Re: transmission line z

On Thu, 19 Jun 2025 13:30:55 -0000 (UTC), "Don" <g@crcomp.net> wrote:

Leo Baumann wrote:

Leo Baumann:

schrieb john larkin:

ir
__________________ copper
.........................................fr4
__________________ copper
>
air

>
www.leobaumann.de/newsgroups/Stripline_without_Groundplane.pdf
>

>
It is necessary to determine the effective material permittivity of the
geometry.

>
OK. It's easy enough for me to mentally model the stripline as a
complexly constructed capacitor.

With inductance.

>
Open question: Is it possible to view the stripline as unterminated long
wire antenna with a length longer than one or two wavelengths? In this
case the radiation pattern's major lobe constricts to increasingly align
with the antenna axis.
>
Danke,

People don't usually include radiation in calculating transmission
line behavior, even though some geometries probably do radiate. I'd
expect that copper and dielectric losses are a lot worse than
radiation, and we usually ignore them too.

Stripline between ground planes shouldn't radiate, at least into free
space.

Some really fast txlines have serious losses, like later gen PCIe and
such. They need adaptive equalizing.

I was at the microwave show in San Francisco yesterday. A guy from R+S
was demonstrating an ADC chip that digitizes at 64 Gbps and 12 bits.
It connects to an FPGA over *eight* microstrip/CPW lines using the
JESD204 protocol. I was shocked. (The chip is too hot to touch and he
wouldn't tell me the price.)