Comtech EF Data SDM-100A - Manual (Page 117)

Rev. 0 4–1
Chapter 4.
THEORY OF OPERATION
This chapter describes the theory of operation for the various components of the modem.
4.1 Modulator
The modem modulator creates a QPSK or BPSK modulated carrier within the 50 to
180 MHz range from the digital data stream that is provided by the Interface section.
The following subsections make up the modulator:
• Scrambler/differential encoder
• Convolutional encoder
• I&Q Nyquist filters
• Modulator
• Output amplifier
• RF synthesizer
A block diagram of the modulator is shown in Figure 4-1.
4.1.1 Theory of Operation
The modulator is composed of several basic subsections, which comprise the baseband
processing and RF sections. The modulator M&C controls all programmable functions on
this module.