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Generalized Sampling Principle

IP.com Disclosure Number: IPCOM000046747D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Faris, SM: AUTHOR

Abstract

This article relates generally to pulse sampling techniques and more specifically relates to a sampling technique which uses room temperature devices in a voltage-controlled mode. Fig. 1 illustrates the sequential sampling principle which is used in commercially available sampling oscilloscopes. The prior-art oscilloscopes utilize a voltage-controlled switch such as a diode with an I-V characteristic shown in Fig. 1B. A pulse vp(tÅt) forward biases the diode, causing capacitor C to be charged. During the time of pulse vp(tÅt), the unknown signal vs(t) is sampled and the voltage across capacitor C is proportional to vs(t). As t is varied, the whole waveform is replicated. The time resolution of such a system is given directly by the pulse duration.

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Generalized Sampling Principle

This article relates generally to pulse sampling techniques and more specifically relates to a sampling technique which uses room temperature devices in a voltage-controlled mode. Fig. 1 illustrates the sequential sampling principle which is used in commercially available sampling oscilloscopes. The prior-art oscilloscopes utilize a voltage-controlled switch such as a diode with an I-V characteristic shown in Fig. 1B. A pulse vp(tÅt) forward biases the diode, causing capacitor C to be charged. During the time of pulse vp(tÅt), the unknown signal vs(t) is sampled and the voltage across capacitor C is proportional to vs(t). As t is varied, the whole waveform is replicated. The time resolution of such a system is given directly by the pulse duration. A superconducting sampler such as that described in [*] operates on a different principle altogether. As shown in Fig. 2, such a sampler utilizes a current control switch such as a Josephson junction having an I-V characteristic, as shown in Fig. 2B. It operates using the superposition of Is(t), Ip(tÅt) and IB . These signals are adjusted such that the Josephson switch just reaches its switching threshold. Averaging means, comparator means and feedback means insure that the threshold is unambiguously defined in spite of the presence of random events, such as noise, jitter, etc. A very important distinction between this technique and the conventional technique described above is that the pulse duration alone does not determine the resolution. Resolution in the superconducting sampler is ultimately determined by the switching speed of the Josephson switch...