Wavecom W-SPECTRA (Automatic Monitoring System) V1.1.0 - Manual (Page 214)

204

Classifier – the Brain of W-SPECTRA WAVECOM Monitoring System W-SPECTRA, W-SPEED Manual V1.1.0
PSK A and B Signal Confusion
Under certain conditions the classifier cannot distinguish between the A and B variants of PSK modulation.
A PSK signal of one variant may be mistaken for the other variant if the signal is offset from the real cen-
ter frequency with a certain fraction of its baud rate; i.e., for PSK-2 ¼, for PSK-4 1/8 and PSK-16 1/16 of
the baud rate. This behavior also includes multiples of the fractions.
OQPSK
The current version of the classifier has difficulties in correctly evaluating the baud rate of OQPSK signals,
e.g., Inmarsat-Aero. Additionally, the phase constellation diagram may be incorrect.
Handling of Synchronous and Asynchronous Speeds
The handling of asynchronous Baudot signals with 1.5 stop bits is a challenge. If the classifier does not
succeed in recognizing the stop bits, it will classify the signal as a synchronous signal having the double
speed of the actual signal.
CW Recognition
The classifier may confuse a low rate FSK signal with a fast CW signal, particularly at the edges of the
classification bandwidth. To lower the probability of such behavior, a classification model may be selected
which only allows CW signals below 30 Bd to be classified at the edges of the classification bandwidth.
Technical Data of the Narrowband and Wideband Classifier
The technical data of the narrowband and wideband classifier are summarized in the following tables.
Bandwidth HF 4 kHz or 8 kHz (IQ signal: 9.6 kHz)
Sampling interval (Ts) 1.6 sec or 3.2 sec
FSK 30 to 3000 Bd, Shift <= 3500 Hz, Modulation index: 0.5 – 20
Signal must be continuously present during the sampling interval
FSK-4 (F7B) 30 to 300 Bd, Shift <= 3500 Hz
MFSK 4-36 tones
PSK 2/4 Variant A/B 30 to 3000 Bd
PSK 8/16 Variant A/B 30 to 3000 Bd
MIL/STANAG Classified to protocol
CIS-12 120 Bd, classified as one signal
OFDM 25-512 carriers
Tg/Tu = 1/1 to 1/8
>= 25 Bd
OQPSK 25 Bd to 30 kBd
CW-Morse Ts = 1.6 s: 6 to 60 Bd
Ts = 3.2 s: 3 to 60 Bd
Voice No
Operation FFT display of classified signals
Continuous and single-pass mode