Showing papers on "Total harmonic distortion published in 1986"

MOS transconductors and integrators with high linearity

Abstract: MOS transconductors are discussed in which the transistors determining the transconductance do not carry bias current, operate with large gate-source voltage, and are signal-driven in such a way that their nonlinearities are eliminated. An integrator implemented using one of the proposed circuits exhibited measured total harmonic distortion of less than 0.1% for differential input signals of 2.5 V p-p, and less than 1% for 5 V p-p.

Harmonics from Transformer Saturation

Abstract: Saturation effects in transformers and shunt reactors can produce harmonics in power systems. Their magnitude can sometimes be found with an electromagnetic transients program, by going from an approximate linear ac steady-state solution directly into a transient simulation in which the nonlinear effects are included. In lightly damped systems, such simulations can take a long time, however, before the distorted steady state is reached. Therefore, another method was developed which uses superposition of steady-state phasor solutions at the fundamental frequency and at the most important harmonic frequencies, with nonlinear inductances represented as harmonic current sources. This method can either be used by itself, or as an improved initialization procedure for electromagnetic transients programs.

The development of harmonic distortion in pulsed finite-amplitude ultrasound passing through liver.

Abstract: The progressive development of finite-amplitude distortion of ultrasonic pulses has been investigated in excised bovine liver using pulsed focused ultrasonic beams at nominal frequencies of 2.5 and 3.5 MHz. Both the transducers and the powers used were those which may be encountered with clinical imaging equipment. Significant distortion of the waveform was observed to occur, particularly at higher powers. For example, at 2.5 MHz, with a mean input pressure (p0) of 0.58 MPa, the second harmonic in the pulse spectrum showed a maximum value 10.5 dB below the fundamental and the highest third harmonic component was 19 dB below the fundamental. These particular observations illustrate that finite-amplitude distortion may be of considerable significance in the transmission through tissue of ultrasonic pulses during diagnostic scanning.

A New Static Var Compensator for an Arc Furnace

Abstract: This paper presents the design of an electronic compensator that can compensate the reactive current drawn by an arc furnace. Consisting of three independent single-phase pulse-width modulated (PWM) inverters, the proposed compensator responds quickly to any sudden load changes and compensates both the fundamental displacement current and the harmonic distortion current drawn by the load. Unlike conventional static var compensators, the electronic compensator can also supply the active current demanded by the load if an energy source independent of the utility is available. Simulations are conducted, including the modelling of the furnace current and voltage waveforms during the early stage of scrap melting, in order to determine the effectiveness of several suggested detection methods that can be used to separate the active and reactive components of the furnace current. Actual waveforms observed on a local furnace are included that corroborate the computer modelling. Experimental results indicate that the electronic compensator equipped with a suitable detection circuit can accurately compensate an arc furnace.

New PWM switching strategy for microprocessor controlled inverter drives

Abstract: A new high-voltage suboptimal (HVSO) pulse-width modulation (PWM) switching strategy is presented which can be used at high fundamental PWM voltages to achieve a smooth, transient-free, low harmonic distortion, transition from the PWM to quasisquare-wave mode. The design philosophy underlying the development of the new HVSO strategy is aimed at reproducing the special features and desirable characteristics of the optimised PWM strategy, using a simple and efficient microprocessor implementation. The full theoretical development of the new HVSO strategy is presented; and experimental results, from a microprocessor controlled PWM inverter drive, are provided which confirm this theoretical development. It is shown that the new HVSO strategy is superior to all existing PWM strategies, and can be implemented simply and efficiently on a microprocessor controller with only minor modifications to the existing PWM microprocessor implementations. In addition, a new hybrid PWM strategy is proposed and demonstrated, which combines the HVSO strategy with a previously developed suboptimal strategy. It is shown that this new hybrid PWM strategy can be used to cover the complete voltage/frequency range of the drive system up to and including the quasisquare wave mode, with minimised total harmonic distortion.

Generalization of conditions for 100% efficiency and nonzero output power in power amplifiers and frequency multipliers

Abstract: In a previous paper, basic limitations on the switch current and voltage waveforms in single-ended switching-mode tuned power amplifiers have been discussed for perfect filtering of harmonics at the output. This paper expands on the previous idea by providing more general conditions for both nonzero output power and 100-percent efficiency at any number of harmonics in the output power. The load network and load are assumed to be passive and linear. It is shown that it is not possible to achieve both nonzero output power and 100-percent efficiency. In switching-mode circuits, it is not possible to eliminate both the transistor turnon switching loss and the transistor turnoff switching loss while obtaining nonzero output power; at least one of the switching losses must be nonzero at nonzero output power. The results presented here are useful in synthesis and analysis of high-efficiency power amplifiers and frequency multipliers.

Harmonic-Free Utility/DC Power Conditioning Interfaces

Abstract: The typical design of a power circuit now used to interface a dc system to the electric utility is such that a heavily distorted current is drawn from the utility. Since this distortion has the potential to interfere with the normal operation of the utility and its load, efforts are underway to develop power-conditioning interfaces that draw a nearly harmonic-free ac current waveform. The design of these interfaces is discussed. The salient issues of the power circuit's topology and its control are presented.

Digital/analog converter

Abstract: A digital/analog converter of the present invention is a pulse width modulation type, and is provided with a 2 N (N: the number of bits of digital data to be converted) notation counter circuit for counting clock pulses, pulse formation circuit which is given the counting output of the counter circuit and the digital data and outputs a pulse signal being varied its pulse width and pulse cycle period corresponding to the contents of the digital data and being decided the sum of the pulse widths of the pulse signal in the 2 N clocks period corresponding to the same, and means which selects corresponding to the pulse one of two potentials different in level and which composed the selected potential, so that the harmonic spectrum of an analog signal obtained as the output of the composite means is larger in the high band and smaller in the low band, resulting in that the digital/analog converter less in the harmonic distortion without using resistance of high accuracy is obtainable.

Realization of a New Inverter Circuit for Direct Photovoltaic Energy Feedback into the Public Grid

Abstract: A new regulated utility interactive inverter for direct photovoltaic energy feedback to the mains has been realized. A modulated buck converter converts the photovoltaic dc current to a rectified 50-Hz sine wave current, and the following self-commutated half-bridge generates a 50-Hz sine wave current, which is fed into one phase of the public power grid. This nonclassical inverter needs only three power transistor switches and isolates the grid and the photovoltaic array using a commercial 50-Hz transformer. It acts as a current source, and due to pulsewidth modulation its output is a sine wave current with very low total harmonic distortion of one percent. The overall efficiency of the 1-kW prototype is at least 88 percent between 250 and 1000 W, and the projected efficiency is over 90 percent for 1-20 kW. Furthermore, a circuit which tracks the maximum power available from the photovoltaic generator has been developed. This circuit regulates the input power to its maximum by detecting the phase angle between the voltage and power ripples at the inverter input.

Deadbeat controlled PWM inverter with parameter estimation using only voltage sensor

Abstract: A new control technique based on deadbeat control theory is proposed to obtain a nearly sinusoidal PWM inverter output voltage using only a voltage sensor. The closed loop sampled-data feedback scheme inherently results in very fast response to load disturbance and nonlinear load, producing low total harmonic distortion. Parameter estimation of the plant provides a type of self-tuning of the proposed controller. This paper presents a theoretical analysis, simulation and experimental results for a single phase PWM inverter controlled by an Intel 8086 microprocessor.

CMOS implementation of an immediately adaptive delta modulator

Abstract: The modulator is described at the system level by analyzing the system transfer function, stability, frequency response, and quantization noise. Individual circuit blocks are explained at device level. A comparator design which is based on presenting an amplified signal to a pull-up pull-down latch, commonly used in dynamic RAMs, is described. The immediately adaptive delta modulator (IADM) was fabricated in a 3.5-/spl mu/m twin-tub CMOS process. An experimentally measured signal-to-noise ratio of 91 dB across the audio band (20 Hz-20 kHz) with a total harmonic distortion of less than 0.17% is reported. These results demonstrate the potential of this topology for 16-bit audio-band A/D conversion.

Television sound signal processor

Abstract: An IF signal filter (16) in the IF sound channel of a television receiver exhibits peak amplitude responses (45.95, 41,18 MHZ) which are unsymmetrical and slightly offset from the nominal picture and sound carrier frequencies (45.75, 41.25 MHZ) by an amount dictated by the amount of tilt introduced by the tuner (12) and the IF signal processing section (14). As a result, a filtered IF signal applied to a sound demodulating system (22) exhibits a substantially symmetrical characteristic with respect to both the sound and picture carrier frequencies, yielding reduced audio buzz and harmonic distortion. The invention can also be employed in other video equipment such as video cassette recorders

Digital Simulation of PWM Induction Motor Drives for Transient and Steady-State Performance

Abstract: In this paper, the influence of nonsinusoidal voltage excitation applied to a squirrel cage induction motor is investigated using direct three-phase machine simulation method. Computer packages are developed to generate various types of inverter modulation techniques, namely the sine, step, and current impressed schemes. These packages together with a three-dimensional plotting subroutine are used to investigate the characteristics of an inverter-fed induction motor system. The effects of switching frequency ratio, overmodulation, and start-on machine waveform characteristics are investigated. Harmonic distortion comparisons between sine and step modulation schemes are presented. A vector controller-driven current-impressed scheme are simulated. The effect of varying hysteresis band in a current-impressed scheme is discussed.

System for alleviating harmonic distortion

Abstract: A system is provided for alleviating harmonic distortion in a power supply having an AC input, a full wave rectifier and filter capacitors. The rectified voltage is chopped at a frequency that is higher than the frequency of the original AC waveform. The higher frequency cycle is provided by timing means coupled to the gate of a FET. The chopped and rectified voltage is stored in an inductor device during one portion of the higher frequency cycle and the energy from the inductor device is transferred to the filter capacitors during another portion of the higher frequency cycle. A reverse protection diode, and a capacitor for delivering high frequency energy to the FET are connected across the output of the full wave rectifier.

A CMOS slope adaptive delta modulator

Abstract: A slope adaptive A/D converter that reduces quantization noise through oversampling and feedback will be presented. A dynamic range of 90dB in the audio band, 15b resolution and total harmonic distortion of 0.17% at 1kHz has been achieved using a 3.5μm process.

Design of a System for Automated Measurement and Statistics Calculation of Voltage and Current Harmonics

Abstract: The design and operation of a portable, personal computer-based system for the measurement and processing of data on 60 Hz. and harmonic current and voltage amplitudes and phases, and for the production of statistics and time trends on those quantities is described. Over the data acquisition interval, which may be several days in length, the system calculates and stores for each selected harmonic frequency of each selected voltage or current channel, statistics chosen from among: Mean, Mean Square Value, Variance, Maximum, Minimum. Trends in composite quantities such as Telephone Influence Factor and Total Harmonic Distortion may also be calculated over the interval. Samples of the graphical presentation of statistical results are included.

MSW-SER Based Tunable Oscillators

Abstract: Tunable Magnetostatic Wave Straight Edge Resonators (MSW-SERs) offer an alternative to YIG spheres and varactor diodes in microwave oscillators. Work on MSW-SERs is extended to coupling with active devices. Interactions increase insight into resonator characteristics. A brief review of resonator-based microwave oscillator topologies precedes a survey of available YIG/GGG materials and coupling structures. Circuit related properties of the MSW-SER are presented as a basis for design. Circuit topologies are compared and the negative resistance topology is selected. Several examples of tunable oscillators in the L, S, and K microwave frequency bands will be given with emphasis placed on tuning bandwidth, power handling, harmonic distortion and phase noise characteristics.

Methods of reducing harmonic distortion in continuous wave seismic exploration

Abstract: Described is a method of driving a seismic vibrator with a control signal to produce an output signal having minimized harmonic distortion. The method includes the steps of producing a plurality a harmonic distortion signals related to a fundamental frequency of the control signal. The phase and amplitude of said harmonic distortion signal is varied to produce with the vibrator suites of variations of the distortion signal. From among suites of variations there is selected that harmonic distortion signal having phase and amplitude values which produce a minimum value in harmonic distortion signal amplitude. The steps are repeated for different fundamental frequencies and the selected signals are summed with their related fundamental frequencies to produce a vibrator sweep control signal. The seismic vibrator is driven with the control signal to produce an output in which harmonic distortion is significantly attenuated.

Thyristor controlled reactors as harmonic sources in HVDC convertor stations and AC systems

Abstract: Thyristor controlled reactors (TCRs) are a relatively new source of harmonic distortion in power systems. The steady-state balanced (or characteristic) harmonics are easily calculated and are well known. Other noncharacteristic harmonics can, however, be generated by TCRs. A detailed representation is therefore necessary which will consider all types of imbalance, be it in the TCR or in other parts of the total system to which they are connected. It is also important to consider the effect of connecting TCRs to systems which do not have a high fault level (weak AC systems) and to consider the effect of control feedback on harmonic generation. The methods by which these factors can be included in calculations of nonideal systems are the subject of this paper. The methods are illustrated by example.

An 8b 250MHz A/D converter

Abstract: An 8b converter, fabricated in a 5GHz, oxide-isolated bipolar process, will be reported. Full power bandwidth is 125MHz. The packaging used for the converter accomodates a power dissipation of 12W.

Amplitude control in a twin-T bridge RC-oscillator using a window comparator

Abstract: The paper describes amplitude control which is achieved by restoring, during each oscillation period, the voltage at the capacitor connected between the inner node and ground of the twin-T bridge RC-oscillator. The calculations of the amplitude transient, steady-state waveforms and total harmonic distortion are given. All calculations were experimentally verified.

Efficient FM-AM Conversion through Injection-Locking of an X-Band Gunn Oscillator

Abstract: This paper describes experimental observations on the amplitude modulation of a 9.347 GHz Gunn oscillator when it is injection-locked by an FM signal. The dependence of both the FM-AM conversion efficiency and the harmonic distortion of the detected signal on the system parameters is discussed in detail. Numerical analysis for the system is also presented. The investigations carried out indicate that an injection-synchronized microwave oscillator can be used as an efficient FM-AM converter so that together with an AM detector, it can serve the purpose of a faithful FM demodulator, expecially for low-index FM signals.

Realization of Linear High-Frequency Transconductance in CMOS-Technology

Abstract: It is shown that a CMOS class AB voltage-current converter circuit can be used as a wideband transconductor with variable highly linear transconductance. Linearity error less than 0.1% and THD of 0.16% for output signal current of 200% of the quiescent current value, and bandwidth of 5 MHz were measured on experimental chips. In addition, the circuit generates a useful square-law function.

Amplifier/corrector, in particular for base band digital links.

Abstract: A cell for amplification and frequency correction is defined by an operational amplifier AOP provided with a negative-feedback resistor R and an output resistor of like value in parallel with a capacitor C. The inverting input of the amplifier AOP is connected to two groups of diodes in parallel which are moreover AC uncoupled. The same is true for the output S of the stage. All these diodes are supplied in the same direction by a controlling direct current I resulting from a voltage VCC. It turns out to be possible to vary greatly both the gain and selectivity characteristics of the amplifier stage, without however acquiring prohibitive harmonic distortion. Several stages of this type make it possible to define an amplifier/corrector for base band digital links, in particular in bifilar lines.

Distortion compensation circuit

Abstract: PURPOSE:To cancel automatically deterioration of the characteristic of a device by measuring automatically a harmonic distortion of a pilot signal and using a differential amplifier so as to compensate a harmonic distortion generated between a transmitter and a receiver depending on the quantity of the distortion. CONSTITUTION:A transmission signal superimposed with a pilot signal is sent from the sending side. A differential amplifier 7 of a distortion compensating circuit 6 amplifies an output signal of a receiver 5, the distortion of the output is extracted by BPF 8 and a detector 9 converts it into a DC component. A comparator 10 controls an FET 11 when the DC component of the output of the detector 9 is larger than a reference voltage Vref. The FET11 acts like a variable resistive element and changes the value of the variable resistive element 11 in proportion to the degree that the said DC component is larger than the voltage Vref. As a result, an FET 13 acts like a distortion generating circuit to generate the distortion component. The component is fed to the differential amplifier 7 in opposite phase to the reception signal and the adjusted component is reduced.

A linearized model of a twin-T RC oscillator employing an amplitude control system with multipliers

Abstract: A twin-T bridge RC oscillator with a system of amplitude control which uses multipliers can have fast amplitude transient response and low distortions simultaneously. A linear model of the amplitude control system is herein discussed and used to derive the transient response for small amplitude steps. The model indicates a dependence of the response time on the oscillator amplitude. The effect of a loop filter for further reducing total harmonic distortions (THD) is analysed. Measured results are given for an experimental oscillator with the oscillation frequency f0 = 1·45 KHz. The circuit achieved THD less than 0·035% for the output voltage amplitude Vm up to 12 V with ± 15V power supplies while maintaining transient response below eight periods for vm  5 V.

Meter and measurement of harmonic distortion under great power of iouderspeaker

Abstract: The measurment is aimed at measuring harmonic distortion under great power of speakers. In a common room the parameters such as frequency response, sensibility of spearer. radio, TV. recorder and hall acoustic devices can be measured. The results are as accurate as those in a muffled room. By the invention a large funds for building muffled room can be saved. The meter is mainly characterised by its signal proccessing system with A/D-microcomputer-D/A, in which the design of hardware and software has originality.

Noise squelch circuit

Abstract: PURPOSE:To widen the operating range of squelch and to prevent malfunction due to harmonic distortion with simple circuit constitution by providing the 2nd FM demodulation section and applying squelch depending on the noise level from the 2nd FM demodulation section. CONSTITUTION:A signal is branched from an output of an intermediate frequency amplifier section 13 and fed to the 2nd FM demodulation section 20 having another center frequency than the 1st FM demodulation section 14. After the noise outputted from the demodulation section 20 is amplified and rectified, the result is fe to a comparison section 19, where the signal is compared with a specific potential so as to decide whether or not the input level corresponding to the potential is inputted. Since the demodulation section has a frequency selective characteristic in general, although the output noise level of the demodulation section 20 is decreased, the level of the demodulation signal due to the input signal is minimized by parting sufficiently the center frequencies of the demodulation sections 14 and 20. Thus, the malfunction due to harmonic distortion of spurious radiation of the demodulation signal is avoided.

The THD Characteristics of the Phase detector

Abstract: The paper presents an evaluation of the THD characteristics of the synmetrical and simple phase detectors, using exponential models of the detectors. By developing the output expressions into a series with Bessel-function coefficients, it is shown that, under certain conditions, the convergence is obtained. This approach results in relating the THD characteristics to other relevant electrical parameters of the circuits. Finally, a comparison is made between the simple and symmetrical detector with respect to their distortion characteristics.