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4-3
WARNING: Disconnect primary power prior to servicing.
Overall System Theory
4.2.2
IPAs
The Z5 has 1 IPA Module, which is made up of 2 power amplifiers or PAs. The IPA
Module is identical to, and interchangeable with, the PA Modules. The 2 IPAs per
IPA Module operate in Main/Alternate mode, meaning that only one of them is
active at a time. The block diagram shows that IPA_AB1 is the normally active
amplifier. RF switching on the input and output of the IPA is activated by the
controller if a fault is sensed in the active IPA. The IPA output is split using a 3dB
hybrid built onto the IPA Backplane Board. This provides 2 equal amplitude outputs
90 degrees out of phase to drive the Power Amplifiers.
4.2.3
PA
The Z5 contains two Z-Planes which could be considered 2.5kW Power Blocks. For
simplicity in Figure 4-1, Z-Plane A is the only one which shows the actual
component assemblies located on each Z-Plane. Z-Plane B is identical. Next, each
Z-Plane can also be broken down into 2 parts, a Divider Board and a Combiner
Board.
4.2.3.1 Z-Plane Divider Board
The Divider Board takes the IPA input and uses a 2 way wilkinson splitter to drive
two more 4 way Wilkinson splitters. This provides the necessary 8 drive signal for
the 8 PAs connected to Z-Plane A. The PAs are labeled A1-A8 for Z-Plane A and
B1-B8 for Z-Plane B. PAs 1-4 on each Z-Plane are located in the front of the
transmitter, while 5-8 are located in the rear of the transmitter. Any four PAs labeled
1-4 are considered a FOURSOME, because they are connected to the same 4 Way
combiner. Any PAs labeled 5-8 are also considered a Foursome. Here is a list of the
4 different Foursomes in the Z5: (See Figure 4-5 and Figure 4-6)
•
A1, A2, A3 and A4 - Front, Z-Plane A
•
B1, B2, B3 and B4 - Front, Z-Plane B
•
A5, A6, A7 and A8 - Rear, Z_Plane A
•
B5, B6, B7 and B8 - Rear, Z-Plane B
4.2.3.2 Z-Plane Combiner Board
The Combiner Board receives the outputs from the 8 PAs and combines them in two
4 Way Isolated Wilkinson Combiners, whose outputs are then combined in a 2 way
Wilkinson combiner for a 2.5kW nominal output. Each PA is capable of delivering
up to 425 watts into a good load, but will be operating at approximately 325 watts
nominally for 5kW of combined transmitter output. The isolation loads for all 3
combiners are located on another board called the Isolation Board for better heat
dissipation and easier access. The Isolation boards are located on each side of the
Power Block. The Isolation Board also contains RF switches which can switch out a
faulty PA without causing a severe system imbalance, allowing greater redundancy.
Содержание Z5 CD
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