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.

Amplitude modulation detector

Abstract: The amplitude modulation detection device, which is provided with an AM (amplitude modulation) responsive to first and second input signals for maintaining a constant D.C. level output signal, the first signal being the AM signal, and the second signal produced by feedback loop which includes a D.C. voltage comparator connected to the detector for comparing the D.C. output level of the detector with a reference signal level.

Quantum cascade laser linewidth investigations for high resolution photoacoustic spectroscopy

Abstract: High detection selectivity is extremely important for gas analyzers in order to correctly identify the measured compound. Therefore, laser-based systems require a high optical resolution, which primarily depends on the spectral linewidth of the radiation source. This study examines the effective linewidth (chirp) of a pulsed distributed feedback (DFB) quantum cascade laser (QCL) in a photoacoustic (PA) gas detection system. The influence of the QCL operating parameters pulse duration and pulse current as well as the impact of the modulation technique are investigated. Effective QCL linewidths for pulse gate modulation, pulse frequency modulation, and chopper modulation are compared. The investigations are performed by measuring the PA spectra of nitrogen monoxide absorption lines. The results prove the strong influence of pulse duration and pulse current. They also demonstrate that the modulation technique has a considerable influence and, consequently, affects the detection selectivity of the PA analyzer. The aim of this research is to determine optimum operational parameters for high resolution PA spectroscopy.

Analog signal modifying apparatus

Abstract: In an electrolytic paper recorder of electric signals, an analog signal is converted by a voltage controlled oscillator to a series of pulses with rises spaced in inverse proportion to the analog signal amplitude. The spaced rises trigger a pulse generator whose output is a corresponding series of constant amplitude marking pulses with a spatial density proportional to the original signal amplitude. The marking pulses are applied to the blade and helical electrodes of the recorder through a current starved amplifier which adjusts the pulse amplitude to compensate for random variations in the resistance of the electrolytic recording paper between the marking electrodes. The width of the marking pulses may be varied by a variable current source for the pulse generator so as to compensate for the nonlinear gamma characteristic of the paper.

Analysis of Dynamic Range, Linearity, and Noise of a Pulse-Frequency Modulation Pixel

Abstract: A complete pulse-frequency modulation (PFM) pixel design analysis and noise measurement for CMOS image sensor applications are presented. This work investigates the design parameters such as dynamic range (DR), signal linearity, and comparator characteristics. The design strategies for wide DR imaging are addressed in detail, and signal linearity is analyzed by considering the analog circuit parameters. The temporal noise is also measured to understand the design tradeoffs of the PFM pixels. The analysis is executed by performing HSPICE simulation and practical pixel measurements. The technology used by the measured pixel is a 0.18-μm one-poly six-metal CMOS process. According to the results, a PFM pixel using the submicrometer CMOS process has a DR of 130-160 dB, and the cost of reaching a higher signal linearity or lower noise floor is the loss of frame rate. In addition, the bandwidth of the comparator can be extended to improve sensor linearity.

Frequency-modulation electronic ballast for dimmable fluorescent lamp

Abstract: The invention relates to a frequency-modulation electronic ballast for a dimmable fluorescent lamp, which comprises a DC-AC half-bridge inverter circuit. The DC-AC half-bridge inverter circuit consists of two power switching tubes Q1 and Q2 driven by a half-bridge driver, a blocking capacitor C1, a buck inductor T1A and a resonant capacitor C2. Through changing the operating frequency of the half-bridge inverter circuit, the voltage applied across the two ends of the resonant capacitor C2 is adjusted to realize the stepless dimming from 1% to 100% within a wide power range. The electronic ballast does not adopt a special integrated control circuit but a universal microcontroller so as to perform the functions thereof through pulse frequency modulation dimming method. The whole structure of the ballast is simple, and various dimming interfaces can be expanded conveniently to perform digital dimming.