# QM33120WDK1 parameters to calculate AOA from PDOA when channel 5 is used

With QM33120WDK1 evaluation kit, I can read the PDOA values. But I’m wondering what are the proper parameters (especially the distance between the two antennas on QM33120W) to use to calculate AOA (theta) from PDOA (alpha).
The formula is theta = arcsin(alpha * lambda)/(2 * pi * d)
Lambda is the wavelength. It is 0.046m for channel 5 and 0.038m for channel 9. What is the correct value of d to use here? I found somewhere online that it is around 0.02m. But if I use this value for channel 5, I can get 10 to 15 degrees error when the actual AOA is larger than 10 degrees. When I change to channel 9, and use d=0.0178m, then the calculated AOA seems correct.
Could someone please explain a bit how AOA should be calculated in channel 5?
Thanks!

Hi @BC0023 ,

QM33120WDK1 has a Channel 9 optimized AoA antenna with approximately 0.45 lambda antenna spacing at Channel 9. We use a LUT to convert raw PDoA to AoA and it is optimized for only that antenna on Channel 9 and the antenna in the evaluation kit. Therefore, if you try to use the same antenna on Channel 5, you will have inaccuracies in AoA readings.

Is there any particular reason that you want to measure AoA on Channel 5 instead of Channel 9?

Kind regards,
Emre

Hi @Emre_Ozbas_Qorvo
Thanks for the explanation! I don’t have to use Channel 5. I was just doing tests and used Channel 5 as default.
I will use Channel 9 instead for future tests.

Got it! You can still use Channel 5 for two way ranging because the antenna is matched for both channels.

Please let us know if you have any other question.