Topic
Fundamental frequency
About: Fundamental frequency is a research topic. Over the lifetime, 8941 publications have been published within this topic receiving 131583 citations.
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Patent•
25 Sep 1978
TL;DR: In this paper, a system for generating output pulses in successive periods of time, each including sub-intervals during which the output pulses may be varied in accordance with a pre-determined scheme.
Abstract: This system generates output pulses in successive periods of time, each including sub-intervals during which the output pulses may be varied in accordance with a pre-determined scheme The time periods and sub-intervals within the periods are defined by means of signals derived from a fundamental clock frequency generation circuit and first and second parallel sets of frequency division circuits connected to the fundamental frequency generation circuit The first set of frequency division circuits is used together with a sub-interval timing circuit to define the sub-intervals of time included in each period A system control means is connected to the frequency generation and division circuits, the timing circuits, a means for entering information into the system defining the periods and sub-intervals and the characteristics of output waveforms to be produced in each sub-interval, and to a variable electrical signal generation means which produce the output waveforms in accordance with the information entered into the system Since the time periods, sub-intervals and output waveforms are all variable in accordance either with a pre-determined scheme, or on a real time basis depending on response of a subject under test, this system may be used to generate complex strings of waveforms especially suitable for measuring responses of biological samples to stimulation by electrical signals in pharmacological, physiological and other biomedical applications
36 citations
TL;DR: It is shown that a 50% duty cycle produces the lowest uncertainty in the charge determination, due to the absence of even-numbered harmonics in the FFT, which in turn leads to an increase in the magnitude of the peak at the fundamental frequency.
36 citations
TL;DR: In this article, a CMOS terahertz oscillator with a novel frequency selective negative resistance (FSNR) tank was demonstrated to operate at a fundamental frequency of about 0.22 GHz, exceeding the CMOS device cutoff frequency of fT.
Abstract: This paper reports a CMOS terahertz oscillator with a novel frequency selective negative resistance (FSNR) tank to boost its operating frequency. The demonstrated oscillator can operate at a fundamental frequency of about 0.22 THz, exceeding the CMOS device cutoff frequency of fT. The proposed architecture suppresses undesired 2nd and odd harmonics and boosts the fourth-order harmonic (0.87 THz), which radiates through an on-chip patch antenna. The THz oscillator's output spectrum is profiled by using a Michelson interferometer. The oscillator circuit consumes 12 mA from a 1.4 V supply and occupies a 0.045 mm2 die area in a 65 nm CMOS technology.
36 citations
TL;DR: In this article, a three-phase multilevel active shunt filter with a low switching frequency is proposed to mitigate the lowest order carrier-frequency terms, which is particularly critical when low carrier-fundamental frequency ratios are used such as in aerospace applications.
Abstract: Active power filters create sideband harmonics over a wide frequency range around the multiple carrier-frequency harmonics, and these can encroach into the low frequency range. This issue is particularly critical when low carrier-fundamental frequency ratios are used such as in aerospace applications, where high fundamental frequencies exist. A three-phase multilevel active shunt filter with a low switching frequency is proposed to mitigate the lowest order carrier-frequency terms. However, low carrier frequencies lead to reference voltage phase delay and attenuation and can introduce significant baseband harmonics. These effects cannot be hidden by employing multiple modulator converters. In addressing these problems, an improved modulation approach is proposed in this work that allows duty cycle updating (N - 1) times per switching period for each H-bridge of one phase of the N -level converter [rather than only once or twice as in the regularly sampled pulse width modulation (PWM)]. The proposed modulation approach is then combined with predictive current control in order to enhance the system performance. The control loop performance compared to regularly sampled PWM is verified through simulations and experimentally by employing a three-phase five-level active shunt power filters in a 400-Hz power network.
36 citations
TL;DR: In this article, the forced and free vibrations of a laminated curved beam under moving loads are analyzed, and a detailed parametric analysis is performed to clarify the influence of various parameters such as stacking sequence and load speed on the vibrational behavior of the system.
36 citations