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Settling Time Testing of Fast DACs

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Kvedaras R., Kvedaras V., Ustinavicius T.
Acta Physica Polonica A
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2011
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vol. 119
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issue 4
521-527
EN
New specialized sampling converter for signal timescale transformation and algorithm of digital signal processing for automated measurement of settling times of fast digital-to-analogue converters is represented. The new sampling device with numerically controlled oscillators allows us realization of different types of the timescale transformation. Usage of ΣΔ analogue-to-digital converter and first-in first-out memory allows us significant simplification of the device. The equations of timescale transformation ratio and sampling step are presented. A method using a brick-wall comb filter in frequency domain to filter measurement signal has been developed. It is shown that such filtering allows us significant reduction of noise of measurement signal. A new method and algorithm using a brick-wall comb filter and averaging of filtered signal has been developed. Results of the research of developed digital signal processing algorithm are submitted.
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Solid State Plasma in the Pulse Modulated Magnetic Field

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Jankauskas Z., Barauskas S., Kvedaras V.
Acta Physica Polonica A
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2009
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vol. 115
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issue 6
1025-1027
EN
Radio frequency (RF) magnetoplasmic waves known as helicons will propagate in solid-state plasma of semiconductors when a strong magnetic field is applied. Helicons have an exact analogy with an electromagnetic whistler wave which is frequently propagated in the low density plasma of the Earth ionosphere. In our experiments the modulated magnetic field is being used for excitation of helicons. It is shown that in the case of pulse modulated field along with the RF helicon waves the transient cyclotron frequency oscillations exist in the semiconductor plasma. For observation of the cyclotron radiation frequency ω_c the modulation depth about one percent is sufficient. The measurement of ω_c provides an opportunity to determine the masses of electrons and holes in solid-state plasma of semiconductors. In already existing method the absorption of electromagnetic radiation on the cyclotron frequency is being used. For this case it is necessary to have an external infrared generator. In our method the cyclotron radiation is being generated by electrons (or holes) directly and additional external excitation is not needed.
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