ee4101 lectures 3 _ 4 & 5 -- 2010

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

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1 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
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3 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
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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
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7 EE4101 RF Communications Part B – Two port network stability Conditional stability: | Γ in | < 1, | Γ out | < 1 for only certain range of passive load and source impedances To check on stability regions: Input side Set | Γ in | = 1 Then |S 11 (1 – S 22 Γ L ) + S 12 S 21 Γ L | = |1 – S 22 Γ L | We get the input stability circle | Γ L –C L | = R L where 2 2 21 12 22 S S S R L 2 2 * 22 * 11 22 ) ( S S S C L S S S S 21 12 22 11
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8 EE4101 RF Communications Part B – Two port network stability To check on stability regions: Output side Set | Γ out | = 1 Then |S 22 (1 – S 11 Γ S ) + S 12 S 21 Γ S | = |1 – S 22 Γ L | We get the input stability circle | Γ L –C L | = R L where 2 2 * 11 * 22 11 ) ( S S S C S 2 2 21 12 11 S S S R S S S S S 21 12 22 11
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9 EE4101 RF Communications Part B – Two port network stability L L in S S S S 22 21 12 11 1 Where | Γ in |<1? Check at Γ L (or Γ S for output stability) = 0 for for Similarly for output stability region
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10 EE4101 RF Communications Part B – Stability testing Device unconditionally stable, we have the stability circles completely outside (for |S 11 | < 1 and |S 22 | < 1) the Smith Chart k- Δ test – rigorous conditions for unconditional stability
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This note was uploaded on 10/21/2011 for the course EE 4101 taught by Professor Yeotatsoon during the Spring '11 term at National University of Singapore.

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

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