Hi Sir,

Please see the below figure.



On left there is a voltage source with impedance(Rsource) 50 Ohm, and on right there is a load RL also with impedance 50 Ohm.
If RS/C/L are added between voltage source and RL, we can calculate the impedance toward RL (the blue arrows in figure) as

• at node 3, L//RL = 25+25i
• at node 2, adding C(-25i) goes to 25 Ohm
• at node 1, adding RS(25) goes to 50 Ohm

and since Rsource is 50 Ohm, impedance is matched at node 1, no signal reflection occurs at this point.

However, if we calculate impedance at the opposite direction (the green arrows in figure)

• at node 2, does the impedance equal to Rsource+RS = 75 Ohm ? And in this case, does that mean impedance is NOT matched at node 2 since impedance toward RL side(25 Ohm) and toward source side(75 Ohm) is not equal ? Is there any signal reflection occurs on node 2 ?
• at node 3, similar to node 2, does impedance is NOT matched at this point ? and is there any signal reflection occurs on this point ?

Also, it is obvious that Vs is 0.5*Vsource, without any signal reflection. But what I need is no signal reflection on load side (RL//L), what would be the best matching in this case ?

Thanks for clarifying the concept of impedance matching !

 

See

 

The impedance at any node is a f() of all z's in circuit interacting with that
node.

Your statement

"at node 3, L//RL = 25+25i" is incorrect`, that implies it is a series R in series with an L
its 50s / (1 + s) in laplace. That's its Z if not connected to any other elements.

The transformation of the "effective" series L is as follows -

http://www.phys.ufl.edu/~majewski/nqr/reference2015/nqr_detection_educational/The Series to Parallel Impedance Transformation.pdf

Tool for matching (several on web, this is just one of them)

http://www.daycounter.com/Calculators/L-Matching-Network-Calculator.phtml


Regards, Dana.

 

Hi Bordodynov

Could you explain more about your simulation ? Do you mean all nodes are matched once one of the node is matched ?

Hi danadak,

I am not asking how to transfer impedance from parallel form to series form.

Thanks you all !

 

Hi Bordodynov

Could you explain more about your simulation ? Do you mean all nodes are matched once one of the node is matched ?

Thanks you all !

I took one and the same circuit three times and measured the resistance in three points of the circuit.
For measurement, I applied 1 amp to alternating current generators to the nodes under test.The magnitude of the voltage obtained is equal to the impedance in the given node of the circuit (Ohm's law).