Create a Multitone Signal

Follow this procedure to set up a simple 8-tone signal and to perform these related tasks:

  1. Start the software and configure the Closedhardware.

  2. Use the default values or configure the ClosedMultitone Settings as desired.

  1. Click to download and play the waveform.

  2. Configure the analyzer to view the resulting multitone signal.

 

Example Multitone Signal

The following figures show an example of the default settings for a ClosedWideband Arb Waveform Generator with a Frequency of 10 GHz.

  1. Configure the analyzer as follows:

The analyzer display should look similar to the figure below. Notice the IMD range and values.

 

 

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Set the Multitone Corrections  

All instruments must share a common 10 MHz reference in order for the corrections to work properly.

 

  1. Configure the ClosedMultitone Settings as follows:

  1. In the ClosedIMD Suppression Bands pane, press Add.

  2. Set the Start Frequency to –15MHz (use the Tab key to enter data and move to the next cell).

  3. Set the Stop Frequency to 15 MHz.

Notice the ClosedTone Preview panel display of the suppression bands.

  1. Click to download and play the waveform.

A progress window similar to the figure below will appear during the correction process.

Green indicates that the IMD suppression level has been achieved, red indicates that the suppression level has not been achieved. The Amplitude Accuracy field shows the achieved tone flatness.  The flatness correction may be disabled.

Set the input attenuator for the spectrum analyzer to at least 20 dB so the distortion from the spectrum analyzer does not affect the multitone signal.

  1. Click Close after the correction process is complete.

Clicking Abort will leave the last signal generated in the Arb. This signal contains the corrections up to the abort.

 

 

Example Multitone Correction

The figure below shows a corrected multitone signal based on the default configuration for a ClosedWideband Arb Waveform Generator.

  1. Configure the analyzer as follows:

 

The correction algorithm corrects everything that is at Tone Frequency Resolution inside the specified suppression band. The correction algorithm views images as IMDs that are in-band. IMD and images can occur in the same place. The correction algorithm corrects IMD that is related to the baseband signal and cannot correct spurs that come from the PSG even if the spurs are within the suppression band. In fact, the correction may make the spurs worse.

 

Click Closedhere for additional IMD information.

At 1 GHz the non-harmonic (spur) specification is -74 dBc.  Corrected for 17000 tones this becomes -74 + 10*log10 (# of tones), or approximately -31 dBc.

IMD suppression has a similar type of equation for maximum suppression: 90 – 8*log10 (# of tones) dBc.
For example, the best possible suppression for a single tone is 90 dBc; for 10 tones it is 82 dBc; for 100 tones it is 74dBc.

 

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Play Stored Waveforms

Waveforms are stored in the Arb. You can play the stored waveforms directly from the user interface by changing the waveform name.

  1. Configure the software as follows:

  1. Click to download and play the waveform.

  2. Change Waveform Name = MULTITONE

  3. Click to Play the waveform.

This will play the previously stored waveform named MULTITONE from the signal generator memory.

Notice that the signal parameters in the Multitone Settings window no longer match the MULTITONE waveform. Clicking at this point will overwrite the MULTITONE waveform stored in memory.

 

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Set Unequally Spaced Tones

  1. Configure the software as follows:

Be sure to use the largest common denominator for the Tone Frequency Resolution to avoid unnecessary correction time.

 

 

  1. On the Tone Table, change Tone 3 to -1.5 MHz as shown below.

 

 

  1. Click to download and play the waveform. The PSG display should look similar to the figure below.

 

 

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Import and Export a Tone Table

In addition to entering tone table information directly from the user interface, tone tables can be imported as .txt files. They can also be exported to .txt files for later use.

  1. To export a tone table, click ClosedExport in the Tone Table pane.

  2. Save the tone table file as a .txt file as shown below.

 

  1. View the tone table .txt file and notice that the data is space delimited. The columns represent On or Off (1 or 0), frequency (Hz), power (dBm), and phase (degrees).

 

 

  1. Import a tone table file by clicking ClosedImport in the Tone Table pane, then selecting the .txt file that contains your tone table data.

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