Strange PDOA measurement

Hi,

We have a strange PDOA measurement on a custom made board. On the board two DW1000 are mounted, and supplied with the same 38.4 MHz crystal, also the synchronization works. The two antenna’s are mounted 22mm and the antenna used is AH086M555003. We are using BAND 2.

strange_pdoa

In the plot above, you can see the real AOA vs the measured PDOA, what strange is on this graph is the part around 0° real AOA. I expected the curve to be monotonically dropping. For a particular PDOA there are multiple AOA solutions?

Any idea what is happening here?

Robin

Antennas are not the ideal receiving element we sometimes assume they are. The response of the antenna can vary depending on the direction of the incoming signal,sometimes by quite a bit. The ceramic style antennas, like this Taiyo Yuden, are particularly non ideal and aren’t suitable for use in PDoA applications in our opinion due to excessive group delay and fidelity factor variances. I’ll note that Decawave’s PDoA demo board uses PCB antennas and not ceramic.

Unfortunately, I don’t have any simple fix for you. You are likely looking at a board redesign with a more suitable antenna to fix this. Making good performing UWB antennas isn’t a trivial exercise and requires considering additional factors that most radio systems can ignore.

As a general rule, we don’t use a ceramic antenna in any of our UWB designs. They simply don’t perform as well as a properly designed PCB antenna.

Mike Ciholas, President, Ciholas, Inc
3700 Bell Road, Newburgh, IN 47630 USA
[email protected]
+1 812 962 9408