User's Manual

Model 1150A DVOR
Rev. - November, 2008
This document contains proprietary information and such information may not be disclosed
to others for any purposes without written permission from SELEX Sistemi Integrati Inc.
2-73
Each individual antenna switch circuit on a Commutator CCA is functionally identical with the others. Pin diodes
a
re used to perform the active switching of the RF to the individual antennas, and to swap the LSB and USB signals
between each half of a switch assembly.
Each Commutator CCA can be thought of as having two halves; each half is connected to twelve antennas. One half
is energized by the LSB RF and the other half by USB RF. The condition of the transfer and NOT transfer lines
(from the driver board) determine which half of the Commutator CCA will process the two RF signals.
Each antenna switch on each half is applied RF energy via a common bus. The transfer control switches the two RF
signals between the two bus lines, while maintaining complete isolation between them. Since the pin diode switches
are operating with either +5V or -10V applied, those voltages insure the diodes are either fully on or off.
When the XFR line is high (+5V) the NOT XFR line is low (-10V), the arrangement turns on A bus pin diode switch
1 and B bus pin diode switch 2. B bus pin diode switch 1 and A bus pin diode switch 2 are biased off. Therefore,
the LSB RF signal will be switched to the A bus and the USB RF signal will be switched to the B bus.
When the XFR and NOT XFR signals change polarity, the condition of the A and B pin diode switches change
which makes the LSB RF signal be sent to the B bus and the USB RF signal goes to the A bus.
To enable the RF energy to be selectively applied to an individual sideband antenna, and at the same time prevent
parasitic re-radiation from an adjacent antenna, a pin diode antenna switch is used. The drive levels are similar to
the transfer levels used to switch the LSB and USB RF energy.
Each antenna assembly has twenty-four switches. Twelve are connected to the “A” bus and twelve to the “B” bus.
Display driver U8 on the driver board drives both the 1A and 14B positions; display driver U13 handles both the 2A
and 15B positions, etc. (see Table 2-1). This allows opposite paired antennas to radiate the LSB and USB signals.
Each display driver will control two antennas simultaneously. If sideband antenna #1 is a radiating antenna, then
sideband antenna #25 is also a radiating antenna. The action of the pin diode antenna switch networks will supply
the RF energy from the two buses into antenna #1 and #25 RF feed cables and the RF feed lines of all the other
antennas are switched into on-board dummy loads.