Hi in CST I want to simulate 2 antennas , the first one is to transmit and the other one to receive . When I run the simulation in CST it excites both antennas separately but I need to do this only for the first one and want to see the energy received by the other one.
You can define 2 ports and observe S21 parameter. This will show how much from transmitted energy is received by second antenna. S12 will show contraversa relation.