Module 2b - Module 2b Impedance matching method Impedance...

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1 Module 2b Impedance matching with Smith chart Matching with shunt stubs (shorted and open) Voltage transients (and bounce diagrams) 1 Impedance matching method For a lossless line, Z 0 is real but Z L is arbitrary (could be complex). – 1) Find a position along the line where the real part of Z in becomes equal to Z 0 – 2) Add a “matching” reactance to cancel out the imaginary part of Z in (resistive part does not change and remains equal to Z 0 ). 2 First example using the Smith chart 1) Normalize z L = Z L /Z 0 = 0.22 + j0.5 3 Z L = (11+j25)Ω Z 0 = 50 Ω We want Z in to be equal to Z 0 First example continued…(2) 2) Locate load impedance: z L = 0.22 + j0.50 3) Locate and draw | G | circle. All reflection coefficients and input impedances that you can find on that line are going to lie on that circle. Page 4
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2 First example continued…(3) About 6 from the looks of it: (value of r at the intersection of the l G l circle and the positive G real axis) Page 5 Exercise for home: what is the admittance of the load? By the way, what would be the VSWR on this line? Impedance matching with Smith chart Page 6 On the chart, impedance matching consists of going from z L to the center of the chart where G = 0. 4) Move from z L away from load until you cross the r=1 circle . There, Z in = Z 0 +jX. 5) The amount of rotation needed tells you the length of the line needed between the input and the load (here d = -0.112 l) 0.076 and 0.188 are just read off the outer scale (dist. in l
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This note was uploaded on 09/27/2011 for the course ENGINEERIN 3600 taught by Professor Victor during the Spring '11 term at Carleton CA.

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Module 2b - Module 2b Impedance matching method Impedance...

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