Functional Investigation; Demodulator Check; Viterbi Check; Demodulator Output Ports - Safran CORTEX Series User Manual

5.2

Functional Investigation

The following check-list can be followed for checking that the CORTEX HDR functions correctly:

Demodulator check: signal acquisition and demodulation.

Viterbi decoder check (if the Viterbi license is supplied).


Demodulator output ports.

5.2.1

Demodulator Check

Apply a modulated RF signal (input level between –10 and –50 dBm) to the Demodulator board and
verify the acquisition and demodulation process:
1. If the IF level status is lower than 50 dBm, check the RF connecting cable. Check also that the
IF input port is correctly programmed (Nominal or Alternate IF).
2. Check the correctness of the Demodulator status: Carrier Offset, BR Offset, PLL locked, Bit
Synchronizer Locked.
3. Check that the displayed constellation is the expected one and remains stable (see Figure 126):
 Four points on a circle for QPSK, OQPSK (SQPSK) and UQPSK (AQPSK, AUQPSK,
AUSQPSK) modulations.
 Two points on the abscissa axis for BPSK modulation.
 Eight points on a circle for 8PSK modulations
4. Check that the Eb/No status is correct.
If the Demodulator fails to lock, verify the setting of the unit.
5.2.2

Viterbi Check

1. Apply an RF signal with Viterbi encoded data and verify the acquisition and demodulation
process (see previous section).
2. Check the Viterbi Lock / Unlock status.
3. Check that the Viterbi BER status is in accordance with the estimated Eb/No status.
4. If the Viterbi fails to decode, check the setting of the Viterbi decoder: single or dual Viterbi
mode, G2 inverted, etc...
5.2.3 Demodulator Output Ports
Once the Demodulator and the Viterbi decoder (if any) are locked, check that the Demodulator output
signals are formatted as expected by the Ingestion System. In case of problem (wrong BER measured
by the Data Ingestion System), check that:
1. The output ports setting is correct: Output Clock, I/Q polarity, Normal or I&Q merged, Output
mode. If the problem remains, try different setting.
2. The PCM code is correct (NRZ-M, DNRZ, ...).
3. The hardware connections to the Data Ingestion System are correct.
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HIGH DATA RATE RECEIVER
HDR-4G+ USER'S MANUAL
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Ref. DTU 100782
Is.Rev 3.5
Date: June 1, 2021
Safran Data Systems
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