[SI-LIST] Re: characteric impedance
- From: Long Yang <long.0.yang@xxxxxxxxx>
- To: tonywai34@xxxxxxxxx
- Date: Wed, 5 Dec 2012 01:37:04 +0800
Long time ago, I derived the S2S conversion, shown as below
Sy = { [Zx/Zy * (U-Sx)^-1] + (U+Sx)^-1 }^-1 * { [Zx/Zy * (U-Sx)^-1]
- (U+Sx)^-1 }
where
Zx --- Reference impedance matrix X
Zy --- Reference impedance matrix Y
Sx --- S-parameter matrix with ref impedance Zx
Sy --- S-parameter matrix with ref impedance Zy
For example, there is one transmission line S-parameter derived with
reference impedance 100ohm, but we want to know the corresponding
S-parameter with 85ohm as reference impedance. If this transmission line is
designed with 85ohm as Zc, we will see resonance in 100ohm S-matrix, but no
resonance in 85ohm S-matrix.
thanks
Long
On Wed, Dec 5, 2012 at 1:26 AM, Long Yang <long.0.yang@xxxxxxxxx> wrote:
> Does it work to use the conversion between Z-parameter and S-parameter? I
> doubt...
> S-parameter is a behavioral model. You can not recognize what the
> S-parameter stand for, transmission line, or waveguide, or something
> else////
>
> Here is my thought, point out if something wrong.
> If you are very sure that this S-parameter is for one dimension non-ideal
> (or ideal) TEM-dominant transmission line, in the other words uniform
> transmission line, then this S-parameter is kind of equivalent to
> W-element, the characteristic impedance is ready to solve. And I do think
> S2Z or Z2S conversion can be directly used to estimated Zc, though they can
> be used to do.
>
> By the definition of S-parameter, reflection is zero when the reference
> impedance is matched characteristic impedance, so we can derive the formula
> of S2S conversion, and sweep Zc to see when reflection tends to zero.
>
> thanks
> Long
>
> On Tue, Dec 4, 2012 at 8:23 PM, Zhang Tony <tonywai34@xxxxxxxxx> wrote:
>
>> Hi
>> If I got a s-parameter file, how can I calculate its characteric
>> impedance at some frequency range?
>> is there any tools can help on this?
>> thanks
>> tony
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