AoA test, how to calculate the phase diffence of the 2.4G wave?

[upupsky]

I used direction finding rx/tx examples(get 45 points of IQ data). I used the ref period IQ data (8 points) can caculate base phase and the phase velocity(setting is 500KHz. Actually is 490KHz), then I also can predict the un-shifted phase for each of the sample/slot period IQ data samples(37 points).

Questions:

1. According to "nwp_036.pdf" file(page 10), the phase= atan2(Q,I). THEN, the phase diffence = atan2(Qm,Im) - atan2(Qn,In) , means phase diffence anntena 'm' and anntena 'n'. Can the "phase diffence" used to calculate the "distance diffence" in page 8, Figure 4: Measuring AoA??   (I think, the phase diffence is ablout 500KHz wave, not the ble 2.4G wave, It can not used to in page 8)

2.ble 2.4g modulate 500k, but ble is hopping every 2M(40*2M=80M), How can I get the real frequency of the ble?? then I can calculate the "phase diffence" of ble 2.4g wave.

3.if the phase= atan2(Q,I) used in page 8 directly, the distance of two anntena should not λ/2=6cm (the λ comes from ble 2.4g, NOT the 500K). the "phase diffence" comes from IQ, is represented the wave 500K or 2.4G??

[Simonr]

Hi

This case has already had a discussion on the AoA mathematics. Please give it a read. Both SwRa and PaKa are Nordic Semiconductor employees FYI.

Best regards,

Simon

[upupsky]

thank you very much. I read the case for several time, but I am still confuse. this is my matlab code about how to calculate phase diff.

Sn_sample9_37 = (0:36)'*4;  %the sample/switch slot data
phi9_45 = phi_fm(9:45) - 2*pi*(fm_250_est - f0_250k) * Sn_sample9_37 * Ts; %use estimate frenquency calculate phase
phi9_45_phase_diff = mod(phi9_45(1:32), 2*pi);