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.
2-7
The Audio Generator CCA generates the carrier modulation signals, monitors and controls power levels, and directs
t
he RF phase control signals for the DVOR transmitter.
Each sideband generator contains one CCA within the assembly. Functionally, each sideband generator has two
sideband amplifiers on the one sideband amplifier CCA. Each sideband amplifier is designed to amplify and
modulate one of the four individual sideband signals used by the DVOR system.
The CSB power amplifier contains one CCA. The CSB power amplifier assembly amplifies the carrier RF signal to
the operational power level of the station and modulates it with the specified audio signals. A sample of the RF
energy to be used as an error correction feedback signal that is sent to the frequency synthesizer assembly. A second
sample of the RF is provided on the front panel test point on the CSB power amplifier assembly. A directional
coupler in the carrier feed-line allows sampling of the forward and reflected RF energy.
The RF monitor processes the main and standby RF signals for use by the audio generator and VOR monitor CCAs.
The RF monitor contains all the dummy loads, for use by the standby transmitter.
The field monitor antenna cable enters the two way equal power splitter in the cabinet. The outputs of the power
splitter feed each of the two VOR monitors for processing and analysis. Each VOR monitor CCA works
independently from the main transmitter and from each other; however, the alarm control features of both monitors
can be organized to function in a logical AND or logical OR arrangement.
2.3.2.1
Frequency Synthesizer (1A3A1, 1A3A11)
The Synthesizer assembly generates a three RF signals (carrier, upper and lower sidebands) for the VOR transmitter.
There are three boards in the Synthesizer Assembly. The Carrier board provides the carrier frequency (see Table
9-4) and the phase control capability for the Carrier Amplifier. The long term phase is kept constant in the carrier
amplifier by means of a phase control loop in the synthesizer. The phase control loop also removes unwanted phase
modulation in the carrier amplifier due to amplitude modulation.
The sideband board generates the upper and lower sideband frequencies for the Sideband amplifier Assemblies and
provides the ability to adjust the sideband generator phase over 360 degrees relative to the carrier. This eliminates
the need to cut the antenna cables during installation.
2.3.2.1.1
Frequency Synthesizer Block Diagram Theory
Refer to Figure 2-4. The function of the Frequency Synthesizer Assembly is to create the Carrier, Upper Sideband,
and Lower Sideband radio frequencies radiated by the VOR Transmitter. The Synthesizer Assembly is used in both
CVOR and DVOR system configurations. The Synthesizer Assembly generates the Carrier Signal using a
synthesized PLL and control loop to lock the frequency. In addition to the PLL synthesized RF Generator, there is
another phase lock loop in the Synthesizer. This loop is used to maintain the carrier phase relative to the reference
RF signal, and correcting for amplitude modulation induced phase mod on the VOR Carrier Transmitter output
signal. There are three boards (CCAs) in the 030838-0001 Frequency Synthesizer Module, the 012258 Sideband
CCA, the 012262 Interface CCA, and the 012263 Carrier CCA. The majority of the circuitry is located on the
012258 Sideband CCA and the 012263 Carrier CCA; with the test port buffer amplifier and audio generation
circuitry on the 012262 Interface CCA.
There is a temperature compensated crystal oscillator, or TCXO, on the 012262 Interface CCA that generates a
10.000 MHz reference signal. This signal is buffered and divided by 50 to create a 200 KHz loop reference signal
for the carrier PLL. The 10.000 MHz reference signal is also buffered and sent directly to the Direct Digital
Synthesizer (DDS) for processing of the 9960 Hz signal generation.