ADTRAN TRACER 6000 SERIES, Руководство пользователя

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TRACER 6000 Series Split System Manual Section 2 Microwave Path Engineering Basics
612806320L1-1B Copyright © 2005 ADTRAN, Inc. 23
TRACER RSSI Test Points
RSSI for the TRACER 6000 Series split system is provided through the RSSI test points located on the
front of the TRACER 6200 IDU and on the bottom of the TRACER 6320 ODU. It is also presented via the
VT100 terminal menus as a series of bars indicating signal strength. More bars means more RSSI, which
ensures greater received signal strength and better link performance.
If both the local and remote end of the system are operational, the remote system receive power can be
viewed from the local TRACER 6200 IDU VT100 terminal menu interface.
An RSSI test point is provided on the front panel of the TRACER 6200 IDU and beneath a weatherproof
cap on the bottom of the TRACER 6320 ODU. The RSSI test points provide a DC voltage level (relative to
the
GND test point) that corresponds to the amount of signal being received from the far end’s transmitter.
The voltage at this test point can vary from approximately 0 to 5 VDC. An RSSI calibration sheet is
shipped with the system to provide the installer a cross-reference between actual received signal level (in
dBm) and RSSI voltage. This sheet is useful for verifying link budget calculations and ensuring proper
equipment installation
Antenna Beam Patterns
Directly related to the subject of antenna alignment is the topic of antenna beam patterns. Antennas used
with the TRACER system have a particular beam shape, determined in part by the physical construction
and geometry of the antenna. The antenna beam patterns are characterized by a dominant main lobe, which
is the preferred lobe to use for point-to-point communications, and several side lobes, as shown in
Figure 2. When setting up a microwave link, antenna alignment is nothing more than steering the main
lobes of both antennas until the main lobe of one transmitter is centered on the receiving element of the
receiving antenna.
Figure 2. Typical Antenna Beam Pattern
Antennas are also designed to radiate RF energy efficiently for a specific range of frequencies. Please
consult the data sheet for your particular antenna make and model to ensure that it is specified to operate in
the 5725 MHz to 5850 MHz frequency band for the TRACER 6320 system.
Fresnel Zones, Earth Curvature, and Antenna Heights
Fresnel zones correspond to regions in the microwave path where reflections of the intended signal occur
and combine in both constructive and destructive manners with the main signal, thereby either enhancing
or reducing the net power at the receiver.
main lobe
side lobes