Equivalent-Time Sampling Waveform Reconstruction in Labview

This article explains how to implement Equivalent-Time Sampling (ETS) in LabVIEW to reconstruct a waveform from interleaved samples and extract its frequency. The process collects segmented data, reorders the samples into the correct sequence, constructs a waveform, and performs frequency analysis using Tone Measurements.

The input signal must be periodic and include a corresponding trigger signal to ensure consistent alignment between acquisitions.

1. Configure the signal and trigger source.

   • Generate a periodic waveform.
   • Ensure a corresponding trigger signal is available.
   • Check the trigger configuration to ensure consistent timing between acquisitions.

2. Acquire data using a looped acquisition method.

   • Use a For Loop to collect segmented data from the analog input.
   • Enable indexing to build a 1D array of sampled data.

3. Convert the acquired data into a waveform-compatible structure.

   • Use a second For Loop with auto-indexing enabled to pass the data forward.

4. Reorder interleaved samples into the correct sequence.

   • Use Get Waveform Components and Index Array to extract the data.
   • Reorder the sequence using the Build Array function.
   • Example reordering:
     • Initial order: 0, 2, 4, 6, 1, 3, 5, 7
     • Final order: 0, 1, 2, 3, 4, 5, 6, 7

5. Build the waveform.

   • Use the Build Waveform function.
   • Set the sampling interval using the formula:
     dt = 1 / (number of iterations × analog input sample rate)

6. Perform frequency analysis.

   • Use the Tone Measurements function to extract the signal frequency from the reconstructed waveform.

The LabVIEW block diagram implementing this process is shown below: