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

DMD1050TS Satellite Modem Board
Revision 1
Theory of Operation 3–2 MN-DMD1050TS
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.
Figure 3-2. L-Band Assembly
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.
Quadrature
Demodulator
IF Board Connector (40-Pin Header)
Demodulator I
Demodulator I Inv.
Demodulator Q
Demodulator Q Inv.
AGC
L-Band
Synthesizer
PDA
Analog Q Inv.
Analog I Inv.
L-Band
Synthesizer
Quadrature
Modulator
Analog Q
Analog I
LPF
LPF
Switch
RxLB
TxLB
Coupler
DCSA