On Wed, 16 Apr 2008 09:31:32 -0500
Cecil Moore wrote:
Roger Sparks wrote:
This WIKI article mentions the ability of an ideal voltage source to absorb power.
It says: "A primary voltage source can supply (or absorb)
energy ..."
That's easy to comprehend for a battery source. Not so
easy for an ideal RF source with a zero series impedance.
Unless we allow it absorb energy with the same ease that it emits energy.
If we define an RF source as a coherent RF battery, anything
is possible (at least in our minds). Which of the following
makes more sense?
1. Destructive interference energy is stored somewhere
in the system and delivered back to the system 90 degrees
later in the cycle just as it is by a physical inductor
or capacitor.
No, the problem here is that the individual switched batteries that would make up this system would not be equally discharged. Some would actually gain charge, and never deliver power to the system. So I don't like this choice.
2. An RF battery inside the ideal source stores the extra energy
in coherent RF form and delivers it back to the system as needed.
This sounds identical to the 1st choice. You can make such a circuit with many individually switched batteries so it becomes a good test of the theory. Again, some of the batteries would actually gain energy.
http://en.wikipedia.org/wiki/Voltage_source
It also says: "The internal resistance of an ideal voltage
source is zero;" So exactly how does something with an
internal resistance of zero absorb any power?
How do we deal with the I x E power when the reflected voltage is greater than the forward voltage from the source? One way is to ignore it and only deal with averages. Another is to allow the ideal voltage source to absorb power. A third way is to allow the energy to be stored in constructive and destructive interference some place in the system. A fourth way is to allow reflections from the ideal voltage source with the result that power will build internally and the phase shift of the resultant system wave will shift farther away from the driving voltage, until some stable power input to disipation rate is reached.
I like your RF battery idea. It could actually be built to a close approximation of an actual sine wave.
--
73, Roger, W7WKB