Demodulator; Description; Specifications - Comtech EF Data SDM-9000 Installation And Operation Manual

SDM-9000 Satellite Modem

5.3 Demodulator

5.3.1 Description

The demodulator PCB fits in the bottom slot of the modem chassis. The demodulator
converts PSK and QAM modulated carriers within the 50 to 180 MHz range to a
demodulated baseband data stream. The demodulator then performs FEC on the data
stream, using the Viterbi decoding algorithm.
The converted modulation types are:
•
•
•
Refer to Section 5.6 for a description of the modulation types. Figure 3-3 shows the
demodulator PCB. A block diagram of the demodulator is shown in Figure 5-4, and all
demodulator jumper settings are listed in Table 3-3.

5.3.2 Specifications

Modulation Types
Data Rate Range
Symbol Rate Range
IF Frequency
Input Power (Desired Carrier)
Input Impedance
Input Return Loss
Forward Error Correction
Carrier Acquisition Range
Filtering Type
Rev.4
QPSK
8PSK (optional)
16QAM (optional)
QPSK
8PSK (optional)
16QAM (optional)
6.0 to 52.0 Mbit/s (four data rate plug-on module)
1.7 to 37.6 Ms/s
50 to 180 MHz, in 2.5 kHz steps
-45 to -25 dBm
Ω Ω
75 (50 optional)
> 18 dBm
Viterbi k=7
±
60 kHz
Nyquist
Theory of Operation
5–11