AC Output Signal Research Articles

Research and Design of High-precision Voltage Sampling Circuit for Tumor Radiofrequency Ablation Medical Instrument

Radiofrequency ablation is a minimally invasive procedure in which tiny radiofrequency electrodes are implanted into the diseased tissue under the guidance of medical imaging (X-ray imager, CT or ultrasound), and neutral electrodes are attached to the skin of the body to carry out radiofrequency ablation, which is carried out by forming a circuit through the human body to the diseased tissue. At present, RF ablation can be applied to lung tumors, liver tumors, kidney tumors and certain heart diseases. The core component of tumor RF ablation surgery equipment is RF power source, which is a fixed frequency sinusoidal AC output signal with a frequency of 400-500Khz. The detection technology of RF voltage is extremely important, which determines the accuracy of RF ablation energy output and energy control. In this paper, we use STM32 microcontroller as the core of acquisition and control, and propose a simple and practical sampling method with high accuracy. Moreover, we have realized to control the voltage measurement error below 1% by using the error curve fitting method for software calibration.

The charging performance in contact electrification of fluorinated ethylene propylene surfaces by electrode bridge

Triboelectricity utilizes triboelectric nanogenerators (TENG) that transfer negative charges between two material surfaces that are in contact. Incomplete flow of charges results in charge accumulation on the material surfaces. In this study, we demonstrated that the accumulated charges could enhance induced output by contact electrification using electrode bridge (EB) to improve charge transfer mechanism. Triboelectric nanogenerator electrode bridge (TENG-EB) was fabricated using synergistic combination of polymer-polymer, polymer-metal, and metal-metal contacts during contact-electrification. Fluorinated ethylene propylene (FEP) film was fabricated using hot pressing technique. FEP crystallinity reached 85.8%, maximum temperature for ε r of FEP was 145 °C, and remanent polarization of FEP polymer was 4.2 µC mm – 2 . The individual events of the charge transfer during contact and separating of TENG-EB could be studied with a single electrode measurement. Separation of FEP, EB and electrode surfaces led to induced output of which signal was 4 times higher than TENG with non-EB. This mechanism utilized DC output that enhanced AC output signal for a given tapping frequency across a rectifier circuit. This new route is proposed for further research, development and invention in alternative energy field including energy harvesting and flexible electronic devices. • Charges event is demonstrated using electrode bridge (EB) induced output performance. • Triboelectric nanogenerator electrode bridge (TENG-EB) was fabricated based on synergistic combination of polymer-polymer, polymer-metal, and metal-metal contacts. • FEP-Al hot pressing is fabricated for electron blocking layer (EBL) has also played a vital role in blocking the electron overflow between a negative material and an electrode. • Output signal of TENG-EB is 4 times higher than that of a TENG non-EB.

Spin Hall Nano-Oscillator Based on an Antiferromagnetic Domain Wall

We propose here a high-frequency spin-Hall nano-oscillator based on a simple magnetic texture, such as a domain wall, located in an antiferromagnet with an easy-axis anisotropy type. We show that the spin current, polarized along the anisotropy axis, excites a conical precession of the N\'eel vector in such a domain wall, which allows obtaining a robust ac output signal---contrary to the planar precession in a uniform uniaxial antiferromagnet, where ac output is hard to achieve. The frequency of the auto-oscillations is easily tunable by the applied current up to the terahertz range, and the threshold current vanishes for a pure uniaxial antiferromagnet. By micromagnetic simulations, we demonstrate that the pinning of the domain wall is crucial for the oscillator design, which can be achieved in the nanoconstriction layout of the free layer.

RANCANGBANGUN RANGKAIAN INVERTER SPWM UNIPOLAR 1 FASA DENGAN PENGATURAN FREKUENSI OUTPUT


 
 
 Changing the dc sgnal to ac signal is done for te purpose of load regulations, such as the ac motor speed, heater and lamp. Inverter work is done by ac rectification first and then converted again to a 1 phase ac signal. The ac output signal is a sinosoidal PWM (SPWM) type of unipolar 220 volts from the input 24 volt dc voltage. Unipolar SPWM signal generation is done by a microcontroller with programming. The number of counts (resolutions) of the SPWM signal and the period are set from the amount in the register, can be set to 8 bits or other constants. The power part of the SPWM inverter is the N channel MOSFET bridge circuit H with IR2110 solid state driver. Step transformer as a load while step-up the inverter output voltage. Determination of the output frequency is set through a rotary encoder that can be adjusted up (increment) or down (decrement). There are 5 frequency variations, namely 30, 40, 50, 60 and 70 Hz. To get the inverter efficiency, the type of MOSFET used is chosen to have the type that has a low RDS (on) value and the right driving pulse, according to the switch configuration. Measurement of the output frequency is done by reading the image on the osciloscope. The observations show a frequency value that is almost the same as the constant. The test results show the difference in output voltage which is reduced at a 30 watt load.
 
 

Comparison of Some PWM Techniques for Control of a Single-Phase Inverter

Single-phase voltage inverters are used among others in relief supplies and DC-DC converters to the alternative middle tier. In these applications, the main purpose is to obtain a sinusoidal AC output signal whose amplitude and frequency can be controlled, as well as the low levels of THD. This document presents a comparative study of certain orders single-phase inverters techniques. The techniques used are studied; the results of the simulations will be discussed.

Piezoelectrically actuated vibrating flexible differential capacitances for electrostatic detection

Space exploration requires reliable measurements of space-radiation induced charge or its electric potential in a wide range in a satellite. Here, we report one pair of 3D printed soft multilayer differential capacitors, which are piezoelectrically actuated in vibration to convert the input static DC charge (high electric potential) into a measurable small dynamic AC output signal through charging and discharging between two differential capacitors. The fabricated prototype features linear responses to a high potential change and also high reliability. Moreover, the method proposed in this work is promising to achieve rapid manufacturing of functional devices in batch processing.

The design and fabrication of electromagnetic microgenerator with integrated rectifying circuits

PurposeThe paper focuses on design, fabrication and characterization of electromagnetic microgenerators with integrated rectifying circuits to convert AC output signal to DC one. The work includes research on simulation of voltage-rectifying circuits, including charge pump, realization of the experimental printed circuit board (PCB) with selected electronic circuits and the execution of the final structure with integrated rectifying circuit. Measurements were performed on these circuits.Design/methodology/approachElectromagnetic microgenerators include multipole permanent magnets secured on rotor three-phase brushless direct current (BLDC) motor and planar multilayer multiple coils. These were fabricated using low temperature co-fired ceramics (LTCC) technology. In our experiment, six rectifying circuits were simulated and tested with a structure consisting of eight layers of coils and with an outer diameter of 50 mm fabricated earlier.FindingsThe microgenerator with Graetz bridge generates higher output power than the modified charge pump at the same rotary speed. However, it is less stable for the distance change between the structure and the magnets than the modified charge pump, which has more constant output power in a wider range of load resistance.Originality/valueThe presented electronic rectifying circuits are novel for LTCC-based electromagnetic microgenerator application. The structure with integrated rectifying circuits allows generation of electrical output power larger than 100 mW at the rotor speed of about 8,000 rpm.

Hybrid renewable energy system with minimum noise wind turbine

In this study, a photovoltaic-wind hybrid renewable energy system has been examined and analyzed, with concentration on wind turbine to minimize generated noise. Mechanical and electrical analyses were performed. Harmonic electrical analysis on the wind turbine generator and electronic devices within the conversion system was conducted to get better performance. Mechanical vibration analysis was also done on selected wind turbine to estimate the forces and frequencies that may affect the blade during operation and cause noise and disturbance effects.It was found that Harmonics and total Harmonic Distortion were minimized after implementing an AC/DC/AC conversion system consisting of a diode full wave rectifier and an LC filter to stabilize the DC bus. Finally IGBT inverter was used to convert the DC signal into AC output signal with a useful frequency of 50 Hz after reshaping. The total harmonic distortion was minimized to 2.81%, less than the IEEE standards of 5% of the fundamental current frequency.Furthermore, it was also found that according to suggested arrangement of the hybrid system in this study, the blade of the proposed wind turbine, if operated even under its natural frequencies, its performance will be slightly affected resulting in minimized resonance effect.

Dynamic analysis of DC–DC converter internal to an offshore wind farm

This study investigates the feasibility of integrating a single-switch active rectifier layout in an offshore wind farm. The proposed active rectifier topology consists of cascade connection of a diode-rectifier and a DC–DC boost converter. A DC collection grid is considered inside the wind farm, which supplies power to a land grid. Each wind conversion units within the DC collection grid includes a turbine, a generator, and an active rectifier. The DC–DC stage of the active rectifier allows regulating the frequency of generator, controlling the DC voltage to follow the reference signal, mitigating the distortion or ripple in the current signal, and maintaining the fault-ride through capability of the wind farm. The AC output signal from the wind-turbine-generators is converted to DC signal through a non-controlled full-bridge diode rectifier and a controlled DC–DC converter. The dynamic model of the DC–DC boost converter cascaded with the diode-rectifier is derived; and the contribution of pulse width modulation (PWM)-controller to the mitigation of signal variations is evaluated. The results prove consistency of the closed loop PWM-controller, which reduces significantly the gain of disturbances. The results are presented in the form of small-signal transfer functions and simulated using MATLAB software.

Lowest of AC–DC power output for electrostrictive polymers energy harvesting systems

Advances in technology led to the development of electronic circuits and sensors with extremely low electricity consumption. At the same time, structural health monitoring, technology and intelligent integrated systems created a need for wireless sensors in hard to reach places in aerospace vehicles and large civil engineering structures. Powering sensors with energy harvesters eliminates the need to replace batteries on a regular basis. Scientists have been forced to search for new power source that are able to harvested energy from their surrounding environment (sunlight, temperature gradients etc.).Electrostrictive polymer belonging to the family of electro-active polymers, offer unique properties for the electromechanical transducer technology has been of particular interest over the last few years in order to replace conventional techniques such as those based on piezoelectric or electromagnetic, these materials are highly attractive for their low-density, with large strain capability that can be as high as two orders of magnitude greater than the striction-limited, rigid and fragile electroactive ceramics. Electrostrictive polymers sensors respond to vibration with an ac output signal, one of the most important objectives of the electronic interface is to realize the required AC–DC conversion. The goal of this paper is to design an active, high efficiency power doubler converter for electrostrictive polymers exclusively uses a fraction of the harvested energy to supply its active devices. The simulation results show that it is possible to obtain a maximum efficiency of the AC–DC converter equal to 80%. Premiliminary experimental measurements were performed and the results obtained are in good agreement with simulations.

A 450°C High Voltage Gain AC Coupled Differential Amplifier

APEI, Inc. designed, fabricated and tested a high gain AC coupled differential amplifier based on a custom-built silicon carbide (SiC) vertical junction field effect transistor (VJFET). This SiC differential amplifier is capable of high temperature operation up to 450 °C, at which a high differential voltage gain of more than 47 dB is maintained. This high gain AC coupled differential amplifier can be integrated with harsh environment sensors that deliver weak AC output signals to improve signal quality and noise immunity.

An All Silicon Carbide High Temperature (450+ °C) High Voltage Gain AC Coupled Differential Amplifier

APEI, Inc. designed, fabricated and tested a high gain AC coupled differential amplifier based on a custom-built silicon carbide (SiC) vertical junction field effect transistor (VJFET). This SiC differential amplifier is capable of extreme temperature operation up to 450 °C, at which a high differential voltage gain of more than 47 dB is maintained. This high gain AC coupled differential amplifier can be integrated with high temperature sensors that deliver weak AC output signals to improve signal quality and noise immunity.

SiC flame sensors for gas turbine control systems

The research and development activities carried out to develop a SiC flame sensor for gas turbines utilized for power generation are discussed. These activities included the fabrication and characterization of SiC UV photodiodes and small SiC signal diodes as well as the designing and testing of production flame detector assemblies. The characteristics that make this solid state flame detector particularly useful for dry low NO x (DLN) premixed oil and natural gas fuels will be described. Since this device provides both analog dc and ac output signals, turbine combustor mode tracking, combustion flame dynamics and flame intensity tracking have been demonstrated. Sensors designed for production have been built, qualified and field tested. These sensors are now being installed in gas turbine power plants and are a component part of the turbine control system. This development has resulted in the first commercialized turbine control application to use SiC electronic devices.

A two-dimensional visible/infrared detector based on μc-Si:H p–i–n structures

We present preliminary results on the analysis and application of an optical detector for imaging light contours. The sensor has a two-dimensional structure and uses a TCO/ μc–p–i–n Si:H configuration as the active device and two lateral ohmic contacts to convert the projected light image into a lateral output photovoltage. A steady-state light pattern was used to simulate the image, in addition to a smallest intensity scanner beam which moved across the device creating an ac output signal. This signal depends on the position, intensity and homogeneity of the light pattern. A bidimensional model to explain the sensor performance is presented based on a small-signal ac circuit analysis.

A GaAs upconverter MMIC with an automatic gain control amplifier for 1.9 GHz PHS

A newly developed GaAs upconverter MMIC with an automatic gain control (AGC) amplifier is presented. The design objectives, considerations, problems, and their solutions are described. The circuit is designed for a 1.9 GHz radio-frequency transceiver for the Japanese Personal Handyphone System applications. The features of the upconverter are: (1) on-chip 50 /spl Omega/ impedance matching for all AC input and output signals; (2) a doubly balanced Gilbert cell and a two-stage AGC amplifier with matching circuits that provide 23.0 dB conversion gain, -39 dBc LO suppression, -23 dBc image suppression, and 30 dB gain control; (3) an adjacent channel power of -70 dBc, and (4) a die size of only 2.87 mm/sup 2/ (2.52 mm/spl times/1.14 mm).

Uninterruptible Power Supplies

A power train of an uninterruptible power supply selectively transforms its load from a primary source of power to a reserve source of power under control of a stored program control operating in real time. A microprocessor operating in conjunction with a prioritized interrupt controller and a plurality of external counters monitors and responds to signal conditions existing at various points of the power supply. In particular, the amplitude of a primary AC voltage source is sampled at precise angles of the sinusoidal waveform in response to a comb pulse waveform generated to conform to the actual period of the primary AC voltage. The frequencies range is determined by comparing a count interval to the period of the primary AC voltage. Relative power flow from the primary AC voltage source and a reserve AC voltage signal is controlled by relative phasing of the two signals. The reserve AC voltage signal is adjusted in phase during normal operation when all power is supplied by the primary AC voltage source by comparison to an AC output signal of the power supply to either null power dissipation in the generator of the reserve AC voltage signal or to supply charging current to its energizing DC voltage source.

High fidelity hearing aid amplifier

A single integrated circuit chip is provided with transistors, diodes, resistor and capacitors thereon for forming a variable gainamplifier (40) and gain control circuitry which provides a level dependent frequency response characteristic, operative at low signal levels to enhance gain at higher frequencies relative to that at lower frequencies. The gain control circuitry includes logarithmic rectifier means (48) operative to develop an AC output signal having a peak value varying as a logarithmic function of a signal level which may be that at the output of the variable gain amplifier (40). The AC output signal so developed is applied to a peak detector circuit in a compression ratio control circuit (46) to develop a DC signal which is amplified by a DC amplifier and applied to a control input of the variable gain amplifier (40).

Square-Wave Operation of a Thermal Conductivity Detectort†

SUMMARY Equipment is described for the operation of thermal conductivity detectors with square-wave bridge current. The resulting ac output signal allows amplification without the need for low-level choppers. With phase-locked demodulation of the amplified signal, bridge unbalance signals of the order of 10 nV can be detected. This performance exceeds the requirements of presently available detector cells, which produce noise levels of the order of 100 nV. The instrument is compatible with most existing hot wire detectors and may be used with economical recorders. Air and other permanent gases can be reliably analyzed at levels of 0.02 μl, with detection limits of the order of 0.002 μl. This performance makes the instrument attractive in the field of air pollution and opens the way to further research in the design of low-noise detector cells.

Dynamic polarization detection

The azimuth angle of the plane of polarization of linearly polarized light is measured accurately by an electro-optically modulated opto-electronical device. The two ac output signals show up a phase difference which is linearly dependent on the azimuth angle. Continuously changing azimuth angles can be measured within 1 degree or better; changes in the azimuth angle as fast as 3 × 10 4 rad/sec are easily followed by the detection electronics.

Development and Application of an Apparatus for Continuous Measurement of Muscle Extensibility and Elasticity Before and During Rigor Mortisa,a,b

SUMMARYAn apparatus was developed to study the extensibility and elasticity characteristics of muscle fibers before and during the onset of rigor mortis. A variable load (weight) was applied to a muscle specimen held in a chamber under controlled conditions maintained by a thermostatically regulated cartridge heater, cooling coil, and gas inlet. A solenoid cell, energized by a cyclic timer, was used to release and apply the load in a direction longitudinal to the vertically mounted specimen. A lever attached to the specimen‐loading, system transmitted the extensibility and elasticity of the specimen to the armature of a differential transformer. The output voltage, from the secondary transformer winding was directly proportional to displacement of the armature. This AC output signal was rectified and transferred to a DC recording microammeter. The time course of rigor mortis was not influenced by loading and unloading interval or size of muscle strip, and was found to be temperature‐dependent, being prolonged as temperature was decreased. The white fibers of the semitendinosus muscle were found to have a considerably longer delay phase than the red fibers. The relations between the time course of rigor mortis and the ultimate properties of the muscle were discussed.