Basically, there are two types of antennas:
Omni and directional (usually broken down to directional and SEMI-directional)
Within the directional (semi-directional) categories you have patch, sector, yagi, and parabolic ("dishes")
Patch antennas are usually indoor, and have a horizontal radiation pattern of 180 degrees or less. You put 'em on the wall to radiate into the forward space.
They are usually vertically polorized, but can be rotated for horizonal polorization (like, if most of your clients are laptops, which are usually horizontally polorized NIC-Attached antennas (buil-ins ... I don't know).
Sector antennas are usually outdoor use and tend to run a horizontal coverage of ~120 degrees or less. They also tend to have very small back-lobes so they can be mounted back-to-back on a mast or tower and not interfere with one another.
Yagis are (usually) multi-element, boom-and-crossbeam style directional antennas. The beamwidth depends on the gain (wich results from the number of elements).
Yagis have three types of elements: the driven element (what the cable connects to), directors (ahead of the driven element, usualy slightly shorter in length), and reflectors (behind the DE, usually a little longer).
By placing the DE, directors, and reflector(s) at specific locations, relative to the DE, ou can collect and greatly narrow the beamwidth, which appears as an increase in apparant gain.
Yagis can be vertically or horizontally polorized, depending on the orientation of the DE when the antenna is installed. Both sides should be the same orientation.
Parabolics are the highest gain for a single radiating signal, yagi's are next, sectors & patches can be about the same.
Regarding 'Panel' antennas: There are several interpretationsof the word "panel." Some people may call a patch a panel ... but I'm pretty sure that's incorrect.
Panel antennas are usually "Phased Arrays:" a flat surface with a bunch of potential radiators on them (usually tuned at some harmonic length) .... think of a board full of long nails driven through it ... or a "bed of nails."
Each of the radiators ("nails") are individually controlled such that the phase and amplitude of the signal can be adjusted. By changing the phase and amplitude correctly, you can steer the signal and vary the gain.
Many PA panels permit multiple simultanious signal, each "following" the host as possible. In this case the PA actually radiates more (can radiate more)(collective) power than a single yagi or possibly a dish ... but it's permitted since each individual "beam" is within the EIRP spec for the system.
Cisco has Omnis, Patch, Sector, Yagi, and Parabolics.
(two types - omni and directional/semi-directional)
Good Luck, I hope this helps to clear thing up for ya.
Scott
