Directivity is a measure of how well an antenna focuses its energy in an intended direction. Point-to-point radios should have highly directional antennas as the goal is to connect to end points of a link. Ideally, all the transmitted energy is directed just at the intended recipient. Highly focused antennas minimize the possibility of interference between links in the same geographic area, minimize the risk that the transmission will be intercepted, and maximize performance.

Operating at higher frequencies inherently results in a more focused antenna. Antenna directivity is limited by the physical principle of diffraction that states that the beam width is inversely proportional to the operating frequency. Therefore at 60 GHz, the beam width is far narrower than at the lower frequency unlicensed bands. Table 1 shows the beam width for several unlicensed frequency bands. These results are shown graphically in the next section.

Table 1 – Beam Width for Several Unlicensed Frequency Bands
For 1-foot diameter antennas