Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

How to get this transfer function?

Status
Not open for further replies.
R

ruwan2

Member level 5
Joined
Nov 29, 2011
Messages
90
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Activity points
2,141
Hi,
When I read the online tutorial, it gives this transfer function. I wonder where the '2' in the denominator comes from. In elsewhere I see a matched condition would result S21/2, but it doesn't mention a matched condition here.

Can you tell me something about the '2'?




Selection_213.png

Selection_214.png



Best Regards,

Robert
 

Gamma_in is not the transfer function. It actually stands for the reflection at port 1 when port 2 has the reflection coefficient gamma_l. When port 2 is perfectly terminated, gamma_l = 0, then gamma_in = S11 as expected.

- - - Updated - - -

I would think the factor 2 comes from the definition of the transfer function. It is the voltage ratio between load and source. The source impedance will lower down the voltage on the load. When both Gamma_l and Gamma_s equal to 0, S21 = 1, the transfer function = 1/2 as expected.
 

cariban said:
Gamma_in is not the transfer function. It actually stands for the reflection at port 1 when port 2 has the reflection coefficient gamma_l. When port 2 is perfectly terminated, gamma_l = 0, then gamma_in = S11 as expected.

- - - Updated - - -

I would think the factor 2 comes from the definition of the transfer function. It is the voltage ratio between load and source. The source impedance will lower down the voltage on the load. When both Gamma_l and Gamma_s equal to 0, S21 = 1, the transfer function = 1/2 as expected.
Click to expand...

I knew Sin is not a transfer function.
Transfer function was shown in the first attached picture. I upload it again here:
Selection_216.png


It doesn't say S11=0. How do you get S21=1?

Thanks for your reply.
 

ruwan2 said:
I knew Sin is not a transfer function.
Transfer function was shown in the first attached picture. I upload it again here:
View attachment 149610


It doesn't say S11=0. How do you get S21=1?

Thanks for your reply.
Click to expand...

I just assume the simplest case to check if the formula is correct. If you would like to derive the formula yourself, one method is to convert the S-parameter matrix to Z-parameter matrix, then you will get the voltage transfer function.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top