SDM-2020 Satellite Demodulator
Data Interfaces
Rev.3
A–67
A.8.3 Interface
Specifications
A 75
Ω
coaxial cable (Belden 8281 or equivalent) is recommended for all ASI connectors.
Typical Coaxial cable length is up to 140 meters (460 feet) with good quality coaxial
cable. Typical attenuation of up to 18dB at 270 MHz is permitted.The following cables,
or an equivalent computer grade cable incorporating twisted, shielded pairs, are
recommended for the LVDS interface:
•
Belden type LV Computer M9768
•
Belden 8175
The Belden 8175 has a lower capacitance, however, it has a larger diameter and requires
theselection of an appropriate connector shell. The typical cable length for the
serial/parallel interfaces is
≤
5 meters (16.405 feet).
Table A-38 describes the interface specifications.
Table A-38. ASI/LVDS Specifications
General Specifications
Data Framing Formats
188, 204 byte packets per ETS 300 421, and None.
Hot Pluggable
Not required. Unit power is turned off before removal or insertion of the
data interface.
ASI Specifications
Data Rate
1.5 to 100 Mbit/s ASI.
Clock Rate Uncertainty
Programmed data rate
±
100 ppm.
Transport Clock ASI
The transport rate is 270 Mbit/s for all data rates.
Impedance
75
Ω
.
Return Loss
15 dB, frequencies, 5 to 270 MHz.
Loop Functions
(see text)
Loopback
Loop Thru
Connectors
BNC female, 75
Ω
.
Electrical Properties
Per EN 80053-9.
Packet Types
Burst or distributed.
Signal Types
Serial data.
Voltage Level
800 mV ± 10% into 75
Ω
.
ASI Data Loop 3 dB
Frequency, TX Only
Wide: 2 Hz
Narrow: 0.3 Hz
Jitter Tolerance
Meets ITU-T G.823 (3/93) and ITU-T G.824 (3/93)
Jitter Transfer
≤
0.5 dB peaking up to cutoff frequency.
–20 dB per decade beyond cutoff.
Cable Length, Typical
100 meters (328 feet), RG59
140 meters (459 feet), Belden 8281
Delay Variation Of
Interface And Modulator
8 bits maximum, QPSK, and 8PSK only.
8PSK 2/3 and 5/6 all data rates. 8PSK 8/9 less than 80 Mbit/s.
Содержание SDM-2020
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