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Stimulus Amplitude VNA E5062A - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.

 Post subject: Stimulus Amplitude VNA E5062A
Posted: Fri Dec 18, 2009 7:20 am 

Joined: Tue Dec 15, 2009 10:22 am
Posts: 9

I would like to know if it is possible to choose the amplitude of the stimulus signal in an Agilent E5062A Vector Network Analyzer.

I know I can choose the power (at least a range), but how can I know the amplitude of the signal? can I choose it?

Thank you very much.

 Post subject: Re: Stimulus Amplitude VNA E5062A
Posted: Thu Jan 07, 2010 7:20 am 

Joined: Tue Dec 15, 2009 10:22 am
Posts: 9
Can't anybody help me?

Can't I determine the voltage of the stimulus signal?

Thanks again.

 Post subject: Re: Stimulus Amplitude VNA E5062A
Posted: Fri Jan 22, 2010 11:56 pm 
User avatar

Joined: Wed Feb 22, 2006 3:51 pm
Posts: 113
Given the power and the S11 of the device under test, you can calculate the voltage at the input port.

While I don't have the specifications for the E5062A, usually VNA power level adjustability is limited, so you may not be able to reach the voltage you want.

Why is voltage so important, if you know the power?

Good luck!

 Post subject: Re: Stimulus Amplitude VNA E5062A
Posted: Mon Jan 25, 2010 6:31 am 

Joined: Tue Dec 15, 2009 10:22 am
Posts: 9
That's the problem: the power cannot be perfectly determined, but just 15dB-wide power ranges can be chosen.

I want to know Vin because I'm interested in obtaining the voltage transfer function and the output voltage.

 Post subject: Re: Stimulus Amplitude VNA E5062A
Posted: Mon Jan 25, 2010 1:22 pm 
User avatar

Joined: Wed Feb 22, 2006 3:51 pm
Posts: 113
"Voltage transfer function" by itself is not completely meaningful at high frequencies.

One classic definition is Vout/Vin, when driven from a voltage source, and driving into an open circuit. This can often be approximated at low frequencies (audio), but even there, you must be careful not to make your measurements inaccurate.

Both a pure voltage source and an infinite impedance load are, at some point, impossible to obtain and still be useful. For example, an active oscilloscope probe with 0.5 pF input capacitance still has an input impedance in the hundreds of Ohms at 1 GHz.

If you're using a VNA, you have a 50 Ohm source and a 50 Ohm load. You may be able to compute the voltage transfer function mathematically - but I'm not sure which constraints are important to you. The information is "hiding" mostly in S21, but needs compensation for S11 and S22, probably. Our host here at RFCafe has posted a complete set of equations for various conversions to and from S-parameters at

You'll need to identify what you really need, either as a Z-parameter, H-parameter, or Y-parameter.

Good luck!

Posted  11/12/2012
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