Control wave direction or path

[Gholzam]

In my plan I have a rf moudle NRF24l01 , this is not important, so , If you see in figure 1 we have radio masts that send waves in around. we can't accept this. my plan for control wave direction is on the figure 2. like ultrasonic ,but how?

[Asbjørn]

Phased arrays or directive antennas are the options you have for this scenario. Usually it desired to have antennas that are as omnidirectional as possible for the kind of application the nRF51822 is inside, but there's nothing wrong with using a directive antenna. Make sure that the input impedance is 50 Ohm and the frequency range is within the 2.4 GHz band.