EUROTEL - ITALY
ETL0480TBD
VI - FUNCTIONAL DESCRIPTION
1 ) Theory of operation of 1 kW UHF RF Amplifier ETL0480TBD
•
With reference to the general Blocks diagram, Figure 3, the output signal from the Exciter, at a
nominal level of 4 W, reaches the low power, 3 dB hybrid, which splits the drive into 2 components
of 2 W each. This hybrid incorporates a step attenuator and a step phase shifter to adjust the slight
differences of gain and phase of the two RF Amplifiers. The resultant signals drive the two ETL0470
tandem connected RF Amplifiers to an output level of 600 W each. The 3 dB high power hybrid
connected to the outputs of the two RF Amplifiers sums the output signals to a nominal level of
1kW.
#1
“E”
LINK
RF reflected power
RF forward power
Dir.
Coupler
A.L.C.
Enable
commands
RF
output
Bpass
filter
3 dB Hybrid
50 Ohm
load
Amplifier
ETL0470TAD
“SLAVE”
#2
Amplifier
ETL0470TAD
“MASTER”
50 Ohm
load
3 dB Hybrid &
gain+phase
equaliser
EXCITER
(external)
RF output
Figure 3: ETL0480TBD TV RF Amplifier blocks diagram
•
At the output of the power 3 dB hybrid a directional coupler collects samples of forward & reflected
output power, which are sent to the two ETL0470 RF Amplifiers Modules. Here they are processed
by their internal metering, alarm and protection modules.
October 2002
CMAN0480ENG
Page 11
