90 WM-OM-E Rev I
RIS Sampling Mode -- For Higher Sample Rates
RIS (Random Interleaved Sampling) is an acquisition technique that allows effective sampling rates
higher than the maximum single-shot sampling rate. It is used on repetitive waveforms with a stable
trigger. The maximum effective sampling rate of 50 GS/s can be achieved with RIS by making 100
single-shot acquisitions at 500 MS/s. The bins thus acquired are positioned approximately 20 ps
apart. The process of acquiring these bins and satisfying the time constraint is a random one. The
relative time between ADC sampling instants and the event trigger provides the necessary variation,
measured by the timebase to 5 ps resolution.
The instrument requires multiple triggers to complete an acquisition. The number depends on the
sample rate: the higher the sample rate, the more triggers are required. It then interleaves these
segments (see figure) to provide a waveform covering a time interval that is a multiple of the
maximum single-shot sampling rate. However, the real-time interval over which the instrument
collects the waveform data is much longer, and depends on the trigger rate and the amount of
interleaving required. The oscilloscope is capable of acquiring approximately 40,000 RIS segments
per second.
Note: RIS mode is not available when the scope is operating in Fixed Sample Rate mode.
When the SDA 11000 is operating in 11 GHz mode, RIS mode sampling is not available.
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