[SI-LIST] Re: SMA connector or 2.9mm connector?
- From: <Wolfgang.Maichen@xxxxxxxxxxxx>
- To: <kvhoffmann@xxxxxxxxx>, <scott@xxxxxxxxxxxxx>, <swagguy09@xxxxxxxxx>
- Date: Thu, 14 Jun 2012 07:29:18 +0000
I took "test board" to mean a board used in small quantities for
characterization. That's why I kept mentioning re-use possibilities for the
connectors. If it is indeed an eval board to be given out in rather large
quantities to customers I'd think long and hard about using those expensive
2.92 connectors - either it means a large expense for your employer (to
subsidize the boards or even hand them out for free) or it means fewer
potential customers will order them due to the high price.
Just my 2 cents
Wolfgang
From: kevin hoffmann [mailto:kvhoffmann@xxxxxxxxx]
Sent: Thursday, June 14, 2012 7:13 AM
To: scott@xxxxxxxxxxxxx; swagguy09@xxxxxxxxx; Maichen Wolfgang (IFAG OP BE TTI
THA 2)
Cc: si-list@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] Re: SMA connector or 2.9mm connector?
Hello Ming,
The end launch style connectors that Wolfgang mentions (please correct me if I
am wrong) are basically designed to launch onto the board in a conductor backed
coplanar waveguide configuration. Plain microstrip and other possibilities
exist, but you will need to pay attention to the launch as noted.
Emerson/Johnson has a low cost high perf SMA but it can be difficult to deal
with in terms of attaching to a board depending on version and skill.
Most of these connectors have a 10 mil center pin tab, Southwest Microwave
being the exception in that they offer different center pin size. Something to
consider since putting a 10 mil pin on a small trace is not going to produce a
good launch point. You would need to do some serious modeling, or hire someone
like Scott to work out a launch.
The Rosenberger SMA connector mentioned works well with an appropriate
footprint. I have experience with them on a number of new boards running at up
to 12.5Gbps data rates and edge rates of 18ps. Soldering the center pin is
easily done with a warming plate and hot air pencil.
The Southwest stuff is great, but just too darn expensive to put on an eval
board that gets given away.
Another money area not mentioned is that items like attenuators, terminators,
bias-tees, etc. cost more in 2.92 than in SMA config. Mixing SMA and 2.92 can
result in a reflection which you may or may not have to deal with.
Hope this is helpful.
Kind Regards,
Kevin
--- On Wed, 6/13/12, Wolfgang.Maichen@xxxxxxxxxxxx
<Wolfgang.Maichen@xxxxxxxxxxxx> wrote:
From: Wolfgang.Maichen@xxxxxxxxxxxx <Wolfgang.Maichen@xxxxxxxxxxxx>
Subject: [SI-LIST] Re: SMA connector or 2.9mm connector?
To: scott@xxxxxxxxxxxxx, swagguy09@xxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Date: Wednesday, June 13, 2012, 6:32 AM
Hello Ming,
as Scott said, 2.92mm connectors have much tighter tolerances and offer higher
bandwidth than typical SMA connectors. As usual this comes with some tradeoffs
- they are much more expensive, and at the same time more fragile (dielectric
standoffs, vs. solid dielectric for SMAs); be careful when mating SMA to
2.92mm, while officially compatible you can easily kill the 2.92 connector with
a cheap SMA that has large mechanical tolerances. The real challenge is to get
the specified bandwidth onto the board, and the connector is only one part of
the equation here. Landing pattern, launch area/tapering, ground return each
have huge influence. A sub-optimal design in these areas can quickly negate the
bandwidth advantages of a 2.92mm connector, so you end up with an expensive
board without the benefit of higher performance.
I had good success with 2.92mm connectors from Southwest Microwave (one nice
feature being that they aren't soldered to the board, thus you can easily
re-use them on your next project and save a lot of money that way). They have
reference launch drawings available. For SMA, Rosenberger has some
high-performance models that performed to well over 20 GHz on my boards, and
while not cheap for SMA the cost was still much lower than the SW Microwave
2.92mm ones. On the downside, these are soldered down (center connector only),
but can be re-used with some skill in desoldering (hot air solder station).
Regards,
Wolfgang
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx</mc/compose?to=si-list-bounce@xxxxxxxxxxxxx>
[mailto:si-list-bounce@xxxxxxxxxxxxx</mc/compose?to=si-list-bounce@xxxxxxxxxxxxx>]
On Behalf Of Scott McMorrow
Sent: Wednesday, June 13, 2012 3:15 PM
To: swagguy09@xxxxxxxxx</mc/compose?to=swagguy09@xxxxxxxxx>
Cc: si-list@xxxxxxxxxxxxx</mc/compose?to=si-list@xxxxxxxxxxxxx>
Subject: [SI-LIST] Re: SMA connector or 2.9mm connector?
Ming
It depends on the connector. standard SMA connectors are designed to have
a bandwidth of 18 GHZ. superSMA connectors have a bandwidth in excess of
25 GHZ, some of which up to about 32 GHz. 2.92 mm connectors have a
guaranteed bandwidth of 40 GHz.
Depending on what you are doing, I would generally recommend a 2.92
On Mon, Jun 11, 2012 at 9:05 PM, Ming Li
<swagguy09@xxxxxxxxx</mc/compose?to=swagguy09@xxxxxxxxx>> wrote:
> Hi, experts,
> We are designing test boards for 10Gbps per channel application and we are
> thinking about using either SMA connector or 2.9mm connector on the test
> boards? Can anyone tell us the detailed difference between SMA connector
> and 2.9mm connector?
>
> Thanks a lot.
>
> Regards,
> Ming Li
>
>
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--
Scott McMorrow
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax
http://www.teraspeed.com
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