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.

A New Approach to the Harmonic Analysis of SPWM Waves

Abstract: The Sinusoidal Pulse Width Modulation (SPWM) wave is very important for the design of frequency and voltage adjustable DC to AC inverters. Currently, SPWM waves are usually generated through the pulse width modulation (PWM) pins of a singer-chip microcomputer or digital signal processor (DSP). In order to achieve desired SPWM waves and know them better, it is essential to analyze their harmonic components. In this paper, we introduce a new approach to the harmonic analysis of SPWM waves based on Discrete Fourier Series (DFS) and the area equivalent principle. The developed method is convenient and the results of simulation and experiments are more accurate compared to conventional methods. The advantages of our approach are confirmed by the simulation and experimental results.

Digital Pulse-Frequency/Pulse-Amplitude Modulator for Improving Efficiency of SMPS Operating Under Light Loads

Abstract: In this paper we show a novel digital control method for improving efficiency of SMPS operating at light loads and demonstrate its hardware implementation. In discontinuous conduction mode (DCM) it simultaneously performs a change of switching frequency and peak amplitude of the inductor current in order to achieve better efficiency than conventional pulse-frequency modulator solutions. Supporting analysis, simulations, and experimental results verify advantages of this control method

Optical pulse generation

Abstract: In the world of high speed communications where the use of return-to-zero modulation format is advantageous, there is a need for being able to exert electrical control, in a relatively simple manner, over the duty cycle of the optical pulses being generated without the undesirable effects of chirp, whilst providing good extinction between pulses. The invention proposes an optical pulse generator and methods of generating and shaping optical pulses using an arrangement of cascaded Mach-Zehnder type interferometers. The pulse generator has a signal generator that produces sinusoidal electrical modulation signals for application to the electrical inputs of cascaded Mach-Zehnder type interferometers. The first Mach-Zehnder type interferometer in the series is responsive to the sinusoidal electrical modulation signal being applied, to generate a series of optical pulses having controllable chirp. Each successive Mach-Zehnder interferometer is responsive to the sinusoidal electrical modulation signal being applied, to shape the series of optical pulses that are input to it from the previous Mach-Zehnder type interferometer, and produce an output train of optical pulses having a duty cycle that is dependant on the waveform of the electrical modulation signal being applied to at least one of the Mach-Zehnder type interferometers. The frequency of the sinusoidal electrical modulation signal that is applied to each Mach-Zehnder type interferometer is substantially the same.

Phase locked loop frequency and phase modulators

Abstract: A signal generator is arranged to produce frequency or phase modulation at frequencies which extend from a high value down to zero, i.e. to a d.c. level shift. The output oscillator forms part of a phase locked loop which also includes a variable frequency divider. A modulation signal is applied to the loop, so that high frequency modulation signals directly modify the control signal which determines the frequency of the oscillator, and so that low frequency modulation signals alter the divisor value of the variable frequency divider so as to modify the frequency characteristics of the phase locked loop. Quantization noise is reduced by applying a masking signal to an analogue-to-digital converter which utilizes the low frequency modulation signals to alter the divisor value.

Apparatus for detecting the frequency of an input signal by counting pulses during an input signal cycle

Abstract: An apparatus for detecting frequency of an input signal by counting the pulses of a reference signal of a predetermined frequency within one cycle of the input signal is disclosed. The apparatus includes a first and a second latch for latching the number of pulses of the reference signal for two consecutive periods of the input signal. In response to the reference signal, a comparator is used to compare the output value of the first and the second latch. When they are different, a flip-flop generates an interrupt signal to a microprocessor. The microprocessor reads the updated number of pulses and generates an updated frequency value based on the updated number of pulses and the predetermined frequency of the reference signal.