How to get I and Q data from the antenna array for direction finding purpose?

[Rishitha]

Hello,

I am currently working on bluetooth direction finding using AoA. I have a doubt regarding the math involved in the calculation of AoA. It's pretty clear that we need I/Q data in order to find the phase difference between the antennae to further proceed with the calculation of AoA. My doubt is how to get that I/Q data after building and flashing nrf5340 boards to work as tx and rx.

Thankyou.

[SwRa]

Hi Rishitha,

You will need to make necessar changes in cte_recv_cb() in main.c to print the I and Q samples.

You can take a look at this ticket:  RE: AOA: Antenna switch pattern and IQ sampling via nrf52833  

You always have to convert the IQ data into a vector, and then examine this to get a useful positioning data. Some formulas for calculating with IQ signals translating between polar and rectangular forms can be found here: https://www.pe0sat.vgnet.nl/sdr/iq-data-explained/

Peak Amplitude A = (I²+Q²)½

Phase Angle ϕ = tan⁻¹(Q/I)

I = A⋅cos(ϕ)

Q = A⋅sin(ϕ)

Converting IQ Data to a plain signal: I is the original signal.

Euler form: A⋅eiϕ = A⋅(cos(ϕ) + i⋅sin(ϕ)) = I + Qi

Regards,
-Swathy

[Rishitha]

Hello Swathy,

Thankyou so much for the reply.