Cisco Cisco 1 GHz GainMaker Amplifier Guía De Instalación
741338 Rev D
Introducing Trim Networks
1-1
Chapter 1
Introducing Trim Networks
Overview
Introduction
The amplitude versus frequency response of an amplifier is defined as the variation
in amplifier output level over frequency relative to a flat input. Trim networks are
passive devices that compensate for amplitude/frequency variations by
superimposing a response that is opposite to that of the uncompensated cascade.
The amount of variation over a cascade of amplifiers combined with the response of
The amount of variation over a cascade of amplifiers combined with the response of
cable and passives make up the plant’s response. The deviation from straight-line
response varies depending on the system’s age and the condition of the amplifier,
cable, connectors, passives, etc. The sweeping process removes, to a great extent,
this deviation from straight-line response.
Trim networks are tunable resistance/capacitance (R/C) or inductance/capacitance
Trim networks are tunable resistance/capacitance (R/C) or inductance/capacitance
(L/C) circuits. Each one is designed to compensate for specific system anomalies.
The two most common trim types are as follows:
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•
peak trim network
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dip trim network
A trim network allows you to adjust the amplifier’s frequency response to be as
uniform as possible across the entire output spectrum. The trim network can be
adjusted (within limits) to cover a wide range of individual requirements. Type and
use factor is determined by evaluating actual system frequency response.
Peak Trim Networks
Peak trim networks operate as broad bandwidth, tunable attenuators.
The peak trim appears to raise a dipped or rolled-off region to the same amplitude
The peak trim appears to raise a dipped or rolled-off region to the same amplitude
as the surrounding carriers resulting in a flat response. In reality, the trim network
reduces the amplitude of the surrounding carriers while leaving the dipped or
rolled-off region at the same level. The peak trim typically introduces 2 dB of flat
loss. This is compensated for by reducing the input or interstage pad value.
Dip Trim Networks
Dip trim networks operate as narrow bandwidth, tunable attenuators.
The dip trim reduces the amplitude of a hump or peak to the same amplitude as the
The dip trim reduces the amplitude of a hump or peak to the same amplitude as the
surrounding carriers. The dip trim typically introduces 1 dB to 2 dB of flat loss. This
is compensated for by reducing the input or interstage pad value.