From
Bob, Delta-V
What
is the ¡§Reference Plane¡¨?
The reference plane is simply where a Plug and a Jack
meet when attached together; or in other words, where
the actual RF signals within each connector stop. It
is buried or embedded below the connectors end edge.
The ¡§Reference Plane¡¨ is also known as the ¡§mating
plane¡¨ or ¡§seating plane¡¨ or simply ¡§RP¡¨.
Why is the important? There 2 important reasons.
Mechanical: When these connectors (or adapters) are
attached together, the dimension from a mounting end
or reference center line to the ¡§Reference Plane¡¨
can simply be added together to determine the overall
dimension engaged. As a Male Plug overlaps the Female
Jack when attached, you can not determine when they
¡§mate¡¨ unless you know where the ¡§Reference Plane¡¨
is to stop the engagement. Since the ¡§Reference Plane¡¨
point is buried below the outer end, it can not be seen
from a side view, and therefore must be dimensioned
to a hidden line within the connector (see other attached
vendor drawings for examples). This is critical when
adapters are mated to each other or other mechanical
parts with SMA connectors to determine where the center
lines are.
Electrical: Length is critical at microwave frequencies
to determine overall RF circuit performance. The ¡§Reference
Plane¡¨ is used for just what it¡¦s called, a dimensional
¡§reference point¡¨ to determine RF length where one
connector ends and another starts. These points must
be known to determine the overall length of a RF path
through a series of connectors, cable, etc.
I have also attached a marked up XM datasheet of one
of the connectors we¡¦ve been discussing as a specific
example. Manufacturing should know this dimension from
the engineering drawings to build the connector. Unfortunately
not all vendors include this dimension on typical ¡§customer
drawings¡¨, however, it certain applications (which
includes many I work on) it must be determined to allow
the adapters to interconnect and mate with modules,
adapters and/or other connectors mounted to a PC board.
