scispace - formally typeset
Search or ask a question
Topic

Fundamental frequency

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


Papers
More filters
Journal ArticleDOI
TL;DR: In this paper, the phase-matching condition to convert the TE00 fundamental frequency to the TM00 or TM20 second harmonic was demonstrated by adjusting the crystal temperature, and the conversion efficiency was 1.5×10−4 at 2mW fundamental input power under the phase matching condition.
Abstract: Highly efficient second‐harmonic generation using a titanium in‐diffused LiNbO3 three‐dimensional optical waveguide was performed with the cw Nd : YAG laser at 1.064‐μm wavelength. The phase‐matching condition to convert the TE00 fundamental frequency to the TM00 or TM20 second harmonic was demonstrated by adjusting the crystal temperature. The conversion efficiency is 1.5×10−4 at 2‐mW fundamental input power under the phase‐matching condition. By using a low‐loss LiNbO3 optical waveguide, equipped with highly reflective cavity mirrors on the input and output surfaces, parametric oscillation is expected.

65 citations

Journal ArticleDOI
TL;DR: An analysis of pre- and postoperative voices of six patients with benign laryngeal disease showed that the N/S ratio for vowel /u/ in running speech consistently improved after surgery for all subjects, in agreement with their successful therapeutic results.
Abstract: A method of pitch‐synchronous acoustic analysis of hoarseness requiring a voice sample of only four fundamental periods is presented. This method calculates a noise‐to‐signal (N/S) ratio, which indicates the depth of valleys between harmonic peaks in the power spectrum. The spectrum is calculated pitch synchronously from a Fourier transform of the signal, windowed through a continuously variable Hanning window spanning exactly four fundamental periods. A two‐stage procedure is used to determine the exact duration of the four fundamental periods. An initial estimate is obtained using autocorrelation in the time domain. A more precise estimate is obtained in the frequency domain by minimizing the errors between the preliminary calculated power spectrum and the predicted spectrum spread of a windowed harmonic signal. Analysis of synthesized voices showed that the N/S ratio is sensitive to additive noise, jitter, and shimmer, and is insensitive to slow (8 Hz) modulation in fundamental frequency and amplitude. An analysis of pre‐ and postoperative voices of six patients with benign laryngeal disease showed that the N/S ratio for vowel /u/ in running speech consistently improved after surgery for all subjects, in agreement with their successful therapeutic results.

65 citations

Journal ArticleDOI
TL;DR: In this paper, the authors theoretically analyzed the second harmonic generation capacity of two-dimensional periodic metamaterials comprising sub-wavelength resonators strongly coupled to intersubband transitions in quantum wells at mid-infrared frequencies.
Abstract: We theoretically analyze the second harmonic generation capacity of two-dimensional periodic metamaterials comprising sub-wavelength resonators strongly coupled to intersubband transitions in quantum wells (QWs) at mid-infrared frequencies. The metamaterial is designed to support a fundamental resonance at ∼30 THz and an orthogonally polarized resonance at the second harmonic frequency (∼60 THz), while the asymmetric quantum well structure is designed to provide a large second order susceptibility. Upon continuous wave illumination at the fundamental frequency we observe second harmonic signals in both the forward and backward directions, with the forward efficiency being larger. We calculate the overall second harmonic conversion efficiency of the forward wave to be ∼1.3 × 10−2 W/W2—a remarkably large value, given the deep sub-wavelength dimensions of the QW structure (about 1/15th of the free space wavelength of 10 μm). The results shown in this Letter provide a strategy for designing easily fabricated sources across the entire infrared spectrum through proper choice of QW and resonator designs.

65 citations

Journal ArticleDOI
TL;DR: In this paper, a systematic procedure for the derivation of exact expressions for the frequency equation and mode shapes of composite beams undergoing free vibration is presented by using the symbolic computing package reduce.

65 citations

Journal ArticleDOI
TL;DR: A general linear passive termination is considered for a typical field effect power transistor such that the first m odd harmonics, excluding the fundamental frequency, are open circuited with the remaining harmonics short-circuited.
Abstract: A general linear passive termination is considered for a typical field effect power transistor such that the first m odd harmonics, excluding the fundamental frequency, are open circuited with the remaining harmonics short-circuited. Under this termination, with the appropriate resistive termination at the fundamental frequency, it is shown that an optimum maximum efficiency of is universally achieved independent of non-linearities in the transistor. Furthermore, where higher ordered harmonics are terminated in finite reactive impedances, which is the case with any realizable network, it is shown that the same maximum efficiency is obtained with the correct complex termination at the fundamental frequency. A prototype network is then defined including the output capacitance of the transistor and synthesized in a lowpass form which, when terminated in a shunt resonant circuit and load resistor, will provide the correct impedances at the fundamental and all of the harmonics. Remarkably, this optimum network has a simple formula for the element values in the general (2m+1) th degree network and a rigorous proof is presented in the appendix. Copyright © 2003 John Wiley & Sons, Ltd.

65 citations


Network Information
Related Topics (5)
Noise
110.4K papers, 1.3M citations
82% related
Vibration
80K papers, 849.3K citations
79% related
Signal processing
73.4K papers, 983.5K citations
76% related
Filter (signal processing)
81.4K papers, 1M citations
74% related
Wave propagation
55K papers, 1.1M citations
74% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202344
2022101
2021236
2020335
2019421
2018375