Harris Platinum Z2 CD, Руководство пользователя

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WARNING: Disconnect primary power prior to servicing.
Overall System Theory
4.3.3.6 IPA Power Divider (3dB Hybrid)
The IPA power divider is actually a 3dB hybrid which is used in the Z5 and Z10
transmitters to split the IPA output into 2 equal amplitude signals 90 degrees out of
phase to drive Z Planes A and B. In the Z2, only Z-Plane B is used and the hybrid is
not really necessary. However, for ease of manufacturing the same IPA backplane is
used in all Z series transmitters and the hybrid must be used. To make the hybrid
transparent to the system a shorting cable is placed between the two normal outputs.
This presents an infinite VSWR to the hybrid and all of the IPA power output is sent
to the reject port which is now used as the hybrid output to Z-Plane B (the PA).
4.3.4 Z-Plane Combiner/Divider Boards
There is only one Z-Plane Combiner/Divider Board in the Z2 transmitter. The board
provides all inputs to and outputs from the PA modules. The Z Plane is the overall
term for the combination of the Combiner and Divider board. There is a separate
schematic for each part of the Z Plane in the schematic package. The first page of
each schematic is identical and is a block diagram of the entire Z Plane.
The Z-Plane assembly contains:
•
Edge connectors for 8 PA amplifier boards (4 in front and 4 in the rear). These
connectors are labeled J1-J8.
•
An 8 way Wilkinson Divider, driven by the IPA, which feeds RF drive to each of
the 8 PA amplifiers.
•
An 8 way Wilkinson Combiner which combines the output of the same 8 PA
amplifiers.
The RF output of the Z-Plane board connects directly to the harmonic filter.
4.3.4.1 8-Way Divider
Refer to the Divider schematic for the following. The 8-Way Divider is a 2-stage
Wilkinson divider. The 8 way divider is located on the Z-plane board in the center
of the PA assembly.
The input to the divider is first divided into two equal outputs at approximately 35
ohms by a two-way Wilkinson divider with a 70.7 ohm isolation resistor, R9. Each
of these outputs (each end of R9) is then divided into 4 outputs in a 4-way
Wilkinson divider.
The Wilkinson dividers contain terminating resistors which dissipate no power
when all of the outputs are correctly loaded, but if a PA is removed, resulting in an
open-circuit on an output, the Wilkinson circuit and the load resistors act to keep the
input impedance of the splitter near the nominal value of 50 ohms. The 8 outputs
from the two 4-Way Dividers are fed to the input of the 8 PA Amplifier boards,
at J1 - J8.