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1

Series-resonant converter with variable input-to-output voltage conversion ratio

Nießen M., Dörmann H., Dick C. P.

Zeszyty Naukowe Instytutu Pojazdów / Politechnika Warszawska

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2017

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z. 3/112

103--110

EN

Series-resonant converters are well known for their very efficient operation. In case of a fixed input-to-output voltage transfer ratio this converter type is basically a very well suited solution. This paper presents a modified modulation technique to widen the field of applications to variable voltage gains. The fundamental idea is to reduce the excitation of the resonant tank by skipping resonant half-waves at the input. Then, the input is shortened such that the current in the resonant tank is freewheeling through the input and is still transferring energy to the output. Experimental results show that operation is feasible, especially when operation frequency is set in the MHz-range using GaN semiconductors.

DE

Serienresonante Konverter sind bekannt für ihren sehr effizienten Betrieb und bestens geeignet für den Einsatz in Applikationen bei festem Verhältnis zwischen Eingangs- und Ausgangsspannung. Dieser Aufsatz präsentiert eine neuartige Modulationstechnik um den Applikationsbereich zu erweitern, insbesondere im Hinblick auf variable Spannungsübersetzungen. Die grundsätzliche Idee basiert auf dem Auslassen anregender Pulse seitens der Eingangsbrücke. Stattdessen wird in einen Freilauf geschaltet, so dass weniger Spannung an den Resonanzkreis angelegt wird. Experimentelle Ergebnisse zeigen den praktischen Gebrauch dieser Schaltung, insbesondere wenn die Arbeitsfrequenz in den MHz Bereich unter Nutzung von GaN Halbleiterbauelementen gelegt wird.

2

Quasi-analytic multidimensional signals

Hahn S. L., Snopek K. M.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2013

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Vol. 61, nr 4

1017--1024

EN

In a recent paper, the authors have presented the unified theory of n-dimensional (n-D) complex and hypercomplex analytic signals with single-orthant spectra. This paper describes a specific form of these signals called quasi-analytic. A quasi-analytic signal is a product of a n-D low-pass (base-band) real (in general non-separable) signal and a n-D complex or hypercomplex carrier. By a suitable choice of the carrier frequency, the spectrum of a low-pass signal is shifted into a single orthant of the Fourier frequency space with a negligible leakage into other orthants. A measure of this leakage is defined. Properties of quasi-analytic signals are studied. Problems of polar representation of quasi-analytic signals and of its lower rank representation are discussed.

3

A comparison of different modulation techniques performances in an underground multiuser communications scenario

Badescu A.-M.

Annales Universitatis Mariae Curie-Skłodowska. Sectio AI, Informatica

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2012

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Vol. 12, no. 2

73--85

EN

The potential use of typical commercial communication systems with ultra high frequencies for the underground emergency/military situations will be investigated, as commercial systems have already a fully developed market that makes them cheap and reliable. The possible usage of broadband techniques like CDMA in the direct sequence will be studied because most commercial communication systems have already been designed to support multiple users, as the underground propagation has many possible applications. The performances of both modulation techniques are evaluated from the point of view of the quality of the signals, power spectral density and the effect that the propagation medium has on the transmitted signals such that the best modulation technique is determined. The 16QAM and QPSK modulations (two of the most popular modulation techniques in the terrestrial wireless system) are compared in a scenario where a number of underground sources share the same physical channel (and antenna) - the receiver is placed at the ground level so the generated signals must propagate through the dielectric layer in order to reach it. The transmitted power, electric and magnetic fields as well as occupied bandwidth are also calculated.