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Measurements >> RF Measurements >> signal generator output voltage
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Message started by aaron_do on May 2^nd, 2008, 9:08pm

Title: signal generator output voltage
Post by aaron_do on May 2^nd, 2008, 9:08pm

Hi all,

when we run a simulation using a PORT element, and set the output voltage to V, it will actually be a voltage source with a voltage of 2V and a 50 ohm resistor. Therefore, when you match your circuit to the PORT, you will get an input voltage of V.

So does the same happen in measurement for a signal generator? Does it assume a matched load?

thanks,
Aaron

Title: Re: signal generator output voltage
Post by pancho_hideboo on May 2^nd, 2008, 11:35pm

aaron_do wrote on May 2^nd, 2008, 9:08pm:

So does the same happen in measurement for a signal generator? Does it assume a matched load?

It depends on Signal Generator you use. So you should read manual of SG you use.
In SG, voltage is defined as RMS value. While, you can set Peak, Peak-Peak, RMS as voltage value in FG(Function Generator)
So if SG supports Terminating Voltage Value setting, you set Vrms then get Vrms at matched load.
If SG supports Open Voltage Value setting, you set Vrms then get Vrms/2 at matched load.

If your SG doesn't have such mode and SG is for uWave, it must be Terminating Voltage Value setting.

Usually their voltage units are denoted as dBu and dBuEMF.
For example, Agilent E4438C Signal Generator support following SCPI command to change display amplitude unit.

"DISP:ANN:AMPL:UNIT {DBM|DBUV|DBUVEMF|V|VEMF}"

Title: Re: signal generator output voltage
Post by aaron_do on May 3^rd, 2008, 4:44am

thanks.

that was very helpful :)