Comtech EF Data SDM-2020 - Manual (Page 193)

SDM-2020 Satellite Demodulator Revision 4
ASI/LVDS Data Interface MN/SDM2020D.IOM
13–3
13.1.3 Interface Specifications
A 75 Ω coaxial cable (Belden 8281 or equivalent) is recommended for all ASI connectors.
Typical Coaxial cable length is up to 70 meters (230 feet) with good quality coaxial
cable. Typical attenuation of up to 8dB 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
the selection of an appropriate connector shell. The typical cable length for the
serial/parallel interfaces is
≤ 5 meters (16.405 feet).
Table 13-1 describes the interface specifications.
Table 13-1. 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 Mbps ASI.
Clock Rate Uncertainty Programmed data rate ± 100 ppm.
Transport Clock ASI The transport rate is 270 Mbps 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 50 meters (328 feet), RG59
70 meters (459 feet), Belden 8281
Delay Variation Of
Interface And Modulator 8 bits maximum, QPSK, and 8-PSK only.
8-PSK 2/3 and 5/6 all data rates. 8-PSK 8/9 less than 80 Mbps.