Safran CORTEX Series - Figure 41: Frame Synchronization Process

HIGH DATA RATE RECEIVER
HDR-4G+ USER’S MANUAL
Ref. DTU 100782
Is.Rev 3.5
Date: June 1, 2021
© Safran Data Systems – IMP000074 e14r1
This document is the property of Safran Data Systems.
It cannot be duplicated or distributed without expressed written consent.
Page 125
The frame synchronizer synchronizes the frame in accordance with the SYN, CTL, LTS and Bit Slip
parameters provided to it:
Figure 41: Frame Synchronization Process
Frame Synchronizer Input 3.4.2.2
Frame synchronizer input can be either I or Q or merged I & Q. Depending on the demodulation and
decoding scheme, the following setting must be programmed (refer to parameter Input Selection in the
Data Processing Unit. Section 4).
Automatic PSK Ambiguity Resolution 3.4.2.3
Automatic PSK Ambiguity Resolution is performed only if parameter IQ output polarity in the
Demodulator Unit Monitoring Table is set to Ambiguity solved by DPU (see section 4.5.4.1.1.1 ).
Should the data at the bit synchronizer output be ambiguous, good data can be obtained by using this
Ambiguity Resolution Mode.
Phase or channel ambiguity resolution is then automatically performed by the frame synchronizer
during the SEARCH phase (and only during this phase). If the comparison between the expected
synchronization word and a given window on the received data stream fails, another phase & channel
configuration is checked and the process is repeated until the frame synchronization word is identified.
The frame synchronizer switches then to the CHECK phase.
S
L
S: SEARCH
C: CHECK
L: LOCK
SW 7,F incorrect
NT
SW 0,8
correct
SW 2,A
correct
SW 1,9
correct
SW 3,B
incorrect
SW 4,C
incorrect
SW 6,E
incorrect
SW 5,D
incorrect
NT
NT
NT
(1)
(1)
(2)
(3)
(3)
(3)
T
NT
T
Scenario: CTL = 2, LTS = 3
SW: Synchronisation Word
NT : frame not transmitted
T : frame transmitted
Received telemetry:
Frames 0 to 2: SW correct
Frames 3 to 7: SW incorrect
Frames 8 to A: SW correct
Frames B to F: SW incorrect
Dotted lines: alternate scenario (different frame contents)
(1): return to search mode if SW incorrect
(2): stay in lock mode while SWs are correct
(3): return to lock mode if SW correct
NT
NT
T
T
T
T
F
F
F
C
C
NT
T
F: FLYWHEEL