Hello all of you,
Op vr 8 jul. 2022 om 19:58 schreef DP <dpoinsett@...>:
For DC or low frequency AC, the return current path in this circuit is on
the bottom copper plane directly immediately between the two ports and
diffused widely over the rest of the bottom surface. As the signal
frequency is increased, the electrical and magnetic fields begin to
concentrate almost entirely in the small space between the top trace and
the bottom copper plane. At RF frequencies, the return current path on the
bottom plane is directly below the trace and NOT between the ports even if
they are close.
Perhaps this is related: When transporting non-DC currents in a coax, both
the shield and the core need to be transporting the TE mode, and thus the
coax has to be the return path and not the connection between the port-1
and port-2 of the NanoVNA.
RF return current always flows via the path of least reactance. Here's
more info:
Nice article!
Thanks,
Victor
