DOA estimation troubleshooting -- any advice?

1

Hello,

I’m new to SDR, so I apologize if this is a simple issue. I’m looking for some advice on troubleshooting DOA estimation with KrakenSDR. Initially, the DOA estimation graph looks as expected. Using either ULA or UCA, the Max DOA angle is accurate within the estimated resolution. However, after less than a minute, the correct Max DOA angle is lost, and typically, unable to recover. I have tried several signal sources including ones in LOS, but the result is always the same.

Is this a multipath issue? Or possibly a calibration issue? There doesn’t seem to be anything wrong with the USB-C or antenna cables. I’m using a RPi5 with the latest image, and an Ubuntu laptop (12th gen i7 w/ 32GB RAM) for the GUI.

Thank you.

2

How cluttered is your local environment?
Are you SURE you have port 0 connected to the front antenna, and the rest in clockwise order looking down on the car?

3

Yes, port 0 is connected to the front antenna, and the array is oriented in a clockwise manner.

I forgot to mention that we have been doing stationary tests, both indoor and outdoor. Clutter was certainly an issue indoors, but the outdoor testing space is quite open.

The array is on a steel utility cart and takes up most of its top surface. Would extending the ground plane beyond the array possibly help?

We have also been testing with a transmitter about 5-10m in front of Kraken. So far, the issue persists.

4

The cart may be the whole problem. I would not expect predictable patterns in that scenario.

Indoors testing is about hopeless except at very high frequencies. Reflections will come from unanticipated directions and change when anything moves.

What frequencies are you running?

5

Yes, I think you are right about testing indoors and using the cart… We haven’t had any luck.

Most of the testing was performed between 550 and 575 MHz. I plan to try again on Monday with the antenna array attached to a vehicle for comparison.

6

Is the DOA lost with the transmitter just staying still and not moving?

Is there anything else connected to your Pi 5 USB ports?