Comtech EF Data DMD-2050E - Manual (Page 44)

DMD2050E Universal Satellite Modem Theory of Operation
MN-DMD2050E Revision 2 3–2
3.1.1 DMD2050E 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.
Figure 3-2. IF Card Block Diagram
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.
In the complex downconverter, the signal for demodulation is amplified and sent through a
variable wideband attenuator for AGC. The gain-controlled signal is then passed through a
complex downconverter to a low IF.