Creating and Downloading Waveform Files

Waveform Phase Continuity

NOTE If you download I/Q data using a file name that currently resides on the signal generator, it also overwrites the existing marker file setting all bits to zero and the file header setting all parameters to unspecified.

Waveform

A waveform consists of samples. When you select a waveform for playback, the signal generator loads settings from the file header. When the ARB is on, it creates the waveform samples from the data in the marker and I/Q (waveform) files. The file header, while required, does not affect the number of bytes that compose a waveform sample. One sample contains five bytes:

I/Q Data

+

Marker Data

=

1 Waveform Sample

2 bytes I

2 bytes Q

 

1byte (8 bits)

 

5 bytes

(16 bits)

(16 bits)

 

Bits 4–7 reserved—Bits 0–3 set

 

To create a waveform, the signal generator requires a minimum of 60 samples. To help minimize signal imperfections, use an even number of samples (for information on waveform continuity, see “Waveform Phase Continuity” on page 195). When you store waveforms, the signal generator saves changes to the waveform file, marker file, and file header.

Waveform Phase Continuity

Phase Discontinuity, Distortion, and Spectral Regrowth

The most common arbitrary waveform generation use case is to play back a waveform that is finite in length and repeat it continuously. Although often overlooked, a phase discontinuity between the end of a waveform and the beginning of the next repetition can lead to periodic spectral regrowth and distortion.

For example, the sampled sinewave segment in the following figure may have been simulated in software or captured off the air and sampled. It is an accurate sinewave for the time period it occupies, however the waveform does not occupy an entire period of the sinewave or some multiple thereof. Therefore, when repeatedly playing back the waveform by an arbitrary waveform generator, a phase discontinuity is introduced at the transition point between the beginning and the end of the waveform.

Repetitions with abrupt phase changes result in high frequency spectral regrowth. In the case of playing back the sinewave samples, the phase discontinuity produces a noticeable increase in distortion components in addition to the line spectra normally representative of a single sinewave.

Agilent N518xA, E8663B, E44x8C, and E82x7D Signal Generators Programming Guide

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Agilent Technologies N5181A/82A, N5183A Waveform Phase Continuity, Phase Discontinuity, Distortion, and Spectral Regrowth

N5183A, N5183A MXG, E8663B, N5181A/82A specifications

Agilent Technologies is renowned for its innovative solutions in electronic test and measurement equipment. Among its offerings are several signal generators including the N5181A, N5182A, E8663B, and N5183A MXG. These models are distinguished not only by their performance but also by their versatility across various applications in communications, aerospace, and electronics.

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