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Gene Fuller wrote:
For future reference, however, just remember: Fields first, then power or energy. That's the way superposition really works. Way back before optical physicists could measure light wave fields, they were dealing with reflectance, transmittance, and irradiance - all involving power or energy. They are still using those concepts today proven valid over the past centuries. Optical physicists calculate the fields *AFTER* measuring the power density and they get correct consistent answers. Use whatever method works for you but don't try to change or replace the body of the laws of physics that was in place before your grandfather was born. Your rejection of those laws of physics from the past centuries is why you are so confused today by your steady-state short cuts. It's why Keith doesn't recognize a 1.0 reflection coefficient when it is staring him in the face. It's why Roy rejects energy in reflected waves. Optical physicists have known for centuries where the energy goes. That RF engineers are incapable of performing an energy analysis is sad. Irradiance (intensity) is a power density. Many problems in physics can be solved without even knowing or caring about the strength of the fields. Here is one such lossless line problem for you. 100w--50 ohm line--+--1/2WL 300 ohm line--50 ohm load Pfor1--|--Pfor2 Pref1--|--Pref2 Without using fields, voltages, or currents: Calculate the magnitudes of the four P terms above. Using the RF power reflection-transmission coefficients, please explain the magnitude of Pref1. If you cannot do that, you really need to broaden your horizons and alleviate your ignorance. Quoting HP AN 95-1: "The previous four equations show that s-parameters are simply related to power gain and mismatch loss, quantities which are often of more interest than the corresponding voltage functions." -- 73, Cecil http://www.w5dxp.com |
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