RC Phase physical meaning and analysis

[mataruzz]

Hi,
I collected some measurements in LOS at different distances (e.g 2m, 5m, 10m…). I recorded also the RC Phase accessing its specific register location (RX_TTCKO – Receiver Time Tracking Offset, see attached screenshot):

For every measurement setup (e.g. 2m, 5m, 10m) I collected around 400 samples and, for each setup, I noticed that the RC PHASE is between 0 and 127.
Now I have 2 questions:

1. The DW1000 user manual, page 100, reports that the phase is stored in a 7 bits register and 127 (decimal representation) exactly correspond to 1111111 (binary, 7bits). Does it mean that the minimum rc phase value is equal to 360[°]/127 = 2.8346 [°]?
   This idea comes from the fact that in the highlighted area of the screenshot reported above, it’s reported that 7bits = 360 degrees.

2. What about the physical meaning of the RC Phase? Should it be constant if we take measurements with the 2 boards that do not move over time? If not, can you gently explain why?

Thank you,
mataruzz

[AndyA]

Yes, each count in that register represents 2.8 degrees.

This is the phase of the received signal as measured on the receivers clock. Since the transmitter is running on an independent clock to the receiver its value is fairly meaningless. For it to be constant you would need to lock the receiver and transmitter clocks together.
If however you have two receivers running on the same clock with their antennas a known distance apart then the difference in the phase values from each of them can be used to calculate angle of arrival.