[Tinyos-help] mica2 vs. telosb range

[Joe Polastre]

If you hook a Mica2 up to a network analyzer, you'll see the device
has a great impedance match on some frequencies (primarily closer to
400MHz), but a much poorer match at higher frequencies.  The problem
is that the CC1000 radio can operate at 315MHz, 433MHz, 868MHz, and
915MHz.  Each of these frequencies has a different set of components
and required board trace widths; the Mica2 uses different components
for different frequencies but *not* a different PCB, which is
affecting the impedance match.

Attached is an S11 graph for the Mica2 at 433MHz, where it is a
relatively good fit.  The green line is the Mica2, the red line is the
XSM (which was sold as the MSP-SYS410CA and is now discontinued).

Since I designed both the Tmote Sky and TelosB, I focused quite a bit
on optimizing the RF performance.  Rob Szewczyk and I took S11
measurements and others on every platform and then optimized our mote
to get the best performance at 2.4GHz.  We continue to only provide
motes with excellent RF performance, and you can see some of our
measurements in the Tmote Sky datasheet at www.moteiv.com/products

-Joe

On 2/4/07, Bruce <bedesign at optonline.net> wrote:
> David,
> An interesting observation is when we use Maxstream 900 MHz modules we get
> twice the distance of the mica2. I'm assuming it's from the antenna
> configuration, possibly the default power was not set to maximum. (I'm going
> to check the default configuration, and verify with the standard install)
> I like the Tinyos platform, there's one other possibility but I don't see
> the hardware available in the US (Eyes I think it is)
> Thanks again, Bruce
>
> >Interesting results.  Hardware wise, there are a few
> >possibilities that I can think of:
>
> >* Antenna type - the telosb inverted-f antenna is a very
> >good antenna.  The whip antenna attached to the mica's are
> >much worse.  The impedance matching on older mica2's is
> >very poor, which will significantly decrease the range.
>
> >* Interference - there's plenty of interference in the 900
> >MHz band, especially with FSK on those CC1000's.  The 2.4
> >GHz CC2420 uses DSSS, which is less likely to be affected
> >by interference.  The 900 MHz cell phone bands surround
> >the 900 MHz band, and spurs coming from the cell phone
> >bands have been known to affect the link performance.
> > Also, any other 900 MHz device will negatively affect
> >performance.  The solution is to add SAW filters to the
> >antenna network, but that's pretty much a no go with
> >off-the-shelf hardware.
>
> >If you're consistently finding that the 2.4 GHz spectrum
> >performs much better in your environment, then go for it.
> > The tmote is a very solid, robust platform to develop on.
>
> >-David
>
>
>
> On Sat, 03 Feb 2007 23:00:20 -0500
>   Bruce <bedesign at optonline.net> wrote:
> > Hi
> >
> > Can anyone tell if they have had similar results.
> >Indoors using the inverted
> >
> >F pcb antenna on telosb (2.4 GHz) we get approximately
> >300 feet between
> >
> > motes and using the 900 MHz motes with the default
> >configuration we get
> >
> > about 150 feet range.
> >
> >
> >
> > Thanks,
> >
> > Bruce
> >
> >
> >
>
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