Equivalent Time Sampling Oscilloscope vs. Real-Time Oscilloscope
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Introduction
In the past, deciding between an equivalent time sampling oscilloscope and a real-time oscilloscope was a matter of determining your bandwidth requirements; but with today’s high-performance instruments that distinction isn’t as clear. This document will discuss how each type of scope samples the incoming waveform and explain the trigger requirements. A summary detailing the advantages of each scope is provided at the end.
Table of contents
Real-Time Oscilloscope
Real-time oscilloscope as an ADC
Triggering the real-time oscilloscope
Equivalent Time Sampling Oscilloscope
One sample per cycle
Sampling methodology
Triggering the equivalent time sampling scope
Eye Diagram
Creating an eye diagram
Real-time eyes
Advantages of Real-Time Scopes
Advantages of Equivalent Time Sampling Scopes
Related Literature
Real-Time Oscilloscope
Real-time oscilloscope as an ADC
A real-time oscilloscope, sometimes called a “single-shot” scope, captures an entire waveform on each trigger event. Put another way, this means that a large number of data points are captured in one continuous record. To better understand this type of data acquisition, imagine it as an extremely fast analog-to-digital converter (ADC) in which the sample rate determines the sample spacing and the memory depth determines the number of points that will be displayed. In order to capture any waveform, the ADC sampling rate needs to be significantly faster than the frequency of the incoming waveform. This sample rate, which can be as fast as 80 GSa/s, determines the bandwidth which currently extends to 63 GHz.
