**From:** Steve Rogers (*SRogers@micromill.com*)

**Date:** Tue Feb 20 2001 - 04:40:28 PST

**Next message:**Ingraham, Andrew: "RE: [SI-LIST] : SYNTHETIC INDUCTOR USING SHORTED TX LINE"**Previous message:**subramanya C K: "[SI-LIST] : Parallel Termination for a differential signal"**Next in thread:**Ingraham, Andrew: "RE: [SI-LIST] : SYNTHETIC INDUCTOR USING SHORTED TX LINE"**Maybe reply:**Ingraham, Andrew: "RE: [SI-LIST] : SYNTHETIC INDUCTOR USING SHORTED TX LINE"**Reply:**Chuck Hill: "Re: [SI-LIST] : SYNTHETIC INDUCTOR USING SHORTED TX LINE"

I have been looking into the use of shorted transmission line 'stubs' as

synthetic inductors. In particular I hoped that this approach could yield a

high Q factor inductor at VHF.

Shorted stubs made using semi-rigid coaxial line seem to be popular for low

phase noise oscillators at UHF frequencies which suggests a high Q structure

be possible by this method. I had an attempt at producting a synthetic

inductor for VHF using a length of semi-rigid coaxial line shorted at one

end the result was poor to say the least. Details below:-

Line length 0.7 metre

Resonant frequency approx 80 MHz

Q: approx 50

I wonder why the Q is so poor?

My analytical attempts.

My first stab at attempting to justifiy the loss assumes that the cable loss

given by the manufacturer may be used together with the line length and the

driving impedance to calculate the loss due to the inevitable multiple

reflections between the source and the load (Basically use of complex power

flow with masons rules). At first this seemed to be the way to go but then I

thought about the loss value for the line. The loss given by the

manufacturer only applies to a matched line! So what is the loss for a

shorted line???? The V:I ratio will clearly vary along the line length being

min V max I at the short. The loss of the line will thus be a function of

the position of the section of line in question with respect to the short

circuit (at and near the short where currents are max the i squared R losses

must be dominant, at and near the V maximum points the dielectric losses

must be maximum).

Is my thinking taking me off on the wrong path here (is there an easy answer

to this problem?)

IF ANYONE CAN SUGGEST HOW TO SOLVE THIS ONE IT WOULD BE VERY MUCH

APPRECIATED?

Thanks in advance

Steve Rogers

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**Next message:**Ingraham, Andrew: "RE: [SI-LIST] : SYNTHETIC INDUCTOR USING SHORTED TX LINE"**Previous message:**subramanya C K: "[SI-LIST] : Parallel Termination for a differential signal"**Next in thread:**Ingraham, Andrew: "RE: [SI-LIST] : SYNTHETIC INDUCTOR USING SHORTED TX LINE"**Maybe reply:**Ingraham, Andrew: "RE: [SI-LIST] : SYNTHETIC INDUCTOR USING SHORTED TX LINE"**Reply:**Chuck Hill: "Re: [SI-LIST] : SYNTHETIC INDUCTOR USING SHORTED TX LINE"

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