help with circuit synthesis

Andrijana Kuhar

Joined Jun 17, 2015
14
Hello

I could really use some opinions on this
I have the rational function of the input impedance of the circuit I need to design (in terms of angular frequency, W), but I am not really sure that it can be designed . I will write the impedance simplified here:
Zin(jW)=((2-3j)/(jW+4-5j))+((2+3j)/(jW+4+5j))

Any thoughts on which elements to use in the corresponding circuit?
best regards,
Andrijana

Veracohr

Joined Jan 3, 2011
763
I don't recall the 'proper' method at the moment, but start by simplifying the formula by combining the two rational sections. Then plot the equation across a frequency range and analyze its characteristics. Consider how the characteristics of the input impedance translate to the circuit's output characteristics. From that you should be able to determine the components and values.

djb

Joined May 17, 2008
31
In theory can be designed. This will lead to resistor and / or coil and or capacitor.
In order to find the sizes of all that we must know the frequency of operation. These values are a function of frequency.

crutschow

Joined Mar 14, 2008
28,526
Seems like this should be in homework.

Andrijana Kuhar

Joined Jun 17, 2015
14
In theory can be designed. This will lead to resistor and / or coil and or capacitor.
In order to find the sizes of all that we must know the frequency of operation. These values are a function of frequency.
thank you for your answers. I need to make a circuit from real elements, so, the capacitor, coil and resistor must not be a function of frequency. any thoughts?

ramancini8

Joined Jul 18, 2012
473
Not sure your transfer function can be implemented as written. How do you get j and jw in the same term?

Veracohr

Joined Jan 3, 2011
763
It can be implemented, I worked it out for myself yesterday. Just simplify the equation. It's a very simple circuit.

WBahn

Joined Mar 31, 2012
26,398
MOD NOTE: This appears to be homework. Moved to Homework Help from General Electronics Chat.

Andrijana Kuhar

Joined Jun 17, 2015
14
It can be implemented, I worked it out for myself yesterday. Just simplify the equation. It's a very simple circuit.

Could you explain in more details and maybe show the simple circuit? thanks!

Andrijana Kuhar

Joined Jun 17, 2015
14
Not sure your transfer function can be implemented as written. How do you get j and jw in the same term?
this is a theoretically obtained impedance. the reason I posted this question is that I am not sure that there is a circuit, too
thanks

Veracohr

Joined Jan 3, 2011
763
Did you simplify the equation and plot it?

My method probably isn't what your teacher had in mind. I vaguely remember some kind of formal approach to circuit synthesis from a function but I'd have to look it up to remember.

WBahn

Joined Mar 31, 2012
26,398
thank you for your answers. I need to make a circuit from real elements, so, the capacitor, coil and resistor must not be a function of frequency. any thoughts?
For "real" components, the values almost always ARE a function of frequency. We often assume that they aren't (i.e., assume that we have "ideal" components) to make the math a lot easier and that assumption is usually good enough.

WBahn

Joined Mar 31, 2012
26,398
Could you explain in more details and maybe show the simple circuit? thanks!
Could you show some effort to at least attempt to solve your own homework?

Andrijana Kuhar

Joined Jun 17, 2015
14
Could you show some effort to at least attempt to solve your own homework?
is this the way you "solve" problems when you don't know how to actually solve them? thanks a bunch

Andrijana Kuhar

Joined Jun 17, 2015
14
Could you show some effort to at least attempt to solve your own homework?
Did you simplify the equation and plot it?

My method probably isn't what your teacher had in mind. I vaguely remember some kind of formal approach to circuit synthesis from a function but I'd have to look it up to remember.
I know where the poles are, I just can't find a circuit to match those poles :/

Andrijana Kuhar

Joined Jun 17, 2015
14
For "real" components, the values almost always ARE a function of frequency. We often assume that they aren't (i.e., assume that we have "ideal" components) to make the math a lot easier and that assumption is usually good enough.
the circuit is supposed to be solved with spice, so , yes, i need "real" components, and not REAL components.

WBahn

Joined Mar 31, 2012
26,398
is this the way you "solve" problems when you don't know how to actually solve them?
1) It's not MY job to solve it -- it's YOUR homework.

2) I'm more than willing to help you walk through the problem, but you want someone to carry you from start to finish.

3) Your little mind games don't play too well around here. We've seen this "prove you can solve it" trick used way too many times.

thanks a bunch
You're welcome.

When you decide you want to show some effort, we can continue. Until then, I'll focus on those that are willing to at least try.

Andrijana Kuhar

Joined Jun 17, 2015
14
1) It's not MY job to solve it -- it's YOUR homework.

2) I'm more than willing to help you walk through the problem, but you want someone to carry you from start to finish.

3) Your little mind games don't play too well around here. We've seen this "prove you can solve it" trick used way too many times.

You're welcome.

When you decide you want to show some effort, we can continue. Until then, I'll focus on those that are willing to at least try.
I thought this was a forum where people actually solve circuit problems, but hey, it's not YOUR job to solve MY problem
thank you so much for the life wisdom that you gave me

WBahn

Joined Mar 31, 2012
26,398
I thought this was a forum where people actually solve circuit problems, but hey, it's not YOUR job to solve MY problem
thank you so much for the life wisdom that you gave me
The sad part is that I believe you really do think that this is a place where it is okay to expect other people to do your homework for you without you making the slightest effot.

If you found out today that the doctor you were considering going to never did any of his own work in medical school but rather found someone else to do it for them, would you still choose to go them?

Maybe that is the way things are done where you're from.