Comtech EF Data SNM-1010L - Manual (Page 168)

SNM-1010L Data/Control Modem Revision 0
Theory of Operation MN/SNM1010L.OM
6.3 Modulator
The modem modulator performs filtered modulation onto a variable frequency/amplitude
carrier in the following modulation:
• Binary Phase Shift Keying (BPSK)
• Quadrature Phase Shift Keying (QPSK)
• Offset Quadrature Phase Shift Keying (OQPSK)
• Eight Phase Shift Keying
(8PSK)
The modulator also provides the following functions:
• Encodes data for the appropriate decoder
• Scrambles data
• Monitors and displays the modulator status without interrupting service
• Provides source control timing
• Appends a burst preamble for detection by the demodulator (burst mode)
• The modem creates a modulated carrier within the 950 to 1750 MHz range from
the digital data stream provided by the interface section.
Control mode
The following modulation type is available when the modem
is operating in the burst-transmit/continuous-receive control
mode.
• QPSK
Data mode The following modulation types are available when the modem
is operating in the continuous data mode.
• 8PSK
• BPSK
• QPSK
• OQPSK
The following subsections make up the modulator:
• Scrambler
• Convolutional encoder
• Preamble and postamble generator (burst mode only)
• Modulator
• Output amplifier
• RF synthesizer
• SCT synthesizer
6–6