User's Manual

Model 1150A DVOR
2-58 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.
A/D
Sample
Controller
DMA
Controller
TIMER0
IF ADC
U24
125 kHz
SPORT 1
Serial
Interface
DMA
Controller
DSP1
U6
SPORT 0
Serial
Interface
DMA
Controller
Audio DAC 1
U69
Audio DAC 2
U71
Input Buffer
(1000 Samples)
Detected Audio Buffer
(4000 Samples)
BP 125 KHzLP 20 KHz

ABS
BP .3-4 KHz LP 5 KHz

BP 1020 Hz
Voice and Ident Buffer
(500x2 Interleaved Samples)
Recovered Voice
Recovered Ident
Thresholder
LP 20 KHz

Buffer1
Buffer 2
Buffer 3
U75 DSP
Figure 2-22 Monitor DSP (U75) Signal Processing Diagram
VOR Signal Demodulation
Refer to Figure 2-22. The DSP U75 samples the 125 KHz IF signal using analog to digital converter U24. The DMA
controller within U75 synchronizes the sampling of data. The data is stored in internal buffer 1. The data then is
bandpass filtered with center frequency of 125 kHz. The data runs through an absolute value calculation which
rectifies the signal. The signal is then low pass filtered with a cut off frequency of 20 kHz. The signal is then down
sampled by a factor of 5. This signal enters the intermediate buffer 2. This buffer 2 data is serially transferred to
DSP U6 for extraction of the VOR azimuth, 9960 Hz modulation, 30 Hz modulation and deviation ratio. The
contents of buffer 2 are also sent through a 20 kHz low pass filter. The signal is then down sampled by 2. The signal
is then low pass filtered with a cut off frequency of 5 kHz. The signal is then down sampled by 4 and enters a band
pass filter with a pass band of 300 to 4000 Hz which contains both voice and identification signals. The voice then
enters the buffer 3 Voice and Ident buffer. The voice also enters a bandpass filter centered at 1020 Hz to pass only
the ident.
Half of buffer 3 contents are transferred to Audio digital to analog converter U69 for the recovered voice and then
through the U16 Audio Amplifier and off the Monitor and eventually the headphone jack on the Test Generator. The
other half of buffer 3 contents are transferred to Audio digital to analog converter U69 for the recovered voice and
then through U71 then unity gain buffer U72a. This signal leaves the Monitor and then goes to the Facilities CCA
for possible connection to the speaker so that the technician can listen to the identification if selected through the
PMDT.
Refer to Figure 2-23. The DSP U6 samples three different VOR detected signals. One is the output of the receiver
section for mU75. The second is the Test Generator signal. The third is the detected standby transmitter signal from
the RF Monitor. One signal at a time is sent to the VOR signal processing routines.