an embedded calibration circuit for dc-coupled unidirectional links is proposed. The proposed TX adopts an N-over-N driver with a supply voltage of 0.4 V in order to reduce the power consumption of the output driver. Its output driver is configured as a two-tap Finite Impulse Response (FIR) filter in order to compensate for channel loss at high frequency. In addition, the proposed embedded impedance calibration circuit precisely matches the impedance of the output driver to the channel characteristic impedance by using the receiver termination resistor instead of external reference resistors. The proposed two-tap voltage-mode TX is fabricated using a 90-nm low-power CMOS process technology and occupies an active area of 0.054 mm2. The measurement results show that the matching error of the output impedance is between −0.6% and +0.8%, and the power efficiency is 0.75 pJ/b without equalization and 0.94 pJ/b with 6-dB equalization, at a data rate of 5.0 Gb/s.

Analysis of Signal Integrity for High Precision Digital-to-Analog Conversion Circuit

In order to improve the accuracy of the digital to analog conversion (DAC), the reflection and crosstalk problems of the signal transmission process were studied in this paper. The Hyperlynx software was used for the simulation study of reflection and crosstalk problems of the master clock signal in the DAC circuit. Source end cascading termination resistor and remote end termination resistor and capacitor (RC) methods were adopted to weaken the reflected signal. The problem of signal crosstalk was solved by the remote end cascading termination resistor method. The experiments results showed that the reflection peak could be eliminated when the value of the source end cascading termination resistor was 100Ω. The reflection peak could be eliminated when the value of remote end termination resistors was 100Ω and the capacitance was 300pF. Terminating 100Ω resistor, shortening the length of the transmission line and decreasing the distance of the adjacent network could weaken crosstalk phenomenon. In high precision digital to analog conversion circuit, the source end cascading termination resistor and the remote RC termination were adopted to solve the problems of signal reflection. The methods of optimizing wiring and the cascading termination resistor weakened the signal crosstalk phenomenon. They also improved signal integrity and ADC accuracy of the signal during transmission.

Design and analysis of a current mode integrated CTLE with charge mode adaptation

With the reduction in feature size of CMOS transistors, the off-chip link speeds have not increased in the same pace as the on-chip link speeds. This gap in speed demands for better interface circuitry to mitigate the adverse effects of the off-chip links, especially, the intersymbol interference due to limited channel bandwidth and reflections due to impedance discontinuities. In this work, a first current mode continuous time linear equalizer (CTLE) with charge mode pole-zero adaptation scheme is proposed. The proposed equalizer is realized with common gate (CG) topology using switched capacitor based pole-zero adaptation to suit varying channel characteristics. The input impedance of the CG-CTLE is made equal to the characteristic impedance of the off-chip link, eliminating the need for a separate resistive termination. Since the proposed CG-CTLE acts as the first stage of the current mode receiver, there is no need for a separate trans-impedance amplifier or a preamplifier. In addition, the proposed CG-CTLE is analytically compared with conventional common source (CS) CTLE for the same targeted output signal swing and power consumption. The CG-CTLE outperforms CS-CTLE in terms of bandwidth and SNR, and is supported by analysis and simulations. The proposed CG-CTLE is implemented in a 1.1V, 65-nm CMOS technology. The performance results show that it achieves a data rate of 15Gb/s while equalizing the loss of a 7.5 inch FR4 PCB trace. It also offers an input impedance of 44.6Ω, SNR of 23dB and a bandwidth of 7.575GHz and consumes a power of 13.9mW.

DLTS analysis of high resistive edge termination technique‐induced defects in GaN‐based Schottky barrier diodes

Efficient edge terminations are fundamental for power electronic devices. High resistive edge termination technique obtained by ion implantation is a possible solution for GaN Schottky barrier diodes (SBD), but may induce defects detrimental to the devices. In this work, two sets of GaN SBDs, with or without a high resistive guard ring edge termination, were investigated by deep levels transient spectroscopy (DLTS). The corresponding DLTS spectra of devices with guard ring were compared to those of as‐fabricated devices (without). Four deep traps at 0.13, 0.26, 0.35, and 0.51 eV were observed below the conduction band in as‐fabricated structures while the ones with guard ring exhibit two additional levels at 0.47 and 0.80 eV and a strong enhancement in DLTS peaks magnitude. Further investigations showed that the additional traps detected in SBD devices with guard ring were consistent with ion implantation‐induced damages. These observations highlight the impact of high resistive edge termination technique on our devices and raise the need of optimization of such crucial structure for the improvement of GaN‐based Schottky barrier diode.