L-Band Printed Circuit Card; Figure 3-2. L-Band Assembly - Comtech EF Data DMD1050TS Installation And Operation Manual

3.1.1 L-Band Printed Circuit Card

The L-Band/IF Printed Circuit Card consists of:
•
Analog modulation function
•
Analog complex down conversion
•
Two wide-band digital synthesizers
The block diagram of the L-Band Assembly is shown in Figure 3-2.
TxLB
RxLB
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 Printed Circuit Card and modulated at the
desired frequency.
The L-Band modulated signal is then passed through a microprocessor-controlled variable
attenuator, providing gain control of the output signal.
In the complex down converter, the signal for demodulation is amplified and sent through a
variable wideband attenuator for Automatic Gain Control (AGC). The gain-controlled signal is
then passed through a complex down converter to a low IF.
Theory of Operation
PDA
DCSA
Switch

Figure 3-2. L-Band Assembly

3–2
DMD1050TS Satellite Modem Board
LPF
Quadrature
Modulator
Analog Q
LPF
Analog Q Inv.
L-Band
Synthesizer
L-Band
Synthesizer
Demodulator I
Demodulator I Inv.
Quadrature
Demodulator Q
Demodulator
Demodulator Q Inv.
AGC
Revision 1
Analog I
Analog I Inv.
MN-DMD1050TS