Team Update 15 - Very important

[eugenebrooks]

Originally Posted by Eldarion

As an aside, I wonder why they used two different datapaths on different antennas? Did the old radios do that, or did the two datapaths use the same antenna?

Only the IFI engineers can say for sure, but if you have a transmitter
and a receiver close enough in frequency that the transmitter causes
the receiver interference problems, you can put them on different
antennas and position the antennas to minimize the coupling between
the transmitter and the receiver.

Given that there is an antenna out of sight in the radio modem case
it is very important that the modem be mounted well clear of any metal
structure on the robot. We mount our antenna on a piece of polycarbonate
a good distance away from metal structure on the robot and have not
had any problems with the radio, but we will be first in the line to upgrade
the radio firmware, and install V15 of the master code, at Portland.

Eugene

[Dave K.]

Originally Posted by Eldarion

T
As an aside, I wonder why they used two different datapaths on different antennas? Did the old radios do that, or did the two datapaths use the same antenna?

The eWave design used an RF module made by Uniden for consumer cordless phones. The transmitter and receiver were duplex coupled onto a single antenna.

In both designs, the transmitters are constantly transmitting even when they are not conveying data. One radio transmits around 902MHz, the other around 928MHz.

To find other examples of full duplex operation on a single antenna, look no further than your nearest cordless or cell phone.


The principal is to provide enough isolation between the receiver and transmitter such that the phase noise from the transmitter at the co-located receiver's input doesn't affect the receiver's sensitivity. By isolating the receiver from the transmitter the impedance from one of the tx/rx ports at that ports desired pass frequency will provide a good match to the antenna's impedance and simultaneously provide a high impedance at the opposing tx/rx port. It can be accomplished with a pair of high pass and low pass filters, or could be done with a pass-notch type filter.

The physical seperation between the internal and external antenna provide little in the way of isolation compared to what filters would accomplish, so I suspect that there are still filters present on at least the transmitters, but maybe they felt it was easier than trying to match the the combined port to a single antenna.

IFI clearly had little time to design these radios, so probably took as little design risk as possible, and thus the dual antenna approach.


Clearly they've spent some additional time over these past few weeks working out some software changes, lets hope it resolves the problems some of the teams were experiencing.

[Dominicano0519]

uggh i cant believe people are still arguing over the ringer over the station wall thing.

in the original rule it said that you may only put it through the chute. then in the update it said you may put it through the chute. Get it? May ONLY changed to MAY

[Duke_of_Hazard]

When I read this I started humming the russian chant from Hunt for Red October....Cheers!

I'm happy that IFI is not like so many other distributors, those that even in the face of massive complaint, don't do near about anything. I would have hated to see a week of regionals go on where they went in thinking it was only a bug related to a few......only to find everyone was having problems, ruining that week of regionals.