[SI-LIST] Re: -3dB at S21 graph

20log(Vout/Vin)= 10log(Pout/Pin) = -3dB

This is like a grade 10 electronics problem for when I went to school. Now
it seems to be a 2nd year engineering problem.

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Jian X. Zheng
Sent: Wednesday, January 25, 2006 6:35 PM
To: sitaskina@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: -3dB at S21 graph


Hi, Ma:

No, I think it is different. |S11| = - 3 dB means |S11| is about 0.707 or
|S11*S11| = 0.5 or 50% of the power is reflected. If there is little
metallic, dielectric and radiation losses (normally the case unless for
antennas), the |S21| should be 0.707 or |S21*S21| = 0.5 or 50% of the power
is transmitted.

Regards.

----------------------------------------------------------------------------
Jian X. Zheng, Ph.D., Zeland Software, Inc.
48834 Kato Road, 103A, Fremont, CA 94538, U.S.A.
Tel: 510-623-7162, Fax: 510-623-7135
----------------------------------------------------------------------------

> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of ma mu
> Sent: Wednesday, January 25, 2006 2:17 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] -3dB at S21 graph
>
> Hi all,
>
>   In my insertion loss, S21 graph, I got -3dB loss at 1.5 Ghz. My question
> is :
>    transmission  at 1.5 Ghz  is 50% or  70%  ?  I thnik 50% . please give
> me feedback.
>
>   Ma
>
>
>
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