Unstable CIR Phase


I’m taking two readings of CIR, one after another, from the same pair of Tx-Rx. The environment is kept static during CIR collections. But if I compare the phase of their first peaks, they’re not even close. The first peak phase seems to be changing. I don’t think this should happen give the environment is static. Is there anything I’m missing? (In the plot, the vertical line marks the first path index output by DW1000, which overlapps in two CIRs).

Thank you!

@decawave @deca_admin Some help here is greatly appreciated!

I exactly had the same issue when analyzing the CIR. Also, if you check the LDE_THRESHOLD reported you’ll see that does not match what Application Notes says (NTM*STD_NOISE). More clarification about this would be appreciated.

Hi @AndresPrietoGonzalez ,

Thanks for your reply. I did more measurements after that — had a pair of Tx and Rx and collect the CIRs from Rx (same as what I was doing above). The environment was perfectly static. For each CIR measurement I find the first peak (by peak detection among the several samples after first path index reported by DW1000) and I take the phase of it. The figure shows first peak phases from 100 CIRs, and it seems to randomly jump between -pi and pi. Some help and clarification from Decawave would be great.

That is a really interest test! Let’s hope we can get some clarification about all this.

Hi jleng,

I also wanted to utilize CIR phase and has been playing with it. I’m using DWM1001-DEV and also found the phase of CIR varies a lot even my ambience is perfectly static. Need for some explanation from Decawave… @decawave @deca_admin

I guess this is due to the lack of clock synchronization between the two devices, resulting in CFO(carrier frequency error) in the received CIR.