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2 Questions: Transfer Function: AWG

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saintefi

New Member
Well I have 2 questions I need answered, first of all how can I get to obtain transfer function of a circuit, without a network analyzer?
Instruments I have include an oscilloscope, a spectrum analyzer, pulse generator, Arbitrary Waveform Generator, DC Power Supply.

Which leads to my next question, how do I use the AWG ?

MikeMl

Well-Known Member
How many ports (or how many connections) into the device you want to get the transfer function of?

saintefi

New Member
Just one input and one output.

saintefi

New Member
Now am getting confused.

The reason am asking is because I dont know how to.

dknguyen

Well-Known Member
YOu sit down, and do a mathematical circuit analysis. That's how you get the transfer function, not by staring at waveforms.

I suppose you might also be able to do it empirically by using the AWG to input a massive frequency sweep of sinusoids into the circuit with the AWG and record each the output fo the spectrum analyzer for each input sinusoid frequency, and then record all that data and use MATLAB or some other software to find a best-fit transfer function for your data. It would be a massive pain in the ass though and you need really really in-depth knowledge to do it.

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Chippie

Member
YOu sit down, and do a mathematical circuit analysis. THat's how you get the transfer function. Not by staring at waveforms.

Yahhh you beat me to it....

Running before learning to walk........

saintefi,
Can you connect an led, resistor and battery together?

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MikeMl

Well-Known Member
Now am getting confused.

The reason am asking is because I dont know how to.

Does your network look like either of these?

Attachments

• Networks.jpg
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saintefi

New Member
Very funny. I can calculate H(s) myself. Lol. I need to use my equipments to get this done.

saintefi

New Member
YOu sit down, and do a mathematical circuit analysis. That's how you get the transfer function, not by staring at waveforms.

I suppose you might also be able to do it empirically by using the AWG to input a massive frequency sweep of sinusoids into the circuit with the AWG and record each the output fo the spectrum analyzer for each input sinusoid frequency, and then record all that data and use MATLAB or some other software to find a best-fit transfer function for your data. It would be a massive pain in the ass though and you need really really in-depth knowledge to do it.

Thanks dknguyen, this was what someone suggested to me. But is there any other way to do this

saintefi

New Member
MIKEMI. Three wires

saintefi

New Member
Hey Chippie, you dont need to talk down on someone, i have done all these analysis analytically, my supervisor wants me t understand how to work instruments, which is why. so quit talking.

dknguyen

Well-Known Member
Thanks dknguyen, this was what someone suggested to me. But is there any other way to do this

What other way is there? To theoretically work out it out (if you know the circuit), or (if it's a black box) input lots of data and look for a pattern in the output data.

THere's only so much you can do if all you can see is the input and output data and the rest of shielded from you.

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kchriste

New Member
Forum Supporter
Just sweep the desired frequency range with a sine wave and measure the output with a scope at various intervals to get some data to plot on a graph.
You could also maybe use a white noise generator to feed into the filter network and look at the output on the spectrum analyzer.

user_88

Member
I seem to recall one method that used a unit step input, in order to get the blackbox transfer characteristics. Another version was to excite the unknown circuit with a unit pulse .... There was some restriction as to how long the pulse could be with respect to the shortest time constant of the unknown circuit. .... I would have to find a textbook to give more details though.

crutschow

Well-Known Member
Do you need a mathematical transfer function or just a plot of output signal versus frequency and perhaps phase?

Chippie

Member
Hey Chippie, you dont need to talk down on someone, i have done all these analysis analytically, my supervisor wants me t understand how to work instruments, which is why. so quit talking.

Perhaps if you were a little more forthcoming with information in your request instead of just putting down so little you may get a better answer!!

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