Wavecom W-SPECTRA (Automatic Monitoring System) V1.1.0 - Manual (Page 59)

WAVECOM Monitoring System W-SPECTRA, W-SPEED Manual V1.1.0 Parameters and Options
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symbol duration the quadrature part is switched. The advantage of this process is a smaller amplitude var-
iation.
OQPSK is used almost exclusively for satellite data links.
QPSK
Carrier recovery is mandatory to demodulate QPSK. As QPSK has phase shifts at ±90 and ±180 degrees,
the signal must be squared two times to produce a carrier at four times the original frequency. A PLL re-
covers the carrier in frequency and phase with ambiguities at ±90 and ±180 degrees. A complex mixer
down converts the signal to base band, and the resulting signal is the data signal.
QPSK is almost exclusively used for satellite data links.
SUBTONE
The same as DSP, but the parameters are optimized for low frequencies.
Passband Center
Set a value in the passband-center to adjust the center frequency of the passband filter.
For more details see “ Passband Filter Support ” on page 52.
Passband Bandwidth
Set a value in the passband-bandwidth to adjust the bandwidth of the passband filter.
For more details see “ Passband Filter Support ” on page 52.
Center
Set a value in the center to adjust the demodulator center frequency within 1 Hz accuracy. For modes
utilizing direct FSK this button is not available: in this case the offset frequency is equal to the effective
center frequency.
Shift
Set a value in the shift to adjust the frequency shift in 1Hz steps. In HF modes the range is 50 Hz – 3500
Hz, and in VHF-UHF modes using direct FSK the range is 50 Hz – 16000 Hz.
Baudrate
Set a value in the baudrate.
Polarity
Set the polarity to toggle “normal” or “inverse”. Usually when the signal is from the USB (upper side
band) the polarity should be set to “normal” and vice versa.