# Design pi/2 artificial transmission line using lumped elements

1. ## Design pi/2 artificial transmission line using lumped elements

Hi, I was reading the paper "Design Methodology for distributed Power Amplifier in Software -Defined Radio Applications" and came across
"Once the characteristic impedances values are fixed, design can be completed by synthesizing the pi/2 transmission lines using lumped components and embedding the devices". I know how to make a transmission line using lumped elements but how do we do it for particular length of the line? Does it mean we need to design an inductor and capacitor per unit length and distribute them until we have pi/2 electrical length?

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2. ## Re: Design pi/2 artificial transmission line using lumped elements

Originally Posted by circuitslave
I know how to make a transmission line using lumped elements
I don't know how to make a transmission line using lumped elements.

Teach me how to make a transmission line using lumped elements.

Originally Posted by circuitslave
"Once the characteristic impedances values are fixed,
design can be completed by synthesizing the pi/2 transmission lines
using lumped components and embedding the devices"
.
Simply it is a phase shifter of pi/2.

3. ## Re: Design pi/2 artificial transmission line using lumped elements

Originally Posted by pancho_hideboo

Teach me how to make a transmission line using lumped elements.
I don't believe if you say that you don't know something. You are genius. I can make lossless line using lumped elements. Connect Inductor in series and Capacitor in shunt and repeat the combination that gives artifical transmission line.

Originally Posted by pancho_hideboo
Simply it is a phase shifter of pi/2.
I don't understand what do you mean by this

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4. ## Re: Design pi/2 artificial transmission line using lumped elements

Look at ABCD parameters for lumped components and transmission line.

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5. ## Re: Design pi/2 artificial transmission line using lumped elements

Originally Posted by circuitking
I don't believe if you say that you don't know something. You are genius. I can make lossless line using lumped elements. Connect Inductor in series and Capacitor in shunt and repeat the combination that gives artifical transmission line.
What he means is that you can only approximate a particular length of transmission line at a particular frequency by lumped components. Placing a length of transmission line only rotates your impedance on the Smith Chart and introduces a phase delay. And given full freedom in the choice of lumped components, you can match any (passive) load to another (passive) load. For example, one of the most common approximations of a lambda by 4 tline is a pi network but it works 'perfectly' only at one frequency.

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Originally Posted by pancho_hideboo

Simply it is a phase shifter of pi/2.
pi/2 is the electric length I think.. Won't the phase shift be pi?

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Originally Posted by pancho_hideboo

Simply it is a phase shifter of pi/2.
pi/2 is the electric length I think.. Won't the phase shift be pi?

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Ignore the last part of the last message. I was thinking of something else when I typed that. Sorry about it. (somehow I misread pi by lambda)..

A lambda by 4 TLIne introduces a phase shift of pi/2. It also transforms your impedance as Zo^2/ZL where Zo is the characteristic impedance of the line and Zl is the load impedance,

6. ## Re: Design pi/2 artificial transmission line using lumped elements

Originally Posted by circuitking
I know how to make a transmission line using lumped elements but how do we do it for particular length of the line? Does it mean we need to design an inductor and capacitor per unit length and distribute them until we have pi/2 electrical length?
Yes, your delay line from lumped components will have low pass characteristics. The more segments you use, the more it approximates the truely distributed LC of the line, for wider bandwidth.

7. ## Re: Design pi/2 artificial transmission line using lumped elements

Originally Posted by circuitslave
I can make lossless line using lumped elements.
Connect Inductor in series and Capacitor in shunt and repeat the combination that gives artifical transmission line.
It is not a transmission line.

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8. ## Re: Design pi/2 artificial transmission line using lumped elements

A Transmission Line can be represented and modelled by R-L-C-G elements.
http://eceweb1.rutgers.edu/~orfanidi/ewa/

Chapter 11-6 expresses this ..

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9. ## Re: Design pi/2 artificial transmission line using lumped elements

Originally Posted by BigBoss
A Transmission Line can be represented and modelled by R-L-C-G elements.
http://eceweb1.rutgers.edu/~orfanidi/ewa/

Chapter 11-6 expresses this ..
These are not lumped components.