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ee4101 lectures 3 _ 4 &amp; 5 -- 2010

# ee4101 lectures 3 _ 4 &amp; 5 -- 2010 - EE4101 RF...

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EE4101 RF Communications Part B Prof TS Yeo

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2 EE4101 RF Communications Part B – Impedance Matching - Revision Matching using Stub – Smith Chart Γin Z Matching network L 1 L 2 Example: Z = 62.5 , Γ in = 0.6/50 o , z = 62.5/50 = 1.25, y = 1/1.25 = 0.8
EE4101 RF Communications Part B – Impedance Matching - Revision Matching using Stub – Smith Chart

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4 EE4101 RF Communications Part B Lecture Three Amplification
5 EE4101 RF Communications Part B – Two-port network stability Z Z Z Z o S o S S Z Z Z Z o L o L L b a source S source 1 1 a a S S S S b b 2 1 22 21 12 11 2 1 b a load L load 2 2 L device device S S a b 22 21 1 2 1 L L device device in S S S S a b 22 21 12 11 1 1 1 S S device device out S S S S a b 11 21 12 22 2 2 1 Forward gain Note the complex (independent and yet interdependent) between the device , source , load ends. See also slides 6 and 15.

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6 EE4101 RF Communications Part B – Two-port network stability Circuit is stable (does not oscillate), if input resistance and output resistance are both positive or | Γ in | < 1 and | Γ out | < 1 Unconditional stability: | Γ in | < 1, | Γ out | < 1, and | Γ S | < 1, | Γ L | < 1 for all load and source impedances 1 1 22 21 12 11 L L in S S S S 1 1 11 21 12 22 S S out S S S S For unilateral device (i.e. S 12 = 0, we then have: |S 11 | < 1 and |S 22 | < 1