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.
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Patent•
26 Oct 2006TL;DR: In this paper, an information processing apparatus includes a main body, a fan which is provided in the main body and is driven by a pulse width modulation signal (PWM signal), and a fan control unit which varies a duty ratio of the PWM signal in accordance with a target rotational speed of the fan.
Abstract: According to one embodiment, an information processing apparatus includes a main body, a fan which is provided in the main body and is driven by a pulse width modulation signal (PWM signal), and a fan control unit which varies a duty ratio of the pulse width modulation signal (PWM signal) and a frequency of the pulse width modulation signal (PWM signal) in accordance with a target rotational speed of the fan.
32 citations
TL;DR: In this article, it was shown that the spectrum of a single-mode semiconductor laser under continuous microwave modulation is locked to a single longitudinal mode for optical modulation depths up to ∼ 80 percent, beyond which the spectrum breaks into multimode oscillation.
Abstract: Experimental observations of the lasing spectrum of a single-mode semiconductor laser under continuous microwave modulation reveal that the lasing spectrum is apparently locked to a single-longitudinal mode for optical modulation depths up to ∼ 80 percent, beyond which the lasing spectrum breaks into multimode oscillation. The width of the envelope of the multimode spectrum increases very rapidly with further increase in modulation depth. These results are satisfactorily explained by a theoretical treatment which gives simple analytic results for the time evolution of the individual longitudinal modes. It also yields considerable insight into spectral dynamics, and enables one to predict the dynamic lasing spectrum of a laser from its CW lasing spectra at various output powers. The results can also be used to predict the amount of spectral envelope broadening under single or pseudo-random pulse modulation.
32 citations
TL;DR: In this article, a taper-coupled GaAs−AlxGa1−xAs laser with a linear electro-optic modulator was demonstrated with a characteristic power P 0 of 10 μW/MHz for 90% intensity modulation.
Abstract: Integration of a taper‐coupled GaAs‐AlxGa1−xAs laser with a linear electro‐optic modulator permits efficient optical frequency modulation of the laser emission. The pulsed room‐temperature threshold current density of the device was 8 kA/cm2. Frequency modulation depth in excess of 15 GHz (corresponding to a wavelength shift of 0.4 A) was obtained with a reverse bias change of 20 V across the modulator. Conversion of frequency modulation into intensity modulation was demonstrated with a characteristic power P0 of 10 μW/MHz for 90% intensity modulation. It is shown that reduction of P0 by an order of magnitude is easily feasible.
32 citations
01 Oct 1992
TL;DR: In this paper, the amplitude and phase modulation properties for pump current modulation of a near travelling-wave semiconductor laser amplifier are examined numerically in the time domain with large signal analysis and in the frequency domain with small signal analysis.
Abstract: The amplitude and phase or frequency modulation properties for pump current modulation of a near travelling-wave semiconductor laser amplifier are examined. The investigations are performed numerically in the time domain with large-signal analysis and in the frequency domain with small-signal analysis. It is shown that the modulation bandwidth is increased by high pump current or high input power and that the small-signal modulation efficiency is increased by low pump current or low input power. The validity of the simulations is supported by experimental results. >
32 citations
Patent•
14 May 2004TL;DR: In this article, a method and apparatus having a digital pulse width modulation generator with integral noise shaping is provided, which includes a random period signal generator, a noise shaping unit, a duty ratio quantizer, and a PWM counter.
Abstract: A method and apparatus having a digital pulse width modulation generator with integral noise shaping is provided. The apparatus for generating a digital pulse width modulation signal includes a random period signal generator, a noise shaping unit, a duty ratio quantizer, and a PWM counter. The random period signal generator generates a random period signal. The noise shaping unit is responsive to at least a digital signal, the random period signal, and a delayed digital signal for generating a corrected signal. The duty ratio quantizer is responsive to the corrected digital signal, the random period signal, and a quantization clock signal, and generates a first duty ratio signal and a second duty ratio signal. The PWM counter is responsive to the first and second duty ratio signals and a quantization clock signal, and generates positive and negative PWM signals, respectively.
32 citations