Assume I have a MIMO channel matrix \$H\$ of dimension [\$N_r\$ \$N_t\$ \$N_f\$] where \$N_r\$ are the number of antennas at the receiver, \$N_t\$ the number of antennas at the transmitter, and \$N_f\$ the number of subbands. If I just look at one receiver element, I can visualize the channel in the beam-delay domain by applying an IDFT on the \$N_t\$ dimension and \$N_f\$ dimension. My question is how do I get the angles in the beam-domain?
Essentially, I am trying to recreate the figures from the following papers:
Figures 2.1 and 4.1 from: https://www.semanticscholar.org/paper/An-Efficient-Beam-and-Channel-Acquisition-via-Map-Kalayci-Guvensen/ef4a11725ea08159b5cca06c533d3a4c4d569af0
