Current Issue : October-December Volume : 2023 Issue Number : 4 Articles : 5 Articles
This paper presents a compact hybrid G-band (170–260 GHz) heterodyne receiver module incorporating both Millimeter Microwave Integrated Circuits (MMICs) and a Schottky diode-based circuit. An on-chip sextupler and a Low Noise Amplifier (LNA), along with a diode-based Sub- Harmonic Mixer (SHM), are integrated into the demonstrated singular module, which is carefully designed and arranged with the co-simulations in electromagnetic and thermal domain. Through this methodology, a terahertz receiver module is fabricated with a volume of only 27 × 20 × 20 mm3. The measured results indicate that the double-sideband conversion gain of the receiver is 10.5–17.5 dB from 195 GHz to 230 GHz, while the noise temperature is 1009–1158 K. As a result, this terahertz receiver provides recorded miniaturized hardware applicable for terahertz Integration of Sensing and Communication (ISAC) systems....
Considering that current voltage transformer models of electrical multiple units (EMUs) are narrow-band models or transformer models, this paper introduces a wide-band model of EMU voltage transformers based on the vector ing method, circuit synthesis theory and black-box model theory. The admiances of voltage transformers from 30 kHz to 5 MHz are measured by the vector network analyzer, the branch admiances in the pi-type equivalent circuit are calculated according to the equation of a two-port network equivalent circuit. Based on the vector matching method, the rational function formulas of branch admiances are obtained, and the formulas are converted into the circuit models by circuit synthesis theory. The pi-type equivalent circuit model is constructed in the simulation software, and so is the voltage transformer model in the range of 30 kHz–5 MHz. The frequency sweeping method is used to measure the transmission characteristics from direct current (DC)to 30 kHz. The pi-type model is modied according to transmission characteristics, whereby the wide-band model in DC-5 MHz is obtained. Fast pulse experiments are carried out on the voltage transformer, and the actual injected fast pulse voltage is used as the excitation source in the simulation model. The measurement and simulation results on the secondary side of the voltage transformer show that the wide-band model has a high accuracy....
The electrical characteristics and resistive switching properties of memristive devices have been studied in a wide temperature range. The insulator and electrode materials of these devices (silicon oxide and titanium nitride, respectively) are fully compatible with conventional complementary metal-oxide-semiconductor (CMOS) fabrication processes. Silicon oxide is also obtained through the low-temperature chemical vapor deposition method. It is revealed that the as-fabricated devices do not require electroforming but their resistance state cannot be stored before thermal treatment. After the thermal treatment, the devices exhibit bipolar-type resistive switching with synaptic behavior. The conduction mechanisms in the device stack are associated with the effect of traps in the insulator, which form filaments in the places where the electric field is concentrated. The filaments shortcut the capacitance of the stack to different degrees in the high-resistance state (HRS) and in the low-resistance state (LRS). As a result, the electron transport possesses an activation nature with relatively low values of activation energy in an HRS. On the contrary, Ohm’s law and tunneling are observed in an LRS. CMOS-compatible materials and low-temperature fabrication techniques enable the easy integration of the studied resistive-switching devices with traditional analog–digital circuits to implement new-generation hardware neuromorphic systems....
We investigated the temperature-dependent reverse characteristics (JR-VR-T) of vertical GaN Schottky-barrier diodes with and without a fluorine-implanted edge termination (ET). To understand the device leakage mechanism, temperature-dependent characterizations were performed, and the observed reverse current was modeled through technology computer-aided design. Different levels of current were observed in both forward and reverse biases for the ET and non-ET devices, which suggested a change in the conduction mechanism for the observed leakages. The measured JR-VR-T characteristics of the non-edge-terminated device were successfully fitted in the entire temperature range with the phonon-assisted tunneling model, whereas for the edge-terminated device, the reverse characteristics were modeled by taking into account the emission of trapped electrons at a high temperature and field caused by Poole–Frenkel emission....
Zn-ZnO(Nw)-rGO hybrid electrodes for supercapacitor applications were successfully prepared in situ by a one-step microwave-assisted hydrothermal method by deposition of reduced graphene oxide (rGO) on the structure of ZnO nanowires grown on the Zn foil. During the hydrothermal treatment, two processes occur the reduction of graphene oxide (GO) and the deposition of rGO on the Zn-ZnO(Nw) support. The growth of ZnO nanowires was achieved by thermal oxidation below the melting point of the Zn foil in a controlled atmosphere. The as-obtained electrodes were assessed for structural, optical, and morphological properties by X-ray diffraction, Raman spectroscopy, ultraviolet-visible spectroscopy, SEM microscopy, and EDX analysis. The supercapacitor properties of the Zn-ZnO(Nw)-rGO hybrid electrodes were investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge analysis. The CV curve reveals that the Zn-ZnO(Nw)-rGO hybrid structures work as negative electrodes and exhibit a non-ideal rectangle-like shape, suggesting that the as-synthesized structure behaves as a pseudo-capacitor. A maximum capacitance was determined to be 395.79 mF cm−2 at a scan rate of 5 mV s−1. Based on GCD analysis, the maximum specific capacitance of 145.59 mF cm−2 was achieved at a low power density of 2 mA cm−2. The cycle life assessment of the Zn-ZnO(Nw)-rGO hybrid electrode over a 250-cycle number was performed by CV and GCD analysis. The maximum retention rate of 120.86% was achieved from GCD analysis over 250 cycles for the Zn-ZnO(Nw)-rGO hybrid electrode....
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