IWR1642BOOST: How to perform angle FFT from raw data captured with DCA1000 and IWR1642

Hello, 

I have a quick question on performing angle FFT (anlge estimation) from raw data. I was using DCA1000 and IWR1642 with setting of 1 TX and 4 RX. I understand how to perform the range FFT and doppler FFT from the raw data. I also learned that to perform the angle FFT I need multiple RX antennas (in my case, it is 4).

I have perform the range and doppler FFT like the picture below from the raw data. 

However, I have no idea how to perform angle FFT (anlge estimation) across the above matrices. The angle range in the azimuth plane is -90 to 90. 

Could you give me some hints on how to do the angle FFT (angle estimation)? I learned mmWave studio integrated the matlab processing functions but I could not find it.

Thank you very much for the help!

Best,

Hang