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.

Impact of Modulation Schemes on the Power Capability of High-Power Converters with Low Pulse Ratios

Abstract: The design of modulation schemes at low pulse ratios is a known topic. However, most of previous work has focused on optimized pulse patterns, e.g., selective harmonic elimination. For industrial applications, standard carrier modulators are still highly attractive in many cases. Unfortunately, few papers presented insightful studies on carrier modulators at extremely low pulse ratios. This paper covers this gap. At extremely low pulse ratios, several special phenomena of carrier modulators are introduced for the first time. For example, a significant performance variation effect can be observed when carrier modulators are used. Moreover, the thermal unbalance of the hotspot devices in the converter may lead to significant power capability degradation of the converter unit. In this paper, the mechanisms behind this are explored and explained in detail for the first time. A quantitative comparison between different carrier-based modulation schemes is presented. Based on that, several design instruction for modulators at low pulse ratios are summarized at the end.

Stable Optical Frequency-Locked Multicarriers Generation by Double Recirculating Frequency Shifter Loops for Tb/s Communication

Abstract: We propose and experimentally demonstrate a novel scheme to generate optical frequency-locked multicarriers by using double recirculation frequency shifter loops based on different frequency shifting direction single-sideband modulation in I/Q modulators driven by RF clock signals. By changing the phase difference of I and Q RF drive signal, each loop generates long wavelength and short wavelength subcarriers, respectively. The tone-to-noise ratio (TNR) performance with amplified spontaneous emission noise and the effect of polarization state are theoretically analyzed and experimentally investigated for the first time. Experimental results are in good agreement with the theoretical analysis. Using this scheme, we successfully generate 104 frequency-locked subcarriers with TNR larger than 17 dB and carrier spacing at 12.5 GHz covering 10.21 nm from 1545.01 to 1555.22 nm which shows that this scheme has great potential in future Tb/s per channel communications. The feasibility of this scheme is demonstrated by the experimental results.

Integral pulse frequency modulated control systems

Abstract: Summary The paper describes a new class of discrete data control systems in which a portion of the system makes use of pulse frequency modulation. This concept arose as an abstraction from the study of neural communication links in physiological control systems. An integral pulse frequency modulator is defined as one which emits a standard pulse whenever the integral of the input variable reaches a threshold value. The frequency of the output pulse train varies in a linear manner with the input magnitude. Modulators producing pulse trains of one or two signs are introduced and approximate frequency characteristics are obtained; they have discontinuous and discrete features, and depend upon signal amplitude, frequency, and initial phase angle. Feedback control systems making use of single-signed modulators in two parallel feedforward paths are described, and some of the unique stability considerations are studied. Continuous systems that approximate these stable discrete-data systems are constructed, and their transient properties considered.

Pulsewidth modulator phase shift

Abstract: Phase shift for the ramp-comparator pulsewidth modulator (PWM) between a continuous input control signal and the signal frequency component of the output is analyzed. It is shown that transport lag is not implicit to these PWM systems in general but rather depends upon the existence of explicit delays between the time at which a switching decision is made and the time at which that decision is executed.

ELF/VLF wave generation via ionospheric HF heating: Experimental comparison of amplitude modulation, beam painting, and geometric modulation

Abstract: [1] Generation of ELF/VLF radio waves (300 Hz to 10 kHz) is achievable via modulation of natural currents in the lower ionosphere with high-power HF (2–10 MHz) heating Recently, Cohen et al (2008b) put forth an alternative to conventional amplitude HF power modulation, therein referred to as geometric modulation, in which the HF ionospheric heating beam is geometrically steered at the desired ELF/VLF frequency, and found 7–11 dB enhanced amplitudes, and ∼14 dB directional dependence for the thus generated ELF/VLF waves, compared to vertical amplitude modulation In this paper, we quantitatively compare amplitude modulation, geometric modulation, and a previously proposed technique known as beam painting, wherein the HF beam is rapidly moved over a wide area during the on portion of amplitude modulation in order to create a larger heated region in the ionosphere We experimentally analyze both the total generation and the directionality, ie, the suitability of each technique to direct signals along a chosen azimuth Among the three methods, geometric modulation is found to be uniquely well suited for both goals We also conduct experiments to investigate two particular physical effects and their role in generation efficacy: that of heat-cool duty cycle and the oblique angle of the HF heating beam It is found that both duty cycle and the oblique angle of the beam have small but counteracting impacts, consistent with the notion that the primary physical process responsible for generation enhancement in geometric modulation is that of formation of an effective multielement phased array