# M8190A relative amplitude arbitrary multi-tones

Question asked by wobbert on Oct 20, 2017
Latest reply on Nov 22, 2017 by thysell

Hi all,

I have some inconvinience witht he M8190A AWG. I am trying to generate a multi-tone output. Therefore I use the Soft Front Panel for the M8190A. When setting the Tone Distribution to "Arbitrary", you could define the tones yourself, including amplitude and phase. I am wondering how the amplitude given in this field relates to the output amplitude. The User Guide states this is the "its relative amplitude (in dB)" (page 61, http://literature.cdn.keysight.com/litweb/pdf/M8190-91030.pdf). However it does not state relative to what. This value seems to be related to the Output amplitude given via the tab "Output" in the Soft Front Panel, but I am not certain how exactly. Could someone help me with this?

Another strange thing I noticed is, when I (in my case) provide only one tone at 20 MHz 0 dB (in this Arbitrary Tone Distrubtion Multi Tone form), the output voltage of the tone at the "Direct output" will be 100 mV (half of the given 200 mV as Amplitude at the output tab -> but that's not that weird because the 200 mV is probably the differential amplitude). However if I change the amplitude of this tone to, for example, -20 dB, the output amplitude stays 100 mV.

When I add another tone (lets say 40 MHz at -10 dB), the 40 MHz tone is 10 dB lower in power than the 20 MHz tone. However if I now also change the amplitude of the 20 MHz tone to -10 dB, both tones will get the same amplitude (luckily) but also get an 100 mV amplitude again.

Could it be that the tone with the highest amplitude always have an amplitude equal to that of the amplitude given at the "Output" tab (even if it is set to +/- x dB) and that all other tones are relative to that tone? So if the second largest tone has an given amplitude of y, the output power/voltage of this tone will be x-y dB lower than the largest tone (where tone x will have an amplitude of, in my case, 100 mV).

Just for convinience:

- AWG: Keysight M8190A

- Scope: Keysight InfiniiVision MSOX3054T

- Driver/Soft Front Panel version: 5.4.5.1

- Windows 7 Enterprise