Frequency Rectifier Research Articles

RF rectifiers for EM power harvesting in a Deep Brain Stimulating device.

A passive deep brain stimulation (DBS) device can be equipped with a rectenna, consisting of an antenna and a rectifier, to harvest energy from electromagnetic fields for its operation. This paper presents optimization of radio frequency rectifier circuits for wireless energy harvesting in a passive head-mountable DBS device. The aim is to achieve a compact size, high conversion efficiency, and high output voltage rectifier. Four different rectifiers based on the Delon doubler, Greinacher voltage tripler, Delon voltage quadrupler, and 2-stage charge pumped architectures are designed, simulated, fabricated, and evaluated. The design and simulation are conducted using Agilent Genesys at operating frequency of 915 MHz. A dielectric substrate of FR-4 with thickness of 1.6 mm, and surface mount devices (SMD) components are used to fabricate the designed rectifiers. The performance of the fabricated rectifiers is evaluated using a 915 MHz radio frequency (RF) energy source. The maximum measured conversion efficiency of the Delon doubler, Greinacher tripler, Delon quadrupler, and 2-stage charge pumped rectifiers are 78, 75, 73, and 76 % at -5 dBm input power and for load resistances of 5-15 kΩ. The conversion efficiency of the rectifiers decreases significantly with the increase in the input power level. The Delon doubler rectifier provides the highest efficiency at both -5 and 5 dBm input power levels, whereas the Delon quadrupler rectifier gives the lowest efficiency for the same inputs. By considering both efficiency and DC output voltage, the charge pump rectifier outperforms the other three rectifiers. Accordingly, the optimised 2-stage charge pumped rectifier is used together with an antenna to harvest energy in our DBS device.

Use of Langmuir Blodgett Thin Films in Tunnel Diodes for Energy Harvesting or Sensing Applications

Tunnel diodes have been found suitable for use in high frequency rectification for energy harvesting or sensing applications in structures known as rectennas. For tunneling to take place in a metal insulator metal (MIM) type assembly, an ultrathin pinhole free insulating layer must be deposited between the metal layers for the diode to operate with small turn on voltages.Langmuir Blodgett (LB) thin film deposition is a useful technique that allows the deposition of conformal, uniform monomolecular layers with a precise control of thickness. Organic compounds such as Vinyl Stearate, 10-12 Pentacosadiynoic Acid (PDA), Arachidic Acid and Porphyrin were considered for deposition onto a Nickel film and were later topped with a small metal contact to complete the metal insulator metal diode assembly.Optical, electrochemical and electrical characterization were performed to check the quality of deposition of the thin insulator film and to analyze its material properties. Specifically, UV spectroscopy, atomic force microscopy and infrared spectroscopy techniques were utilized for this purpose. An electrochemical study was performed with the insulating monolayers deposited using the LB method on an Indium Tin Oxide coated glass substrate.Picoammeter measurements on the metal insulator metal junctions showed improved tunneling characteristics with fewer pinholes in the film after UV initiated polymerization. This was possible due to the intermolecular crosslinking in the film which was induced by the UV exposure. This was confirmed with the detection of more pronounced peaks at C=C vibration frequencies.

Interaction dynamics in small networks of nonlinear elements

We study a small circuit of coupled nonlinear elements to investigate general features of signal transmission through networks. The small circuit itself is perceived as building block for larger networks. Individual dynamics and coupling are motivated by neuronal systems: We consider two types of dynamical modes for an individual element, regular spiking and chattering and each individual element can receive excitatory and/or inhibitory inputs and is subjected to different feedback types (excitatory and inhibitory; forward and recurrent). Both, deterministic and stochastic simulations are carried out to study the input–output relationships of these networks. Major results for regular spiking elements include frequency locking, spike rate amplification for strong synaptic coupling, and inhibition-induced spike rate control which can be interpreted as a output frequency rectification. For chattering elements, spike rate amplification for low frequencies and silencing for large frequencies is characteristic.

Use of Langmuir Blodgett Thin Films for Rectification in Energy Harvesting Applications

Tunnel diodes have been found suitable for use in high frequency rectification for energy harvesting applications in a rectenna. For tunneling to take place in a metal insulator metal diode for rectification at THz frequencies, an ultrathin pinhole free insulating layer must be deposited between the metal layers for the diode to operate with small turn on voltages.Langmuir Blodgett (LB) thin film deposition is a useful technique that allows the deposition of conformal, uniform monomolecular layers with a precise control of thickness. Organic compounds such as Vinyl Stearate, 10-12 Pentacosadiynoic Acid and Porphyrin were considered for deposition onto a Nickel film and were later topped with a small metal contact to complete the metal insulator metal diode assembly.Several characterization techniques were used to check the quality of deposition of the thin insulator film and to analyze its material properties. UV spectroscopy, atomic force microscopy and infrared spectroscopy techniques were utilized for this purpose. An electrochemical study was performed with 10-12 Pentacosadiynoic acid deposited using the LB method on an Indium Tin Oxide coated glass substrate. Along with these characterization results, the current voltage characteristics of the diode behavior as well as its suitability for detection or energy harvesting will also be reported.

An assessment of reference exposure in analogic and digital mammographic units

Abstract In this study, the incident air kerma ( K i,a ), half-value layer (HVL), output and voltage accuracy for 28 mammography services were evaluated. All mammographs had high frequency rectification, a focus-film distance greater than 60 cm, automatic exposure control, a Mo–Mo anode-filter combination, and compression system. Twenty-three evaluations were made of analogic imaging systems and 21 of digital imaging systems, two of which were full field digital mammography units. The K i,a was measured in the beam radiation with a 6 cm 3 ionization chamber, calibrated for a mammography range of energy. A standard American College of Radiology mammographic phantom simulated a skull caudal incidence. The average, minimum, and maximum K i,a values were 10.13 mGy, 3.92 mGy, and 30.41 mGy, respectively. However, when the analogic and digital systems are analyzed separately in two subsets, the values were 8.13 mGy, 3.92 mGy, and 11.78 mGy for the analogic systems and 12.33 mGy, 5.21 mGy, and 30.41 mGy for the digital systems, respectively. The results show that the K i,a values found in digital systems were higher than those in analogic systems, highlighting the differences between these acquisition systems. All HVL values, measured in the primary beam at 28 kV were found between 0.33 mm Al and 0.43 mm Al. Although the manufacture time of the equipment was approximately 146 months (~12 years) prior, the variation in output was between 0.071 mGy/mAs and 0.164 mGy/mAs for the entire sample.

Design of Miniaturized Antenna and Power Harvester Circuit on the Enucleated Porcine Eyes

This letter describes a prototype of a miniaturized rectifying antenna (rectenna) design for the wireless powering of an ocular device. In contrast to the conventional on-lens loop antenna, this letter presents a loop antenna with stepped structures for optimal impedance to the rectifier. The return loss of the antenna less than -15 dB at 3 GHz is accomplished in a contact lens with a diameter ranging from 10 to 15 mm. Additionally, the radio frequency (RF) rectifier and voltage-boosting network (VBN) are optimized to enhance the power conversion efficiency (PCE) by using the voltage boosting technique. Experimental results indicate that the optimal rectifier, which is fabricated with the TSMC 0.18- μm process, produces a dc output voltage of 2.94 V and a conversion efficiency of 31% across a resistive 3.5 k Ω load with an input power of +9 dBm. Moreover, the rectenna under the experiment with an enucleated porcine eye can be powered wirelessly with a transmitting device at a distance of 4 cm. The output power is 2.01 mW with a transmitting power of +32 dBm for the wireless ocular physiological monitoring (WOPM) system. Importantly, this letter demonstrates the feasibility of an optimal miniaturized on-lens rectenna design, capable of overcoming the RF power attenuation on the ocular tissue to increase the delivering distance and reduce the transmitting power.

Receptor trafficking hypothesis revisited: Plasticity of AMPA receptors during established status epilepticus

Status epilepticus (SE) is associated with a dynamic plasticity of postsynaptic neurotransmitter receptors. The plasticity of AMPA receptor (AMPAR)-mediated glutamatergic transmission during established SE (ESE), after development of benzodiazepine resistance, was evaluated. There was increased frequency and inward rectification of AMPAR-mediated excitatory postsynaptic currents at Schaffer collateral - CA1 pyramidal neuron synapses during ESE. Surface expression of the GluA1 subunit increased, and this was a consequence of N-methyl-d-aspartate receptor activation. Further, diminishing glutamate release by activation of somatostatin receptors prevented SE. These studies suggest that AMPAR-mediated glutamatergic transmission is strengthened during ESE.

Quantum theory of operation for rectenna solar cells

Optical rectennas, sub-micrometre antenna-coupled diodes, can directly rectify solar and thermal electromagnetic radiation, and have been proposed as an alternative to conventional semiconductor photovoltaics. We develop a comprehensive description of the operating principle of rectenna solar cells. In prior work classical concepts from microwave rectenna theory have been applied to the analysis of photovoltaic power generation using these ultra-high frequency rectifiers. Because of their high photon energy the interaction of petahertz frequency waves with fast-responding diodes requires a semiclassical analysis. We use the theory of photon-assisted transport to derive the current–voltage [I(V)] characteristics of metal/insulator/metal tunnel diodes under illumination. We show how power is generated in the second quadrant of the I(V) characteristic, derive solar cell parameters, and analyse the key variables that influence the performance under monochromatic radiation and to a first order approximation. The efficiency improves with reduced dark current under reverse bias and increasing incident electromagnetic power.

A new process for the fabrication of planar antenna coupled Ni–NiOx–Ni tunnel junction devices

Graphical abstractDisplay Omitted Highlights? Methods to fabricate planar, geometrically asymmetric Ni-NiOx-Ni tunnel diodes are developed. ? Planar structure decreased the parasitic capacitance enabling high cut-off frequency. ? Ni electrodes provided the surface oxidation control and low band edge offset with its native oxide. ? Asymmetric geometry of the electrodes resulted in electrical asymmetry across zero bias. ? Three Ni oxidation methods are studied to build a thin, but durable oxide for the tunnel barrier. Antenna coupled metal-insulator-metal (ACMIM) tunnel junctions are fast electromagnetic wave detectors shown to respond to radiation of wavelength as short as 1.6µm. In the design and fabrication of these devices, it is crucial to keep the RC time constant of the tunnel junction small to achieve the requisite cut-off frequency and adequate rectification efficiency. Junction geometry and the properties of the insulation layer between the metal antenna parts play an important role in determining both the time constant and the rectification effectiveness. In this paper we have designed and fabricated Ni-NiOx-Ni devices and performed three oxidation processes to optimize the insulation layer. Ease of manufacture over large areas is also a requirement for successful implementation. We detail two simple and low cost processes for the fabrication of Ni-NiOx-Ni tunnel junctions. These methods allow for the large area array implementations of the antenna coupled MIMs for the application in low-cost energy harvesting.

Differential Buck DC–DC Chopper Mode Inverters With High-Frequency Link

A circuit configuration and a circuit topological family of differential buck dc-dc chopper mode inverter with high-frequency link are proposed in this paper. The circuit configuration, the topology family, the instantaneous output voltage and the capacitance current feedback control strategy, the steady principle characteristic, and the design criteria for the key circuit parameters are fully investigated in this paper. The circuit configuration is differentially composed of two identical isolated bidirectional buck dc-dc choppers with the same input and output LC filters. These two choppers generate unipolarity sinusoidal pulse width modulation voltage waveforms with positive and negative half low-frequency cycle separately. Each dc-dc chopper consists of high frequency inverter, high frequency transformer, and high frequency rectifier. The circuit topological family includes six circuit topologies, namely, one-transistor forward mode, push-pull mode, push-pull forward mode, two-transistor forward mode, half-bridge mode, and full-bridge mode. Taking one-transistor mode circuit topology as example, the prototype is designed and implemented. The results from the theoretical analysis and principle test indicate that the inverters have advantages of high frequency galvanic isolation, simple topology, bidirectional power flow, single-stage power conversion, high conversion efficiency, high-quality output voltage waveform, and strong adaptability to various loads.

Printed Electronics for Flexible Applications

The application of roll-to-roll printing processes for the fabrication of polymer electronics on flexible films enables the mass production of low-cost electronic circuits and components. Being produced by the successive application of thin layered functional structures on flexible polyester film, the products end up being thin and flexible themselves.Example applications are discussed, all manufactured in roll-to-roll printing processes. A 13.56 MHz radio frequency rectifier was combined with an electrochromic display into a “smart object” that reveals the display information when brought into an electromagnetic field of an activator unit. Transparent conductive films on flexible substrates were realized by a high resolution roll-to-roll production process with structure sizes down to 10μm. They are suitable to replace indium tin oxide in applications such as touch screen displays.

Schottky Diode Based on Microcrystalline Silicon Deposited at 165°C for RFID Application

The design and fabrication of high efficiency low cost electronics components for commercial and industrial applications is very challenging. In this paper we introduce a fabrication of Schottky diode dedicated to high frequency rectification. The devices are prepared on Corning glass substrate with a configuration Au /µc-Si:H /Al and by using microcrystalline silicon as semiconductor. Photolithographic masks are used for diodes fabrication. Two processes are carried out to optimize Schottky diode characteristics. Silicon films are deposited in an usual RF PECVD reactor at low temperature (165°C). Current - voltage (I-V) characteristics are measured and plotted to determine the different parameters of Schottky contact such as ideality factor and rectifying ratio. At 13.56 MHz which is common in RFID frequency application, this Schottky diode in association with parallel load capacitor can be used to build an efficient rectifier.

The Research of Digital Soft Switching Arc-Welding Inverter

This paper discusses the characteristics of welding power supply, and then gives the design ideas of digital welding power. A full-bridge configuration which cooperates with high frequency transformer and rectifier circuit is used to be main circuit, and IGBT is the primary switch component. The leading leg achieves Zero Voltage Switching, and the lagging leg is Zero Current Switching by the combination of soft switching and inverter technology. We take UC3879 as the core of PWM controlling to carry out soft switching and TMS320LF2407A as the core of all controlling system. The control strategy adopts fuzzy-PID control.

Radio frequency rectification on membrane bound pores

Probing the interaction of biological systems with radio frequencies holdsgreat promise for research and drug screening applications. While a commonassumption is that biological systems do not operate at radio frequencies, we findthat currents due to ion transport through channels and pores in cell membranesare in the pA to nA range. These values translate via the average current⟨I⟩ = ⟨n⟩e/τd = ⟨n⟩ef to frequencies in the range of 1 MHz–1 GHz, where⟨n⟩ is the average number of ions transported andτd is the dwell time of the ions in the channel. It is thus desirable to have circuitry availablewhich facilitates radio frequency spectroscopy of ion transport. This will yield real-time invitro information on ion channel operation. Here we present measurements on the localinteraction of a radio frequency signal with single ion channels and pores. We find radiofrequency rectification and pumping on the channels and pores embedded in suspendedbilipid membranes, recorded in direct current measurements. This electromagneticmodulation can be used to probe the dynamics of ion channel conformational changes.

An efficient algorithm for generalised single-phase converter

This paper describes the various common converters and illustrates the working principle of single phase matrix converter that shows a single topology capable of performing all function required in basic converter. An algorithm is developed that enables a single-phase matrix converter (SPMC) to perform functions of a generalised single phase power electronics converter such as acting as a frequency changer, rectifier, inverter and chopper. This reduces the need for new converter hardware. The algorithm is implemented on computer simulation software Orcad Capture CIS version 9.1. Simulation results are presented for all five types of converters with a control input variable that decides the 1) type of converter and 2) type of output waveform. The simulated results verify the working and operation of a generalised converter based on SPMC.

RF doubling and rectification in three-terminal junctions: experimental characterization and Monte Carlo analysis

The feasibility of three-terminal junction devices for frequency doubling and rectification reaching the terahertz range is studied both experimentally and numerically (by means of Monte Carlo simulations). Experiments at room temperature up to 94 GHz for detection and to 4 GHz for doubling and phase detection are shown. The influence of the width of the branches and the shape of the junction (T-shaped vs. Y-shaped) on the frequency response of the devices has been studied. Cut-off frequencies found for frequency doubling are lower than for the rectifying operation of the devices. This difference is attributed to the slow characteristic time of carrier penetration into the stem.

Methods of generating superbroadband terahertz pulses with femtosecond lasers

This paper presents experimental results and an analysis of methods of generating terahertz (THz) radiation, using femtosecond laser sources: generation by photoconductive semiconductor antennas, nonlinear-optical generation of the difference frequency or optical rectification, and generation using optical breakdown in gases under the action of femtosecond pulses. An undoped semiconductor crystal of indium arsenide (InAs) located in a magnetic field, an electrooptic ZnTe crystal, an organic DAST crystal, and an optical spark in air were used as generators of THz radiation

A magnetorheological actuation system: test and model

Self-contained actuation systems, based on frequency rectification of the high frequencymotion of an active material, can produce high force and stroke output. Magnetorheological(MR) fluids are active fluids whose rheological properties can be altered by the applicationof a magnetic field. By using MR fluids as the energy transmission medium in such hybriddevices, a valving system with no moving parts can be implemented and used to control themotion of an output cylinder shaft. The MR fluid based valves are configured in theform of an H-bridge to produce bi-directional motion in an output cylinder byalternately applying magnetic fields in the two opposite arms of the bridge. Therheological properties of the MR fluid are modeled using both Bingham plasticand bi-viscous models. In this study, the primary actuation is performed using acompact terfenol-D rod driven pump and frequency rectification of the rod motion isdone using passive reed valves. The pump and reed valve configuration alongwith MR fluidic valves form a compact hydraulic actuation system. Actuatordesign, analysis and experimental results are presented in this paper. A timedomain model of the actuator is developed and validated using experimental data.

Solution-deposited ZnO-organic diodes with high current density and high frequency rectification under ambient conditions

Abstractn-ZnO/p-Pentacene and n-ZnO/poly(bis(dodecyl)quaterthiophene) (p-PQT-12) vertical p-n junction diodes were prepared on ITO-coated glass. A continuous film of ZnO nanoparticles was grown on the ITO glass by dip-coating and subsequent heat treatment of a zinc acetate film. Pentacene was then thermally evaporated to form the ZnO/Pentacene diode, whereas PQT-12 was spin coated for the ZnO/PQT-12 diode. Based on the band energies of ZnO, pentacene and PQT-12, for efficient carrier injection, gold was chosen as the top electrode to complement the ITO for both diodes. The microstructures of ZnO and pentacene films are studied by AFM and show a layer of pentacene grains with about twice the extent of the underlying layer of ZnO grains, implying substantial interfacial contact between them The current density-voltage (J-V) measurement shows that the maximum current density for ZnO/Pentacene and ZnO/PQT12 are 160 A/cm2 and 350 A/cm2 respectively. The rectification was characterized by observation of full input-half output waves. Data indicate that these devices can operate up to frequencies of 20 MHz and 9 MHz for ZnO/Pentacene and ZnO/PQT12, respectively, under ambient environment conditions. This rectification frequency is higher than other reported organic and polymer Schottky diodes under these conditions. Turn on voltages of these diodes are also much lower than for the reported organic and polymer diodes.

Radio frequency rectifiers based on organic thin-film transistors

One important technical hurdle that has to be overcome for using organic transistors in radio-frequency identification tags is for these devices to operate at rf frequencies (typically 13.56MHz) in the front end. It was long thought that organic transistors are too slow for this. In this letter we show that organic transistor based full-wave rectifier circuits utilizing pentacene, a p-channel organic semiconductor, can operate at this frequency with a useful efficiency. In order to achieve such high-frequency operation, we make use of the nonquasistatic state of the transistors.