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User Manual
Rev. 1.0 - 29/06/09
PJ2500M-C, PJ3000HE, PJ3500M-C,
PJ4000U-K & PJ5000U-K
8.3 RF Part
8.3.1 RF Power Amplifier
The RF power amplifying section consists in 8 (mod.
PJ2500M-C, PJ3000HE,
PJ4000U-K
e
PJ5000U-K
) or 6 (mod.
PJ3500M-C
)
power modules coupled by
a Wilkinson splitter and combiner and implemented in strip-line technology.
The RF modules, the splitter and the combiner are housed inside the top part of
the equipment.
The whole RF section is mounted on the fin that cools the equipment by means
of forced ventilation.
Each RF module supplies 550 watts in
PJ4000U-K
model, 600 watts in
PJ3500M-
C
model or 375 watts in
PJ2500M-C
and
PJ3000HE
model with 4 to 6 pilot power
watts and is powered by the switching PSU.
The modules’ operating parameters in standby are as follows:
VDC=50V Vgs=3.5V Idq=200mA
The active device used in the amplifier modules is a Mosfet (2x) SD2942 for
PJ5000U-K
and
PJ3500M-C
,
(2x) BLF278 for
PJ4000U-K
and SD2942 for
PJ2500M-C
and
PJ3000HE
.
8.3.2 Wilkinson Splitter and Combiner
Both the splitter and the combiner are made in strip-line technology.
The splitter is used for splitting power arriving from the exciter and supplying one
part to each of the RF modules.
The combiner is then used to combine power output from each module to obtain
the amplifier’s total power.
The two cards ensure equal phases among the powers generated by the RF
modules. One power resistance is used for dissipating the offset power that might
be present in case a module breaks down.
The Splitter card is also fitted with the temperature sensor which is monitored by
the software.
8.3.3 Bias Board
The task of this card is to check and correct the bias voltage of the Mosfets in the
RF amplification section.
