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Analyzing Stub Matching with Reflection Coefficients
Richard Clark wrote:
On Fri, 13 Apr 2007 16:37:02 GMT, Walter Maxwell wrote: The voltage reflection coefficient at the input of these two transmission lines is 1.0 at 180°, and the current reflection coefficient at this point is 1.0 at 0°. These are the reflection coefficients that would be found when measuring at any short circuit, no matter whether it is physical or virtual. Consequently, both physical and virtual short or open circuits placed on a transmission line can cause reflections. And here we get to the nut of the matter - causality. It is already established that either the physical short, or physical open, whose absence would render any correlation invalid, dominates the action. The proof follows the quality of the physical open or the physical short. A poor physical open or poor physical short will never be improved by ANY transmission line mechanics. On the other hand, poor transmission line mechanics will never deliver the action of the best physical short or the best physical open. I agree that this is the problem in Walt's otherwise brilliant work. Reflections are only caused by the direct interaction between electromagnetic waves and matter. It is nevertheless valid to say that systems behave as though virtual impedances cause reflections. Virtual reflection coefficients are a clever tool and methodology for systems analysis. But it must be remembered that the propagation of electromagnetic waves is effected only by certain physical properties of matter, as described eloquently by James C. Maxwell and others. Those fundamentals of wave behavior are not different in the steady state than at other times. A VIRTUAL short or open is metaphor, and it is an useful metaphor for describing systems. What I see beyond these examples you have provided are statements (in other discussions) that tend to confer a reality to the VIRTUAL which is obviously a contradiction on the face of it. Other than that, there is absolutely nothing in your published work that is in dispute. I completely agree. I think if we got past this one issue, the newsgroup might actually find itself devoted more to discussions of antennas. 73, Jim AC6XG |
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