Wyniki wyszukiwania - BazTech

1

Fluktuacje fazowe sygnału zegarowego wytworzonego w procesie cyfrowej syntezy częstotliwości

Frankowski R., Kowalski M., Zieliński M.

Przegląd Elektrotechniczny

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2011

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R. 87, nr 9a

95-100

PL

W referacie przedstawiono wyniki pomiarów fluktuacji fazowych sygnału zegarowego wytworzonego w procesie cyfrowej syntezy częstotliwości. Wykorzystano do tego celu dedykowane bloki DCM wbudowane w strukturze układu programowalnego FPGA Virtex4 XC4VFX12. Przeprowadzono badania mające na celu wybranie odpowiedniego trybu pracy tych bloków, aby uzyskać referencyjny sygnał zegarowy charakteryzujący się najmniejszym błędem losowym.

EN

The article presents, the results of the phase fluctuation measurements of the clock signal generated in the digital frequency synthesis process. For this purpose, dedicated DCM blocks embedded in the field programmable gate array Virtex4 XC4VFX12 structure are used. Measurements allowed to choose the appropriate mode of operation of these units to get the reference clock signal characterized by the smallest random error.

2

Accumulated jitter measurement of standard clock oscillators

Zieliński M., Kowalski M., Frankowski R., Chaberski D., Grzelak S., Wydźgowski L.

Metrology and Measurement Systems

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2009

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Vol. 16, nr 2

259-266

EN

Long term instability of frequency and phase fluctuations of the clock signal are significant source of the measurement error in the precise time-interval measurement systems. In this paper the problem of clock signal instability, fluctuations caused by accumulated clock jitter and their influence on the precision of the time-interval measurement system implemented in the programmable CMOS FPGA devices are discussed. The presented method enables jitter characterization of the reference-clock. Moreover, the time-interval-error in the range up to several miliseconds can be easily and quickly calculated using only two parameters obtained during the calibration process. The described method can be applied in measurement instruments with a precise time-base.

3

Influence of the clock signal phase fluctuation on the precision of time-interval measurement

Zieliński M., Kowalski M., Grzelak S., Chaberski D., Frankowski R.

Elektronika : konstrukcje, technologie, zastosowania

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2006

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Vol. 47, nr 1

50-52

EN

Random clock signal phase fluctuations and their influence on the precision of time-interval measurement are described in this paper. The construction of time-interval measurement system [TIMS] and its application for oscillator phase fluctuations measurement are discussed. The new metrological parameters useful for estimations of the precision of TIMS as function of the measuring range are proposed.

PL

W artykule opisano w jaki sposób przypadkowe fluktuacje sygnału zegarowego wpływają na dokładność pomiaru odcinka czasowego. Przedstawiono budowę systemu pomiaru odcinka czasowego oraz pokazano sposób jego wykorzystania do oceny fluktuacji fazowych generatora zegarowego. Zaproponowano nowe parametry dla określenia stopnia oddziaływania fluktuacji fazowych na system pomiaru odcinka czasowego i ich wpływ na dokładność pomiaru w zależności od wielkości zakresu pomiarowego.

4

Impact of tec fluctuations in the Antarctic ionosphere on GPS positioning

Krankowski A., Shagimuratov I. I.

Artificial Satellites : Journal of Planetary Geodesy

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2006

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Vol. 41, No. 1

43--56

EN

With increasing reliance on space-based platforms for global navigation and communication, concerns about the impact of ionospheric scintillation and total electron content fluctuations on these systems have became a high priority. In this paper, GPS transionospheric signals have been used to study the development of ionospheric phase fluctuations observed at Antarctic IGS permanent stations: McMurdo-MCM4, Casey-CAS1, Mawson-MAW1, Sanae-VESL, Syowa-SYOG and Davis-DAV1 in 2001. The use of the multi-station, multi-path observations of the GPS beacons has allowed the study of the time development of irregularities as a function of latitude and longitude of individual geomagnetic storms. The basic storms studied were those of March 19-20, March 31, April 9-11, June 16-17, and September 23, 2001. The rate of TEC (ROT) parameter was used to study the occurrence of TEC fluctuations. The results from studying these storms showed the unique nature of each storm. For the above five storms, data were available from three auroral stations (VESL, SYOG and MAW1) and from 61° to 70° Corrected Geomagnetic Latitude (CGL). In addition, data from three higher latitude polar stations (DAV1, MCM4 and CAS1) near 800 CGL are also analysed. Fluctuation effects, causing dramatic changes in total electron content – TEC, can have a different impact on GPS positioning accuracy (especially during phase ambiguity resolution). Bernese ver.4.2 software was used for the analysis of the GPS permanent data from Antarctic IGS stations. The analyses rely on studying the repeatability of vector co-ordinates. These vectors were investigated during the geomagnetic storms when the intensity of TEC fluctuations was more pronounced. The impact of TEC fluctuations in the high latitude ionosphere on GPS positioning accuracy has been discussed in terms of the total number of observations of doubledifferences (DD) and in the ratio of the total number of all ambiguities to unresolved ones.