Deploying License-Free Wireless Wide-Area Networks

Combining Antenna Systems

There are a number of reasons to combine antennas or to connect more than one antenna simutaneously to the same piece of wireless equipment. Often, antennas are combined to modify the directivity and the gain of an antenna system. For example, the horizontally polarized omni in Figure 5-12 is made up of four horizontally polarized omni antennas placed (stacked) close together and electrically connected. When these four antennas are stacked together to create one antenna system, the gain goes up by +6 dB and the vertical beamwidth of the main lobe narrows by a factor of four. (Donut-to-pancake—remember?) You might have situations in which you need to combine antennas to create a custom coverage pattern.

Multipath fading ...