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Smith Chart Circuit

In an example in Pozar's Microwave Engineering, a conjugate matching circuit for maximum gain is designed using Smith chart. In the shown Smith chart, the matching circuit for input is designed. We locate \$\Gamma_{source}\$ on the Smith chart, convert it to admittance, then move backwards (towards the load) till we reach 1+jb circle. My question is why do we move backwards ? Thanks in advance.

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  • \$\begingroup\$ Can you specify the example no. in pozar.. \$\endgroup\$ – Virange Nov 11 '15 at 9:49
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Consider microwave amplifier basic design,

enter image description here

and compare this with your cicuit,

enter image description here

If you look from the transistor input port towards left then Z0 it will be treated as load side. Then you convert Γsource to admittance and use open circuit stub.

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  • \$\begingroup\$ Good answer. Here's a tip I find useful. In your first diagram, the arrows point towards the load. Move in the direction of the arrow to move towards the load. Move opposite the arrow to move towards the generator. \$\endgroup\$ – curtis Dec 18 '15 at 17:42
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You rotate backwards because you move away from the impedance mismatch. You will rotate until the admittance is 1 and the stub is used to cancel the complex component.

Actually, you move towards source, not load.

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  • \$\begingroup\$ why do you think you move toward the load from \$\Gamma_{source}\$? you specify that the matching circuit is for the input. \$\endgroup\$ – johnnymopo Nov 7 '15 at 6:30

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