4-42 888-2406-002
WARNING: Disconnect primary power prior to servicing.
Overall System Theory
4.7.4 PA Controller Board
The PA Controller Board utilizes a micro-controller which reports to the Master
Controller, but operates independently of the Master. The board ID is set via DIP
switches to make it PA Controller #1. The Backplane Board has slots for up to 4 PA
Controllers which are used for the higher power Z Series transmitters such as the Z5
and Z10. Each PA Controller can handle 8 PAs and therefore only one is needed in
the Z2, except in the Z2R which uses 2 PA Controllers for increased redundancy
(see Table 4-1 on page 4-59).
The PA Controllers are responsible for the following:
• Turn on/Turn off of the PAs via the PA gate bias voltage.
• Metering, status and fault monitoring of the PAs and the isolation resistors associ-
ated with them.
• Control of the combiner isolation switches (located on the isolation boards)
which are associated with the PAs under its control.
• Crossover protection - the ability to mute the PAs which are controlled by the
other PA Controller Board in case of a failure (only available in the Z2R)
4.7.4.1 PA Turn On/Turn Off
The PA Controller’s primary responsibility is to turn the PAs on and off. The PAs
are turned on and off by varying the bias voltage on the gates of the MOSFETs on
the PAs. If the gate voltage is -0.6V, the PA is turned on full. If the gate voltage is -
18V, then the PA is turned off. This means the PA Controllers have the ability to turn
off or MUTE each PA individually, or all at the same time if it is necessary to
MUTE the entire transmitter RF output.
Whenever a defective PA is to be shut off or MUTED, all of the PAs will be
MUTED for 120mS while the defective PA is disconnected from the combiner by
the isolation switch. The rest of the PAs are then turned back on.
4.7.4.1.1Control Distribution and Controller Failure (Z2R Only)
Each PA Controller controls half (4) of the PAs, see Table 4-1 on page 4-59. Note
that each PA Controller Board controls two PAs on each foursome. This pattern of
control distribution allows for maximizing of power output if one of the PA
Controller Boards fails.
4.7.4.2 Metering
The PA Controllers are responsible for metering of the following parameters:
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