Harris Maxiva ULX, Technical Manual

Page: 178 / 308

4-42 888-2629-200 10/6/10
WARNING: Disconnect primary power prior to servicing.
Section 4 Theory of Operation
Maxiva ULX COFDM Series
combining of the signals is done in series fashion with the first stage being a 2-way 3dB
hybrid, the second stage being a 2-way 4.77dB hybrid, and the 3
rd
stage being a 2-way
6dB hybrid. Each RF input is isolated from the others by using 50 Ohm 500W reject
loads. This allows continuous operation of the PA Module in the event of a PA Pallet
failure. The combiner contains Forward and Reflected signal directional couplers at the
output trace. Two directional couplers have envelope detector circuitry included. The
detector circuitry serves to deliver a sample of envelope detected signal to the Monitor
Board (p/n 9010222051G). The sampled base band signal amplitude indicates power
level in dBm. The third directional coupler serves to deliver a scaled down sample of
output RF signal to a specially designated coaxial port at the front panel of the PA
Module.
4.6.3.10 RF Pallets
The PA pallet serves as the single stage of amplification in the Triton module. There are
4 PA pallets operating in parallel in this PA module. A simplified diagram of the pallet
is given in Figure 4-17. Each pallet has a hybrid splitter on the input side of the FET’s.
The hybrid divides the RF input signal into two equal parts to feed the two pallet FET’s.
There is another hybrid at the output of the FET’s that is used to combine the amplified
outputs. The RF pallets are field replaceable. Replacement instructions can be found in
section 5.6 on page 5-11.
Figure 4-17 PA Pallet Simplified Block Diagram