User's Manual

30 kW S-BAND/U ANTENNA GROUP
FUNCTIONAL DESCRIPTION
3.5 Rev. C
The signals used in this circuit are:
- 70 Vdc from TRANSCEIVER 30S Power Supply Unit
- 18 VAC from the RTM CONT B Board
- LPA (Long Pulse Adjustment), MPA (Medium Pulse
Adjustment) and SPA (Short Pulse Adjustment) from
MICROPROCESSOR of RTM CONT B Board
- HVON from MICROPROCESSOR of RTM CONT B Board
The 70 Vdc is applied to the RECTIFIER through a protecting fuse, external to
the board, and its presence is visualised when the LED DL2 (MAIN VOLTAGE),
mounted on the board, is lit.
The 70 Vdc (VMOD) is applied to the primary of the HVPS TRANSFORMER
which, controlled by the MOSFET, generates, as output, the required high
voltage (700 V).
The MOSFET activation is controlled by a circuit, which, also, protects the
MOSFET itself.
The circuit is composed by the blocks COMPARATOR, POTENTIOMETER and
FLYBACK CONTROLLER. When the COMPARATOR recognises that the
output voltage is present, it activates the FLYBACK CONTROLLER which
receives as input the output voltage adjusted by the POTENTIOMETER
according to the pulse length (signals LPA, MPA and SPA).
This way, it is possible to control the Magnetron output power.
3 .3 .2 .2 Pulse Gener a t or Cir cuit
The Pulse Circuit Generator function (Chapter 9, Figure 9.1.11) is to generate
the necessary high voltage supplying the Magnetron, in accordance with the
previous selections.
The Input Pushing Trigger is TRPUSH and the input Pulling Trigger is TRPULL;
both from RTM CONT B Board. To the Pulse Circuit Generator is applied also
the 700 V from the HVPS Generator Circuit.
To one terminal of the primary windings of the PULSE TRANSFORMER is
applied the 700 V whilst the second terminal is connected to the MOSFET
(push and pull).
The pulse is generated in accordance with TRPULL and will be pushed in
accordance with TRPUSH; in fact the current flows only when the Transformer
is grounded with the TRPULL. Every time there is 700 V on the primary, there
is, as well, -8000 V on the secondary windings of the PULSE TRANSFORMER.
According to this configuration, the R.F. is sent to the antenna from the
Magnetron.
To get the best operating conditions for the Magnetron, there is also a need to
generate a voltage, named VFIL which is applied to a section of the secondary
windings of the PULSE TRANSFORMER. As result, the FIL signal, sent to the
Magnetron, has always a potential greater than the K potential.