Class25_27_The_Ground_Conundrum1

Class25_27_The_Ground_Conundrum1 - TheGround C onundrum...

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  1 The Ground Conundrum Assignment: Find and research papers on this subject, be prepared to defend research
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 The Ground Conundrum 2 Grounding Thoughts Ground is only a conveniencefor a voltagemeasurement reference Theground paradox Ground is 0 volts Ground is relative Thereis not an absoluteground Ground can beanywhere Any sources referenced to ground returns power to ground All real sources havea referenceto ground
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 The Ground Conundrum 3 Reduced Ground Definition Thereason for thereduced ground concept is related to themodeling of transmission lines in any spice-likesimulator. We will develop the concept of reduced ground first and subsequently illustrate why it is required. Thereduced ground: Collapses return path circuits to a singlereference node. Signal measurement accuracy of a network is then preserved by incorporating the return path effects as elements added into the signal path. Measurement of ground bounce is hidden. Return path may bepower or ground. We will only concern ourselves with ground for now. ReducePower is a good research and development topic.
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 The Ground Conundrum 4 First Order View - Resistor Model This Simplemodel will besufficient to illustratetheground reduction concept and issues of creating multi-linereduced models I1 -I1 I2 -I2 I1 -I1 Lets simplify a μ -strip to simpleresistors Signal path Return path
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 The Ground Conundrum 5 The lossless return path Calculate voltage at the load as a reference R_source=50 R_tline=2 R_load=50 2V
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 The Ground Conundrum 6 The lossy return path Calculatethe voltage at theload Noticethis is less that the voltage on the previous slidebecausethe return path is considered here. Now lets usethis voltagea reference Thegoal is to createa circuit that produces thesameload voltageand current but only has oneground node. R_source=50 R_tline=2 R_load=50 2V Rg_tline=2
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 The Ground Conundrum 7 The reduced ground circuit Thevinize the ground resistor into the signal path. Both lossy ground circuit and the reduced ground circuit produce 0.9615 volts at the loads. One ground node
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 The Ground Conundrum 8 R_source=50 R_tline=2 R_load=50 2V R_source=50 R_tline=2 R_load=50 2V Rg_tline=2 Rg_tline=2 Add another line! Lets keep with a resistor model and a reduced ground path Spice only allows a single nodefor return path for multi conductor transmission line element. I2 -I2 I1 -I1 I3 -I3 I4 -I4 Tlinemodel: 2 lines plus return in 2 lines plus return out This seems OK so far but consider  – I1, -I2, -I3, and -I4 are combined
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 The Ground Conundrum 9 9 Take a closer look at where the current are and the voltages are developed Z1 Z2 Z1g Z2g Z12g Z12 There’s can be a  voltage drop between  these two nodes Current in  plane It is possible to  collapse both  ground nodes into  one node but that  creates issues
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 The Ground Conundrum 10 Circuit Simulation Ground Rules – Transmission Line Rules 1.
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  • Spring '03
  • YinchaoChen
  • Human mitochondrial DNA haplogroup, Trigraph, Transmission line, Impedance matching, Ground De duce finition, Ground Conundrum

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