High Impedance Devices Research Articles

Upper airway stimulation device failure: A 7-year single center experience

ObjectiveTo identify and report a single center experience with upper airway stimulator device-related failures. Study designRetrospective case series. SettingSingle tertiary academic center. MethodsRetrospective data on 352 patients who underwent UAS surgery with an Inspire device from 2016 to 2023 was collected, including demographics, comorbidities, and nature of device failure requiring revision surgery. ResultsOut of the 348 patients included in our analysis, 16 (4.6 %) required revision due to device failure, with an average interval of 772 days (∼2 years) between initial implant and revision. Most failures were attributed to respiratory sensing lead damage (n = 11, 68.8 %), resulting in high system impedance and subsequent device malfunction. Lead fracture causes varied, including idiopathic occurrences and potential trauma. Lead migration was noted in one case (6.3 %), where the hypoglossal electrode detached from the nerve. Two patients (12.3 %) required implantable pulse generator (IPG) replacement, one after experiencing trauma and the other due to unclear source of malfunction. One patient (6.3 %) required complete system replacement following high lead impedance and absent tongue motion. The last patient required replacement of both the IPG and respiratory lead after experiencing high lead impedance (6.3 %). ConclusionRespiratory sensing lead fracture emerged as the leading cause of device failure in this cohort, underscoring the need to address this under-reported issue, potentially linked to the time lapse after device implantation.

On-Wafer Series-Through Broadband Measurement of Sub-fF55-nm MOS RF Voltage-Tunable Capacitors

The objective of this letter oriented toward micro-wave measurement of high-impedance devices using a conventional on-wafer probe station is multiple. First, we provided a quantification of the measurement uncertainty inherent to the setup when measuring capacitors in the range of 0.01–10 fF using both the reflection and transmission methods up to 50 GHz. In particular, we demonstrate a clear improvement when using the transmission method in series-through configuration. As a practical demonstration, on-wafer MOS voltage-tunable capacitors with capacitances ranging from 0.85 to 1.15 fF are extracted with uncertainties of 130 and 2 aF, respectively, for both reflection and transmission measurements at 10 GHz. Capacitance fluctuation related to the technological process on the order of 20 aF is then exemplary demonstrated using the series-through configuration.

Electrical Characterization of Emerging Transistor Technologies: Issues and Challenges

Experimental results gained by various electrical characterization techniques are discussed and compared for a CNTFET technology, which suffers as almost all emerging technologies from traps in the gate oxide. Based on these results, it is highlighted that, contrary to common practice, a fast data acquisition technique is required to ensure a proper electrical device characterization in terms of 1) trap-free device characteristics, 2) reproducible experimental results, and 3) a consistent set of dc and small-signal (ac) characteristics. It is argued that a reasonable technology comparison among emerging technologies must be based on data fulfilling these criteria since trap-affected measurements distort the device behavior which can lead to wrong conclusions about the performance of a device such as the apparent linearity. A trap model capturing the aforementioned issues is briefly introduced. Moreover, the challenges of the electrical characterization of high-impedance devices are explored.

Shot Noise of a Quantum Dot Measured with Gigahertz Impedance Matching

The demand for a fast high-frequency read-out of high impedance devices, such as quantum dots, necessitates impedance matching. Here we use a resonant impedance matching circuit (a stub tuner) realized by on-chip superconducting transmission lines to measure the electronic shot noise of a carbon nanotube quantum dot at a frequency close to 3 GHz in an efficient way. As compared to wide-band detection without impedance matching, the signal to noise ratio can be enhanced by as much as a factor of 800 for a device with an impedance of 100 k$\Omega$. The advantage of the stub resonator concept is the ease with which the response of the circuit can be predicted, designed and fabricated. We further demonstrate that all relevant matching circuit parameters can reliably be deduced from power reflectance measurements and then used to predict the power transmission function from the device through the circuit. The shot noise of the carbon nanotube quantum dot in the Coulomb blockade regime shows an oscillating suppression below the Schottky value of $2eI$, as well an enhancement in specific regions.

Clean carbon nanotubes coupled to superconducting impedance-matching circuits.

Coupling carbon nanotube devices to microwave circuits offers a significant increase in bandwidth (BW) and signal-to-noise ratio. These facilitate fast non-invasive readouts important for quantum information processing, shot noise and correlation measurements. However, creation of a device that unites a low-disorder nanotube with a low-loss microwave resonator has so far remained a challenge, due to fabrication incompatibility of one with the other. Employing a mechanical transfer method, we successfully couple a nanotube to a gigahertz superconducting matching circuit and thereby retain pristine transport characteristics such as the control over formation of, and coupling strengths between, the quantum dots. Resonance response to changes in conductance and susceptance further enables quantitative parameter extraction. The achieved near matching is a step forward promising high-BW noise correlation measurements on high impedance devices such as quantum dot circuits.

Measurement Techniques for RF Nanoelectronic Devices: New Equipment to Overcome the Problems of Impedance and Scale Mismatch

The emergence of new materials (nanowires, nanotubes, graphene tapes, and thin films) and devices with nanoscale dimensions give rise to the necessity for developing dedicated techniques that will allow their electrical characterization at high-frequency range. In this article, two possible views have been highlighted to tackle the issue of the measurement of high-impedance nanoscale devices. The first solution is based on the integration of a high-impedance reflectometer and a nanoscale device on the same chip. The microwave impedance of a single CNT has been successfully measured up to 6 GHz using this technique. The second solution consists of inserting an adjustable microwave interferometer between a traditional VNA and the high-impedance device. The interferometer allows adjustment of the impedance to be measured to the highest measurement sensitivity of the measurement system. In particular, capacitances down to 0.35 fF have been measured with an error estimated to be less than 10% using the interferometric technique combined with a scanning microwave microscope. These proofs of concept on one-port nanodevices open the route towards the case of two-port active devices with high impedance. Advances in the manufacturing of next-generation nanodevices will depend on our ability to measure electrical properties and performance characteristics accurately and reproducibly at the nanoscale regime over a broad frequency range.

A Stable Bayesian Vector Network Analyzer Calibration Algorithm

A new overdetermined vector network analyzer (VNA) calibration algorithm is presented. The new algorithm shows significant advantages in the measurement of very high-impedance devices such as carbon nanotube transistors and can be applied to all types of VNA calibration. It was found that, for high-impedance devices, the new algorithm yields up to four times more accurate results. The focus of this study is on the accuracy and robustness of the algorithm. A statistical error model of calibration, which includes errors in the calibration standards and errors in the VNA, is converted into a formula for calibration by Bayes' theorem. The numerical implementation of this formula makes use of nonlinear optimization techniques and Monte Carlo integration. The resulting new algorithm is compared against various other algorithms. Benchmarking shows that the presented calibration algorithm is robust and more accurate than all other tested algorithms in all tested calibration scenarios.

Characterization of a planar self-complementary square-spiral antenna in the THz region

This paper describes a compact, self-complementary square-spiral antenna on a GaAs substrate with a broadside high-directivity (∼29 dB) frequency-independent pattern when coupled through a silicon hyperhemisphere. The driving-point resistance undulates between ∼100 and 300Ω from 200 GHz to 1 THz—much higher than the 72Ω value from Booker's modified formula, but quite beneficial for coupling to high-impedance broadband devices. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 524–529, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21398

Approach to variable frequency measurements of carbon nanotube transistors

An approach to variable frequency characterization of high impedance devices such as a carbon nanotube field-effect transistor is presented. A top-gated nanotube transistor is configured as a common source amplifier, and frequency response function of the device is measured. Evidence of signal amplification is observed in time domain as well as frequency domain up to a unity gain frequency of approximately 600kHz. The observed roll-off in frequency is solely due to the measurement setup.

Performance of GaAs JFET at a Cryogenic Temperature for Application to Readout Circuit of High-Impedance Detectors

A GaAs junction field effect transistor (JFET) is a promising candidate for the cryogenic electronics of high-impedance sensitive photoconductors because of its low-noise at low frequencies. This GaAs JFET has advantages compared with other type of FETs, such as no kink phenomena or hysteresis in its current-voltage (I-V) characteristics, small gate leakage currents, and minute capacitance. We report on the noise spectra and leakage current of a SONY n-type GaAs FET in a high-impedance configuration where the gate terminal was surrounded by high-impedance devices at a cryogenic temperature, i.e., 4.2 K. In the high-impedance configuration, we obtained a low noise level and low leakage current of 0.5 /spl mu/V/Hz/sup 1/2/ at 1 Hz and 4.6/spl times/10/sup -19/ A. This result implies that the GaAs JFET is suitable for cryogenic readout electronics. We also discuss the source of the random telegraph signal and the 1/f noise in the GaAs JFET at cryogenic temperatures.

Nanometer-Size Conducting and Insulating Molecular Devices

Using quantum ab initio techniquesa theoretical “microscope”we demonstrate that molecules of nanometer sizes can be characterized as low and high impedance devices, needed as building blocks in the field of molecular electronics. Small alkanes and polyynes chains with σ and π bonding, respectively, yield a high-low impedance relation of 2 orders of magnitude at 1-nm length and of 3 orders of magnitude at 1.3-nm length. For these small chains, it is concluded that no simple trends of conductance versus length can be determined. We also successfully test our methods against a recent precise experiment.

Reliability of ECG monitoring with a gel pad/paddle combination after defibrillation

Recent warnings have highlighted the possibility of unreliable monitoring through gel pads and paddles when using manual defibrillators. Occasionally, this causes an apparent asystole to be displayed when the true rhythm is ventricular fibrillation. We investigated this phenomenon in the laboratory using defibrillator-testing devices with two different impedances and with two defibrillators (Physio-Control LIFEPAK 9 and Hewlett Packard XL). After delivery of a 200 J shock, the time taken for the original ECG test signal to return to the defibrillator monitor was measured. Measurements were made after each of a series of ten shocks delivered with each defibrillator and gel pad/ testing device combination. Additional measurements were made using self-adhesive combination defibrillator electrodes. When using a low-impedance testing device with gel pads, on all occasions the initial rhythm reappeared immediately. When using the high-impedance testing device, the post shock rhythm was initially displayed as ‘no signal’ (Hewlett Packard XL) or ‘asystole’ (Physio-Control LIFEPAK 9). Over the series of ten shocks, the time to return of the original signal ranged between 24 and 154 s with the Hewlett Packard and 17–61 s with the Physio-Control LIFEPAK 9. The time for return of the signal increased with successive shocks. When using Fast-Patch electrodes, the original test signal always returned immediately. We conclude that after the delivery of a shock, monitoring through gel pads may result in the display of spurious asystole being displayed. This is more likely to occur in the presence of high chest impedance and with an increasing number of shocks delivered through the same gel pads. If defibrillator paddles and gel pads have been used for ‘quick-look’ monitoring, and ‘asystole’ is displayed after delivery of a shock, the rhythm should be confirmed immediately with monitoring leads.

Design and calibration of a noise measurement system

The setup principle and calibration method of a noise measurement system for frequencies from dc to 10 kHz are described. This system measures the current noise power spectral density of some device, and consists of a low-noise current preamplifier, a voltage preamplifier, and a dynamic signal analyzer which implements the fast Fourier transform (FFT). The noise aspects of the whole system can be modeled as a serial noise voltage generator and a parallel noise current generator at the input port, plus a system free of noise. The cross correlation of the two noise generators is an imaginary number because the system input stage is composed of some junction field effect transistors (JFET's). Via the thermal noise measurement of several resistors, we derive the magnitudes of the noise generators in addition to the input impedance and the total system gain. The imaginary cross correlation is obtained by the noise measurement of pure capacitance. With a well-calibrated procedure, we can measure the noise power down to 2/spl times/10/sup -27/ A/sup 2//Hz. Two systems with different input stages were calibrated with the same procedure and the noise measurement results of the various resistance values with the two systems all agree well with theoretical values. One of these with an input stage which has a much smaller noise current generator shows great improvement in the noise measurement of the high-impedance device.

Occluded-ear simulator with variable acoustic properties.

Ear simulators were designed to replicate acoustical characteristics of the average adult ear. Due to variability of ear-canal geometry and eardrum impedance among individuals, the possibility of any one person exhibiting such "average" characteristics--especially if that person is a child and/or has a conductive pathology--is remote. Thus, ear simulators have been of only peripheral value when prescribing a hearing aid (a high output impedance device) to fit the acoustical requirements of a particular patient. Reported herein is development of a programmable artificial ear (PAE) that can account for individual differences in ear-canal geometry and eardrum impedance. It consists of a 2.0-cc coupler, microphone, amplifier, computer, PAE code, and a computer card and/or software for digitization and Fourier transformation. Required input data includes ear-canal dimensions, eardrum impedance, and output impedance of the hearing aid being tested. Sound-pressure recordings produced in the 2.0-cc coupler by the hearing aid are adjusted by the computer to what they would have been had the recordings been made at the eardrum of a particular patient wearing the same hearing aid. Good agreement was observed between experiment and theory for one test case involving a totally occluding miniature earphone.

Hy‐wire measurements of atmospheric potential

A method of directly measuring the electric potential drop across the lowest portion of the atmosphere by using an apparatus called Hy‐wire is described. This tethered balloon‐borne system has been operated extensively at altitudes near 0.62 km at which voltages over 150 k V were measured with a high impedance device. Also described are measurements of system parameters such as system capacitance (5.6 pf/m), impedance (1010Ω), and response time (tens of seconds). Hy‐wire measurements from an around the‐clock experiment at Wallops Island, Va., having a characteristic repetitive diurnal pattern of variability exceeding 40% of the mean, are presented. This diurnal pattern is discussed in terms of both local and global current sources. A demonstration using Hy‐wire as a lightning channel model is also presented. These experiments have so far been conducted at mid‐latitudes but can also be flown from other locations in an effort to determine whether the lowest atmospheric electric circuit is affected by high altitude and possibly global current systems, and if so how much. The data presented in this paper are not definitive about the source of potential variations. The data are, however, representative of the new Hy‐wire technique and demonstrative of the potential usefulness of this technique.

Piezoelectric ceramic headphone development

An examination of the pertinent characteristics of headphones is followed by a discussion of the influence of the electromechanical parameters of mounted piezoelectric elements. A comparison of these parameters for Rochelle salt and PZT <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∗</sup> ceramic elements reveals a two to one difference in the energy conversion capabilities of the two materials. The increased activity of Rochelle salt is present for all modes of operation but the difference is very slight for longitudinal and shear expander modes. This is not so for flexure type elements for which the difference is as quoted above«, Despite this advantage, there are some environmental limitations associated with this material. Thus, for some applications, the use of piezoelectric ceramics as the active element in such transducers is recommended. The net result of the difference in electromechanical coupling (energy conversion capability) in the two materials is a compromise in the characteristics of the modified headphone. The important performance characteristics of any headphone include (a) sensitivity, (b) frequency response, and (c) impedance level. Piezoelectric audio transducers in general are characterized as high impedance devices. A significant reduction in impedance does little to change this classification. Consequently, the design objective was to limit the compromise to a change in impedance only. Selection of a PZT ceramic element of suitable dimensions to yield the required sensitivity is facilitated by the use of equivalent circuit techniques. At low frequencies, the electroacoustical circuit representation of the piezoelectric headphone takes on a simple form. Most of the components of this circuit are known, but the dimensions of the mounted element are taken as variable. A solution of the pressure sensitivity of the headphone as a function of element dimensions is readily obtained. Use of the resultant equation is facilitated by plotting design curves. Pressure response measurements in accordance with existing techniques <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> yield data in good agreement with results predicted by the aforementioned analysis. The important characteristics include a sensitivity of 8 μbars/volt flat within ±3 db from 50 cps to 8 kc. The only significant change in performance between the crystal and ceramic phones is as anticipated; namely, a reduction in impedance from 90, 000 ohms to approximately 15,000 ohms at 1 kc.