Cisco Cisco 1 GHz GainMaker Amplifier インストールガイド
Chapter 3 Balancing and Setup
Balancing the Reverse Path
This section covers reverse RF amplifier cascade balancing. Balancing refers to the
process of individually aligning reverse amplifier station gain and tilt characteristics to
achieve reverse amplifier cascades that have optimum, repeatable transmission
characteristics.
There are a variety of test equipment combinations that enable proper balancing of the
There are a variety of test equipment combinations that enable proper balancing of the
reverse path. Regardless of the type of equipment used, the balancing process is
fundamentally the same.
About Reverse Path Balancing
Balancing should be completed in the following order.
1
Balance the reverse fiber link, i.e., the path from the node reverse optical transmitter
to the headend or hub reverse optical receiver.
2
Balance the individual reverse amplifier cascades that combine at the node. Start
with the amplifier closest to the node, and work from that point outward towards
the first reverse amplifier in each upstream cascade.
Injection of Test Signal(s)
During the balancing process, a reverse RF test signal or signals of known amplitude are
injected into the reverse RF input path of the amplifier station prior to the reverse
amplification circuit. The injected signals are amplified and routed out the station
reverse RF output port in the upstream direction. The injected test signals pass through
any previously balanced amplifiers in the reverse cascade, as well as the reverse fiber
link, and arrive at the node reverse optical receiver, which typically is located in the
headend or hub.
Monitoring and Adjusting Received Amplitude and Tilt
The amplitude and tilt associated with the received signals are monitored at the headend
or hub at an RF test point on the output of the reverse optical receiver associated with
the particular node. The received amplitude and tilt of the test signals are compared to
the desired (reference value) amplitude and tilt. Any deviations from reference value
amplitude or tilt are then minimized by altering the (dB) value of the output pad or
equalizer in the amplifier being balanced. This process is completed for each amplifier in
the reverse cascade, working outward from the node.
Methods of Generating and Monitoring Test Signals
The reverse RF test signals to be injected into the reverse path of the amplifier being
balanced may be generated by the following.
Multiple CW signal (tone) generator
Reverse sweep transmitter
74
OL-31155-01