Cisco Aironet 1242AG Access Point 规格指南
© 2011 Cisco and/or its affiliates. All rights reserved. This document is Cisco Public Information.
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Figure 2. Directional Patch Antenna
Figure 3. Yagi Antenna
Diversity Antenna Systems
Diversity antenna systems are used to overcome a phenomenon known as multipath distortion or multipath
interference. A diversity antenna system uses two identical antennas, located a small distance apart, to provide
coverage to the same physical area.
Multipath Distortion
Multipath interference occurs when an RF signal has more than one path between a receiver and a transmitter.
This occurs in sites that have a large amount of metallic or other RF reflective surfaces.
Just as light and sound bounce off of objects, so does RF. This means there can be more than one path that RF
takes when going from a transmit (TX) and receive (RX) antenna. These multiple signals combine in the RX
antenna and receiver to cause distortion of the signal.
Multipath interference can cause the RF energy of an antenna to be very high, but the data would be
unrecoverable. Changing the type of antenna and location of the antenna can eliminate multipath distortion
(Figure 4).