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User Manual
Rev. 1.0 - 28/02/11
PJ1000C/1300C/2000LCD
ELETTRONICA
7.2.2 Power Amplifier
RF power amplifier section is made with four power amplifier modules combined
through a Wilkinson splitter and a Wilkinson combiner in strip-line technology.
The splitter is used to divide input power from PWR Input Measure card and to
supply a quarter of it to every RF module. The combiner is used to combine output
power from every RF module so as to have total power amplifier.
Splitter, amplifier and combiner are plans so that powers generated from the
amplifiers add its in phase, diminishing the loss of balance and therefore the
dissipation of useful power.
All RF section is placed on a fin that supplies to the cooling through forced
ventilation.
Every RF module supplies 350 watts in
PJ1300C-LCD
model, or 300 watts in
PJ1000C-LCD
model, and is supplied from own switching supply.
The active device used in the amplifier modules is a Mosfet (SD2942 in
PJ1300C-
LCD
model, or SD2032 in
PJ1000C-LCD
model)
.
7.2.3 LPF card
This card is a low-pass filter and its function is to suppress the harmonic components
generated by the amplifier below the levels required by regulations.
Moreover, in the end of filter, there is a directional coupler, its function is the
measurement of the forward and reflected output power.
On this card there is an RF sample at -60 dB compared with the output and it is
available on a BNC connector. This sample is useful for checking the characteristics
of the carrier, but not of the higher order harmonics.
7.2.4 BIAS card
Main function, of this card, is to check and to correct the polarization voltage (BIAS)
of Mosfet in RF amplifier section.
Moreover it supplies the measure of the absorbed current as sum of the absorbed
currents from every module and it contains a circuit for the signalling of the
breakdowns in the Power Supply.
