Harmonic

About: Harmonic is a research topic. Over the lifetime, 44833 publications have been published within this topic receiving 495922 citations. The topic is also known as: overtone & partial.

Harmonic output of class-E RF power amplifiers and load coupling network design

Abstract: Class-E RF power amplifiers have advantages of explicit a priori designability, reproducibility, high efficiency, and low-stress operation of the power output devices. The authors give information on harmonic output and explicit design criteria for harmonic-suppression networks to be used with class-E power amplifiers.

A heuristic derivation of the uncertainty of the frequency determination in time series data

Abstract: Context: Several approaches to estimate frequency, phase and amplitude errors in time series analyses were reported in the literature, but they are either time consuming to compute, grossly overestimating the error, or are based on empirically determined criteria. Aims: A simple, but realistic estimate of the frequency uncertainty in time series analyses. Methods: Synthetic data sets with mono- and multi-periodic harmonic signals and with randomly distributed amplitude, frequency and phase were generated and white noise added. We tried to recover the input parameters with classical Fourier techniques and investigated the error as a function of the relative level of noise, signal and frequency difference. Results: We present simple formulas for the upper limit of the amplitude, frequency and phase uncertainties in time-series analyses. We also demonstrate the possibility to detect frequencies which are separated by less than the classical frequency resolution and that the realistic frequency error is at least 4 times smaller than the classical frequency resolution.

80〜200 GHz erbium doped fibre laser using a rational harmonic mode-locking technique

Abstract: Pulse trains with repetition rates as high as 80~200 GHz were obtained at 1.55 µm, using rational harmonic mode-locking with an erbium doped fibre laser. A fundamental repetition frequency (fosc) of 40 GHz was first generated by applying a 40 GHz modulation frequency to an LN intensity modulator in the fibre cavity, in which the longitudinal mode spacing (Δf) was 1.5 MHz. By rationally detuning the modulation frequency by Δf/n, the authors succeeded in obtaining a repetitive oscillation of (nfosc+Δf). The maximum frequency was 200 GHz, at which n corresponds to 5.

Selective Compensation of Power-Quality Problems Through Active Power Filter by Current Decomposition

Abstract: Active power filters (APFs) are used to compensate harmonics, reactive current and negative sequence fundamental frequency current of load current drawn by nonlinear loads. The flexibility of selective compensation, if provided in the control scheme, makes APF versatile device for compensation of reactive power, harmonic currents and unbalance in source currents and their combinations, depending upon the limited rating of the voltage-source inverter employed as an APF. The proposed scheme decomposes the load current into positive and negative sequence fundamental frequency active components, reactive component and harmonic components in synchronous reference frames. The control scheme performs with priority-based scheme, which respects the limited rating of the APF. The simulated results in MATLAB environment and experimental results of the developed prototype of APF are presented to validate the effectiveness of the proposed control scheme. Digital signal processor based implementation of control scheme is also detailed for selective compensation of power-quality problems with details of developed prototype.

Electron cyclotron emission radiometer upgrade on the DIII-D tokamak

Abstract: The electron cyclotron emission (ECE) heterodyne radiometer diagnostic on DIII-D has been upgraded with the addition of eight channels for a total of 40 The new, higher frequency channels allow measurements of electron temperature into the magnetic axis in discharges at maximum field, 215 T The complete set now extends over the full usable range of second harmonic emission frequencies at 20 T, covering radii from the outer edge inward to the location of third harmonic overlap on the high-field side Full coverage permits the measurement of heat pulses and magnetohydrodynamic fluctuations on both sides of the magnetic axis In addition, the symmetric measurements are used to fix the location of the magnetic axis in tokamak magnetic equilibrium reconstructions Also, the new, higher frequency channels have been used to determine central Te with good time resolution in low-field, high-density discharges using third harmonic ECE in the optically gray and optically thick regimes