Topic
Pulse-frequency modulation
About: Pulse-frequency modulation is a research topic. Over the lifetime, 4151 publications have been published within this topic receiving 53039 citations. The topic is also known as: PFM.
Papers published on a yearly basis
Papers
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TL;DR: A new space-vector approach is proposed by which the switching losses can be reduced by 15%-35%, depending on the output load angle, and the output voltage of the proposed scheme turns out to be comparable to the best of the conventional schemes while the input current is more distorted.
Abstract: This paper presents a method for evaluating different modulation schemes employed with three-phase to three-phase matrix converters. The evaluation method addresses three important modulator characteristics: the output waveform quality, the input waveform quality and the switching losses associated with the modulation schemes. The method is used to evaluate four different modulation strategies, all based on the direct space-vector modulation approach. Further, regarding the switching losses, the paper proposes a new space-vector approach by which the switching losses can be reduced by 15%-35%, depending on the output load angle. This new modulation approach is applicable whenever the output voltage reference is below half the input voltage and the output voltage quality is then superior to that of the conventional space vector modulation scheme. The functionality of the new modulation scheme is validated by both simulations and experimental results and compared to waveforms obtained by using exiting space vector modulation schemes. The output voltage of the proposed scheme turns out to be comparable to the best of the conventional schemes while the input current is more distorted.
200 citations
TL;DR: The responses of single units in the cochlear nucleus of the rat to sinusoidally amplitude- and frequency- modulated tones and amplitude-modulated broadband noise were studied and showed a peak in the degree of modulation of the spike frequency within the modulation frequency range from 50 to 200 Hz.
Abstract: The responses of single units in the cochlear nucleus of the rat to sinusoidally amplitude- and frequency-modulated tones and amplitude-modulated broadband noise were studied. The distribution of discharges within a cycle of modulation was determined from cycle histograms locked to the modulation wave. In response to amplitude-modulated tones and broadband noise, all units investigated showed a peak in the degree of modulation of the spike frequency within the modulation frequency range from 50 to 200 Hz. In many units the relationship between the degree of modulation of the stimulus sound and of the modulation of the resulting spike train was almost unchanged over a wide range of sound intensities. In other units, enhancement of modulation within a certain range of modulation frequency became more pronounced when the sound intensity was increased. This was mainly due to a suppression of modulation at lower modulation frequencies. The shape of the histograms was nearly sinusoidal even at modulation depths which resulted in nearly 100% modulation of the neural discharge frequency. The amount of modulation of the discharge frequency in response to frequency-modulated tones was dependent on the frequency of the tone in relation to the CF of the unit.
193 citations
TL;DR: Modulation thresholds were measured for a sinusoidally amplitude-modulated (SAM) broadband noise in the presence of a SAM broadband background noise with a modulation depth of 0.00, 0.25, or 0.50, suggesting that there are channels in the auditory system which are tuned for the detection of modulation frequency, much likethere are channels (critical bands or auditory filters) tuned forThe detection of spectral frequency.
Abstract: Modulation thresholds were measured for a sinusoidally amplitude‐modulated (SAM) broadband noise in the presence of a SAM broadband background noise with a modulation depth (mm) of 0.00, 0.25, or 0.50, where the condition mm=0.00 corresponds to standard (unmasked) modulation detection. The modulation frequency of the masker was 4, 16, or 64 Hz; the modulation frequency of the signal ranged from 2–512 Hz. The greatest amount of modulation masking (masked threshold minus unmasked threshold) typically occurred when the signal frequency was near the masker frequency. The modulation masking patterns (amount of modulation masking versus signal frequency) for the 4‐Hz masker were low pass, whereas the patterns for the 16‐ and 64‐Hz maskers were somewhat bandpass (although not strictly so). In general, the greater the modulation depth of the masker, the greater the amount of modulation masking (although this trend was reversed for the 4‐Hz masker at high signal frequencies). These modulation‐masking data suggest ...
191 citations
TL;DR: It is argued that the present results on frequency selectivity in modulation detection underline the perceptual relevance of a spectral decomposition of a signal’s temporal envelope and provide a rationale for the application of modern concepts like the speech‐envelope spectrum or the modulation‐transfer function in relation to speech intelligibility.
Abstract: For a broadband noise carrier, the modulation detection threshold for sinusoidal amplitude modulation (the test modulation) is measured in the presence of an additional modulation (the masker modulation). Two traditional approaches for revealing effects of frequency selectivity in the audiofrequency domain are shown to give comparable results in the modulation‐frequency domain: (1) a typically peaked modulation‐detection threshold pattern when the masker modulation is a fixed narrow band of noise, and (2) an effect of leveling off of the increase of the modulation‐detection threshold when, for a fixed test‐modulation frequency, the masker‐modulation bandwidth is widened beyond a certain ‘‘critical’’ bandwidth. It is argued that the present results on frequency selectivity in modulation detection underline the perceptual relevance of a spectral decomposition of a signal’s temporal envelope and provide a rationale for the application of modern concepts like the speech‐envelope spectrum or the modulation‐transfer function in relation to speech intelligibility.
188 citations
TL;DR: In this article, a low-power energy harvesting system targeting to harvest several milliwatts from vibration is presented, and several low power design schemes to reduce power dissipation of the proposed system are described.
Abstract: A low-power energy harvesting system targeting to harvest several milliwatts from vibration is presented in this paper. Several low-power design schemes to reduce power dissipation of the proposed system are described, and sources of power loss are analyzed to improve the power efficiency. A discontinuous conduction mode (DCM) flyback converter with the constant on-time modulation is adopted for our system. The DCM operation of a flyback converter is chosen as for maximum power point tracking (MPPT) to be implemented with a single current sensor. The constant on-time modulation lowers the clock frequency of the controller by more than an order of magnitude for our system, which reduces the dynamic power dissipation of the controller. MPPT, executed by a microcontroller unit (MCU), is achieved through dynamic resistive matching, and the MPPT is executed at intermittent time intervals due to a relatively slow change of the operating condition. When MPPT is not active, the MCU operates at a lower clock frequency to save power. Experimental results indicate that the proposed system harvests up to 8.4 mW power under 0.5-g base acceleration with four parallel piezoelectric cantilevers and achieves 72% power efficiency around the resonant frequency of 47 Hz.
186 citations