[Prev][Next][Index][Thread]

Re: Vf,Zo,R,G,L,C.....

Hi Antonio,

	I tried modeling high and low loss lines with the same L and C parameters.
 The frequencies stayed exactly the same.  Only the Q changes.  Perhaps the
L and C parameters in a real system are frequency dependant to some degree.
	I have a model with the magnetically coupled L sections and the
frequencies stay exactly the same in those too.  This would suggest that as
the frequency goes up, either the effective inductance or capacitance also
increases since frequncy seems independant of losses in the models.
Perhaps the capcitance from turn to turn starts to take over or something
strange like that is having an effect at higher frequencies...

	Terry


At 11:08 AM 12/30/98 -0800, you wrote:
>Tesla List wrote:
>
>> A single lossy line model.  The corums like the balanced pair but that does
>> not seem realistic to me...  But perhaps they have a good reason to use the
>> two lines that I don't understand...??
>
>The model is always the same for a TEM line. Only the parameters change.
>
>> BTW - the lumped models give pretty much the same waveforms and results
>> just like I always said :-))  However, with the transmision lines you can
>> see the impulse effects of the coil's 3/2, 5/2, 7/2... wavelengths
>> reflecting back which is sorta neat...  but for most uses, the lumped
>> parameters ar vastly easier to deal with and give perfectly good results.
>
>Some time ago I posted something about some measurements that I made to
>find these higher-order resonances. They were all there, with the
>expected
>voltage distributions along the length of a coil, but all at the -wrong-
>frequencies (significantly lower than what the TEM line predicts).
>I attributed the difference to the fact that a vertical coil is not a
>TEM line, because there is significant magnetic field in the 
>vertical direction. A model of this behavior can be obtained by
>including coupling between successive LRC sections of the usual TEM
>model, but I didn't try to derive one.
>
>Antonio Carlos M. de Queiroz
>
>
References: