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.

Modulation strategies of three phase PWM inverters: Analysis and comparative study

Abstract: Presents a systematic study and analysis of the various modulation strategies for three phase pulse width modulated (PWM) inverters. Analytical expressions are derived to obtain harmonic components of output voltages for duty ratio, sine, triangular and step modulation. A comparative study of the merits and demerits of the various modulation technique is presented. The effects of ratios of carrier and reference frequencies, and the instant of synchronisation are investigated. Use of a particular modulation strategy for a particular application is discussed.

Novel efficiency-Optimal Frequency Modulation for high power density DC/AC converter systems

Abstract: State-of-the-art high power density AC/DC and DC/AC converter systems typically employ Triangular Current Mode (TCM) modulation or conventional PWM. TCM is characterized by a wide variation of switching frequency over the mains period and ensures soft-switching in all operating points, but results in increased conduction and high-frequency losses due to the necessary large current ripple. In contrast, PWM with constant switching frequency features a lower RMS current and thus reduced conduction losses, but cannot achieve soft-switching over the entire mains period and suffers from turn-on losses. In this paper it is investigated if an optimal combination of these two operating modes, i. e. an optimal adjustment of switching frequency and/or current ripple amplitude throughout the mains period, can lead to an increase in conversion efficiency and how such an Optimal Frequency Modulation (OFM) control scheme can be implemented in practice. The presented analysis is based on an ultra compact 2kW, 400V DC/AC converter system designed to overcome the GOOGLE Little Box Challenge.

Frequency Chirp Supported Complex Modulation of Directly Modulated Lasers

Abstract: The frequency chirp of the directly modulated lasers (DML) has long been regarded as the performance barrier preventing the DML from being employed in high-speed optical transmissions. In contrast, we regard the chirp as the combination of intensity modulation (IM) and frequency modulation in this paper. By utilizing coherent detection which provides a wavelength reference by the local oscillator, FM can be converted to phase modulation via time integral. Namely, we realize a 2 dimensional complex modulation (CM) using a single DML. The channel of a complex modulation of directly modulated lasers (CM-DML) is convolutional due to the integral operation. The maximum likelihood sequence estimation can be applied for demodulation. CM-DML offers more than 10-dB system OSNR sensitivity advantages over the conventional IM-DML using coherent detection, which shrinks the sensitivity penalty to 1000-km transmission of the standard single mode fiber. This reach record of the optical PAM reveals the great potentials of the CM-DML to replace the commercialized DP-QPSK products for medium reach applications.

Electromagnetic flowmeter measuring system

Abstract: A measuring system for comparing the relative magnitudes of a first and a second D.C. input signal by symmetrically integrating the first input signal between time period intervals proportional to its magnitude relative to the magnitude of the second input signal so that pulses are generated at a frequency which is a multiple of the integrating cycle. The variable frequency pulses are either counted directly or are converted to a frequency variable train of voltage pulses, each of the pulse cycles of the train of pulses having the corresponding periodicity of the variable input frequency and each voltage pulse having a substantially constant pulse width; the train of pulses are used to modulate a voltage source output signal which, when subsequently averaged, provides an output signal that is proportional to the product of the modulated output signal of the voltage source and the input frequency. A flow measuring apparatus operating on the Faraday principle of electromagnetic induction wherein an indication of fluid flow is provided by ratioing a first D.C. signal, proportionally converted from a flow signal induced in the fluid, with a variable D.C. reference signal to produce a frequency variable train of pulses. Each of the pulses in the pulse train has a constant width, and each of the pulse cycles in the pulse train has a time period that varies inversely proportional to the ratio of the D.C. signals to produce an output signal which provides a measurement at a constant value so that the output signal is proportional to the velocity of flow or it is varied proportional to the density of flow so that the output signal is proportional to mass flow.

Modulation device, demodulation device, modulation method and demodulation method

Abstract: A modulation apparatus is disclosed that enables great improvements in signal transmission rate in a limited frequency band as compared with conventional modulation schemes. Modulation apparatus 100 has first and second frequency-increasing SSB modulators 110 and 120. The modulators 110 and 120 are configured to have respective carrier frequencies with a difference by a frequency corresponding to the reciprocal of the symbol rate (i.e. fundamental frequency of the input symbol). Adder 130 combines a LSB signal obtained from the SSB modulator 120 set for a higher carrier frequency, and a USB signal obtained from the SSB modulator 110 set for a lower carrier frequency to obtain a modulation signal.