High Frequency Response Characteristics Research Articles

(Digital Presentation) On-Chip Micro-Supercapacitors of 3D Carbon Nanotube/Gold Nanocomposites through Silicon-Based MEMS Technology

The high-power and high-frequency response characteristics of supercapacitors have enabled their promising application in fasting charging/discharging scenarios such as power grid stabilization and Internet of Things (IoT). The widespread use of portable electronic devices and the evolution of the IoT have underscored the growing demand for the ongoing miniaturization and enhanced energy autonomy of existing circuit components [1]. Micro-supercapacitors (MSCs) have surfaced as a promising solution to meet these demands, offering superior power density and cycle life compared to similar battery products [2]. However, integrating MSCs with electronic circuits presents significant challenges, often serving as a roadblock to comprehensive system miniaturization. To cater to the requirements of practical application scenarios, particularly in System-in-Package (SiP) and System-on-Chip (SoC) contexts, the fabrication of MSCs requires the use of silicon-based semiconductors or Micro-Electro-Mechanical Systems (MEMS) technology [3]. This strategic approach not only enhances performance but also ensures shorter interconnection distances, more compact dimensions, and increased energy and power density across all components. Emphasizing high power density, elevated energy density, and responsive high-frequency behavior is crucial for the optimal characteristics of MSCs in future applications. As for electrode materials, carbon, which is abundant and cost-effective, has spurred extensive research into various nanostructured carbon-based materials for Electric Double-Layer (EDL) MSCs, including activated carbon, carbon nanotubes (CNTs), carbide-derived carbon, and onion-like carbon [4]. Additionally, transition metal oxides such as ruthenium oxide and manganese oxide, along with conductive polymers like polypyrrole and polyaniline, have proven useful as materials for pseudocapacitive micro supercapacitors [5]. Notably, CNTs fabricated through Chemical Vapor Deposition (CVD) are unequivocally compatible with MEMS microfabrication technology. In the context of EDL MSCs, a dense CNT network structure boosts energy density but impedes ion transport, thereby reducing power density. Conversely, a sparse CNT network structure facilitates ion transport but compromises high-frequency response due to fewer charge transfer paths. Therefore, the development of CNT-based MSCs tailored to practical application needs a more thorough investigation into CNT network structures and their current collector designs.Here, we report the fabrication of on-chip MSCs that are fully compatible with Silicon-based MEMS technology. Figure 1 illustrates the fabrication and characterization process of on-chip MSCs utilizing silicon-based MEMS technology, showing distinct surface morphologies of b-Si nanostructures after CNT growth and Au layer deposition. Figure 2 presents the electrochemical performance of the on-chip MSCs. The CV curves exhibit an ideal rectangular shape at a scan rate of 1 V/s. Even at a high scan rate of 100 V/s, the CV curve maintains a quasi-rectangular shape with minimal distortion, confirming the ultrafast response performance (Fig. 2 (a-b)). The phase angles of the on-chip MSCs are measured to be -68.9° and -66.2° in 1.0 M Na2SO4, and -64.1° and -70.8° in 0.5 M H2SO4 at 120 Hz (Fig. 2 (c)). The absence of a prominent semicircle in the Nyquist plots at high frequencies region implies fast electron transfer and ion diffusion within CNT/Au nanocomposite electrodes. Furthermore, the equivalent series resistances (ESR) are 0.604 Ω·cm2, 0.201 Ω·cm2, 0.504 Ω·cm2, and 0.126 Ω·cm2 for Si-CNT-20 and Si-CNT-20-Au MSCs (Fig. 2 (d)), indicating excellent interfacial contact between the CNT layer and Au current collector and good electrode conductivity. Fig. 2(e) shows that the MSCs deliver a specific capacitance (CA ) of 0.049 mF/cm2, 1.041 mF/cm2, 0.101 mF/cm2, and 1.368 mF/cm2 in 1.0 M Na2SO4 and 0.5 M H2SO4 at 120 Hz, respectively. The relaxation time constant (τ0 ) is calculated to be as short as 1.65 ms for the MSCs (Si-CNT-20-Au), underscoring rapid ion diffusion within electrodes in 0.5 M H2SO4 electrolyte (Fig. 2 (e)).In conclusion, we have successfully used b-Si as the scaffold structure and 3D CNT/Au nanocomposites as the active material for on-chip MSCs application. Significantly, the incorporation of this silicon-based 3D CNT/Au nanocomposite electrode presents promising prospects for the application of MSCs in varied domains, including wearable electronics, IoT devices, and sensor networks.

A Study on the Gas/Humidity Sensitivity of the High-Frequency SAW CO Gas Sensor Based on Noble-Metal-Modified Metal Oxide Film

In order to improve the response characteristics of the surface acoustic wave (SAW) sensor to trace gases, a SAW CO gas sensor based on a Pd-Pt/SnO2/Al2O3 film with a high-frequency response performance is proposed in this paper. The gas sensitivity and humidity sensitivity of trace CO gas are tested and analyzed under normal temperatures and pressures. The research results show that, compared with the frequency response of the Pd-Pt/SnO2 film, the CO gas sensor based on a Pd-Pt/SnO2/Al2O3 film has a higher frequency response performance, and the sensor has high-frequency response characteristics to CO gas with a concentration in the range of 10-100 ppm. The average response recovery time of 90% ranges from 33.4 s to 37.2 s, respectively. When the CO gas with a concentration of 30 ppm is tested repeatedly, its frequency fluctuation is less than 5%, indicating that the sensor has good stability. In the range of relative humidity (RH) from 25% to 75%, it also has high-frequency response characteristics for CO gas with a 20 ppm concentration.

Study on high frequency response characteristics of a moving-coil-type linear actuator using the coils combinations

This paper addresses the problem of dynamic characteristics of a moving-coil-type linear actuator (MctLA) to satisfy the requirements of higher output electromagnetic force and faster response time. A novel coils combination approach is presented because the time constant and the electrified currents are highly relevant to the resistance and the inductance. A general coil is divided into several segments and then used in parallel and series so that three different combinations of the electrified coils are developed. A mathematical model related to the output electromagnetic force, displacement response time, acceleration of the proposed MctLA is presented, respectively. Simulations results show that if the electrified coils are divided into three sections and used in parallel, the dynamic and static performances of the proposed MctLA are greatly improved. Numerical simulation and experimental results prove the usefulness of the electrified coils combinations approach, and the proposed MctLA can display high frequency response characteristics.

Study on high frequency response characteristics of a moving-coil-type linear actuator using the coils combinations

Study on high frequency response characteristics of a moving-coil-type linear actuator using the coils combinations

HOLE ACCUMULATION EFFECT OF InGaAs HIGH-ELECTRON-MOBILITY TRANSISTORS WITH A 1550-nm WAVELENGTH FEMTOSECOND PULSE LASER

InGaAs is known as a material system with high electron mobility derived from InAs and can be formed by metal organic chemical vapor deposition. The base material substrate is InP and is formed by controlling the composition ratio of In and Ga to lattice match with this InP. The bandgap energy Eg of InGaAs is 0.87 eV, and photoelectric conversion of 1550-nm light, which is a communication wavelength band, can be executed. Therefore, it is now used as a detector material in optical communication technology. In this study, we investigated the photoresponsive properties of InGaAs high-electron-mobility transistors (HEMTs) with simultaneous utilization of photoresponse characteristics and high-frequency response characteristics of this InGaAs crystal. A1550-nm wavelength femtosecond pulse laser (with a pulse width of 100 fs and a period of 50 MHz) was coupled with DC light with a wavelength of 1480 nm and irradiated from the InGaAs HEMT metal electrode surface. Laser light transmitted through the side of the gate metal electrode into the device structure generates electron-hole pairs via the photoelectric effect in the InGaAs layer, and it was confirmed that the maximum drain current of 0.4 mA was reduced. A current response is detected inside the semiconductor by transporting electrons to the drain electrode side and holes to the source electrode side. Because the laser used is pulsed light, the process of generation and disappearance of electron-hole pairs were confirmed as photoresponsive properties.

Automotive Reclaiming Energy Vibration Reduction System Based on Electric Control Rectifying Valve

With the automotive popularization, energy dilemma and environmental problems are further severe. Now the mechanic vibration energy recovery devices which have been invented could not break the bottleneck of low energy recovery efficiency and bad high frequency response. This system is based on hydro-electric reclaiming energy vibration damper electric control rectifying valve with independent intellectual property rights, and is composed with electrical and hydraulic multi-system, converting the automobile suspension vibration energy to electric energy to recycle. Compared with the same kind products, this system avoids their shortcomings and has great advantages. Through automatic and accurate rectification control on liquid flow, the system is able to improve system high-frequency response characteristics, reduce system energy loss, and enhance the system working reliability. This paper will present Automotive Reclaiming Energy Vibration Reduction System Based on Electric Control Rectifying Valve in 7 parts.

Saturation and Short Pulse Response Characteristics of the Fe-Based Amorphous Core With a Small Air Gap

In this paper, saturation and high-frequency pulse response characteristics of the Fe-based amorphous core with a small air gap are studied in detail by theoretical analysis and experiments. After a 0.32-mm air gap was cut through the longitudinal cross section of the amorphous core, test results showed that the relative permeability of the amorphous core only had small changes. Therefore, mechanical processing jobs can be done on the amorphous core made of curled fragile thin tapes. In the charge experiment, the maximum saturation voltage of a 1:10 transformer based on the air-gapped core increased by 1.33 times in contrast to that of the closed-core situation, which basically corresponded to the theoretical calculation (1.6 times). The small air gap obviously improved the saturation characteristics of the amorphous core but decreased the coupling coefficient and step-up ratio of the 1:10 transformer. Experimental results of another 3:3 transformer based on the air-gapped core proved that the air gap had great effects on the high-frequency response characteristics of core-type transformers. The loss ratio of the response voltage signal of the air-gapped-core transformer increased by about 30% in contrast to that of the closed-core situation. The air gap had small effects on the front-edge response to square pulses.

Effects of electronic state modulation on the high-frequency response characteristics of GaAs quantum wells

Abstract The effect of electronic-state modulation on the high frequency response of GaAs quantum well with thin inserted barrier layer is studied. The carrier scattering by polar optic phonons, acoustic deformation potential and background ionized impurities are incorporated in the present calculations considering the carrier distribution to be heated drifted Fermi–Dirac distribution. Modified phonon spectra and modulated electron wave function give different values of form factor compared to bulk mode phonon. Mobility is found to be enhanced on insertion of thin layer inside the quantum well. The ac mobility and the phase lag increases with the increase in both the channel width and the 2D carrier concentration. Cutoff frequency, where ac mobility drops down to 0.707 of its low frequency value, is observed to be enhanced reflecting better high frequency response.

聚合物定向耦合电光开关的高频响应特性分析

聚合物定向耦合电光开关的高频响应特性分析

Characterization of flexible ECoG electrode arrays for chronic recording in awake rats

We developed a 64-channel flexible polyimide ECoG electrode array and characterized its performance for long-term implantation, chronic cortical recording and high resolution mapping of surface-evoked potentials in awake rats. To achieve the longest possible recording periods, the flexibility of the electrode array, adhesion between the metals and carrier substrate, and biocompatibility were critical for maintaining the signal integrity. Experimental testing of thin film adhesion was applied to a gold–polyimide system in order to characterize relative interfacial fracture energies for several different adhesion layers, yielding an increase in overall device reliability. We tested several different adhesion techniques including the following: gold alone without an adhesion layer, titanium–tungsten, tantalum and chromium. We found titanium–tungsten to be a suitable adhesion layer considering the biocompatibility requirements as well as stability and delamination resistance. While chromium and tantalum produced stronger gold adhesion, concerns over biocompatibility of these materials require further testing. We implanted the polyimide ECoG electrode arrays through a slit made in the skull of rats and recorded cortical surface evoked responses. The arrays performed reliably over a period of at least 100 days and signals compared well with traditional screw electrodes, with better high frequency response characteristics. Since the ultimate goal of chronically implanted electrode arrays is for neural prosthetic devices that need to last many decades, other adhesion layers that would prove safe for implantation may be tested in the same way in order to improve the device reliability.

Microwave thin-film transistors using Si nanomembranes on flexible polymer substrate

Large-feature-size single-crystal Si thin-film transistors (TFTs) with fT of 1.9GHz and fmax of 3.1GHz were demonstrated on flexible polymer substrate. In this letter, the authors detail the fabrication process that enables TFTs, made on low-temperature flexible substrates, to operate at microwave frequencies under low bias voltages. The outstanding electrical performance results measured from these devices, such as high electron mobility, high current drive capability, and high frequency response characteristics, and the simple process procedures for producing these devices on flexible substrate make flexible electronics highly promising for power-efficient large-area radio-frequency and microwave applications.

Transit-time limited high-frequency response characteristics of MSM photodetectors

A simplified, but useful, one-dimensional transit-time limited frequency domain current response model of MSM photodetectors is presented. The model includes the effects of unequal velocities and lifetimes governing the lateral transport of photogenerated holes and electrons in the absorption layer. Normalized frequency response curves depicting the amplitude and phase versus the frequency are presented using the transit-time ratio as a parameter. The usefulness of the analytical response amplitude curves for the extraction of hole and electron transit times has been demonstrated by regressively fitting them with the measured results obtained from practical MSM photodetectors.

High Frequency Rogowski Coil Response Characteristics

The high frequency response characteristics of differentiating and self-integrating Rogowski coils have been calculated for arbitrary values of the coil terminating resistance assuming Ampere's law to be valid. Effects due to a reactive terminating impedance are also discussed. When the displacement current is taken into account in the measurement of the current of a charged particle beam, it is found that an effective rise time is introduced into the self-integrating coil response on the order of a/ϒυ, where a is the major radius of the coil, υ is the velocity of the beam, and ϒ = (1 -υ2/c2)-1/2.

Electrocardiographic distortions caused by inadequate high-frequency response of direct-writing electrocardiographs

The majority of direct-writing electrocardiographs in present use have inadequate high-frequency response characteristics, in that Q, R, and S amplitude errors will result when such systems are used for recording. In a study of 60 electrocardiographic waveforms, wide-band (greater chan 1,000 c.p.s.) recordings were compared with recordings using lower cutoff frequencies. Identical complexes were compared. In order to reduce Q, R, and S amplitude errors below 0.10 millivolt, a cutoff frequency greater than 100 c.p.s. is required. Errors in the duration of QRS are less affected unless the cutoff frequency is reduced to the vicinity of 60 c.p.s. Other time intervals, such as Q-wave duration and P-R and Q-T intervals, are affected in somewhat the same manner as QRS durations, and a small percentage of records exhibited erros in these durations even with a cutoff frequency of 80 c.p.s. The use of direct-writers having a cutoff frequency of at least 100 c.p.s., with no resonant peaks below this frequency, is recommended as a minimum response. To reduced amplitude errors below 0.05 millivolt, the use of a considerably greater cut-off frequency, perhaps 200 c.p.s., is recommended. It is also suggested that recording techniques need to be improved in order to take advantage of the higher frequency response because of the increased capability to respond to power-line frequency interference.

Energy Spectral Density of the Sonic Boom

The energy spectral density of ideal sonic-boom pressure signatures has been computed and equations have been developed for the asymptotic behavior of the spectra at high and low frequencies. For systems with essentially high-frequency response characteristics, the system will be basically sensitive to peak overpressure and not to N-wave duration. Low-frequency systems will be sensitive to both duration and peak overpressure. Experimental data are cited to corroborate these conclusions based on the theory.

Hearing Aid Design Criteria

The restricted low frequency and exaggerated peaky high frequency response characteristics of some modern transistor hearing aids, coupled with their very high output levels are considered unsatisfactory for use by many perceptively deaf children. Experiment has shown that providing sufficient amplification is given in the 250-750 c/s frequency range, very high output levels are seldom required, even by severely deaf children. No aid known to the author will perform according to the design criteria outlined which propose suggestions not usually accepted in hearing aid design. These are considered likely to satisfy many children who at present are not making full use of their residual hearing.Depending on the type and severity of the deafness a flat frequency response characteristic should be incorporated over the range of 250-4000 c/s. The maximum output levels should be restricted for example to either 125 dB or 110 dB spl. with associated maximum air to air gain figures of 60 dB or 45-50 dB respectively...

Measurement of Parameters Controlling Pulse Front Response of Transformers

The two-element equivalent circuit commonly used in predicting the high-frequency or pulse-front response of a stepdown or step-up transformer is not applicable to transformers with turns ratios near unity. Furthermore, the transformer leakage inductance (the series element in the circuit) may vary with frequency or time because of skin effects in the windings, and the distributed capacitance (the shunt element in the circuit) varies with frequency or time, source impedance, and load impedance because of variations in voltage distribution. These variations are difficult to take into account in measuring the element values and also in using the values in the prediction of transformer response. A theoretical and experimental analysis has shown that a T circuit containing three inductances and one capacitance (or the mathematically equivalent \pi circuit, which contains seven elements) can be used to represent a transformer of any turns ratio, and element values obtained from appropriate measurements give reasonably accurate results over necessary frequency range. Measurements are easily made with an rf generator and a vacuum-tube voltmeter. Greater accuracy with which high-frequency response characteristics can be predicted by this T circuit indicates a marked improvement in accuracy will result when T circuit is used in predicting response of a transformer to fast-rising pulses.