Fundamental frequency

About: Fundamental frequency is a research topic. Over the lifetime, 8941 publications have been published within this topic receiving 131583 citations.

Power System Frequency Estimation by Using a Newton-Type Technique for Smart Meters

Abstract: This paper proposes a single-phase grid voltage fundamental frequency estimation technique for smart meters. The technique relies on a nonlinear Newton-type algorithm and a recursive differentiation filter (NTA–DF). It can reject the negative effects caused by dc offset, harmonics, notches, and spikes. When compared with a NTA technique based on least-squares (NTA–LS), the proposed one reduces matrix dimensions, avoids matrix inversion, and is computationally efficient, thus requiring less hardware and associated cost for real-time implementation. Moreover, unlike the NTA–LS technique, the NTA–DF shows less sensitivity to the presence of harmonics. Simulation and experimental results are presented to verify the performance of the proposed technique.

Miniaturized self-q-switched frequency-doubled laser

Abstract: A diode-pumped monolithic laser is fabricated from a self-doubling host material co-doped with two ionic species, where one ionic dopant converts pump radiation to continuous radiation at a fundamental frequency and the other dopant acts as a saturable absorber to Q-switch the fundamental radiation which is then frequency doubled to produce pulsed high-intensity green light, the green light being either outputted or further frequency-doubled, into pulsed coherent UV radiation, by means of a non-linear crystal.

Two-dimensional model of vocal fold vibration for sound synthesis of voice and soprano singing.

Abstract: Voiced sounds were simulated with a computer model of the vocal fold composed of a single mass vibrating both parallel and perpendicular to the airflow. Similarities with the two-mass model are found in the amplitudes of the glottal area and the glottal volume flow velocity, the variation in the volume flow waveform with the vocal tract shape, and the dependence of the oscillation amplitude upon the average opening area of the glottis, among other similar features. A few dissimilarities are also found in the more symmetric glottal and volume flow waveforms in the rising and falling phases. The major improvement of the present model over the two-mass model is that it yields a smooth transition between oscillations with an inductive load and a capacitive load of the vocal tract with no sudden jumps in the vibration frequency. Self-excitation is possible both below and above the first formant frequency of the vocal tract. By taking advantage of the wider continuous frequency range, the two-dimensional model can successfully be applied to the sound synthesis of a high-pitched soprano singing, where the fundamental frequency sometimes exceeds the first formant frequency.

Power supply and impedance matching to drive technological radio-frequency plasmas with customized voltage waveforms

Abstract: We present a novel radio-frequency (RF) power supply and impedance matching to drive technological plasmas with customized voltage waveforms. It is based on a system of phase-locked RF generators that output single frequency voltage waveforms corresponding to multiple consecutive harmonics of a fundamental frequency. These signals are matched individually and combined to drive a RF plasma. Electrical filters are used to prevent parasitic interactions between the matching branches. By adjusting the harmonics’ phases and voltage amplitudes individually, any voltage waveform can be approximated as a customized finite Fourier series. This RF supply system is easily adaptable to any technological plasma for industrial applications and allows the commercial utilization of process optimization based on voltage waveform tailoring for the first time. Here, this system is tested on a capacitive discharge based on three consecutive harmonics of 13.56 MHz. According to the Electrical Asymmetry Effect, tuning the phases between the applied harmonics results in an electrical control of the DC self-bias and the mean ion energy at almost constant ion flux. A comparison with the reference case of an electrically asymmetric dual-frequency discharge reveals that the control range of the mean ion energy can be significantly enlarged by using more than two consecutive harmonics.

Controlling the Carrier-Envelope Phase of Raman-Generated Periodic Waveforms

Abstract: We demonstrate control of the carrier-envelope phase of ultrashort periodic waveforms that are synthesized from a Raman-generated optical frequency comb. We generated the comb by adiabatically driving a molecular vibrational coherence with a beam at a fundamental frequency plus its second harmonic. Heterodyne measurements show that full interpulse phase locking of the comb components is realized. The results set the stage for the synthesis of periodic arbitrary waveforms in the femtosecond and subfemtosecond regimes with full control.