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User's Manual

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Table Of Contents
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.
2-59
The signal is first changed by removing the DC bias and which provides an RF level value in dB from the nominal
s
et point. The signal is then sent through three separate paths, 30 Hz am recovery, identification recovery, and 9960
Hz recovery.
The 30 Hz am recovery path has a 30 Hz low pass filter. The signal is decimated to 1 KHz then enters a 30 Hz band
pass filter. The output is the 30 Hz mod% and the 30 Hz used for the internal audio frequency counter.
The identification recovery path has a 1020 Hz band pass filter. The signal is decimated to 10 KHz then enters a
second 1020 Hz band pass filter. The output enters the 1020 Hz mod% detector. The signal is then analyzed for
continuous, missing or incorrect identification codes.
The 9960 Hz recovery path has 9960 Hz band pass filter which feeds the modulation detector, the audio frequency
counter and the FM deviation detector. The FM detector uses two quadrature mixers mixed with an internally
generated 10 kHz signal. The phase angle is computed and sent through a differentiator. This signal is band pass
filtered at 30 Hz. The signal is decimated down to 1 kHz and enters a second 30 Hz band pass filter. This output
feeds the audio frequency counter and the fm deviation detector.
The azimuth detector takes the 30 Hz am and 30 Hz fm signals and uses a quadrature mixer mixed at 30 Hz to
determine the phase of the am and fm signals. The phase angles are subtracted to provide the resulting Azimuth
angle.
The DSP U6 then compares the values obtained with the alarm limits. When an alarm condition occurs the front
panel LEDs are lit and alarm delay timer is activated. If the alarm continues and the alarm delay timer ends then the
alarm outputs to the LCU are activated. The LCU then within 0.5 seconds takes the action of transfer and or
shutdown.