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: In this article, the effect of spectral amplitude modulation on self-phase modulation is studied and it is shown that the removed frequency components are not only replenished by self phase modulation but can even overshoot their adjacent frequencies in power spectral density.
Abstract: The effect of spectral amplitude modulation on self-phase modulation is studied. To that end we remove a small interval of frequency components from the broad spectrum of a femtosecond laser pulse. We investigate the regeneration of these missing frequency components via self-phase modulation. A water jet serves as a transparent sample. A physical model is given which explains the observation that the removed frequency components are not only replenished by self-phase modulation but can even overshoot their adjacent frequencies in power spectral density. In addition, we suggest possible applications in the field of nonlinear microscopy.
19 citations
Patent•
03 Mar 2008
TL;DR: In this paper, a method and apparatus for frequency modulating a PWM involves 1) generating a high frequency carrier signal much greater in frequency than the PWM signal, 2) modulating the high frequency signal to generate a spread spectrum carrier signal, and 3) retiming a PW signal with this high frequency SS carrier signal so that the binary transitions of the PWP signal are aligned with the frequency varying carrier signal.
Abstract: A method and apparatus for frequency modulating a PWM involves 1) generating a high frequency carrier signal much greater in frequency than the PWM signal; 2) modulating the high frequency signal to generate a spread spectrum carrier signal; and, 3) retiming a PWM signal with this high frequency SS carrier signal so that the binary transitions of the PWM signal are aligned with the frequency varying carrier signal. In another embodiment, a PWM oscillator is driven by a second, FM oscillator having spread spectrum characteristics. In another embodiment a PWM oscillator is driven and modulated by a counter/frequency divider comprised of modules.
19 citations
TL;DR: Improved effifiency of frequency-modulated (FM) transmission of signals through analog channels is accomplished by adaptive adjustment of the modulation index in such a manner that the spectrum of the channel signal more nearly occupies the entire channel more of the time than it would otherwise.
Abstract: Improved effifiency of frequency-modulated (FM) transmission of signals through analog channels, i.e., achievement of a higher bandwidth and/or signal-to-noise ratio (SNR) in the received signal for a given channel bandwidth and channel carrier-to-noise ratio (CNR), is accomplished by adaptive adjustment of the modulation index in such a manner that the spectrum of the channel signal more nearly occupies the entire channel more of the time than it would otherwise. Data is transmitted, along with the signal, to enable the receiver to calculate the modulation index at each instant so that the signal can be properly demodulated. The invention has application to FM transmission of signals representing visual image or other information, such as sound, for which human perception of noise is greatest in areas of low amplitude and/or frequency and reduced in and immediately adjacent to areas of high amplitude and/or frequency.
19 citations
01 Aug 1942
TL;DR: In this article, the shape and duration of the transient in a frequency-modulation system with amplitude limiter and symmetric filter pass band was investigated. But the results were not applicable to the case of amplitude limiting.
Abstract: In a frequency-modulation system, a sudden jump in carrier frequency corresponding to a Heaviside unit signal will result in a transient depending on the receiving-filter bandwidth. If this bandwith exceeds twice the maximum frequency swing, the shape and duration of the transient is shown to be about the same as in an amplitude-modulation system with the same bandwidth; for narrower filters the transient lasts longer. These results are applied to several practical cases. The transient is favorably affected by using an amplitude limiter and by arranging the filter pass band so as to enclose the maximum frequency swing symmetrically.
19 citations
Patent•
21 Jan 1993
TL;DR: In this paper, a pulse width modulation speed control for a d.c. motor is presented, where auxiliary sensing of the motor's operating condition, such as current sensing, automatically shuts down the motor.
Abstract: A pulse width modulation speed control for a d.c. motor (12). A control input (26) corresponding to a motorist setting or a sensed condition is coupled to pulse width modulation circuit (16) that generates a variable duty cycle signal. The signal is used to adjust the speed of the motor. Auxiliary sensing of the motor's operating condition, such as current sensing, automatically shuts down the motor.
19 citations