15,490 research outputs found
Efficient Sampling of Band-limited Signals from Sine Wave Crossings
This correspondence presents an efficient method for reconstructing a
band-limited signal in the discrete domain from its crossings with a sine wave.
The method makes it possible to design A/D converters that only deliver the
crossing timings, which are then used to interpolate the input signal at
arbitrary instants. Potentially, it may allow for reductions in power
consumption and complexity in these converters. The reconstruction in the
discrete domain is based on a recently-proposed modification of the Lagrange
interpolator, which is readily implementable with linear complexity and
efficiently, given that it re-uses known schemes for variable fractional-delay
(VFD) filters. As a spin-off, the method allows one to perform spectral
analysis from sine wave crossings with the complexity of the FFT. Finally, the
results in the correspondence are validated in several numerical examples.Comment: To appear in the IEEE Transactions on Signal Processin
Advanced Algorithms for Satellite Communication Signal Processing
Dizertační práce je zaměřena na softwarově definované přijímače určené k úzkopásmové družicové komunikaci. Komunikační kanály družicových spojů zahrnujících komunikaci s hlubokým vesmírem jsou zatíženy vysokými úrovněmi šumu, typicky modelovaného AWGN, a silným Dopplerovým posuvem signálu způsobeným mimořádnou rychlostí pohybu objektu. Dizertační práce představuje možné postupy řešení výpočetně efektivní digitální downkonverze úzkopásmových signálů a systému odhadu kmitočtu nosné úzkopásmových signálů zatížených Dopplerovým posuvem v řádu násobků šířky pásma signálu. Popis navrhovaných algoritmů zahrnuje analytický postup jejich vývoje a tam, kde je to možné, i analytické hodnocení jejich chování. Algoritmy jsou modelovány v prostředí MATLAB Simulink a tyto modely jsou využity pro ověření vlastností simulacemi. Modely byly také využity k experimentálním testům na reálném signálu přijatém z družice PSAT v laboratoři experimentálních družic na ústavu radioelektroniky.The dissertation is focused on software defined receivers intended for narrowband satellite communication. The satellite communication channel including deep space communication suffers from a high level of noise, typically modeled by AWGN, and from a strong Doppler shift of a signal caused by the unprecedented speed of an object in motion. The dissertation shows possible approaches to the issues of computationally efficient digital downconversion of narrowband signals and the carrier frequency estimation of narrowband signals distorted by the Doppler shift in the order of multiples of the signal bandwidth. The description of the proposed algorithms includes an analytical approach of its development and, if possible, the analytical performance assessment. The algorithms are modeled in MATLAB Simulink and the models are used for validating the performance by the simulation. The models were also used for experimental tests on the real signal received from the PSAT satellite at the laboratory of experimental satellites at the department of radio electronics.
Superoscillations with arbitrary polynomial shape
We present a method for constructing superoscillatory functions the
superoscillatory part of which approximates a given polynomial with arbitrarily
small error in a fixed interval. These functions are obtained as the product of
the polynomial with a sufficiently flat, bandlimited envelope function whose
Fourier transform has at least N-1 continuous derivatives and an N-th
derivative of bounded variation, N being the order of the polynomial.
Polynomials of arbitrarily high order can be approximated if the Fourier
transform of the envelope is smooth, i.e. a bump function.Comment: 10 pages, 1 figur
Regulation Theory
This paper reviews the design of regulation loops for power converters. Power
converter control being a vast domain, it does not aim to be exhaustive. The
objective is to give a rapid overview of the main synthesis methods in both
continuous- and discrete-time domains.Comment: 23 pages, contribution to the 2014 CAS - CERN Accelerator School:
Power Converters, Baden, Switzerland, 7-14 May 201
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