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Creating and Downloading Waveforms

This topic describes the requirements and procedure for creating and downloading waveforms for playback on the VXG signal generator.

Waveform File Requirements

The VXG signal generator supports the following waveform file types:

Keysight 16-Bit Binary

Binary waveform files must conform to these requirements:

• Signed 2's complement

• Two-byte integer values

• Big endian or little endian byte order (See Default Binary File Format.)

• Value range of -32768 to 32767

• Interleaved I and Q data

• Minimum of 512 samples per waveform (512 I and 512 Q data points)

  Depending on the sample rate, waveforms less than 512 samples can be played.

• Multiple of eight samples (see How do I make my waveform a multiple of eight samples?)

• The maximum number of samples is dependent on the option configuration of the instrument; refer to the Configuration Guide for your particular instrument

How do I make my waveform a multiple of eight samples?

You can add zeros to the I/Q data until your waveform is exactly a multiple of eight samples, that is, dividing by eight yields an integer value. This method may not be suitable for continuous waveforms; in those cases, you can repeat the waveform up to eight times to achieve the same result.

SCPI Example

Use the MMEMory:DATA command to transfer the contents of the binary waveform file into the signal generator:

Then use the following commands to select the waveform file to play and set the signal’s characteristics:

SOURce:SIGNal:WAVeform:SELect "my_file.wiq"

SOURce:SIGNal:WAVeform:SCLock:RATE <sample rate in frequency>

SOURce:SIGNal:WAVeform:RMS <range 0.1 to 1.0>

SOURce:SIGNal:STATe ON

MATLAB

The MAT file format (version 4, 6, 7, and 7.3) and the HDF5 format are supported. Only arrays in the mat file or the hdf5 file are imported as data, and scalar values are ignored. If there is only one array in the file, it is treated as an array of interleaved I/Q samples (I0, Q0, I1, Q1, …). If there are more than one array, simple case insensitive variable naming rules are applied to identify I, Q, and Marker data in the file.

• If the variable name starts with IQ, it is regarded as an array that holds IQ interleaved data. It can be a complex array or a real array filled with interleaved I and Q data (I0, Q0, I1, Q1, …).

• If the variable name starts with I and the second character is not Q, it is regarded as an I array.

• If the variable name starts with Q, it is regarded as a Q data array.

• If the variable name starts with M, it is regarded as a Marker data array.

• Even when names of variables don’t start with any of I, Q, or M, the first and second arrays are regarded as I and Q data arrays respectively.

• If there are multiple arrays, the lengths of the I, Q and Marker arrays must be the same.
• If the variable name is "XDelta" or "SampleRate", it is regarded as a Sample Rate.
• If both "XDelta" and "SampleRate" exist, "XDelta" is regarded as a Sample Rate.

In the case where IQ data are floating values, if the max abs value of I or Q is less than 1.0, no scaling is applied to the IQ data from the matlab file. If it is more than 1.0, the IQ data is normalized with the max abs value of I or Q. The IQ data is also scaled in the same way for Int32, as well. 

Marker data array in the matlab file is used only when the associated wmk doesn’t exist. For example, if there are myWaveform.mat and myWaveform.wmk in the same folder, myWaveform.wmk is used as marker data even if myWaveform.mat has the marker data array.

MATLAB Examples

Example 1. I and Q are created as a complex array.

dataSize = 2560;

phase = 10 * (2 * pi / dataSize) * (0:(dataSize - 1));

iData = cos(phase);

qData = sin(phase);

theData = iData + 1i * qData;

save('myData.mat', 'theData');

Any variable name is OK because there is only one array in the file.

Example 2. I and Q are created as a real array that has double length.

dataSize = 2560;

phase = 10 * (2 * pi / dataSize) * (0:(dataSize - 1));

iData = cos(phase);

qData = sin(phase);

combined_matrix = [iData; qData];

iqData = transpose(combined_matrix(:));

theData = iqData;

save('myData.mat', 'theData');

Any variable name is OK because there’s only one array in the file.

Example 3. I and Q are two separate arrays. The arrays must be the same size.

data1 = iData;

data2 = qData;

save('mydata.mat', 'data1', 'data2');

The first data and the second data are treated as I and Q respectively.

Example 4. If array names start with either I or Q, the order in the mat file does not matter.

save('mydata.mat', 'qData', 'iData');

The first data and the second data are treated as I and Q respectively.

Example 5. Marker data can be added with two matrix configurations.

Firstly, you can create marker data with 4 x N matrix.

marker4N = int16(zeros(4,dataSize));

marker4N(1,1:1) = 1;  % Marker 1

marker4N(2,1:2) = 1;  % Marker 2

marker4N(3,1:3) = 1;  % Marker 3

marker4N(4,1:4) = 1;  % Marker 4

save('mydata.mat', 'qData', 'iData', 'marker4N');

The Data Type for the marker can be Double, Float, Int32, or Int16. Zero values become zero and non-zero values become 1.

Example 6. Next example uses smaller 1xN size array.

marker1N = int32(zeros(1,dataSize));

marker1N(1) = 15; % Marker 4, 3, 2, 1 = 0b1111 = 15

marker1N(2) = 14; % Marker 4, 3, 2, 1 = 0b1110 = 14

marker1N(3) = 12; % Marker 4, 3, 2, 1 = 0b1100 = 12

marker1N(4) =  8; % Marker 4, 3, 2, 1 = 0b1000 =  8

save('mydata.mat', 'iData', 'qData', 'marker1N');

Example 7. The following is an example of python script that creates a HDF5 file using numpy and h5py modules.

import numpy as np
import h5py
import math

data_size = 2560
phase = 10 * (2 * math.pi / data_size ) * np.arange(0, data_size)
i_data = np.cos(phase)
q_data = np.sin(phase)

marker_data = np.zeros(data_size, dtype=int)
marker_data[0] = 15
marker_data[1] = 14
marker_data[2] = 12
marker_data[3] = 8

with h5py.File("hdf5_data.h5", "w") as hdf:
    hdf.create_dataset('iData', data=i_data)
    hdf.create_dataset('qData', data=q_data)
    hdf.create_dataset('markerData', data=marker_data)

Related Topics

Waveform File (GUI and SCPI description)

Creating Waveform Marker Files