Diode Impedance Research Articles

A Compact Broadband Rectifier Based on Coupled Transmission Line for Wireless Power Transfer

Wireless Power Transfer (WPT) can effectively solve the problem of autonomous power supply for low-power devices. Rectifier is the key component in WPT technology. In this paper, a novel impedance matching network for the broadband rectifier is proposed. This impedance matching network compensates for the diode impedance and reduces its impedance change when the frequency or input power changes. The passive boosting mechanism utilizing coupled transmission lines (CTLs) improves the power conversion efficiency (PCE) of the diode in the low power region. The structure is especially optimized for low-power device applications. For validation, a broadband rectifier operating at 1.9–3 GHz is fabricated and measured. The structure fabricated on the Rogers 4003 substrate with a thickness of 1.508 mm and the diode is HSMS2860. The DC voltage Vout on the load (RL=1300 Ω) was measured. The results show that at 0 dBm, the PCE keeps more than 60% at 1.98–3 GHz. The peak PCE of 79.6% is obtained at 4 dBm. The compact size of the broadband rectifier is 19 mm × 21 mm. This broadband rectifier for low input power ranges can be applied to WPT technology.

A compact broadband RF rectifier using two‐stage microstrip lines

AbstractThis paper simulates and measures a compact broadband rectifier for voltage doubler Schottky diode. Among them, a two‐stage microstrip line impedance matching network for voltage doubling circuits is used. The imaginary part of the diode impedance is limited by the short‐circuit branch. The impedance conversion transmission line matches the impedance to 50 Ω. The impedance matching in the circuit is only realized by two‐stage microstrip lines, which reduces the physical size of the rectifier and makes the rectifier more compact. Judging the measurement results from 0.8 to 2.5 GHz, the conversion efficiency is greater than 30% at 0 dBm, the bandwidth is 103%, and the maximum conversion efficiency reaches 66.3% at 8 dBm. In addition, the compact size of the rectifier is 23 × 20 mm2.

Research on the influence of gas ionization on pulse forming in linear transformer driver (LTD) electron beam generator

Currently, there is limited research on the influence of gas ionization on the pulse formation process in pulse power source-driven loads. This paper introduces a road-field-Particle-In-Cell (PIC)/Monte Carlo Collision (MCC) collaborative simulation method that can accurately simulate gas ionization in Linear Transformer Driver (LTD) electron beam generation (EBG). The method couples the electromagnetic field and charged particle simulated through PIC/MCC with the circuit modules, and the load's voltammetry characteristics can real-time feedback to the Blumlein Pulse Forming Network (BPFN) of the LTD. In contrast to prior simulations that used fitted ideal T-shaped pulse input waveforms to model the load, this method provides a clearer depiction of the influence of gas ionization on the pulse shape. Additionally, the paper conducts simulation studies on LTD electron beam generator operating at different argon gas pressures. The findings indicate that introducing gas can effectively increase current while reducing voltage amplitude, thereby lowering the diode impedance. A small amount of gas can slightly enhance peak power, but excessive gas diminishes peak power and significantly shortens voltage pulse width. This is attributed to the beneficial effect of a small amount of gas ionization-produced plasma on the device. However, an excessive amount of gas ionization-generated plasma can lead to impedance mismatch in the device, even resulting in a load short circuit. This phenomenon causes a decrease in pressure drop at the top, consequently shortening the pulse width.

Compact high-efficiency energy harvesting positive and negative DC supplies voltage for battery-less CMOS receiver

In this paper, novel compact high-efficiency multi-band rectifiers that supply positive and negative output voltages are demonstrated for energy harvesting applications. The proposed voltage doubler circuits are used as real DC voltage supplies of radio frequency mm-wave CMOS receivers. Operating multi-band rectifiers have a complicated structure that required more resonance networks to force the rectifier to work in multi-band. Novel series and parallel resonance networks are implemented to force the rectifier to operate in dual-band at frequencies of 850 and 1400 MHz. The proposed resonance network eliminates the Schottky diode impedance variation as the input power or frequency changes and supports the impedance matching and minimizes the insertion loss. A novel high-quality sine-shape micro-strip inductor that obtains a quality factor above 65 over the frequency band from 200 to 1400 MHz and inductance equal to 14 ± 2 nH is designed to improve efficiency and enhance performance at low power levels. The first suggested RF voltage doubler rectifier with series resonance feedback between the input and cathode of the diode and parallel resonance operates at two frequency bands of 850 and 1400 MHz and obtains a peak conversion efficiency of 59%, a saturated output DC voltage is 2.5 V, and the conversion efficiency is 40% at RF-input-power of − 10 dBm. This voltage doubler achieves the required DC supply parameter (1.1 V and 450 uA) for biasing the mm-wave receiver at an RF input power of 0 dBm. Otherwise, the second suggested negative voltage rectifier has a maximum simulated conversion efficiency of 65%, saturated negative DC-voltage is − 3.5 V, and the conversion efficiency is 45% at an RF input power of − 10 dBm. The negative voltage rectifier obtains DC supply parameters (− 0.5 V and no current condition used for a gate bias) at − 10 dBm input power.

Investigation of intense pulsed ion beam generation by a magnetically insulated ion diode at a reduced impedance

The intense pulsed ion beam (IPIB) generation was investigated at reduced impedance of a magnetically insulated ion diode. The main goal of our research was to obtain IPIB with adjustable parameters at low current densities. The diode impedance was varied by the external magnetic field current by setting the delay of the accelerator's trigger relative to the launch of the magnetic field generator. The B-applied ion diode adjustably generated IPIB with a current density in the range from 25 to 4 A/cm2. In the matched mode the accelerator generates the ion beam with a current density of about 100 A/cm2. Obtained results of the IPIB current density adjustment allows to irradiate samples in a single vacuum cycle without the change of charging voltage of both magnetic field and accelerating voltage generators. Gold films with a thickness of 10 nm deposited on fluorine-doped tin oxide (FTO)/glass substrates were irradiated to demonstrate the applicability of obtained IPIB for irradiation of thin coatings without their deterioration. Single shot of IPIB with current density of 20 A/cm2 transformed Au film to spherical micro-particles, while after irradiation at the same fluence with 5 pulses of IPIB with current density of 4 A/cm2 Au coating was preserved as a film.

Understanding Transient Ionic Diode Currents and Impedance Responses for Aquivion-Coated Microholes.

Ionic diode based devices or circuits can be applied, for example, in electroosmotic pumps or in desalination processes. Aquivion ionomer coated asymmetrically over a Teflon film (5 μm thickness) with a laser-drilled microhole (approximately 10 μm diameter) gives a cationic diode with a rectification ratio of typically 10-20 (measured in 0.01 M NaCl with ±0.3 V applied bias). Steady state voltammetry, chronoamperometry, and electrochemical impedance spectroscopy data are employed to characterize the ionic diode performance parameters. Next, a COMSOL 6.0 finite element model is employed to quantitatively assess/compare transient phenomena and to extract mechanistic information by comparison with experimental data. The experimental diode time constant and diode switching process associated with a distorted semicircle (with a typical diode switching frequency of 10 Hz) in the Nyquist plot are reproduced by computer simulation and rationalized in terms of microhole diffusion-migration times. Fundamental understanding and modeling of the ionic diode switching process can be exploited in the rational/optimized design of new improved devices.

Wideband High-Efficiency and Simple-Structured Rectifying Metasurface

In this communication, a wideband rectifying metasurface for RF energy harvesting is proposed. By virtue of the two resonant modes of the paralleling metasurface resonator, it is not only the wideband feature can be obtained but also enables direct impedance matching between the high impedance diode and high impedance metasurface, eliminating impedance matching. A DC feed structure is proposed where each unit of the metasurface is connected by the chip inductors, and DC energy can be combined and exported directly, eliminating power combining networks. Then, A 6 × 6 array was designed and fabricated. Experimental results show that the proposed rectifying metasurface system operates at 5.32–6.66 GHz with a fractional bandwidth of 22.4%, and the peak efficiency is 74.5%. As a contribution to this work, RF energy on a broader frequency range can be captured by the proposed system with higher system efficiency, while maintaining a simple structure. This shows its great potential in wireless power transfer and indoor RF energy harvesting.

Inductive Type Impedance of Mo/<i>n</i>-Si Barrier Structures Irradiated with Alpha Particles

In silicon microelectronics, flat metal spirals are formed to create an integrated inductance. However, the maximum specific inductance of such spirals at low frequencies is limited to a value of the order of tens of microhenries per square centimeter. Gyrators, devices based on operational amplifiers with approximately the same specific inductance as spirals, are also used. Despite the fact that such solutions have been introduced into the production of integrated circuits, the task of searching for new elements with high values of specific inductance is relevant. An alternative to coils and gyrators can be the effect of negative differential capacitance (i.e., inductive type impedance), which is observed in barrier structures based on silicon.The purpose of the work is to study the low-frequency impedance of Schottky diodes (Mo/n-Si) containing defects induced by α-particles irradiation and determination of the parameters of these defects by methods of low-frequency impedance spectroscopy and DLTS (Deep Level Transient Spectroscopy).Unpackaged Schottky diodes Mo/n-Si (epitaxial layer of 5.5 μm thickness and resistivity of 1 Ohm∙cm) produced by JSC “Integral” are studied. Inductance measurements were carried out on the as manufactured diodes and on the diodes irradiated with alpha particles (the maximum kinetic energy of an αparticle is 5.147 MeV). The impedance of inductive type of the Schottky diodes at the corresponding DC forward current of 10 µA were measured in the AC frequency range from 20 Hz to 2 MHz. DLTS spectra were used to determine the parameters of radiation-induced defects. It is shown that irradiation of diodes with alpha particles produces three types of radiation-induced defects: A-centers with thermal activation energy of E1 ≈ 190 meV, divacancies with activation energies of E2 ≈ 230 meV and E3 ≈ 410 meV, and Ecenters with activation energy of E4 ≈ 440 meV measured relative to the bottom of c-band of silicon.

Harmonic-Based Integrated Rectifier–Transmitter for Uncompromised Harvesting and Low-Power Uplink

Wireless uplink of a sensor node based on modulating rectifier-generated harmonics is promising for lowered energy consumption and Tx-to-Rx leakage. The existing solutions need to balance between maintaining the rectification performance and modulating the reradiated harmonic. In this article, a novel controllable second-harmonic termination (CSHT) is proposed to modulate the reradiated second harmonic in amplitude without compromising the wireless power reception. By combining a CSHT and a rectifier, an integrated rectifier–transmitter (IRT) is formed. An analytical model is derived for designing CSHTs, while the relationship between the CSHT, the diode impedance, and the reradiated harmonic power is revealed for the IRT. As a proof of concept, an IRT prototype at 2.4GHz was designed and experimented. An uplink data rate of 2 Mb/s was achieved when the IRT was fed by a transmitter with +25-dBm output power at a distance of 4 m. The data transmission of the proposed IRT consumes power less than 12.2 pJ/bit while maintaining the wireless power rectification performance.

A Self-Packaged SISL Low-Power Rectifier Based on a High-Impedance Line for C-Band Applications

In this letter, a self-packaged substrate-integrated suspended line (SISL) rectifier is proposed. The rectifier consists of a quarter-wavelength high-impedance transmission line, a diode, a tuning inductor, and a dc pass filter. The lower the power is, the lower the rectifying efficiency is. At a low input power level, the diode impedance real part is almost zero. A tuning inductor is introduced to form a parallel resonator to enhance the diode voltage. A quarter-wavelength high-impedance line is presented to match the rectifying diode to the source. In addition, due to the self-packaging characteristics and air cavity of SISLs, the radiation loss and dielectric loss of the proposed rectifier are reduced. A rectifier was designed, fabricated, and measured at 5.8 GHz. The radio frequency (RF)-dc conversion efficiency reaches 3.5% at −30 dBm, which is close to its theoretical estimated efficiency at 5.8 GHz. This ultralow power rectifier may be used in energy harvesting at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C$ </tex-math></inline-formula> -band.

Evaluation of Explosive Emission Carbon Fiber Cathodes for High-Power Microwave Devices

Most high-power microwave (HPM) sources, such as the magnetically insulated transmission line oscillator (MILO) being developed at Texas Tech, utilize cold cathodes that generate electrons via explosive emission. Highly emissive cathodes such as the presented can generate current densities and currents greater than 1 kA/cm 2 and 10 kA, respectively, which are required for devices that can output radio frequency (RF) power greater than 100 MW. Typically, these cathodes are made of materials such as metal, silk or synthetic velvet, carbon fiber, and cesium iodine (CsI)-coated carbon fiber. In order to optimize the MILO performance, we fabricated carbon fiber velvet cathodes and compare their performance with other commercially available carbon fiber cathodes. Fabrication was done on a manual, mechanical loom using commercially available carbon fiber thread. Four carbon fiber cathodes were tested: in-house fabricated monomodal carbon fiber velvet, in-house fabricated bimodal carbon fiber velvet, in-house fabricated carbon fiber plain weave cloth, and bimodal carbon fiber velvet manufactured by ESLI Inc. Testing was performed in a vacuum chamber with variable AK gap in the high vacuum range (10−7 torr). High-speed optical imaging was performed in order to determine the uniformity of the generated plasma as well as the e-beam. Voltage and current measurements were performed to determine diode impedance and perveance.

Design of High-Efficiency Broadband Rectifier With Harmonic Control for Wireless Power Transfer and Energy Harvesting

In this letter, a novel methodology for designing a broadband rectifier with high efficiency and an extended dynamic range of input power is proposed for wireless power transfer (WPT) and energy harvesting (EH). The proposed structure consists of two main networks. The first one reduces diode impedance variation with only two transmission lines (TLINs). The second network deploys a synthesized three-stage, low-pass matching network (MN) to match the reduced-variation fundamental impedance to the source of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50~\Omega $ </tex-math></inline-formula> . The harmonic impedances in the stopband of this low-pass MN is manipulated to reshape the diode-across current and voltage following the Class-C or Class-R standard waveforms for power conversion efficiency (PCE) enhancement. For validation, a HSMS2860-based rectifier prototype is tested showing a bandwidth of 43.5% from 1.8 to 2.8 GHz with 72%-above PCE at an input power of 14 dBm. In addition, the PCE of over 70% is achieved across a bandwidth of 48.9% (1.7–2.8 GHz) with the highest of 82.5% at 12 dBm while the measured PCE can remain above 47% within the same bandwidth at a low input power of 0 dBm. Furthermore, the proposed rectifier has a comparative size of 46 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times32$ </tex-math></inline-formula> mm.

Investigation of the characteristics of the explosive-emission cathode based on carbon fiber in pulsed-periodic electron beam generation

Explosive electron emission cathodes provide a high current density without auxiliary systems and, therefore, have long been the subject of research for high-power pulsed accelerators. The paper summarizes the results of studies on the operation of an explosive-emission cathode based on carbon fiber in operating modes with a pulse repetition rate of 5–15 pps, at a voltage rise rate of ≈ 2.5 × 1012 V/s. The change in current and voltage as a function of the number of pulses and the diode impedance in the pulsed-periodic mode with a voltage pulse duration of 200 ns at full width half maximum (FWHM) are studied. During testing, the total diode current reduced by 25%. The change in the characteristics of the cathode at different pulse repetition rates is given up to 3.2 × 105 pulses. Changes in characteristics are correlated with changes in the microstructure of the cathode surface, presented in the enlarged images of the cathode surface.

Accurately Modeling Zero-Bias Diode-Based RF Power Harvesters With Wide Adaptability to Frequency and Power

This paper proposes an analytical method for effectively evaluating the performances of zero-bias diode-based RF power harvesters. The method allows the accurate calculation of both the diode power conversion efficiency (PCE) and matching efficiency, while showing the wide adaptability to frequency and input power. To calculate the diode PCE accurately, the junction voltage is built based on modeling the diode junction capacitance and turn-on voltage. Using the accurate diode PCE, the equivalent nonlinear resistance of the diode is calculated, and thus the diode impedance is obtained. This helps to design a matching network with required bandwidths and evaluate the corresponding matching efficiency. The total PCE of the RF power harvester is finally obtained by multiplying the diode PCE and matching efficiency. For verification, dual-band RF power harvesters based on diodes of SMS7630 and HSMS-2850 are developed to cover the two 5G frequency bands for three telecom operators in China (2.515-2.675, 3.4-3.5 & 3.5-3.6 GHz). They are designed to operate in the low power range of −25-−5 dBm for low power harvesting scenarios. Compared with the simulated results, the calculation discrepancy of less than 3.12% can be achieved in evaluating the total PCEs of the RF power harvesters. Prototypes of the designed RF power harvesters were fabricated and measured for validation. It shows that the proposed analytical method can provide design guidelines for developing a multi-band RF power harvester.

Bias voltage effect on impedance, modulus and dielectric spectroscopies of HfO2-interlayered Si-based Schottky diodes at room temperature

In this study, Al/HfO2/p-Si metal-insulator-semiconductor (MIS) Schottky diode was fabricated by atomic layer deposition (ALD) technique with an adjusted HfO2 interlayer thickness of 3.3 nm. Using (I, V), (Z, θ) and (C, G) experimental data sets, the electric and dielectric properties of the fabricated diode were investigated in 1 kHz–10 MHz frequency range at different applied bias voltages at room temperature through complex functions like impedance, modulus, conductivity and dielectric. From the DC current-voltage (I–V) measurements, the ideality factor and the barrier height of the diode were estimated at room temperature as 2.22 and 0.86 eV, respectively. AC measurement results demonstrated the presence of two different polarization mechanisms (interfacial and orientational) in the investigated frequency range. The results also clearly showed that three relaxation phenomena exist within the diode bulk structure, and that both relaxation and conduction mechanisms are activated by the applied bias voltage. One of the relaxations was the Warburg relaxation spotted in the low frequency region in two different forms (semi-infinite Warburg in impedance Nyquist plots and finite-space Warburg in dielectric Nyquist plots) and both were explained by the slow diffusion of Al3+, O2− and Hf4+ ions across the interface layer. Equivalent circuit impedance fit analysis showed that the fabricated diode has a good MIS structure due to the demonstrated high resistivity and low-leakage of the interfacial HfO2 layer. The big values of the dielectric loss tangent (8.03 at 500 kHz and +2 V) as compared to the dielectric constant (0.13 at 500 kHz and +2 V) at room temperature and the independence of dielectric constant on temperature suggests the appropriate usage of the fabricated diode in thermal heating applications. The estimated four major parameters (ideality factor, barrier height, dielectric constant and dielectric loss tangent) were compared with other literature results based on different growth parameters and tabulated in conclusion.

Phase Control of an Infrared-Frequency Current Wave on a Microstrip Line with dc Diode Bias

Antenna tuning using voltage-controlled elements such as diodes or varactors has been challenging in the infrared. We present measurements of an antenna-coupled metal-oxide-metal (MOM) diode with a time constant fast enough to rectify at infrared frequencies. This diode loads a microstrip infrared antenna, and the dc diode impedance is a function of voltage. When a dc bias voltage was applied across the diode, phase shifts of the current standing waves on the antenna were observed using scattering scanning near-field optical microscopy. This is the first experimental evidence of a dc bias voltage on a MOM diode controlling the phase of current waves at infrared frequencies.

Cold atmospheric pressure plasma jet prepares TiO2 coating on carbon fibre for field emission and explosive electron emission

As the ‘heart’ of high-current vacuum electronic devices, explosive emission cathodes play an important role in their applications. In this work, a titanium dioxide (TiO2)/carbon fibre cathode prepared by a cold atmospheric plasma jet is reported. TiO2 on the carbon fibre surface prepared by an atmospheric plasma jet is at the mixture of anatase and rutile phases. The field enhancement factor of the TiO2/carbon fibre cathode is 6681, which is over ten times higher than that of the carbon fibre cathode. Furthermore, the TiO2 coating slows the diode impedance collapse and decreases the cathode plasma expansion velocity from 1.5–2.0 to 1.0–1.5 cm µs−1, which is explained by a cathode plasma model. The surface of the TiO2/carbon fibre cathode is covered by 1.6 cm2 plasma, far exceeding that of the carbon fibre cathode (1.1 cm2), which enables uniform explosive electron emission. The obtained results show that TiO2/carbon fibre cathodes prepared by cold atmospheric plasma jets will be potential candidates as high-current explosive electron emitters.

Spatially resolved self-heating and thermal impedance of laser diodes using CCD-TR imaging

The spatial distribution of the surface temperature of single and multi-section slotted semiconductor laser diodes with surface gratings is investigated experimentally with CCD-thermoreflectance imaging. The lasers are single frequency devices, operating at approximately 1550 nm. High resolution temperature maps of the laser ridge are obtained, with spatial resolution near 1 µm. The temperature profile in the direction lateral to the ridge is presented and a rapid decay in temperature away from the ridge is observed. Acquisition of the temperature maps takes about 8 minutes, with three maps required for a 400 µm device. The ridge temperature rise is shown to be linear with the power consumed by the diode. The temperature profile along the laser ridge is shown to be uniform within a section of the multi-section laser. The thermal impedance of the single section slotted laser and the various sections of the multi-section slotted laser were determined. It was found that the thermal impedance ridge length product (ZthL) was 40 ± 6 ° C µm/mW for all section lengths. Between sections a rapid decay is also observed.

Wide Input Power Range X-Band Rectifier With Dynamic Capacitive Self-Compensation

A microwave rectifier composed of a pair of Schottky diodes with dynamic capacitive self-compensation is proposed in this letter. The impedance of a Schottky diode usually varies with the input power. A method using paired diodes for capacitive self-compensation is presented to enhance the rectifier’s dynamic power range. The imaginary part of one diode’s impedance is compensated using another identical diode with a section of transmission line by impedance transforming. The proposed method reduces the effect of the input power on the diode impedance. An $X$ -band rectifier using a pair of HSMS-286 Schottky diodes based on the proposed method is designed and fabricated. This rectifier, with a dc load of $300~\Omega $ , achieves power conversion efficiency of 64.5% at 9.7 GHz and has a 15.3-dB input power dynamic range with efficiency exceeding 50%. The rectifier is expected to be used in wireless power transmission systems with flexible distance requirements.

Decreasing the Loading Effect of the TVS Diode Using a Transmission Line for RF and Microwave Applications

In this letter, a new method for decreasing the loading effect of the transient voltage suppressor (TVS) diode has been presented and its technical details are studied under the immunity standard of IEC61000-4-2. In our approach a transmission line with a specific electrical length is employed to convert the TVS diode impedance to a significant impedance at the operating frequency. As a result, the TVS diode does not have any destructive effect on the RF specifications. In addition to the simulation using ADS software, a test circuit is fabricated on a RO4003 substrate. The simulated and measured S11 and S21 show appropriate frequency responses. However, by applying the proposed method, a parasitic inductance in the discharge path is created that can cause significant overshoot voltages during an electrostatic discharge event. In order to handle this shortcoming, the impact of this inductance is well studied using ADS and CST software and two techniques are introduced to minimize the overshoot voltages.