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.

Digital power amplifier and digital/analog converter

Abstract: A digital power amplifier includes a pulse width modulator for converting an input signal into a pulse width modulated signal according to a signal level of the input signal; an output stage, switching thereof being controlled by the pulse width modulated signal generated by the pulse width modulator; a pulse width modulation ratio detector for detecting a pulse width modulation ratio of the pulse width modulated signal generated by the pulse width modulator; and a control unit for disabling the switching operation of the output stage. The control unit disables the switching operation of the output stage when the pulse width modulation ratio detector detects that the pulse width modulation ratio is 50%.

Nonlinear dynamics of a laser diode with optical feedback systems subject to modulation

Abstract: The nonlinear dynamic behavior of a direct frequency-modulated diode laser with strong optical feedback is examined and compared to a laser diode subject to electro-optically modulated, strong optical feedback Direct modulation is achieved by sinusoidal modulation of the diode laser injection current Electro-optic modulation is achieved by applying a sinusoidal voltage to an intracavity phase modulating element The output state (characterized by the output power versus time, the intensity noise spectrum and the optical frequency spectrum) for both types of modulation is dependent on the ratio of the modulation frequency to the external cavity resonant frequency, and the modulation power A number of distinct states are observed: conventional amplitude modulation (with FM spectra); multimode, low-noise amplitude modulation; multimode, high-noise amplitude modulation; periodic limit-cycle operation; quasi-periodicity; chaos; low-frequency fluctuations; and mode-locking There are significant differences between the direct and electro-optic frequency-modulation cases The onset of the dynamic instability is characterized as a noisy period-one oscillation for direct modulation and a low-frequency fluctuation for intracavity electro-optic modulation Phase portraits produced experimentally with the use of a digital phosphor oscilloscope are shown to agree well with those constructed from output power versus time data This represents an experimental method for examining the dynamics phase portraits in real-time

Radar tracking accuracy improvement by means of pulse-to-pulse frequency modulation

Abstract: Angular scintillation tracking noise for simplified radar target models has been analyzed by Delano, Muchmore, Freeman, and others for monofrequency pulse radars. This paper extends their work to the case of pulse-to-pulse frequency-modulated radars and demonstrates that such radars offer a significant reduction in angle tracking error. Tracking improvement is derived as a function of tracking servo bandwidth, scintillation spectrum, and FM (frequency modulation) regimen. A quantity, ΔLfc, is defined as the minimum pulse-to-pulse frequency shift required to achieve maximum tracking improvement, and is derived as a function of target model and radar parameters.

Direct Duty Ratio Pulse Width Modulation Method for Matrix Converters

Abstract: This paper presents a new carrier based pulse-width modulation (PWM) method for matrix converters. By using the concept of average over one switching period, the modulation algorithm and the required equations are derived to synthesize the desired output voltage and to achieve the controlled input power factor. The proposed method uses a continuous carrier and the predetermined duty ratio signals to directly generate the gating signals and, thus, is referred to as "direct duty ratio PWM (DDPWM)". The feasibility and validity of the proposed method were verified by simulation and experiment.