Comtech-ef-data SDM-2020 Manual do Utilizador descarregar pdf (Página 55)

SDM-2020 Satellite Demodulator Revision 4

Specification MN/SDM2020D.IOM

5–3

5.1.1 L-Band and 70/140 MHz Input Demodulator Charactistics

Table 5-2. L-Band and 70/140 MHz Input Demodulator Characteristics

Demodulator Specification

Parameter Single L-Band Input

(Older L-Band)

4 L-Band Inputs

(Newer L-Band)

Signal 70/140 MHz

Input (Optional)

RX IF Input 950 to 1750 MHz

in 2.5 kHz steps

950 to 1750 MHz

in 2.5 kHz steps

50 to 90 MHz and

100 to 180 MHz

in 2.5 kHz steps

Number of IF Inputs:

Standard

FAST Option

1 Physical Connector

4 Physical Connector

1 RF input connector

2 RF inputs enabled

4 RF inputs enabled

1 Physical Connector

Isolation, Unused Input to Tuner NA 50 dB minimum NA

Isolation, Between any Input NA 50 dB minimum NA

RX IF Impedance

75Ω 75Ω 75Ω (50Ω Optional)

RX IF Return Loss (minimum) 10 dB 10 dB 18 dB

RX IF Connector Type F, Female Type F, Female BNC, Female

Minimum Input, Desired Carrier C.

(See Figure 5-1 and 5-2)

C = –71 + 10 log

(Msym/s) dBm

C = –65 + 10 log (Msym/s)

dBm

C = –57 + 10 log

(Msym/s) dBm

Input AGC Range, minimum 40 dB 40 dB 30 dB

Input Level, Composite –5 dBm maximum, additive white Gaussian noise (AWGN)

Composite/Desired Carrier Ratio

≤ 17 +10 log [37.5/(Msym/s)]

LNB Power Supply Output

(Through Selected Input Only)

Selection 1

Selection 2

Selection 3

500 mA maximum, short circuit protected through

Type F connector feed:

20 to 24 VDC

12 to14 VDC, V-polarization per DiSEqC 4.2

16 to 20 VDC, H-polarization per DiSEqC 4.2

RX Buffer None (Note: Some Data Interfaces contain a buffer.)

Acquisition Sweep Range/Increment

0 to ± 500 kHz/1Hz 0 to ± 60 kHz

Acquisition Time

≤ 5 seconds, typical at ± 50 kHz uncertainty

BER Performance See Tables.

Adjacent Carrier Performance QPSK and 8-PSK: Performance degradation will not be more than 0.5 dB in the

presence of two-like modulated carriers each spaced 1.3 x symbol rate on either side

of the desired carrier and each adjacent carrier 10 dB greater in power than the

desired carrier .

16-QAM: Performance degradation will not be more than 0.5 dB in the presence of

two-like modulated carriers each spaced 1.3 x symbol rate on either side of the

desired carrier and each adjacent carrier 10 dB greater in power than the desired

carrier for symbol rates < 10 Msys/s and 7 dB, each carrier for symbol rates over 10

Msym/s.

Spectral Inversion Automatic, detection with ambiguity resolution

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