gta02-core and external GPS antenna
werner at openmoko.org
Thu May 28 21:53:13 CEST 2009
There's one simplification that looks attractive to make in gta02-core
and that's to remove the external GPS antenna connector. From what I've
heard, this antenna is rarely used in the FreeRunner, and for
stationary use, one could connect an external antenna to the socket for
the internal antenna.
There are the following benefits in removing the external antenna:
- reduced SMT cost by removing about a dozen components, some of them
unique. Due to its shape, The antenna connector may also need
special treatment in SMT, such as glueing.
- fewer components means less risk of getting interferences. This goes
particularly for the external antenna socket when open.
- simplifies the layout of the GPS RF circuit and thus reduces the
risk of us getting something wrong.
- when investigating the SD/MMC vs. GPS problem, Andy found that the
antenna selection circuit is operating with an incorrect voltage.
Apparently, this didn't cause any observable problems, but then
you never know what's really behind the occasional glitch ...
- in case future designs are made based on gta02-core, a smaller GPS
subsystem may allow for a smaller PCB size or give more room to
There are also a few disadvantages:
- if you really need the external GPS antenna along with the internal
one, this will not be a welcome change
- the antenna connector also helps to hold the PCB in place. Without
it, there is only USB on that side of the board to assist the
snap-in mechanism. (Probably doesn't matter all that much, though.)
- removing the connector leaves an empty hole in the case
I think the benefits outweigh the disadvantages, so I'd like to see
the external GPS connector gone.
Any thoughts ?
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