Section 3 - Theory Of Operation; Dmd20 Hardware; Dmd20 L-Band/If Printed Circuit Card - Radyne DMD20 Installation And Operation Manual

DMD20/DMD20 LBST Universal Satellite Modem Theory of Operation
Theory of Operation
3

3.0 DMD20 Hardware

The DMD20 is based on a two printed circuit card (minimum configuration) design with additional
optioned printed circuit cards available for additional features. The minimum configuration
consists of an L-Band/IF Assembly and a Digital Baseband Assembly. The optional printed circuit
cards include a Turbo Codec printed circuit card and one of several types of Interface printed
circuit card (refer to Appendix A). A block diagram of the DMD20 is shown in Figure 3.1.
Figure 3-1. DMD20 Block Diagram

3.0.1 DMD20 L-Band/IF Printed Circuit Card

The L-Band/IF Printed Circuit Card consists of an analog modulation function, an analog complex
downconversion, and two wide-band digital synthesizers. The block diagram of the L-Band/IF
Assembly is shown in Figure 3-2.
In the modulator, analog in-phase (I) and quadrature (Q) signals are generated on the Digital
Baseband Printed Circuit Card, routed to the L-Band/IF Printed Circuit Card, and modulated at
the desired frequency. The L-Band or 70/140 modulated signal is then passed through a
microprocessor controlled variable attenuator providing gain control of the output signal.
TM103 – Rev. 2.5 3-1